Highlights
• Average daily gain and feed efficiency in diseased pigs may be improved by a combination of functional amino acids supplemented above requirements for growth
• Functional amino acids improved the immune response associated with Salmonella infection
• Bacterial shedding and intestinal colonization can be reduced by functional amino acid supplementation
• Dietary protein level had limited effect on pig response
Research conducted at the Prairie Swine Centre and the University of Saskatchewan investigated the interaction between functional amino acid (AA) supplementation and dietary protein during disease challenge in growing pigs. To achieve this, growing pigs were either inoculated with an enteric pathogen (Salmonella typhimurium, ST) or received saline control (CT) and had ad libitum access to diets differing in crude protein content (low (16%, LP) vs high (20%, HP) containing either basal supplementation of amino acids at requirements according to NRC (2012) (AA-) or supplemented with a functional amino acid profile in which threonine, methionine, and tryptophan were provided at 20% above requirements (AA+). Diets contained no animal products or antibiotics.
Clinical signs associated with infection
The post-weaning period is a stressful time for growing pigs, with increased susceptibility to several enteric pathogens, including Salmonella. Pigs infected with Salmonella experience a pronounced inflammatory reaction in the gut, consequently showing compromised performance. The researchers monitored body temperature, fecal score and demeanor daily for each pig over a period of 7 days (day -1, 1, 2, 3, 4, 5 and 6 relative to inoculation). Fecal score and demeanor were then scored from 0 to 3 according to severity (Table 1). Inoculation with Salmonella typhimurium increased body temperature within 24 h which remained elevated for the duration of the study (Figure 1). Demeanor and fecal score were negatively affected by ST inoculation during the first 3 and 5 days after challenge, respectively (Figure 1). There were no diet effects on any clinical signs.
High protein diets: are they harmful?
More susceptible post-weaned pigs also experience an abrupt change from a milk-based to a cereal-based diet. Besides that, highly digestible nutrient sources are not always available, and pigs are commonly fed diets high in protein sources potentially harmful for gut health. As a result, current dietary recommendation in the post-weaning period is to provide lower protein diets that have been supplemented with necessary essential amino acids to meet requirements. This reduces the amount of undigested protein available for fermentation At the start and middle of the trial, pigs tend to consume more water after the moving activity. On average, pigs consumed about 3,890 and 5,226 mL 24 hours before stress was induced at the start of the trial and middle of the trial respectively, increasing to 4,138 and 5,878 mL after the stress was induced. These results may imply that grower pigs consumed more water when stressed. No apparent trend was observed for water consumption towards the end of the trial.
Water Consumption and Mixing
A comparison of average water consumption of pigs 24 hours before and 24 hours after unfamiliar pigs were introduced into the pen is shown in Figure 3. In contrast to the moving activity, water consumption generally decreased 24 hours after mixing unfamiliar pigs into the pen. Pigs consumed an average of about 5,387 mL/day of water prior to the mixing activity; this decreased to 4,738 mL/day 24 hours after mixing occurred. The decrease in water consumption might be due to aggression that occurred after mixing, which subsequently prevented some of the pigs from drinking. This observation may have also caused the no apparent increase in water consumption from the start to the end of each trial.
Infrared Thermography – Handling
During the start and middle of the trial, no considerable change in body temperatures was observed. Towards the end of the trial when pigs were close to market weight, a slight increase in body temperature was observed after the moving activity. Pig average body temperature was 36.5°C before the moving exercise; this increased to 36.8°C after the mixing activity. This minimal change in body temperature could indicate that the moving activity was not strenuous enough to cause a marked change in body temperature of pigs.
CONCLUSION
1. Using the individual water consumption system, it was observed that grower pigs tend to consume more water when stressed. The system also confirmed that water consumption increased as the pig grew regardless of stress induction.
2. As captured by the infrared thermography system, aggression as a result of mixing unfamiliar pigs to the pen caused an increase in the recorded body temperature of pigs. The system also showed that the pigs’ body temperature was affected by changes in room temperatures.
3. In this study, installation of the individual water consumption system and infrared thermography system and inducing stress due to moving and mixing had no considerable negative impact on pig production performance.
