In mammals, anti-Müllerian hormone (AMH) expression is detected in the granulosa cells of all growing follicles and is highest in healthy small antral follicles, which contribute most significantly to AMH endocrine levels. AMH is a reliable endocrine marker of this population of gonadotrophin-responsive follicles in ruminants and, over the longer term, plasma AMH concentrations are characteristic of individual animals. In the cow, plasma AMH concentrations follow specific dynamic profiles throughout the prepubertal period, the oestrous cycle and the change from gestation to the post partum period, with the alterations most likely reflecting numerical changes in the population of high AMH-producing follicles. In granulosa cells, bone morphogenetic proteins (BMP) enhance AMH gene expression and AMH synthesis, with these effects antagonised by FSH. BMP could both support follicular growth and contribute significantly to the induction and/or maintenance of AMH expression in small growing follicles. AMH expression decreases sharply in large follicles when they become oestrogenic, suggesting a role for FSH and/or oestradiol in these changes, but the underlying mechanisms remain hypothetical. A better understanding of the factors and mechanisms regulating AMH production is needed to propose new strategies for managing the reserve of primordial and small growing follicles, as well as for improving embryo production.

Docility tests were performed over 3 trait with four classes. Tests were performed by seven yr on 906 Limousin heifers sired by 34 males. The different handlers. The effects of handler, year, birth heifers were tested individually when they were 10 t o period, dam parity, birth region, husbandry system, 11 mo old in a pen with a handler who had 2 min to and sire were estimated. Handlers, birth period, lead the animal to a corner, keep it there for 30 husbandry system, and sire had significant effects. In consecutive seconds, and then to stroke it. Behaviors particular, animals that were managed indoors were of the animals were recorded and scores calculated. more docile than those reared out-of-doors at least The first score (docility score) was a continuous part of the time. Heritability estimates of the docility variable combining the greatest possible information. score ( .2 2) and docility criterion ( .l 8 ) seem sufficientThe second score (docility criterion) was a categorical to select for docility traits.

The aim of this study was to assess the potential consequences of selection for less aggressive or active animals during handling by estimating genetic correlations between different criteria of temperament and Limousin heifer breeding traits. Data consisted of the records collected from 1992 to 2004 at the progeny test station of Limousin AI sires. Six traits recorded during the same behavioural test – the so-called docility test – were considered to describe the heifer's temperament: aggressiveness against the handler, running time and number of escapes per minute of test period in presence or absence of the handler and a synthetic docility score accounting for the five previous components. Eight breeding traits were also considered simultaneously in the joint analysis with the five elementary temperament components: weights at 12 months and after calving (for measuring heifer growth), age at first observed oestrus (for measuring puberty) and fertility (for measuring heifer reproductive performance), calving ease score and pelvic opening (for measuring calving performance), maternal behaviour at calf's birth and milk yield (for measuring the suckling ability of the primiparous cow). REML (co)variance estimates were derived using linear multitrait sire models. Estimates of heritability were in the range of values given in the literature. Estimates of genetic correlation between temperament traits indicated that, genetically, aggressive animals also attempt to escape a lot. Consequently, their elimination will reduce both working risk and handling time for the breeder. Genetic correlations between temperament traits and breeding traits ranged from zero to favourable estimates and confirmed the very few results of the literature indicating a slight trend of less fearful heifers also being more productive, mainly because of a higher reproduction and calving performance, and, to a lesser extent, because of higher maternal abilities such as behaviour at calf's birth and milk yield.