Effects of dietary Ca/P ratio, P level and microbial phytase supplementation on nutrient digestibilities in growing pigs: breakdown of phytic acid, partition of P and phytase activity along the intestinal tract
M. Seynaeve et al., Effects of dietary Ca/P ratio, P level and microbial phytase supplementation on nutrient digestibilities in growing pigs: breakdown of phytic acid, partition of P and phytase activity along the intestinal tract, J ANIM PHYS, 83(4-5), 2000, pp. 193-204
Citations number
63
Categorie Soggetti
Veterinary Medicine/Animal Health
Journal title
JOURNAL OF ANIMAL PHYSIOLOGY AND ANIMAL NUTRITION-ZEITSCHRIFT FUR TIERPHYSIOLOGIE TIERERNAHRUNG UND FUTTERMITTELKUNDE
Light female pigs (26-61 kg) provided with a simple T-cannula about 10 cm p
roximal to the ileo-caecal valve, were used in two experiments to investiga
te the effects of Ca/P ratio, P level and supplementation with phytase (500
FTU/kg) on the breakdown of phytic acid (IP6), partition of P and phytase a
ctivity along the alimentary tract in pigs. In experiment 1, two Ca/P ratio
s (1.5/1 and 2.2/1) and two P levels (0.34 and 0.47%) were tested according
to a 2 x 2 factorial arrangement within a Latin square design. In experime
nt 2, the maize-tapioca-soybean meal-based diets of experiment 1 were suppl
emented with phytase (500 FTU/kg). No lower inositolphosphates, but substan
tial phytase activities were detected in the ileal digesta and faeces. Sign
ificant faecal amounts of IP6 were found only for diets with a wide Ca/P ra
tio, due to its antagonistic effect on phytase activity. The addition of fe
ed phosphate increased the proportion of inorganic P (Pi), but reduced the
phytase activity in the small intestine. Breakdown of IP6 at the terminal i
leum was 16.2% for the diets without phytase supplementation and was due to
microbial activity. Supplementation with phytase tripled the pre-caecal br
eakdown of IP6. However, the liberated Pi along the small intestine was not
absorbed by the animal, but incorporated in microbial biomass as shown by
lower organic matter (OM) disappearance and unaffected P disappearance (SEY
NAEVE et al.; J. Anim. Physiol. a. Anim. Nutr 83, 36-48, 2000), increased p
hytase activity (+28%), higher organic nonphytate P fraction (+36%) and hig
her amounts of bacterial residues or intestinal cell debris residues (+43%)
in the small intestine. The digestibility experiments indicate that P abso
rption from feed phosphate takes place to a large extent proximally to the
ileo-caecal valve. The phosphorus that is liberated by added microbial phyt
ase from phytate in feedstuffs causes an increase in the microbial populati
on in the small intestine of pigs but only becomes available for absorption
by the pig in the caecum/colon region.