GENETIC AND BIOLOGICAL ASPECTS OF ZEBU ADAPTABILITY 1 ,2

J. W. Turner

Louisiana State University, Baton Rouge 70803

Summary

The util i ty and documentat ion of traits and characteristics of Zebu, Bos indicus, cattle in beef production in the United States are dis- cussed with reference to adaptation. Zebu cattle are uniquely suited to hot climates due to coat, hide, skin and hematological attributes. Form, growth and physiological aspects are unique genetic attributes which are different from those of Bos taurus cattle. Compared with Bos taurus cattle, Zebu cattle are lower in re- production, later maturing, slower growing and lower in beef quality. Zebu cattle are valuable in crossbreeding, with adaptive aspects trans- mitted and large amounts of heterosis in growth, maternal effects and reproductive traits. (Key Words: Beef cattle, Adaptat ion, Zebu, Bos indicus, Production.)

Introduction

Adaptat ion is a broad term used to describe the ability of animals to adjust to environmen- tal conditions or to infer genetic modifications that make animals more suitable for existence under specific environmental conditions. Zebu, Bos indicus, cattle are widely recognized as adaptable to tropical and subtropical environ- ments that are restrictive to Bos taurus cattle. However, objective measurements of traits and characteristics that directly affect adaption are limited. Most work documents the effects of environmental factors on production variables or the broad effects of breed comparisons under specified environments.

Discussion

Research into adaptat ion can be viewed from two classical perspectives:

= Presented at a symposium on "The Role of Zebu Cattle in Efficient Beef Production" at the Annu. Meet. of the Southern Sec. of the ASAS, Feb. 5, 1979, in New Orleans, LA.

ZPublished with approval of the Director of the Louisiana Agr. Exp. Sta.

1. The direct measure of performance under measured environmental stress is the ap- proach utilized by response scientists. The application is to control the envi- ronmental stresses reducing performance or to predict the ability of the animal to adjust to environmental stresses (Dowling, 1974; McDowell, 1974).

2. The classical genetic approach of fitness details a selective value for adapted ani- mals to effect a populat ion change i n harmony with existing environmental conditions (Falconer, 1960).

Rohles (1974) presented an interesting con- cept for environmental research as the eco- system complex. The ecosystem complex in- cluded: ( i ) physical factors defining the envi- ronment; (2) organismic factors, which are factors describing the animal, and (3) adaptive factors, those factors that interact with the physical factors and organism to allow for adaptation. While adaptat ion is a complex sub- ject, the application of knowledge concerning Zebu cattle is important to beef production in several environments. This paper will present pert inent research that documents the adaptive aspects of Zebu cattle and their uti l i ty as a genetic entity.

Bonsma (1973) presented a comprehensive review of adaptat ion and beef cattle breeding. Zebu, Bos indicus, cattle evolved in the South- ern hemisphere and ~tdapted to muggy and scorching environments. These include environ- ments defined by mean monthly temperatures of 18 C or higher and relative humidi ty of 55% or higher. It was noted that humidi ty was of little importance compared to temperature. Therefore, particular emphasis was placed on temperature effects in the discussion of Zebu cattle. Because Zebu cattle are smooth- coated, have primary hair follicles, have better developed sweat and sebaceous glands than Bos taurus cattle and can lose more moisture by evaporation, they are cited as adaptable to hot climates. In addition, the ability to maintain thermal equilibrium is a necessary factor for

1201

JOURNAL OF ANIMAL SCIENCE, Vol. 50, No. 6, 1980

1202 TURNER

normal function and performance. Bonsma (1973) expanded Zebu attributes to include coat color, pigmentation, conformation, genetic adaptation to the source of nutrit ion (forages) and resistance to pests and disease. The implica- tions are that Zebu cattle are adaptable to poorer quality forages and soils of low pH and are resistant to ectoparasites and diseases trans- mitted by ectoparasites. Frisch and Vercoe (1978) studied 15-month weights of Bos indi- cus, Bos taurus and crosses and listed Brahmans as resistant to ticks, worms, pinkeye, heat and nutritional fluctuations. Brahmans (Bos indicus) were also cited as having lower inherent volun- tary feed intake and lower relative maintenance requirements.

Howes (1963) reported that hematological comparisons of Brahman and Hereford cattle in Florida were related to respiration and adaptation. Brahman cattle were observed to have higher red blood cell counts, total cell volume and hemoglobin values. Venous blood of Brahman cattle had less carbon dioxide than did that of Herefords. These results imply that Brahman cattle are capable of maintaining lower respiration rates during periods of high ambient temperatures. Evans (1963) confirmed these hematological advantages for Zebu cattle as well as the effect of the advantages on adaptat ion to temperature stress.

Allen (1962) compared Brahman and Jersey cattle skin temperatures and respiration rates at air tempetaures from 24 C to 35 C. Zebu cattle had lower respiration rates at all levels of skin temperature, and skin temperature of Zebus closely followed air temperature. Zebu cattle had the lower skin temperature below 24 C and the higher mean temperature above 35 C. It should be noted that Jersey cattle are generally accepted as adapted to warm climates.

Cartwright (1955) documented advantages in heat tolerance of Brahman and F-1 crosses over Hereford cattle. Superior summer gains were cited as important measures of adaptive merit of Brahmans and the Brahman x Here- ford crosses.

Johnson (1963) cited the major factor favoring Brahman cattle as heat tolerance or the ability to respond to increasing heat loads.

Tugwell et al. (1969) studied levels of Brah- man breeding and color as factors affecting horn fly, Haematobia irritans (L.), attractive- ness and(or) repellency. As Brahman breeding (percentage of blood) increased, actual fly counts decreased, regardless of color. Subse-

quent investigation of ambient temperature, humidity and sunlight in association with horn fly counts and respiration rate, surface temper- ature and moisture of the animal did not define attractiveness and(or) repellency. Brahman breeding was cited as the important variable. Brown et al. (1977) found lighter coat color to be important in reducing fly counts in Arkansas. Breed differences were important during peri- ods of high fly populations. No specific refer- ence to the Brahman breed was made, yet purebred cattle were studied. Rick (1962) established Bos indicus breeding as a factor promoting resistance to the cattle tick, Boopbi- lus microplus. Bos indicus x Bos taurus crosses were more resistant than were Bos taurus cattle. A port ion of the resistance was termed innate. Strother et al. (1974) documented the resist- ance of Brahman cattle to the Lone Star tick, A m b l y o r n m a americanum. Both Brahman and Brahman • Hereford crosses were more re- sistant than Herefords.

Steelman et al. (1973) and Steelman et al. (1976) documented the efficacy of Brahman characteristics in reducing weight loss due to mosquito attack. Brahman steers were found to be more tolerant to mosquito at tack than were Herefords on the basis of weight gains. Dowling (1974) dismissed the notion that heat tolerance limits Bos taurus cattle in Australia. He cited the resistance of Bos indicus cattle to ticks and parasites and calving ease as the important adaptive attr ibutes and suggested that crossbreeding with Bos taurus cattle is necessary to improve production efficiency.

The environmental effects of nutritional status and breed x environment interaction on Zebu cattle are difficult to document. Zebu cat- tle are universally accepted as adapted to poor quality forages. Stated differently, they can survive and produce in restrictive environments. Most at tr ibute this quality of Zebu cattle to a genetic ability to utilize forages more effi- ciently. Rogerson et al. (1968) compared Boran (Zebu) steers with grade Herefords (Bos taurus) on high energy diets and concluded that Zebu steers have lower dry matter intakes but do not use feedstuffs more efficiently. Zebu cattle had lower metabolic rates, and water intake was similar. Efficiency was measured as growth relative to feed intake. Lofgreen et al. (1975) reported that Brahman • British steers utilized energy more efficiently than British steers under a heat stress of warm drinking water (32.2 C) compared to cooled drinking water

ADAPTABILITY ASPECTS OF ZEBU CATTLE 1203

(18.3 C). Moore et al. (1975) reported a sig- nificant breed x diet (energy level) interaction in diet digestibilities. They observed that Brah- man bull calves were more efficient on low energy (high roughage) diets than were Here- fords, yet Herefords were superior to Brahmans on a high energy (low roughage) diet. The im- plication was that Brahman cattle utilize low energy diets more effectively than high energy diets. Related observations made by Bonsma (1973) verify that Zebu cattle founder readily under intensive feedlot conditions with moder- ate to high energy diets. Feed intake, nutri- tional requirements for growth and mainte- nance requirements for Zebu cattle may be different from those for Bos taurus cattle (Frisch and Vercoe, 1978). Evidence at least suggests advantages for Zebu cattle on roughage diets. Zebu cattle do not adapt to high energy feeding as readily as Bos taurus .

The unique qualities of Zebu cattle in com- parison to Bos taurus breeds are important considerations for the breeding decisions made by many cattlemen. Because Zebu cattle are humped and atypical in conformation, and appear by observation to be shallow and nar- row in the heart girth and narrow in the crops, they may not be considered as acceptable beef animals. Zebu cattle grunt or bellow more than low, and their disposition is truly different. Zebu cattle are docile and quiet yet possess the ability to become aroused more quickly than do Bos taurus cattle. Zebu cattle are difficult to handle under forced or stress working condi- tions. Some will fight, jump or exhibit ex- tremely nervous behavior. Others sulk and refuse to be moved when they tire or face unfamiliar surroundings. It is safe to say that more research into animal behavior is needed and that learning and understanding the Zebu psyche will be an interesting research area. Some Zebu cattle are extremely docile while others are totally unruly. Disposition is be- lieved to be heritable, and it is the most impor- tant reason why Zebu cattle are not used more in crossbreeding.

Zebu cattle are poorer in reproductive effi- ciency than Bos taurus cattle under subtropical conditions in the United States (Warnick, 1963; Reynolds, 1973; Wythe, 1970; Bazer, 1973). Howes (1963) stated that Brahman cows had lower ovulation rates than did Hereford cows. Also, lower levels of thyroid, adrenal and ovarian activity were cited as factors con- tributing to the Brahman's greater heat toler-

ance but lower reproductive efficiency. Howes (1963) and Hentges and Howes (1963) indi- cated that Brahman cows milked more than Herefords and used feedstuffs and nutrients from body stores to lactate at the expense of reproduction. Delayed estrus and subsequent lower reproductive rates were obvious effects. Kincaid (1963) documented a lactation status x breed interaction in fertility (calving rate). Dry Brahman cows were 13% more fertile than wet Brahman cows, while wet Hereford cows bred better (10%) than dry Hereford cows.

The Brahman breed of the United States has other unique reproductive qualities. Perinatal calving losses are normally greater in purebred Brahman herds (Reynolds, 1973). Franke et al.

(1975) documented the incidence and charac- terized the weak calf syndrome in Brahman cattle. Purebred Brahman calves are often lack- ing in vigor at birth and are adversely affected by cool, moist conditions. Puberty occurs later in Zebu cattle than in Bos taurus breeds (Plasse et al., 1968b; Bazer, 1973). Late sexual matu- rity is a well-known characteristic of Zebu cattle. Brahman cattle have a gestation period of 292 days (Plasse et al., 1968c), and calving intervals average 410 days (Plasse et al., 1968a). Plasse et al. (1968b) observed a seasonal estrus activity in Brahman heifers, with spring and summer activity greatest. Zebu cattle are recognized as having excellent longevity and little dystocia (Wythe, 1970).

Brahman cattle have been characterized as slow-growing feedlot cattle that are lower grading and produce less tender beef (Turner, 1973). Slower growth performance for pure- bred Brahman steers was also reported by Crockett (1973) and Peacock et al. (1973). Carpenter (1973) reported that compared to straightbred Brahman, British • Brahman crosses produced carcasses with increas~ed weight, grade, palatability and fat content with lower percentage lean and bone. Zebu purebreds are not recognized as efficient beef cattle but are desirable in restrictive environments.

The genetic utility of Zebu cattle has been well documented in beef production systems. Zebu crossbreds, Bos indicus • Bos taurus ,

including reciprocal crosses, exhibit heterosis in several economically important traits. The greatest and most important hybrid effects are found in reproductive performance (Turner e t

al., 1968; Bazer, 1973). Maternal heterosis is large for weaning weight (McDonald and Turner,

1204 TURNER

1972). Preweaning and postweaning growth tra ts exhibi t heterosis of economic significance and are well documented . Carptenter (1973) stated that heterosis for carcass traits was l imited a lmost entirely to traits associated with carcass weight.

The u l t imate uti l i ty of Zebu catt le has been in wel l -def ined crossbreeding programs. Achiev- ing adapta t ion to hot cl imates and poor forage areas with Zebu crossbreeds via additive in- heri tance and utilizing he tero t ic advantages in re!rroductive, maternal and g rowth- re la ted traits is the manner in which breeders use Zebu cattle. As atypical cattle, they excel in cross- breeding systems utilizing the additive inheri- tance of Bos t a u r u s breeds. Crossbreeds are in termedia tes that adapt in much the same way as Zebu parental s tock ye t per form be t te r than the Bos t a u r u s parent breed. The success o f such crossbreeding has led to the estabTishment of several new breeds based upon percentage of blood and selection. The c o m m o n fac tor in most is that Zebu inheri tance has been ut i l ized for adapta t ion to produce in hot climates. It is impor tan t to note that the South and Sou th - west are regions of relatively high tempera tures in which a sizable por t ion o f the United States beef cattle popula t ion is located. Zebu cross- bred catt le can and do move into more t emper - ate zones, but the advantages of Zebu breeding apparent ly decline as B o s t a u r u s catt le become be t te r adapted and per form mo.re favorably. Adapta t ion to cold weather quickly becomes the more impor tan t considerat ion.

Purebred Zebu catt le are found in greatest numbers in Texas, Florida and Louisiana. H o w - ever, interest has al lowed for expansion o f Zebu cat t le into o ther states in the South and Southwest . Addi t ional ly , Zebu breeders have advanced interest in developing and re- cording di f ferent types of Zebu cattle. The Amer ican Brahman Breeders Associat ion cur- rently maintains a single herdbook, while the Pan Amer ican Zebu Associat ion has separate herdbooks for Zebu Tejano, Indu-Brazi l and Gyr cattle.

Zebu catt le in the United States occupy a unique posit ion. Purebreds are normally no t used in commercia l product ion , and many ca t t lemen are un in fo rmed about the mer i t o f Zebu breeding. There is no quest ioning the effect ive use o f Zebu catt le for crossbreeding. Probably no o ther types or breeds have such a wel l -def ined and accepted role in commerc ia l beef product ion .

Literature Cited

Allen, T .E. 1962. Responses of Zebu, Jersey and Zebu • Jersey crossbred heifers to rising temper- atures, with particular reference to sweating. Australian J. Agr. Res. 13:165.

Bazer, F. W. 1973. A twenty-year summary of heter- otic effects on reproduction in Florida cattle. In M. Koger, T. J. Cunha and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. Series 2. University of Florida Press, GainesviUe.

Bonsma, J. C. 1973. Crossbreeding for adaptability. In M. Koger, T. J. Cunha and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. Series 2. University of Florida Press, Gainesville.

Brown, C. J., J. L. Lancaster and R. W. Parham. 1977. Treatment and breeding group effects on hornfly counts. J. Anim. Sci. 45 (Suppl. 1):41.

Carpenter, Z. L. 1973. Effects of crossbreeding on car- cass characteristics. In M. Koger, T. J. Cunha and A . C . Warnick (Ed.) Crossbreeding Beef Cattle. Series 2. University of Florida Press, Gainesville.

Cartwright, T. C. 1955. Responses of beef cattle to high ambient temperatures. J. Anim. Sci. 14: 350.

Crockett, J. R. 1973. Finishing calves from a crisscross breeding system. In M. Koger, T. J. Cunna and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. Series 2. University of Florida Press, Gainesville.

Evans, J. B. 1963. Adaptation to subtropical environ- ments by Zebu and British breeds of cattle in relation to Erythrocyte characters. Australian J. Agr. Res. 14:559.

Dowling, D. F. 1974. Discussion of the influence of environmental factors on cattle production. In Livestock Environment Affects Production, Re- production, Health. ASAE, St. Joseph, MI.

Falconer, D. W. 1960. Introduction to Quantitative Genetics. The Ronald Press Co., New York.

Franke, D. E., J. D. Combs, Jr., W. C. Burns and W. W. Thatcher. 1975. Neonatal health status in Brah- man calves and blood components. J. Anim. Sci. 40:193 (Abstr.).

Frisch, J. E. and J. E. Vercoe. 1978. Utilizing breed differences in growth of cattle in the tropics. World Anita. Rev. (FAO) 25 ;8.

ltentges, J. F., Jr. and J. R. Howes. 1963. Milk pro- duction. In T. J. Cunha, M. Koger and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. Univer- sity of Florida Press, Gainesville.

Howes, J. R. 1963. Blood composition and physiology of Brahman and Herefords. In T. J. Cunha, M. Koger and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. University of Florida Press, Gaines- ville.

Johnson, J .E . 1963. Response to environment. In T. J. Cunha, M. Koger and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. University of Florida Press, Gainesville.

Kincaid, C. M. 1963. Crossbreeding in the southern region. In T.J . Cunha, M. Koger and A.C. Warniek (Ed.) Crossbreeding Beef Cattle. Univer- sity of Florida Press, Gainesville.

Lofgreen, G. P., R. L. Givens, S. R. Morrison and T. E. Bond. 1975. Effect of drinking water tempera- ture on beef cattle performance. J. Anim. Sci. 40:223.

ADAPTABILITY ASPECTS OF ZEBU CATTLE 1 2 0 5

McDonald, R. P. and J. W. Turner. 1972. Estimation of maternal heterosis in preweaning traits o f beef cattle. J. Anita . Sci. 35:1146.

McDowell, R. E. 1974. Effect o f environment on the functional efficiency of ruminants . In Livestock Environment Affects Production, Reproduct ion, Health. ASAE, St. Joseph, MI.

Moore, R. L., H. W. Essig and L. J. Smithson. 1975. Influence o f breeds o f beef cattle on ration utilization. J. Anim. Sci. 41:203.

Peacock, F. M., G. W. Kirk, J. W. Carptenter , M. Koger and A. Z. Palmer. 1973. Feedlot performance of straightbred and crossbreds. In T. J. Cunha, M. Koger and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. University of Florida Press, Gaines- ville.

Plasse, D., M. Koger and A. C. Warnick. 1968a. Repro - ductive behavior of Bos indicus females in a sub- tropical environment . III. Calving intervals, inter- vals f rom first exposure to concept ion and intervals f rom parturi t ion to conception. J. Anim. Sci. 27:105.

Plasse, D., A. C. Warnick and M. Koger. 1968b. Repro - ductive behavior o f Bos indicus females in a sub- tropical environment . I. Puberty and ovulat ion f requency in Brahman and Brahman • British heifers. J. Anim. Sci. 27:94.

Plasse, D., A. C. Warnick, R. E. Reese and M. Koger. 1968c. Reproductive behavior o f Bos indicus females in a subtropical environment . II. Gesta- tion length in Brahman cattle. J. Anim. Sci. 27: 101.

Reynolds, W . L . 1973. Reproduct ion o f Brahman, Angus, Africaoder, and their crosses at Jeanerette, Louisiana. In M. Koger, T. J. Cunha and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. Series 2. University o f Florida Press, Gainesville.

Rick, R. F. 1962. Studies on the resistance of animals to infestat ion with ticks. Australian J. Agr. Res. 13:532.

Rogerson, A., H. P. Ledger and G. H. Freeman. 1968.

Food intake and live weight gain comparisons o f Bos indicus and Bos taurus steers on a high plane of nutr i t ion. Anita. Prod. 10:373.

Rohles, F. H., Jr. 1974. The ecosystem complex - A new approach in defining the animal-envi- ronmen t relationshipship. In Livestock Environ- ment Affects Product ion, Reproduct ion, Health. ASAE, St. Joseph, MI.

Steelman, C. D., T. W. White and P. E. Schilling. 1973. Effects of mosqui toes on the average daily gain of Herefords and Brahman breed steers in South Louisiana. J. Econ. Entomol . 66:1081.

Steelman, C. D., T. W. white and P. E. Schilling. 1976. Efficacy o f Brahman characters in reducing weight loss of steers exposed to mosqui to attack. J. Econ. Entomol . 69:499.

Strother, G. R., E. C. Burns and L. I. Smart. 1974. Resistance of purebred Brahman, Hereford, and Brahman • Itereford crossbred cattle to the Lone Star tick, Arnblyomma americanum (acarina: exodidae). J. Med. Entomol . 11:559.

Tugwell, Phillip, E. C. Burns and J. W. Turner. 1969. Brahman breeding as a factor affecting the a t - tractiveness or repellency o f cattle to the horn fly. J. Econ. Entomol . 62:56.

Turner, J. W. 1973. Brahman • European crosses versus other breeds in feedlot. In M. Koger, T. J. Cunha and A. C. Warnick (Ed.) Cross- breeding Beef Cattle. Series 2. University of Florida Press, Gainesville.

Turner , J. W. (Bill), B. C. Farthing and G. L. Rober t - son. 1968. lteterosis in reproductive performance o f beef cows. J. Anita. Sci. 27:336.

Warnick, A. C. 1963. Reproductive performance. In T. J. Cunha, M. Koger and A. C. Warnick (Ed.) Crossbreeding Beef Cattle. University of Florida Press, Gainesville.

Wythe, L. D., Jr. 1970. Genetic and environmental effects on characters related to productive ability of the American Brahman. Ph.D. Thesis. Texas A&M Univ., College Station.