Influence of some Genetic and Non-Genetic Factors on Total Milk Yield and Lactation Period in Iraqi Awassi Sheep

This study was conducted to evaluate productivity of Awassi sheep raised at the Research Station of Sheep and Goats/ Abo Gharib/West of Baghdad/Iraq. A total of 369 milk records of the Awassi ewes collected during year of 2008 were used to investigate the effect of non-genetic factors (parity, group of dam, month of birth, type of birth and sex) on total milk yield (TMY), and lactation period (LP). Data were analyzed by using GLM in SAS program. Restricted Maximum Likelihood Estimation method (REML) was used to estimate heritability (h2) for milk yield an lactation period. Best Linear Unbiased Predication (BLIP) values were estimated for rams. Results revealed that total milk yield (TMY) and lactation period (LP) were 103.57±3.63kg and 107.44±1.47 respectively. LP affected significantly (P < 0.01) by parity, group of dam (local and Turkish), month of birth and type of birth (single and twin), while the sex of birth was not significant. TMY was affected significantly (P < 0.01) by the same factors except the parity and sex of birth, which were not significant. Estimates of heritability for TMY and LP were 0.40 and 0.30 respectively. BLUP values of rams for total milk yield were between -33.61and 31.00 kg. These results point to a high genetic potential of Awassi sheep. Hence, it is imperative to apply selection programs to improve the productive performance of Awassi sheep in Iraq.