Influence of fumaric acid on ruminal parameters and organ weights of growing bulls fed with grass or maize silage.

The influence of the potential methane reducer, fumaric acid (FA), on ruminal parameters, the rumen wall and organ weights was investigated in a long-term study with growing bulls. In all, 20 bulls were fed with maize or grass silage as roughage, and with concentrate with or without 300 g FA per animal and day during the whole fattening period. After slaughtering, the organs were weighed and blood serum was analysed for glucose, ß-hydroxybutyric acid (BHB) and non-esterified fatty acid concentration. The ruminal fluid was analysed for short-chain fatty acids, ammonia-N and the microbial community via single strand conformation polymorphism analysis. The rumen wall was examined histopathologically and results were graded as 'no visible lesions', 'few inflammatory infiltrates', 'some inflammatory infiltrates' or 'several inflammatory infiltrates'. In addition, the dimensions of the rumen villi were measured. The FA supplementation decreased the serum BHB concentration and the butyric acid concentration in the ruminal fluid. The microbial community in the ruminal fluid was not influenced by FA. An interaction between FA and silage type was observed for the inflammation centres counted in the villous area of rumen papillae. This interaction was also observed in the length and surface of the rumen villi. Rumen villi results show that the influence of FA depends on the roughage used in the diet.

Effects of fumaric acid on rumen fermentation, milk composition and metabolic parameters in lactating cows.

The aim of this study was to determine the influence of fumaric acid (FA) on ruminal fermentation and its effects on the acid-base balance of seven ruminally and duodenally fistulated multiparous German Holstein cows. The experiment was conducted in a change-over design with three periods in which the animals were randomly arranged in one of three treatments: Control (C; without FA), 300 or 600 g FA per day. The diets consisted of 7.4 kg DM grass silage, 4.2 kg concentrate mixture and 0, 300 or 600 g FA or wheat starch as isocaloric compensation per day and cow. FA supplementation decreased the rumen pH, acetic acid and butyric acid and increased propionic acid in rumen fluid. The results of the single-strand conformation polymorphism analysis (SSCP) did not show an influence of FA on the microbial population in the rumen. The beta-hydroxybutyrate (BHB) concentration in blood and the pH of the urine decreased, while the blood gases were unaffected by supplementation of the acid. The microbial protein per MJ ME decreased in the duodenum with FA supplementation. The milk fat concentration decreased after addition of FA. We conclude that in this study feeding of up to 600 g FA per day did not result in an acidosis. It seems that up to 600 g FA per day did not have a significant influence on the acid-base balance of dairy cows.