Intestinal viscosity and metabolizable energy in chickens and turkeys of different ages fed cereal-based diets with or without enzyme supplementation

Two experiments were conducted to assay digesta viscosity and metabolizable energy values of different cereal-based diets with or without enzyme supplementation in growing turkeys and broiler chickens at 3 and 6 weeks of age and in laying hens. Age, feeding and poultry species had interacting effects on digesta viscosity and metabolizable energy. Viscosity was reduced with age in broilers, but energy metabolizability was improved with age more remarkably in turkeys. Growing turkeys gained slightly more energy from the diets as compared to hens. Introduction In poultry feed formulation, the same mean digestibility and energy values are usually applied for different poultry species and for birds of different ages. It is, however, known that nutrient digestibility and metabolizable energy content of a diet may vary according to age of the target birds. For fat digestibility and therefore for metabolizable energy an increasing trend in growing chickens and turkeys seems to be evident (Wallis and Balnave 1984, Plavnik et al. 2000, Palander et al. 2005). Viscosity-reducing hemicellulolytic enzyme supplementations have been widely applied in poultry feeding and widely investigated in broiler chickens. Regarding turkeys investigations have been carried out to a small extent, and comparative information on effects of enzymes in different types of poultry fed different diets is scarcely available. The objective of the present study was to assay digesta viscosity and metabolizable energy values of different cereal-based diets with or without enzyme supplementations in growing broiler chickens at two age periods and in laying hens. Materials and methods In Experiment 1, 252 growing turkeys (B.U.T. 8) and 162 growing broiler chickens (Ross 208) were used. 14 turkeys or 9 broilers were placed in each cage, thus forming 18 replicates for each species. The experimental feed mixtures consisted of ground cereals, soybean meal, vegetable oil and sufficient mineral and vitamin supplementations. 2 g of chromic oxide and 5 g of titanium oxide per 1 kg feed were added to the mixtures as markers. The feeding treatments were composed to form diets which according to general knowledge can be considered to represent sources of soluble (wheat and barley) and insoluble (oats) fibres: 1. a 1:1 mixture of wheat + dehulled barley (WB) 2. oats (O) 3. a 1:1:1 mixture of wheat + dehulled barley + oats (WBO) 4. as 1. + Avizyme 1200, 1.0 g / kg (WB+E) 5. as 2. + O Avizyme 1200, 1.0 g / kg (O+E) 6. as 3. + Avizyme 1200, 1.0 g / kg (WBO+E) The trial periods at 3 and 6 weeks of age consisted of excreta collection of 24 h, an intervening time of one day, and finally a slaughtering day so that the slaughtering days took place at 21 and 42 of age. The diets and excreta was analysed for gross energy and nitrogen for nitrogen corrected metabolizable energy determination. At the slaughtering days, a part of the birds of each cage (7 turkeys and 5 broilers at 3 weeks of age, 4 turkeys and the remaining 4 broilers at 6 weeks of age) were taken for digestive tract sampling. The birds were stunned