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Urea Utilization by Young Dairy Calves as Affected by Chlortetracycline Supplementation¹

Department of Dairy Science, University of Kentucky, Lexington

ABSTRACT

Forty-eight two-day-old male and female calves representing the Holstein and Jersey breeds were raised to 86 days of age on a limited milk-hay-starter system to study the effect of chlortetracycline on urea utilization at three levels of protein equivalent intake. Four experimental starters ranging from 6.5 to 15.3% protein equivalent were fed with and without chlortetracycline supplementation. Highest average daily gains were made by calves on the 12.1% protein equivalent starter with chlortetracycline. The growth of calves increased as the protein equivalent level of the starter increased up to the 12.1% protein equivalent starter. Chlortetracycline did not spare dietary nitrogen in this study, but did significantly increase average daily gains, skeletal growth, and feed efficiency. Chlortetracycline had no significant effect on apparent digestibility of any ration nutrient, nitrogen retention, or blood levels of plasma protein and urea nitrogen. Coefficients of dry matter and crude protein digestibility, as well as nitrogen retention values, were significantly lower for calves on the 6.5% protein starter than for any of the other groups. The trend was for increased protein digestibility as the level of protein equivalent in the starter increased.

¹ The investigation reported in this paper is in connection with a project of the Kentucky Agricultural Experiment Station and is published by permission of the Director.

² Present address: Dairy Department, Michigan State University, East Lansing, Michigan.