Effects of long-term postgastric infusion of casein or glutamic acid on small intestinal starch digestion and energy balance in cattle

Abstract

The objective of this experiment was to evaluate effects of postruminal flows of casein or glutamic acid on small intestinal starch digestion and to quantify changes in energy and nutrient balance. Twenty-four steers (body weight = 179 ± 4 kg) were duodenally infused with raw cornstarch (1.46 ± 0.04 kg/d) and either 413 ± 7.0 g casein/d, 121 ± 3.6 g glutamic acid/d or water (control). Measures of small intestinal starch digestion and nutrient excretion were collected across 4 d after 42 d of infusion and measures of respiration via indirect calorimetry were collected across 2 d after 48 d of infusion. Ileal starch flow was least among calves provided casein, but ileal starch flow was not different between glutamic acid or control. Small intestinal starch digestion tended to be greatest among calves provided casein, least for glutamic acid and intermediate for control. Casein increased ileal flow of ethanol soluble oligosaccharides compared to glutamic acid and control. Large intestinal starch digestion was not different among treatments. By design, N intake was greatest among cattle provided casein, intermediate among calves provided glutamic acid and least for control. Nitrogen retention was greater in response to casein compared to control and glutamic acid. Intake of gross energy from feed was similar across treatments, and gross energy from infusate was greatest for casein, intermediate for glutamic acid and least for control. Variation in gross energy intake from feed resulted in no difference in overall gross energy intake across treatments. Similar to measures of small intestinal starch digestion and N retention, casein increased calories of digestible energy and metabolizable energy, compared to glutamic acid and control, which did not differ. Postruminal infusions did not influence methane production, but heat production was greatest in steers infused with casein, intermediate for steers provided glutamic acid, and least for control. Overall, amounts of energy retained by casein tended to be nearly 34% greater than control, but glutamic acid had no impact on energy balance. Improvement in small intestinal starch digestion in response to casein increased energy and N retained; however, glutamic acid did not influence small intestinal starch digestion and energy or N balance in cattle, which seems to suggest that responses in small intestinal starch digestion to greater postruminal flows of glutamic acid become refractory across greater durations of time.

NCCC308: Nutrition and Management of Feedlot Cattle to Optimize Performance, Carcass Value, and Environmental Compatibility – Feature Collection - Nutrition and Management of Finishing Cattle

“…Enhance the utilization of carbon from energy feeds to compete in an energy economy and improve national food security ( Acharya et al, 2023 ; Coulson et al, 2023 ; Francis et al, 2023 ; Hamilton et al, 2023 ; Larson et al, 2023a and b ; Tarnonsky et al, 2023a and b ; Troyer et al, 2023 ; Wilson et al, 2023 ; Winders et al, 2023 ).…”

Effects of long-term postgastric infusion of casein or glutamic acid on small intestinal starch digestion, energy balance, body composition, and metabolic fates of luminally assimilated glucose carbon in cattle

“…There was a slight tendency for C lost in feces to be least among cattles that received casein which corresponded with differences in DM and starch digestibility (Acharya et al, 2022). Cattle that received glutamic acid were intermediate to both casein and control and did not differ from either control which was greatest.…”

“…Cattle were fed to 1.5 × NEm requirements, and diets fed to cattle in this experiment were designed to exceed metabolizable protein requirements by 20% and fed in amounts to meet 1.5 × maintenance energy requirements. Like differences in DMI, DM infusion (Acharya et al, 2022) carbon intake reflected differences in DMI, as C intake was similar among treatments. Carbon lost to urine however was significantly greater for cattle that received casein and glutamic acid compared to cattle that received corn starch alone, which likely reflects increased amount of AA oxidized for energy.…”

“…There were no differences in feed loss to nitrogen in feces. This is likely because this model likely exceeded large intestinal fermentative capacity (Acharya et al, 2022). Given that there is no change in large intestinal fermentation there is likely no difference in the amount of microbial mass that flows to feces, although we did not directly measured that.…”

“…Cattle were adapted to duodenal infusions for 41 d and measures of nutrient disappearance from the small and large intestines and measures of total-tract nutrient balance were determined from samples of feed, infusate, orts, ileal digesta, urine and feces collected on d 42 to 45 as we described previously (Acharya et al, 2022). After 57 d steers were fitted with bilateral indwelling jugular catheters (14 GA 20 cm, Mila international inc., Florence, KY) five h prior to jugular infusion of a isotopomer of [6,6-2 H2]-glucose to facilitate measures of glucose appearance rate, and jugular blood samples (10 mL) was collected using a syringe and placed in a plastic tubes containing potassium ethylene diamine tetra acetic acid immediately prior to jugular infusions and then each h for 12 h. Subsequently, plasma was harvested after centrifugation with blood at the rate of 2,200 × g for 15 minutes at 4°C temperature.…”