By

Zaib-Ur-Rehman

Lecturer

Department of Poultry Science

PMAS,Arid Agriculture University, Rawalpindi, Pakistan

Avian Reproductive system differs

Reproduction is organized into distinct developmental andfunctional phases

Male, it include Fertilization

formation of a patent reproductive tract

production of sperms

maniifestation of male-specific behavioral patterns

expulsion of sperm from the body

It consist of testes, epididymis, ductus deferens, papilla andphallus

TESTES

Two elliptical testes lie along the back, near the anterior end ofkidneys

Weight at birth is 2-4g & at maturity 25-35g

Left testis is heavier 0.5-3g

Mesorchium connects testes with the body wall

Serves as conduit for blood vessels and nerves

Each teste is made up of two types of parenchymal tissue,interstitial and seminephrus epithelium

Interstitial tissue contain Lyding cells Peritubular epithelial cells Nerves Lymphatic vessels Blood vessels

TESTES

Seminephras epithelium consist of

Fibroblast

Myoepitheilial cells

Connective tissue over basal lamina

Sertoli cells and developing germ cell stages are presentwithin seminephrus tubules

Their size varies depending upon the age and reproductivestage

EPIDIDYMIS The series of ducts opening into deferent duct are referred as

epididymis

It is present on the dorso-medial aspect of kidney known ashilus

Epididymis consists of rete testes

connecting ducts

efferent ducts

epididymal duct

Rete testes are lined by simple cuboidal and simple squamousepithelium

Efferent dusts have pseudostratified clumner ciliated and non-ciliated epithelium

EPIDIDYMIS

Connecting Ducts The epithelium of connecting ducts is alsopseudostratified columnar

Ductus deferens

It is the continuity of epididymis having low mucosal foldscovered with non-ciliated pseudostratified columnarepithelium

From cranial epididymis toward ductus deferens the luminaldiameter increase gradually up-to three times and denseconnective tissue along with smooth muscles surround themucosa

It runs towards cloaca for opening

PAPILLA

The deferens ductus straitens towards cloaca

Abruptly widens making receptacle a bean shaped structure

It terminates into cloacal urodeum (on dorsal wall) as papilla(copulatory organ), immediately below the opening of ureter

ACCESSORY ORGANS Accessory reproductive organs consist of Paracloacal vascular bodies

lymphatic folds

dorsal proctodeal gland

They are integral part of cloaca

Paracloacal vascular body lies alongside the receptacles

Lymphatic folds are present in proctodium wall

A non-intromittent phallus (used for sex identification) formstumescence of lymphatic folds that is seen everted immediatelyafter ejaculation

And the lymph is formed inside vascular bodies by theultrafiltration of blood

ONTOGENY OF REPRODUCTIVEORGANS

Pronephros, mesonephros and metanephros are the three pairsof primary excretory organs formed after incubation

Pronephros (wollifian duct) disappear after 4 days ofincubation

Pronephros gives rise to mesonephros tubule, Mullarian duct,connect mesonephros and cloaca and eventually persist asdeferent duct in males

Gonads arise from germinal ridge of mesonephros

Primary sex cords and rete cords are present inundifferentiated gonad

ONTOGENY OF REPRODUCTIVEORGANS

Gonadal differentiation takes place around 6.5-7 day ofincubation

Progenitors of sertoli cells in sex cords are responsible for theproduction of mullarian inhibiting substance (hormone) whichis responsible for regression of Mullarian ducts

Acromatase is an enzyme responsible for conversion oftestosterone into estradiol, so it is the key factor for gonadaldifferentiation and development of female phenotype

HORMONAL PROFILES ANDSPERMATOGENESIS

CONTINUE……

The LC being dispersed between the tubules, produce severalandrogens, primarily testosterone

As sexual maturity approaches, production of testosterone isstimulated by increased plasma concentrations ofgonadotrophins, especially, LH

In mature males, blood levels of LH is maintained by thefollowing negative feedback loop :

increased testosterone levels decreased secretion ofGnRH -, inhibits secretion of LH decreased concentrationof LH decreased concentration of androgens

increased secretion of GnRH --) increased secretion ofLH.

SEMEN PRODUCTION

Number of sperms per gram of testes produced per day isknown as daily sperm production

In case of gallus it is 80–120 million sperm per gram of testis

This value denotes number of sperms released fromseminephrous epithelium to seminephrous tubule lumen perday

This phenomenon is known as spermiation

Galliform sperms are 0.5–0.7 µm wide and 75–90 µm in length

SEMEN PRODUCTION

Acrosome of sperm is conical, nucleus is moderately bentcylindrical, and flagellum (84% of cell length) is surrounded byhelix having 25-30 mitochondrion

Following spermiation sperms are suspended in seminephrusfluid that results in formation of seminal plasma

Male ejaculate 0.1-1 cc semen with 1.5-8x109 sperms in a singlemating

SEMEN

Volume and concentration

Number of SC and daily sperm production depend on testicularsize

large-sized males will have larger testes and produce more semen

Up to 87% of daily sperm may be collected by abdominal massagemethod provided that the males are mating frequently orejaculated 5 times a week in artificial insemination (Al) program

In the absence of ejaculation, spermatozoa from lower vas deferensare reabsorbed

Volume and concentration of sperms decrease if ejaculate iscollected frequently

Color of semen will be pearly white with a pH of 7.0 to 7.2

VOLUME AND CONCENTRATION OF THESEMEN

NUMBER OF SPERMS VS NO OF EJACULATIONS

MOTILITY OF SPERMS AT DIFFERENTREGIONS

TRANSPORT AND STORAGE

Fluids from ST move SZ released into the lumen to RT

Re-absorption of the fluids at RT and vasa efferentia resulting inconcentration of SZ which then pass through ED to vas deferens(VD), reservoir of semen

In Coturnix, sperm concentration is enhanced by 60 folds andtransport through excurrent ducts takes about 24 hr (severaldays in chicken)

Cells of RT and ED synthesize and secrete proteins which helpSZ to gain motility and fertilizability

Release of fully formed SZ into lumen of ST is called asspermiation.

CONTINUE….

SZ can reach lower VD from ED in 24 hr and most of SZ in EDwould have been transported within 72 hr

40-60% of SZ/semen is given out in the first ejaculate onabdominal massage

At ejaculation, semen from VD flows out, on contraction of well-developed muscles in the lower region, through papillae intourodeum, lymph-engorged lateral phallic folds of proctodeumand to cloaca in that order; it exits with such a force that itseldom touches cloaca

SECONDARY SEX GLANDS

Domestic birds lack secondary sex glands

Seminal fluid is derived entirely from testes and/or excurrentducts

Lymphatic exudates may be added to the semen in case ofabdominal massage for collection of semen

Chicken, turkeys and Japanese quails have a gland in the dorsalproctodeum

This gland can be considered an accessory sex gland in case ofJapanese quails

METABOLISM

In vivo, fertilizing capacity of SZ lasts for 7 to 14 d whereas, in vitro, itdecreases within 15 min

From testes up to ED, SZ do not receive energy nor dispatch waste directlyto blood stream.

Cock can utilize glucose both aerobically and anaerobically

Tom semen only aerobically

Fowl SZ can utilize PL when glucose is not available; but it cannotmetabolize glutamate although it is available at high concentrations

Therefore, glutamate is not an essential component in any semen diluent but it is beneficial as a preservative probably as an alternative for Cl- ions

Seminal fluid is a poor reservoir of glucose and hence cannot cater to theenergy requirements of SZ

If lymphatic fluid is present in semen (as in case of abdominal massage)

MATING/ ARTIFICIAL INSEMINATION

Natural Mating

Courtship

Male

Waltz (drops one wing and approaches the hen with short shufflingside-steps)

Tidbitting

Cornerning

Female

MATING

Semen is ejaculated through the engorged phallic folds intoeverted cloaca

The male quickly retracts and slides off the female

The female assumes a characteristic stance and in about 3 to 4sec shakes vigorously while the male may circle and waltzaround the female

Males prefer to mate with females having a phenotype

In small flocks, females mate with the same male in theabsence of morphological differences in the male

Courtship in case of turkeys is called strutting

ARTIFICIAL INSEMINATION

Advantages Less number of males

Pedigree mating

Unlimited number of single male matings

Prefential mating

Problems of trap nesting

Pooled semen

Old males (with good characteristics)

Cage system

Turkey & broiler breeders

Male to female ratio in Muscovy ducks

Sexually transmitted diseases

CONTINUE……

Disadvantages Labor consuming

Chances of cross contamination

Involves handling of birds

MATING

Male chicken attempts to mate 10-30 times a day and 70%mating is successful

Male birds prefer to mate with pullets in the middle of socialorder and may mate with the same hen many times in a day

Competition, availability of female, social order, light,temperature and many other factors effect courting behavior

SEMEN COLLECTION

In chicken, turkeys, Guinea fowl, Pheasants and Quails, semencollection can be done by abdominal massage method

In case of Ducks and Geese, semen is usually collected byintercepting the flow of semen during natural mating.

ABDOMINAL MASSAGE METHOD

Semen can be collected from male chicken by massaging thesoft part under pelvic bone

Papilla protrudes out and semen is gently milked out in a vial

An experienced practitioner can collect semen from 145 birdsin an hour

Semen collected at morning is more efficient because of Greater volume

High sperm motility

Concentration

Semen is collected by aspiration into an ampoule containingsemen diluent at 15°C

CONTINUE…

Advantages of using diluents are

a) prevents cold-shock to the SZ since the vial itself will becooler

b) diluents buffer the acidic products of metabolism of SZ and

c) volume of semen to be handled will be practical andconvenient commercially

Since Avian SZ can metabolize glucose/fructose

TES, BFS and PO4- - act as buffers in the range of pH 6.8 to 7.5.

Milk powder and albumen are added to help freezing

SEMEN EVALUATION

Fertilizability of the SZ

To fix dilution rate to ensure 108 sperms/Al.

Color of semen must be white to pearly white; yellow (fecalcontamination) and brownish red (presence of RBCs) colors are notacceptable

Neat semen can be viewed under microscope for swirling mass ofcells sweeping across the field

Volume is found to fix dilution rate later and if weigh of semen isfund, density can be calculated as the ratio of weight to volume;density of semen is expected to be 1 mg/µL

Concentration can be assessed by automatic counters(spermatocrit)

Transmittance (spectrometric)

Integrity of SZ can be estimated by staining technique

INSEMINATION DOSE

Theoretically, 5 x 107 SZ appear to be sufficient; but, undercommercial conditions, 108 (chicken) to 2 x 108 (turkeys) SZ arerecommended

5 to 20 AI can be done per collection

Each male can yield semen 4 to 5 times/week

40 to 200 hens can be inseminated over a week out of semenfrom a cock

TIMING OF AI

Timing of Al changes according to oviposition of the species

In chicken, AI done at or within 2 hr after oviposition resulted in20 to 40% fewer fertile eggs

This is presumably because of fewer contractions of shell glandand vagina

High fertility can be expected for 7 d (chicken) and 14 d(turkeys) after Al

It is highly recommended to repeat AI after 5 d (chicken) or 7 d(turkeys) to ensure high fertility

Under commercial conditions, some poultry breeders doperform AI twice a week.

PLACEMENT OF SEMEN

Cloaca is everted by securing the bird and applying a gentlepressure on the abdomen towards the vent;

White Leghorns commonly evert the cloaca with little effortwhereas, broiler breeders may require training and carefulhandling for satisfactory results

Vaginal entry is exposed (constricted opening can be seen onthe left side of the bird)

Al pipette is inserted to about 3 cm (chicken) or 6 cm (turkeys)depth

It is highly desirable that the Al is performed within 30 min ofcollection of semen

IN VITRO STORAGE OF SEMEN

Avian semen is more fragile than that of mammals

Therefore, whenever AI is not possible to be completed within30 min, in vitro storage becomes a necessity

Semen can either be held in a liquid medium or be frozen; thelatter is not commercial because of fragility of Avian SZ (98 to99% of SZ are Lost due to freezing and thawing) as well as costand availability of liquid nitrogen

Liquid semen can be stored up to 48 hr with sufficient supply ofoxygen and glucose with sufficient buffering to maintain pHand an ambient temperature of 5 to 7°C

Hence, it is possible to hold diluted semen for 24 hr (turkeys) to48 hr (chicken) at 5°C with minimum loss

CAPONIZATION

Surgical removal of testes to castrate a male chickens resultingthe cockerel fail to develop certain male characteristics

tends to lose them if they are developed

Castration eliminate the production for male sex hormones

capons are usually docile and quiet, and their head seem smallbecause comb and wattles cease growing after castration butthe feathers of hackle, tail and saddle grow unusually long

CAPONIZATION

These males do not waste energy in courting behavior, fightingand territorial protection

Feed conversion ratio becomes better, fat deposition increasesand meat quality improves

Capon meat has more fat, so this meat is more tender, juicierand flavorful than that of intact male

Caponization is usually done at two to four weeks of age

Capons are marketed at the age of 15 to 18 weeks

A good practitioner can caponize 200 birds per hour

FERTILITY IN CHICKENS

Goal of a chicken breeder is to produce hatching eggs

Flock fertility is dependent (the level of egg and semen production)

Combined with the chickens' interest in and capability of mating

Fertility decrease as the chickens get older

For females, it is decline in fertility is due to faster release of sperm from the sperm storage tubules

meaning that the hen cannot store sperm as long

For males, it is presumed that although roosters continue to produce spermfor many years, sperm quality declines and mating activity decreases as arooster ages

Increase in early embryo deaths occurs when incubated eggs come fromchickens in the second half of their reproduction cycle. These early deathsoften appear as clears and may be mistaken for infertile eggs duringcandling or breaking out of unhatched eggs.

REFERENCES

Reece, W.O., 2005. Dukes Physiology of Domestic Animals, Panimapublishing corporation New Delhi, Banglore, India.

Whittow, G.C., 2000. Sturkie’s Avian Physiology. 5th Edition.Academic Press, NewYork, USA.

Bell, D.D. and W.D. Weaver. 2007. Commercial Chicken Meat andEgg Production. 5th Edition. Springer (India) Private, Limited.

Sreenivasaih, P.V. 2006. Scientific Poultry Production. 3rd RevisedEdition, International Book Distributing Company, Lucknow, India.Pages, 134-146.