Take Home Message

The addition of phytase enzymes to swine diets help pigs better utilize the naturally occurring phosphorus in plant ingredients, so that less supplemental phosphorus is required in the diet. As a result less phosphorus is excreted into the manure and less phosphorus is applied onto the landbase.

Based on the results of this research there would appear to be no benefit to supplementing Phyzyme XP, a microbial 6-phytase, at a rate higher than 500 units of phytase per kilogram of diet.

Background

Phosphorus is an essential nutrient. It is required for bone growth, cell structure, and enzymatic processes, to name a few. However, meeting phosphorus requirements for growing pigs is difficult. That is because approximately 60 % to 70 % of phosphorus in plant-based swine feed ingredients occurs as phytate phosphorus. Phytates are complex molecules that bind phosphorus and other nutrients for storage in seeds and grains.

Monogastric animals lack sufficient intestinal phytase, which is the enzyme required to break down phytate molecules and release bound phosphorus. Several studies have shown that supplementing swine diets with the phytase from various sources improves phytate phosphorus utilization. Adding phytase to swine diets may release bound nutrients and increase their digestibilities. However, the extent of such improvement varies with source of phytase and diet type.

Research

The objective of our study was to investigate the efficacy of a microbial phytase, specifically Phyzyme XP, a microbial 6-phytase, on phytate phosphorus hydrolysis by growingfinishing pigs. Thirty-six individually housed Yorkshire barrows with an average initial body weight of 55.5 kg (+ 4.6 kg) were randomly assigned to dietary treatment based on body weight.

Four wheat-based experimental diets consisted of a positive control formulated to meet NRC requirements for growing pigs, a negative control diet with reduced total phosphorus, or the negative control supplemented with 500 or 1000 units of phytase per kilogram of diet. Wheat was pre-pelleted and crumpled prior to diet mixing in order to inactivate intrinsic phytase. This ensured that any active phytase in the diets was from the microbial test enzyme. Feed and water were provided for ad libitum consumption throughout the experiment. Average daily feed intake, average daily gain, and feed efficiency were measured. The study was conducted over a 14-day period, with 11 days of acclimatization to the experimental diets and 3 days of fecal collection for determining energy and nutrient digestibilities.

Results from this study show that there was no significant dietary effect on feed intake, average daily gain or feed efficiency. Phytase supplementation did improve fecal phosphorus digestibility compared with the nonsupplemented diets (Figure 1).

There was no significant difference in phosphorus digestibility between supplementing phytase at 500 or 1000 units of phytase per kilogram of diet. Supplementing the negative control diet with 500 units of phytase per kilogram of diet improved gross energy digestibility from 86.6% to 87.8%. The effect of phytase supplementation on calcium, crude protein, and dry matter digestibility was not significant, but there was a 3% improvement in dry matter digestibility as a result of phytase supplementation at 500 units per kilogram of diet.

Conclusion

It was concluded that the phytase enzyme evaluated in this study improves phytate phosphorus utilization in growing-finishing pigs. Microbial phytase may also enhance energy and dry matter utilization of the diet. However, there appears to be no benefit to supplementing this particular phytase at a rate higher than 500 units of phytase per kilogram of diet.