Selection in Marwari sheep: 2. Gain in body weight and growth efficiency

667 Marwari lambs of a selection line and tester group born during 1994–96 were analyzed to assess the impact of sex, genetic group and year of birth on gain in body weight and growth efficiency during 0–3, 3–6,6–9,9–12 and 3–12 months of age. The overall least squares means of gain in body weight were 8.91±0.08, 3.53±0.06, 3.26±0.06, 2.56±0.08, 8.94±0.10 kg and 319.93±3.68, 30.13±0.54, 22.99±0.57, 14.11±0.47, 76.17±1.03% for growth efficiency. Sex and year of birth showed highly significant (P<0.01) influence on all body weight gains and growth efficiency except the non significant influence of sex on growth efficiency during 0–3 and 3–12 months of age. The gain in weight and growth efficiency did not differ between tester and elite groups. The body weight gain during 0–3 (pre-weaning) and 3–12 (post-weaning) months were almost identical. Regression of dam's weight at lambing and birth weight, 3, 6, 9 and 3 months weight showed highly significant influence on gain in weight during the age groups under study. The negative regression of birth, 6 and 9 months weight on body weight gain during 0–3, 6–9 and 9–12 months, respectively indicated that the lambs which had higher body weight at birth, 6 and 9 months age might not grow relatively faster at subsequent age suggesting rhythmical trend in growth rate.