They didn’t get the result they were hoping for, but a trio of Agriculture and Agri-Food Canada scientists have discovered feeding flax to cattle makes for healthier beef.
The AAFC scientists recently completed a comprehensive project investigating whether long-term flax supplementation in cattle diets could increase the level of omega-3 fatty acids in the beef to the level required for a Health Canada “source of omega-3 polyunsaturated fatty acids” label.
Flax is known for its high content of omega-3 fatty acids, such as alpha-linolenic acid, which has been shown to reduce the risk of cardiovascular disease in humans. To qualify for the “source of omega-3 polyunsaturated fatty acids” label, Health Canada requires at least 300 milligrams of omega-3 fatty acids per 100-gram serving.
“Our hope was that enough of the alpha-linolenic fatty acid provided by the flax would escape biohydrogenation in the rumen and be stored in the tissue to result in omega-3 beef,” said Hushton Block, who conducted the feedlot portion of the trial at AAFC’s Brandon Research Centre.
“Biohydrogenation occurs when microbes in the rumen try to saturate the alpha-linolenic fatty acid with hydrogen molecules before the fatty acids are available for uptake by the animal. What appears to have happened is that much of the omega-3 provided by the flax underwent partial biohydrogenation, resulting in markedly higher levels of two isomers — vaccenic and rumenic acids.”
And that’s good news because the latter has known health properties and the former may have some, too.
The level of rumenic acid was three to four times higher and the level of vaccenic acid was seven to nine times higher in the beef from the flax-fed heifers compared to beef from the control group that received a conventional feedlot ration.
The chemistry of all three substances gets a bit involved, but here’s how it works:
Rumenic acid is the most common form of naturally occurring conjugated linoleic acid (CLA), a polyunsaturated fat found primarily in ruminant meat and dairy products. The rumenic acid version of CLA is recognized for its anticancer properties.
All mammals can convert vaccenic acid to rumenic acid within their own tissues. The health benefits of vaccenic acid are just beginning to be explored. Indications are that it may reduce triglycerides, LDL cholesterol, and total cholesterol in the bloodstream.
Trigylcerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and a lesser-understood variation of LDL known as Lp(a), make up your total cholesterol count. HDL is the good cholesterol known to protect against heart attacks. High levels of LDL, triglycerides and Lp(a) are associated with an increased risk of heart attack and stroke.
And while some of the omega-3 acids fed to the cattle wound up as rumenic and vaccenic acids, a significant chunk remained — the study found twice as much alpha-linolenic acid in the meat of cattle fed flax compared to the control group.
In regular ground beef from the cattle fed flax, the omega-3 level was 380 mg per 100 grams, easily meeting Health Canada’s labelling requirement. That’s similar to the level that can be achieved by mixing the fat with the lean beef from grass-fattened cows to produce an omega-3 ground beef product.
“It wasn’t quite high enough to meet the requirement for top-grade lean cuts, such as steaks and roasts from young cattle,” said Block.
“We would need something more than just long-term flax feeding — something that protects fatty acids in the rumen — to develop a feeding program that would result in consistently high levels of omega-3 in the beef.”
However, there may be potential to create a niche market for flax-fed beef based on the remarkable elevation in the proportion of vaccenic acid, he said. Not only was the vaccenic acid level as much as nine times higher in beef from the flax-supplemented animals, it was a truly remarkable 12 to 18 times higher than the typical level in beef from animals finished on traditional high-grain diets.
Earlier studies, which also failed to achieve omega-3 levels needed to meet Health Canada’s labelling requirements, supplemented flax at the maximum recommended inclusion rates for fat, usually for 60 to 100 days in conventional feedlot production systems.
Flax is a source of fat in beef cattle diets. Like starches, fats provide energy, however, high-fat diets (more than six to eight per cent added fat) are not well received by cattle and result in reduced feed efficiency, Block noted.
So instead of upping the flaxseed ration, Block lengthened the period it was included in the diet. The hope was more of the unsaturated fatty acids would remain available for uptake after biohydrogenation by the microbes in the rumen.
Block formulated a forage-based diet that was lower in energy than conventional feedlot diets to allow for a 250-day period of flax supplementation without causing the cattle to become excessively fat before slaughter.
The control diet was grass-legume hay with ground barley supplemented at approximately 30 per cent of the dry-matter intake to provide the same energy intake as the two flax supplementation treatments. Both diets containing flax had the same grass-legume base as the control diet. One included a half-and-half blend of ground flaxseed and barley grain supplemented at a level that provided six per cent added fat. The second diet used Lin- Pro, which is an extruded flaxseed and legume supplement manufactured by Oleet Processing Ltd. at Regina, and was also supplemented at a level that provided six per cent added fat.
At 1.1 to 1.2 kilograms per day, the growth of the heifers in the trial was slightly better than expected. With final weights of 500 to 600 kilograms, most heifers graded Canada AA. The performance results are typical of what would be expected for youthful finished beef, said Block.
The other big question was whether the flax supplement would affect the taste of the beef — but a taste-testing panel gave it a thumbs up.
University of Manitoba nutritional scientist Michel Aliani recruited students and staff from his department and put them through training sessions to familiarize them with the texture and flavour attributes of beef from various breeds of cattle, fed various diets, and aged and prepared by various methods.
The taste-testers then sampled the flax-fed beef and rated it on a wide range of criteria: aroma, initial tenderness, initial juiciness, overall tenderness, overall juiciness, connective tissue, beef flavour, off-flavour, and overall flavour quality. A shear force test was used to measure tenderness.
The majority of the panellists ranked most of the samples as having no off-flavour. If an off-flavour was detected, it was most frequently rated as trace.
There was some indication that beef juiciness could be reduced with long-term flax supplementation. The report advises that beef preparation, packaging, presentation and consumer information will have to be considered in promoting flax-fed beef if the long-term flax-feeding strategy leads to unique marketable products.
The other scientists involved in the study were Scott Duguid (flax breeder at AAFC’s Morden Research Station in Manitoba) and Mike Dugan at AAFC’s Lacombe Research Centre in Alberta, who analyzed the fatty acid profiles of the meat. The full report is expected to be available this winter.