Is there a relationship between serum minerals (Ca, Mg) and trace elements (Cu, Fe, Mn, Zn) at mating on pregnancy rates in fat-tailed Morkaraman sheep?

Abstract

The specific roles of nutrients in reproduction are not well defined in sheep. Hence, the relationships between certain mineral (Ca, Mg) and element (Cu, Fe, Mn, Zn) levels at mating and pregnancy rates was investigated in fat-tailed Morkaraman ewes synchronised with different hormones (melatonin, norgestomet implant and eCG) early in anoestrus season. For this purpose, 40 healthy ewes (aged 2-4 years) allocated in the synchronised (n=30) and no-treated group (n=10) were used during mid-May (suckling period). On the eCG injection day, fertile rams (n=8) were introduced into the groups and, then the oestrus signs were visually monitored twice daily for 7 days. The oestrous ewes were allowed to hand-mate using rotational (four rams daily) mating system. Additionally, jugular blood samples were collected on the days of onset of oestrus (before mating) for determination of serum Ca, Cu, Fe, Mg, Mn and Zn levels. Presence of pregnancies was diagnosed by real-time ultrasonography 35 days post-mating. Totally, 25 ewes became pregnant (21 ewes with stimulated- and 4 with spontaneous oestrus), while 9 ewes (all received stimulation) were not pregnant. In non-pregnant ewes, unlike other minerals and elements, the Cu and Zn values were significantly lower than their reference values (for Cu: 0.87±0.16 mg/dl vs. 9.20 mg/dl; for Zn: 2.06±0.30 mg/dl vs. 3.8 mg/dl, resp.; P less than 0.01 in both cases). In pregnant ewes, the corresponding values remained unchanged (P>0.05). Hence, the present findings indicate that the low Cu and Zn levels during the oestrus might adversely affect the subsequent pregnancy rate in suckling ewes.