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Energy and Protein Utilization during Lactation

Department of Animal Sciences, University of Maine, Orono

ABSTRACT

Nine Holstein cows selected for the first phase of this study produced an average of 19,171 lb of milk and 668 lb of fat (2x–305). These cows had an average gross energetic efficiency of 40.6%.

The average requirement of TDN above maintenance after adjusting for body weight changes for all cows through the entire experiment was 0.287 lb per pound of FCM produced. High net energetic efficiencies were associated with early stages of lactation or high levels of production. A high, significant correlation (r = 0.82) was found between energy requirement and level of production.

The protein equivalent of a pound FCM in this study was found to be 3.43%. The average requirement of digestible protein above maintenance during the entire experiment was found to be 0.052 ± 0.004 lb. All cows showed higher protein efficiency at early stages of lactation than later in the lactation. A significant correlation (r = 0.73) was found between protein requirement and level of production. There was considerable variation among cows in energetic and protein efficiencies.

¹ Present address: College of Agriculture, University of Bagdad, Bagdad, Iraq.