Inclusion of slowly digestible starch source is a promising strategy than reducing starch to protein ratio in low protein broiler diets

The present study investigated the effects of low protein diets with different starch sources and starch to protein ratio on growth, digestibility, intestinal health, caecal short chain fatty acids (SCFAs), serum cholesterol and triglycerides in broiler chickens. Eight hundred one-day-old male broiler chicks (Ross 308) were randomly allotted to one of 4 dietary treatments with 10 repeats and 20 birds in each repeat. The dietary treatments included 1) a standard protein corn-SBM based diet (SP), 2) a low protein corn-SBM based diet (LPI) without reduced starch: protein ratio, 3) a low protein corn-SBM based diet (LPII) with reduced starch: protein ratio, and 4) a low protein corn-SBM-peas based diet (LPP) and reduced starch: protein ratio. Soy hulls were added in the LPII and LPP diets to reduce starch: protein ratio. During the experiment period from 11 to 24 d, FI was not affected by the dietary treatments (P > 0.05). The BWG was significantly reduced in the LPI diet compared to the SP diet (P < 0.05). Likewise, FCR deteriorated in LPI and LPII but was better in the SP diet followed by the LPP diet (P < 0.05). The apparent total tract digestibility (ATTD) of dry matter (DM) varied significantly among the dietary treatments (P < 0.01). While ATTD of starch was similar for all the diets except the LPP diet wherein the ATTD of starch was significantly lower (P < 0.001). Ether extract digestibility was also significantly different between the SP and LPII dietary treatments (P < 0.01). The AME and AME(n) values were significantly lower in the LPP diet compared with other dietary treatments (P < 0.001). Nitrogen retention (%) was increased in all the LP diets compared with the SP diet (P < 0.001), but it was significantly better in both LPII and LPP diets compared to the LPI diet. The data showed that cecal SCFAs production was increased in the LPII and LPP compared to the SP and LPI diets (P < 0.001). Further, the production of acetic, butyric, and propionic acids was substantially higher in the LPP diet (P < 0.001). There was no significant difference in gene expression of Claudin-1 and ZO-1 (P > 0.05). However, MUC-2 and GLUT-1 gene expression were significantly downregulated in the LPI diet (P < 0.05). The concentration of cholesterol and triglycerides was significantly increased in the LPI diet (P < 0.001). In conclusion, the addition of peas as a slowly digestible starch source combined with soy hulls in low protein diet helped to partly recover the growth performance and improved cecal SCFAs production compared to other low protein diets with and without reduced starch: protein ratio in broiler chickens.