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 (R) 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.