Effects of biotin and high copper levels on performance and immune response of weanling pigs.

Weanling crossbred pigs (n = 216, 6.9 kg initially) were used in three 5-wk trials to evaluate the effect of supplemental biotin (0, 220, 440 and 880 ppb) and Cu (0, 200 and 400 ppm) on performance, hemoglobin concentrations, serum and liver Cu levels and immune response (humoral and cell-mediated). Feeding 200 ppm Cu increased growth rate (P less than .01) and feed intake (P less than .01) during the 5-wk trials; 400 ppm Cu depressed growth and feed intake after wk 2. Efficiency of feed utilization, however, was improved (P less than .05) when either 200 or 400 ppm Cu diets were fed. Whereas supplemental biotin generally did not affect pig performance, an interaction (P less than .01) during the first 2 wk was detected; ADG and feed intake were highest for 200 and 400 ppm Cu dietary levels in combination with the 440 and 880 ppb biotin levels. Hemoglobin concentration was depressed (P less than .01) when 400 ppm Cu was fed, and liver Cu levels were increased (P less than .01) 8- and 35-fold for pigs fed 200 and 400 ppm supplemental Cu, respectively. Although the magnitude of the immune response was small and inconsistent, diets containing 220 and 440 ppb biotin seemed to increase the immune response to sheep red blood cells, but 880 ppb biotin appeared to depress the response; there was no effect of biotin level on lysozyme titers. Addition of Cu to the diet tended to depress the immune response to lysozyme and phytohemagglutinin but did not affect sheep red blood cells.