Lucas A. Rodrigues1,2, and Daniel A. Columbus1,2*
1Prairie Swine Centre, Inc., Saskatoon, SK
2Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK
- Average daily gain and feed efficiency were improved by feeding functional amino acids above requirements for growth for 2 weeks before Salmonella
- Inflammatory reaction due to Salmonella was attenuated by a longer adaptation period to functional amino acids.
- Salmonella shedding and intestinal presence were reduced in pigs fed functional amino acids for 2 weeks before infection.
- Positive effects of adaptation period to functional amino acids above requirements for growth may be related to improved gut health in pigs.
A previous study conducted at the Prairie Swine Centre and the University of Saskatchewan revealed improved performance of pigs under Salmonella infection when fed functional amino acids (FAA) above requirements for growth. The positive effects were mainly associated with enhanced gut health and improved immune status. Here, researchers attempted to assess whether a longer adaptation period to FAA supplementation would further enhance the previously reported benefits. To achieve this, weanling pigs were fed a basal amino acid profile (AA-) throughout the trial period (FAA-) or a functional amino acid profile only in the post-inoculation (FAA+0), for 1 week pre- and post-inoculation (FAA+1), or throughout the trial period (FAA+2). The functional amino acid profile contained threonine, methionine, and tryptophan at 120% of requirements. Diets contained no animal products or antibiotics, and all the pigs were inoculated with Salmonella after a 2-week pre-inoculation period.
Pigs fed functional amino acids for a longer period showed improved gut health and had lower counts of Salmonella in feces and colon digesta.
Researchers also measured the activity of an enzyme called myeloperoxidase (MPO) in fecal and digesta samples. This enzyme has increased activity during situations of gut inflammatory reaction and has been recognized as an important diagnostic and prognostic tool in assessing enteric disease status. Fecal MPO was increased post-inoculation, which confirms the negative effects of Salmonella in the gut. Interestingly, MPO content measured in fecal and colonic digesta samples were lower in FAA+2 and FAA+1 pigs compared to FAA-, indicating decreased intestinal inflammation with longer adaptation period to FAA supplementation. An improved gut health led to a reduced Salmonella shedding in feces in FAA+2 pigs compared to FAA- and FAA+0. Also, Salmonella presence in colon digesta was increased in FAA- and FAA+0 pigs compared to FAA+2.
Figure 1. Haptoglobin was increased and albumin was decreased post-Salmonella inoculation. Overall haptoglobin was lower in FAA+2 compared to FAA- pigs while FAA+2 and FAA+1 pigs had higher albumin compared to FAA- and FAA+0 (P < 0.05).
A longer adaptation period to functional amino acids decreased overall inflammatory reaction.
The researchers measured the content of two blood proteins, haptoglobin and albumin. These proteins are directly related to the overall health status of pigs, with haptoglobin being increased and albumin being decreased during situations of trauma, infection, or inflammation. As expected, Salmonella increased haptoglobin and decreased albumin. However, these trends were counteracted by supplementation of FAA for a longer period, where overall haptoglobin was lower in FAA+2 compared to FAA- pigs while FAA+2 and FAA+1 pigs had higher albumin compared to FAA- and FAA+0 (Figure 1). These findings are in line with the reduced shedding and intestinal counts of Salmonella in pigs fed FAA-fortified diets for a longer period before infection.
Post-infection growth performance was improved in pigs fed functional amino acids for a longer period
|Table 1. Pre- and post-inoculation growth performance of Salmonella-inoculated pigs
No effects of treatments were observed pre-inoculation (Table 1). Post-inoculation, weight gain and feed efficiency were improved in FAA+2 compared to FAA- pigs. This finding confirms the attenuation of the negative effects of Salmonella and are in line with lower MPO content in FAA+2 and FAA+1 pigs, which indicates that a longer adaptation period to FAA supplementation improved gut health, improving the ability of pigs to cope with the subsequent Salmonella challenge. One remarkable finding from this study was that the positive effects of a longer adaptation period to FAA+ diets on weight gain and feed efficiency of Salmonella-inoculated pigs were achieved regardless of increments in feed intake, which highlights the ‘functional’ roles of the amino acids supplemented, beyond protein synthesis.
Acknowledgments: Funding for this project was provided by Swine Innovation Porc and Evonik Industries GmbH. Prairie Swine Centre receives program funding from the Government of Saskatchewan, Sask Pork, Alberta Pork, Manitoba Pork, and Ontario Pork.