Effect of non-genetic factors on growth traits of Avikalin sheep

Avikalin is a synthetic sheep selected over the years for higher growth and fleece yield. The objective of the present study was to evaluate the growth performance of Avikalin over 4 decades in light of several non-genetic factors for better management decisions. The data on 7274 Avikalin sheep born to 2418 dams and 409 sires spread over a period of 41 years (1976-2016) maintained at the Animal Genetics and Breeding Division, ICAR-Central Sheep and Wool Research Institute (CSWRI), Avikanagar, were used for study using least squares analysis. The least squares mean (LSM) with standard error (SE) for birth weight (BWT), weaning weight (WWT), 6-month weight (6WT) and 12-month weight (12WT) were 2.98 +/- 0.01 kg, 14.42 +/- 0.06 kg, 21.21 +/- 0.09 kg and 27.07 +/- 0.12 kg, respectively. Average daily gains from birth to weaning (ADG1), weaning to 6 months (ADG2) and 6 months to 12 months (ADG3) were, 126.52 +/- 0.65 g, 72.90 +/- 0.72 g and 32.70 +/- 0.72 g, respectively. Corresponding Kleiber ratio (KR) from birth to weaning (KR1), weaning to 6 months (KR2) and 6 months to 12 months were 16.8 +/- 0.04, 7.1 0.06 and 2.7 +/- 0.06, respectively. Regression of the ewe weight was highly significant on all growth traits except ADG3 and KR3. Thus, it was found essential to care the ewes with less weight for heavier lamb production. The effect of sex and period on all the growth traits was highly significant. The effect of season and parity was significant on early growth traits. It was observed that the lamb's birth weight has a quadratic relationship with the parity. Ewes in 3rd to 5th parity gave birth to heavy lambs as compared to ewes in their 1st parity and >= 7th parity. The study revealed improvement in the growth traits over the period due to selection and also negative impact of sudden change in management decision on growth of lambs. Understanding the decisive factors and adopting corrective steps can help harvest better growth of lambs.