Influence of Caloric Level and Protein Quality on the Manifestations of Protein Deficiency in the Young Pig

Abstract

Young pigs (approximately three weeks old, average weight 6.3 kg) were used to study the effect of caloric density and protein quality of the diet on the biochemical and anatomical manifestations of protein deficiency. Purified diets containing 5% of protein from casein or wheat gluten and either 3 or 23% fat (corn oil) were fed ad libitum for 14 weeks. A stock diet containing 18% of protein served as the positive control. Casein produced a 182-gm average daily gain in the presence of 3% of fat. Weight gain was similar during the first 8 weeks when casein was fed in the presence of 23% of fat, but weights reached a plateau and remained constant during the remainder of the trial. Wheat gluten failed to support body weight gain at either level of fat. Deficiency symptoms noted were similar to those reported in kwashiorkor in humans. Symptoms were most severe in pigs fed wheat gluten with 23% of fat, and least severe in those fed casein with 3% of fat. The pigs in the former group were emaciated and feeble during the last two weeks, had reduced rectal temperature (P < 0.01) and lower hematocrit (P < 0.01) than the other groups. Hemoglobin was depressed (P < 0.01) with wheat gluten as compared with casein, but total serum protein declined to about 4 gm/100 ml after 6 weeks in all groups and plateaued. Total globulins remained constant in all groups throughout the experiment. Adrenal, heart and liver weghts (as percentage of body weight) were greater in pigs fed wheat gluten than in those fed casein. Bone growth was depressed, especially in gluten-fed pigs, and carcasses showed extensive edema throughout. Pathological changes occurred in all organs and tissues studied, being the most severe in the pigs fed gluten with 23% fat and least severe in those fed casein with 3% fat. Both caloric density and protein quality exerted an effect on the severity of protein deficiency symptoms in the pig. The severity of symptoms was inversely related to the absolute amounts of protein voluntarily consumed daily by each group.