Bovine somatotropin (bST) enhances ovarian follicular and embryonic development in sheep and cattle. In the present study, the objective was to assess whether bST given 5 days before the end of progestin-based estrous synchronization improves prolificacy and lambing rate in sheep. Pelibuey ewes (n=92) exhibiting estrous cycles at regular intervals received an intravaginal sponge containing 45mg...

T WO factors affect lambing rate: (1) frequency of lambing and (2) number of lambs born per pregnancy. Certain individual ewes have given birth to live normal lambs three times within a 12-mo. period. I t is thus apparent that under proper physiological conditions two lambings a year are possible. When the physiological processes involved and their mechanisms of action are more adequately under...

The aim of this trial was to evaluate the effectiveness (fertility and lambing) of priming with a single injection of progesterone plus PMSG in anovulatory lactating Sarda ewes subjected to the ram effect (RE) in spring. Thirty ewes (P4 group) were i.m. injected with 30 mg progesterone and 500 IU PMSG 36 h before ram introduction (d 0). This treatment was compared to a 12-day treatment with flu...

Body condition was scored at lambing (BCSL) on 101 mature (4 to 7 yr old) Polypay ewes and related to colostral immunoglobulin G (IgG) concentration and lamb performance. Colostrum samples were collected from each ewe within 12 h of lambing and litters of more than two lambs were reduced to two within 2 h of lambing. Colostral IgG concentrations decreased rapidly with time (b = -3.28; R2 = .213...

In sheep, embryonic and fetal death during pregnancy can account for 25% to 50% of the total number of corpora lutea (and thus potential embryos). The objective of this study was to determine the effects of injectable and oral Arg supplementation provided for 14 d postbreeding on the reproductive performance of naturally stimulated fall lambing ewes. Rambouillet ewes ( = 210) were exposed to ra...

The effects of progestogen-gonadotropin treatment on estrous response, ovulation rate and lambing response of crossbred ewes were examined at two times during the anestrous season (May-June and July-August). Each ewe group was treated with progestogen pessaries for 16 days and injected with 750 IU pregnant mare serum gonadotropin (PMSG) on days 17 and 32 to induce two consecutive estrous period...

Pregnancy rate following artificial insemination (AI) in sheep is variable depending on several factors. The Churra breed (milk breed of the North-West of Spain) yields lower fertility results compared with other local and European breeds (Manchega, Latxa, Merino, Lacaune, Sarde, etc.). In this work we studied the influence of many factors on the fertility of the Churra breed (insemination tech...

Factors affecting ewe prolificacy (number of lambs born per ewe lambing) were evaluated using records on 9705 Targhee, 12,721 Suffolk, and 7231 Polypay lambings from flocks participating in the US National Sheep Improvement Program. Factors considered were ewe age and season of lambing. Prolificacy was affected by age of the ewe (P<0.001) and was highest for ewes lambing between 4 and either 7 ...

Cervical anatomy limits the use of transcervical intrauterine artificial insemination (TC AI) in sheep. We have developed an instrument to cope atraumatically with the cervix; although this instrument has not affected fertilization rate or pregnancy rate through Day 3, the effects on sperm transport and pregnancy after Day 3 are not known. The objective of the present study was to determine whe...

The aim of the study was to evaluate effect body condition score (BCS) at lambing over resumption ovarian and estrous postpartum activity in lactating Pelibuey ewes. Twenty ewes were assigned two groups, according BCS lambing: Low (LBC, n = 10) High (HBC, 10). Ovarian activities daily monitored from day 3 until first or 90 days postpartum. Continuous variables analyzed using Student´s t test bi...