Growth performance responses to increased tryptophan supplementation in growing barrows fed three different very low crude protein corn and soybean meal‐based diets fortified with essential amino acids

Abstract

Seventy-five individually fed barrows averaging 35 kg were used in a series of three experiments for 6-week growth assays (25 barrows each) to determine the effects of L-tryptophan (Trp) supplementation on growth performance and to establish the lower limits of dietary crude protein (CP) levels. Corn and soybean meal (SBM)-based diets containing 9% (Experiment 1), 10% (Experiment 2), and 11% CP (Experiment 3) fortified with deficient essential amino acids (AAs) except Trp were used as basal diets for each experiment. The experimental diets were supplemented with 0.00%, 0.02%, 0.04%, or 0.06% Trp. A 16% CP corn-SBM-based diet was set as a positive control in each experiment, and feed and water were provided ad libitum. Average daily gain and gain-to-feed ratio improved quadratically (P < 0.05) as supplemented Trp increased in the 9% and 10% CP group, although these positive effects were not observed in the 11% CP group. Because the maximum performance parameters in 9%, 10%, and 11% CP groups were not different from that of the 16% CP positive control group, the marginally reduced level of dietary CP without growth performance being affected appears to be around 9% at most. A potential reduction of nitrogen intake was clearly indicated.

Intestinal tryptophan metabolism in disease prevention and swine production

“…Maintaining the levels of Lys, methionine (Met), threonine (Thr), and L-Trp in early protein-restricted diets during the grower phase improved the growth performance, with an increased growth rate and FCR, and decreased diarrhea rate ( Sun et al., 2020 ). Additionally, the addition of different L-Trp concentrations to the diet with low crude protein levels enhanced the ADG and G:F ratio in growing barrows ( Sato et al., 2021 ). Intensified housing conditions and poor sanitation are often associated with decreased growth performance and the abnormal activation of the immune system during pig farming.…”

“…(2021b) PIC TR4 × (Large White × PIC L02) 103 Moderate L-Lys HCl + high Ile, Val, and Trp + Val Increased ADFI Kerkaert et al. (2021) Landrace 42 0.06% Trp in low CP diet Increased ADG, ADFI Sato et al. (2021) 28 Trp + Thr + Met Improved growth performance and protein deposition Valini et al.…”