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Performance of Dairy Cows Fed Trace Minerals in Three Roughage Feeding Schemes
Dissertation Abstract:
Ninety crossbred (Holstein x Red Sindhi) cows which were 1-60, 61-180, and 181 days up into their 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 (in mg/head/day) 60 copper (Cu), 41 zinc (Zn), 150 manganese (Mn), 150 iron (Fe), 15 cobalt (Co), and 14 iodine (I). 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<0.05) in milk production (11.89 vs 13.81 and 13.50 kg/head/day), but significant increase (P<0.05) in milk Cu level (0.25 vs 0.18 and 0.12 g/ml) and in blood plasma Cu level (1.41 vs 0.61 and 0.73 g/ml). The blood hemoglobin level appeared related to the milk and blood plasma Cu levels.
At 1-60 days of lactation, trace mineral supplementation caused significantly lower (P<0.05) milk production compared to those fed with corn silage without trace minerals (10.69 vs 13.09 kg/head/day) and slightly lower (P<0.05) 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 effect (P<0.05) on concentrate intake, and conversion efficiency, trace mineral levels of milk and plasma, hemoglobin, hematocrit, and red blood cell levels.
Trace mineral supplementation lengthened the interval from calving to first service of 98 days compared to 63 days without trace minerals for cows that grazed day and night. 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 with corn silage during the daytime and with forage obtained during night grazing. Data suggest that these trace minerals are not recommended for supplemental feeding to cows at the Dairy Training Research Institute (DTRI) in UPLB.