Performance of dairy cows fed trace minerals in three roughage feeding schemes

Ninety crossbred (Holstein x Red Sindhi) dairy cows of 1-60, 61-180, and 181 days up to lactation were assigned to one of two trace mineral supplementation levels (with or without) and one of three roughage feeding schemes (corn silage feeding, corn silage plus forage consumed by cows when night grazing and forage consumed by cows in day and night grazing). The supplemental trace mineral mixture provided 60 mg Cu, 41 mg Zn, 150 mg Mn, 150 mg Fe, 15 mg Co and 14 mg I per head per day. Soil, feed, milk and blood plasma were analyzed for Cu, Zn, Fe, and Co. All cows were fed with the same concentrate which was found to contain high level of Fe (589.53 ppm). Soil in all areas contained low level of Mn (4.50 ppm), but high Mn was found in para grass (187.37 ppm). All grass species had low Zn (26.09 ppm). Corn silage had low Zn (24.98 ppm) and Mn (19.98 ppm). At 1-60 days of lactation corn silage feeding compared with the other two groups caused a significant decrease (P.05) in milk production (11.89 vs. 13.81 and 13.50 kg/head/day), but signficantly increase (P.05) in milk Cu level (0.25 vs 0.18 and 0.12 microgram/ml) and in blood plasma Cu level (1.41 vs. 0.61 and 0.73 microgram/ml). The blood hemoglobin level appeared related to the milk and blood plasma Cu levels. At 1-60 days of lactation trace minerals supplementation caused significantly lower (P.05) milk production compared to those fed corn silage without trace minerals (10.69 vs. 13.09 kg/head/day) and slightly lower (P.05) than that of the cows on corn silage plus forage (12.87 vs. 14.74 kg/head/day). Generally the percentage of fat, protein, and total solids at the various stages of lactation was not influenced by supplementation. Trace mineral supplementation had no significant effects (P.05) on concentrate intake, and conversion efficiency, trace mineral levels of milk and plasma, hemoglobin, hematocrit, and red blood cell levels. Trace minerals supplementation lengthened the interval from calving to first service of 98 days compared to 63 days without trace minerals for cows on day and night grazing. Likewise, the conception and pregnancy rates in this roughage feeding scheme were higher for those fed without trace minerals. The same trends were observed for cows fed corn silage during the daytime and forage obtained during night grazing