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

The objective of this study was to investigate metabolic alterations in young ruminating calves associated with the sudden introduction of readily fermentable 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 contained either 71 or 81% total digestible nutrients (TDN) and 15 or 20% crude protein 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 frequent intervals over a subsequent 2-d period. Hooves were examined for abnormalities and the orientation of the pedal bone radiographed prior to the experiment, 48 to 72 h into the experiment and at 3 and 7 mo later. Calves responded 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 fatty acid concentration decreased as pH declined. Whole blood L-lactate did not 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.