The Microflora and Concentrations of Volatile Fatty Acids in The Rumen of Cattle Fed on Single Component Rations

Abstract

The composition of the rumen microflora and the volatile fatty acids were examined in cattle free-grazing on grass or stall-fed on hay, grass pellets, oats or dried beet pulp with molasses. Total and viable counts of anaerobic bacteria were highest on the grass feeding, but viable counts as a percentage of total counts were highest when oats or beet pulp with molasses were fed. Counts of cellulolytic bacteria were lowest on these latter 2 diets, and highest on grass or grass pellet diets. Studies of the anaerobic flora showed that the composition in animals fed on grass pellets resembled more that found in animals free-grazing on grass than in those fed on hay. Counts of aerotolerant bacteria were only a small percentage of the total count, but were highest on the hay diet. On this latter diet and on grass-feeding the streptococci (identified as Streptococcus bovis) were predominant, but contrary to expectation, streptococci were found only in small numbers on the oats diet, where coryneform rods were the major type present. Although a period of 4–6 weeks was allowed for the animals to adapt to the feeds, the 2 periods of feeding on oats and dried beet pulp with molasses markedly affected the composition of the rumen flora in the subsequent periods of feeding grass pellets and hay. Ruinen volatile fatty acid analysis showed a propionogenic effect of oats and the highest percentage of butyric acid when beet pulp with molasses was fed. The expected propionogenic effect of grass pellets was not observed.

Sammendrag

Sammensætning af vommens bakterieflora og indhold af flygtige fedtsyrer undersøgtes hos køer fodret udelukkende med græs, græspiller, hø, havre eller snitfoder. Totaltal og kolonital af anaerobe bakterier var højest hos græsfodrede køer, medens kolonital udtrykt som procent af totaltal var størst i perioderne med havre og snitfoder. Antallet af cellulolytiske bakterier var størst ved fodring med træstofrige fodermidler. Aerotolerante bakterier, som kun udgjorde en lille procentdel af det totale bakterietal, var højest hos høfodrede køer. Ved fodring med hø og græs var streptokokker (identificeret som Streptococcus bovis) dominerende, hvorimod der ved fodring med havre, hvor coryneforme stave dominerede, fandtes et uventet lavt antal streptokokker. Skønt overgangsperioderne varede 4–6 uger, påvirkede havre og snitfoder bakteriefloraens sammensætning i de efterfølgende perioder med græspiller og hø. Den molære fordeling af flygtige fedtsyrer viste den højeste procent eddikesyre ved fodring med græsmarksprodukter. En propionogen effekt af fodring med græspiller kunne, i modsætning til fodring med havre, ikke påvises. Den største molprocent af smørsyre fandtes ved fodring med snitfoder.