Impact of the oxidative quality of fish oils in feeds on the composition and oxidative stability of chicken and rabbit meat

The use of fish oils in animal feed has been largely studied due to their particular fatty acid composition; however, no much attention has been paid to the relevance of the oxidative quality of fish oils on animal health and meat composition and stability. Here, two fish oils (that were available as feed ingredients in the current market) presenting a different oxidative quality [i.e. a thiobarbituric (TBA) value of 65 vs 2819μg MDA/kg, and a % polymers of 0.21 vs 2.65] were added to chicken and rabbit feeds, in order to study their effects on the fatty acid composition and oxidative stability of meat, liver and plasma. This study shows that not only the fatty acid composition of fish oils, but also their oxidative quality affects the final nutritional and stability properties of meat, liver and plasma. A 100% increase in TBA value occurred in chicken meat from animals fed highly oxidised fish oil, and similar trends were observed in rabbit meat. This might be related to the 42% decrease observed in chicken meat α-tocopherol (αT) content, although the absorption of certain secondary oxidation compounds from fish oil could not be excluded. The αT content of chicken and rabbit meat, liver and plasma varied according to the αT content in the corresponding feed. However, these differences were not always directly proportional, suggesting that certain factors could impair availability of the tocopherol supplied by the feed. Susceptibility to oxidation (measured as peroxide values obtained through the FOX induced method) showed some differences between tissues and species, which might be related to differences between the PUFA/αT ratios in each type of sample. Both chicken and rabbit meat and tissues were enriched in n-3 fatty acids, but the amounts varied depending on the content of n-3 fatty acids in the fish oil, reaching values around 1000mg/100g in chicken and 230mg/100g in rabbit meat.