Influence of a parasitic infection in fattening pigs on their amino acid requirement

In a feeding trial at the Swiss Federal Research Station for Animal Production (RAP), a total of 48 fattening pigs were given daily access (7 to 9 hrs) to an uncultivated plot infected with Ascaris suum eggs to investigate the influence of the parasitic exposure and subsequent infection on the amino acid requirements. Set up as a 2×2 factorial design, the experimental rations varied in their amino acid supply (feeding standard, feeding standard + 10 %) and the use of synthetic amino acids (with synthetic AA, without synthetic AA) yielding differing crude protein contents. Considering the parasitic stress and daily outdoor activity, the pigs realised a high fattening performance. The exclusion of synthetic amino acids in the grower feed ration resulted in significant higher growth rates and improved feed conversion ratios. No such dietary effect was observed for the finishing period. Based on these findings, it is assumed that an Ascaris infection raises the amino acid requirement of grower pigs, apparently concerning the usually non limiting amino acids. The additional requirement is met by a ration optimised according to RAP feeding standards with synthetic amino acids excluded (higher crude protein content). For the finishing period, a ration optimised according to feeding recommendations containing synthetic amino acids covers the protein needs. The additional amino acid supply did not improve the percentage of premium meat cuts. It is concluded that the dietary amino acid pattern and the fitness status of the pigs are of some importance with respect to the severity of liver damage caused by larval migration.