In order to overcome the refractory period of the corpus luteum to prostaglandin (day 15 of the cycle through oestrus to day 3 of the next cycle), two injections each consisting of either 31,25 μg; 62,5 μg; 125 μg or…
The effects of oestrogen priming and GnRH administration on the release of LH and on luteal function were investigated using 66 spring-lambing S.A. Mutton Merino ewes in early lactation. Seven randomly selected groups of ewes received either (i) 30 μg…
Progesterone and total unconjugated oestrogen concentrations in the peripheral blood of 4 Afrikaner cows during late gestation and parturition were determined by RIA. From l2-18 days prepartum, progerone levels ranged .from 8.4 to 13,0 ng/ml and subsequently declined to 3,7-8,2…
Following parturition blood samples were collected daily from 5 mature lactating cows until the first post partum oestrous period. Plasma progesterone concentration as determined by RIA was applied to evaluate post partum ovarian activity. Parturition to first oestrus varied from…
Post-partum plasma progesterone concentrations and luteal progesterone content were measured in lactating and non-lactating ewes during a normal breeding season in autumn and an abnormal breeding season in spring. The results indicate that silent ovulations during the autumn breeding season…
Plasma LH and progesterone levels were measured daily from the sixth to the fifteenth day of the oestrous cycle in Friesland cows during December (summer) of one year, and April/May (autumn), June/July (winter) and September (spring) of the following year.…
The administration of different doses (62,5; 125 or 250 μg per injection) of a prostaglandin analogue (cloprostenol) 14 days apart (in the double injection regime), proved that oestrus can be synchronized very efficiently in the Boer…
Forty-five SA Mutton Merino ewes, 2 to 5 years of age, were divided into three groups. Although all ewes received the same basic diet, the diet of one group (group M) was supplemented with molybdenum and that of another group…
Mechanisms that have been proposed to account for (i) premature regression or (ii) subnormal secretory activity of corpora lutea (CL) in cows or in ewes are reviewed. Processes which occur prior to, at the time of, or following, ovulation are…
Numerous studies have shown that in the acyclic ewe, the fIrst corpus luteum (CL) after administering gonadotropin releasing hormone (GnRH) will lead to inadequate progesterone (P4) concentrations or will be short-lived. An attempt was made to promote the function…
The use of the CIDR (controlled internal drug release) dispenser as a progestagen-synchronizing agent was evaluated in 37 Karakul ewes during the breeding season, using the intravaginal progestagen sponge as a control (30 ewes). Although there was no significant differences…
An investigation was conducted into the effects of two phenolic amines, N -methyl-β-phenethylamine (NMP) and tyramine (T) on corpus luteum function and reproductive performance of Angora goats. Both compounds are widely distributed through the plant kingdom and, because of their…
