Within breeds and other captive populations, the risk of high inbreeding rates and loss of diversity can be high within (small) herds or subpopulations. When exchange of animals between different subpopulations is organised according to a rotational mating scheme, inbreeding rates can be restricted. Two such schemes, a breeding circle and a maximum avoidance of inbreeding scheme, are compared. In a breeding circle, flocks are organised in a circle where each flock serves as a donor flock for another flock, and the same donor-recipient combination is used in each breeding season. In the maximum inbreeding avoidance scheme, donor-recipient combinations change each year so that the use of the same combination is postponed as long as possible. Data from the Kempisch Heideschaap were used with computer simulations to determine the long-term effects of different breeding schemes. Without exchanging rams between flocks, high inbreeding rates (.1.5% per year) occurred. Both rotational mating schemes reduced inbreeding rates to on average 0.16% per year and variation across flocks in inbreeding rates, caused by differences in flock size, almost disappeared. Inbreeding rates with maximum inbreeding avoidance were more variable than with a breeding circle. Moreover, a breeding circle is easier to implement and operate. Breeding circles are thus efficient and flexible and can also be efficient for other captive populations, such as zoo populations of endangered wild species.

The Dutch scrapie eradication programme aims at the exclusive use of homozygous ARR/ARR breeding rams by the end of 2004. As a consequence, breeds with a small population size and a low frequency of the ARR allele may suffer unacceptable losses of genetic diversity and high inbreeding levels. We simulated three breeding strategies to assess their efficacy in eliminating scrapie sensitive alleles and their effect on inbreeding levels. Under mild selection, both homozygous and heterozygous ARR rams were used indiscriminately. Under moderate selection, homozygous ARR rams were used preferably but they were supplemented with heterozygous rams when necessary. Under severe selection, only homozygous rams were used. Severe selection mimics then the proposed eradication programme. Simulations were carried out with allelic frequencies and population parameters of existent rare breeds in The Netherlands. With severe selection all simulated breeds showed unacceptably high inbreeding rates (> 0·5% per year). For some breeds, moderate selection resulted in acceptable inbreeding rates, while for other breeds only mild selection resulted in acceptable rates. The frequency of the ARR allele after 5 years of selection was only slightly lower with moderate selection than with severe selection (0·8% lower on average), but it was clearly lower with mild selection. Based on these simulations, we propose a selection programme where with low frequencies of the ARR allele, mild selection is used initially. Once the ARR frequencies rise to a particular value, the switch can be made to moderate selection. The population size (e.g. below 750, 750 to 3750 and above 3750 ewes) determines the frequency of the ARR allele at which the switch can be made (33%, 25% and 10%, respectively). With even higher ARR frequencies (above 70%, 50% and 33%, respectively) the regime can be changed to severe selection.

The expression of oestrous behaviour in Holstein Friesian dairy cows has progressively decreased over the past 50 years. Reduced oestrus expression is one of the factors contributing to the current suboptimal reproductive efficiency in dairy farming. Variation between and within cows in the expression of oestrous behaviour is associated with variation in peripheral blood oestradiol concentrations during oestrus. In addition, there is evidence for a priming role of progesterone for the full display of oestrous behaviour. A higher rate of metabolic clearance of ovarian steroids could be one of the factors leading to lower peripheral blood concentrations of oestradiol and progesterone in high-producing dairy cows. Oestradiol acts on the brain by genomic, non-genomic and growth factor-dependent mechanisms. A firm base of understanding of the ovarian steroid-driven central genomic regulation of female sexual behaviour has been obtained from studies on rodents. These studies have resulted in the definition of five modules of oestradiol-activated genes in the brain, referred to as the GAPPS modules. In a recent series of studies, gene expression in the anterior pituitary and four brain areas (amygdala, hippocampus, dorsal hypothalamus and ventral hypothalamus) in oestrous and luteal phase cows, respectively, has been measured, and the relation with oestrous behaviour of these cows was analysed. These studies identified a number of genes of which the expression was associated with the intensity of oestrous behaviour. These genes could be grouped according to the GAPPS modules, suggesting close similarity of the regulation of oestrous behaviour in cows and female sexual behaviour in rodents. A better understanding of the central genomic regulation of the expression of oestrous behaviour in dairy cows may in due time contribute to improved (genomic) selection strategies for appropriate oestrus expression in high-producing dairy cows.Keywords: sexual behaviour, dairy cow, oestrus, gene expression, brain ImplicationsReduced oestrus expression is one of the factors contributing to the current suboptimal reproductive efficiency in dairy cows. A recent series of publications that correlated the level of oestrous behaviour expression to gene expression levels in the cow brain and anterior pituitary are reviewed here and their findings placed in perspective of what is known about sexual behaviour from studies on other species. The improved understanding of the central genomic regulation of oestrous behaviour expression may in due time contribute to improved (genomic) selection strategies for appropriate oestrus expression in high-producing dairy cows. IntroductionMaintaining good fertility and thereby optimum reproductive performance in dairy cows is of great economic importance for the dairy industry. Artificial insemination of cows is widely practiced in modern dairy farming. To ensure timely insemination and thereby maximize conception rates in the herd and profitability of the farm, it is important that the farmer does not m...

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