Evaluating the quality of feed fats and oils and their effects on pig growth performance

Authors: SHURSON, GERALD - University Of Minnesota; Kerr, Brian; HANSON, ANDREA - University Of Minnesota

Submitted to: Journal of Animal Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2015
Publication Date: 4/1/2015
Publication URL: http://handle.nal.usda.gov/10113/1239496
Citation: Shurson, G., Kerr, B.J., Hanson, A. 2015. Evaluating the quality of feed fats and oils and their effects on pig growth performance. Journal of Animal Science and Biotechnology. 6:1-11.

Interpretive Summary: Peroxidation of lipids is a dynamic process which produces numerous compounds which have been associated with deleterious effects on animal health, metabolic oxidative status, and growth performance. Consequently, these effects can significantly reduce energy and nutritional efficiency and increase the cost of food animal production. However, accurate measurement of the extent of lipid peroxidation and relationship to animal health and performance is a major obstacle that must be overcome to optimize energy and nutrient utilization efficiency in animal feeds. Currently, there are no universally accepted analytical standards for measuring lipid peroxidation, and various measures are used in different segments of the food, agriculture, and lipid industries. Animal nutritionists have historically assumed that peroxide value and thiobarbituric acid reactive substances assays are reliable indicators of the extent of lipid peroxidation in feed fats and oils. However, a review of the scientific literature and recent studies indicate that the use of peroxide value or thiobarbituric acid reactive substances as single indicators do not adequately characterize the extent of lipid peroxidation as it relates to animal performance, and may often provide misleading results. The fatty acid profile of the lipid and the peroxidative conditions to which lipids were exposed (e.g., storage or processing temperature and duration) appear to be important when selecting an indicative assay. Therefore, use of combinations of indicative peroxidation assays that measure compounds at different stages of peroxidation is recommended to provide a more accurate assessment of peroxidation of lipids used in animal feeds, and determine dietary thresholds of peroxidation compounds at which animal growth is impaired. Although the addition of some dietary antioxidants have been shown to improve animal performance when feeding peroxidized lipids, the type of antioxidant and the dietary peroxidation conditions where they are beneficial needs to be defined. Research results described in this report provide nutritionists at universities, feed companies, allied industries, and livestock production facilities information on how to critically evaluate lipid quality for the use of feed lipids in livestock diets.

Technical Abstract: Optimizing energy utilization efficiency of swine diets is essential because energy represents the greatest proportion of total diet cost. Various feed fats and oils, as well as other feed ingredients containing moderate amounts of lipid, provide significant amounts of energy to swine diets. However, there is large variation in composition, quality, feeding value, and price among lipid sources. Common measures of lipid quality include moisture, insolubles, and unsaponifiables (MIU), titer, and free fatty acid (FFA) content, which are used to ensure that lipids meet trading specifications, but provide limited information regarding their feeding value. Lipid peroxidation is an important quality factor that is related to animal growth performance and health, but maximum tolerable limits in various lipids have not been established. Several indicative assays can be used to detect the presence of various peroxidation compounds, but due to the complexity and the numerous produced and degraded during peroxidation process, no single method can adequately determine the extent of peroxidation. The most common indicative tests used in the feed industry are peroxide value (PV), thiobarbituric acid reactive substances (TBARS), and anisidine value (AnV). Until further information is available, using the combination of these three predictive tests can provide a reasonable assessment of the extent of peroxidation in a lipid at a reasonable cost, but the fatty acid composition of the lipid should be considered when selecting specific assays. Predictive tests can also be used to estimate the stability or susceptibility of lipids to peroxidation and include active oxygen method (AOM), oxygen stability index (OSI), and oxygen bomb method (OBM). These tests can be useful when considering the need to add antioxidants to lipid sources during storage under pro-oxidant conditions. Results from limited studies in pigs and broilers have shown inconsistent effects of peroxidation on energy value and nutrient digestibility of various lipid containing ingredients. These inconsistent responses may be due to the choice of indicative tests used to characterize the extent of peroxidation of lipids used in this study. However, an extensive review of 16 published studies with pigs has shown an average decrease of 11.4% in growth rate, 8.8% feed intake fed isocaloric diets containing peroxidized lipids compared to diets containing unperoxidized lipids of the same source. Furthermore, serum vitamin E content was generally reduced and serum TBARS content was increased when peroxidized lipids were fed in these studies, suggesting that feeding peroxidized lipids negatively affects metabolic oxidative status of pigs. Although determining metabolic oxidative status of pigs is complex and involves several indicators such as serum TBARS, PPARa activation in the liver, and measures of gut barrier function, there is an increasing amount of information indicating that peroxidized lipids cause metabolic oxidative stress in pigs. However, it is unclear if antioxidants are useful additions to lipids to maintain optimal nutritional value, or if their addition to swine diets is beneficial in overcoming a metabolic oxidative challenge.