A mutagenized clone of Rift Valley fever virus (RVFV; MV P12) used in inoculation of 3 pregnant ewes was immunogenic, nonpathogenic, and nonabortogenic. In contrast, inoculation of a matched group of 3 pregnant ewes with parent RVFV induced clinical disease and abortions. Ewes given MV P12 delivered healthy lambs that had RVFV antibody titers of less than 1:10 at birth, increasing to greater th...

If ewes consumed a high-salt diet or saltbush during the last 3 months of pregnancy and for 3 weeks after birth, we expected the renin activity of their lamb to be suppressed at birth and at 3 weeks of age. We also expected an increase in the concentration of cations other than sodium in the ewe's milk and an increase in the plasma Na concentration of the lamb at birth. To test these hypotheses...

The aim of this study was to determine whether endogenous progesterone regulates synthesis and secretion of luteal oxytocin. In Expt 1, mature ewes (n = 5 per group) were assigned randomly to control or mifepristone (RU486) treatment groups. Ewes were injected s.c. twice a day with vehicle or 10 mg RU486 on days 5-7 of the oestrous cycle (oestrus = day 0). On day 8, after an i.v. injection with...

The objective of this experiment was to determine whether passive immunization against a synthetic inhibin-like peptide (alpha-IF) increases FSH secretion and reproductive performance of ewes bred in the spring. Crossbred ewes were assigned to three treatment groups of 10 ewes each. Progesterone-releasing pessaries (CIDR-G) were inserted and left in place for 12 d. The CIDR-G were removed on Ap...

Reproductive performance of four, five and six-year old crossbred ewes representing six combinations ofFinnsheep (F), Dorset (D), Rambouillet (R), and White Face Western (WFW) breeding were evaluated when lambing in the winter (February-March, 1977) and in the fall (October-November, 1977). The six breed combinations represented were 3fsF, 5fsWFW; %F, 1f2D, %R; %F, %D, 1f2R; %F, %R; 1f2D, 1f2R;...

The objective of the study was twofold: (i) to quantify the differences in daily milk yield (DMY) and total milk yield (TMY) between lame and non-lame dairy ewes and (ii) to determine the shape of lactation curves around the lameness incident. The overall study was a prospective study of lameness for the surveyed sheep population, with a nested study including the selection of matching controls...

Activation of the hypothalamo-pituitary-adrenal (HPA) axis by psychosocial stress is attenuated during lactation. We tested the hypothesis that lactating ewes will have attenuated HPA axis responses to isolation and restraint but will have greater responses to predator stress in the form of barking dogs. We imposed two 4 h stressors: psychosocial stress (isolation and restraint of ewes) and pre...

Ile-de-France ewes had high plasma progesterone concentrations during early summer-late winter. Gentile-di-Puglia ewes had high progesterone values during the winter-spring-summer period but during autumn progesterone values were very low and oestrous behaviour was not displayed. The comparison with Ile-de-France ewes indicates that a phase shift occurs in the annual ovarian activity in ewes of...

The objective of this study was to determine the effects of selenium (Se) supplementation of mature ewes in the period from day -14 to day 90 post mating on Se status, productivity and viability of ewes and their offspring. Multiparous crossbred ewes (n = 82) were randomly assigned to receive a standard dried grass-based diet (control) or dried grass diet supplemented with 1 g of selenised yeas...

Shearing ewes in mid pregnancy can provide farmers with management and financial advantages. Six experiments conducted at Massey University have collectively shown that shearing ewes at this time can increase lamb birthweight by up to 1.0 kg. When comparisons were made across studies, there was a strong negative relationship between size of the response and the birthweight of control lambs (tho...