Reproductive performance in the high-yielding dairy cow has severely decreased in the last 40 yr. The aim of this study was to compare the effectiveness of 4 nutritional strategies in improving the reproductive performance of high-yielding dairy cows. It was hypothesized that offering cows a high-starch ration in early lactation would enhance the onset of luteal activity, and that decreasing the severity of negative energy balance in the early postcalving period would improve reproductive parameters. Nutritional regimens aimed at improving fertility were applied to 96 Holstein-Friesian dairy animals. Upon calving, animals were allocated in a balanced manner to one of 4 dietary treatments. Primiparous animals were balanced according to live weight, body condition score and calving date. Multiparous animals were balanced according to parity, previous lactation milk yield, liveweight, body condition score and calving date. Treatment 1 was based on an industry best practice diet (control) to contain 170 g of crude protein/kg of dry matter. Treatment 2 was an individual cow feeding strategy, whereby the energy balance (EB) of individual animals was managed so as to achieve a predetermined target daily EB profile (±10 MJ/d). Treatment 3 was a high-starch/high-fat combination treatment, whereby an insulinogenic (high-starch) diet was offered in early lactation to encourage cyclicity and followed by a lipogenic (low-starch, high-fat) diet to promote embryo development. Treatment 4 was a low-protein diet, containing 140 g of crude protein/kg of dry matter, supplemented with protected methionine at an inclusion level of 40 g per animal per day. The nutritional strategies implemented in this study had no statistically significant effects on cow fertility measures, which included the onset of luteal activity, conception rate, in-calf rate, and the incidence of atypical cycles. The individual cow feeding strategy improved EB in early lactation but had no benefit on conception rate to first insemination. However, conception rate to second insemination, 100-d pregnancy rate (from the commencement of breeding), and overall pregnancy rate tended to be higher in this group. The high-starch/high-fat treatment tended to decrease the proportion of delayed ovulations and increase the proportion of animals cycling by d 50 postcalving. Animals that failed to conceive to first insemination had a significantly longer luteal phase in the first cycle postpartum and a longer inter-ovulatory interval in the second cycle postpartum. With regards to estrous behavior, results indicate that as the size of the sexually active group increased, the intensity of estrus and the expression of mounting or attempting to mount another cow also increased. Furthermore, cows that became pregnant displayed more intense estrous behavior than cows that failed to become pregnant.

Improving the sustainability and overall longevity and health of modern Holstein Friesian (HF) dairy cattle is essential in order to maintain overall farm profitability. Prolonged negative energy balance in early lactation can result in metabolic stress, as well as long term problems with fertility (Pryce et al., 2004). In addition, maximising the efficiency of nitrogen (N) utilisation by strategies such as reducing the crude protein content of the diet is of crucial importance in minimising the environmental impact of dairying. The aim of this study was to evaluate the effect of a range of nutritional strategies on milk production, energy balance and efficiency of N use in early lactation.

IntroductionThe cost of replacing cows that are culled due to reproductive failure is approximately £18,000 per 100 cow herd per year. It is estimated that fertilisation rates following artificial insemination are >90% (Diskin et al., 2006) and yet calving rate to a single insemination is in the order of 31% (Law et al., 2009). The majority of this reproductive wastage occurs between insemination and maternal recognition of pregnancy, approximately 16 days after ovulation, with relatively little late embryonic/foetal mortality. The objective of this study was to quantify reproductive wastage prior to day 7 post insemination and to evaluate energetic, metabolic and hormonal effects in early lactation (day 0-42) on embryonic loss.

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La position et la forme de la queue ont 6t£ mesuroes sur 253 photographies de 84 babouins doguera (Papio anubis), identifiables individuellement, dans des situations nonsociales ou neutres. D'annie en annee la position du segment proximal de la queue des babouins est plus verticale. La difference moyenne d'angle est d'environ 3° par an pour les males et de 5° par an pour les femelles.Plusieurs caractoristiques de la forme de la queue changent aussi en fonction de Tage. Les modifications de maintien de la queue des babouins doguera en fonction de Tage sont dans l'ensemble semblables celles que Γόη observe chez les babouins jaunes (P. cynocephalus). Dans les deux especes, le maintien neutre de la queue chez les adultes est sans relation avec la domination de rang hidrarchique.Ces otudes fournissent une base d'estimation de Tage des individus dans une population sauvage et un point de depart pour l'analyse des communications sociales.