COMPARISON BETWEEN STEEPING AND PELLETING A MIXED DIET AT DIFFERENT CALCIUM LEVELS ON PHYTATE DEGRADATION IN PIGS

The degradation of phytate (inositol hexaphosphate) in the stomach, sm all intestine and colon was studied in 36 female pigs. A comparison wa s made between steeped (9 h, room temperature, feed:water 1:2.5) and p elleted diets with or without calcium carbonate supplementation (12.5 g kg(-1)). The diet was composed of barley, rapeseed cake and peas in the proportion 70:15:15. Dietary and intestinal content of phytate and its hydrolysis products (inositol penta-, tetra-and triphosphates) we re determined using HPLC ion-pair chromatography. Steeping the feed fo r 9 h at room temperature reduced the phytate content by 45% and incre ased the amount of free phosphorus threefold, Pelleting the diet reduc ed phytate content by 7%. Supplementation with Ca decreased dietary ph ytate reduction. Steeping of the diet reduced ileal phytate content by 40% compared with pelleting. Apparent phosphorus absorption from ilea l digesta was 10% lower when pigs were fed the pelleted diet, as compa red to the steeped diet. Calcium carbonate supplementation impared ino sitol hexaphosphate degradation in the colon of pigs, but did not affe ct phytate degradation in the stomach and small intestine. Calcium car bonate supplementation, moreover, depressed apparent P uptake in the s tomach/small intestinal region, as well as in the total gastrointestin al tract, for all feed treatments.