Evaluation of various sources of corn dried distillers grains plus solubles for lactating dairy cattle.

The objectives of this study were to evaluate the effects of feeding dried distillers grains plus solubles (DDGS) from different sources on milk production and composition in dairy cows. Eight multiparous and 4 primiparous Holstein cows were used in a replicated 4 x 4 Latin square design with 28-d periods. Treatments consisted of total mixed diets containing no DDGS (CON), or DDGS from source 1 (DDGS-1), source 2 (DDGS-2), or source 3 (DDGS-3) at 20% of diet dry matter. The processing of DDGS-2 and DDGS-3 was intended to decrease heat damage and improve nutritional quality. The DDGS in the diets replaced a portion of the ground corn and soybean meal, allowing them to be isonitrogenous at 16% crude protein. All diets had a forage-to-concentrate ratio of 55:45. Dry matter intake (21.4 kg/d) did not differ among diets, but cows fed diets containing DDGS had greater yields of milk (34.6 vs. 31.2 kg/d), 4% fat-corrected milk (32.7 vs. 29.6 kg/d), and energy-corrected milk (35.4 vs. 32.3) compared with cows fed the CON diet. Feed efficiency was greater in cows fed DDGS compared with CON (1.78 vs. 1.63). Milk fat yield was greater in cows fed DDGS compared with those fed CON (1.26 vs. 1.14 kg/d). Milk protein percentages (3.28, 3.13, 3.19, and 3.17% for CON, DDGS-1, DDGS-2, and DDGS-3, respectively) were greater for CON vs. DDGS and tended to be lower for DDGS-1 than for DDGS-2 and DDGS-3. Milk protein yields tended to be greater for cows fed DDGS than for those fed CON (1.09 vs. 1.02 kg/d). Concentrations of milk urea nitrogen were lower in cows fed DDGS compared with CON (9.36 vs. 10.6 mg/dL). Feeding DDGS decreased arterial plasma concentrations of Arg, Ile, Lys, and Thr and increased His and Leu compared with CON. Arterial plasma from cows fed DDGS-2 and DDGS-3 had greater concentrations of Ile, Trp, and Val compared with DDGS-1. In all diets, Lys, Met, and Phe were the first 3 limiting amino acids for protein synthesis with Lys being first limiting in DDGS-1 and DDGS-3 and Met being first limiting for CON and DDGS-2. Inclusion of DDGS did not affect the molar proportions of ruminal acetate or propionate compared with CON. Ruminal proportions of butyrate were lower in CON compared with DDGS. Total concentrations of VFA were greater in CON compared with DDGS. The concentrations of rumen ammonia were greater in CON (7.2 mg/dL) compared with DDGS (4.5 mg/dL). Overall, the source of DDGS used in this study did not affect lactation performance.