Study Looks At Calcium In Canola Meal As Part Of Pig Diet
URBANA, ILL.
When formulating diets for pigs, it is more accurate to use values
for standardized or true nutrient digestibility than values for apparent
nutrient digestibility because the former are additive in mixed diets.
Research at the University of Illinois is helping to determine the true
digestibility of calcium in swine diets.
Hans H. Stein, a professor of animal sciences at the U of I, led the
team that conducted the study. “We know that there are endogenous losses
of calcium in cattle and chickens, and our hypothesis was that the same
is true for pigs,” Stein said. “We also wanted to determine if adding
microbial phytase to the diets would affect endogenous losses of
calcium.”
Stein’s team set out to determine the apparent total tract
digestibility (ATTD) and true total tract digestibility (TTTD) of
calcium in canola meal without and with microbial phytase. They fed
growing pigs four diets containing 0.08, 0.16, 0.24, or 0.32 percent
calcium. All of the calcium in the diets came from canola meal, which is
one of the few ingredients that contain both phytate and appreciable
amounts of calcium. In addition, they fed four diets that were identical
to the first four except that they also contained 1,500 units per
kilogram of microbial phytase.
In diets both with and without added phytase, the ATTD of calcium
increased as the calcium level in the diets increased. This indicated
that there was endogenous loss of calcium. Using regression equations,
the researchers estimated that the total endogenous loss of calcium was
0.160 g/kg dry matter intake (DMI) for pigs fed diets with no added
phytase, and 0.189 g/kg DMI for pigs fed diets containing microbial
phytase. These values were not statistically different, demonstrating
that phytase doesn’t affect endogenous loss of calcium, Stein said.
Next, values for the TTTD of calcium were calculated by correcting
the ATTD for total endogenous losses. Unlike ATTD, the TTTD of calcium
was not affected by the level of calcium in the diet. The ATTD and TTTD
of calcium were both greater in diets containing added phytase than in
diets with no phytase added.
Stein said that the results bore out his team’s hypothesis.
“There is a measurable loss of endogenous calcium from the
gastrointestinal tract of pigs,” he said. “The fact that TTTD values are
unaffected by dietary calcium levels indicates that the only reason
ATTD increases as dietary calcium increases is because of the reduced
contribution of endogenous calcium to the total output.
“Because TTTD values for calcium were not influenced by the level of
calcium in the diets, we expect these values to be additive in mixed
diets,” he added. “It is, therefore, necessary to take endogenous losses
of calcium into account when formulating diets for pigs.”
Future work will focus on determining the digestibility of calcium in additional feed ingredients.
The study, “Endogenous intestinal losses of calcium and true total
tract digestibility of calcium in canola meal fed to growing pigs”, was
recently published in the Journal of Animal Science. It was co-authored
by Caroline González-Vega and Yanhong Liu of the University of Illinois
and Carrie Walk of AB Vista Feed Ingredients (Marlborough, UK). The full
paper is available at http://www.journalofanimalscience.org/content/91/10/4807.full.∆