Reproductive Performance After hCG or GnRH Administration of Long-Term Progestagen Treatment of Fat Tailed Ewes During Seasonal Anoestrus

Abstract

This research was carried out to evaluate the effect of hCG or GnRH two days after long-term progestagen treatment on the reproductive performance of Mehraban ewe during seasonal anoestrus under field conditions. A total of 75 ewes pretreated with intravaginal progestagen sponges left in situ for 14 days and all ewes were treated with Pregnant Mare Serum Gonadotrophin at the time of sponge removal. Two days after removal of sponge, the ewes in two groups were injected (im), either with hCG (hCG group) or with GnRH analogue (GnRH group) and the other group remained untreated and served as control. Blood samples were collected on day 19 after sponge removal from all animals to measure serum concentration of progesterone in order to pregnancy diagnosis. The reproductive performance of the Mehraban ewes in all groups was assessed by lambing data. The pregnancy rate of ewes was highest in the hCG group (86.4%), compared to the control (60%; P 0.05) groups, respectively. The percentage of lambing rate of the ewes which lambed from mating at the induced oestrus was highest in the hCG group (85.7%), when compared to the control (58.3%; P 0.05) groups. The highest proportion of twin lamb birth rate was recorded in the hCG group (61.1%), compared to the control (57.1%; P>0.05) and GnRH (31.3%; P<0.05) groups. The hCG group recorded significantly greater mean single and twin lamb birth weight compared to the control group (P<0.05). It can be concluded that hCG injection, two days after sponge removal, increases prolificacy and can improve reproductive performance of Mehraban ewes outside the breeding season, which is in high importance for sheep holders from economical point of view. Key Words: Ewe, anoestrus, progestagen, hCG, GnRH, prolificacy