Sampling time influences the apparent total tract digestible Ca and P equivalence of phytase in weaner pigs during a 21-day study

Abstract

The objective of this study was to investigate the effect of the fecal sampling time on the apparent total tract digestibility (ATTD) of Ca and P and the efficacy of phytase in weaner pigs. During a 21-day feeding trial with 240 weaner pigs (7.4 ± 0.9 kg; 28-day old), fresh and clean fecal samples were grabbed every 2 h from 0900 to 1700 h daily from each pen on d 6–8, 13–15, or 19–21 of the trial. There were five experimental diets including a low Ca and P control diet and the control supplemented with phytase at 500, 1000, 2000, or 3000 phytase units (FYT)/kg feed. Each diet was fed to 6 pens of 8 pigs. All diets included 3 g/kg TiO2. The results showed that increasing supplementation level of phytase linearly and quadratically (P < 0.01) increased ATTD of Ca and P. There was an interaction (P < 0.01) between phytase and sampling time for ATTD of Ca and P because the response curves on d 19–21 were not parallel to those on d 6–8 and d 13–15. The ATTD of Ca in the diets supplemented with phytase was higher (P < 0.05) at the sampling time of d 19–21 of the trial than at other sampling times, which contrasts with unaffected ATTD of Ca in the control diet over the sampling times. In control diet, the ATTD of P was higher (P < 0.05) at the sampling time of d 13–15 of the trial compared to d 19–21; but in the diets supplemented with 2000 or 3000 FYT/kg phytase, the ATTD of P was higher (P < 0.05) at the sampling times of d 13–15 and d 19–21 of the trial than at d 6–8. There was no interaction between phytase and sampling time on the release of digestible P by phytase, but the interaction showed a tendency for digestible Ca release (P = 0.07). The concentration of digestible Ca and P released by phytase increased linearly (P < 0.01) with sampling time. In conclusion, the phytase efficacy in terms of digestible Ca and P release increased with time in this feeding trial with weaners pigs. Therefore, we suggest that the fecal samples should be grabbed at the midpoint of a feeding trial to measure the phytase efficacy in weaner pigs.