Emerging Technologies in the Dairy Industry

Chapter 4

Emerging Technologiesin the Dairy Industry

ContentsPage

BIOTECHNOLOGY AND THE DAIRY INDUSTRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Reproductive Technologies and Transgenic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Animal Health Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Food Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

KNOWLEDGE-BASED INFORMATION SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Expert Systems and Other Computer-Based Decision Aids.... . . . . . . . . . . . . . . . . . . . . 66Application of New Information Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

CONCLUSIONS .. .. . .. .. .. ... ... ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....67CHAPTER PREFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Box4-A. Definitions

Figure

of Commonly

BoxPage

Used Terms . . . . . . . . . . . . . . . . . . . . .. . . . ....... . . . . . . 52

FiguresPage

4-1. Reproductive Technologies Used To Produce Transgenic Animals . . . . . . . . . . . . . . . 544-2. Identification and Isolation of Desired Gene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554-3. Process of Producing a Transgenic Mouse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574-4. Gene Transfer Using Embryo Stem Cell Culture . . . . . . . . . . . . . . . . . . . . . . . . . .4-5. Nuclear Transplantation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6. Preparation of Monoclinal Antibodies . . . . . . . . . . . . . . . . . . . . + . . . . . . . . . . . . . . .

TablesTable4-1. Predicted and Actual Sex Ratios of Offspring After Intrauterine Insemination

of Sorted X and Y Chromosome-Bearing Rabbit Sperm... . . . . . . . . . . . . . . . . .4-2.Monoclinal Antibodies for Diagnostic Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

, . . . . . 5 8... ...60... ...64

Page

. . . . . . 62

. . . . . . 65

Chapter 4

Emerging Technologies in the Dairy Industry

Bovine somatotropin (bST) is the first majorbiotechnology product developed for the dairyindustry. This product has been controversial andhas raised many scientific and socioeconomic ques-tions. BST, however, is not the only new technologythat will affect the dairy industry. Advances inanimal reproduction, animal health, and food proc-essing are occurring, and many of the new technolo-gies being developed use highly sophisticated andcomplex biotechnology methods. By comparison,the biotechnology methods used to produce bST areactually rather rudimentary; potentially some ofthese new technologies could make bST obsolete.These new technologies will increase the level ofmanagement skills needed to use them effectively;new information technologies will aid the decision-making process. Several conclusions can be drawnconcerning the development of these new technolo-gies:

The dairy industry is on the verge of atechnological revolution. Biotechnology meth-ods that are more advanced than those used toproduce bST are currently under development.The impact of these technologies, in conjunc-tion with new information technologies in thenot too distant future may rival that of bST.Assessment and analysis, similar to that of bSTmay be warranted for many of these technolo-gies.The field of animal reproduction is advancingrapidly. Researchers ‘have significantly im-proved their understanding of egg developmentin the ovary, how to stimulate the release ofnumerous eggs at once, and how to achievefertilization and development of eggs outsideof the cow. Embryos can be frozen for later use.Both embryos and sperm can be sexed. It is alsopossible to create multiple copies of an embryo,each of which can be transplanted into a cowwhose reproductive cycle has been adjusted tobe able to accept the embryo and carry it toterm. These new technologies make it possibleto improve herd quality more rapidly than canbe achieved using traditional breeding meth-ods.

●

●

●

●

●

[t is now possible to create transgenicl cattle,however, the techniques currently used areinefficient and require the use of thousands ofeggs to produce just one transgenic animal.These inefficiencies make it too expensive tocommercially produce and market transgeniclivestock. However, scientific breakthroughsare leading to the development of technologiesthat will improve the efficiency of transgenicanimal production and substantially lower thecost of doing so. Transgenic livestock maybecome commercially available in small num-bers by the end of the decade.BST potentially could be supplanted by thedevelopment of transgenic cattle. Dairy cowscan be developed to produce higher levels ofbST so that daily injections or timed releaseformulations are no longer needed. Alterna-tively, genes that code for chemicals thatsuppress bST production can be altered in thecow such that a cow’s normal bST productionwill increase.New biotechnology products are also beingdeveloped to improve animal health. Productsinclude new vaccines and diagnostic kits, aswell as compounds that enhance an animal’sability to fight disease.Not only are new biotechnology products beingdeveloped for use in livestock production, butthey are also being developed for use in foodprocessing. New products will improve theproduction of milk products such as cheese andyogurt. They can also be used to detect milkcontaminants.Effective use of these new technologies willplace a premium on management skill. Newinformation technologies are being developedto aid farm management. These new technolo-gies can incorporate individual farm data, withpertinent information from national databases,into computer programs that will aid farmers inthe decisionmaking process.

This chapter describes information systems, andbiotechnology methods and products that have beendeveloped, or are expected to be developed for use

lm~5 whose heredi~ DNA has been augmented by the addition of DNA from a source other than parental germplasm uStig recombmt DNAtechniques.

-51–

52 ● U.S. Dairy Industry at a Crossroad: Biotechnology and Policy Choices

in the dairy industry in the decade of the 1990s.Many of these technologies are highly sophisticated,cutting-edge technologies, and as such have not beenextensively discussed in the lay literature. However,it is important that the potential of these technolo-gies be understood. Given the nature of these newtechnologies, the following descriptions are, bynecessity, somewhat technical.

BIOTECHNOLOGY AND THEDAIRY INDUSTRY

The term biotechnology refers to a wide array oftechniques that use “living organisms (or parts oforganisms) to make or modify products, to improveplants or animals, or to develop microorganisms forspecific uses’ (46). Under this broad definition,biotechnology includes many long-practiced dairy

technologies such as animal breeding and cheese-making. New biotechnologies include recombinantDNA techniques, cell culture, and monoclinalantibody (hybridoma) methods (see box 4-A). Theapplication of these new methods to the dairyindustry has already generated a number of productsfor improving milk production, animal health, andfood processing, and will continue to do so. Productsnow emerging range from rapid diagnostic tests for

contaminants in dairy products to cows geneticallyengineered to produce high-value pharmaceuticals.

Reproductive Technologies andTransgenic Animals

Animal scientists generally agree that the mostimportant cause of economic loss in the animalindustries results from reproductive inefficiency

Box 4-A—Definitions of Commonly Used Terms

Antibody: Proteins produced by specific white blood cells (i.e., B lymphocytes) that bind specifically toforeign antigens in the body.

Antigen: Any substance that elicits a defensive (immune) response.Cell culture: The growth and maintenance of cells derived from multicellular organisms under controlled

laboratory conditions.Chromosome: A thread-like structure composed primarily of DNA, that carries the genes which convey

hereditary characteristics; in mammals chromosomes are contained in the nucleus and the X chromosome conveysfemale characteristics and the Y chromosome the male characteristics.

DNA (deoxyribonucleic acid): The molecule that is the repository of genetic information in all organisms(with the exception of a small number of viruses in which the hereditary material is ribonucleic acid-RNA).

Estrus: The period during which a female mammal is receptive to sexual activity.Estrous cycle: The period of time needed for the reproductive cycle that includes egg maturation and ovulation

in the ovary and preparation of the uterus to receive fertilized eggs. This cycle is under hormonal control and extendsfrom the beginning of one period of estrus to the beginning of the next.

Hybridoma: A new cell resulting from the fusion of a particular type of immortal tumor cell line, a myeloma,with an antibody-producing B lymphocyte. Cultures of such cells are capable of continuous growth and specificantibody production

In vivo: Within the living organism.In vitro: Outside the living organism and in an artificial environment, e.g., test tube.Monoclinal antibodies: Identical antibodies that recognize a single, specific antigen and are produced by a

clone of specialized cells.Recombinant DNA: A broad range of techniques involving the manipulation of the genetic material of

organisms; term is often used synonymously with genetic engineering; term also used to describe a DNA moleculeconstructed by genetic engineering techniques composed of DNA from different individuals or species.

Transgenic animals: Animals whose hereditary DNA has been augmented by the addition of DNA from asource other than parental gerrnplasm using recombinant DNA techniques.

Uteri: The plural for uterus— the organ of the female mammal for containing and nourishing the young duringdevelopment prior to birth.SOURCE: Office of Technology Assessment, 1991.

Chapter 4--Emerging Technologies in the Dairy Industry ● 53—

(i.e., low conception rates and embryo mortality).The field of animal reproduction is currently under-going a scientific revolution. In the 1986 reportTechnology, Public Policy, and the Changing Struc-ture of American Agriculture, OTA predicted that,beginning about the year 2000, eggs matured andfertilized in vitro and transplanted to a recipientanimal (artificial inembryonation) would in part,replace natural and artificial insemination in theanimal breeding system, and embryos altered byrecombinant DNA techniques (transgenics) wouldbe commercially available. In fact, embryos pro-duced by new reproductive methods are currentlybeing marketed, although at present no transgenicembryos are commercially available. However, sig-nificant new advances are occurring, and the direc-tion and timetable of developments will almostcertainly be affected. This section focuses on recentadvances in reproduction and recombinant DNAtechniques and their application to the dairy industryduring the decade of the 1990s.

It is now possible to select genetically superiorfemales and induce them to shed large numbers ofeggs (superovulation) that can be matured in vitroand fertilized with sperm from males selected fortheir desirable traits. The resulting embryos can besexed, split to make duplicate copies, and storedfrozen until needed. An embryo can then be trans-ferred by nonsurgical techniques into the uterus of arecipient animal whose estrous cycle has beensynchronized with the stage of development of theembryo. These new reproductive technologies can,and are being used to improve the quality oflivestock herds more rapidly than could be achievedwith traditional breeding, although currently manyof these technologies are still relatively inefficient.

The ultimate goal of many workers in the field ofanimal biotechnology, however, is to produce ani-mals whose hereditary DNA has been augmented bythe addition of DNA from a source other thanparental germplasm, using recombinant DNA tech-niques (transgenic animals) (47). Transgenic ani-mals can be created that possess traits of economicimportance including improved disease resistance,growth, lactation, or reproduction.

Transgenic livestock may also prove to be effec-tive factories for the production of high-valuepharmaceuticals, a development particularly perti-nent for the dairy industry (9). Genes that code foranimal proteins (e.g., tissue plasminogen activator-

TPA) can be linked to regulatory sequences thatdirect high levels of gene expression in the mam-mary gland. This enhanced expression results inincreased secretion of the desired animal protein intothe milk of lactating females. This protein could thenbe extracted and purified from the milk. Transgeniccows producing pharmaceuticals have not yet beenreported, but these animals are under development ina number of public and private laboratories. Highlevels of milk production coupled with the ease ofmilk collection may make this production methodmore cost effective than the cell culture systemscurrently used in the production of certain pharma-ceutical proteins.

The production of transgenic animals is inextrica-bly linked to development of new reproductivetechnologies. It is impossible to produce animalscontaining foreign DNA in their germlines withoutfirst manipulating the embryo and transferring it toa recipient animal. New reproductive technologies .such as superovulation, in vitro egg maturation andfertilization, nuclear transplantation, and embryosexing can be used to upgrade livestock herds.However, when they are combined with recombi-nant DNA technologies (the identification, isolation,and transfer of selected genes), they provide oppor-tunities to efficiently and cost effectively producetransgenic animals, and to rapidly improve livestockquality (see figure 4-l). Therefore, advances inreproductive technologies will be discussed withinthe context of their applicability to the production oftransgenic animals, recognizing that they are in theirown right powerful tools for livestock improve-ments.

Steps in the Development of Transgenic Animals

The production of transgenic animals is a com-plex process, and involves four major steps. First,the desired gene must be identified, isolated, andprepared for insertion into a fertilized egg. Second,the host cell must be obtained and prepared for geneinsertion. In livestock, the host cells used aregenerally fertilized eggs or early stage embryos.Third, the desired gene must be transferred to thehost cell. And fourth, the resulting recombinantembryo is duplicated, and the resulting multipleembryos are transplanted into recipient cows thathave had their estrous cycles synchronized to receivethe embryo. This duplication process allows for theproduction of multiple offspring of geneticallysuperior animals. Advances in each stage, discussed

Figure 4-1—Reproductive Technologies Used To Produce Transgenic Animals

kIdenttflcatlon and Isolatlon

r I

E\ .+;~’’’’’’’nisrandom”superovulation combined with

eggI

Host cell preparation using1

superovulation combined within vitro egg maturation andfertilization 1

I I 12 to 4 + 2 to 4embryos Embryo cell embryos

L J multiplicationI J

by splitting

1

Embryo multiplication bynuclear transplantationand recloning

Egg cell with nucleus removedEarly stage embryo(less than 64 cells) -

Gene transfer

I Implantation into cowwhose estrous cycle has~ m

~ been synchronized to JY receive the embryo

E + I i s t a r g e t e d”by gene identificationand isolation.

SOURCE: Office of Technology Assessment, adapted from J.P. Simons and R.B. Land, “Transgenic Livestock,” J. Reprod Fert. Supp/. 34:237-250, 1987.

I

Chapter 4--Emerging Technologies in the Dairy Industry .55

below, are improving the efficiency of transgenicanimal production.

Step 1: Gene Identification and Isolation--Be-fore a foreign gene can be transferred into thegenome of a host cell to create a transgenicorganism, the gene must first be identified andpurified. This is done by a process called cloning.The tools used to clone DNA include specialenzymes that cut and paste DNA, nucleic acidfragments that can be used to identify specific DNAsequences (probes), vehicles used to carry a foreigngene into a host cell (vectors), and host cells that canbe used to produce multiple copies of the gene. Thehost cells used to multiply gene numbers are usuallybacteria. The vectors most commonly used arebacterial plasmids, circular pieces of DNA that areeasily inserted into bacterial cells and are capable ofindependent replication inside the bacteria (seefigure 4-2).

Isolating a single gene is complicated by the factthat a DNA sample may contain millions of genes.Researchers must be able to separate the one gene ofinterest from all of the other genes. To do this, theDNA sample containing the desired gene is cut intopieces with special enzymes (restriction endonu-cleases). The bacterial plasmid (vector) is also cutwith the same enzyme. The pieces of sample DNA,including any pieces carrying the desired gene, areinserted into vectors and the loose ends of the sampleDNA and bacterial plasmid are pasted together(using the enzyme DNA ligase). These recombinantDNA vectors are then inserted into bacterial cells,and the bacterial cells are grown. At this point thebacterial cells containing the plasmid carrying thedesired gene must be identified and isolated from therest. This is done by using a probe, a nucleic acidsequence that recognizes the desired gene. Once thebacterial cells containing the desired gene are found,those cells can be grown in isolation to producemillions of copies of the vector containing thedesired gene. The vector can be removed from thebacterial cells, and the desired gene isolated. Thisprocedure can yield millions of copies of the desiredgene that are free from contamination by other genes(48).

The purified gene can then be combined withappropriate regulatory genes that control the circum-stances under which the gene is turned on and off.The purified gene and its regulatory sequences canbe inserted into a vector such as a virus, for example,

Figure 4-2—identification and Isolationof Desired Gene

DNA containing gene to be isolated

1 Use restriction enzymesto cut the vector and to

icut the DNA containing

.$: the desired gene into~ pieces I I

f9,

\ - .

F %8, $

\ /’%

- - m ’ c7~; {k/’ ‘$ &,..1

,,&f@

%, Joining of Vector

\ /DNA Fragments With

$“ DNA Fragments to beq, c’ Cloned Using the% k’-%.?$:2:.... .;” Enzyme DNA Ligase‘ “ ’ $7”

Recombinant DNA Molecules

Introduction ~into Bacteria tj;~.,;

tiim Vector with

( 2Cloned DNA

Bacterial FragmentChromosome

@3

j ,

@@’@@DesiredMultiplication of Bacteria Containing the

Gene To Yield Many Identical Copies of Fragments

SOURCE: Office of Technology Assessment, 1989.


that will carry these genes into an animal cell andincorporate them into the genome (see gene transfertechnologies). The tools used to purify genes arewell developed. The major challenge is determiningwhich genes are to be purified.

Step 2: Preparation of the Host Cell—Becausecurrent technologies used to transfer a gene into ahost cell are inefficient, to get just one transgenicanimal requires the use of thousands of fertilizedeggs. To attain such large numbers of embryos, cowsmust be induced to shed large numbers of eggs(superovulation) that can be matured and fertilizedin vitro. Increased understanding of the control ofovarian functions is improving the efficiency ofobtainin g sufficient numbers of fertilized eggs.

Control of Ovarian Functions-The lack ofhighly repeatable, efficient means for inducingsuperovulation is a major constraint. Induction ofsuperovulation requires detailed knowledge of thehormonal factors that control the development of theegg in the ovary. The process of egg developmenthas been subjected to intense investigation and anumber of significant advances have been madeduring the past 5 years. Studies that have exploredthe basic mechanisms controlling egg growth andmaturation, and corpus luteum2 function, havepaved the way for developing even more precisemethods for regulating the estrous cycle, producingsuperovulation, and reducing the heavy losses due toearly embryo deaths.

Perhaps the most important development in ovar-ian physiology in recent years is the discovery of theovarian hormone inhibin, which decreases the ovu-lation rate.3 Some breeds of animals with excep-tionally high ovulation rates, such as the Booroolastrain of Merino sheep in Australia, are known tohave low levels of circulating inhibin (4). Cattleimmunized against inhibin have lower circulatinglevels in their blood and show increased ovulationrates (21). The genes controlling inhibin productionhave been cloned and the potential exists forproducing transgenic animals in which these genesare repressed or deleted.

Progress has also been made in understanding thecontrol mechanisms that regulate corpus luteumfunction and its production of progesterone, ahormone that regulates the length of the estrous

cycle and helps maintain pregnancy. This under-standing paves the way for development of moreprecise methods for regulating the estrous cycle,which is needed to synchronize surrogate mothers,and for producing superovulation. Superovulationtreatments are initiated when the ovaries are underthe influence of progesterone. Currently, super-ovulation treatments use highly purified hormonesproduced by recombinant DNA technology andproduce, on average, about 10 viable eggs pertreatment (compared to the 1 egg a cow normallyproduces per ovulation) (21). As the new knowledgeof the factors controlling egg development andcorpus luteum function is applied, the number ofviable embryos produced by each superovulationtreatment is expected to increase.

In Vitro Maturation and Fertilization of Eggs—Invitro maturation and fertilization of eggs recoveredby superovulation provides a means of overcomingthe problem of livestock reproductive inefficiency.Normally, a bovine ovary contains about 50,000immature eggs at puberty, however, on average only3 to 4 of these eggs will result in the births of livecalves during the animal’s lifetime. Using presentsuperovulation methods, about 10 viable eggs can beharvested from the ovaries of 1 treated cow andabout half of these develop into embryos suitable fortransfer. Improved superovulation technology maylead to the recovery of more eggs suitable for in vitrofertilization such that the number of live birthsresulting from a superior animal could be quite high.

In vitro fertilization occurs only when a capaci-tated sperm (i.e., a sperm specially prepared topenetrate the egg cell membrane) encounters an eggat an optimal maturation state. Great progress hasbeen made in understanding the factors involved inegg maturation and sperm capacitation in livestock.As a result, offspring have been produced in cattle,swine, sheep, and goats following in vitro fertiliza-tion (16) and attempts to market embryos producedwith these techniques are already underway.

Step 3: Gene Transfer Technologies—Achiev-ing the goal of transgenic animal production requiresthe development of efficient and cost effective waysto transfer the selected genes to an embryo. Micewere the first transgenic mammals created (seefigure 4-3), and were produced by microinjecting

z~e CO~u.S lute~ is a temp~~ endocrine organ that is produced at the site of ovulation dtig each W@Ous cYcle.

%hibin decreases owlation rates by suppressing the secretion of follicle stimulating hormone (FSH), a hormone produced by tie Pitiw gl~d.

Chapter 4--Emerging Technologies in the Dairy Industry ● 57

Figure 4-3-Process of Producing aTransgenic Mouse

Y Implant injected embryosinto pseudopregnant

Q

4’Fetal Developmental regulationexpression / . Live birth

\test for transgene

eFounder animal

1 Breed transgenics

6 3A & ~ 2Fetal/neonatal pup

Adult

SOURCE: Sally A. Camper, Fox Chase Cancer Center.

cloned DNA into a fertilized egg4 (32). Alterna-tively, viral vectors can be used to transfer clonedDNA into a host embryo (14). The embryo is thentransferred to a recipient animal whose estrous cyclehas been synchronized to accept and carry to term,the developing embryo.

A number of transgenic cattle, pigs, sheep, andchickens have been produced by these techniques,however, they are of limited use because of the highcost and low efficiency of microinjection tech-niques, and the absence of appropriate viral vectorsfor use in most livestock species. Additionally, DNAtransferred by these methods is inserted randomlyinto the host genome, resulting in a lack of controlof the gene transfer process (20).

Because of the deficiencies encountered withusing viral vectors or microinjection methods tocreate transgenic livestock, alternative methods arebeing sought. A promising new method for generat-ing transgenic animals has recently been developedin mice and may be applicable to other mammals.This new technique uses stem cells derived from anembryo. Stem cells are cells that are normallyundifferentiated, that is, they do not become special-ized tissue cells such as muscle, brain, liver cells,etc. However, stem cells retain their ability tobecome specialized cells when given the properstimuli (i.e., they are pluripotent).5 These stem cellscan be used as vectors to introduce selected genesinto a host embryo. This method has severalsignificant advantages over microinjection methods,the most profound of which is that for the first time,it is possible to insert DNA at specific, predeter-mined sites within the genome of the stem cells (8).Targeted insertion is possible because stem cellshave an intrinsic ability to recombine similar (ho-mologous) DNA sequences, which results in thereplacement of the endogenous gene with the desiredgene.

Stem cells must first be isolated (see figure 4-4).An early stage embryo is cultured on a thin layer ofspecially prepared cells. The proliferating embryocells are recultured until individual stems cells canbe isolated. These individual stem cells can then becultured indefinitely. At this stage, DNA sequencescontaining desired genes can be inserted into thestem cells.6 A genetically transformed stem cell isthen microinjected into an immature embryo toproduce a chimera, an organism that contains cellsfrom more than one source. If the stem cells areincorporated into the germ lines of these chimericanimals, then these animals can be interbred toobtain offspring that are homozygous for the desiredtrait (8).

Application of the gene targeting method makespossible a broad range of phenotypes for transgenicanimals that could not be produced economicallyusing direct microinjection or viral vectors. Targetedgene insertion allows endogenous genes to be

4SPcific~Iy, tie DNA is ~ject~ into tie male Pronucleus of the fertilized egg. The pronucleii are the egg ~d sPerm nucleii Present after tie ‘Pmpenetrates the egg membrane.

Splmipotency help me stem cells attractive vectors of DNA transfer. While in tissue culture, DNA Cm emily be tiefied ~to stem ce~s. menstem cells are injected into an early stage embryo, the conditiom for tissue specialization are present, and stern cdls undergo the normal tissuedevelopment that occurs as the embryo develops during pregnancy. Thus, using stem cells provides an efficient means to transfer DNA.

6Me~ods US~ inc]ude viral infmtion and use of an electric pulse to make cell membranes leaky (electropomtion).

58 ● U.S. DairyIndustry at a Crossroad: Biotechnology and Policy Choices

Figure 4-4—Gene Transfer Using Embryo Stem Cell Culturea

A-,: I - t-

- 1 -

–7 1-1--1 , :1- . , . . “ ;:I - -. ‘ +–,—, - .(

, . .

t

A mouse embryo (blastocyst)is donated.

The embryo is culturedonto a thin layer ofspecially prepared(feeder) cells.

The embryo attaches tothe cell layer, and theinner cells of the embryobegin to proliferate.

Groups of these differentiatingembryo cells are separated,recultured and single coloniesof embryonic stem cells areidentified and transferred.

Single cells are reseededonto the feeder cells. Foreign

K “ ’ ’ ’ O th e ~ <l < l

F r

#+-’-JTJ

A second mouse embryo is donatedand is injected with a culturedembryonic stem cell. This embryois transplanted into a surrogatemouse, which gives birth to achimera (a mouse with cells fromboth parent embryos). Mating twochimeras gives rise to offspringwith the desired traits.

. ----Y’.. .( - 3‘“* :

“

aThis technique is currently developed only for mice and hamsters and possibly rabbits and swine. It is not yet developed for cattle.

SOURCE: M.R. Capecchi, “The New Mouse Gene!ics: Altering the Genome by Gene Targeting,” Trends in Genetics 5:70-76, 1989.


inactivated or replaced with modified forms of thegene, such as one that is expressed at a higher level,has anew pattern of tissue specific expression, or hasa modified biological activity.

Perhaps the most significant advantage of thegene targeting approach is that it allows for en-dogenous genes to be effectively removed. Genescan be inactivated by targeting insertion into anessential region of the gene. This fact is of particularinterest to the livestock industry, because inactiva-tion of genes that have inhibitory physiologicaleffects is likely to result in improvement in a numberof productive traits. For example, bovine somato-statin is a hormone that inhibits bovine somatotropinproduction; inactivation of this gene would result inincreased endogenous somatotropin secretion and,presumably increased milk production and moreefficient growth. If successful, this technologywould supplant the need to administer bST ex-ogenously to increase milk production (see ch. 3).The genes controlling the production of inhibin, theovarian hormone that reduces ovulation rate, is yetanother example. The ability to inactivate genes alsoprovides a powerful research tool that allows scien-tists to study the function of genes in vivo. Theabsence of a method to produce embryo stem celllines from cattle is currently preventing the use ofthe gene targeting approach in the dairy industry,7

however, a number of laboratories are trying todevelop this technology.

Step 4: Embryo Multiplication-The productionof multiple copies of a genetically engineeredembryo is the final step in the development oftransgenic animals. Efficient and inexpensive multi-plication technologies are tremendously importantfor improving the efficient development of transgenicanimals. Multiple copies of a mammalian embryowere first produced by physically splitting an earlyembryo into halves, giving rise to identical twins(21). If the embryo is divided more than twice,however, few offspring survive. Thus, no more thanfour identical animals can be produced by splittingand generally only two embryos are produced by thismethod. This procedure is already used in the cattleembryo transfer industry, nearly doubling the num-ber of offspring produced.

A more efficient and promising method of produc-ing multiple copies of an embryo is by a technique

called nuclear transplantation. Basically, the proce-dure involves the transfer of a nucleus from a donorembryo into an immature egg cell whose ownnucleus has been removed. The recipient egg cell isactivated by exposure to an electric pulse, allowed todevelop into a multicelled embryo, and then used asa donor in subsequent nuclear transplantations togenerate multiple clones. This procedure (outlinedin figure 4-5) has been used successfully with cattle(7,35), sheep (42,49), and swine (36). Using thistechnique, hundreds of pregnancies have alreadybeen produced in cattle and recloning has beenperformed successfully resulting in as many as eightcalves from one embryo (28).

The value of this technique to the dairy industryis enhanced by the ability to successfully transfernuclei from frozen embryos into eggs whose nucleihave been removed. Conception rates obtained aftertransfer of embryos produced by nuclear transplan-tation are variable, but rates as high as 50 percenthave been obtained. However, embryo losses aftertransfer are higher than normal, resulting in actualpregnancy rates ranging from 15 to 33 percent (7).Combining the techniques of in vitro fertilization,embryo cloning, and artificial estrous cycle regula-tion will likely result in major changes in dairy cattlebreeding and in the rates of genetic improvement.

While significant advances in transgenic animalproduction have been made, it is unlikely thattransgenic animals will be commercially availablebefore the end of the 1990s at the earliest. The abilityto produce transgenic cattle possessing traits ofeconomic value is currently limited by the absenceof embryo stem cell technology and the lack ofknowledge about the relationship between the ex-pression of a specific gene and the physiologicalconsequences. While the techniques for isolatingand sequencing bovine genes are now straightfor-ward, understanding of the functions of the geneshas lagged. Analysis of gene function is complicatedby the fact that many traits are controlled by multiplegenes. Thus, manipulation of such traits will requiredetailed understanding of these genes and theirinteractions. Ultimately identifying and understand-ing the physiology of the major genes controllinglactation, reproduction, and disease and stress resis-tance in dairy cattle is needed. An active genomemapping program could help enhance these develop-ments.

7~e stem ce~ tec~o]on has been developed for mice, titers, ~d swine.

292-860 0 - 91 - 3


Figure 4-5—Nuclear Transplantation

— 1 — , — , — , —,

An embryo is nonsurgically removedfrom a donor cow or is produced byin vitro fertilization.

Individual embryoare removed.

cells

Each embryo cell is injected intoa specially prepared egg cell thathas had its nucleus removed. Anelectric pulse is administered tocause fusion.

Each egg cell is grown to amulticell embryo at which pointthe cloning procedure can be repeated

or

the embryo can be transplanted toa cow that eventually gives birth.

SOURCE: ~’fice of Technology Assessment, adapted from R.S. Prather and N.L. First, “Cloning Embryos by Nuclear Transfer,” Genetic Engineering ofAnima/s, W. Hansel and B.J. Weir (eds.), Journa/ of Reproduction and Ferti/ify~td, Cambridge, UK, 1990, pp. 125-134.

Chapter 4--Emerging Technologies in the Dairy Industry . 61

Sexing of the Offspring

The availability of a technique to preselect the sexof the progeny is of great economic potential for thedairy industry where females are the major incomeproducers and artificial insemination is alreadywidely used. Until recently, none of the methodsresulted in the degree of separation needed forcommercial use. However, recent advances in theseparation of the X and Y sperm, and sexing of theembryo have been made.

Separation of the X- and Y-Beating Sperm—Ithas long been a goal of mammalian p h y s i o l o g i s t s t odevelop a method for effectively separating X and Ychromosome-bearing sperm to control the sex of theoffspring. Most sperm separation techniques arebased on potential differences in the size and densityof the two sperm types. 8 These methods, however,have met with limited success (41).

Development of cell sorting techniques based onthe differences in sperm size and fluorescence ofsperm DNA (flow cytometric measurements) hasprovided the first effective method to sort the spermcells. Johnson et al. (24) recently reported successfulseparation of intact viable X and Y chromosome-bearing sperm using this method (see table 4-l).Although the difference in DNA contents of the Xand Y chromosome-bearing sperm in rabbits amountsto only about 3 percent, 94 percent of the rabbits(does) inseminated with X-bearing sorted spermproduced females and 81 percent of the doesinseminated with Y-bearing sorted sperm producedmales. Commercial use of this process is limited, atpresent, by the number of sperm that can be sortedper hour and by increased embryo mortality ob-served in the embryos produced after inseminationwith the sorted sperm. Neither of these factors isthought to represent an insurmountable difficulty.

Embryo Sexing—The most accurate method forsexing embryos is to create a picture of the number,size, and shape of the chromosomes contained in theembryonic cells (karyotyping). However, this methodrequires removal of about half of the cells ofearly-stage embryos, which decreases embryo via-bility and limits the number of embryos that can betransferred. Another method uses antibodies todetect proteins (antigens) unique to male embryos.

This method is not damaging to the embryos andencouraging results have been obtained in onelaboratory (2), however, the technique yields varia-ble results and has not been widely adopted.

More recently, the sex of bovine embryos hasbeen determined by using fragments of DNA that arecontained only on Y chromosomes as a means ofidentifying the same DNA fragments in the embryo(6). Due to its chemical structure, a fragment ofDNA will combine with a second DNA fragmentthat has a corresponding nucleic acid sequence.Therefore, a fragment of DNA that is specific tomales can be used as a probe to identify male DNAfragments in the embryo. Combined with technolo-gies that multiply the number of copies of the DNAfragments, this method determines the sex of theembryo using only a few cells. It is rapid (about 6hrs) and extremely accurate, but may be overtakenby the rapidly developing technology, describedabove, for separating X and Y chromosome-bearingsperm.

Animal Health Technologies

Biotechnology is rapidly acquiring a prominentplace in veterinary medical research. Initially ap-plied to vaccine development, it most recently hascontributed to efforts to develop diagnostic proce-dures and to improve detoxification systems.

Vaccines

Vaccines are agents that stimulate an effectiveimmune response but do not cause disease. Tradi-tional methods of vaccine development involvedkilling or modifying the pathogenic organism toreduce the potential for disease while preserving itsability to induce an immune response. Recombinantvaccine development involves either deletion orinactivation of genes necessary for disease, orinsertion of immunizing genes into nonpathogenicvectors.

Gene deletion technology has been successfullyused to develop both viral and bacterial vaccines. Anaturally occurring mutant of E. coli, for example,has been shown to provide protection againstgram-negative bacterial infections in cattle andswine (15,18). Live Salmonella modified to prevent

gMethods used me differenti~ s~imentation techniques including differential velocity sedimentation free-flow electrophoresis, and Convectioncounter streaming galvanization.

%e antibodies are attached (labeled) to a fluorescent compound to allow for detection.

Table 4-1—Predicted and Actual Sex Ratios of Offspring After Intrauterine Insemination of Sorted X and Y Chromosome-Bearing Rabbit Sperm

Percentage and number of offspring

Number of does Total of Predicted a Actualb

Treatment of sperm Inseminated Kindled young born Males Females Males (N) Females (N).—Sorted Y . . . . . . . . . . . . . . . . . . . . . . . . . 16 5 21 81 19 81 (17) 19 (4)Sorted X . . . . . . . . . . . . . . . . . . . . . . . . . 14 3 16 14 86 6 (1) 94 (15)Recombined X and Y . . . . . . . . . . . . . . . 17 5 14 50 50 43 (6) 57 (8)

Total ... , . . . . . . . . . . . . . . . . . . . . . . 47 13 51 — — 47 (24) 53 (27)aRepresents the results of reanalysis for relative DNA content of aliquots of sorted X- and Y-bearing sperm populations.bRepresents actual biflhs.

SOURCE: L.A. Johnson, J.P. Flook, and H.W. Hawk, “Sex Pre-Selection in Rabbits: Live Births From X and Y Sperm Separated by DNA and Cell Sorting,” Bio/. Reprcd. 41 :199-203, 1989.


reproduction in vivo have also proven to be effectivevaccines for cattle (12).

The first gene deletion viral vaccine to beapproved and released for commercial use was thepseudorabies virus vaccine for swine (26,30). Ini-tially, a single gene deletion reduced the virulence ofthe virus. Since then, other genes have been deletedwith a continuing reduction of virulence.

Vaccines can also be created by inserting intopathogens, genes that produce protective antigensthat reduce the ability of the pathogen to causedisease. 10 Some of these vaccines, however, willhave to be carefully tested because they have a slightpotential to cause human infection (31). Others arein the early developmental stages (notably herpesvirus vaccine and adenovirus vaccine).

Immunomodulators

Immunomodulators are chemical compounds thatboost or accentuate immune response. Several suchcompounds (e.g., interleukins and interferon) havebeen identified in mammals, and the genes encodingsome of these compounds have been isolated andcloned into bacteria (31). Mechanisms by whichthese regulatory proteins modulate immune re-sponse is now being investigated in domesticanimals (l). Biotechnology is being used to identifyand replicate these compounds so that their functioncan be investigated.11

Interleukin genes and genes for compounds thatcause immune responses in animals (antigens) arebeing inserted together into viral or bacterial vac-cines. This combination could possibly enhance theimmune response of the animal and lead to increasedprotection against the antigen. The recombinantinterleukins produced in bacteria or other expressionvectors may also be used therapeutically to assist inovercoming certain infections.

Diagnostics

Safe, accurate, rapid, inexpensive, and easy-to-use diagnostic procedures are critical to the dairyindustry at virtually all points in the production

process. Examples of diagnostic tests include preg-nancy tests and assays for pathogenic organisms.Many of the currently used diagnostic tests arecostly, time consuming, and labor intensive, andsome still require the use of animal assay systems.Monoclinal antibodies and nucleic acid hybridiza-tion probes can be used to produce simpler, easilyautomated, and highly sensitive and specific diag-nostic procedures.

Antibodies are proteins produced by the body inresponse to foreign chemical substances. Monoclo-nal antibodies are produced by a cell line expressingonly a single antibody type (see figure 4-6). Theycan be used to prevent disease,12 and are the primarytools for biotechnology-based diagnostics. At least15 different rapid diagnostic tests are on the marketor will be soon. These tests are highly specific andmost lend themselves to automation, potentiallyallowing their application in mass screening systemsfor disease surveillance and control. Some of thetests have been adapted to field use and can be usedby veterinarians or producers. The rapid commer-cialization of these products is having a significantimpact on animal health management and diseasecontrol.

Monoclinal antibodies are also being used inenzyme-linked-immunoabsorbent-assay (ELISA)systems to provide sensitive, quantitative bloodassays (see table 4-2) of toxins, hormones, chemicals(e.g., pesticide and antibiotic residues), and a varietyof antigens including microbial agents (19,29,34,38).Many of these tests are commercially available. Insome instances monoclinal antibody diagnosticshave been used to replace bioassays such as mouseinoculation tests.

“Nucleic acid hybridization’ can also be used todiagnose the presence of microbes and parasites.Such assays rely on the bonding of a specific DNAor RNA segment to complementary RNA or DNAfragments in a test sample. Specific segments(probes) are available to detect viruses such as

lo~e first veterinq recombinant viral vaccine was the vaccinia vectored vesicular stomatitis vaccine (27). This has been followd by the vaccfiiavectored rabies and rinderpest vaccines (3,5,50).

1 lclon~ ~terle~n genes, such as bovine ~p~, beta and ~mm intefieron, bov~e interlefin.2 ~L.2) etc. have been s~died both h vitro ~d hvivo.

12A comerci~ Prepmation of monocloMI antibodies directed to the K-99 pilus antigens of pathogenic E. cOIi, for examP1e, Prevents ~~hea hnewborn calves (31).

64 . U.S. Dairy Industry at a Crossroad: Biotechnology and Policy Choices

Figure 4-6—Preparation of Monoclinal Antibodies

*

* Mouse isimmunized With

A

a foreignsubstance or“antigen”

. . - - :. - Spleen is.1 removed and

minced torelease antibodyProducing cells(B lymphocytes)

a“. ,..,”. >

. ..’:.--,..t.t.

Myeloma cellsare mixed andfused withB lymphocytes

1

SOURCE: Office of Technology Assessment. 1988.

bluetongue, bovine virus diarrhea, and foot andmouth disease as well as many parasites andbacterial diseases. The major limitation of thistechniqu e is the small amount of target nucleic acidpresent in some samples. Also, the most reliablemethods use radioactively labeled probes, and re-

Y Mouse myelomaa

- % %

(tumor) cellsare removed

t and placed inu tissue culture

0 “..,,. . . , ~.:... s:,.:

Cells divide inliquid medium

Ju

The products of thisfusion are grown in aselective medium. Onlythose fusion productswhich are both “immor.tal ” and contain genesfrom the antibody-pro.ducing cells survive.These are called“hybridomas.”

Hybridomas are clonedand the resulting cellsare screened for anti-body production. Thosefew cells that producethe antibodies beingsought are grown inlarge quantities forproduction of mono-clonal antibodies,

quire expensive equipment and trained technicians,thus precluding their use in the field. Alternativecalorimetric techniques currently in developmentwill replace the radioactively labeled probes andmake the use of this technology more commerciallyattractive.


Table 4-2—MonoclinalAntibodies for Diagnostic Tests

E. coli K99 antigenPseudorabies virus antibodyAvian Ieukosis virus antigenEquine infectious anemia antibodyAvian reovirus antibodyBluetongue virus antibodyBluetongue virus antigenBrucella abortus antibodyAvian encephalomyelitis antibodyBovine progesteroneSulfa methazine in milkCrytosporidiumBovine leukemia virusBovine herpes virusAflatoxin BSulfamethazine-swine

SOURCE: B.1. Osburn, “Animal Health Technologies,” commissionedbackground paper prepared for the Office of TechnologyAssessment, Washington, DC, 1990.

Food Applications

Dairy products will be among the first foodproducts to be impacted by biotechnology. Forexample, during the next decade, the geneticallyengineered version of the enzyme rennet, recentlyapproved by FDA for use in cheese manufacturingsystems, will replace the enzyme preparation nor-mally extracted from the forestomach of calves.Other enzymes, which are added to the curd toaccelerate ripening, or to produce dairy productsacceptable for digestion by lactose-intolerant indi-viduals, will also be produced more economically byengineered microorganisms (22).

Dairy starter cultures are living microorganismsused for the production of fermented dairy productsincluding cheese, yogurt, butter, buttermilk, andsour cream. They have been safely consumed byhumans for centuries and serve as ideal hosts for theproduction of these natural foods. The metabolicproperties of these organisms directly affect theproperties of the food product including flavor andnutritional content. In order to improve variousproperties of food products, food microbiologistsattempt to manipulate the traits of the microorgan-isms, primarily through mutation and selection. Thecloning and gene transfer systems developed in the1980s are being used to construct strains withimproved metabolic properties more rapidly andprecisely than is possible with traditional methods.The development in this decade of new strains withprecise biochemical traits will have an impact onseveral aspects of dairy fermentation, including

production economics, shelf-life, safety, nutritionalcontent, consumer acceptance, and waste manage-ment (22).

Although much of the current work in new straindevelopment has focused on the use of E. coli andother nonfood microorganisms, there are distinctadvantages to engineering starter cultures for pro-ducing high-value foods. For example, constructionof cultures resistant to attack by viral infection willimpact processing costs by eliminating waste. Clon-ing of the genes responsible for ripening of agedcheeses will decrease storage costs by acceleratingripening. Production of natural preservatives such asnisin, effective in inhibiting foodborne pathogensand spoilage organisms, will help ensure the safetyand extend the shelf-life of fermented dairy prod-ucts. Cloning of the gene(s) responsible for enzy-matic reduction of cholesterol or modification of thedegree of saturation of milk fat will improve thenutritional quality of fermented dairy products. Theability to engineer strains capable of producingenhanced flavors or natural stabilizers will influenceconsumer acceptance of fermented dairy foods.

Engineered yeast strains capable of fermentingthe lactose in whey to value-added products, such asvitamin C, biofuels such as ethanol and methanol, orpharmaceuticals, will facilitate management of thiswaste product. Whey protein could potentially beused to produce specialty chemicals with biotech-nology.

Nucleic acid probes and monoclinal antibodiescan be used to analyze raw materials, ingredients,and finished products for pathogenic organisms,bacterial or fungal toxins, chemical contaminants(i.e., pesticides, heavy metals), and biological con-taminants (i.e., hormones, enzymes). Animal cellcultures may partially replace whole animal systemsto test for acute toxicity. Biosensors maybe used tomonitor food processing, packaging, transportation,and storage (22).

KNOWLEDGE-BASEDINFORMATION SYSTEMS

The economic vitality of an animal enterprise isdependent on expert managers who formulate,implement, and continually fine-tune relevant plansand goals in order to optimize resource use andoutput (10). However, producers may have difficultyevaluating the many interrelated factors that go into


such planning (17). Even a relatively simple animaloperation requires that complex decisions be made,based on simultaneous consideration of dynamicallychanging factors related to risk, efficiency, disease,milk production, gestation status, and weather. Withtechnology changing so rapidly, it has becomealmost impossible for agricultural managers tobalance all of the facets of milk production nowunder their control (45).

Many producers rely on consultants and experts tosift through the data and information needed forinformed management decisions. In addition, com-puters have come to play a significant role indairying, an industry that historically has usedrecords to make management decisions. Initially,data resided in mainframe computers. This allowedfor professional maintenance of the database, but theultimate user-producer had limited access to thatdatabase.

Examples of database access via telecommunica-tion systems include the Direct Access to Records byTelephone (DART) system, run by the Dairy Rec-ords Processing Center at Raleigh, North Carolina;and the Remote Management System (RMS) avail-able through Northeast Dairy Herd Improvement(DHI). Although dairy records processing centers(DRPCs) like the one at Raleigh have not developedsoftware for onfarm data calculation and informa-tion storage, the private sector has. Pollock andFredericks (33), for example, offer a microcomputer-based diagnostic program with which producers canavoid the time, recurring costs, and problems ofphone access to a distant mainframe.

As computer languages have evolved and micro-computers decreased in price and gained computingcapacity, database accessibility has increased. Mi-crocomputers provide for direct, rapid delivery ofmanagement data, as well as more efficient datahandling and user interfaces. They have, accord-ingly, revolutionized production record-keeping,and made possible onsite data manipulation andfarm-level processing of information (45).

Expert Systems and Other Computer-BasedDecision Aids

Management decisions rest on a knowledge baseconsisting of two kinds of information: that which iswidely shared and generally publicly available(domain information); and rules-of-thumb judg-ments and sometimes educated guesses (heuristics),

which typically characterize human decisionmak-ing. Both kinds of information are fundamental tocomputer-based expert systems (11), the objectiveof which is to raise the performance of the averageproducer to the expert level (39). Expert systemseffectively and rationally integrate numeric, judg-mental or preferential, and uncertain information, allof which come into play in the biologically based,weather-influenced production systems that typifyanimal agriculture (23). Another promising newinformation technology is the management-infor-mation system, with which managers can test theoutcome of various management alternatives. De-cision-support systems also hold high promise ofenabling managers to balance production inputs in away that maximizes response (output).

Expert systems, knowledge-based systems, ordecision-support systems offer the potential ofbringing the consultant to the farm through themicrocomputer. An expert system provides a flexi-ble yet structured approach to many problems thatExtension specialists now solve relatively routinely(43). Interest in these systems is beginning to emergeas a field of research and development in agriculture,reflecting both industry awareness and appreciationof new information-management technologies (13).With the widespread introduction of specializeddevelopment tools, expert system construction hasaccelerated (25,37). For example, development ofexpert systems was, until recently, restricted toexpensive LISP (a computer language) processingmachines and mainframe computers. Recent ad-vances in hardware and software have made possiblethe development of reasonably sized expert systemson microcomputers. Newly released expert systemshells have removed the necessity to program inLISP (44). While conventional computer programsmanipulate data (11), expert systems manipulateknowledge and help determine which data are usefulto the decisionmaker. They are not competitors butextensions to conventional computer programs.

Application of New Information Technology

Pressure for the management expertise offered bythese new information technologies will grow in the1990s as farms increase in size, new technologiesemerge, prices fluctuate, and consumer concernabout food safety and diet increases. Problemsolving and successful adoption of new agriculturaltechnologies like bST will be facilitated if theknowledge acquired from research and the expertise

Chapter 4-Emerging Technologies in the Dairy Industry . 67

acquired in practice are combined and made readilyavailable in easy-to-use forms.

Indeed, the possibility of fusing expert knowledgefrom different domains (extension, research, producer/managers) into a cohesive, accessible structuremight be the most promising advantage of the newinformation technologies (11). This will allowmanagement opportunities to be maximized, a widergroup of individuals to be reached, and specialists toallocate more time to new areas of concern. Expertsystems, for example, will provide farmers withonline access to needed knowledge: the humanexpert farmers would otherwise rely on gains timefor research and for expanding his or her expertise(40).

New information technologies will also revolu-tionize dairy record-keeping. For example, milk dataare typically recorded once during a 30-day intervaland extrapolated to predict total milk for that period.With new automatic metering devices, milk weightscould be recorded from each milking, For a 305-daylactation, this would increase the data points from12 to 710, if the cow is milked twice a day. Withappropriate data-handling tools, this informationcould be tied to other information, such as measuresof milk conductivity and temperature, and profilesdeveloped to monitor cows for estrus. This wouldallow increased reproductive efficiency, while re-ducing labor requirements, and decrease the need forvisual observation.

CONCLUSIONSAdvances in biotechnology and information tech-

nology will revolutionize the dairy industry. Atten-tion by farm groups, consumers, and policymakershas focused on the first major biotechnology productfrom this new era—bST. In the future bST will besurpassed by more advanced biotechnology meth-ods in animal reproduction, transgenic animal pro-duction, and animal health technologies. The moreadvanced technologies, for example, will increase acow’s endogenous bST production and milk synthe-sis by inactivating genes that inhibit bST production,eliminating the need to administer bST exogenously.Similar advanced technologies will produce higherquality cows, improve disease prevention and man-agement, and allow for the production of high-valuepharmaceuticals in milk.

These advanced biotechnologies will requiresophisticated management capability to use them

effectively. Knowledge-based information systemswill assist in providing this management capability.Expert systems, for example, can help farmersintegrate information for decisionmaking. To effec-tively use these systems farmers will need access tosoftware that is specific to their individual situationand feasible for use in a variety of economic andpolicy situations.

The technologies from this new era are in variousstages of development. Some of these technologies,such as embryo transfer, recombinant DNA vac-cines, and information systems, are already commer-cially available or will be soon. Other technologies,such as transgenic cattle and advanced reproductivetechnologies, will not be available until the end ofthe decade. The next chapter examines the collectiveeffect these emerging technologies, including bST,will have on the dairy industry in the economic andpolicy environment of the 1990s.

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