Effect of sex on live weight and growth intensity of Thracian merino lambs

Stanimira Slavova, Georgi Kalaydzhiev and Petia Slavova

Abstract: The aim of the present study was to determine the effect of sex on live weight and growth intensity of lambs of the Thracian merino breed, raised at the Agricultural Institute in Stara Zagora. For the period of two years, ewes in the flock were divided into 2 groups – mated in the spring (hormonally treated) and in the summer (not hormonally treated). The autumn progeny formed the Ist (experimental) group and respectively the winter progeny – the IInd /control/ group. Live weight of lambs at birth, at 10, 30, 70 days of age and at weaning was reported and growth intensity was calculated. Feeding and rearing were equal for both groups. As a result, it was found that male lambs had a higher live weight than females, born in the autumn, with the exception of twins at weaning. Significant differences were found at all ages for the singles /except at weaning/ and from birth up to the 30th day of age for the twins. The male progeny, born in the winter, also showed higher live weight than female progeny, except for the singles at 30 days of age. Significant differences of medium degree (p < 0.01) were established at the age of 70 days for both singles and twins and of low degree (p < 0.05) only for the twins at birth and at 10 days of age. The live weight of lambs from both groups increased most intensively in the period from 30th to 70th day after birth, except for the females, born in the winter, which grew rapidlier by the 10th day after birth in comparison to the next ages. A higher average daily gain was calculated for the male progeny in the experimental group, while in the control group the results varied by sex.

Keywords: average daily gain; effect of sex; ewes; lambs; Thracian merino breed

Date published: 2022-12-09