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

[摘要] English: A study aimed at comparing the efficiency of different progestagen treatmentsused for oestrous synchronization in indigenous South African goats wascarried out between February (autumn) and September (spring), 2000. Thestudy was carried out at Paradys experimental farm, of the University of theOrange Free State situated approximately 20km south of Bloemfontein, in theFree State province.Forty-eight indigenous feral does and 42 Boer does were used in thisexperiment, during the normal breeding season. The two breeds wererandomly allocated and distributed between the three progestagensynchronizing treatment groups of 30 does per group. The treatment groupswere medroxyprogesterone acetate (MAP), fluorogestone acetate (FGA) andcontrolled internal drug release dispenser (CIDR) groups. These three mainprogestagen treatment groups were further subdivided into six flush feedinggroups of 15 does each, namely A1 (MAP X flush feeding); A2 (MAP Xcontrol); B1 (FGA X flush feeding); B2 (FGA X control); C1 (CIDR X flushfeeding) and C2 (CIDR X control). Three groups (A1, B1 and C1) were flush fed with crushed maize for 3 weeks prior to breeding. Progestagen treatmentwas administered for 16 days. All does were injected with 300lU PMSG im atthe time of progestagen withdrawal. Oestrus was detected with the aid ofvasectomized bucks at 8 hour intervals for a period of 96 hours followingprogestagen treatment. Blood samples were collected at 4 day intervalsduring synchronization and at 8 hour intervals after progestagen treatmentremoval, 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 wholemaize grain, while another one acted as a control group, irrespective of flushfeeding and progestagen treatment prior to pregnancy. The parametersmeasured, included body weight, oestrous response, onset of oestrus,duration of oestrus, conception rate, gestation length, total litter weight, littersize, kid birth weight, sex of kids and mortality rates of kids.Body weight of the does was not affected by progestagen treatment, flushfeeding or pregnancy supplementation. Higher body weights at breeding wereassociated with a higher conception rate. Weight gain or loss prior to breedinghad no effect on conception rate and litter size. Prior to synchronization, only17.8% of the experimental does were observed to be cyclic. Followingoestrous synchronization, the overall oestrous response recorded was 96.6%.Oestrous response for three progestagen treatments was 93.1%, 96.7% and100.0% for MAP, FGA and ClDR, respectively. Progestagen treatment had asignificant (P<0.01) effect on the time to onset of oestrus following cessationof 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) treateddoes. There was no significant difference on the duration of induced oestrousperiod 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 wassignificantly (P<0.05) higher from day of device insertion until cessation oftreatment, when compared to the MAP and FGA treated does. No significantdifference in serum progesterone concentrations was observed between MAPand 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. Thedifference was non-significant. At 21 days following AI, pregnant does hadsignificantly (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 forthe 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 groupswas 149.1±4.1 days. Gestation length was not affected by progestagentreatment, flush feeding or late pregnancy supplementation. Does bearingquadruplets had a significantly (P<0.05) shorter gestation length (142.7±2.8days), when compared to does bearing singles, twins and triplets (150.0±2.8days, 148.8±4.3 days and 150.0±4.1 days, respectively). The total litter weightfor single births was significantly (P

[发布机构] University of the Free State