To investigate the influences of dietary riboflavin (RF) addition on nutrient digestion and rumen fermentation, eight rumen cannulated Holstein bulls were randomly allocated into four treatments in a repeated 4 × 4 Latin square design. Daily addition level of RF for each bull in control, low RF, medium RF and high RF was 0, 300, 600 and 900 mg, respectively. Increasing the addition level of RF, DM intake was not affected, average daily gain tended to be increased linearly and feed conversion ratio decreased linearly. Total tract digestibilities of DM, organic matter, crude protein (CP) and neutral-detergent fibre (NDF) increased linearly. Rumen pH decreased quadratically, and total volatile fatty acids (VFA) increased quadratically. Acetate molar percentage and acetate:propionate ratio increased linearly, but propionate molar percentage and ammonia-N content decreased linearly. Rumen effective degradability of DM increased linearly, NDF increased quadratically but CP was unaltered. Activity of cellulase and populations of total bacteria, protozoa, fungi, dominant cellulolytic bacteria, Prevotella ruminicola and Ruminobacter amylophilus increased linearly. Linear increase was observed for urinary total purine derivatives excretion. The data suggested that dietary RF addition was essential for rumen microbial growth, and no further increase in performance and rumen total VFA concentration was observed when increasing RF level from 600 to 900 mg/d in dairy bulls.

An in situ study was conducted on four rumen-cannulated wethers to determine (using 15N infusion techniques) the microbial contamination (mg bacterial DM or crude protein (CP)/100mg DM or CP) and the associated error on the effective degradability of fourteen feeds: barley and maize grains, soyabean and sunflower meals, full-fat soyabean, maize gluten feed, soyabean hulls, brewers dried grains, sugarbeet pulp, wheat bran, lucerne and vetch-oat hays, and barley and lentil straws. The DM or CP contamination in residues (M) fitted to single exponential or sigmoid curves. A general model (M=m (1−e−ft)j) was proposed to match this fit. Asymptotic values (m) varied from 2·84% to 13·3% and from 2·85% to 80·9% for DM and CP, respectively. Uncorrected results underestimated the effective degradability of both DM (P<0·05) and CP (P<0·01). For CP, this underestimation varied from 0·59% to 13·1%, with a higher but unascertainable error for barley straw. Excluding maize grain, the microbial contamination of both DM and CP, and the associated underestimation of the effective degradability of CP, were positively related to the cellulose content of the feed. The error in the effective degradability of CP was also negatively related to the CP content and its apparent effective degradability (R2 0·867). This equation allows easier and more accurate estimates of effective degradability, needed to improve protein-rationing systems.

An in sacco mobile bag technique was used to determine the rate and extent of disappearance of unmolassed sugar-beet pulp, soyabean hulls, hay cubes and an oat hull–naked oats mixture (67:33, w/w) in the foregut and total digestive tract of ponies. Ponies were administered naso-gastrically polyester mesh bags (60×10×10 mm) containing 350 mg feed, in a 3×4 Latin square design. Bags were collected at the ileo-caecal junction (small intestine bag, SIB) and in the faeces (faecal bag, FB) and their residues analysed for proximate constituents and NSP composition and content. DM disappearances from individual bags were fitted to degradation profiles () and effective degradability values determined. Significant differences (P<0·05) in DM, organic matter and crude protein (N×6·25) losses from SIB were noted between feeds with hay cubes and oat hulls–naked oats > sugar-beet pulp and soyabean hulls. Acid-detergent fibre, neutral-detergent fibre and NSP disappearances were small and varied little between feeds. In contrast, FB losses showed significant (P<0·05) differences for all constituents measured with sugar-beet pulp > soyabean hulls > hay cubes > oat hulls–naked oats. Crude protein losses from sugar-beet pulp and soyabean hulls in FB were significantly higher (P<0·05) than from SIB. FB degradation curves showed degradation to be affected by bag residence time with sugar-beet pulp > soyabean hulls and the effective degradability showed that significantly more (P<0·05) sugar-beet pulp was lost at 40.0 and 60.0 h than for the other three feeds. These results show that sugar-beet pulp and soyabean hulls are rapidly degraded by ponies and could be used as alternatives to hay in equid rations. However, the foregut availability of crude protein from sugar-beet pulp is poor, so a readily digestible source of crude protein should be offered to animals with high protein demands when diets are based on sugar-beet pulp.