Author
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Neel, James |
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Submitted to: Grazinglands Research Laboratory Miscellaneous Publication
Publication Type: Proceedings Publication Acceptance Date: 3/21/2018 Publication Date: 3/5/2019 Citation: Neel, J.P. 2019. Factors which impact the fatty acid profile of ruminant meat. NEPC 2017 Conference. Hargerstown, Maryland. March 2-3, 2017. Available: http://grazingguide.net/news/NEPC2017.html. Interpretive Summary: Research pertaining to factors impacting fatty acid (FA) profiles of meat products when ruminant diets are made up of entirely pasture/forage is minimal. Of the FAs found in ruminant fat, major emphasis is usually given to cis-9, trans-11 conjugated linoleic acid (CLA, also known as rumenic acid), linoleic (LA, an omega-6), alpha-linolenic (ALA, an omega-3), and the polyunsaturated FA (PUFA) omega-6 to omega-3 ratio. This emphasis is due to the potential healthful benefits these FAs have when consumed in human diets. The human health benefits of CLA has long been noted by dieticians. However, the dietary value of trans-11 vaccenic acid (TVA) is often overlooked. During the rumen fermentation process, TVA is produced and then converted to CLA by the ruminant. When ruminant fat is consumed by humans, CLA may have immediate health benefits, but the TVA present in the fat can also provide health benefits after being converted to CLA by the human. This conversion occurs at the rate of approximately 20% TVA to CLA. Linoleic and alpha-linolenic fatty acids are considered essential to humans. Our bodies can’t produce them on their own, but they are required for proper physiological function and human health. The essentiality of these FAs gives rise to the importance of the recommended omega-6 to omega-3 dietary ratio with regard to human health. For proper absorption rates of both essential FAs, it is generally accepted that the omega-6 to omega-3 ratio should be around 4:1 or less in our diet. However, the typical human diet within the United States contains an omega-6 to omega-3 ratio of around 10:1. An imbalance of either FA category (n-6 or n-3) results in over absorption of one or the other. Available research indicates that content of TVA in the fat of pasture finished animals can range from 2-10X that of concentrate finished. The value of TVA in ruminant fat is often overlooked, given the fact that humans can produce CLA from TVA at the approximate rate of 1 part CLA from 5 parts of TVA. When feeding starch-based energy supplements and silage prior to forage finishing, both CLA and TVA increased with increasing days of grazing straight pasture. When cattle were fed forage or forage + soyhull diets prior to pasture finishing, TVA content increased, while CLA remained generally steady with increased grazing time. During pasture finishing, the PUFA n-6 to n-3 ratio generally decreases with increasing grazing time when concentrate supplementation and silage is fed prior to pasture finishing. The ratio remains relatively steady if animals are stockered on forage diets prior to pasture finishing. Different forage species utilized during pasture finishing had no impact on TVA, CLA, LA concentration or PUFA n-6:n-3. There was a legume effect with regard to ALA, in that legume finished cattle had greater ALA than those finished on grass based pasture. The implications of the reviewed research are: 1) starch based concentrate supplementation followed by pasture finishing impacts meat fatty acid profile, even when animals grazed pasture alone for 118 days post supplementation; 2) producers of pasture finished beef can utilize forages best suited for their farm and management, while still producing a product containing a typical pasture finished FA profile; and 3) meat trans-11 vaccenic acid content should be included in discussions concerning the healthy properties of beef. Technical Abstract: Research pertaining to factors impacting fatty acid (FA) profiles of meat products when ruminant diets are made up of entirely pasture/forage is minimal. Information that is available indicates that both management and forage species consumed can have an effect on product FA profile. Of the FAs found in ruminant fat, major emphasis is usually given to cis-9, trans-11 conjugated linoleic acid (CLA, also known as rumenic acid), linoleic (LA, an omega-6 FA), alpha-linolenic (ALA, an omega-3 FA), and the polyunsaturated FAs (PUFAs) omega-6 to omega-3 ratio. However, the dietary value of trans-11 vaccenic acid (TVA) is often overlooked. During the rumen fermentation process, TVA is produced and then converted to CLA by the ruminant. When ruminant fat is consumed by humans, CLA may have immediate health benefits, but the TVA present in the fat can also provide health benefits after being converted to CLA after human ingestion. It is generally accepted that the omega-6 to omega-3 ratio should be around 4:1 or less in our diet. During forage finishing of livestock, research shows time on pasture impacts the FA profiles of meat. After feeding starch based energy supplements prior to finishing on pasture (Noci et al., 2005), TVA and CLA increased linearly with increasing days on pasture. Without starch based supplements during forage stockering (Fincham et al., 2009; Duckett et al., 2014), CLA content stayed constant over time in fatty tissue while TVA increased with increased days on pasture. Available research also indicates there is no effect due to forage type during pasture finishing regarding meat TVA, CLA, LA contents or PUFA n-6:n-3 (Duckett et al., 2013; Chail et al. 2016). The implications of the reviewed research are:1) starch based concentrate supplementation followed by pasture finishing impacts meat fatty acid profile, even when animals grazed pasture alone for 118 days post supplementation; 2) producers of pasture finished beef can utilize forages best suited for their farm and management, while still producing a product containing a typical pasture finished FA profile; and 3) meat trans-11 vaccenic acid content should be included in discussions concerning the healthy properties of beef. |
