Search

Concentrations of plasma progesterone, Ca, Mg and Zn were monitored from oestrus synchronization to weaning in 38 indigenous female breeding goats showing cyclical changes in ovarian activity. Goats were synchronised with intra-vaginal sponges containing 30 mg fluorogestone acetate. Ca, Mg and Zn concentrations in plasma increased as gestation progressed and dropped after kidding. A high level of progesterone concentration in plasma was maintained during pregnancy, reaching a peak prior to parturition and dropping to basal levels at kidding. There was a negative correlation (r = −0.95) between blood plasma Ca and Mg, a positive correlation (r = 0.68) between blood plasma Ca and Zn concentration and a negative correlation (r = −0.57) between blood plasma Mg and Zn concentration during the dry period. Blood progesterone concentration was positively (r = 0.59) and negatively (r = −0.59) correlated to Mg concentration during gestation and lactation periods, respectively. Progesterone was negatively correlated (r = −0.47) to Ca, positively correlated (r = 0.59) to Mg and negatively (r = −0.67) correlated to Zn during the dry period. Results suggest variations in plasma progesterone, Ca, Mg and Zn concentrations in breeding does as the physiological state of the animal changes.

Length of oestrus and timing of the LH surge was measured in six British White does, housed with a vasectomized buck (experiment 1). The following breeding season, pulsatile LH release during the cycle was measured in eight does and the pattern of behavioural and vaginal traits in relation to onset of oestrus (time 0) determined (experiment 2). In experiment 1, the interval to first oestrus after introduction of the buck on 1st October was 10.3 +/- 3.0 days (n = 6) but in experiment 2, when the buck was put in on 1st September, first oestrus occurred after 39.3 +/- 3.4 days in 7/8 does and 7 days in 1/8 does indicating that adequate exposure to short days is needed before the buck can initiate ovarian activity. LH pulse frequency increased from 0-1 pulses/8 h to 3 pulses/8 h after luteolysis, with no change in pulse amplitude, suggesting that progesterone regulates LH pulse frequency. Mean LH values rose from basal to 102.1 +/- 7.8 ng/ml, 12 +/- 1.5 h after the onset of oestrus, which was 16.3 +/- 1.7 h in length. Does sought out the buck and displayed tail wagging, bleating and restlessness from -60 h to +36 h relative to the onset of oestrus (time 0). The incidence of these activities rose at -12 h and peaked at 0 h. Tail wagging, but not bleating or restlessness, also increased in intensity at 0 h, as did the intensity with which the doe actively sought out the buck. Vulval redness and swelling and onset of a clear thin vaginal discharge were first observed 1-2 days before oestrus, becoming maximal on day 0. It was concluded that onset of frequent tail wagging was the most useful trait for detecting onset of oestrus.

Ten Boran ( Bos indicus ) cows were studied over 64 oestrous cycles. Alterations in sexual behaviour and of the ovaries palpated per rectum were related to the plasma progesterone profiles detemined using an extracted double antibody radioimmunoassay. The mean cycle length in the cows was 23 ± 0 · 4 days. Oestrus detection efficiency using standing to be mounted, was 27 percent. Restlessness, where observed, reliably indicated that a cow was in the period of basal progesterone concentration. Mounting, sniffing, head-butting, being sniffed, being mounted with avoidance behaviour, although shown by 50 percent of cows during the basal progesterone period were not confined solely to this part of the cycle. Use of Kamar heat-mount detectors in conjunction with standing to be mounted identified 44 percent of oestrous animals. However, the occurrence of false positives during the rest of the cycle precluded their use as sole indicators of oestrus. Accuracy of palpation of corpora lutea was 61 percent during periods of elevated and 98 percent in periods of basal progesterone concentrations.

A group of 12 first-calved Boran cows was infected with Trypanosoma congolense transmitted by Glossina morsitans centralis and another 10 uninfected cows kept as controls. Routine monitoring of oestrous behaviour, palpation of the ovaries per rectum and determination of plasma progesterone profiles was carried out until day 180 post-infection to assess the cyclical status of each animal. Two cows died of trypanosomiasis on days 51 and 54 post-infection. The remaining cows were divided into two groups. Group A (five infected and five controls), which showed the most severe clinical symptoms, was selected for treatment around day 60 and given a curative dose of diminazene aceturate (Berenil). Group B (five infected and five controls) was treated on day 90. Control cows remained cyclic throughout the study, and were unaffected by Berenil treatment. Infected cows became severely anaemic and lost weight and body condition. On day 60 post-infection, five infected cows were acyclic (two in group A; three in group B), three had a persistent corpus luteum (two in group A; one in group B) and one cow from each group was still cyclic. Shortly after day 60, the cow in group B with a persistent corpus luteum had also become acyclic, leaving only one cow which continued to cycle throughout the study. This cow lost the least amount of weight over the infection period and showed the least severe clinical symptoms. Cows which stopped cycling lost between 8 and 21% of their initial body weights post-infection. Animals resumed cyclical ovarian activity within 21–73 days of receiving Berenil treatment. Within cows, onset of cyclicity did not appear to be affected by the severity or duration of the previous infection period (60 versus 90 days) and occurred before the cows had gained weight appreciably. Infected drug-treated cows had a higher number of short cycles (< 19 days) and cycles with low mean luteal concentrations of progesterone (< 2.6 ng/ml) compared to the control cows. Transient rises in plasma progesterone were also seen before the first post-treatment cycle. There was no difference in the oestrous detection rate between infected, drug-treated cows and control cows (55 versus 44%).