Effect of Supplementing Distillers Grain or Corn on Performance of Cows Grazing Spring Pasture during the Breeding Season

In a 2 yr study 180 lactating cows (2 to 10 yr old) grazing pastures dominated by smooth bromegrass and Kentucky bluegrass near Brookings, SD received 3 supplemental treatments for 48 d beginning in mid May. Cows received 4.6 lb DM of dried distillers grains with solubles (DDGS), 4.3 lb corn DM, or no supplement daily, starting approximately 14 d prior to the start of the breeding season. Cows were bled weekly for 5 wk beginning 1 wk prior to the beginning of the treatment period. Serum was analyzed for progesterone concentration to determine the onset of cyclicity. While supplemented cows did tend to have higher ADG than cows that received no supplement, supplementation did not improve any measure of reproduction. Calf growth rate was not affected by supplementation. The results were similar when only 2 and 3 yr olds were included in the analysis. Under the conditions of this study, it is not beneficial to supplement cows with DDGS or corn to improve cow reproductive performance or calf performance.