Assessment of the quality, oxidative status and dietary energy value of lipids used in non-ruminant animal nutrition

Abstract

Background: Fats and oils represent the most concentrated source of energy available to animal nutritionists and form an expensive part of the diet. Thorough understanding of lipid quality and composition are required for efficient and precise diet formulation. Therefore, 724 samples of commercially available fats and oils were assessed for fatty acid profile, oxidation status and energetic value as per the Wiseman equation, with consideration of a correction factor K, which is based on the presence of the energy diluting compounds moisture, impurities and unsaponifiables.

Results: Energy diluting compounds were widespread across fat types and sources. Average MIU (moisture, insoluble impurities and unsaponifiable matter) presence in individual oils was 5.1-28.1 g kg^-1 . Using the adapted Wiseman equation presented in the current paper, which reflects the energy diluting potential of MIU, the calculated energy values of fats and oils is reduced by up to 46% in extreme cases compared to those predicted by the original equation. From the chemical parameters, it is clear that there is limited correlation between individual measures of oxidation, with only weak negative correlations between 2-thiobarbituric acid (TBA) and Oxidative Stability Index (OSI) values (Spearman's ρ between -0.20 and -0.39) and a weak to moderate negative correlation between peroxide value (PV) and OSI (Spearman's ρ between -0.20 and -0.59) for certain fats and oils. A moderate to very strong positive correlation between FFA and the energy diluting compounds MIU was observed for all animal fats (Spearman's ρ between 0.40 and 1.00).

Conclusion: The current report highlights the large variation in composition and quality seen in commercially available fats and oils and encourages ongoing analysis and assessment rather than reliance on published values. The results also indicate that the oxidation parameters when interpreted as separate values lack the power of inferring oil and fat quality. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: apparent metabolizable energy; broilers; digestible energy; lipids; pigs.

Figure 1

Principal component analysis of 11 predominant fatty acids for animal fats (observation plot pane A1, biplot pane A2) and nine predominant fatty acids for plant oils (observation plot pane B1, biplot pane B2). Ellipses indicate the 95% confidence interval.

Figure 2

Proportion of samples from each individual oil type displaying limited (‘good’), initial, or substantial signs of oxidation according to the three tests: PV, TBA and OSI.

Figure 3

Comparison of the energy value for individual samples based on both the original Wiseman equation and the modified equation including MIU as energy diluting component of soybean oil, sunflower oil, rapeseed oil, tallow, lard and poultry fats tested.