The average least square means of birth weight, weight at 1-, 3-, 6- and 12-months were observed as 1.76 ± .06, 4.13 ± .15, 8.94 ±. 31, 13.81 ±. 53 and 23.23 ± 1.00 and 1.81 ±. 07, 4.02 ±. 15, 8.41 ± .35, 13.06 ± .51 and 26.51 ± .75 kg in male and female, respectively having insignificant sex difference (p<.05). ADG1 (birth-weaning) and ADG2 (weaning-six month) were found as 54.13 ± 2.65 and 54.30 ± 2.89 and 47.41±3.00 and 51.08±4.58 g/d in male and female, respectively. Both ADG did not differ (p>.05) between sexes. Sire, region, birth type, dam’s parity and season of birth, birth type×kid sex and birth type×birth season impacted growth traits mostly in the earlier stages. Season of birth (p<.001) and its interaction with birth type (p<.05) affected 12-months body weight. Dam parity (p<.05) and birth type (p<.001) influenced ADG1 and sire (p<.05) and season of birth (p<.05) influenced ADG2. Only 5% of the F1 does manifested behavioural oestrus within 1 year of age. Boer × BB F1 crossbreds gained more than two times higher than BB goats under similar extensive management and environment. Since dams are BB, therefore, litter size remains unaffected. It suggests that goat farmers in Bangladesh can have more than two times higher benefit by producing this type of crossbreds. As sex of the kids does not affect body weight and body weight gain, animals of both sexes may be recommended for slaughter without further breeding.

Highlights

• Evaluation of growth performance of F1 crossbreds.
• Determination of genetic and non-genetic factors affecting body weight and body weight gain at different ages.