Effects of replacing wild rye, corn silage, or corn grain with CaO-treated corn stover and dried distillers grains with solubles in lactating cow diets on performance, digestibility, and profitability

The objective of this study was to measure the effects of partially replacing wild rye (Leymus chinensis; WR), corn silage (CS), or corn grain (CG) in dairy cow diets with CaO-treated corn stover (T-CS) and corn dried distillers grains with soluble (DDGS) on performance, digestibility, blood metabolites, and income over feed cost. Thirty tonnes of air-dried corn stover was collected, ground, and mixed with 5% CaO. Sixty-four Holstein dairy cows were blocked based on days in milk, milk yield, and parity and were randomly assigned to 1 of 4 treatments. The treatments were (1) a diet containing 50% concentrate, 15% WR, 25% CS, and 10% alfalfa hay (CON); (2) 15% WR, 5% CG, and 6% soybean meal were replaced by 15% T-CS and 12% DDGS (RWR); (3) 12.5% CS, 6% CG, and 5% soybean meal were replaced by 12.5% T-CS and 12%DDGS (RCS); (4) 13% CG and 6% soybean meal were replaced by 7% T-CS and 13% DDGS (RCG). Compared with CON treatment, cows fed RCS and RCG diets had similar dry matter intake (CON: 18.2±0.31kg, RCS: 18.6±0.31kg, and RCG: 18.4±0.40kg). The RWR treatment tended to have lower dry matter intake than other treatments. The inclusion of T-CS and DDGS in treatment diets as a substitute for WR, CS, or CG had no effects on lactose percentage (CON: 4.96±0.02%, RWR: 4.97±0.02%, RCS: 4.96±0.02%, and RCG: 4.94±0.02%), 4% fat-corrected milk yield (CON: 22.7±0.60kg, RWR: 22.1±0.60kg, RCS: 22.7±0.60kg, and RCG: 22.7±0.60kg), milk fat yield (CON: 0.90±0.03kg, RWR: 0.86±0.03kg, RCS: 0.87±0.03kg, and RCG: 0.89±0.03kg), and milk protein yield (CON: 0.74±0.02kg, RWR: 0.72±0.02kg, RCS: 0.73±0.02kg, and RCG: 0.71±0.02kg). Cows fed the RWR diet had higher apparent dry matter digestibility (73.7±1.30 vs. 70.2±1.15, 69.9±1.15, and 69.9±1.15% for RWR vs. CON, RCS, and RCG, respectively) and lower serum urea N (3.55±0.11 vs. 4.03±0.11, 3.95±0.11, and 3.99±0.11mmol/L for RWR vs. CON, RCS, and RCG, respectively) than cows fed other diets. No significant differences were noted in apparent neutral detergent fiber digestibility among the treatments. Compared with CON treatment, the RWR, RCS, and RCG treatments generated an additional $0.77, $0.70, and $0.81 income over feed cost per cow per day, respectively. In conclusion, feeding diets containing a portion of T-CS and DDGS can improve profitability of the treatment groups without negatively affecting the lactation performance of mid- to late-lactation cows.