US - Added fat increases the energy content of swine diets, but it may also affect the digestibility of nutrients. Dr Hans H. Stein, professor of animal sciences at Illinois, and a team of researchers have studied the effects of fat sources with different concentrations of saturated and unsaturated fatty acids on mineral digestibility.
"In pigs, addition of soybean oil to the diets has been shown not to reduce calcium digestibility. However, some studies in pigs and humans have observed the formation of indigestible calcium-fat complexes," says Stein. "These studies used fats that were more saturated than soybean oil."
Therefore, Stein and his team set out to determine the effect of the relative concentrations of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) on the apparent total tract digestibility (ATTD) of minerals in diets fed to pigs.
Five sources of supplemental fat were tested. Soybean oil and corn oil contained about 15 per cent SFA, 26 per cent MUFA, and 57 per cent PUFA. Palm oil and beef tallow contained about 46 per cent SFA, 42 per cent MUFA, and 6 per cent PUFA. The final fat source, choice white grease, contained 39 per cent SFA, 43 per cent MUFA, and 13 per cent PUFA.
The apparent total tract digestibility of calcium, phosphorus, and sulfur was increased in pigs fed diets containing soybean oil, corn oil, palm oil, or tallow compared with pigs fed diets containing no added fat or choice white grease.
Added fat did not affect the ATTD of potassium, manganese, sodium, or zinc, although there was a tendency for magnesium digestibility to be greater in pigs fed diets containing soybean oil or corn oil, compared with pigs fed diets containing tallow or choice white grease.
"The implication of this experiment is that producers can include added fat, whether saturated or unsaturated, in diets for pigs without creating a reduction in digestibility of calcium or other minerals," says Stein. "However, in the case of choice white grease, there was some indication that it had been oxidized, and oxidation may reduce mineral digestibility."
Stein says this observation warrants further investigation.
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