**6. Concentration Range in Red Meats**

Approximately 80% of Australians are not meeting the recommended n-3 LCPUFA intake for optimum health [55]. The same is likely true for majority of the population in other Western countries such as United States of America and the United Kingdom. The general advice from dieticians and health professionals is to consume 2–3 fish meals weekly to elevate the n-3 LCPUFA levels in the body. Fish and other seafood are rich sources of n-3 LCPUFA. Nevertheless, the consumption of LCPUFA (i.e., EPA and DHA) from marine-based foods is low to very low in many Western countries, and alternative food sources for these FA may therefore be advantageous in these populations.

Unlike human and other monogastric animals, ruminants are mainly dependent on the microbial population in the rumen for the digestion and absorption of dietary lipids. This microbial activity is responsible for the hydrolysis of dietary lipids and further isomerisation and conversion of unsaturated FAs into MUFA and SFA intermediates. The latter process leads to an increase in stearic acid (C18:0) concentration for small intestine absorption. However, several studies have reported that PUFA content in red meat from ruminants can be significantly modified by feeding systems. Pasture- and silage-fed animal deliver meat with higher PUFA, particularly in terms of n-3 PUFA content, when compared with their grain-fed and concentrate feedlot fed counterparts [56–58]. Particular secondary metabolites found in pasture and forage diets may exert a greater protection against microbial biohydrogenation of PUFA in the rumen and, therefore, facilitate increased absorption and deposition of PUFA in ruminant tissues [59]. Previous research has also

shown considerable differences on animal growth performances, carcass characteristics and meat quality attributes in sheep and cattle fed forage-based diet versus concentrate diet and these areas have been discussed in detail by others [60].

Western populations consume more meat and processed meat products than marinebased foods due to preference, availability and affordability. As a consequence, red meat can contribute up to 20% of their n-3 LCPUFA requirements [61]. An earlier study in humans consuming lean red meat showed that 2 weeks consumption of 500 g lean meat per day was sufficient to raise plasma DPAn-3 levels [62]. This may therefore be considered an alternative or complementary source for those with poor fish consumption. The enrichment of n-3 PUFA levels in meat through dietary management has been a focus in the animal production systems for the past 20 years. This aims to improve n-3 PUFA consumption for those who consume lower amounts of meat [20,34,63,64]. For this reason, many studies have investigated feeding lipid sources such as marine-based oils, and grains and oilseeds in ruminant and monogastric animals. To our knowledge, the studies conducted with algae, fish oil, flaxseed and canola seed supplementation and, likewise, using specialised forage or grazing options have shown prominent outcomes in increasing the n-3 LCPUFA levels in ruminants [65–69]. This information provides insight into management practices that can optimise the nutritional value of the meat products. That said, ALA is the primary FA source from plant-based diets. A good understanding of the efficacy of the elongation process of ALA to EPA, DPA and DHA in ruminants is long overdue [17].

#### **7. Preservation until the Point of Consumption**

Management systems have been adopted that enrich animal tissues so that they become a source of n-3 PUFA and n-6 PUFA. These efforts are often implemented without first considering the interim between processing and consumption. This is important as longer carbon chain-length FA with double C-H bonds (e.g., EPA or DHA or AA) are more susceptible to oxidation than shorter or more hydrogenated FA, such as MUFA [70,71]. Manifestations of this effect are observed in Adeyemi et al. [72], with results showing that n-3 PUFA and n-6 PUFA concentrations in goat meat declined across 12 days of a chilled storage period at 4 ◦C; in Muino et al. [73], with findings that lamb PUFA decreased in a linear trend with increased chilled storage period when held in oxygen-rich modified atmospheric packaging; and in Diaz et al. [74], with conclusions that 6 days of chilled storage at 2 ◦C was sufficient to degrade the PUFA content of lamb meat. It is interesting, therefore, that Holman et al. [75] observed no change in beef PUFA composition across a 12 week chilled storage period—although the authors suggest this was an outcome of anaerobic storage, low initial levels of PUFA and a relatively high concentration of vitamin E within the samples.

Vitamin E (α-tocopherol) has been widely acknowledged as practical and intrinsic means to preserve the FA profile of meat. Indeed, for lamb meat, Ponnampalam et al. [76] proposed a tissue concentration of greater than 3.45 mg/kg vitamin E as sufficient to inhibit excessive peroxidation. A similar recommendation was made for beef, with Arnold et al. [77] concluding that concentrations of 3.3 mg/kg vitamin E were appropriate. The concentrations of tissue vitamin E have been reportedly improved with animal supplementation [78,79] and functions as a result of its inhibition of the production of reactive oxygen species and propagation of free radical reactions [80]. Alternatively, meat may be stored within anaerobic packaging conditions or with embedded antioxidants to inhibit peroxidation. Examples have been described in Holman et al. [81] with review of different patents for smart packaging devices and antioxidant coatings that can scavenge specific gases, including oxygen, from an in-pack atmosphere to preserve against oxidation, and can be implemented within packaging systems to assure anaerobic conditions. That said, temperature controls (cold-chain, frozen storage) and vacuum packaging alone may be enough to prevent excessive peroxidation if their consistency and efficacy can be confirmed across the interim. From these findings, it is recommended that the preservation of FA

composition beyond its immediate enhancement should be considered when seeking to enrich the composition of different food types.

#### **8. Conclusions**

We report here that animal and human foods in the modern era are composed of higher n-6 PUFA levels and n-6/n-3 ratio compared to foods consumed by humans and animals during early evolutionary periods. These variations are primarily the consequence of changes to agricultural practice, animal production systems and food processing during the last 100–200 years. Changes in ecosystems and climate variability also contribute to these variations. Taking Australian production systems as an example, it is perceived that the application of low-nutritive or low-quality roughage diets (haylage), crop residues, senesced hay materials in the ruminant production systems is vital for sustainable and resilient future animal industries, but this will further reduce the n-3 PUFA and vitamin consumption and as a consequence in red meat. Commercially based animal industries using proportionately high concentrate diets in their animal feeds may also be attributable to increased consumption of n-6 PUFA and reduced n-3 PUFA by livestock and, thus, elevated n-6/n-3 ratio in red meat. It is likely that animals grazing single stand pasture (monoculture) receive lower amounts of essential FA, vitamins and minerals than those grazing mixed pastures. This is due to limited selection of herbage materials that are rich in nutrient values. It is known that ruminants consuming feeds rich in lipids mainly n-3 PUFA (oils and fats—e.g., diets containing brassica family members such as canola, camelina, or flax) also emit lower amounts of methane to the ecosystem than those consuming diets with highly fibrous structural carbohydrates, such as diets high in cellulose. Forages high in secondary metabolites such as polyphenols (tannins, flavonoids and phenolic acids), alkaloids and carotenoids may protect n-3 PUFA against microbial fermentation and biohydrogenation in the rumen due to their low bioavailability, allowing PUFA to reach the intestine for the absorption by host animals. This observation notwithstanding, additional research is necessary in this area to better understand the biological pathways and mechanisms of actions.

A sustainable animal and plant production system is essential for economic viability and the health and welfare of animals and humans, reinforcing the consideration of n-3 PUFA and n-6 PUFA in animal feeding systems equivalent to range feeding. The literature clearly indicates that animal grazing diets high in essential FA and vitamins have better metabolic conditions and oxidative status than those consuming diets of low nutritive value, contributing to improved wellness and lower veterinary care. It is likely that ruminant animal feeding systems will, in the future, utilise more concentrate-based specialised diets, which consist of less n-3 PUFA, to tackle the extended dry seasons and shortage in green pasture with climate variation. This scenario requires that the producers and researchers identify forage diets and supplements high in n-3 PUFA, vitamins and phytonutrients whilst low in n-6 PUFA and structural carbohydrates (cellulose, lignin) so that the health and wellbeing of animals and humans can be advantaged. The capacity to maintain the essential PUFA, vitamins and trace elements in meat from farm to fork and throughout processing and preservation must also be considered. Taken together, we state that offering n-3 PUFA rich diets to animals has many advantages economically, environmentally and socially, not only for animals but also for those humans who consume red meat in moderate to high quantities.

**Author Contributions:** Conceptualisation, E.N.P.; writing—original draft preparation, E.N.P., A.J.S. and B.W.B.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors are grateful to the support of their corresponding organisations, specifically Agriculture Victoria and NSW Department of Primary Industries. The first author (Eric N Ponnampalam) wishes to acknowledge Andrew J Sinclair's contribution as an adviser and mentor in his early scientific research career development (year 1994–2000) in the area covering the nutritional management of omega-3 fatty acids in ruminants for better production aspects and animal health and wellbeing. Sinclair is internationally recognised and published his research in *Nature* four decades ago (Rivers, Sinclair and Crawford [16]) reporting on the importance of omega-3 fatty acids for a healthy life.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

