Relationship of body condition score, body weight and tail measurements at mating with the reproductive performance of Gray Shirazy sheep.

The aim of this study was to determine the relationship of the body condition score (BCS), body weight and fat-tail measurement of ewes at the beginning of mating season with their reproductive performance of Gray Shirazy sheep under an extensive production system. For this reason, in 5 flocks in different parts of Fars province, a total of 900 ewes were divided in 2 groups based on two method of mating. In method 1 mating was natural (without synchronization of estrus) and in method 2 synchronization of estrus was done byinsertion of an CIDR for 12 days followed by an im injection of 500 IU eCG at CIDR removaltime, then eweswere artificially inseminated. All ewes were used for measuring body condition score, body weight and tail measurement for over a 2-year period before the introduction of rams or artificial insemination. After pregnancy period and parturition, reproductive characteristics were calculated. The data were analyzed by chi square test and GLM procedure in SAS. Lambing rate were 78.3, 97.6, 99, 99, and 69.4 in different group (1 to 5) of BCS respectively. In BCS=5 fertility rate was 73.6 (minimum) and in BCS=3 was 99 (maximum). Number of lambs born per lambing (litter size) in different groups of BCS was range from 1.00 to 1.36 (P=0.01). Fecundity rate (pregnant ewes to inseminated ewesأ 100) in different group (1 to 5) of BCS were 71.4, 116, 126, 123 and 66.5 respectively. The abortion percent was 9% (maximum) in BCS=1 and 0.9% in BCS=2 (minimum). The difference among BCS groups for abortion percent was very significant (P=0.01).The pregnancy rate was statistically different among BCS groups (P0.01) and were 58, 89, 94, 93 and 52 in BCS 1 to 5, respectively.In natural method of mating, there were statistically differences in lambing rate among BCS groups (P=0.01). In BCS=5 fertility rate was 75 (minimum) and in BCS=3 was 99 (maximum). Number of lambs born per lambing (litter size) in different groups of BCS was range from 0.95 to 1.13 (P0.01).The minimum level of fecundity rate was 68% for BCS=1 and the maximum level was 106% for BCS=3.The abortion percent was ranged from 0.0 for BCS=3 to 6% in BCS=1 (P0.01).The pregnancy rate was statistically different among BCS groups (P=0.01) and were 52, 82, 86, 86 and 51in BCS 1 to 5, respectively.Some reproductive characteristics in different BCS were significantly different in both natural mating and artificial insemination method.In most cases, these characteristics in artificial insemination method were higher than natural mating. The spearman correlation coefficient between BCS, tail dimension and body weight ranged from 0.16 to 0.61 (P=0.01).According to these results, if the farmer will obtain sufficient experience toestimate BCS accurately and use management techniques such as flushing at mating time in the breeding season (early September to mid-October), ewes will reach to the optimum BCS (BCS between 3 - 3.5), thenreproductive characteristics and followed farmer profit will increase.In the non breeding season (Frommid-March to lateMay), concurrent use of estrous synchronization (with CIDRand PMSG) technique and estimation ofBCS of sheep, in addition to concentrate lambing time in desired date and improving sale management,it can cause to increase the reproductive characteristics of ewes and farmer profit. Keywords:Gray Shirazy sheep, Body Condition Score (BCS), reproductive characteristics