Abstract
Supplementing swine diets with phytase increases phosphorus release by approximately 50% from cereal phytates. The increase in phosphorus availability allows for a reduction in dietary phosphorus supplementation from mineral sources and decreases the environmental impact of pork production through a decrease in phosphorus excretion. Superdosing phytase has been reported to boost swine productivity, improve the digestibility of other nutrients, and mitigate the antinutritional effects of phytates. However, there are significant cost differences among phytase products. Bacterial phytases are considered more modern, often with a higher cost of inclusion. A study was conducted with 288 piglets that were 21 d of age and weighed 6.43 ± 0.956 kg. Pigs were divided into four groups. Each group of pigs was fed a different experimental diet varying in phytase source and level: fungal phytase (Aspergillus niger) at 500 FTU/kg of diet, fungal phytase at 2,000 FTU/kg, bacterial phytase (Escherichia coli) at 500 FTU/kg, and bacterial phytase at 2,000 FTU/kg. No differences were found for phytase sources or doses on productivity at 14 and 21 d postweaning. However, piglets supplemented with 2,000 FTUs/kg of phytase in the diet during the first 21 d of nursery exhibited a 5.8% better feed conversion (P = 0.02). An interaction between phytase source and dose was observed for average live weight and daily weight gain over the 42-d nursery period (P < 0.05). Supplementing the diet with 2,000 FTU/kg of fungal phytase improved daily weight gain and live weight throughout the experimental period compared to piglets supplemented with 500 FTU/kg of the same phytase source. Additionally, it resulted in better final weights compared to piglets supplemented with 500 FTU/kg of bacterial phytase. Phytase inclusion at 2,000 FTU/kg improved feed conversion by 2.07% over the 42-d nursery period. The most economically favorable feed conversion ratios were observed when supplementing the diet with fungal phytase at 2,000 FTUs/kg.