Ovarian, metabolic and endocrine indexes in dairy cows with different body condition scores
Journal Title: Journal of Animal and Feed Sciences - Year 2013, Vol 22, Issue 4
Abstract
Body condition can influence bovine fertility, but the morphological, biochemical and endocrine mechanisms of this influence are not fully understood. The aim of the study was to examine the interrelationships between cow body condition, morphological and endocrine state of the ovary, and blood metabolic indexes. Czech Fleckvieh dairy cows at the follicular phase of the ovarian cycle and with a tendency towards emaciation (body condition scoreCS2) and cows with an average body condition score (BCS3) were compared. Plasma concentrations of aspartate aminotransferase (AST), non-esterified fatty acids (NEFAs), Ca2+, inorganic phosphorus (Pi ), Mg2+, Fe2+, Cu2+, Zn2+ (determined using photometrically), leptin and insulin (ELISA), ovarian area, number of visible ovarian follicles, diameter of primary and secondary ovarian follicles and corpora albicantia (macro- and micrometric analysis of ovarian histological sections), as well as the release of progesterone, testosterone, oestradiol and insulin-like growth factor I (IGF-I) by isolated ovarian granulosa cells (RIA) were analysed. No significant differences between BCS2 and BCS3 cows in blood metabolic and endocrine indexes (except for decreased Zn2+ in BCS3 cows) were found. The ovaries of BCS2 cows, however, showed a lower ovarian area, diameter of both primary and secondary follicles and corpora albicantia, but not the number of visible secondary follicles as compared with BCS3 cows. No differences between the release of progesterone, testosterone and IGF-I by ovarian granulosa cells isolated from BCS2 or BCS3 cows were found, but the granulosa cells of BCS2 animals released more oestradiol than those of BCS3 cows. These results indicate that a slight reduction in BCS (tendency towards emaciation) does not substantially affect ovarian secretory activity or metabolic blood indexes. On the other hand, a tendency towards emaciation is associated with reduced ovarian follicle growth (but not their number) and increased secretion of oestradiol. These observations suggest that a tendency towards emaciation can suppress bovine fertility via alterations in ovarian folliculogenesis and oestrogen release. A.V. Sirotkin et al. 317 Introduction Understanding the mechanisms and mediators of the effect of energy metabolism on reproduction can be important for control of both human and animal reproduction. Furthermore, such mediators could be useful for the welfare and selection of animals with a desirable metabolic and reproductive status for animal production. Metabolic state can exert both positive and negative effects on animal reproduction (Hernandez-Medrano et al., 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). 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). The body condition of dairy cows, evaluated by visual estimation of the body condition score (BCS), influences their reproductive characteristics, i.e. 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). 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
Authors and Affiliations
A. V. Sirotkin, P. Makovicky, E. Kubovicova
Keywords
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