Some Effects of Feeding Frequency on the Utilization of Isocaloric Diets by Young and Adult Sheep

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Abstract
Three experiments were conducted to determine the effects of the frequency of feeding on the utilization of isocaloric rations by sheep of different ages. Growing sheep (6 months old) fed 8 times per day gained 65% more weight (P < 0.01), excreted 20% less of nitrogen in the urine (P < 0.01) and tended to produce less heat than when fed the same daily quantity of feed in one meal. The same feeding frequencies had no effect on the body gain or urinary nitrogen excretion by more mature sheep (2.5 years old). Feeding frequency also had no effect upon the apparent absorption of energy or nitrogen by either growing or adult sheep. Although the average pH values of the ruminal ingesta were not different for the two feeding frequencies, those for the animals fed once daily fluctuated more drastically. The total output of heat per day by animals on the one meal regimen housed in isolation was not different from that produced when they were housed in the same quarters with the sheep fed 8 times per day. During the daylight hours (when sheep were fed), however, the output of heat by the sheep fed one meal was 13.4% greater (P < 0.01) in the presence of the frequently fed sheep than it was under isolation. The animal's output of heat during the remainder of the 24-hour period was compensatory. The amount of creatinine, urea or total nitrogen excreted in the urine of 14-month-old sheep was not different when isocaloric diets were ingested in one, 4 and 8 meals per day. A study of the diurnal output of heat showed that the production of heat by sheep fed one meal per day reached a higher peak after eating and decreased more abruptly during the day than that of sheep fed more frequently. During the nonfeeding hours for the frequently fed sheep, the output of heat was lowest for all sheep irrespective of their feeding-frequency regimen. The results of these studies and those reported by others suggest an interaction of age and frequency of feeding on the response of ruminants. Further study is needed to determine the fundamental reasons for this apparent relationship.