Two experiments were conducted to examine the effect of a cyclopropenoid fatty acid on luteal cell function. In Exp. 1, 12 mature ewes were mated to a fertile ram, assigned to two groups (n = 6/group) and laparotomized on day 18 of gestation. Ewes with corpora lutea (CL) in both ovaries were unilaterally ovariectomized while ewes with a CL in one ovary only were allowed to remain intact. An extract of Sterculia foetida seeds (1.09 mg), consisting of a mixture of fatty acid methyl esters including 750 ug of sterculic acid (SA), or 1.09 mg oleic acid methyl ester (OA) was injected into the artery supplying the ovary bearing CL. Jugular blood was collected on day 18 before surgery and daily thereafter until day 30 of gestation or until detected estrus, whichever occurred first. Sera were assayed for progesterone (P₄) by radioimmunoassay. In Exp. 2, 12 mature ewes were laparotomized on day 10 of the estrous cycle and CL were removed, weighed and sliced for incubation. Corpora lutea from two ewes were pooled for each incubation. Slices of CL were preincubated in medium containing 145 ng/ml of S. foetida extract (100 ng/ml sterculic acid methyl ester) or 145 ng/ml oleic acid methyl ester (control) for 90 min. Then, slices of tissue were washed and reincubated in fresh medium containing 25 ug 22(R)- hydroxycholesterol/ml (0.079 nM final concentration) or 25 ug 5-pregnen-3βol-20-one/m1 (0.084 nM final concentration) for 120 min. Tissue plus medium were analyzed for P₄. Injection of SA or OA on day 18 of gestation caused a reduction in serum concentrations of P4 within 24 h, after which concentrations of steroid remained low and relatively constant in control and those SA-treated ewes that remained pregnant until day 30 of gestation. Three of six ewes that were injected with SA exhibited estrus within 3 to 5 days after treatment. Serum concentrations of P₄ of SA-treated ewes differed from those of OA-injected control ewes (P<0.01). Luteal tissue subjected to SA or OA in vitro did not differ in ability to synthesize P₄ during subsequent incubation in the absence of precursor substrate (incubated controls). Relative to respective incubated controls, P₄ synthesis by tissue previously exposed to SA or OA was not altered by incubation in the presence of 22(R)-hydroxycholesterol. Presence of 5-pregnen-3βol-20-one (pregnenolone) in the medium significantly increased P₄ synthesis by luteal tissue preincubated with SA or OA compared with that of controls. However, response of SA-treated tissue was markedly less than that of tissue exposed to OA (P<0.05). Results of this study suggest that $A can cause regression of CL in 50% of pregnant ewes. Apparently, the luteolytic effect of SA may be caused by its ability to interfere in the conversion of pregnenolone to P₄ by 3β- hydroxysteroid dehydrogenase. / Graduation date: 1991

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains vii, 72 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 58-71).

A series of trials was conducted with Polypay (P), Coopworth (CP), Hampshire (H), and crossbred ewes over a two year period at three locations to assess the effects of ewe body condition and pre-lambing supplementation on ewe productivity. Supplementation trials were conducted at all three locations in Year 1 using P (OSU), CP (Farm 1), and crossbred ewes (Farm 2), and at OSU in Year 2 using P ewes. Supplementation consisted of one pound of whole corn daily in addition to the routine ration being fed to the controls. Supplementation began four weeks prior to lambing and continued to parturition. Body condition trials were conducted concurrently at OSU using CP, H, and crossbred ewes in the first year and CP ewes in the second year. A body condition trial was also conducted at Farm 1 (CP ewes) in the second year. At OSU, Polypay ewes were mated to CP, P, and H rams, CP ewes were mated to CP and H rams, and H ewes were mated to H rams. On the commercial farms, CP ewes (Farm 1) were mated to CP rams, and crossbred ewes (Farm 2) were mated to Suffolk rams. Ewes in supplementation trials were condition scored on a five point scale(1=very thin; 5=very fat)at the time of allocation to treatments six weeks pre-lambing, and ewes in all trials were scored one week prior to lambing. In addition, in Year 2 P and CP ewes at OSU were scored and weighed at mating, post-mating, mid-gestation, pre-lambing, and weaning. Production traits recorded included litter size at birth, total weight of lamb born (TWB), lamb survival, and individual lamb weaning weights (WWT). The various components were combined to calculate total weight of lamb weaned (TWW) by each ewe as the measure of total lamb production. In most trials, higher ewe body condition score pre-lambing (CSL) was associated with heavier TWW. The heavier TWW was the result of both increased lamb survival and heavier individual lamb WWT. Supplementation increased both CSL and subsequent TWW; the increase in TWW was accounted for entirely through improved CSL. The response to supplementation was not consistent over ewe genotypes; crossbred ewes showed a greater increase in CSL than purebred ewes, and likewise a greater response in TWW. While supplementation increased ewe productivity, a comparison of control vs supplemented ewes which were at the same body condition prelambing (CSL = 3.0) indicated that ewes which were previously thin did not perform as well as ewes which had been maintained in good condition throughout gestation. While supplementation raised their CSL to the same level, their lambs exhibited both lower survival and lighter WWT. Comparison of the expense of supplementation with the increased TWW indicated a feed cost of about $.30 per extra pound of lamb weaned. At typical lamb market prices of $.60/lb, identification and supplementation of thin ewes pre-lambing would be a profitable management strategy for sheep producers. / Graduation date: 1994

Thesis (M. Ag. Sci) -- University of Adelaide, 1965. / [Typescript]. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 76-83). Also available via the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 56-64).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Two trial were conducted to determine the possible effects of season, protein supplementation, age and birth status on the reproduction rate (ovulation rate and rate of twinning) of ewes. In Trial 1 the weight, age and birth status if ewes were recorded. 144 ewes were randomly allocated in two treatment groups (urea and mix protein group) synchronised, mated and the number of corpora lutea, foetuses observed, lambs born per ewe and the mass of the ewe after lambing were also recorded. Lambing status or the 1-year-old (0.993 ± 0.316) and 2-year-old (1.233 ± 0.134) ewes were lower (p < 0.05) than that of the 6- year-old ewes (1.897 ± 0.248). The lambing status and the number of corpora lutea of the single born ewes (1.179 ± 0.131; 1.274 ± 0.138) were lower (p < 0.0001) than that of the twin born ewes (1.614 ± 0.139; 1.782 ± 0.147), within the urea treatment. In Trial 2, 75 ewes were randomly allocated in four treatment groups (raw lupins, cooked lupins, cottonseed oil-cake and Fescue grass), synchronised and the number of corpora lutea were recorded. The weight, age and birth status of the ewes were also recorded. The number of corpora lutea from the cooked lupin group (1.815 ± 0.184) was significantly higher than that from the cottonseed oilcake group (1.048 ± 0.209), within the twin born ewe group. It was concluded that season, protein supplementation, age and birth status influenced the reproduction rate of ewes. Copyright / Dissertation (Msc)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted