Effects of dietary concentrates on rumen digestion of fibrous feedstuffs

Abstract

Three mature rumen cannulated steers were given Penniseteum purpureum forage (60–65 days regrowth) ad libitum, with and without a concentrate supplement (1.0 kg maize bran dry matter (DM) per 100 kg live weight). Eight feedstuffs (bagasse, bagasse treated with 8% NaOH, Penniseteum purpureum, Digitaria swasilandensis, dried brewers grains, Canavalia ensiformis hulls and leaf and sweet potato forage) were incubated in nylon bags in the rumen and the disappearance of DM insoluble in 0.15 M NaCl after 0, 8, 16, 24 and 72 h was measured. The half-time ( T 1 2 ) of disappearance of insoluble DM calculated for the first 24 h of incubation in the rumen was increased by dietary concentrates and this increase ( ΔT 1 2 ) was related to the T 1 2 of DM disappearance measured in steers given forage alone ( T 1 2 ) and to the cellulose content of the insoluble DM in each feedstuff. Also, separate linear relationships between ΔT 1 2 T 1 2 and the cellulose content of insoluble DM were observed for the five graminaceous and the three non-graminaceous feedstuffs studied. The experiment showed that concentrate supplementation reduced fibre digestion in the rumen more for graminaceous than non-graminaceous forages and this reduction was positively related to the rate of DM digestion in the absence of concentrates and to the cellulose content of the forage.