Use of recovered frying oils in chicken and rabbit feeds: effect on the fatty acid and tocol composition and on the oxidation levels of meat, liver and plasma

Abstract

The addition of some fat co-and by-products to feeds is usual nowadays; however, the regulations of their use are not always clear and vary between countries. For instance, the use of recycled cooking oils is not allowed in the European Union, but they are used in other countries. However, oils recovered from industrial frying processes could show satisfactory quality for this purpose. Here we studied the effects of including oils recovered from the frying industry in rabbit and chicken feeds (at 30 and 60 g/kg, respectively) on the fatty acid (FA) and tocol (tocopherol 1 tocotrienol) compositon of meat, liver and plasma, and on their oxidative stability. Three dietary treatments (replicated eight times) were compared: fresh non-used oil (LOX); oil discarded from the frying industry, having a high content of secondary oxidation compounds (HOX); and an intermediate level (MOX) obtained by mixing 50 : 50 of LOX and HOX. The FA composition of oil diets and tissues was assessed by GC, their tocol content by HPLC, the thiobarbituric acid value was used to assess tissue oxidation status, and the ferrous oxidation-xylenol orange method was used to assess the susceptibility of tissues to oxidation. Our results indicate that FA composition of rabbit and chicken meat, liver and plasma was scarcely altered by the addition of recovered frying oils to feed. Differences were encountered in the FA composition between species, which might be attributed mainly to differences in the FA digestion, absorption and metabolism between species, and to some physiological dietary factors (i.e. coprophagy in rabbits that involves fermentation with FA structure modification). The a-tocopherol (aT) content of tissues was reduced in response to the lower aT content in the recovered frying oil. Differences in the content of other tocols were encountered between chickens and rabbits, which might be attributable to the different tocol composition of their feeds, as well as to species differences in the digestion and metabolism of tocols. Tissue oxidation and susceptibility to oxidation were in general low and were not greatly affected by the degree of oxidation of the oil added to the feeds. The relative content of polyunsaturated fatty acids/aT in these types of samples would explain the differences observed between species in the susceptibility of each tissue to oxidation. According to our results, oils recovered from the frying industry could be useful for feed uses.Keywords: vegetable frying oils, tissue lipid composition, feed ingredients, oxidability, vitamin E ImplicationsVarious fat by-products of the food chain are included in feeds. Recycled cooking oils are not intended for feed uses in the European Union, although they might be used in other countries. However, oils recovered from industrial frying processes could show satisfactory quality for this purpose. Thus, here we studied how the addition of frying oils to feeds affects the lipid composition and the stability of meat and other animal tissues. Our results reveal an acceptable ...

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

“…Therefore, the lower ␣T content in rabbit meat samples might have promoted an earlier onset of oxidation than in chicken, leading to higher present TBA values in rabbit than chicken meat. These differences in meat oxidation between species were consistent with previous studies on animals fed with unsaturated vegetable oils (Tres et al, 2012b).…”

“…Tissue susceptibility to oxidation seemed more dependent on their PUFA/␣T ratios, in agreement with results from our previous trials (Tres et al, 2012b). For instance, compared to rabbit samples, chicken liver and plasma showed lower susceptibility to oxidation values as well as lower PUFA/␣T.…”

“…As it happened for the meat FA composition, differences between species in meat tocol content might have been masked by the inclusion of the skin on chicken meat samples. However, as previously found in other trials of this project (Tres et al, 2012b), the higher ␣T contents in chicken liver and plasma compared to rabbit revealed differences between species in their capacity to absorb, distribute and store ␣T. In tissues, ␣T acts as an antioxidant, thus lowering and retarding malondialdehyde formation.…”

“…In the first part of this project, more than 120 commercial fat products were characterised (Ábalos et al, 2008;Nuchi et al, 2009;Ubhayasekera and Dutta, 2009). Those containing the highest levels of dioxins, polycyclic aromatic hydrocarbons (PAH), trans FA (Tres et al, 2012a) and oxidation compounds (Tres et al, 2012b) were selected for testing in experimental animal trials. In agreement with what has been mentioned above, fish oils were the group of fats showing the highest dioxin content and oxidation status (Ábalos et al, 2008;Nuchi et al, 2009).…”

Livers of terrestrial production animals as a source of long‐chain polyunsaturated fatty acids for humans: An alternative to fish?

“…However, in mammals and birds EPA and DHA synthesis from ALA occurs mainly in liver, rather than in muscle tissue . Indeed, levels of the LC‐PUFA in liver are significantly higher than those in muscle of pigs , cattle , and chickens . Since liver also is an edible part of the production animals, it is worth to estimate its putative contribution to the LC‐PUFA supply in human nutrition, alternative to fish.…”