Pregnancy is characterized by increased plasma adrenocorticotropic hormone (ACTH) and cortisol. Studies suggest that progesterone acts as an antagonist at mineralocorticoid receptors. Therefore, we tested the hypothesis that chronic progesterone, produced by treatment of nonpregnant ewes or during pregnancy, will result in increased plasma ACTH relative to the plasma cortisol concentrations. We...

The effect of level of dietary energy and protein intake on reproductive performance was studied in 110 Finn-cross ewe lambs and in 404 Finn-cross yearling ewes during late gestation. Nitrogen metabolism was studied in 26 ewe lambs and 23 yearling ewes. Increasing digestible energy and crude protein intake for ewe lambs and yearling ewes during late gestation increased (P<.05) ewe average daily...

Two commercially available progestogen products for cattle, melengestrol acetate (MGA) and norgestomet (SMB), were evaluated for their ability to induce synchronized estrus in anovulatory ewes. Seasonally anestrous ewes (n = 232) were randomly assigned to one of seven treatments: 1) control (C); 2) MGA only (OMGA; .3 mg of MGA/d); 3) MGA+zeranol (RMGA; 2.5 mg of zeranol); 4) MGA+PG-600 (PMGA; 4...

These studies test the hypothesis that pregnancy alters the feedback effects of cortisol on stimulated ACTH secretion. Ewes were sham-operated (Sham), or adrenalectomized (ADX) at approximately 108 days gestation and replaced with aldosterone (3 microg x kg(-1) x day(-1)) and with cortisol at either of two doses (ADX + 0.6 and ADX + 1 mg x kg(-1) x day(-1)); ewes were studied during pregnancy a...

These studies test the hypothesis that the increased adrenocorticotropic hormone (ACTH) and cortisol in pregnancy reflect a reset of regulated plasma cortisol concentrations. Ewes were sham operated (Sham) or adrenalectomized (ADX) at ∼108 days gestation. Adrenalectomized ewes were replaced with aldosterone (3 μg ⋅ kg-1 ⋅ day-1) and with cortisol at either of two doses (ADX + 0.6 and ADX + 1.0 ...

During the last trimester of pregnancy single and twin-bearing ewes were fed chopped oat hay ad libitum and supplements (300 g/day) of cottonseed meal (CSM) (T1) or barley grain plus urea and sodium sulfate (Bar+N+S) (T2), or CSM and oat hay restricted to the level consumed by the T2 ewes (T3). T1 ewes consumed 47% more hay and approximately 13% more digestible organic matter than T2 ewes. T1 e...

Thirty-nine multiparous ewes (19 Pelibuey and 20 Romanov × Pelibuey) treated with fluorogestone acetate impregnated intravaginal sponges were used to evaluate the effects of low pregnant mare serum gonadotropin (PMSG) doses and genotype on their reproductive efficiency under heat stress conditions. The sponge treatment lasted for 12 days, and 24 h before sponge removal, ewes of each genotype we...

St. Croix White hair sheep ewes were used to evaluate the effect of supplemental nutrition prior to breeding during the dry and wet seasons on St. Croix. Beginning 21 d prior to breeding ewes were fed supplement in addition to grazing guineagrass pasture (FEED). Other ewes in the flock grazed pasture only (CONTROL). This study was conducted during the dry (June and July) and wet seasons (Octobe...

In order to study the effects of sheep teat disorders on the protection of the mammary gland, we used a Mannheimia haemolytica isolate, which did not cause clinical mastitis when deposited into intact teats. In the first experiment, this was deposited into the duct of teats with orf (Group A, n=5) or papilloma (Group B, n=3). In the second, teats were chapped and then, the organism was deposite...

By using continuous infusions of 3H- and 14C-labelled substrates, three-pool models, incorporating rumen propionate, plasma glucose and blood carbon dioxide were constructed to determine the contribution of propionate to glucose in non-pregnant, pregnant (mid and late) and lactating hill ewes. Although the intakes of non-pregnant and pregnant ewes were the same (1200 g dried grass/d) and result...