Response to a Salmonella Typhimurium challenge in piglets supplemented with protected sodium butyrate or Bacillus licheniformis: effects on performance, intestinal health and behavior,2

Abstract

Salmonella spp. is one of the worldwide leading causes of food-borne illnesses for which the inclusion of probiotics or organic acids in animal feeds can be useful control methods. Experimental models are utilized to test the efficacy of strategies against pathogens, but they exhibit limitations which may preclude finding sensible evaluation parameters. The objective of this work is to evaluate the efficacy of 2 different feed additives; a Bacillus licheniformis based probiotic and a protected sodium butyrate (SB) salt, using an experimental model of salmonellosis and, second, to explore if behavior analysis can be used as a sensible evaluation tool for additives evaluation. A total of 78 piglets weaned at 24 d, 8.3 kg BW, were used. Seventy-two were placed in 3 rooms of 8 pens (3 animals/pen) with evenly distributed treatments (n = 8): CON, control group with plain diet; PRO, plain diet with 1 kg/t of Proporc (10⁹ cfu of B. licheniformis/kg of feed), and BUT, plain diet with 3 kg/t of Gustor BP70 (2.1 g of partially protected SB salt/kg of feed). Remaining piglets (n = 6) were separated and used as a challenge negative control. The experiment lasted 16 d. After 1 wk of adaptation, animals were challenged with 5 × 10⁸ cfu of Salmonella Typhimurium. One pig per pen was euthanized and sampled at d 4 and 8 post-inoculation (PI). There were no significant differences among treatments for ADFI, ADG, G:F, rectal temperature, fecal consistency, pH, ammonia, short-chain fatty acids and lactic acid concentrations, cytokine TNF-α, Pig-MAP acute-phase proteins and histological parameters. However, both products were equally able to reduce colonization and shedding of Salmonella (P = 0.016 for PRO and BUT vs. CON). In addition, PRO treatment had a positive effect on behavioral displays, particularly exploring (P < 0.05 vs. CON), feeding (P < 0.05 vs. CON and BUT) and other active behaviors (P < 0.05 vs. CON and BUT) in the morning period (0830 to 1030 h). In the afternoon (1400 to 1600 h), the challenge effect was most significant. Pigs were less active after the challenge (P < 0.001), with a decrease in positive contacts (P = 0.004), exploration (P < 0.001) and feeding behaviors (P < 0.001) on d 3 PI, in comparison with before the challenge. Accordingly, many lying conducts increased at d 3 PI (P < 0.05). In conclusion, both treatments had positive effects against Salmonella, and behavior analysis appears to be a sensible tool to be considered.

Keywords: Bacillus licheniformis; Salmonella Typhimurium; behavior; feed additives; piglets; sodium butyrate.

Figure 1.

Percentage of Salmonella shedders along the post-inoculation (PI) period. Percentage of animals (n = 8) that showed Salmonella in feces at d 0, 1, 7 post-inoculation (PI) or colon digesta at d 8 PI. P-values obtained by Fisher's exact test. Treatments: CON, plain diet without additives; PRO, plain diet with 1 kg/t of Proporc (10⁹ cfu/kg of feed of Bacillus licheniformis); BUT, plain diet with 3 kg/t of Gustor BP70 (2.1 g of partially protected sodium butyrate salt/kg of feed).

Figure 2.

Frequency of animals with active and inactive behaviors in the morning (0830 to 1030h) and afternoon (1400 to 1600 h), before and after the oral inoculation of the pathogen, for the different dietary treatments. Each data point represents a mean value (n = 8). Treatments: CON, plain diet without additives; PRO, plain diet with 1 kg/t of Proporc (10⁹ cfu/kg of feed of Bacillus licheniformis); BUT, plain diet with 3 kg/t of Gustor BP70 (2.1g of partially protected sodium butyrate salt/kg of feed). Active = positive + negative + exploration + feeding + drinking + walking + others. Inactive = lying laterally or ventrally, with or without contact with pen mates.