Ruminal and post-ruminal phytate degradation of diets containing rapeseed meal or soybean meal.

This study aimed to investigate ruminal and post-ruminal degradation of phytic acid (InsP6) in diets containing either rapeseed meal (RSM) or soybean meal (SBM). In Experiment 1, the effective degradability of crude protein (CPED) and InsP6 (InsP6ED) was evaluated by incubating RSM and SBM in situ in three rumen-fistulated lactating Jersey cows for 2, 4, 6, 8, 16, 24, 48 and 72 h, and calculating effective degradability at rumen passage rates of 2% and 5%/h. In Experiment 2, eight wethers were assigned for 8 weeks to two dietary treatments (Diet RSM and Diet SBM) containing 150 g of either meal and 100 g of maize silage per feeding time and had free access to hay and water. Titanium dioxide (TiO2) was added to the diets for the last 5 days of the study. The wethers were then stunned, exsanguinated and digesta from the reticulo-rumen, omasum, abomasum, jejunum, colon, and rectum were sampled. In Experiment 1, the InsP6ED of RSM (InsP6ED2: 83%; InsP6ED5: 64%) decreased almost identically to that of CPED with increasing passage rate (CPED2: 78%; CPED5: 63%) and was significantly lower than that of SBM (InsP6ED2: 93%; InsP6ED5: 85%). In Experiment 2, ruminal InsP6 disappearance was significantly higher in wethers fed Diet SBM (89%) than in those fed Diet RSM (76%). Total post-ruminal InsP6 degradation was 6% for Diet RSM and 4% for Diet SBM (p = 0.186). The total tract InsP6 disappearance was higher in Diet SBM (93%) than in Diet RSM (82%). Considering higher InsP6 contents in RSM, Diet RSM resulted in significantly higher amounts of ruminally (Diet RSM: 4.5 g/d; Diet SBM: 3.4 g/d) and total tract (Diet RSM: 4.9 g/d; Diet SBM: 3.5 g/d) degraded InsP6. InsP5 was quantified in most of the digesta samples after feeding Diet RSM but was not detectable in the majority of digesta samples for Diet SBM. Concentrations of myo-inositol (MI) tended to be higher (p = 0.060) in the blood plasma of wethers fed Diet RSM. The consistency between ruminal InsP6 disappearance in wethers and in situ calculated InsP6ED2, along with the very low extent of post-ruminal InsP6 degradation, suggests that at a low rumen passage rate, InsP6-P from the feed becoming available to ruminants is almost entirely from InsP6 degradation in the rumen.

Effects of calcium level and source, formic acid, and phytase on phytate degradation and the microbiota in the digestive tract of broiler chickens.

BACKGROUND: Diet acidification, dietary calcium (Ca) level, and phytase supplementation are known influences on the microbial community in the digestive tract and on phosphorus (P) utilization of broiler chickens. Effects of dietary factors and microbiota on P utilization may be linked because microorganisms produce enzymes that release P from phytate (InsP6), the main source of P in plant feedstuffs. This study aimed to detect linkages between microbiota and InsP6 degradation by acidifying diets (i.e., replacing Ca carbonate (CaCO3) by Ca formate or adding formic acid to CaCO3-containing diets), varying Ca levels, and supplementing phytase in a three-factorial design. We investigated i) the microbial community and pH in the digestive tract, ii) prececal (pc) P and Ca digestibility, and iii) InsP6 degradation. RESULTS: All factors under investigation influenced digesta pH and the microbiota composition. Predicted functionality and relative abundance of microorganisms indicated that diets influenced the potential contribution of the microbiota on InsP degradation. Values of InsP6 degradation and relative abundance of the strains Lactobacillus johnsonii and Lactobacillus reuteri were correlated. Phytase supplementation increased pc InsP6 disappearance, with differences between Ca levels, and influenced concentrations of lower inositol phosphate isomers in the digestive tract. Formic acid supplementation increased pc InsP6 degradation to myo-inositol. Replacing CaCO3 by Ca-formate and the high level of these Ca sources reduced pc InsP6 disappearance, except when the combination of CaCO3 + formic acid was used. Supplementing phytase to CaCO3 + formic acid led to the highest InsP6 disappearance (52%) in the crop and increased myo-inositol concentration in the ileum digesta. Supplementing phytase leveled the effect of high Ca content on pc InsP6 disappearance. CONCLUSIONS: The results point towards a contribution of changing microbial community on InsP6 degradation in the crop and up to the terminal ileum. This is indicated by relationships between InsP6 degradation and relative abundance of phosphatase-producing strains. Functional predictions supported influences of microbiota on InsP6 degradation. The extent of such effects remains to be clarified. InsP6 degradation may also be influenced by variation of pH caused by dietary concentration and solubility of the Ca in the feed.