263 Dietary Supplementation of Tryptophan, Threonine, and Methionine Improves the Growth and Immune Status for Lighter Body Weight Pigs But Not for Heavier Pigs Under a Sanitary Challenge

Abstract

Abstract Great variability in growth performance and blood metabolites is observed between animals and within the same group. This variation may exist between individuals due to the initial body weight (BW) which may determine different abilities to cope with a sanitary challenge (SC). Besides, supplementing tryptophan (Trp), threonine (Thr), and methionine (Met) above NRC requirements supports the immune system and growth performance costs during a SC. Therefore, this study aimed to investigate the effect of initial BW on changes in body composition, and blood metabolites of growing pigs housed under poor SC and receiving Trp, Thr, and Met at 100 or 120% of NRC recommended levels. Twenty gilts were categorized into two groups according to initial BW: light (22.5 ± 0.8 kg) and heavy (28.5 ± 1.0 kg). Both BW groups were group-housed for a 28-d trial. Pigs were orally inoculated with 2 × 109 CFU of Salmonella typhimurium, and manure from a commercial pig farm was spread on the floor. Two dietary treatments were provided: control (CN) or supplemented (AA+) diet with Trp, Thr, and Met:Lysine 20% above the NRC (2012) requirements. Serum albumin and urea, along with BW were measured on days 0, 14, and 28. Body composition was estimated by dual-energy X-ray densitometry on days 0, and 28 to obtain protein (BP, % of BW) and lipid (BL, % of BW) masses. A linear mixed regression considering repeated measures in time was used to compare the slopes of the BW groups, day, and their interaction within dietary treatments. The BW and BP increased, whereas BL decreased with time (P < 0.10; Table 1). However, light pigs had greater BL than heavy pigs (P < 0.10). Dietary treatment influenced BW differently, and BL changes over time within BW groups (Figure 1). Light pigs fed the CN diet had a faster decrease in BL and a slower increase in BW over time than heavy pigs (P < 0.10), which was not observed in pigs fed AA+ diet. Light pigs fed CN diet had greater serum urea than heavy pigs (P < 0.10), with no differences for pigs fed AA+ diet. No changes in serum albumin were observed between BW within diets. Heavier pigs tend to adapt and cope better under a SC and may not need AA supplementation above the requirement. On the other hand, increasing AA improved ability of lighter pigs to cope with the SC allowing for a greater growth potential under a poor SC.