Comparison of alternative methods to estimate the milk yield of cows from Gyr breed

The objective of this work was to compare the alternative methods to estimate the milk yield of cows from Gyr breed. A total of 3,632 lactations from of Gyr breed cows, from 1986 to 1996, were analyzed. The methods were: A - the morning milking control was performed in the odd months and the afternoon milking control in the even months - the yield of the morning milking control was multiplied by the multiplicative factor of the morning (MP;) and that of evening by the multiplicative factor of the afternoon (AF), B and D - the control was performed in the morning milking (in B, the yield of the morning milking was multiplied by the MF and in D the yield was multiplied by two); C and E - the control was performed in the evening milking (the yield of the afternoon milking was multiplied by the AF and in E it was multiplied by two). All methods were compared with the actual production (R). The method A showed the most precise, being the precision of method C intermediate between the B and D methods. The Pearson correlation among the estimate yields by the different methods and R, by the production at the 305 days and total production, were, respectively,.98,.95, and .96 for A,.97,.93, and .95 for B,.93,.90, and .89 far C,.97,.94, and .95 for D and .93,.89,.98 for E method. The method A showed the most viable to estimate the milk production ire the day of milk production control by its practicability and precision, while the C and E methods were the worst among the evaluated milk control methods.