Manganese Nutrition of the pig

Four experiments involving 104 pigs were conducted to study different aspects of manganese (Mn) nutrition in swine. In the first experiment, a basal diet (16.2 ppm Mn) and basal diet supplemented with 10 ppm of Mn from MnS04·H20, HnCO) or MnO uere compared for Mn availability to.the growing pig. Growth .rates were equal on all diets. Mn availability as measured by Mn balance data and tissue Mn concentrations indicated that Mn from the supplemented diets was more available than that from the basal diet. Mn retention, as a percent of intake, was higher on M" from the supplemented diets than the basal diet. Regardless of dietary Mn source, over 90% of excreted Mn was recovered in the feces. Within the supplemented diets, Mn was essentially equally available to the growing pig. Hemoglobin, hematocrit, serum Mn and serum alkaline phosphatase did not differ significantly due to dietary treatment. In the second experiment, flux patterns across the wall of the gastrointestine of Mn from different sources was studied. Net absorption of Mn from the basal diet was evident in two sections of the gut; the stomach and the cecum, whereas Mn from the supplemented diets was apparently absorbed in the stomach, cranial small intestine and cecum. The net cecal absorption,of Mn from the basal diet was higher than that of Mn from the supplemented diets. Net Mn secretion in the caudal small intestine and the rectum was much higher on the supplemented than on the basal diet, but this trend was reversed in the colon. The pH values of the gut contents from different sections of the tract were not significantly different between dietary treatments. In the third experiment, two ratios of Ca to P, two levels of Ca and P and two levels of Mn were studied using a factorial feeding trial. Mn supplementation significantly increased heart Mn levels and significantly depressed rib Ca and Mg values. Mn supplementation did not affect serum Ca, inorganic P, Mg and alkaline phosphatase levels. Dietary Mn levels had no significant effect on rib and metacarpal physical measurements, breaking strength and related parameters. A 2 to I Ca to P ratio significantly (P<0.05) depressed rib Mn content. The increased levels of Ca and P supplementation significantly (P<0.01) increased rib, pancreas and serum Mn levels but significantly (P<0.01) depressed metacarpal Mn concentration. There was a significant (P<0.05 to P<0.05) interaction between levels of Ca and P and ratios of Ca to P on the levels of serum, liver and pancreas Mn, and on metacarpal Mn values. High levels of Ca and P in both ratios had a depressing effect on metacarpal Mn concentration. Feeding Mn along with Ca and P, in a 2 to I ratio, increased liver Mn. Metacarpal Mg was depressed when Ca and P were given in a I to 2 ratio. The interaction between Ca and P levels and Mn levels was significant (P<0.05) with respect to rib ash content, Ca and P, metacarpal Mn and serum inorganic P. With lower Ca and P levels, Mn supplementation increased metacarpal Mn and serum inorganic P but depressed rib ash, Ca and P concentration. The significant effects of Mn supplementation on rib Mg, metacarpal internal vertical diameter and heart and serum Mn u~8appeared when Ca and P supplements were also fed. The 3-way interaction between level of Ca and P, ratio of Ca to P and level of Mn was significant (P<0.05) relative to rib and serum Mn levels, pancreas dry matter and metacarpal Mg content and elasticity. With high or low Ca and P levels in a 2 to 1 ratio, Mn supplementation increased rib and serum Mn and pancreas dry matter but depressed metacarpal elasticity. With low Ca and P levels in a 1 to 2 ratio, Mn supplementation increased serum and metacarpal Mn, but high Ca and P levels in the same ratio depressed rib and serum Mn, metacarpal Mg and pancreas dry matter and increased metacarpal elasticity. Mn supplementation produced more nearly normal histologic structure of the epiphysis than the basal diet, but animals on high Mn levels had significantly (P<0.05) less compact bone in the diaphysis. However, the thickness of the epiphyseal cartilagenous plate was not affected. There was a significant (P<0.05) interaction between Ca to P ratio and Mn level on the histology of the epiphysis. The interaction of diet Mn with Ca and P levels was significant (P<0.05) in relation to the thickness of the epiphyseal cartilagenous plate. These changes were not typical of rickets but were changes in which there was failure of production of compact bone in the region of the diaphysis. However, the deleterious effects on weight gain, feed efficiency and histology of bone of a low dietary P level (0.35%) from soybean meal were much more pronounced than the effects of excessive dietary levels of Ca and P or of an inverse Ca to P ratio, regardless of dietary Mn supplementation. In the fourth experiment, the Mn requirements of the baby pig born of sows fed a low Mn diet were determined using three dietary Mn concentrations. Growth, Mn balance data and serum Mn concentration were used as measures of sufficiency. Average daily gain, serum Mn, Mn retention, fecal Mn excretion and urinary Mn excretion as percent of intake were significantly (P<0.01 or P<0.05) different between dietary treatments. The average daily gain and feed efficiency were highest on 2.67 ppm Mn in the diet. Mn intake was highly correlated with serum Mn and serum alkaline phosphatase activity but not with average daily gain and feed efficiency. Mn retention as percent of intake had very high negative correlations with feed efficiency and urinary Mn excretion as percent of intake. Fecal and urinary Mn excretion as percent of intake was significantly higher on the basal diet (0.46 ppm Mn). There was a negative Mn retention on this diet. Serum Mg levels substantially declined in pigs on the basal diet 28 days after the start of the experiment. Average daily gain was positively related to Mn retention as percent of intake and negatively related to fecal Mn excretion as .percent of intake. Mn retention and fecal Mn excretion, both as percent of intake, were much more highly correlated with growth rate than absolute Mn intake, excretion and retention and the serum parameters examined. Based on all criteria examined, the dietary Mn requirements of the baby pig on a semipurified diet are probably between 3 and 6 ppm.