Relationship of feed intake during various portions of the lactation to total intake in dairy cattle

Since the cows' ability to consume feed is a limiting factor on milk production, the development of alternatives to the measurement of complete feed intake are necessary if this trait is to be measured and evaluated on large numbers of animals. The purpose of this research was to examine the part-to-whole relationships of lactation feed intake to determine if suitable alternatives were available. Feed intake data on 225 first lactations of daughters of 13 sires fed two rations were used to study the part-to-whole relationships of lactation feed intake. Correlations were used to determine the relationship of feed intake in various portions of the lactation with the total feed intake for the lactation. From this study it appears that feed intake during shorter periods in the middle of the lactation are as accurate as extended periods at the beginning of the lactation as a measurement for estimating total feed intake. Ratio factors were calculated from which lactation estimated net energy intake can be predicted from intake during a portion of the lactation. The similarity of the ratio factors between the two rations, in mid-lactation, suggests that this information may be applied to a wide range of management levels and could probably be used to obtain reasonable estimates of means for older animals.