Relationship of Feed Intake and Ration Digestibility to Estimated Transmitting Ability, Body Weight, and Efficiency in First Lactation

Abstract

Forty-nine Holstein cows in 1st lactation representing a wide range of estimated transmitting abilities were fed complete feeds ad lib from calving to 305 days of lactation. Rations included equal parts (dry matter basis) of corn silage and hay crop silage mixed with sufficient concentrate to provide 60% of the digestible energy estimated for the ration during the 1st 180 days and 40% thereafter. Feed intake was correlated .3 with estimated transmitting ability during mid-lactation (days 91-180) but about half of that during other periods or over the whole lactation. Intake of dry matter during the total lactation, days 91-180, and days 181-305 was correlated with lactation yield of solids-corrected milk .81, .78 and .82. During early lactation (days 1-90), feed intake was associated more closely with body weight than with other traits (r = .44). Gross efficiency of lactation as the ratio of solids corrected milk to dry matter intake was correlated .6 with intake of dry matter. Metabolism trials on 24 cows at an average of 232 days of lactation indicated no association between ability to digest ration and estimated transmitting ability. Estimated transmitting ability is not a useful predictor of lactation intake of feed or ration digestibility.