Effect of Source of Protein on Zinc Requirement of the Growing Pig

Abstract

Seventy 3-week-old Duroc pigs were fed various proteins and carbohydrates with and without added zinc to determine the effect on the dietary zinc requirement. The pigs receiving the milk proteins (containing 6–18 ppm zinc) with or without added zinc had superior growth (P<.05) and no symptoms of a zinc deficiency were observed. All pigs receiving the soybean protein rations (containing 16–22 ppm zinc) showed typical zinc deficiency symptoms. The addition of 50 ppm zinc to the soybean protein rations alleviated the zinc deficiency symptoms; however, the addition of zinc to the milk protein rations did not improve performance. Two of the four parakeratotic pigs fed a dried skimmed milk ration (16 ppm total Zn) died; however, the other two pigs showed marked improvement in performance within 28 days. When zinc deficient pigs were fed an isolated soybean protein ration (16 ppm total Zn) plus 125 ppm copper, no improvement in performance was observed. In this study the addition of 30% lactose or the autoclaving of the soybean protein did not increase body weight significantly. The cases of parakeratosis were essentially the same in the two treatments but less acute than in the control group. The results indicate that the pigs may have obtained some zinc from the galvanized metal pens. Parakeratotic pigs fed 50 ppm zinc, 450 ppm EDTA and autoclaved isolated soybean protein gained 35, 31 and 42% more than the controls, respectively, however, the differences were not statistically significant. All pigs except those receiving the basal ration showed marked alleviation of the zinc deficiency syndrome.