Performance and Carcass Traits of Finishing Pigs Fed Low Phosphorus Containing DietsBased on Normal Hulled or Hulless Barley of a Low-Phytate Hulless Barley With andWithout Phytase

摘要

The objective of the present experiment was to determine the effects of phytase supplementation onthe performance and carcass traits of finishing pigs fed diets containing normal hulled or hulless barley or anewly developed low-phytate hulless barley all formulated without a source of inorganic phosphorus. A totalof 72 crossbred pigs weighing an average of 67.9±8.9 kg were assigned on the basis of sex, weight and litter toone of eight dietary treatments in a factorial design experiment. A positive control diet, based on Harringtonbarley, was formulated to meet the pig’s requirements for total phosphorus. Three experimental diets wereformulated based on either Harrington barley (0.28% phytate phosphorus) or the hulless barleys CDC Freedom(0.31% phytate phosphorus) and LP 422H (0.16% phytate phosphorus). The experimental diets were deliberatelyformulated to be below requirements for total phosphorus by removing all of the inorganic phosphorus (i.e.dicalcium phosphate) from the diet so that the diets contained only organic sources of phosphorus. All fourdiets were fed with and without 1000 FTU/kg phytase (Natuphos 5000). The addition of phytase tended toimprove weight gain (p=0.07) and feed intake (p=0.11). Phytase had the greatest effect in the Harrington dietformulated without dicalcium phosphate improving both daily gain (1.01 vs. 1.16 kg/day) and feed conversion(3.07 vs. 2.83). For the barley diets formulated without dicalcium phosphate, daily gain averaged 1.08, 1.11 and1.14 kg/day while feed conversion averaged 2.95, 2.72 and 2.74 for the Harrington, CDC Freedom and LP 422Hdiets, respectively. Neither phytase supplementation nor type of barley had any affect on slaughter weight,carcass weight, dressing percentage or carcass value index. Pigs fed the LP 422H diet without phytase had asignificantly higher lean yield (p=0.03) and lower loin fat (p=0.07) than pigs fed the LP 422H supplemented withphytase. The overall results of this experiment indicate that the performance of pigs fed low-phosphorus dietscontaining phytase is generally improved over unsupplemented diets. In addition, the performance of pigs fedhulless barley-based diets formulated without inorganic phosphorus is superior to that of pigs fed hulledbarley-based diets formulated without inorganic phosphorus. Finally, the performance of pigs fed low-phytatehulless barley formulated without a source of inorganic phosphorus but supplemented with phytase is at leastequal to that of pigs fed diets containing normal-phytate barley supplemented with inorganic phosphorus.Since inorganic phosphorus sources tend to be expensive, a reduction in their use could lower ration coststhereby increasing the potential profitability of swine production.