Influences of Feeding Conventional and Semisynthetic Diets and Transport of Broilers on Weight Gain, Digestive Tract Mass, and Plasma Hormone and Metabolite Concentrations

Two replicate experiments were done to investigate if special diets provided to broilers in their last phase of life could reduce the negative effects of feed withdrawal and transport without an increased content of the digestive tract. In each experiment, 240 broilers were used. The experiments consisted of 2 interventions: the feed intervention and the transport intervention. The feed intervention took 72 h, in which broilers had full access to a conventional grower diet, a conventional grower diet with an increased carbohydrate level, a conventional grower diet with an increased fat level, a semisynthetic diet, or a semisynthetic diet with an increased carbohydrate level. The diets differed remarkably in carbohydrate content; carbohydrate content was approximately 67% in the semisynthetic diets and 42%, on average, in the conventional diets. Moreover, all of the carbohydrates in semisynthetic diets were highly soluble and digestible. The diets were compared with a feed withdrawal period of 24 h before transport. The transport intervention took 3 h; broilers were caught, crated, loaded, transported for 1.5 h, and had to wait in the crates for 1 h thereafter; or remained in the pens. After the transport intervention, blood samples were taken to determine plasma corticosterone, triiodothyronine, glucose, lactate, uric acid, nonesterified fatty acid, and triglyceride concentrations. Also, changes in live weight (LW) and digestive tract mass were assessed. The LW losses of broilers fed with semisynthetic diets after transport were 0.24% per hour less than of feed-withdrawn broilers. Moreover, intake of semisynthetic diets was approximately 200 g, whereas the intake of conventional diets was approximately 300 g. Therefore, the digestive tract mass as a percentage of LW was lower for semisynthetic-fed broilers in comparison with conventional-fed broilers, which can lead to a lesser degree of contamination during evisceration. No increase of corticosterone was found due to transport in semisynthetic-fed broilers. Semisynthetic feed with high carbohydrate concentration could be a good alternative for the feed withdrawal period held before transportation to the processing plant.