The effect of dry corn gluten feed on chewing activities and rumen parameters in lactating dairy cows

Abstract

The objectives of this research were to evaluate the effects of increasing levels of dry corn gluten feed (DCGF) on dry matter intake (DMI), chewing activity, and rumen fermentation when used to replace a portion of corn silage in diets for lactating Holstein cows. Eight lactating Holstein primiparous cows averaging 98&plusmn;20 d in milk and weighing 515&plusmn;20 kg were randomly assigned in a 4x4 Latin square design with 4 week periods. Dietary treatments were 1) a control diets (C) of 50% forage (corn silage and wheat straw, 35%, 15% DM basis, respectively), 2) a low DCGF diet (L-DCGF) in which 10% of the same corn silage was replaced by DCGF, 3) a medium DCGF diet (M-DCGF) in which 18% of the same corn silage was replaced by DCGF, and 4) a high DCGF diet (H-DCGF) in which 25% of the same corn silage was replaced by DCGF. The proportion of particles retained on the 19.0 mm screen and physical effectiveness factor of the HDCGF was lower (P<0.05) than in the other groups. Increasing the level of DCGF did not change DMI. Cows fed the C diet spent significantly more time ruminating and chewing per day compared with the MDCGF and H-DCGF diets (483.88, 435.63, 431.25 min/d, P<0.05; and 818.38, 753.00, 745.75 min/d respectively, P<0.05). Cows fed the C diet had ruminal pH values higher than the cows fed the M-DCGF and H-DCGF diets (6.02, 5.95, and 5.91, P<0.05). The total volatile fatty acid and propionate levels of H-DCGF fed cows were higher than the control (P<0.05). The changes in acetate (A) and propionate (P) concentrations resulted in a decrease in A/P ratio, when corn silage was replaced by DCGF, which led to a reduction in the particle size of the diets (P<0.05). It was concluded that when ratio 18 and 25% DCGF were substituted for corn silage, rumination time, chewing activities and ruminal pH are negatively affected. The optimum level for the addition of DCGF was found to be below 18% of the diet for a healthy rumen and a chewing behaviour in dairy cows.