Effects of replacing soybean meal with corn gluten meal on milk production and nitrogen efficiency in Holstein cows

The objective of the current study was to determine the effects of partial replacement of soybean meal with corn gluten meal on lactation performance and nitrogen (N) efficiency in lactating Holstein dairy cows. Nine multiparous lactating cows in mid lactation (109 ± 19 days in milk) received three treatments in a 3 × 3 Latin square design for 21 days. The three treatments consisted of i) Ctrl: low protein diet with 15.2% crude protein (CP); ii) SBM: soybean meal-based diet with 18.4% CP; and iii) CGM: soybean meal partially replaced with corn gluten meal with 18.3% CP. Two pre-planned orthogonal contrasts were used to compare the treatments: i) Prot compared Ctrl and average of SBM and CGM to see the effect of increasing protein supplies; and ii) Rep compared SBM and CGM treatments. Increasing CP supplies did not affect dry matter intake, whereas it significantly increased milk protein and lactose yield by 3.6% and 3.3%, respectively. Increasing CP supplies decreased milk nitrogen efficiency (MNE) by 10.9%. The milk yield, milk component yield, milk composition and feed efficiency were similar in the SBM and CGM treatments. Similarly, no difference was observed on dry matter, N and net energy for lactation (NEL) intakes between SBM and CGM treatments. However, MNE significantly decreased by 4.8% in the CGM treatment compared with SBM. The results indicated that soybean meal could be partially replaced with corn gluten meal without negatively affecting productive performance.Keywords: Dairy cows, feed efficiency, nitrogen utilization, production performance, protein sources