Effects of phytase on growth and slaughter performance, digestibility and nitrogen and mineral balance in heavy pigs

The study aimed at evaluating the effects of phytase (Ronozyme® NP) to the diet of fattening pigs. In comparison with a control diet (C) which included 0.5% calcium salt (CaHPO4), two diets without CaHPO4 were tested: 150Phy and 300Phy, which contained 150 and 300 mg phytase/kg, respectively. Sixty barrows of about 47 kg body weight (BW) each were randomly divided into 3 groups of 20 animals each, every group split into 5 pens. Average daily gain (ADG), feed intake and feed conversion ratio (FCR) were registered. The trial was divided into 2 phases: 0 to 68 days (47 to 100 kg BW) and 69 to116 days (100 to 140 kg BW). During phase II, 6 pigs/diet were housed in individual metabolic cages for the digestibility-balance trial. Addition of phytase resulted in higher ADG (723, 783 and 772 g/d for C, 150Phy and 300Phy, respectively) and improved FCR (2.84, 2.64 and 2.65) in phase I. No differences were registered in phase II, though a better FCR was overall observed. All slaughter parameters and the total tract apparent digestibility (TTAD) of nutrients - except for calcium (Ca) and sodium (Na) -, were similar among treatments. Likewise, total nitrogen (N) excretion did not differ across treatments. Phosphorous (P) excreted for C, 150Phy and 300Phy was 47.1, 53.3 and 52.5% of the P. Trace-minerals showed similar retentions among diets. Phytase effectively improved growth performance until 100 kg BW at both inclusion levels. Yet, it did not improve growth performance, digestibility, N and P balance in heavier animals.