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Simple Summary: The 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. This 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.). [ABSTRACT FROM AUTHOR]