Grassfed Beef Expectations for Fattening and Genetics

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July 18, 2020

By: Anibal Pordomingo 

SANTA ROSA, Argentina:Fattening cattle without grain is an artisan and difficult task. But some principles seem to hold in common. 

Fattening or finishing on pasture at a young animal age does not allow for the luxury of low gains and long periods. Marbling expectations shorten that luxury even more. A year-old animal can take forage restriction during backgrounding, speculating with compensatory growth later. But, the length of a restriction depends on the fattening ability later. Animals that reach “ready benchmark” of finishing should be harvested. 

Many of us prefer grassfed beef on the assumption that we buy a lean and healthy product, with the expectation of eating quality protein with low fat. As an oxymoron we expend most of our planning of a production program on the fattening component. That amount and type of fat is harmless to human health, furthermore, it can be beneficial. 

Markets, chefs and finally consumers dictate what pasture-finished beef is. Interpreting the signals from the market is not easy and many times signals have different weight. Previous experiences, expectations, culture, education introduce biases far more important than objectivity of scientific facts. Meats become what they are supposed to be, or we want them to be, even if objectively they are not.  We do not mind lean and dark deer meat, but not so much for beef. 

Pasture-finished beef is leaner and difficult to cook, compared with grain-fed for tenderness.  Although people may know about differences in cuts and benefits of grassfed beef, toughness is never appreciated. And, people are more inclined to acquire grassfed beef for their own cooking after a good experience at a restaurant. 

We have learned that not just steaks, but a good, flavorful hamburger can have the same effect.  Hamburger meat should not be underestimated in quality. A significant fraction of the carcass goes to hamburger, so it needs to be good.  This reflects more on the cooking than on the meat itself. Adding fat to hamburger meat to adjust flavor is difficult with an extra lean carcass. 

All cuts with some intramuscular and a layer of outside fat are easier to grill/cook than lean beef.  Lean beef is more sensitive to handling, aging and cooking methods. It dries fast and can burn. Chefs point out that marbling and outside fat prevents fast drying and meat burning. 

Young animals tend to havewhite cover fat and it is often preferred, but excessive thickness is rejected. Experienced grassfed beef buyers do not segregate against a slight yellow tint on the fat (proof of grassfed) but brightness is central. Brightness or shininess of the cut surface indicates freshness, good meat pH, adequate muscle glycogen content or muscle sugar, and likelihood of quality. 

For more than 20 years, we have worked on developing forage and management plans to produce quality grassfed beef. Most producers and buyers agree that beef has to be tender, juicy, appealing in color and texture, with fat but not fatty, and consistent in quality. 

On the production side, most systems target for harvesting at two and a half years old or younger age. The likelihood of consistent tenderness decreases with age. Having such a time frame restriction, the challenge is on the pasture and the genetics. 

Breed is the first concern, and most producers accept that genetics for grass finishing should favor British breeds, early maturing, low frame, (3 to 4) and easy marbling. For the typical British breeds, thick body and deep chest and belly are important. Eye of the rump should drop low and visible before 12 months of age. One-year-old males and females should be very moderate in size, below the average for the breed, but thicker (wider), and the shoulders as wide as their rump length. We want to avoid long legs and large bones. 

The likelihood of consistent tenderness decreases with age. 

Some genetics are naturally more tender that others. Breeds that evolved in temperate environments tend to be more tender. Dairy breeds, or those with some milking ability, are more tender although lower yielding. Muscling and adaptation to harsh environments, to work, such as draft breeds, or stress, favors excessive connective tissue and the likelihood of meat toughness. 

Now, breeding operations have developed genetics on adaptation and feed efficiency. The feed efficiency has increased in the USA herd. Steers are significantly more efficient in the yard now than in the past. Depending on the baseline year to compare against, we can demonstrate that feed efficiency has improved 40% or more.  Genetic improvement is the largest contributor to such improvement. 

However, is feed efficiency the adequate trait to select cattle for grassfed programs? One of the drawbacks of selecting for feed efficiency is the high correlation of feed efficiency on animal size and late maturing. High feed efficiency may also relate to delayed marbling or no marbling at all on pasture. 

A selection index that can help select animals for efficiency without the risk of increasing body size and leanness could be “residual feed intake.” Residual feed intake (RFI) refers to the difference between the actual and the expected intake for a given daily weight gain. It describes a trait of efficiency without maximizing, or independent of gain, or feed to gain. Therefore, it does not depend on weight and animal size. 

Light and small animals, early maturing and easy fleshing, can be negative RFI (more efficient).  Such efficiency relates more to efficiency of energy use for maintenance, lower protein turnover, lower energy use in temperature homeostasis - more efficient mitochondria, and likely more efficient immune system. Negative RFI animals do not necessarily marble more but will not postpone marbling and fattening. 

But, beyond conventional approaches for selection, grassfed genetics - a minor fraction and divergent of the world beef genetics - need to evolve beyond phenotype and population performance.  It will not gain the  homogeneity needed for tenderness if it does not approach selection differently. 

It might be the time for incorporating new tools for objective selection of animals within a breed and biotype. Being such a defined niche with one priority (tenderness), the grassfed industry could use genomics to detect quality performing genetics. 

Gene mapping and gene marker-oriented selection were impossible in the past. Today, linking responses and performance to gene pools and maps is commercially feasible. The grassfed industry should move towards mapping the pools of genes that control traits such as muscle collagen, soluble collagen, easy marbling, bone density  and temperament. 

■  Dr. Anibal Pordomingo is both a grassfed researcher, renown world-wide educator and private grass finisher in the Argentine Pampas. He has spent a lifetime perfecting production systems under harsh climatic conditions that allow healthful grassfed beef to compete quality-wise with grain-fed beef.

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