Effect of phytase supplementation of rapeseed cake-containing diets on performance and skeletal development in broilers.

Ninety nine broiler females were divided into 9 groups, 11 replicates in each group and fed isonitrogenous and isoenergetic diets with 100/150 g/kg of 4 different rapeseed cakes (RC) or control diet without RC. The level of Ca and available P in RC diets was as in control diet, while in RCP diets it was lowered by 7 and 12%, respectively. RCP diets were supplemented with 1000 U phytase/kg. The intake of RC diets was similar, while BWG lower in some and FCR 5% worse in all RC groups, than in the control group. The type of RC had no effect on tibia parameters, but affected significantly feed intake, BWG, thyroid and kidneys weight. Phytase addition to RCP diets increased thyroid weight (P<0.01) and lowered tibia ash content (P<0.05), but had no effect on tibia weight and its ultimate strength. Introduction Various phytase preparations have proved their efficiency in broiler nutrition. Total phytate P utilization in broilers consuming P-deficient corn-soybean meal diet were reported to reach a plateau around the dose of 500 U phytase/kg diet (Schöner et al., 1993), or to increase up to the dose of 12,000 U/kg diet (Shirley and Edwards, 2003). Information is scarce about the effect of rapeseed products, which are rich in phytate phosphorous, but also in condensed tannins on the activity of exogenous phytase in the digestive tract of chickens. Rutherfurd et al. (2002) found no effect of added phytase on ileal or total P digestibility in broilers fed rapeseed meal-based diet. The aim of the study was to evaluate the effect of phytase on performance and skeletal development in broilers fed diets containing different rapeseed expeller cakes. Materials and Methods Four rapeseed cakes (RC) used in experiment were cold-pressed from 00 rapeseed in different rural mills in Poland, RC 1 was additionally toasted, while RC 4 was additionally extruded. Glucosinolates content of rapeseed cake samples were determined using ISO 91671 method (1992). Three control wheat, maize and soybean meal-based diets, containing nutrients satisfying chickens requirements during starter (1-21), grower (22-35) and finisher (36-42 day of life) periods were prepared. Two sets of each experimental diets were prepared, in both starters contained 100, growers and finishers 150 g/kg RC and protein, energy, lysine and sulphur amino acids content was equalized with the respective control. RC diets were unsupplemented and had P and Ca content equal to the control diet, while RCP diets, due to lower amount of added dicalcium phosphate, contained 7% less Ca and 12% less available P than respective RC diets and were supplemented with 0.2 g/kg (1000 U) of Natuphos 5000 G (BASF) phytase (Table 1). All diets were cold pelleted. Real phytase activity in the feed samples was not measured. Ninety nine day-old broiler females Cobb 500 were randomly allocated into 9 groups, 11 birds in group. For the first week of life chickens were kept in pens, at 8 d they were allocated into individual cages. Birds were given experimental diets ad libitum, body weight and feed intake was measured in weekly intervals. At the end of experiment all birds were killed, the abdominal cavity was opened and liver, thyroid glands, kidneys and abdominal fat were excised and weighed. The right tibia was collected, cleaned of all exterior tissue and frozen.