The effects of different dietary crude protein and valine levels on the performance and dietary carbon footprint of Ross-308 roosters

The effects of different dietary crude protein (CP) and valine levels were examined on the live weight, feed conversion ratio (FCR) and protein conversion of roosters as well as on the calculated dietary CO 2 footprint of broiler production. The trial involved seven treatments formulated on a corn–soybean meal base. Compared to the positive control (PC) diet following the Aviagen ’s (2014) recommendations, the LPV0 treatment had reduced CP content without valine supplementation. In five additional treatments (LPV1–5), L-valine was supplemented in increasing quantities . The results suggest that reducing the recommended CP content decreases the final weight. While the average weight of LPV0 birds was 9.5% lower than that of the PC up to day 21, by the end of the 35-day trial, this difference decreased to 7.2% due to similar weight gains registered in the finishing stage. Roosters fed diets with 1.0/1.0/1.05 g/kg of valine supplementation achieved the same weight gain as the PC birds, even over the full trial (P>0.05). The FCR was the same across all treatments between days 1 and 35 (P>0.05). Roosters fed reduced protein, but valine-supplemented diets presented weight gains of 11.2% less protein on average, while the dietary CO 2 footprint of their weight gain was 15.53% lower than that of the PC group. These data suggest that, from day 22, the dietary CP content in broiler diets can be reduced by up to 11% without adversely affecting performance, while also improving protein conversion and reducing the dietary CO2 footprint of the final product.