Efficacy of protected benzoic acid in broilers subject to Eimeria challenge as affected by diet type

It is recognized that the benefits of eubiotic feed additives are not consistently demonstrated in research trials, especially in a clean environment without any challenge. Understanding factors affecting their efficacy will facilitate mechanism of action investigation and guide practical application. A battery trial was conducted with 384 day-old male broilers to evaluate the effect of protected benzoic acid on growth performance and gut health of broilers subject to Eimeria challenge as affected by diet type. The study consisted of 6 dietary treatments in a 3 x 2 factorial arrangement with 3 types of diet (rye 10%, canola meal 7.5% and poultry meal 3%, and their combination) and 2 levels of protected benzoic acid (0 and 500 g/ton AVIMATRIX® Novus International, Inc.). Each diet was fed to 8 replicate pens of 8 birds. All birds were orally gavaged with a coccidiosis vaccine at 10X recommended dose on d 14. Body weight, feed intake, FCR, and mortality were determined on d 7, 14, 19, and 26. On d 27, blood samples were collected for serum coloration, IL-10 and IL-4 determination. Data were subject to 2-way ANOVA to evaluate main effects and interaction; means were separated by Fisher’s protected LSD test. Body weight was reduced with inclusion of 10% rye on d 7, 14, and 19 regardless of canola and poultry meal (CPM) inclusion (P<0.05). Benzoic acid increased body weight on d 7 and 14 regardless of diet type (P<0.05). On d 26, without benzoic acid, birds fed CPM weighed higher than those fed the combination, and the rye fed birds weighed in between not significantly different from either; benzoic acid increased 26-d BW of broilers fed the combination by 12%, not in the other two types, accounting for a trend of interaction (P=0.09). Up to d 14, FCR was not significantly affected by diet type, but improved by benzoic acid by 17 and 7 points on d 7 and 14 respectively (P≤0.05). There was an interaction between diet type and benzoic acid on d 19 (P=0.07) and 26 (P<0.05) where combining rye and CPM led to higher FCR, which was reversed by benzoic acid supplementation. Feed intake was affected by diet type on d 14, 19, and 26 (P<0.05) in which higher BW typically corresponded to higher feed intake, but not significantly affected by benzoic acid (P>0.10). Serum IL-4 was the highest in birds fed rye, followed by CPM and rye, and then by CPM (P<0.05), indicating rye was capable of inducing inflammatory responses. In summary, protected benzoic acid improved growth performance of broilers subject to Eimeria challenge in all three diet types, and the efficacy was greater when diet complexity was increased by combining viscous grain and low digestible protein ingredients.

Keywords: benzoic acid, Eimeria, broiler

Presented at 2018 PSA Annual Meeting