Interactive effects of dietary grain and supplemental fat sources on growth performance and carcass characteristics of broiler chickens

The current study investigated if grain type or supplemental fat sources affect or interact for growth performance and nutrients digestibility in broiler chickens offered starter and grower diets with lower metabolizable energy (ME) than breeder recommendations. The experiment was conducted using a completely randomized design with a 3 × 3 factorial arrangement of treatments with three grains (wheat, sorghum, barley) and three fat sources (canola oil, poultry fat, and beef tallow), resulting in nine treatments, each replicated eight times with 25 birds per replicate. Diets were fed in starter (0-10 days), grower (10-22 days), finisher (22-35 days), and withdrawal (35-42 days) phases. Starter and grower diets were formulated to 2875 and 2975 kcal/kg ME, 100 and 75 kcal/kg lower than breeder recommendations. Nutrient digestibility was assessed on day 33, and carcass characteristics were evaluated on day 42 of the trial. There was no significant effect of grain or fat source on body weight gain and feed conversion ratio (FCR) over the starter and grower phases (P > 0.05). There were no interactions of feed grain and fat sources on overall growth performance and age to 2.5 kg body weight (P > 0.05). As the main effect, sorghum-based diets significantly increased overall FCR (0-42 days) compared to wheat- and barley-based diets (P < 0.05). Regardless of fat source, barley-based diets decreased breast meat yield and increased fat pad deposition (P < 0.05). Sorghum-based diets resulted in the lowest ileal starch digestibility (P < 0.05). An interaction between grain and fat source (P < 0.01) showed that poultry fat and beef tallow in wheat-based diets improved crude protein digestibility compared to sorghum- and barley-based diets. In summary, these results indicate that all three grain and fat sources tested in this study can be incorporated into broiler chicken diets without significantly impacting growth rate. However, sorghum-based diets, irrespective of the supplemental fat source, result in lower starch digestibility and approximately a 2-point increase in feed conversion.