Influence of age and live body weight on daily milk yield of Zaraibi and Shami goats in Sinai, Egypt

The objective of this work was to study the relationship of daily milk yield (DMY) on age and live body weight on of Zaraibi and Shami goats in Sinai, Egypt. Fifty lactated Zaraibi and 60 lactated Shami goats were used to record the DMY (g) during March–August 2009. Age of the both studied breeds was ranged from 24 to 72 months. Weight was ranged from 20 to 33 kg in Zaraibi and from 25 to 40 kg in Shami. Data of DMY were statistically analyzed to obtain the partial regression coefficients of DMY on age and weight within each studied breeds. Two models were used to estimate the partial linear and/or quadratic coefficient of DMY on age and weight. According to the results of model 1, Model 2 was done for DMY on age as linear and weight as linear and quadratic in Zaraibi. While, in Shami model 2 was done for DMY on age and weight as linear only. Results indicated that DMY of Zaraibi and Shami were 576± 9.7 and 587± 9.2 g, respectively. In model 1, partial linear and quadratic regression coefficient estimates in Zaraibi for DMY on age were (b1) 1.93 g/mo and (b2) 0.03 g/mo2 and on weight were (b3) 121 g/kg and (b4) 2.17 g/kg2, respectively. These result indicated that relationship of DMY on weight was negative curve-linear. While, partial regression coefficients in Shami goat were 0.49, 0.01, 32.75 and 0.37 for b1, b2, b3 and b4, respectively. In model 2, the linear relationship of DMY on age (b1= 1.38 g/mo) in Zaraibi became negative and significant (p 0.05). While, of DMY on weight have the same trained as model 1. In Shami the linear relationship of DMY on age (b1 =0.46 g/mo) became positive and not significant (p 0.05). While, of DMY on weight became highly (p 0.01) significant (b3= 9.06 g/kg).