Most of the human supply of animal proteins is provided by buffalo and cow followed by sheep and goat. Goat is contributing to tile health and nutrition of millions of people in the developing countries and is primarily important for production of meat. milk, skin and hair. The proportion of meat and milk produced in Pakistan is 27.4 % and 4.2 % respectively. Among the most popular breeds of goat in Pakistan is Dwarf goat. This breed is preferred over others because it has high prolificacy and is a non-seasonal breeder. These characteristics of Dwarf goat are quite in contrast to other breeds of goat and accordingly may exhibit different reproductive hormonal mechanisms than other breeds. The reproductive physiology of this animal has not been thoroughly studied in Pakistan although it plays very important role in the economy of the country. The potential of this animal can be further exploited by manipulating and controlling its reproduction. This pioneer study was therefore, undertaken to determine the patterns of pertinent circulatory hormones in female Dwarf goat. Gonadotrophin and steroid hormones and their interrelationships during various reproductive events were determined through suitable RIA methods to ascertain the age at puberty in kids, natural and induced oestrous cycle, gestation period, postpartum period, kidding interval and the response to exogenous hormone treatments.
Age at puberty in female Dwarf goat was determined by monitoring the levels of progesterone, oestradiol, LH and FSH during prepuberal and puberal phases. Progesterone profile was taken as an index of ovarian activity. During prepuberal age, there were no significant fluctuations in the level of progesterone except a small rise, a few days before the onset of puberty. Progesterone remained at the basal level whereas oestradiol showed a small rise, sometimes followed by FSH and LH secretions during the prepuberal period. This period extended to the age of 137 days, at which the animals showed the signs of puberty (oestrous cycle). The progesterone remained at the lower level of 0.024 ng ml-1 on day 0 of oestrous cycle and then increased gradually to the peak level of 5 6 ng ml-1 by day 10-11 which persisted for the next 4-5 days and then declined to the basal level at the end of the oestrous cycle (day 20). In contrast to the progesterone profile, oestradiol was found to be maximum (11.3 pg ml-1) on the day 0 of oestrous cycle which then declined to the basal level (0.3-2.04 pg ml-1) within 2-3 days. However, small rises were observed at different stages of the cycle. The LH concentration on day 0 was 11 1 ng ml-1 which then declined and fluctuated at low levels of 0.26 ng ml-1,l to 2.18 ng ml-1 during rest of the cycle. The FSH peak of 14 21 ng ml-1 was simultaneous with LH. It decreased gradually to levels of 0.78 ng ml-1 to 1.58 ng ml" within 5-6 days. FSH and oestradiol variations were more pronounced near and after the oestrous period. From these endocrine patterns, it was inferred that the mean age at puberty in Dwarf goat is 137 days and the length of its oestrous cycle is 20 days.
Hormone profiles were also monitored at different reproductive phases of adult female goat i.e., oestrous cycle, gestation and parturition. The same oestrous cycle length was confirmed by other studies conducted on adult goat. After conception higher levels of progesterone were maintained throughout the gestation, declined during prepartum period and dropped to 0.8-1.0 ng ml-1 on the day of parturition. The oestradiol levels during the first 30-50 days of gestation remained low (0.4-1,0 pg ml-1) and then increased up to 80-170 pg mil till near parturition and finally reached the peak level of 270 pg ml-1 two days before parturition. After parturition it dropped to the basal level of 0.4 pg ml-1 within 1-2 days of postpartum. FSH and LH remained at lower basal levels throughout the gestation period. The length of gestation period was found to be145 days,
The release patterns of FSH, LH, progesterone and oestradiol were monitored during postpartum anoestrous, on resumption of ovarian activity and during gestatiol1 period, The mean concentration of progesterone was found in the range of 0.1-0.3 ng ml-1 throughout the postpartum anoestrous. The resumption of cyclicity was evidenced by a gradual rise attaining the highest level within 10 days, which was followed by a slanting decrease to the basal value marking the end of the cycle. Oestradiol concentration remained low (0,1-0.8 pg ml-1) during postpartum period and with the resumption of ovarian cyclicity increased to peak level of 8.0-15.0 pg ml-1 on tile day of oestrous and again dropped to the basal level within 1-2 days of oestrous. However, in some of the animals minor peaks of oestradiol were detected prior to its progressive rise during 1-2 days before the onset of oestrous. LH and FSH remained low during the postpartum anoestrous while found high on the day of oestrous. The levels were variable from animal to animal, whereas these hormones remained fluctuating at low levels (0,1-2.0 ng ml-1) in the other phases of oestrous cycle. The level of LH dropped towards the mid luteal phase whereas FSH showed a comparatively higher level during the luteal phases. The mean concentrations of LH during the early luteal phase and gestation period were significantly lower than those during the late luteal phase. There was a progressive increase from the basal level to a peak during 1-2 days period preceding the oestrous (Follicular phase), All the animals did not show any significant hormonal fluctuations during the anoestrous period, after which there was a rise in oestradiol level, followed by LH and FSH. All these hormones showed peaks almost at the same time but the LH dropped earlier to the basal level followed by oestradiol and FSH, after 1-3 days. Some of the animals showed a dry period of about 28-30 days after the resumption of first cycle and during this period there were irregular peaks of oestradiol and LH but no change in the progesterone concentration was noticed. Sharp peaks of gonadotrophin and oestradiol were noticed at the start of each cycle which were followed by progesterone. However, some oestradiol peaks occurring at various phases of oestrous cycle are unexplainable.
Various studies were also undertaken to find out the reproductive performance of female Dwarf goat. The serum progesterone profile was used to monitor various reproductive phases such as length of postpartum period, the resumption of cyclicity, gestation period, prepartum period, parturition, litter size and kidding interval. Most of the animals conceived within 25-65 days of postpartum period. During gestation period, higher levels of progesterone were maintained with wide variations falling in the range of 3-13 ng ml-1. These fluctuations are unexplainable but the important feature observed was that the progesterone level fluctuated in the higher limits (> 3 ng ml-1) throughout the gestation. However, a few days before parturition a decline was noticed in all the animals. This decline started at 6 days of prepartum and dropped to the lowest level of 0.1 ng ml-1 after the completion of the parturition process. The length of gestation period was found 145 days. All the animals of the lot conceived during first or second oestrous cycle showing the high prolificacy of this breed. A very short kidding interval and significantly bigger litter size was observed. All the parturitions were normal and a considerable weight gain (2.5-6.5 kg) was noticed during pregnancy. The initial birth weight of a kid was found in the range of 1.5-3.2 kg. Singlets were significantly higher in weight followed by twins and triplets.
The efficient use of an animal can be achieved by using better and more precise methods of controlling oestrous. Potential benefits of induction and synchronization of oestrous cycle include increasing overall kid production and reducing management costs. Various studies were conducted with exogenous hormonal treatments to manipulate the reproductive efficiency. Ovarian stimulation with pFSH was accomplished, significant fluctuations of hormones pointed to the induction of ovarian activity. Among various studies PGF2α proved more efficient method for the induction and synchronization of cyclicity in the Dwarf goat kept under different environmental-nutritive conditions. Estrumate treatment resulted in the regression of corpus luteum within 48-56 hours and oestrous signs were observed 56-72 hour of treatment. It was observed that oestrous signs appear earlier than LH surge and the peak levels of LH were attained within 6-8 hour of visible symptoms of the oestrous period. The LH surge (7.5-30.0 ng ml-1 with a mean of 19.0 ng ml-1) and oestradiol rises (9.0-16.2 pg ml-1 with a mean of 12.0 pg ml-1) were found to have a remarkable intimate temporal relationship with each other, rising almost at the same time. The LH fall was earlier than oestradiol. The length of induced or natural oestrous cycle was not significantly affected by tr8atment or environmental or management conditions. This treatment was accompanied with high fertility rate (90%).
In these studies, methods of hormonal assay based on radio-immunoassay have been developed to establish the normal base line data of hormonal profiles of female Dwarf goat during various phases of reproduction. This would facilitate the understanding of various physiological and reproductive aspects of our livestock under different environmental/nutritive conditions and changed management practices. The precise biological data thus produced could be of great help for the biotechnologies like superovulation, embryo transfer technology, oestrous synchronization for artificial insemination (A.I.), hormone immunoneutralization for increasing fertility and more rapid genetic improvements in goat. There is a definite scope of applying these methods to improve the health and reproductive efficiency of our livestock so as to boost up their yield of milk, meat and other animal by products.