Reproduction in Domestic Animals

Reprod Dom Anim 43 (Suppl. 2), 207–212 (2008); doi: 10.1111/j.1439-0531.2008.01163.xISSN 0936-6768Postpartum Ovarian Activity in South Asian Zebu CattlePS Brar and AS NandaDepartment of Animal Reproduction, Gynaecology and Obstetrics, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab,IndiaContentsTimely onset of postpartum ovarian activity is vital foroptimal reproductive performance of dairy cows. Muchdepends upon genetic constitution of an animal althoughseveral factors interplay to govern the onset of postpartumovarian activity. South Asian zebu cattle have much longerservice period when compared with other exotic or crossbredcattle reared in the same Asian environment, which suggestsdifferences in their genetic makeup. However, the cows withsame genetic configuration expressed better reproductivepotential when reared under different environment, such asin Brazil and Mexico, which suggests the role of extrinsicfactors such as management, nutrition, environment anddisease conditions. Better management of animals (provisionof proper shade, water and housing, efficient oestrous detectionand timely insemination), good quality nutrition supplementedwith appropriate minerals and vitamins, prevention ofdiseases (vaccination, deworming, suitable therapeutic interventions)and application of biotechnology have helped inimproving postpartum ovarian activity and, therefore, reproductiveperformance of zebu cattle in Asia. No comprehensivestudy appears to have been carried out on the various aspectsof reproduction in zebu cattle reared under South Asian socioagro-climaticconditions. This paper is a modest effort tocollect what ever information available and to critically reviewthe postpartum ovarian activity in zebu cattle with specialreference to the effect of the various managemental practicesand pharmacological interventions.IntroductionZebu cattle (Bos indicus), world’s oldest domesticatedcattle, originated in Western Asia and subsequentlymigrated to larger areas in Asia, Africa and South andCentral America. There are approximately 75 recognizedbreeds, of which 30 exist in India and Pakistanalone (Chenoweth 1994). Sahiwal, Gir, Amritmahal,Haryana, Rathi, Tharparkar and Nelore are some of themost prominent breeds found in South Asia. Originatingfrom the wild, most of these are dual purpose breeds;males being used as draft animals and females for milkproduction. Lately, however, with mechanization ofagricultural operations and commercialization of dairying,high producing milk breeds became preferred. Sointense has been the need and desire for enhanced milkproduction that crossbreeding of zebu with exotic milkbreeds became fashionable in the early sixties andonwards. With this, zebu cattle however faced neglectand their numbers were drastically reduced. Havingevolved under tropical conditions, zebu were betteradapted to hot and dry climatic conditions (Barcelos etal. 1989), can utilize low-quality roughages and havebetter disease resistance when compared with Bostaurus. Their quality of milk is comparable or evenbetter than in crossbred cattle (Joshi et al. 2001). Zebucontributes significantly to draft power and meatproduction in many South Asian countries.The reproductive efficiency of Asian zebu (Table 1),however, is much lower than in their counterparts in thewestern world, the Bos taurus. They have delayed onsetof puberty, poorly expressed oestrus, long inter-calvingintervals (ICI) and distinct seasonality of reproductivetraits. In particular, they suffer from prolonged postpartumanoestrous periods (Abeygunawardena andDematawewa 2004) which make their rearing uneconomical.Hence, it is important to understand their basicreproductive physiology, identify major impedimentsand devise proper interventions to improve postpartumovarian activity.Physiology of Ovarian ActivityThe developmental and the structural properties of thepre-antral follicles are similar in B. indicus and B. taurus.The follicular wave pattern studied in some zebu breeds(e.g. in Rathi cattle; Gaur and Purohit 2007) revealedtwo (78.57%) and three follicular waves (21.42%) withcharacteristics similar to Bos taurus. Two (6.67%), three(60.00%), four (26.67%) and five (6.67%) follicularwaves have also been reported in Gir cows (Viana et al.2000). Certain characteristics of the follicular wave suchas rate of growth and atresia in dominant and subordinatefollicles were similar in cows with differentnumbers of follicular waves (Table 2). There was nodifference of cycle length (21.11 ± 1.76 and22.25 ± 1.71 days) and circulatory progesterone levelsduring dioestrus (14.24 ± 4.61 and 16.15 ± 4.45 nM)incows with one or more follicular waves.Some scientists have considered postpartum pituitaryfunctions in zebu apparently equivalent to Europeancattle (Chenoweth 1994). However, their reproductiveendocrine profiles are generally lower. The basal (Bo etal. 2003) and GnRH-induced LH release is lower in zebuthan in exotic breeds of cattle and their crosses (Portilloet al. 2008), although the follicular size and ovulationrates between Angus cows and Angus-Brahman crossesdid not differ.Circulatory progesterone profiles are also normallylower in zebu (Baruselli et al. 2004), althoughthe pattern of changes in its concentrations duringdifferent stages of reproduction is similar to that inB. taurus. Average serum progesterone concentrationson days 0 (1.30 ± 0.57 nM), 7 (3.87 ± 0.47 nM) and 15(9.41 ± 1.93 nM) of oestrous cycle and on 22 ofpregnancy (11.16 ± 2.13 nM) have been reported(Chakurkar et al. 2004). Ovariectomized zebu cattlerelease progesterone following exogenous challengesÓ 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag