The effect of non-genetic factors on the birth weight of Romanov sheep

Abstract

The aim of this study was to analyse the non-genetic factors influencing the birth weight of Romanov lambs, and to determine which of them may be a useful source of information in the selection of female lambs for replacement. The study included 1712 lambs born in the period from 2016 to 2019. The linear model used in birth weight estimation included: birth type, sex, parity, year of birth, season of birth, and breeding group as fixed factors. Year of birth x season of birth interaction was also included in the model. All factors, except the season of birth, significantly affected birth weight (P<0.05). Birth weight decreased significantly (P<0.05) with increasing birth type and singles, twins, triplets and quadruplets weighing 4.11 ± 0.07, 3.56 ± 0.05, 3.07 ± 0.05 and 2.66 ± 0.08 kg, respectively. Male lambs (3.44 ± 0.05 kg) were significantly (P<0.05) heavier than female lambs (3.25 ± 0.05 kg). The lightest lambs (2.99 ± 0.05 kg) were born in the first litter, after which the birth weight gradually increased up to the sixth litter (3.54 ± 0.10 kg). Litter weight showed a nonlinear increase with an increase in birth type (P<0.05). The birth weight of female lambs from litters of twins and triplets with different ratios of male and female lambs did not differ significantly (P>0.05). Variations in birth weight are influenced by non-genetic factors, with birth type, sex, and parity being the most important. These factors should be considered in breeding and selection programs for lamb meat production, where fertility and growth traits have the key role.