Twenty-four yearling beef steers (initial BW = 510 +/- 4.9 kg) predominantly of Angus breeding were used in a randomized complete block design to determine the effect of dietary CP concentration on pancreatic cellularity, mass, and alpha-amylase and trypsin activities. Treatment diets were formulated to contain 8.8, 11.0, 13.2, and 15.4% CP. Soybean meal and Top Soy (ruminal bypass soybean meal) were used as supplemental protein sources to ensure that MP intake was increased with increasing dietary CP concentrations. Steers were penned in groups of 4 (1 steer per treatment) and individually fed at 2.5x the NE(m) requirement by using Calan gates for 28 d before tissue collection. Four steers (1 pen) were slaughtered per week. Pancreases were weighed, subsampled, frozen in liquid N(2), and stored at -80 degrees C until analyses for DNA, RNA, and protein concentrations, and alpha-amylase and trypsin activities. Pancreatic weight (g and g/kg of 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 alpha-amylase activity (U/g, U/mg of DNA, U/g of protein, U/pancreas, and U/kg of BW) increased linearly (P < or = 0.04) with increasing dietary CP concentration. Pancreatic trypsin activity (U/g, U/g of DNA, U/g of protein, U/pancreas, and U/kg of BW) increased linearly (P < or = 0.09) with increasing dietary CP concentration. Pancreatic alpha-amylase and trypsin activities (U/mg of RNA) responded quadratically (P < or = 0.09), with the greatest alpha-amylase activity observed in the 13.2% CP treatment. These data indicate that increasing dietary CP concentration decreases pancreatic cell numbers and also increases the concentration and content of pancreatic alpha-amylase and trypsin activities. Changes in cell number and size may be important factors regulating digestive enzyme production in the pancreas of cattle.
Twenty-four yearling beef steers (initial BW = 467 ± 3.6 kg), predominately of Angus breeding, were used in a randomized complete block design to determine the effect of dietary intake on pancreatic cellularity, mass, and α-amylase and trypsin activity. Steers were individually fed a high-moisture corn-based diet at 1.25, 1.50, 1.75, and 2.00% of BW (DM basis) using Calan gates. After 28 d on treatment, the heaviest steer from each dietary treatment was slaughtered per wk and pancreata collected. Average daily gain (kg) and pancreatic weight (g) increased linearly (P ≤ 0.01) with increasing DM intake. Pancreatic DNA and RNA concentration and content, and RNA:DNA and protein:DNA did not differ (P > 0.05) between treatments. This suggests that the observed increase in tissue weight was due to increases in both cell size and number. Total pancreatic α-amylase activity (kU pancreas-1) increased linearly (P = 0.04) with increasing DM intake. These data indicate that total pancreatic α-amylase activity (kU pancreas-1) linearly increases with increasing intake of a high-moisture corn-based finishing diet and that dietary intake-dependent changes in total pancreatic α-amylase activity are primarily due to changes in pancreatic weight rather than changes in the concentration of pancreatic α-amylase activity (U g-1 pancreas). Key words: Beef cattle, pancreas, α-amylase, trypsin, feed intake
. W. 2008. Pancreatic mass, cellularity, and a-amylase and trypsin activity in feedlot steers fed diets with increasing corn silage inclusion. Can. J. Anim. Sci. 88: 703Á709. Twentyfour yearling beef steers (initial BW 053595.0 kg), predominately of Angus breeding, were used in a randomized complete block design to determine the effect of dietary inclusion of corn silage on pancreatic cellularity, mass, and a-amylase and trypsin activity. Using calan gates, steers were individually fed diets containing 20, 40, 60, or 80% corn silage (DM basis) with the rest of the diet made up of concentrate. Diets were formulated to maintain a constant CP:ME (g Mcal ) and were fed at 2.1 )NE m requirement. After 28 d on treatment, the two heaviest steers from each treatment were slaughtered per week and pancreata collected. Pancreatic weight (g and g kg(1 BW) and content (kU and U kg (1 BW) of a-amylase activity did not differ among dietary treatments. Concentration (U g(1 ) of pancreatic a-amylase decreased (P00.03) with increasing corn silage inclusion. Pancreatic DNA and RNA content (g and mg kg(1 BW) increased linearly (P 50.04) with increasing corn silage inclusion. The content of pancreatic trypsin activity responded cubically (P00.03). These data indicate that increasing corn silage inclusion does not influence total pancreatic a-amylase activity and that cell number may influence pancreatic a-amylase concentration. Ces re´sultats indiquent qu'augmenter la quantite´d'ensilage de maı¨s dans la ration n'exerce aucune influence sur l'activite´totale de la a-amylase pancre´atique mais que le nombre de cellules pourrait agir sur la concentration de cette enzyme.Mots clé s: Mots cle´s: Bovins de boucherie, pancre´as, a-amylase, trypsine, fourrage, concentreT he pancreas produces enzymes responsible for the digestion of nutrients in the small intestine. Pancreatic a-amylase and trypsin are responsible for the partial hydrolysis of starch and protein, respectively, in the small intestine. Pancreatic exocrine function is influenced by nutritional as well as genetic factors Swanson and Miller 2008). In high concentrate feedlot diets, significant amounts of dietary starch reach the small intestine (Theurer 1986) where there may be limitations in starch digestion due to inadequate a-amylase secretion Harmon et al. 2004). Dietary forage:concentrate may be an important regulator of pancreatic exocrine function. Data suggest that pancreatic content of aamylase activity decreases in cattle fed a high grain diet vs. those fed a high forage diet at similar energy intakes (Kreikemeier et al. 1990;Harmon 1992). However, when dietary metabolizable protein intake was fed at similar intakes in lambs, content of pancreatic a-amylase activity was not influenced by increased starch concenAbbreviations: ADF, acid detergent fibre; BW, body weight; DM, dry matter; ME, metabolizable energy; NDF, neutral detergent fibre; NE m , net energy for maintenance For personal use only.
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