Increasing Functional Amino Acid Ratios Does Not Improve Growth Performance in Pigs Raised Under Poor Sanitary Conditions When Fed with Individual Precision Feeding Or Conventional Feeding Systems

Immune system activation redirects dietary nutrients to defense mechanisms, thereby impairing growth performance of pigs. Supplementing pigs with functional amino acids (AA) such as Met, Thr and Trp was shown to support the immune system and reduce the negative effects on growth. However, pigs respond differently to immune stressors which increase herd variability. In this context, individual precision feeding (IPF) might be an alternative approach to reduce herd variability and increase nutrient efficiency in immune challenged pigs. This study aimed to evaluate growth performance, body composition, nitrogen (N) efficiency and haptoglobin and triglycerides serum concentration in growing pigs raised in poor sanitary conditions (PoorSC). The PoorSC was characterized by oral inoculation with 2 × 109 cfu of Salmonella typhimurium and manure spreading on the pen floor. Sixty gilts (23 ± 2.8 kg BW) were distributed in BW blocks according to a 2 dietary (D) × 2 feeding system (FS) factorial arrangement composed of to 2 diets [control (CN): INRA ideal AA ratio or supplemented (AA+) 120% of the ideal ratio for Met, Thr and Trp] and 2 feeding systems [conventional (GP) or IPF]. GP pigs were fed with a unique diet that matched the SID Lys requirement of the 80th-percentile pig at the beginning of the trial whereas the IPF pigs received a diet tailored daily to each pig requirement. All pigs were housed in the same pen and fed ad libitum during 28 experimental days with automatic feeding stations able to provide to each pig the assigned diet. Body composition was obtained by dual X-ray absorptiometry at days 0 and 28 and blood samples were collected at d 28. Data were analyzed with D and FS and their interaction as main fixed factors and body weight (BW) blocks as a random effect (Table 1). Haptoglobin serum concentration increased from d 0 to 28 regardless of FS and D (P < 0.10). IPF pigs fed with CN diet had the lightest BW at the end of the trial (P ≤ 0.10; FS × D), whereas BW was similar for the other treatments. However, across diets, IPF pigs had final BW, and protein, ADG, G:F, protein and lipid deposition, N intake and excretion and circulating triglycerides that were less than GP pigs. N utilization efficiency was similar across treatments. Additionally, increasing the provision of the studied functional AA did not improve pig performance. Thus, showing no benefits in increasing AA ratios for growth and immune response. The increased triglycerides concentration and low protein and lipid deposition suggests that IPF pigs prioritized the immune system to the expense of protein and lipid accretion. In conclusion, AA supplementation and IPF do not improve growth performance and N efficiency of pigs raised in poor sanitary conditions.