Abstract
The objective of this experiment was to determine whether post-mating progesterone (P4) supplement improves pregnancy and lambing rates in ewes bred during the seasonal anestrous period. In June, 39 synchronized to estrus Awassi ewes were allowed with four harnessed fertile rams immediately following CIDR-G device removal (day 0 and 0 hour). Five days following ram introduction, ewes were randomly assigned to four groups to be treated post-mating with intramuscular injections of 20 mg P4 supplement once daily from day 5 to day 9 (P4-D5-9), days 10 to 14 (P4-D10-14), days 5 to 14 (P4-D5-14) or did not receive P4 supplement (control). Blood samples were collected from all ewes for P4 analysis. Progesterone concentrations prior to CIDR-G insertion were basal and no differences in P4 concentrations were found on days â12, â10 and between days 0 and 5 among groups. Progesterone concentrations between days 5 and 15 differed (p
Highlights
Reproductive performance of Awassi ewes has been low under semi arid conditions[1]
Progesterone concentrations declined to day 0 values of 2.4 ±0.1, 2.4 ± 0.1, 2.3 ± 0.1 and 2.5 ± 0.2 ng mL–1 for the P4-D5-9, P4-D10-14, P4-D5-14 and control groups, respectively
All ewes ovulated during this period based upon the subsequent rise in P4 concentrations following CIDR-G removal
Summary
Reproductive performance of Awassi ewes has been low under semi arid conditions[1]. The fertility rate has been estimated to be 0.9 lambs per ewe mated and the majority of lambs born are singles, with some twins and rare triplets. Fertilization and early embryonic mortality rates are among factors influencing litter size[2]. At the time of CIDR-G removal (day 0 and 0 plasma P4 concentrations during the luteal phase are hour) four Awassi rams fitted with marking harnesses important for maintaining pregnancy[11]. Ewes with lower concentration of P4 are more prone to embryonic loss, perhaps, as a result of insufficient maternal recognition of pregnancy signals[12]. It is (P4-D5-9), from day 10 to day 14 (P4-D10-14), and from day 5 to day 14 (P4-D5-14) or did not receive P4 supplement (control group).
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