The Efficiency of Utilization of Protein in Milk Production, as Indicated by Nitrogen Balance Experiments

Abstract

This paper is based upon data obtained by E. B. Forbes and associates in a series of 60 mineral and nitrogen balances with milch cows at the Ohio Agricultural Experiment Station, the main results having been published in Ohio bulletins Nos. 295, 308, 330 and 363, in the years 1916-1922. 3 In these experiments the determination of the nitrogen balances was incidental to the project of investigation of the mineral metabolism, and in the above mentioned publications little use was made of the nitrogen balances, except for general confirmatory purposes in connection with the balances of the other elements studied, especially sulphur, calcium, and phosphorus. Especial reasons for conservatism in the interpretation of this extensive series of nitrogen balances lay in the well-known adaptability of animals to different planes of protein intake, the extensive possible use of protein for energy production, and the slowness with which final effects of a particular level of protein consumption are attained. Having refrained from attempts to use these nitrogen balances in a critical manner as the experiments have been worked up, one at a time, we have now undertaken to derive from the accumulated data average figures for efficiency of utilization of protein as indications of the proportion of the protein of the feed