Hormones and Amino Acids as Possible Factors in the Control of Hunger and Satiety in Sheep

Abstract

Several hormones and three amino acids were injected intravenously into sheep dur- ing spontaneous meals of a grain diet to test for their effect on feeding behavior. In- jections at the beginning of each meal of either approximately 67 U of insulin or 0.71 mg of growth hormone did not influ- ence feeding behavior. Injections of epi- nephrine of about 6 mg per meal, but not 0.07 or 1.09 mg per meal, reduced feed intake; the injections were continuous throughout the approximately )0-minute meals. Neither injections of 1.23 mg per meal of norepinephrine nor 2.6 mg or 15.3 mg per meal of hydrocortisone depressed feeding. Injections of 34.2 mmoles of ly- sine or 36.2 mmoles per meal of glyeine reduced feed intake slightly; however, 16.8 mmoles per meal of alanine had no effect on feeding. Since feeding behavior was lit- tle affected by the large metabolic and physiological changes caused by the hor- mones, none of those tested is acting as intermediaries in the hunger-satiety control system. It is also suggested that because of the combination of effects of the various hormones tested, plasma free fatty acids probably do not affect feed intake. The large amounts of )ysine and glycine re- quired to produce the moderate depression of feed intake is evidence that at least these amino acids probably have little role in hunger and satiety.