Genetic Improvement of Some Productive Traits in Zaraibi Goats

The objective of this study was to evaluate the genetic improvement in Zaraibi goats herd raised on El-serw research station located in the north eastern part of Nile Delta, Egypt. The station belongs to Animal Production Research Institute (APRI). Some body weights at different ages were included in genetic and environmental trends. These weights were 4-month weight (4M), 6-month weight (6M), and 12-month weight (12M). Data and pedigree information were collected from 1988 until 2018. The least square means of body weights at 4M, 6M and 12M were 12.14±0.02, 15.49±0.02 and 24.08±0.04 kg, respectively. Year of birth, season, gender of kid, parity of dam and type of birth significantly (P<0.01) affect growth traits. Genetic parameters were estimated using a multi-trait animal model program (MTDFREML). The same previous fixed effects were included in this analysis regarding the animal as random effects. The heritability of the studied body weights tend to increase as age increases. That is inversely matched with the environmental proportion of total variance which was found to be 0.72, 0.66 and 0.62 for M4, M6 and M12, respectively. The heritability value was estimated as 0.28 for 4M. Genetic trends were obtained as the regression of the predicted breeding values on years of birth and Environmental trends were obtained as the regression of year constants on years of birth. The annual genetic change trends were positive and significant for 4M, 6M and 12M (0.091, 0.121 and 0.158 kg/year, respectively) and the annual phenotypic change trends were (0.020, 0.045, 0.117 kg/year, respectively). Genetic trends for M12 trait were higher than those for other traits in this study. Genetic and environment correlations between 4 month body weight and other growth traits were positive. Negative environmental trends indicates poor management system for the flock during studied period. Weight at 12 months of age has the highest heritability in studied body weights and suggested to be selection criteria to improve yearling weight for Zaraibi goat.