Necrotic enteritis (NE) is one of the most important diseases of the world broiler industry which costs over six billion dollars annually. There has been a concerted effort to control and minimise the effects of NE that have arisen since the EU ban of in-feed antibiotics in the poultry industry. Organic acids have been used as alternatives to in-feed antibiotics for maintaining good gut health of poultry by suppressing the growth of pathogenic bacteria, resulting in improved performance (Naseri et al., 2012). The present study investigated the effects of dietary supplementation of a mixture of 1-mono-glycerides (MG) and sodium buffered formic acid (FA) in diets on broiler performance, mortality rate and caecal microflora under a necrotic enteritis challenge. A total of 544 d-old Ross 308 broiler chicks (as hatched) was allotted to 32 pens each stocked with 17 birds. A randomised complete block design was used with 4 treatments replicated 8 times. The treatments included: 1- negative control, without additives; 2- positive control containing salinomycin (0.050%) and zinc bacitracin (0.033%); 3- mixture of 1-mono-glycerides (MG), starter: 0.5%, grower: 0%, finisher: 0%; 4- MG + sodium buffered formic acid (FA), starter: 0.5% MG, grower: 0.3% FA, finisher: 0.3% FA. All diets were wheat, sorghum, soybean meal and meat and bone meal based, formulated to meet Ross 308 nutrient specifications. The NE challenge model followed the method described by Keerqin et al. (2017). Bird performance was measured from d 0-10, d 11-24, d 0-24 and d 0-35. NE caused mortality was determined by necropsy and recorded after challenge, while caecal microflora was measured on d16. Data were analysed using the General Linear Models (GLM) of SPSS and male:female ratio determined by feather sexing was set as a covariate for performance data. Birds fed diet-contained antibiotics showed better FCR, higher weight gain and feed intake during the whole period of study (P < 0.05) except for d 0-10, compared to those fed diets supplemented with or without additives. Birds fed the diet supplemented with 0.5% MG in starter phase and 0.3% FA in grower phase had enhanced FCR (from d 10-24 and d 0-24) compared to those fed no-additive diet (P < 0.05). However, no significant differences were observed on FCR, weight gain and feed intake between birds which received different additives and those without additives during d 0-35 (P > 0.05). The diet-contained antibiotics reduced the occurrence of mortality due to NE (P < 0.05). Birds fed the diet supplemented with 0.5% MG in starter phase reduced the occurrence of mortality due to NE compared with those fed no-additive diet (26.1% vs. 14.8%, P < 0.05). Birds fed the diet supplemented with antibiotics had lower counts of Lactobacillus spp. compared to those fed the diet without additives and those fed the diet supplemented with 0.5% MG in starter phase following 0.3% FA in grower phase (P < 0.05), but did not significantly differ from birds fed 0.5% MG in the starter phase. Birds fed the diet supplemented with different additives had higher counts of Clostridium perfringens (P < 0.05) compared to the antibiotics group but were not significantly different from those fed the no-additive diet. Total anaerobic bacteria, Ruminococcus spp., Bacillus spp., and Bifidobacterium spp., were not affected by different treatments (P > 0.05). These results demonstrated that the MG supplemented in the starter phase and MG in starter phase followed by FA in the grower phase may partially protect birds from clinical necrotic enteritis as indicated by reduced mortality and improved feed efficiency.
Abstract presented at the 30th Annual Australian Poultry Science Symposium 2019. For information on the latest edition and future events, check out https://www.apss2021.com.au/.