Synchronisation of oestrus in indigenous goats: the use of different progestagen treatments

English: A study aimed at comparing the efficiency of different progestagen treatments used for oestrous synchronization in indigenous South African goats was carried out between February (autumn) and September (spring), 2000. The study was carried out at Paradys experimental farm, of the University of the Orange Free State situated approximately 20km south of Bloemfontein, in the Free State province. Forty-eight indigenous feral does and 42 Boer does were used in this experiment, during the normal breeding season. The two breeds were randomly allocated and distributed between the three progestagen synchronizing treatment groups of 30 does per group. The treatment groups were medroxyprogesterone acetate (MAP), fluorogestone acetate (FGA) and controlled internal drug release dispenser (CIDR) groups. These three main progestagen treatment groups were further subdivided into six flush feeding groups of 15 does each, namely A1 (MAP X flush feeding); A2 (MAP X control); B1 (FGA X flush feeding); B2 (FGA X control); C1 (CIDR X flush feeding) and C2 (CIDR X control). Three groups (A1, B1 and C1) were flush fed with crushed maize for 3 weeks prior to breeding. Progestagen treatment was administered for 16 days. All does were injected with 300lU PMSG im at the time of progestagen withdrawal. Oestrus was detected with the aid of vasectomized bucks at 8 hour intervals for a period of 96 hours following progestagen treatment. Blood samples were collected at 4 day intervals during synchronization and at 8 hour intervals after progestagen treatment removal, as well as at days 14 and 21 following AI. Six weeks prior to kidding, pregnant does were divided into two groups, one supplemented with whole maize grain, while another one acted as a control group, irrespective of flush feeding and progestagen treatment prior to pregnancy. The parameters measured, included body weight, oestrous response, onset of oestrus, duration of oestrus, conception rate, gestation length, total litter weight, litter size, kid birth weight, sex of kids and mortality rates of kids. Body weight of the does was not affected by progestagen treatment, flush feeding or pregnancy supplementation. Higher body weights at breeding were associated with a higher conception rate. Weight gain or loss prior to breeding had no effect on conception rate and litter size. Prior to synchronization, only 17.8% of the experimental does were observed to be cyclic. Following oestrous synchronization, the overall oestrous response recorded was 96.6%. Oestrous response for three progestagen treatments was 93.1%, 96.7% and 100.0% for MAP, FGA and ClDR, respectively. Progestagen treatment had a significant (P<0.01) effect on the time to onset of oestrus following cessation of progestagen treatment, with ClDR treated does exhibiting oestrus earlier (27.2±4.5h), compared to the FGA (30.9±4.6h) and MAP (32.2±7.1h) treated does. There was no significant difference on the duration of induced oestrous period between the three progestagen treatment groups (FGA: 32.0±13.7h; MAP: 32.6±13.8h and ClDR: 35.2±13.7h). The mean serum progesterone concentration in CIDR treated does was significantly (P<0.05) higher from day of device insertion until cessation of treatment, when compared to the MAP and FGA treated does. No significant difference in serum progesterone concentrations was observed between MAP and FGA treated does throughout the observation period. At the onset of oestrus, the mean serum progesterone concentrations were 0.3±0.2ng/ml, 0.2±0.5ng/ml and 0.4±0.1ng/ml for MAP, FGA and CIDR, respectively. The difference was non-significant. At 21 days following AI, pregnant does had significantly (P<0.01) higher serum progesterone concentrations (17.3±0.9ng/ml), than the non-pregnant does (3.6±5.4ng/ml). The overall conception rate for all groups was 52.2%. The conception rates for the CIDR, MAP and FGA groups were 46.7%,51.7% and 60.0%, respectively. The differences were non-significant. The mean gestation length for all groups was 149.1±4.1 days. Gestation length was not affected by progestagen treatment, flush feeding or late pregnancy supplementation. Does bearing quadruplets had a significantly (P<0.05) shorter gestation length (142.7±2.8 days), when compared to does bearing singles, twins and triplets (150.0±2.8 days, 148.8±4.3 days and 150.0±4.1 days, respectively). The total litter weight for single births was significantly (P<O.01) lower, than that of multiple births (3.6±0.4; 6.0±0.9; 6.7±1.5; 6.4±0.5 for singles, twins, triplets and quadruplets, respectively). The mean litter size was 2.0±0.9 and this was not affected by progestagen treatment. Flush fed does had a significantly (P<0.05) lower litter size, when compared to the control does (1.8±O.9 vs 2.3±1.0). Does lighter than 41kg produced a significantly (P<0.01) lower litter size, when compared to heavier does. The average birth weight of the kids was 2.7±0.5kg and was not affected by late' pregnancy supplementation. Crossbred (Indigenous X Boer) and male kids (2.7±0.8kg and 2.7±O.8kg, respectively) were significantly (P<0.05) heavier when compared to pure Boer and female kids (2.6±0.9kg and 2.6±O.8kg) at birth. The mean birth weights for quadruplets, triplets, twins and singles were 1.6±0.3kg, 2.3±O.6kg, 3.1±0.5kg and 3.6±0.4kg, respectively, and these differed significantly (P<O.01)from each other. The overall perinatal mortality rate of kids up to 48 hours postpartum was 22.3%. Kids from supplemented pregnant does had significantly (P<0.05) higher perinatal mortality rate when compared to kids from the control does (31.9% vs 14.0%), respectively. Perinatal mortality rates of kids increased with an increase in litter size and decreased with an increase in birth weight. It is concluded that synchronization of oestrus with the use of progestagen (irrespective of the type used), is efficient in synchronizing oestrus. The type, duration and time of nutritional supplementation as well as the body condition of the animal should be born in mind whenever flush feeding and supplementation programmes are considered. There are many factors (nutritional and managerial) that could influence the conception rate following fixed-time AI in goats.