Diet density during the first week of life: Effects on growth performance, digestive organ weight, and nutrient digestion of broiler chickens

The current study aimed to investigate whether diet density affects growth performance and nutrient digestion during the first wk after hatch and digestive organ weight at 7 d of age. Effects were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The dietary fat level was increased through soybean oil inclusion. Amino acids, minerals, and the premix were increased at the same ratio as dietary fat. Consequently, diets were kept neither isocaloric nor isonitrogenous. Broiler chickens were weighed on d 0 and d 7 after hatch, whereas feed intake was measured daily. Excreta produced from d 0 to d 7 was collected at d 7. Dietary dry matter and nitrogen metabolizability, as well as fat digestibility were calculated as an average over 7 days. Broiler chickens were sampled at d 7 to determine carcass yield, breast meat yield, and organ weights. Average daily gain (P = 0.047) and average daily feed intake (P < 0.001) decreased linearly as diet density increased, while gain to feed ratio increased linearly (P < 0.001). An increased diet density resulted in a linear decrease of crop, liver, and pancreas weight relative to body weight (BW; P < 0.05). Duodenum, jejunum, ileum, and cecum length (expressed as cm/kg of BW) and empty weight (as % of BW) increased linearly with increased diet density (P < 0.05). Dietary dry matter metabolizability decreased linearly as diet density increased (P < 0.001), whereas fat digestibility and nitrogen metabolizability were not affected (P > 0.05). In conclusion, one-week-old broiler chickens respond to increased diet densities by increasing intestinal weight and length, while decreasing liver and pancreas weight. This may be an adaptive response to cope with an increased nutrient concentration in the diet.