Relationship between ewe body condition score (BCS) at mating and reproductive and productive traits in Lori-Bakhtiari sheep

Abstract

The data set used in this study consisted of 1099 records of body condition score (BCS) and respective reproductive and productive traits from 442 ewes, recorded over a 3year (2006–2008) period, of a Lori-Bakhtiari research flock at the Shooli station. The aim was to determine the relationship of BCS with reproductive and productivity performance. Body condition scoring was assessed 1–2days before mating, based on a scale of 1–5, by palpation of muscling and fat deposition over and around the vertebrae in the loin region. The data set was analyzed using a model that included BCS, as well as other factors that affected reproductive and productive traits. The results showed that the overall mean ewe body condition at mating was 2.6, the highest relative frequency (32%) being observed for a BCS of 2.5. Of the total ewes, 62.1% recorded a BCS of between 1 and 2.5. The effect of ewe BCS was significantly (P<0.01) related to ewe body weight, reproductive traits (conception rate, litter size at birth, weaning rate, number of estrous cycles to conception in each season) and the ewe's productivity (total litter birth weight and weaning weight per ewe exposed). Ewe body weight at mating increased by 3.1kg with each increasing unit of BCS. The least square means for most of the reproductive and all of the productive traits increased, with increasing ewe BCS – reaching maximum values at a BCS of 3.5 and then decreasing in the presence of other factors affecting these traits. For most of the considered traits, the differences between ewes with a BCS of 3 and 3.5 were low and not significant (P>0.05). It is therefore recommended to maintain the BCS of ewes at mating in the range of 3–3.5, to optimize the profitability of flocks in this breed.