Mechanisms Linking Metabolic Status and Disease with Reproductive Outcome in the Dairy Cow

Abstract

Contents Culling for infertility remains the main reason for disposal of dairy cows, limiting productive lifespan. In extreme cases, ovulation is inhibited, preventing the possibility of conception. More often cows do conceive, but fail to remain pregnant owing to intrinsic problems in the embryo and/or to a poor‐quality reproductive tract environment. Both aspects have a genetic component and are also influenced by management practices affecting nutrition and health. The relative importance of these factors varies among heifers, first‐lactation and older cows. A common theme, however, is that an internal signalling system exists which reduces fertility when the cow is in an unsuitable metabolic state to sustain a pregnancy. This may be directly related to nutrient shortage caused by inadequate feed intake, or because available nutrients are being prioritized towards growth or milk production, away from reproduction. Evidence is presented for the involvement of the somatotrophic axis (GH, IGF1, insulin, IGFBP2) and leptin as key metabolic signalling molecules. Another emerging theme is the interaction between metabolism and disease that affects the fertility. Common examples include (i) calf diseases causing inadequate heifer growth and increased age at first calving; (ii) poor peripartum energy status reducing the capacity of the uterus to involute and mount an effective immune response, thereby increasing the likelihood of endometritis; and (iii) development of mastitis after conception, a contributory factor to both early and late embryo mortality. Finally, recent evidence suggests that times of metabolic stress cause mitochondrial damage that also contributes to a reduction in longevity.

Endocrine and metabolic mechanisms linking postpartum glucose with early embryonic and foetal development in dairy cows

“…Perhaps the best-studied example of a metabolic imprint is for postpartum NEFA and its effect on composition of the oocyte and function of follicular cells Van Hoeck et al, 2011;Wathes, 2012). The possibility that there are permanent epigenetic modifications to the genome during the early postpartum period that affect long-term developmental competence of follicular cells has not been demonstrated at this time.…”

Ovarian, metabolic and endocrine indexes in dairy cows with different body condition scores

“…Nevertheless, the biochemical mechanisms and signs of BCS, as well as the association between BCS and endocrine or reproductive functions, have been insufficiently studied. Reproductive functions can be regulated by nutrients (Roche et al, 2009;Hernandez-Medrano et al, 2012) which, in turn, affect metabolic hormones (insulin, leptin), growth factors (insulin-like growth factor I, IGF-I and its binding proteins), GnRH/gonadotropins, steroid hormones, and response to these signalling molecules regulating ovarian folliculogenesis (Webb and Campbell, 2007;Sirotkin, 2011;Hernandez-Medrano et al, 2012;Wathes, 2012). On the other hand, no comparison of the concentrations of these substances in cows of different BCS has been performed previously.…”

“…time of oestrus onset, conception, pregnancy and embryo mortality rate (Silke et al, 2002;Roche et al, 2009) probably due to changes in the cell apoptosis rate (Wathes, 2012), ovarian follicular atresia (Pivko et al, 2012), and/or the risk of uterine disorders (Wathes et al, 2007;Roche et al, 2009;Wathes, 2012). A BCS either above or below the 2.75-3.25 range is associated with reduced fertility in both dairy and beef cows (Wathes et al, 2007;Crowe, 2008;Roche et al, 2009).…”

“…Several studies indicate that a negative energy balance in early lactation can also cause excessive mobilization of fatty acids in the cow's liver tissue. Such cows are less fertile, have significantly longer interval to calving, and a greater number of inseminations per conception compared with cows with moderate fattening (Reid and Collins, 1980;Jackson et al, 2011;Wathes, 2012).…”

“…Cows can be a good model to study the link between reproduction, endocrine system, metabolism, and body condition in females. For example, a negative energy balance in post-partum cows causes rapid body weight loss, increased occurrence of metabolic disorders, changes blood levels of glucose, insulin and IGF-I, which are important factors of ovarian functions (Spicer and Echternkamp, 1995;Zulu et al, 2002;Roche et al, 2009;Jackson et al, 2011;Kawashima et al, 2012;Wathes, 2012). A negative energy balance in such cows may restrict the pulsatile release of gonadotropin-releasing hormone, its downstream targets, gonadotropins (FSH and LH), responsiveness of ovarian tissue to gonadotropins and, therefore, adversely affect normal ovarian follicle development, causing follicle atresia (Butler, 2000;Wathes et al, 2007;Hernandez-Medrano et al, 2012).…”