Non-Genetic Factors and Estimates of Repeatability for Milk Traits in Maraz Goats
This work was conducted at the private flock of Maraz goat at Bamerny Sub-district-Amadiya district -Duhok governorate during kidding seasons 2015-2016. Does were synchronized byusing intra-vaginal sponges and mated with bucks by hand mating. Milk traits consist of 305 monthly records of test-day milk yields (TDMY), 54 of each of total milk yields (TMY), pre-weaning milk yields (PWMY) and 53 post-weaning milk yields (POWMY) were obtained from 57 goats. General liner model and Mivqueo methods of SAS (2005) were used to study the effect of factors on the studied traits and restricted maximum likelihood (REML) to estimate repeatability of TDMY. Overall mean of TDMY, PWMY, POWMY and TMY were 0.659, 35.286, 20.98 and 55.88 kg, respectively. Type of birth had a significant effect on TDMY (P<0.05) only. Also the effect of stage of lactation on TDMY was significant (P<0.01), the maximum and the minimum TDMY were attained during third test (0.870kg) and seventh test (0.288kg), respectively. Weight of doe at kidding had a significant effect on TDMY (P<0.01), with a positive regression coefficients of 0.0123, respectively. In addition, the repeatability estimates by REML method for TDMY were 0.23. It was concluded that type of birth, stage of lactation and does weight at kidding had significant effects on TDMY, so it is necessary to apply adjusted model to reduce the effect of factors before estimating the genetic parameters and repeatability estimate for TDMY was relatively low and this refer to that selecting does on their records at early stage of lactation cannot be performed. Keywords - Non-Genetic Factors, Reeatability, Milk Traits, Maraz Goat.