Interpretive Summary: Influence of feeding thermally peroxidized soybean oil on growth performance, digestibility, and gut integrity in growing pigs.
By: Surely Wallace
In an article published in the Journal of Animal Science in February 2018, researchers looked at the effects peroxidized soybean oil (SO) heated at different temperatures had on growing pigs. The goal was to see if temperature affected growth performance, gut integrity or nutrient digestibility.
Addition of oils to pig feed is necessary as an energy source. Thermal processing however causes unwanted oxidative breakdown of mono- and polyunsaturated fatty acids. Oils subsequently may become less digestible or palpable due to formation of free radicals and secondary byproducts. Since previous studies noted decreased growth performance and nutrient digestibility in pigs and poultry fed peroxidized lipids, the authors investigated SO processed at different temperatures.
The study period lasted 49 days. Barrows were randomly assigned to a control or one of three treatment groups (n=14 each). The control diet was 10% fresh SO (22.5°C). Processed SO were heated at 45°C for 288 hours, 90°C for 72 hours, or 180°C for 6 hours. Gut barrier integrity was determined by urine lactulose to mannitol ratio (L:M) after an oral challenge. Weight, average daily gain (ADG), average daily feed intake (ADFI), gain to feed ratio (G:F), nitrogen (N) retention and digestibility, and serum tryptophan (Trp) were studied. When required, pigs were housed in individual metabolism crates for urine and fecal collection.
The ADG was lower in pigs fed 90°C SO diet (by approx. 7%) than control, consistent with a previous study. No differences in ADFI were noted. Pigs fed the 45°C SO diet had higher G:F. Digestibility of N was highest in control (88.72%) and lowest in 45°C (87.05%) and 90°C SO (88.19%) diets. Retention of N was higher in control and 45°C diet. Pigs fed 90°C and 180°C SO diets also had reduced serum Trp, without known effects. No difference in L:M ratio were noted.
Overall, any effects that thermal processing temperature of oils added to pig feed might have on growth performance and digestibility needs to be studied in more detail. This small study suggests there were no detrimental effects on gut integrity. However, SO heated at 90°C for 72 hours was correlated with reduced growth performance (lower ADG and digestibility). The authors stress the need for more in-depth studies focusing on specific indices of lipid quality that may be affected by heating temperature, in order to determine any potential causality.
To view the full article, “Influence of feeding thermally peroxidized soybean oil on growth performance, digestibility, and gut integrity in growing pigs,” visit the Journal of Animal Science.