Effects of Environmental Factors on Pre-Weaning Growth Traits in Zandi Lambs

The present study was carried out to investigate the effects of environmental factors on pre-weaning growth traits in Zandi sheep. Data (birth weight, weaning weight and average daily gain from birth to weaning) were collected from lambs that have been born during 1993-2008 in Khojir Research Station (Tehran-Iran) and analyzed using SAS 9.1 software. Birth year, birth type, lamb's sex and dam's age were highly significant sources of variation on Birth Weight (BW), Weaning Weight (WW) (p<0.01), whilst lamb's sex was not significant on Average Daily Gain from birth to weaning (ADG). The interaction effects between birth year and birth type and dam's age and birth type were significantly affected on these traits (p<0.05). At birth and weaning, the male and single lambs were heavier than female and twin lambs. Results showed that environmental factors have an important role in expressing of genetic potential in the lambs. Average weights were 4.23 +/- 0.012, 21.17 +/- 0.060 and 0.174 +/- 0.00 kg for BW, WW and ADG, respectively.