Effect of various dietaries on milk composition and efficiency of production of dairy cows

Abstract

REVIEW OF LITERATURE This section will review literature relating to the use of various dietaries (roughage to concentrate ratios and planes of nutrition), the factors causing changes in milk composition, and the interpretation of efficiency studies in experimenta tion with lactating dairy cows. Hay to Concentrate Combinations in Dairy Cattle Research A very limited number of reports are available in which the combination of dietaries has been similar to those explored in this research. Consequently, after reviewing these few re ports it will be necessary to consider research which has only partial or indirect application to this work. The work reported by Bloom (1955) and Bloom ert al. (1957) utilized the same dietaries as were used in the present study; roughage supplying 75, 55, 35 and 15 percent, respectively, of energy of the four ratios, with concentrate furnishing the remainder. These ratios were offered at three planes of nu trition, supplying feed energy for maintenance plus 13,000, 11,000 and 9,000 pounds of 4% fat corrected milk (PCM) over a 243-day lactation period. During a controlled 7-week pre liminary period the 36 Hoistein cows were classified into three ability groups (high, medium and low) and were placed on the experimental rations. Bloom noted a marked adjustment