Feed additives affects RNA expression in the brush border membrane in broilers
Probiotics and essential oils have been investigated as replacements for antibiotic growth promoters (AGP) by improving the performance and gut health of chickens. However, studies reported contrasting responses from these additives in intestinal digestion and absorption. We investigated the effects of addition of Bacillus subtilis (Probiotic), an essential oil blend (carvacrol , cinnamaldehyde, cineol and pepper extract) and their combination in the performance and expression of genes related to digestion and absorption in coob® broilers, by RT-qPCR. Basal diet was used as negative control and the avilamycin AGP as positive control. One thousand, three hundred and twenty male broiler chicks from Coob® strain were divided among five treatments, in 6 pens of 44 chicks each. Birds were raised following breeder’s recommendations. Performance was assessed in terms of feed intake (FI), weight gain (WG) and feed conversion ratio (FCR) recorded at 7, 21 and 42 days of age. At these same ages, one bird per pen (N=6), was slaughtered to collect the mucosa of the ileum for RT-qPCR analysis. The investigated genes were: aminopeptidase N (APN), sucrase isomaltase (SI), maltase-glucoamylase (MGA), intestinal transporter peptide-1 (PEPT1), transporter of glucose and galactose Na+ dependent-1 (SGLT-1), glucose transporter, galactose and fructose independent Na+-2 (GLUT -2) and ATP ase Na+/ K+ (ATP1A-1). Except for an increased feed intake presented in birds fed probiotics in relation to fed AGP at 21 days, no differences were found in broiler performance during the experiment. Regarding gene expression, at 7 days, birds treated with AGP presented lower (p<0.05) expression of ATP1A-1 mRNA than the negative control. At 21 days, birds fed with the combination of probiotics and essential oil showed lower mRNA concentration of MGAM than those fed with AGP. In addition, no difference was observed in gut gene expression at 42 days. The lack of difference in growth performance between treatments could be due to the environment in which the birds were raised, more hygienic than that normally found in poultry farms. Moreover the changes in ATP1A-1 and MGAM RNA expression observed herein highlight the role of feed additives in host gut enzymes and transporter gene expression. These results encourage analysis of brush border enzymes activity, jejunum morphometry and indirect absorption trials of glucose in the jejunum, which are underway.
Keywords: broiler, feed additives, gene expression, intestine, RT-qPCR