Amino acid selection by piglets in a choice-feeding setting under different sanitary conditions

Pigs are capable to repair an amino-acid (AA) deficiency by eating higher quantities of an AA-adequate diet in a choice-feeding setting. To investigate the ability of pigs to detect and repair an AA deficiency under different sanitary conditions, 60 piglets (n=30 pairs) were observed for 19 days (from 5 weeks of age). Piglets were housed under high (HSC) or low (LSC) sanitary conditions and had ad libitum access to either a diet deficient in eight indispensable AA (IAA) (LP-) (No-choice) or the choice between the LP- and a diet supplemented with eight IAA (LP+) (Choice) in a 2x2 factorial design. Performance and behaviour were recorded, and blood and brain samples were collected at the end of the experiment. LSC piglets had 31, 44, and 21% lower ADFI, ADG, and G:F than HSC piglets, while no differences were observed between No-choice and Choice piglets. Both HSC and LSC Choice piglets ingested more LP- than LP+ diet, but with different pattern in time. LSC piglets had 22, 38, and 129% higher leukocyte, monocyte, and haptoglobin levels than HSC piglets, and also higher concentrations of neurotransmitters, tryptophan and their metabolites in the pre-frontal cortex and hippocampus. Duration and frequency of object and locomotory play were higher in HSC than in LSC, and Choice piglets tended to perform object play more frequently. In conclusion, LSC, while decreasing performance, activating the immune system, and reducing brain neurotransmitter concentrations and play behaviour, did not increase the preference for an AA-supplemented diet in a choice-feeding setting.