Effect of a rumen-protected niacin product on lactation performance by dairy cows during summer in Wisconsin

The objective of this study was to evaluate the effect of a rumen-protected niacin product (NiaShure, Balchem Corp., New Hampton, NY) on lactation performance by dairy cows during the summer in Wisconsin. Eighty lactating dairy cows (63 ± 29 DIM) were used in a 10-wk lactation trial (a 2-wk pretreatment covariate period followed by an 8-wk treatment period). Cows were stratified by breed, parity, and DIM and randomly assigned to 10 pens of 8 cows each. Pens were assigned randomly to either control or 12 g/d per cow rumen-protected niacin TMR. Ambient temperature and humidity were monitored weekly to calculate temperature–humidity index, and individual cow rectal temperatures were measured weekly to characterize heat-stress conditions during the experiment. Milk yield, milk composition, milk component yields, DMI, BW, and rectal temperature were unaffected (P > 0.10) by treatment. Under summer conditions in Wisconsin, dietary supplementation with rumen-protected niacin at 12 g/d per cow did not affect (P > 0.10) lactation performance or body temperature of dairy cows.