IN SITU DEGRADATION AND FERMENTATION OF A DIET WITH AN EXOGENOUS PHYTASE FOR LAMBS
Close to 70% of phosphorus (P) from cereal grains and oleaginous seeds is linked to phytic acid as phytate, which is little utilized or not at all by non-ruminants. Diets containing more than 50% of the P as phytate will decrease hydrolysis of the phytate by rumen microorganisms. Therefore, the objective of this in situ trial was to evaluate the effect of an exogenous phytase added to a diet for lambs. Treatments were: 0, 540 and 720 g of phytase Ronozyme-HiPhos (DMS Nutritional Products, 5000 FTU/g) added to a 70% sorghum grain diet and fed to 6 Criollo lambs (40 ± 2 kg live BW) with ruminal and duodenal cannulas, and housed on individual metabolic cages during 45 days (plus 15 days for adaptation). The experimental design was a 3x3 Latin Square repeated on time, data were analyzed using GLM procedure (SAS v. 9.2) and treatment means were compared with the Tukey test (P≤0.05). Variables were dry matter intake (DMI), pH and VFA concentration in ruminal fluid, NH3-N and P concentration in ruminal and duodenal fluid, fecal and urine P, and plasma P; samplings were carried out at 3, 6, 9, 12, 24, 48 and 72 h. Phytate of the diet was 67.74% of the total P. For 0, 540 and 720 g phytase, differences (P ≤ 0.05) were found only for DMI (1053.32ab, 988.70b, 1141.32a g/day) and fecal P (2.32a, 2.01ab, 1.85b % P/g DM). Thus, it may be concluded that this exogenous phytase did not change pH, VFA, P in ruminal fluid, P in urine or plasma. But since fecal P excretion was reduced, soil contamination could be decreased.
Keywords: phytase, P excretion, lamb.