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.

摘要

Effects of partial substitution of clover silage with high starch forages were investigated upon milk production and chemical composition, in vivo digestibility, rumen fermentation pattern and N excretion in dairy cattle. 16 dairy cattle were separated into 2 groups and were assigned to treatments in a 2-period crossover design. 2 forage supplements were used: corn silage (CS); and dry ground corn (DG). All animals received 4.5 kg of concentrate DM per day. Results showed no significant difference between the forage supplements for milk production, while significant differences (P < 0.01) were observed for milk fat, milk protein and N utilization efficiency (42 vs. 4.0 g/kg, 3.5 vs. 3.3 g/kg and 222 vs. 188 g/kg, respectively, for DG and CS). Faecal N excretion did not differ between forage supplements, but urinary N excretion was higher for CS (P < 0.05). No significant differences were observed between treatments for rumen fluid pH or for rumen fluid concn. of ammonium N or of acetic, propionic or butyric acids. DM intake and the in vivo digestibilities of DM, organic matter, acid detergent fibre and neutral detergent fibre were all higher for CS compared with DG.