Pancreatic mass, cellularity, and -amylase and trypsin activity in feedlot steers fed diets differing in crude protein concentration

¹ Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1

^* To whom correspondence should be addressed. E-mail: kswanson{at}uoguelph.ca.

	Abstract

Twenty-four yearling beef steers (initial BW = 510 ± 4.9 kg) predominately of Angus breeding were used in a randomized complete block design to determine the effect of dietary CP concentration on pancreatic cellularity, mass, and -amylase and trypsin activity. Treatment diets were formulated to contain 8.8, 11.0, 13.2, and 15.4% CP. Soybean meal and TOP SOY (bypass soybean meal) were used as supplemental protein sources to assure that metabolizable protein intake was increased with increasing dietary CP concentrations. Steers were penned in groups of 4 (1 steer per treatment) and individually fed at 2.5xNE_m requirement using Calan gates for 28 d before tissue collection. Four steers (1 pen) were slaughtered per week. Pancreata were weighed, subsampled, frozen in liquid N₂, and stored at -80°C until analyses for DNA, RNA, and protein concentrations, and -amylase and trypsin activities. Pancreatic weight (g and g/kg BW) did not differ among treatment groups. Pancreatic DNA concentration (mg/g) decreased linearly (P = 0.06) with increasing CP concentration. Pancreatic protein (g/pancreas) increased linearly (P = 0.08) with increasing dietary CP concentration. Pancreatic -amylase activity (U/g, U/mg DNA, U/g protein, U/pancreas, and U/kg BW) increased linearly (P 0.04) with increasing dietary CP concentration. Pancreatic trypsin activity (U/g, U/g DNA, U/g protein, U/pancreas, and U/kg BW) increased linearly (P 0.09) with increasing dietary CP concentration. Pancreatic -amylase and trypsin activity (U/mg RNA) responded quadratically (P 0.09) with the greatest -amylase activity observed in the 13.2% CP treatment. These data indicate that increasing dietary CP concentration decreases pancreatic cell number as well as increases the concentration and content of pancreatic -amylase and trypsin activity. Changes in cell number and size may be important factors regulating digestive enzyme production in cattle pancreas.

Key Words: Beef Cattle, Pancreas, -Amylase, Trypsin, Dietary Protein