Relationship between Age of Iraqi Awassi Ewes and Responses to Superovulation Protocols

Abstract

The current study aimed to investigate the relationship between the age of ewes subjected to various superovulation programs and the response of those ewes to the programs under study through the standard fertility parameters adopted in this type of studies.
Seventy healthy Awassi ewes were divided into seven equal groups (10 ewes for each) whose ages ranged from 2.5 to 7 years, with two age categories for each of the seven study groups, (the group of ewes less than 4 years old and the group of ewes aged 4 years and older) as follows: Control group (c) that did not receive any treatment (G1): a group of long-term progesterone sponges (14 days) with eCG injections on the day of the sponges’ withdrawal, then GnRH injections on the day after the sponges were withdrawn. Group (G2) was the same as group (G1), but without GnRH injections. Group (G3) received short-acting progestin (CIDR) in the same design as (G1), while group (G4) received (CIDR) in the same design as group (G2), but for 7 days only days for both groups (G3, G4). While group (G5) was injected with PGF2α in two doses 9 days apart, the eCG hormone was injected one day before the second dose, then GnRH was injected one day after the second dose of PGF2. The last group (G6) is similar to group (G5), but without the GnRH injection.
The results recorded a superiority for ewes within the age category of 4 years and older in most of the study groups in the parameters of the twinning rate, and litter size rate, compared to the age category of less than 4 years, with the opposite in respect to litter size rate, when all groups recorded superiority for age category of 4 years and older with some exceptions. While no differences were recorded between the two age categories under study in the rest of the fertility parameters, namely the estrus rate,lambing rate and survival rate. The current study conclude that the best age for ewes subjected to superovulation programs should be confined Under 4 years old.