Metabolic alterations associated with an attempt to induce laminitis in dairy calves

The objective of this study was to investigate metabolic alterations in you ng ruminating calves associated with the sudden introduction of readily fer mentable diets in an attempt to induce laminitis. Sixteen dairy bull calves , at 17 wk of age were fed equal amounts of one of four diets that containe d either 71 or 81% total digestible nutrients (TDN) and 15 or 20% crude pro tein in a 2 x 2 factorial with time as a factor. Jugular blood and ruminal fluid were sampled, and hoof temperature was measured postfeeding at freque nt intervals over a subsequent 2-d period. Hooves were examined for abnorma lities and the orientation of the pedal bone radiographed prior to the expe riment, 48 to 72 h into the experiment and at 3 and 7 mo later. Calves resp onded acutely to the 81% TDN diets by inappetence, stiffness, and diarrhea. Ruminal pH was lower and both D- and L-lactate concentrations were greater in the rumens of calves fed the 81% TDN diets. Total ruminal volatile fatt y acid concentration decreased as pH declined. Whole blood L-lactate did no t differ across treatments, but blood D-lactate increased in calves fed the 81% TDN diets, peaking at 32 h (7.2 mM). Hoof temperature responses could not be explained by dietary treatments. Laminitis was not detected despite the reduction of ruminal pH and a manyfold increase in blood D-lactate.