Protein Deprivation in Primates: III. Cage Activities and Chain-Pulling Behavior of Adult Rhesus Monkeys Maintained on Low-Protein Diets

Abstract

Three groups of adult female rhesus monkeys, maintained on low-protein diets (3-gm, I-gm, and 2-gm protein per kg body weight) were compared with a control group (4-gm protein per kg body weight) on a number of spontaneous cage activities and chain-pulling behavior. Although the deprived animals lost body weight and muscle tissue and they became deficient in essential amino acids and plasma albumin, they maintained their normal posture and continued to move about, vocalize, eat, drink, etc., as such monkeys usually do in their home cages. However, several specific behavioral deficiencies were revealed: reduced face and head movements, fewec eye contacts, and less chain pulling. It was concluded that the level of protein deprivation induced i n this study depletes the animals' energy resources and produces a lowered anxiety threshold, so that certain additional behavioral demands cannot be supported even though routine cage activities are not impaired.Many years ago Hitchcock ( 1928) found that consumption of a low-protein diet over a relatively long period of time depressed the general activity of the adult white rat. Since chat time, numerous studies (summarized by Brozek & Vaes, 1961, pp. 74-78; Scrimshaw & Gordon, 1968, pp. 168-250) have generally confirmed these results. Rodents, dogs, and pigs were typically Ss in these investigations and their performance was usually impaired within a variety of experimental situations by diets containing less than 1 4 to 18% protein. Although much of this work employed learning and problem-solving indices of behavioral effects, ic was often observed that the animals were apathetic or sluggish, exhibited low levels of curiosity, or lacked responsiveness, even when errors and/or time were unaffected.More recently, non-human primates have been committed to this research effort with an emphasis on the motivational aspects of behavior, but concerned only with the early (infant and adolescent) period of life (Kerr & Waisman, 1968; Zimrnermann & Strobel, 1969; Strobe1 & Zimrnermann, 1971, 1972. In general, the association of protein deprivation with decreased activity and apathetic behavior was confirmed. I n addition, evidence was obtained for increases in fear and avoidance reactions in response to novel conditions (Strobe1 LQ Zimmermann, 1972 ) . These phenomena still remain to be investigated in the mature primate.The present study was designed to determine the effects of relatively longterm low-protein deprivation on general cage activity and the specific task of