ABSTRACT
The experiment was conducted to determine the reproductive performance (lambing rate and litter size) of sheep artificially inseminated at a synchronized estrus in relation to rams, dose of PMSG and number of artificial inseminations performed. During spring cyclic Merino adult ewes were treated with intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP). After 14 days sponges were removed and the females received an intramuscular injection of either 375 or 400 IU pregnant mare serum gonadotropin (PMSG). Estrus detection was performed with vasectomized rams. Females in estrus were cervically inseminated with fresh diluted semen from different rams either once or twice. Data on lambing rate and litter size were recorded. Lambing rate was not affected by rams or number of inseminations. A higher proportion of ewes that received 400 IU PMSG lambed compared with those receiving 375 IU PMSG (76.47 percent v 54.32 percent; p<0.01). Litter size was not affected by any of the variables under study
Subject(s)
Animals , Female , Insemination, Artificial , SheepABSTRACT
The objectives of this study were: 1) to determine estrus presentation and distribution following a conventional method of estrus synchronization (progestagen-PMSG treatment) in an ewe herd and 2) to analyze estrus presentation and distribution in adult ewes and ewe lambs. During spring a total of 300 cyclic Merino ewes, including 231 adult ewes and 69 ewe lambs were treated with intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP). After 14 days sponges were removed and 375 IU pregnant mare serum gonadotropin (PMSG) were administered i.m. Estrus detection was performed with vasectomized rams. Ewes were inspected for the presence of marks at 4-hours intervals. Sponge losses, estrus synchronization and distribution were analyzed for adult ewes and ewe lambs. It was detected 1 per cent (3/300) of sponge losses. Estrus synchronization rate was 92.93 per cent (276/297) for the ewe herd, being 93.48 per cent (215/230) for adults and 91.04 per cent (61/67) for lambs (p>0.10). Estrus onset was detected from 28 to 68 hours following treatment in both classes of females. The interval between sponge removal and estrus onset was 46.88 ñ 11.78 hours for the ewe herd, being 46.99 ñ 12.22 hours for adult ewes and 47.31 ñ 10.94 hours for ewe lambs (p>0.10). Statistical differences were found only for the intervals 34-38 (p<0.10) and 50-54 hours (p<0.05) between adult ewes and ewe lambs. It was concluded that the treatment used was effective for estrus synchronization in ewes
Subject(s)
Animals , Female , Adult , Estrus Synchronization , Gonadotropins, Equine , Medroxyprogesterone Acetate , SheepABSTRACT
A pool of polyurethane sponges impregnated with medroxyprogesterone acetate (MAP) was prepared. Real level of progestagen on sponges was checked prior to sponge treatment insertion. During spring a total of 126 cyclic Merino ewes were intravaginally treated with MAP-impregnated pessaries for the synchronization of estrus. After 14 days treatment, sponges were removed. Estrus detection was performed with vasectomized rams. Ewes were inspected for the presence of marks twice a day. Ewes in estrus were artificially inseminated with fresh diluted semen containing a dose of 300x106 total sperm. Artificial insemination was performed 12 hours after estrus presentation. Residual levels of MAP (RMAP) on removed sponges were measured by spectrophotometry at 241 nM and examined in relation to their estrus response and fertility. Real dose of MAP was in average 54 mg. RMAP found on sponges following treatment were in average 25.00 ñ 0.84 mg. Percentage of estrus synchronization was 92.86 per cent and pregnancy rate was 50.43 per cent. There were no significant differences for RMAP between ewes with (24.70 ñ 0.86 mg) and without (28.89 ñ 3.65 mg) estrus response (p>0.10). There were also no significant differences for RMAP between pregnant (25.56 ñ 1.25 mg) and non-pregnant (23.83 ñ 1.18 mg) ewes (p>0.10). It was concluded that the 60 mg MAP dose conventionally used for estrus synchronization in ewes is higher than the amount uptaken by the females