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Concentrate Allowances by 1971 National Research Council Standards Compared to Other Feeding Guides for Lactating Dairy Cows

Department of Animal Science, Macdonald Campus of McGill University, Ste. Anne de Bellevue, Quebec, Canada

ABSTRACT

Daily concentrate was allotted to lactating cows as recommended by both the National Research Council (NRC) requirements of 1966 and 1971 for digestible energy and compared to a feeding guide using estimated net energy. Twelve Holsteins and six Ayrshires were divided into three equal groups. Design of the experiment was double reversal with three 28-day periods. All groups were offered the same amount of forage. Cows fed according to the 1971 NRC standard produced less milk and lost weight when compared to cows fed according to the estimated net energy standard. The 1966 NRC standard did not differ from the other standards. The new NRC requirements resulted in less concentrate being offered and a greater ratio of milk production to concentrate allowance. Milk fat and protein percentages were similar between groups. The validity of the 1971 NRC standards for formulating feeding guides is discussed.