Duodenal supply of glutamate and casein both improve intestinal starch digestion in cattle but by apparently different mechanisms1

Abstract

Greater postruminal flows of protein increase small intestinal starch digestion in cattle. Our objective was to determine if small intestinal starch digestion is increased by duodenal supplementation of AA. We fed 5 duodenally and ileally cannulated steers a low-starch soybean hull-based diet in 5 × 5 Latin square designs and provided continuous duodenal infusion of raw cornstarch in combination with AA or casein and measured small intestinal starch digestion. In Exp. 1 treatments were continuous duodenal infusion of 1) no supplement (control), 2) casein (400 g/d), 3) crystalline AA similar in amount and AA composition to the casein (CASAA), 4) crystalline nonessential AA similar to those provided by casein, or 5) crystalline essential AA similar to those provided by casein. In Exp. 2 treatments were continuous duodenal infusion of 1) no supplement (control), 2) casein (400 g/d), 3) Glu (133 g/d), 4) Phe and Trp plus Met (30.4, 6.5, and 17.5 g/d, respectively; PTM), or 5) a combination of Glu and PTM. Duodenal infusion of casein increased (P ≤ 0.05) small intestinal starch digestion. When CASAA was infused, small intestinal starch digestion was similar (P = 0.30) to casein infusion. Infusion of only nonessential AA tended to increase (P = 0.14) small intestinal starch digestion relative to the control, but infusion of essential AA alone did not affect (P = 0.84) small intestinal starch digestion. In addition, infusion of casein or CASAA increased ileal flows of ethanol-soluble starch (small-chain α-glycosides), but nonessential AA alone were not different than the control. Duodenal infusion of Glu increased (P ≤ 0.05) small intestinal starch digestion, whereas PTM did not. Neither Glu nor PTM increased ileal flow of ethanol-soluble starch, but Glu and PTM provided together tended (P = 0.07) to increase ileal flows of small chain α-glycosides. Our data suggest that Glu alone can increase small intestinal starch digestion in cattle similar to casein, but increases in small intestinal starch digestion in response to Glu are not associated with an increase in ileal flows of small chain α-glycosides.

Effects of dietary leucine and phenylalanine on pancreas development, enzyme activity, and relative gene expression in milk-fed Holstein dairy calves

“…In Swanson et al (2002), the infused casein in calves increased the small intestinal protein flow that increased pancreatic weight and thus total pancreatic α-amylase and trypsin activity, the effect of which might differ from that by infusion of a single AA. This premise is consistent with the notion that different AA may have different abilities to regulate the pancreas (Hashimoto and Hara, 2004;Brake et al, 2014). In the studies of Yu et al (2013) and Swanson et al (2008), older animals were used (adult goats and 1-yr-old castrated cattle, respectively).…”

“…During the digestion process a variety of enzymes are secreted by the pancreas, including pancreatic α-amylase, trypsin, and lipase. Studies have shown that the insufficient secretion of pancreatic α-amylase is considered a factor limiting the starch digestion in the small intestine of ruminants (Owens et al, 1986;Harmon, 2009;Brake et al, 2014;Liu et al, 2015). Therefore, research on the pancreas has been focused on enhancing the synthesis and secretion of its digestive enzymes.…”

“…These authors also observed that a change in the ratio of the EAA to starch in the small intestine could change pancreatic amylase secretion. By infusing casein, EAA, NEAA, and glutamate into the duodenum, Brake et al (2014) found that casein and EAA increased the secretion of pancreatic amylase without affecting the starch digestibility in the small intestine, whereas NEAA and glutamate increased the starch digestibility (steer initial BW = 259 kg). Yu et al (2014) showed that both protein and AA could influence the activities of pancreatic enzymes and the expression of their genes in yearling ewes (initial BW = 297 kg) by altering pancreas development.…”

Effects of Branched Chain Amino Acids on digestive enzymes secretion from pancreas of dairy cows

“…However, this three amino acids did not interact with α-amylase, trypsin and chymotrypsin and not affect digestive enzyme activities. The difference between this observation and previous results may be due to the difference in amino acid composition, resulting in different regulation way and effects on pancreas [36].…”

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

“…It has been proposed that pancreatic a-amylase secretion is a limiting constraint to SISD, and that this can be increased with greater post-ruminal flows of high-quality protein. Duodenal infusion of casein and casein-like nonessential amino acids increased pancreatic a-amylase secretion linearly, and increased SISD, by, on average, 0.31 for each gram of duodenally infused casein (Brake et al 2014a(Brake et al , 2014bBlom et al 2016). Rumen protection of non-essential amino acids and glutamate may, therefore, increase SISD in feedlot cattle fed corn-based diets.…”