Graduate Student Paper Competition: National ADSA Production PhD Oral

The objective of this study was to investigate the effects of concentrations of forages and dried distillers grains with solubles (DDGS) on production of lactating dairy cows. Twelve Holstein cows were assigned randomly to replicated 4 × 4 Latin squares in a 2 × 2 factorial arrangement of treatments. Diets were formulated containing low forage (LF; 41% of diet DM) or high forage (HF; 60% of diet DM) and DDGS at 0 or 18% of diet DM. Forage consisted of 80% corn silage and 20% alfalfa hay (DM basis). Ground corn and soybean feeds were partially replaced by DDGS from 0% DDGS diets to formulate 18% DDGS diets. Average DMI was not affected by diets (Table 1). Milk yield was greater when cows were fed LF compared with HF regardless of the addition of DDGS (43.3 vs. 41.5 kg/d). Milk fat concentration (3.03 vs. 3.38%) were lesser for cows fed LF compared with HF, whereas protein concentration (3.11 vs. 2.98%) and yield (1.34 vs. 1.24 kg/d) were greater for cows fed LF compared with HF. Yields of fat, total solids (TS), and 4% fat-corrected milk (FCM) were not affected by diets. Cows fed HF had greater feed efficiency FCM/DMI) compared with cows fed LF (1.50 vs. 1.43). Overall, there were no interactions of forage and DDGS for any of the measures. Results suggest that the concentration of forage in diets influences the performance of cows, but not the addition of DDGS. Consequently, partially replacing starch from ground corn and protein from soybean feeds with DDGS at either 41 or 60% of forage in the diet did not affect the production of lactating dairy cows. Table 1.