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Compensatory Growth of Intensively Raised Bull Calves II. The Effect of Feed Energy Concentration^{1, 2,}

The Agricultural Research Organization, Volcani Center, Bet Dagan and and Neve Ya'ar Regional Experiment Station, Israel

Abstract

The effects of temporary energy restriction and refeeding on the performance of Israeli-Friesian bull calves were studied in two experiments using a total of 160 animals. Restriction, started at 180 days of age, continued for 80 or 90 days; feeding levels of maintenance and 125% of maintenance were fed during restriction. The major variable studied was feed energy concentration during restriction. The effects of varying the level of feeding during the refeeding period were studied in one experiment.

Under certain conditions considerable compensatory growth occurred, unlike in a previous study. Nevertheless, average daily gain was highest in the control groups fed ad libitum or 85% of ad libitum; feed efficiency in the latter was 9% higher than in the former. A comparison of rations containing 1.50 and 1.10 Mcal/kg net energy for maintenance during restriction, indicated that the former promoted significantly better overall performance (a) in terms of average daily gains and feed efficiency throughout both experiments, and (b) in terms of increment in body measurements and weight gains during restriction in one experiment. Increasing the amount of protein in the low energy ration fed during restriction eliminated the differences due to feed energy concentration during restriction but did not improve the relatively inferior performance of the bull-calves throughout the experiment.

A uniform feeding level of approximately 85 to 90% of ad libitum was found to be the most efficient method of raising bull-calves of the dairy herd fed intensively to 500 kg at slaughter; it is doubtful whether the slight advantage in leaner carcasses of the bull calves restricted for 80 or 90 days can offset the disadvantage in average daily gains.

¹ Contribution from the Agricultural Research Organization, Volcani Center, Bet Dagan, Israel. 1973 Series, No. 114-E.

² This research was financed in part by a grant made by the U.S. Department of Agriculture, under P.L. 480.