Author(s): Banaszkiewicz Teresa
Keywords:broiler chickens, crude phosphorus, performance, phytase, rape cake
The aim of this study was to evaluate the effect of high rape cake content and phytase added to phosphorus and calcium deficient diets on the nutritive value for broiler chickens. Two experiments were performed: a growth experiment on four groups of one-day-old broilers Ross 308, 30 birds per group (6 replications x 5 birds) and a digestibility experiment on 60 chickens divided into four groups of 20 birds (4 replications of 5 birds). The digestibility of the starter diets were evaluated on chickens at 7 days of age and of grower diets at 28 days of age. The diets used in the digestibility tests were the same for the growth trial. In the growth experiment four diets were prepared for the due periods: starters (1-21 day) and growers (22-49 day of chicken life). The control diet (SBM) did not contain rape cake, while experimental diets contained 15% (starters) and 20% (growers) rape cake of Lirajet cultivar. The experimental diet denoted RC HP had P and Ca contents equal the control diet (phosphorus about 7.5 g and calcium about 10 g.kg-1), while the diet denoted as RC LP contained less P and Ca (5.8 g and 6.8 g.kg-1 respectively) than the control and RC HP diets. The diet denoted RC LP+ Phy was supplemented with an enzyme preparation containing phytase at a quantity of 875 FYT.kg-1. Application of 15% of rape cake into starter and 20% into grower diets (RC HP) allowed for similar body weights and feed conversion ratio as the control group, whereas reduction of phosphorus and calcium content in the starter diet (RC LP) significantly decreased body weight at day 21. The addition of phytase to the starter diet with low level of phosphorus and calcium showed the tendency to improve body weight in this period. Application of rape cake into starter and grower diets had poor effects on fat digestibility in all groups, whereas supplementation of grower diets with a low level of phytase phosphorus and calcium improved the digestibility of total phosphorus in comparison to the control and RC HP diets. A tendency to improve the performance results for diets with rape cake (RC HP) in comparison to the control diet in the second period of fattening (grower diets) was observed. Application of rape cake into the diets had a significantly beneficial effect on slaughter yield, fleshiness and fatty acid composition of meat, but not so on the heart muscle, whereas phytase did not have an influence on slaughter results. It was concluded that rape cake can be used in broiler diets, but a quantity of 15% in the starter and 20% in the grower diet may have a negative effect on the heart of so fed birds.
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