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Nonprotein Nitrogen Adaptation: Intake and Eating Patterns of Steers¹

U.S. Department of Agriculture, Beltsville, MD 20705

Abstract

Eating patterns of 16 steers (averaging 218 kg) fed ad libitum were monitored by means of photoelectric activated relays and a time event recorder daily for 217 days. Each day was divided into octaves (1 octave = 3 hr). There was a standardization period of 21 days during which all steers were fed a 12% crude protein diet containing 80% timothy hay (7% crude protein) with cottonseed meal as the source of supplementary nitrogen. Phase 1 (28 days, July 5 to August 2) followed the standardized period with all steers fed the cottonseed meal supplemented diet. On day 29, 12 steers were randomly switched either abruptly or gradually over 14 days to the same diet but with soybean meal, urea or biuret replacing cottonseed meal for 161 days (phase 2, August 3 to January 11). Phase 3 (January 12 to February 9) started on day 162 when the steers fed the soybean meal, urea and biuret diets were abruptly changed to urea or biuret, soybean meal or biuret, and soybean meal or urea, respectively, for 28 days. Feed and water consumption were measured and replenished daily at 1500 hours. Steers visited the feeder during all eight of the octaves; however, more (P<.05) time was spent at the feeder from 0600 to 1800 hours. Eating patterns appeared to be influenced by diurnal variations and by supplementary nitrogen source when abruptly switched from another source of nitrogen. Feed intake appeared to be influenced by abrupt switches and by source of nitrogen but showed no pattern characteristic of adaptation. Water intake was positively related to feed intake and ambient temperature. Although results from the present experiment showed no clear trends, the data suggested that steers need an adaptation period when switched abruptly from one source of nitrogen to another nitrogen source in similar diets.

¹ The authors gratefully acknowledge the technical assistance of C. V. Beall, Jr., L. I. Colbert and P. P. Padovano and the secretarial assistance of Ms. G. M. Collins and Ms. M. A. Grier in the preparation of this manuscript.

² Science and Education Administration, Nutrition Institute, Ruminant Nutrition Laboratory.

³ Present address: U. S. Meat Animal Research Center, Clay Center, NB 68933.

⁴ Consulting statistician, Northeastern Region, Science and Education Administration.