Excess dietary amino acids (AA) may negatively affect feed intake in pigs. Previous results showed that Lys, Leu, Ile, Phe, and Glu significantly increased gut peptide secretion (i.e., cholecystokinin, glucagon-like peptide 1). However, the link between dietary AA and gut peptide secretion with changes in feeding behavior patterns has not been demonstrated to date in pigs. The aim of the present study was to determine the effect of Lys, Leu, Ile, Phe, and Glu, on feed intake and meal patterns in young pigs. Twelve male pigs (Landrace × Large White, body weight = 16.10 ± 2.69 kg) were administered an oral gavage of water (control) or Lys, Leu, Ile, Phe, Glu, or glucose (positive control) at 3 mmol.kg-1 following an overnight fasting. The experiment consisted in measuring individual feed disappearance and changes in meal pattern (including latency to first meal, first meal duration, intermeal interval, second meal duration, and number of meals) based on video footage. Compared to the control group Lys significantly (P ≤ 0.01) reduced feed intake during the first 30 min and up to 2.5 h post-gavage, including a reduction (P ≤ 0.05) in the first meal duration. Similarly, Leu and Ile also significantly decreased feed intake up to 3 h post-gavage on a cumulative count. However, the strongest (P ≤ 0.01) impacts on feed intake by the two branched chained AA were observed after the first- or second-hour post-gavage for Leu or Ile, respectively. In addition, Leu or Ile did not affect the first meal duration (P ≥ 0.05). Leu significantly increased (P ≤ 0.01) the intermeal interval while decreasing (P ≤ 0.05) the number of meals during the initial 2 h following the gavage when compared with the control group. In contrast, the oral gavages of Phe or Glu had no significant impact (P > 0.05) on the feeding behavior parameters measured relative to the control pigs. In turn, glucose had a short-lived effect on appetite by reducing (P < 0.05) feed intake for 30 min after the first-hour post-gavage. In conclusion, the impact of an oral gavage of Lys on feeding behavior is compatible with a stimulation of early satiation and an increased duration of satiety. The main impact of the oral gavages of Leu and Ile was an increase in the duration of satiety. The gastrointestinal mechanisms associated with non-bound dietary AA sensing and the impact on voluntary feed intake warrant further investigations.
Keywords: amino acid; feed intake; meal pattern; pig; satiation; satiety.
A better understanding of the impact of individual dietary amino acids on feeding behavior in pigs can help improve current feed formulation practices. Lys, Leu, Ile, Phe, or Glu were selected based on the impact on gut peptide secretion from a previous study, to assess the effect on feed intake and meal pattern using an oral gavage model (3 mmol.kg−1) in young pigs. The oral gavage of Lys resulted in early satiation as indicated by the reduction of the first meal duration and the feed intake within the first 30 min post-gavage. In addition, the Lys group showed reduced feed intake up to 3 h post-gavage, interpreted as an extended duration of the post first meal satiety compared to the control. The latter was also observed for the branched chained amino acids (BCAA) Leu and Ile. The Leu gavage resulted in an increased intermeal interval together with a reduction on the number of meals while Ile, in turn, reduced feed intake particularly during the third hour post-gavage. No significant effects of the Phe or Glu gavages on feeding behaviors were observed. Overall, these results suggest that dietary Lys, Leu, or Ile had significant anorexigenic effects. Lys increased both satiation and satiety while the BCAA Leu and Ile, mainly increased post-meal satiety in pigs.
© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.