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Two trials were conducted over consecutive years to examine the effects of ewe body condition and post-mating nutrition on ovulation rates and embryo survival. Trial 1 used 146 Polypay ewes ranging in age from 5 to 8 years in a 3 x 2 factorial array of pre-mating (high-H, low flushed-LF and low unflushed-L) and post-mating nutrition (high and low) treatments. Trial 2 was a 2 x 2 x 2 factorial array of 60 Polypay and 60 Coopworth x Polypay (C x P) three year old ewes, two pre-mating (H and LF) and two post-mating (high and low) treatments. To estimate timing and extent of embryo loss, two methods of embryo detection were employed during Trial 2. Real-time ultrasound was performed on all ewes at 21, 28, 34 and 45 days post-mating. Blood samples were also collected on these days for analysis of Pregnancy-specific Protein B (PSPB) levels. There was no effect of pre-mating treatment or ewe age on ovulation or conception rates for Trial 1. Pre-mating treatment was significant in Trial 2, with H ewes having higher ovulation rates than LF ewes. Pre-mating treatment, post-mating treatment, ewe age (for Trial 1) and genotype (for Trial 2) had no effect on mean litter size in either trial. Analysis of litter size among ewes with twin and triple ovulations showed pre-mating treatment to be significant among triple ovulators in Trial 1, where L ewes had much lower litter size (1.86) than LF (2.37) or H (2.60) ewes. In Trial 2, post-mating treatment was significant among the ewes with triple ovulations, with ewes on low nutrition having lower litter size (2.01) than ewes on high nutrition (2.59). Two-way interactions were significant among twin and triple ovulators in Trial 2. Breed x pre-mating interaction among twin ovulating ewes showed C x P LF ewes to have lower litter size (1.43) than the H ewes (1.87), while the opposite was true for Polypay ewes. Pre- x post-mating treatment interaction among triple ovulators showed LF ewes on low post-mating nutrition had lower mean litter size. This effect is largely due to lower litter size in the C x P triple ovulators on low post-mating nutrition. Data available from the ultrasound diagnosis showed little indication of treatment effects on amount or time of embryo loss. Ewes bearing single or multiple embryos differed in PSPB level at day 45, but not at earlier times. However, there were no differences in PSPB levels in ewes with twin or triple embryos at any of the trial days. Assay for PSPB failed to facilitate detection of the amount or time of embryo loss, as determined by ultrasound. / Graduation date: 1991

Previous work in this laboratory revealed that hormone analysis using fecal samples may predict the number of fetuses carried by pregnant ewes at mid- to late gestation. Reliable lambing number prediction is useful to the producer. Using gas chromatography/mass spectrometry the 5��- and 5��-series of pregnanes and selected 4- and 5-pregnenes were monitored in the feces of 36 black and white-face cross ewes during early gestation. Feces were collected at d 5, 19, and 30 post-mating. Endoscopy was used at d 6 to determine the number of corpora lutea, and litter size data were collected at term. The number of copora lutea was not related (P>.05) to hormone concentrations at any of the sampling times (ANOVA-GLM). No differences in hormone levels were detected at d 5 in response to lambing number. At d 19, 5��-pregnane-3,20-dione and 5��-pregnane-3��,20��-diol were higher in ewes carrying triplets than ewes carrying twins (P���.008). At d 30, 3��-hydroxy-5��-pregnan-20-one was higher in ewes carrying triplets than twins (P<.05). Five progestins, including progesterone and 20��-hydroxy-4-pregnen-3- one, were lower at d 5 in ewes that conceived (n=26) than in ewes that did not conceive (n=6) at the first mating (P<.05). Concentrations of ten progestins were different (P<.05) (some higher and some lower) between groups of ewes that conceived at the first mating versus those that conceived at the second mating. In ewes that conceived at the second mating, pregnenolone and 5��-pregnane-3,20- dione were higher (P<.05) at d 5 than at d 5 of their previous non-conceptive cycle. Of the six ewes that were mated a second time, two still did not conceive but had elevated concentrations of three 5��-pregnanes (P<.05). Although there are differences in progestin profiles in ewes carrying different numbers of fetuses, concentrations alone are not adequate predictors of prolificacy at early gestation. It is inconclusive whether detection of pregnancy is possible as early as d 5 of gestation. / Graduation date: 2001

Coopworth sheep, a newly available genotype, were compared with other genotypes in two trials to assess cumulative lamb and wool production and contributing components related to survival, reproduction and growth, and for the effects of ewe body weight on reproductive traits. In a third trial, various genotypes generated in the process of upgrading native Kaghani sheep, were evaluated for lamb and wool production. In the first two trials six ewe genotypes, generated by mating Coopworth (C), Polypay (P) and Suffolk (S) rams to Polypay and Coopworth-type ewes, were exposed to Hampshire rams for spring lambing from 1986 through 1990. Overall conception rate averaged 96% and ranged from 93% for S X C ewes to 97% for P X C ewes. Sire breeds were not different in ovulation rate but daughters of Polypay dams averaged .18 higher ovulation rate than daughters of Coopworth dams (P<.05). Uterine efficiency for twin ovulators was .86 with little variation among sire breeds; however, daughters of Polypay ewes had a mean uterine efficiency of .93 compared to .78 for daughters of Coopworth ewes (P<.05). Mean litter size at birth averaged 1.63 and ranged from 1.45 for C ewes to 1.75 for S X P ewes. Ewes from Polypay dams had higher mean litter size (P<.01) than those from Coopworth dams (1.73 vs 1.54), but differences between sire breeds were not significant. Ewes from Suffolk sires weaned the heaviest lambs while ewes from Polypay sires weaned the greatest number of lambs, resulting in similar weight of lamb weaned per ewe mated. Adjustment of lamb production for ewe metabolic body size resulted in Coopworth-sired ewes being more efficient than the heavier Suffolk-sired ewes. Coopworth-sired ewes produced 32% more wool than ewes sired by the other two breeds. Combining lamb and wool production in an index resulted in a range of less than 2% among sire breeds for gross productivity per ewe mated. Productivity of Rambouillet ewes studied under Pakistani conditions declined significantly over time. Crossbred lambs were generally heavier at weaning than Rambouillets, while wool production was highest in purebred Rambouillet ewes followed by genotypes related closely to Rambouillets. In all trials crossbreds generally excelled purebreds in overall productivity; the degree of superiority depended on genotypes involved in the crosses. / Graduation date: 1991

Two experiments were conducted to determine whether in ewes uterine concentrations of estrogen and progesterone receptors are affected by the presence of a conceptus or by the hormonal milieu associated with extremes in photoperiod to which ewes are exposed. In Exp.1, nine mature ewes were unilaterally ovariectomized by removing an ovary bearing the corpus luteum (CL). The ipsilateral uterine horn was ligated at the external bifurcation and a portion of the anterior ipsilateral uterine horn was removed and assayed for endometrial nuclear and cytosolic concentrations of estrogen receptor (ER) and progesterone receptor (PR) by exchange assays. After a recovery estrous cycle, ewes were bred to a fertile ram. On day 18 of gestation a 10 ml jugular blood sample was collected for measurement of serum concentrations of estradiol -17β (E₂) and progesterone by radioimmunoassay. Ewes were relaparotomized on day 18 and the remaining uterine tissue was removed. Endometrium from both the pregnant and nonpregnant uterine horn was assayed for nuclear and cytosolic ER and PR concentrations. Nuclear and cytosolic ER concentrations on day 10 of the cycle were greater than in endometrium of gravid and nongravid uterine horns on day 18 of gestation (p<.01). Endometrial nuclear PR levels were also greater on day 10 of the cycle than in the pregnant (p<.05) and nonpregnant horn (p<.01) on day 18 of gestation. There were no differences in nuclear and cytosolic ER and PR concentrations between the pregnant and nonpregnant uterine horn on day 18. Serum levels of E₂ and progesterone on day 18 of gestation were 16.56 ± 2.43 pg/ml and 1.74 ± 0.57 ng/ml, respectively. These data suggest that duration of exposure of the uterus to progesterone and(or) the presence of the conceptus causes a reduction in uterine concentrations of ER and PR. Further, an effect of the conceptus, if any, is exerted via a systemic route. In Exp. 2, ten mature ewes were bilaterally ovariectomized in early October. During the onset of the winter solstice (late December), a 10 ml blood sample was collected from five ewes for analysis of serum levels of E₂ and progesterone. Ewes were then laparotomized and approximately one-third to one-half of a uterine horn was removed and assayed for endometrial nuclear and cytosolic ER. The contralateral horn was ligated at the external bifurcation and 10 μg of E₂ in 3 ml of physiological saline was injected into the uterine lumen of the ligated horn. After 48 h, a jugular blood sample was collected for steroid analysis and a section of the E₂ treated horn was removed and assayed for endometrial cytosolic and nuclear ER. This procedure was repeated on the remaining five ewes during the height of the summer solstice (late June). Endometrial nuclear and cytosolic concentrations of ER prior to and after exogenous E₂ stimulation were similar during the winter and summer solstice (p>.05). However, treatment with E₂ increased endometrial nuclear and cytosolic concentrations of ER compared with those of the nonstimulated uterine horn during the winter and summer solstice (p<.05 for each). Serum levels of E₂ prior to luminal treatment of ewes with E₂ during the winter and summer solstice did not differ (16.55 ± 4.05 vs 16.00 ± 3.0 pg/ml, respectively, p>.05). Serum levels of E₂ 48 h after administration of E₂ did not differ among ewes at the winter and summer solstice (18.75 ± 2.4 vs 18.65 ± 1.65 pg/ml, respectively, p>.05). Serum levels of progesterone were basal (<0.10 ng/ml) and did not differ in ewes prior to and after E₂ treatment at the winter and summer solstice (p>.05). These data indicate that physiological factors and(or) hormones such as prolactin and melatonin secreted in response to extremes in photoperiod do not appear to influence uterine concentrations of ER in ovariectomized ewes. / Graduation date: 1991

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 160 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 132-159).

Thesis (Ph. D.)--University of Wyoming, 2005. / Title from PDF title page (viewed on Nov. 14, 2007). Includes bibliographical references (p. 167-211).