PSIX-7 Grazing toxic endophyte-infected tall fescue does not influence pancreatic or small intestinal digestive enzyme activities in beef steers

Abstract

Abstract The objective of this experiment was to determine the influence of toxic endophyte-infected tall fescue exposure on pancreatic and small intestinal digestive enzyme activities in steers. Twelve fescue-naive beef steers [693 ± 42.7 kg of body weight (BW)] were stratified by BW and randomly assigned within BW ranks to graze non-toxic endophyte-infected tall fescue (NTE, n = 6; 0.01 ± 0.009 mg ergovaline + ergovalinine/kg) or toxic endophyte-infected tall fescue (TE, n = 6; 0.50 ± 0.048 mg ergovaline + ergovalinine/kg) pastures for 84 d. After the grazing period, steers were weighed and then slaughtered in three groups for tissue collection. A 1-m segment of the small intestine was collected 5-m distal to the pyloric sphincter. Subsamples of the small intestinal mucosa and pancreas were collected, homogenized in saline, and assayed for protein concentration. Pancreatic and small intestinal digestive enzyme activities were assayed. Data were analyzed using the GLM procedure of SAS as a randomized complete block design for effects of treatment and slaughter group (blocking factor). Steers grazing NTE pastures had a greater (P < 0.001) average daily gain (0.282 vs -0.631 kg/d) and final BW at slaughter (739 vs 620 kg) than steers grazing TE pastures. Small intestinal segment mass and mucosal density (P ≥ 0.16) were not influenced by treatment. Grazing TE pasture did not influence (P ≥ 0.21) pancreatic or small intestinal protein concentrations. Pancreatic α-amylase and trypsin activity per gram pancreas (P ≥ 0.21) or per gram pancreatic protein (P ≥ 0.30) were not influenced by fescue treatment. Small intestinal glucoamylase, isomaltase, and maltase activities did not differ between steers grazing NTE or TE pastures when expressed per gram of intestinal tissue (P ≥ 0.47) or per gram of intestinal protein (P ≥ 0.60). These data indicate that decreased gains observed in cattle consuming TE are not a result of decreased pancreatic or small intestinal digestive enzyme activities.