Salmonellosis is one of the most important foodborne zoonotic diseases throughout the world and poultry represents an important source of infection in humans. Chickens may become infected during incubation, in the brooding houses, through various vectors, such as feed and rodents or during slaughtering and processing. The use of antibiotics have been reduced and even banned in some countries, due to the risk of bacterial populations developing resistance against the antibiotics. This lead to the exploration of alternative products for antibiotics as growth promoters, which include prebiotics, probiotics, organic acids, essential oils, plant extracts and many more. These products may improve animal health, productivity and microbial food safety in a natural way. A feeding trial was conducted to investigate the effects of the dietary inclusion of probiotics and a prebiotic to improve the health and performance of broilers, which were challenged with Salmonella typhimurium. 1800 chicks (900 chicks exposed to Salmonella and 900 chicks not exposed) were randomly assigned to 6 dietary treatments for 5 weeks. The dietary treatments were: 1) No feed additives added, 2) A prebiotic (fructooligosaccharide) added to the feed, 3) Probiotic type 1 (Spore-forming bacteria) added to the feed, 4) Probiotic type 1 combined with the prebiotic added to the feed, 5) Probiotic type 2 (Lactobacillus spp.) added to the feed, 6) Probiotic type 2 combined with the prebiotic added to the feed. The feed intake, average daily gain and body weight of the control (nonchallenged) birds were significantly higher (P<0.05) than the Salmonella (challenged) birds. The Probiotic type 2 combined with the prebiotic improved the feed intake of the non-challenged birds compared to the non-challenged birds that received no supplementation or only a prebiotic. The challenged and non-challenged birds that did not receive any supplementation had lower body weights and average daily gains compared to the birds that received supplementation. The feed conversion ratio showed significant differences among the treatments (P<0.003) and between the control and Salmonella birds (P<0.05). The non-challenged birds fed the Probiotic type 2 combined with a prebiotic and the challenged birds fed only the prebiotic, displayed a decrease in liver weight, compared to the other treatments. However, the duodenum, jejunum and caeca weights of the broilers were significantly (P<0.05) enlarged shortly after Salmonella exposure through the inclusion of Probiotic type 1 and the two combination treatments in the diet. No significant differences were observed in the ileal weights after Salmonella exposure or after dietary supplementation. The total serum protein and the aspartate amino transferase (AST) levels showed no significant differences between the groups and treatments. However, the albumin levels of the challenged birds were significantly lower (P<0.05) than the non-challenged birds. The globulin levels were higher for the challenged birds that did not receive any supplementation than those that received a prebiotic and probiotics. The albumin: globulin ratios were higher for the non-challenged birds than the challenged birds. In general, the challenged birds tended to have more lesions than the non-challenged birds on the gastrointestinal tract (GIT). There were no significant differences in the villous height, mucosal thickness and crypt depth of the duodenum, jejunum and ileum. However, the control birds supplemented with Probiotic type 2 combined with a prebiotic showed a thicker mucosa layer than the control that received no supplementation. These findings indicate that the supplementation of a basal diet with probiotics and combination treatments of probiotics with a prebiotic can be used as growth promoters for broilers. These products, especially the Probiotic type 2 combined with the prebiotic, show promising effects as alternatives for antibiotics as pressure increases to eliminate the growth promotant antibiotics from being used in the livestock industry.
Dissertation (MSc(Agric))--University of Pretoria, 2011.