The sexual motivation of boars housed adjacent to ovariectomised gilts did not affect the efficiency of detecting hormonally induced oestrus using the back pressure test

This study tested the hypothesis that the efficiency of detecting oestrus in gilts, using the back pressure test (BPT), will be reduced when gilts are housed adjacent to a boar of high sexual motivation compared to when gilts are housed adjacent to a boar of low sexual motivation. The experiment was a 2 x 2 Latin square design with three replicates. Boars of high and low sexual motivation were selected on the basis of the total number of copulations and the mean reaction time to first mount during three mating tests. Twelve boars were observed in mating tests and the three highest and lowest ranking boars were assigned to three palm, each pair containing a boar of high and a boar of low sexual motivation. One pair was used in each replicate. In each replicate, two groups of six ovariectomised gilts were housed for 14 days, commencing 7 days prior to hormonally induced destrus, adjacent to a boar of either high or low sexual motivation. All gilts were checked twice daily for oestrus using the BPT. In the first replicate, the level of proceptive behaviour of the gilts was quantified immediately after checking for oestrus in a 3-rain test in which the amount of time that the gilts spent within 0.5 m of a pen containing a sexually mature boar was recorded. There were no effects of housing gilts adjacent to boars of high or low sexual motivation on the percentage of gilts detected in oestrus, the percentage of gilts detected in oestrus for more than I day, the duration of oestrus or the level of proceptive behaviour of gilts. These data suggest that the level of sexual motivation of boars does not influence the efficiency of detecting hormonally induced oestrus, using the BPT, in ovariectomised gilts housed adjacent to boars.

The effect of repeated boar exposure on cortisol secretion and reproduction in gilts

It has been proposed that short-term activation of the hypothalamo-pituitary adrenal axis, with a consequent increase in the secretion of cortisol, amy disrupt the endocrine events prior to ovulation and thereby impair reproduction in females. We investigated this concept in gilts in which oestrus was detected by introduction to boars, where intense physical contact is possible, or by applying pressure to the back of gilts (back-pressure test) during fence-line exposure to boars, where intense physical contact is prohibited. We expected that there would be a greater release of cortisol and that reproduction would be inhibited in gilts introduced to boars compared to gilts in which the back-pressure test was used. As expected, introduction of gilts to boars resulted in a significant transient increase in plasma concentrations of cortisol while there was no significant effect of using the back-pressure test on plasma cortisol. Nevertheless, introduction of gilts to boars did not impair reproduction and there was no effect of method of detecting oestrus on duration of oestrus, sexual receptivity, fertility or fecundity. The length of the oestrous cycle was decreased and ovulation rate increased in gilts that were introduced to boars compared to gilts that underwent the back-pressure test, indicating that introduction of gilts to boars may have stimulated these aspects of reproduction. These stimulatory effects may have been due to an increased exposure of gilts to sexual behaviour and stimuli from boars when introduced to boars and/or to stimulatory effects of the hypothalamo-pituitary adrenal axis on some aspects of reproduction.

Progesterone and testosterone in combination act in the hypothalamus of castrated rams to regulate the secretion of LH

We tested the hypotheses that progesterone enhances the negative feedback actions of testosterone in rams and that this occurs through actions at the hypothalamus. In the first part of this study, blood samples were collected every 10 min for 12 h before and after 7 days of treatment (i.m.) of castrated Romney Marsh rams (n=5 per group) with vehicle, progesterone (4 mg/12 h), testosterone (4 mg/12 h) or a combination of progesterone (4 mg/12 h) and testosterone (4 mg/12 h). In the second part of this study the brains of four gonad-intact Romney Marsh rams were collected, the hypothalamus was sectioned and in situ hybridisation of mRNA for progesterone receptors conducted. After 7 days of treatment with vehicle or progesterone or testosterone alone, there were no changes in the secretion of LH. In contrast, treatment with a combination of progesterone and testosterone resulted in a significant (P<0.01, repeated measures ANOVA) decrease in mean plasma concentrations of LH, the number of LH pulses per hour and the pre-LH pulse nadir and a significant (P<0.01) increase in the inter-LH pulse interval. We found cells containing mRNA for progesterone receptors throughout the hypothalamus, including the preoptic area (where most GnRH neurons are located in sheep), the periventricular, ventromedial and arcuate nuclei and the bed nucleus of the stria terminalis. This study shows that progesterone is capable of acting centrally with testosterone to suppress the secretion of LH in castrated rams and that cells containing mRNA for progesterone receptors are located in the hypothalamus of rams in the vicinity of GnRH neurons.

Monitoring the ungulate prey of the Komodo dragon Varanus komodoensis: distance sampling or faecal counts?

Monitoring the abundances of prey is important for informing the management of threatened and endangered predators. We evaluated the usefulness of faecal counts and distance sampling for monitoring the abundances of rusa deer Rusa timorensis, feral pig Sus scrofa and water buffalo Bubalus bubalis, the three key prey of the Komodo dragon Varanus komodoensis, at 11 sites on five islands in and around Komodo National Park, eastern Indonesia. We used species-specific global detection functions and cluster sizes (i.e. multiple covariates distance sampling) to estimate densities of rusa deer and feral pig, but there were too few observations to estimate densities of water buffalo. Rusa deer densities varied from from 2.5 to 165.5 deer/km2 with coefficients of variation (CVs) of 15-105%. Feral pig densities varied from 0.0 to 25.2 pigs/km 2 with CVs of 25-106%. There was a positive relationship between estimated faecal densities and estimated population densities for both rusa deer and feral pig: the form of the relationship was non-linear for rusa deer, but there was similar support for linear and non-linear relationships for feral pig. We found that faecal counts were more useful when ungulate densities were too low to estimate densities with distance sampling. Faecal count methods were also easier for field staff to conduct than distance sampling. Because spatial and temporal variation in ungulate density is likely to influence the population dynamics of the Komodo dragon, we recommend that annual monitoring of ungulates in and around Komodo National Park be undertaken using distance sampling and faecal counts. The relationships reported here will also be useful for managers establishing monitoring programmes for feral pig, rusa deer and water buffalo elsewhere in their native and exotic ranges.