n-3 PUFA Sources (Precursor/Products): A Review of Current Knowledge on Rabbit

Abstract

Simple SummaryThe nutritional quality of fat for human consumption is usually evaluated in terms of the n-6/n-3 polyunsaturated fatty acid (PUFA) ratio (with optimal values ≤4). Moreover, with respect to animal production, the standard feed is unbalanced in terms of n-6/n-3 polyunsaturated fatty acids (PUFAs) with a lower proportion of the latter. Such discrepancy negatively affects the health status of animals, the productive and reproductive performances, and the general quality of their products. Hence, n-3 PUFA intake should be promoted. The increase in n-3 PUFA proportions in animal products would also be in accordance with the human dietary recommendations that often focus on the need of increasing the intake of long-chain n-3 PUFAs. In this regard, two main strategies could be implemented, namely to furnish precursor (α-linolenic acid) or long-chain derivatives (eicosapentaenoic and docosahexaenoic acids). In the present review, the effects of different n-3 PUFA sources on biological activity, physiological/reproductive endpoints, and health implications are compared focusing on the most recent results obtained in the rabbit.AbstractThis review compares the effects of different n-3 polyunsaturated fatty acid (PUFA) sources on biological activity, physiological/reproductive endpoints, and health implications with a special emphasis on a rabbit case study. Linoleic acid (LA) and α-linolenic acid (ALA) are members of two classes of PUFAs, namely the n-6 and n-3 series, which are required for normal human health. Both are considered precursors of a cascade of molecules (eicosanoids), which take part in many biological processes (inflammation, vasoconstriction/vasodilation, thromboregulation, etc.). However, their biological functions are opposite and are mainly related to the form (precursor or long-chain products) in which they were administered and to the enzyme–substrate preference. ALA is widely present in common vegetable oils and foods, marine algae, and natural herbs, whereas its long-chain PUFA derivatives are available mainly in fish and animal product origins. Recent studies have shown that the accumulation of n-3 PUFAs seems mostly to be tissue-dependent and acts in a tissue-selective manner. Furthermore, dietary n-3 PUFAs widely affect the lipid oxidation susceptibility of all tissues. In conclusion, sustainable sources of n-3 PUFAs are limited and exert a different effect about (1) the form in which they are administered, precursor or derivatives; (2) their antioxidant protections; and (3) the purpose to be achieved (health improvement, physiological and reproductive traits, metabolic pathways, etc.).

Effects of Diets Enriched in Linseed and Fish Oil on the Expression Pattern of Toll-Like Receptors 4 and Proinflammatory Cytokines on Gonadal Axis and Reproductive Organs in Rabbit Buck

“…Experimental Design. Rabbits were randomly assigned to one of three groups (5 animals/group): C group was fed with commercial standard diet (lacking linseed or fish oil), L group with diet rich in extruded linseed (10%), and FO group with diet rich in fish oil (3.5% NORDIC NATURALS omega-3®) [14,33]. Vitamin E (200 mg/kg feed, synthetic alpha-tocopheryl acetate) was included in all diets.…”

“…However, in the present study, no lineal relationship exists between n-3 PUFA ingestion and their profile in the sperm: it seems that n-3 PUFAs from fish oil were more effective with respect to those provided by the linseed. This is justifiable by the fatty acid composition of rabbit sperm: membrane phospholipids were constituted by 43% of LC-PUFAs, and then they incorporate more easily EPA, DHA, and especially the docosapentaenoic acids from n-6 series (22:5n-6) with respect to their precursors LA and ALA (n-6 and n-3, respectively) [14].…”

“…On the other hand, some nutrients such as PUFAs, minerals, and vitamins seem to improve the reproductive functions through several potential mechanisms of action [6][7][8][9]. For example, it is now known that the diets rich in long-chain PUFAs (≥20 C, LC-PUFAs) improve semen quality by modifying the fatty acid profile of plasma, seminal fluid, and sperm [3,[10][11][12][13][14].…”

“…Among the strategies to prevent and manage the infections of the genital tract, the use of some natural components in the diet, called functional foods or nutraceuticals, provides an attractive alternative to pharmacologic interventions. Indeed, experimental and epidemiological studies have shown the LC-PUFAs, in addition to their direct effects on sperm fatty acid profiles, have also anti-inflammatory properties [14,36,37]. In most of these studies, fish oil was used as source of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) [6,14,36,37].…”

“…Nevertheless, LC-PUFAs can be also obtained indirectly from other sources like the linseed. In fact, linseed contains α-linolenic acid (ALA, 18:3n-3) which can be endogenously converted into EPA and DHA [14,33,36]. Mechanisms underlying the anti-inflammatory actions of PUFAs not only include the inhibition of the production of eicosanoids, like prostaglandins and leukotrienes, but also of proinflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-8 [37][38][39][40].…”