Milk progesterone profiles, blood metabolites, metabolic hormones and pregnancy rates in Awassi ewes treated by gestagen + eCG at the early breeding season

Abstract

The ovarian response to a standard chronogest + eCG treatment with plasma levels of insulin, insulin-like growth factor-I (IGF-I), thyroids, non-esterified fatty acids (NEFA), OH-butyrate (BHB) and urea-N (PUN) was studied in lactating Awassi ewes (<i>n</i> = 105) during the late-summer – early autumn transition period. The ewes were inseminated with diluted fresh semen after gestagen removal, and mated thereafter; 26 of them conceived at the fixed-time AI (fix AI; conception rate is calculated from lambing dates). Ovarian function was monitored by milk progesterone (P₄) profiles. Before synchronization, the ovary was still acyclic in 33 and already cyclic in 72 ewes. Twenty-nine and 43 of the cyclic animals were in the follicular and luteal phases, respectively. After gestagen removal almost all (<i>n</i> = 104) ewes ovulated, although at AI elevated P₄ levels related to the presence of partially luteinized follicles, and short-lived CL-s were observed in 10 and five animals (none of them re-conceived at the fixed time AI). Cycling ewes showed higher insulin and IGF-I levels than the acyclic animals, and those who had not conceived had higher PUN than the pregnant ones. The other metabolic parameters did not differ. Neither conception rate, nor the ovarian response was influenced by the pre-treatment.