The effect of slaframine on salivary output and subacute and acute acidosis in growing beef steers2

Abstract

Experiments were conducted to determine 1) the effect of injecting slaframine (SF) on salivary output in growing beef steers and 2) whether increased salivary output after SF injection would inhibit the decrease in ruminal pH that occurs after experimentally induced subacute and acute ruminal acidosis. In Exp. 1 and 2, we measured ruminal pH and salivary output in ruminally and esophageally cannulated beef steers fed an 88% concentrate diet. Injections of 66 or 100 micrograms of SF/kg BW increased salivary flow approximately 50% compared with controls. Those doses were tested in subacute and acute acidosis models using ruminally cannulated beef steers in Exp. 3 and 4, respectively. In these experiments, salivation was assessed indirectly using a visual scoring system. In the subacute acidosis model, SF reduced (P < .10) the decrease in ruminal pH (1.1, .7, and .6 pH units for control, 66, and 100 micrograms of SF/kg BW doses, respectively), and excessive salivation was observed in all SF-injected steers. In the acute acidosis model, there were no differences (P > .10) in ruminal pH at 12 h after injection between control and SF-treated steers. Mean ruminal lactate concentrations for all treatment groups were between 87 and 112 mM. Although treatment with 66 micrograms of SF/kg BW reduced (P < .10) ruminal lactate concentrations, all ruminal lactate concentrations were indicative of acute acidosis. These results indicate that SF will reduce the decrease in ruminal pH associated with subacute acidosis in growing beef steers, but SF does not attenuate acute ruminal acidosis.