Effects of forage supplements on milk production and chemical properties, in vivo digestibility, rumen fermentation and N excretion in dairy cows offered red clover silage and corn silage or dry ground corn

This study concerned the effects of partial substitution of clover silage with high starch forages on milk production and chemical composition, in vivo digestibility, rumen\nfermentation pattern and nitrogen excretion of dairy cows. Sixteen dairy cows were\nseparated into two groups and were assigned to treatments in a two-period crossover\ndesign. Two forage supplements were used: corn silage (CS) and dry ground corn (DG).\nAll animals received 4.5 kg of concentrate dry matter per day. Results showed no significant\ndifference between the forage supplements for milk production, while significant\ndifferences (P<0.01) were observed for milk fat, milk protein and nitrogen utilisation\nefficiency (42 v. 4.0 g/kg, 3.5 v. 3.3 g/kg and 222 v. 188 g/kg, respectively, for DG and CS).\nFaecal N excretion did not differ between forage supplements, but urinary N excretion\nwas higher for CS (P<0.05). No significant differences were observed between treatments\nfor rumen fluid pH or for rumen fluid concentrations of ammonium nitrogen\nor of acetic, propionic or butyric acids. Dry matter intake and the in vivo digestibility\nof dry matter, organic matter, acid detergent fibre and neutral detergent fibre were all\nhigher for CS compared with DG.