Comparing oxidation of fatty acids in pigs fed starch, animal fat or soy oil using 13C labelled fatty acids

A study was conducted to compare oxidative loss of dietary starch, unsaturated and saturated fats in growing pigs. Eighteen barrows (28 kg BW) were assigned to one of 3 dietary treatments, in which starch (20%), animal fat (9.7%) or soy oil (9.1%) were exchanged isocalorically. Diets were fed twice daily at a rate of 1200 kJ DE/(kg BW0.75.d) for an adaptation and experimental period of 7d each. A bolus dose of [U-13C] labeled glucose was administered 1 h after feeding on d 1, and [U-13C] bolus doses of linoleic (C18:2), stearic (C18:0) and oleic acid (C18:1) with the feed on d 2, 4 and 6, respectively. Pigs were housed individually in climate-respiration chambers. Based on 13CO2 measurements by non-dispersive infrared absorption, 13C recoveries of tracers were calculated (Table 1). Complete energy balances were measured using indirect calorimetry. Exchanging starch for fat, regardless of its source, reduced heat production by 4%. Cumulative recovery of 13C from labeled glucose was unaffected. Replacing starch by fat increased the 13C recovery of all fatty acid tracers used (P