Postruminal supply of amino acids enhances ghrelin secretion and lipid metabolism in feed‐deprived sheep

Abstract

Single amino acids (AA) feeding is gaining more attention for their functional roles beyond nutritional needs. This study aimed to describe the endocrine and metabolic responses to a single AA administration (at 10% of MP for maintenance) in 48 hr fasted sheep (n = 4) receiving, over continued 4 hr, a duodenal infusate of saline (control), glutamate (Glu), glutamine (Gln), lysine HCl (Lys), threonine (Thr), or valine (Val) in a 4 by 6 Youden square design with weekly intervals. Blood samples were collected at 0, 15, 30, 60, 120, 180, and 240 min relative to the infusion onset, and plasma AA, glucose, β‐hydroxybutyric acid (BHBA), nonesterified fatty acids (NEFA), ghrelin, insulin, glucagon, and insulin‐like growth factor 1 (IGF‐1) concentrations were measured. The results showed that the duodenal supply of Glu, Gln, Lys, Thr, and Val enhanced ghrelin release. Administration of Glu, Gln, and Val declined plasma BHBA concentrations, whereas plasma NEFA levels were decreased with Gln and Thr. Insulin concentration was greater with Thr, glucagon levels were increased with Lys, Thr, Val, and Glu, whereas IGF‐1 levels were enhanced with Gln, Lys, and Thr supply. Thus, selective AA feeding can positively adjust the endocrine status and counteract the feed restriction‐induced lipid mobilization.

Effects of rumen-protected glutamate supplementation during the periparturient period on digestibility, inflammation, metabolic responses, and performance in dairy cows

“…Another possible reason for greater DMI for cows fed the RP-Glu is hormonal control. In a previous study, duodenal Glu infusion in 48-h fasted sheep increased plasma ghrelin concentration (Elsabagh et al, 2018). As ghrelin increases feed intake (Kojima et al, 1999), the greater DMI for the RP-Glu treatment might be mediated by ghrelin.…”

“…Glutamate is considered as a NEAA, and NRC (2001) does not establish its dietary requirement for dairy cows. However, previous studies reported that postruminal Glu infusion increased plasma Glu concentration in 48-h fasted sheep (Elsabagh et al, 2018) and feed restricted mid-lactation cows (Ansia et al, 2017). Similarly, we observed that cows fed the RP-Glu diet had greater plasma Glu concentration only right after calving.…”

“…Furthermore, Glu contributes up to 4% of the total glucose produced in sheep (Heitmann and Bergman, 1981). Other studies also report that postruminal Glu infusion increases plasma glucose concentration in sheep (Elsabagh et al, 2018) and lactating dairy cows (Ansia et al, 2017). Glutamine and Glu play similar physiological roles in the gut tissues (Heitmann and Bergman, 1981), and effects of postruminal Gln infusion were evaluated for transition dairy cows (Doepel et al, 2006).…”