To determine true digestibility of nutrients, endogenous losses from the digestive tract must be measured. Because consistent values for endogenous losses of fat (ELF) in pigs have yet to be determined, the calculation of fat digestibility has mostly been limited to apparent digestibility.

Endogenous losses of fat may be influenced by the form of fat – extracted or intact – and by the concentration of fiber in the diet. The objective of this experiment was to determine the effect of the form of dietary fat on ileal and total tract digestibility of fat in growing pigs. To do so, it was necessary to measure endogenous losses of fat and to correct for the difference in amounts of dietary fiber in diets containing extracted fat and diets containing intact fat.

Most corn hybrids grown in the US are genetically modified to resist certain pests or to tolerate certain herbicides. Numerous studies have been conducted to determine the nutritional value of corn that is genetically modified for pest resistance, but there are no published reports about feeding corn that has been modified for both pest resistance and insecticide tolerance to pigs. Investigation into the nutritional value of such corn is, however, warranted, because the use of crops with multiply stacked traits is rapidly increasing; approximately 35 million acres of crops with double- and triple-stacked traits were planted in the United States in 2006.

Two experiments were, therefore, conducted to determine if the nutritional value of corn grain with multiple genetically modified traits is different from that of nontransgenic corn. The hypothesis in both experiments was that pigs fed transgenic corn would not differ in growth performance or carcass characteristics from pigs fed nontransgenic corn.

Kil, D. Y., T. E. Sauber, H. H. Stein. 2007. Effect of form of fat and NDF addition on apparent ileal and apparent total tract digestibility of fat in diets fed to growing pigs. J. Anim. Sci. 85(Suppl. 1):438 (Abstr.) Link to abstract (.pdf)

Stein, H. H., T. Sauber, D. Rice, M. Hinds, D. Peters, G. Dana, and P. Hunst, 2004. Comparison of corn grain from biotech and non-biotech counterparts for grow-finish pig performance. J. Anim. Sci. 82(Suppl.1):328 (Abstr.) Link to abstract (.pdf)