Changes in rumen parameters during dietary transitions in feedlot cattle

Recent Advances in Animal Nutrition in Australia, Volume 15 (2005) Introduction of grain–based diets to cattle can be associated with metabolic diseases such as lactic acidosis. Lactic acidosis is characterised by high concentrations of L– and D–lactate in the rumen, a decrease in rumen pH from approximately 6.4 to below 5.8, and an underlying change in rumen ecology (Owens et al. 1998). The main bacterial species responsible for increased concentrations of lactic acid is thought to be Streptococcus bovis, but other species such as lactate–producing Lactobacilli sp. and possibly Selenomonas ruminantium have also been suggested as playing an important role (Tajima et al. 2001). This paper reports changes in rumen pH and their relationship to L–lactate concentrations in feedlot cattle during transition to high energy diets. Eight yearling animals from a March/April calving group of cattle and another eight from a June/July calving group were sampled during a period of introduction to high energy diets in feedlots at Vasse Research Station after they were all weaned in January. Sixteen cattle were also sampled from a commercial feedlot near Donnybrook which fed hay and grain separately. Rumen samples were taken via rumen tubes on days 0, 3, 7, and 14 after introduction to their feedlot diets. Rumen pH values were measured immediately and then the samples were stored at –80°C for rumen L– lactate analysis. There was no relationship between rumen L–lactate concentration and rumen pH in cattle from the commercial feedlot over the range of pH 5.8 to 7.2 (R2 = 0.088). Rumen L–lactate concentrations Changes in rumen parameters during dietary transitions in feedlot cattle