ARS | Publication request: The effect of brown midrib corn silage and dried distillers grains and solubles on milk production nitrogen utilization and microbial community structure in dairy cows

Submitted to: Canadian Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2012
Publication Date: N/A

Interpretive Summary: The U.S. ethanol industry provides many co-products that may be utilized as animal feedstuffs. One of the most widely used co-products is dried distillers grains with solubles (DDGS). When DDGS is included in dairy rations, it typically replaces soybean meal as a source of protein; moreover, DDGS can serve as a source of energy as it replaces corn and forages. Many corn hybrids have dual purposes; that is, they are grown for grain or forage. However, forage-specific hybrids also exist. Hybrids possessing the brown midrib 3 mutation (bm3) of corn (Zea mays L.) are characterized by reduced lignin content, which translates into improved fiber digestion in ruminants. In the present study, ruminally canulated cows were fed a variety of corn silage and distillers grains based rations. Co-feeding of brown midrib corn silage and distillers grains improved milk protein production but reduced milk fat.

Technical Abstract: Thirty-six Holstein cows, four of which were ruminally cannulated, (mean ± SD, 111 ± 35 DIM; 664 ± 76.5 kg BW) were used in replicated 4×4 Latin squares to investigate the effects of brown midrib (bm3) and conventional (DP) corn silages and the inclusion of dried distillers grains with solubles (DDGS) on milk production and N utilization. In each 28 d period, cows were assigned to one of four treatments that differed by corn silage hybrid and inclusion level of DDGS. Treatments were DP corn silage and 0% DDGS, bm3 corn silage and 0% DDGS, DP corn silage and 30% DDGS, and, lastly, bm3 corn silage and 30% DDGS. Compared to cows consuming DP corn silage, dry matter intake was greater for cows consuming bm3 (25.8 vs. 24.4 ± 0.47 kg). Additionally, DMI increased for cows consuming DDGS compared to those consuming the zero control (25.9 vs. 24.3 ± 0.47 kg/d for 30 and 0%, respectively). Compared to DP hybrid, total tract fiber digestibility was higher for cows consuming bm3 (32.5 vs. 38.1 ± 1.79%) and DDGS (40.0 vs. 35.2 + 1.76). There was a hybrid by DDGS interaction for total concentration of ruminal volatile fatty acids (VFA) and rumen pH. Specifically, the addition of DDGS to rations containing bm3 corn silage resulted in an increase in concentrations of rumen VFA and, as a result, lowest rumen pH. Milk yield was not affected by treatment and averaged 30.5 ± 1.09 kg/d. Milk protein yield was positively affected by bm3 corn silage and the inclusions of DDGS, with these factors having an additive effect. An interaction between hybrid and DDGS on milk fat was also observed, as the addition of DDGS only reduced milk fat yield when cows consumed bm3 corn silage (1.03, 1.08, 0.84, and 0.78 ± 0.045 kg/d for DP 0% DDGS, bm3 0% DDGS, DP 30% DDGS, and bm3 30% DDGS respectively). Total mass of manure N was not affected by either hybrid or DDGS averaging 386.9 + 14.1 g/d across treatments. However, as a proportion of the total N consumed, manure N was significantly reduced by the inclusion of bm3 corn silage and DDGS (64.1, 57.1, 52.0, 51.2% for DP 0% DDGS, bm3 0% DDGS, DP 30% DDGS, and bm3 30% DDGS respectively). In conclusion, the feeding of bm3 corn silage and DDGS had a positive effect on milk protein yield but a negative effect on milk fat yield. Additionally, although the total mass on N in the manure was not affected, improvements were observed in productive use of N by the lactating dairy cow.