The influence of sodium fumarate on rumen fermentation was investigated in vitro using batch and semi-continuous cultures of mixed rumen micro-organisms taken from three sheep receiving a basal diet of hay, barley, molasses, fish meal and a mineral–vitamin supplement (500, 299·5, 100, 91 and 9·5 g/kg DM respectively). Batch cultures consisted of 10 ml strained rumen fluid in 40 ml anaerobic buffer containing 200 mg of the same feed given to the sheep. Sodium fumarate was added to achieve a final concentration of 0, 5 or 10 mmol/l, as a result of the addition of 0, 250 or 500 μmol, equivalent to 0, 200 and 400 g/kg feed. CH4 production at 24 h (360 μmol in the control cultures) fell (P < 0·05) by 18 and 22 μmol respectively (SED 7·5). Total gas production was increased by the addition of fumarate without significant accumulation of H2. Substantial increases in acetate production (92 and 194 μmol; SED 26·7, P < 0·01) were accompanied by increases in propionate formation (212 and 396 μmol; SED 13·0, P < 0·001). Longer-term effects of fumarate supplementation on ruminal fermentation and CH4 production were investigated using the rumen simulation technique (Rusitec). Eight vessels were given 20 g basal diet/d, and half of them received a supplement of fumarate (disodium salt) over a period of 19 d. The response to the daily addition of 6·25 mmol sodium fumarate was a decrease in CH4 production of 1·2 mmol (SED 0·39, P < 0·05), equivalent to the consumption of 4·8 mmol H2, and an increase in propionate production of 4·9 mmol (from 10·4 to 15·3 (SED 1·05) mmol/d, P < 0·01). The inhibition of CH4 production did not decline during the period of time that fumarate was added to the vessels. Thus, the decrease in CH4 corresponded well to the fraction of the fumarate that was converted to propionate. Fumarate had no significant (P > 0·05) effect on total bacterial numbers or on the number of methanogenic archaea, but numbers of cellulolytic bacteria were increased (8·8 v. 23·9 (SED 2·49) × 105 per ml, P < 0·01). Fumarate also increased DM digestibility of the basal diet after 48 h incubation (0·476 v. 0·508 (SED 0·0123), P < 0·05). Thus, it was concluded that sodium fumarate may be a useful dietary additive for ruminants, because it diverts some H2 from CH4 production and because it is able to stimulate proliferation of cellulolytic bacteria and digestion of fibre.

The effects of four diets differing in their for age: concentrate ratio (80:20, 60:40, 40: 60 and 20:80; g/100 g fresh matter) on rumen characteristics, digestibility and digesta flow kinetics were investigated. Alfalfa hay was used as forage and concentrate was composed of barley, soya-bean meal and maize. Diets were prepared by mixing all ingredients and offered to the animals as complete diets. Eight mature Merino sheep, each fitted with a rumen cannula, were offered 1·055 kg dry matter per day of the corresponding diet over two experimental periods. The daily evolution of ruminai pH, volatile fatty acids (VFA) and ammonia nitrogen (N) concentrations were measured. Digestibility was determined by total faecal collection and Cr and Co were used as markers to estimate digesta passage rates. Microbial nitrogen flow at the duodenum (MNDF) was estimated from the urinary excretion of purine derivatives (PD). The apparent digestibility of organic matter increased (P < 0·001) whereas that of all fibrous fractions decreased linearly (P < 0·05) as the proportion of concentrate in the diet increased. Rumen pH decreased linearly (P < 0·001) with increasing proportions of concentrate but total VFA concentrations were unaffected by changes in the diet (P > 0·05). Both liquid and solid digesta outflow rates from the rumen decreased quadratically (P < 0·01) as the proportion of concentrate in the diet increased. The urinary excretion of total N, urea-N and ammonia-N was unaffected (P > 0·05) by changes in the diet. In contrast, the daily urinary excretion of both allantoin and total PD increased quadratically (P < 0·05) with increasing proportions of concentrate. Consequently, the estimated MNDF increased linearly (P < 0·001) from 9·9 g/day on the high forage diet to 14·5 g/day on the high concentrate diet.

No abstract

The influence of peptides and amino acids on ammonia assimilation and de novo synthesis of amino acids by three predominant noncellulolytic species of ruminal bacteria, Prevotella bryantii B14, Selenomonas ruminantiumHD4, and Streptococcus bovis ES1, was determined by growing these bacteria in media containing 15NH4Cl and various additions of pancreatic hydrolysates of casein (peptides) or amino acids. The proportion of cell N and amino acids formed de novo decreased as the concentration of peptides increased. At high concentrations of peptides (10 and 30 g/liter), the incorporation of ammonia accounted for less than 0.16 of bacterial amino acid N and less than 0.30 of total N. At 1 g/liter, which is more similar to peptide concentrations found in the rumen, 0.68, 0.87, and 0.46 of bacterial amino acid N and 0.83, 0.89, and 0.64 of total N were derived from ammonia by P. bryantii, S. ruminantium, andS. bovis, respectively. Concentration-dependent responses were also obtained with amino acids. No individual amino acid was exhausted in any incubation medium. For cultures of P. bryantii, peptides were incorporated and stimulated growth more effectively than amino acids, while cultures of the other species showed no preference for peptides or amino acids. Apparent growth yields increased by between 8 and 57%, depending on the species, when 1 g of peptides or amino acids per liter was added to the medium. Proline synthesis was greatly decreased when peptides or amino acids were added to the medium, while glutamate and aspartate were enriched to a greater extent than other amino acids under all conditions. Thus, the proportion of bacterial protein formed de novo in noncellulolytic ruminal bacteria varies according to species and the form and identity of the amino acid and in a concentration-dependent manner.

The present study was designed to describe the effects of early feed restriction of Merino lambs on feed efficiency during the fattening period by examining ruminal microbiota and fermentation parameters, gastrointestinal morphology, digestibility or liver proteome. In total, 24 male Merino lambs were randomly assigned to two experimental treatments (n=12 per treatment). Lambs of the first group (ad libitum (ADL)) were kept permanently with the dams, whereas the other 12 lambs (restricted (RES)) were milk restricted. When lambs reached a live BW (LBW) of 15 kg, all the animals were offered the same complete pelleted diet (35 g dry matter/kg LBW per day) until slaughter at a LBW of 27 kg. The RES lambs showed poorer feed efficiency during the fattening period when compared with the ADL group (feed to gain ratio, 3.69 v. 3.05, P<0.001). No differences were observed in ruminal microbiota, fermentation parameters or apparent digestibility. However, the proportion of the small intestine and the length of ileal villi were reduced in the RES lambs. In total, 26 spots/proteins were identified in the liver proteomic profile, with significant differences (P<0.05) between experimental treatments, suggesting a higher catabolism of proteins and a reduction in β-oxidation of fatty acids in RES lambs when compared with the ADL animals. In conclusion, early feed restriction of Merino lambs during the suckling period promotes long-term effects on the small intestine and the proteomic profile of the liver, which may influence the metabolic use of nutrients, thus negatively affecting feed efficiency during the fattening phase.