Brix: The Panacea to Grass-Based Finishing?

By Amy Barkley, Livestock Specialist, CCE SWNYDLFC Team

I was sitting at the kitchen table with one of our region's farmers a few months ago, and we were discussing how to get a better and earlier finish on his grass-fed cattle. Typically, with grass-based finishing systems, producers have to wait until cattle are around 30-36 months old to process in order to achieve the weights and marbling preferred by many clients. This puts the producer in a pickle. First, grass fed animals need to be maintained for about twice that of a traditionally finished animal. That means the producer needs to charge substantially more for their product to make up the difference of feed, housing, and care. Second, the turnaround time for grass-fed animals is much longer, meaning that customers may have a longer wait for their beef, especially if a herd is small and the customer base is large. Third, if the animal is 30 months or older when processed, the butcher is required by law to remove the spinal column, meaning no bone-in steaks. Fourth, as the animal ages, it takes on a flavor and texture that can be more robust than that of beef many grain-finished customers are used to. For all of these reasons, it makes all of the sense in the world that we would want to decrease the finishing time of grass-fed beef. But, how do we do that?

Most grass-fed systems require that the animal be fed forages for the vast majority of its life, including through finishing. There are two main nutrients in forage that we need to concern ourselves with: Protein (CP) and Energy (TDN). In it's simplest terms, protein puts on muscle, energy puts on fat. As the animal goes from calf to finished animal, it's protein needs start high, and decrease over time. The opposite is true for energy. As the animal puts down more fat in the finishing phase, its energy needs increase. In cool season perennial pastures, we normally get enough protein, but the TDN is lacking for quick finishing.

Cool season forages grown in the Northeast are generally sufficient for weight gains of about 1-1.5 pounds a day on finishing animals. This unfortunately pales in comparison to gains from high energy, grain-based rations, which can get you in the 3.5-4 pound range for daily gains. Why is it that forages lag so much when it comes to putting on the pounds? While protein levels in pasture and most stored forages is sufficient for muscle accretion, they just don't have the energy needed for finishing. For instance, a finishing steer that you want to gain 3 pounds a day requires a TDN of 70% on a dry matter basis. If you are feeding that animal a diet with 50% TDN, expect gains of less than a pound a day. If you target 60%, that'll put you closer to 1.5 - 2 pounds a day. Keep in mind that this is in ideal circumstances. If temperatures are outside those that are optimal for cattle, expect those gains to be less. In the harshest winter months, I've seen negative or near 0 gains for cattle in the finishing stages.

So, now the big question: how do we improve rates of gain for these critters? There has been much conversation around the Brix contents of the forages in the grazing community, which deserves some looking into. Brix is a term used to quantify the amount of dissolved sugars in a liquid sample (in this case, pasture plant juice). It's measured using an instrument called a refractometer, and can be used to compare the sugar content of forages. However, it's not very accurate for pasture forages, in part because it was developed to measure the sugar contents of fruit and honey. Pasture plants have about 1/4 - 1/3 of the free sugar concentrations of wine grapes, for instance.

In addition, Mississippi State and the US Department of Agriculture's Agriculture Research Service (USDA-ARS) share that Brix is highly variable in cool season pasture due to influences including time of day, ambient temperature, barometric pressure, soil moisture, drought conditions, fertilization, species, maturity, and human sampling error. Furthermore, there is little research evidence to support how brix directly influences rates of gain in beef cattle. Based on the research I've read, it appears that until we understand more, the best way to add pounds to your cattle is not to focus on Brix measurements, but instead to focus on forage quality and TDN. So, as forage stand managers, we have to use tools that we already have in the toolbox to manage for the best cool season stand possible:

1. Manage pastures so that they don't over mature. Younger plants have less indigestible structural carbohydrates like lignin that are used to extend the plant stem in preparation for pollination/seeding. Younger plants tend to have less indigestible fiber, so they'll have a higher rate of passage, meaning that your animals will eat more forage per day and potentially get more out of it. Furthermore, the consumption of more readily available carbohydrates in the forage results in an increase in rumen microbes, which will increase organic acid production that is then used as energy by the cow.
2. Avoid grazing below 4" of residual. The lower you graze plants, the more they will naturally prune their roots, reducing the rate of regrowth and therefore making the stand take longer to replenish its free sugar content.
3. Nitrogen application will reduce the free sugar content in forages because the plant will be using its free sugars to grow. Nitrogen is good  to increase tons/acre and increase protein content in forages.
4. Plant species that are known to have a high energy contents. You can work with your local seed dealer to identify species/varieties that have characteristics like a higher leaf to stem ratio, the ability to produce more digestible sugars, or mature later to give you a longer grazing window.

If you're open to planting summer annuals, species including sudangrass, forage sorghums, and legumes tend to have higher brix and TDN levels than perennial forages in part because of their tendencies toward more lush, vegetative growth. Annuals work for farms that have the open land and time to commit to harvesting forages at the ideal maturity stage for the best nutrition. Over mature summer annuals decrease in quality quickly once they move into their reproductive phases.

Through this article, I hope to have provided you with some ideas to increase the bang for your buck of your forage stands. We are continuing to look out for research on Brix and strategies to decrease the timeline for grass-fed finishing, so stay tuned!

References:

Balsom, T. and Lynch, G. 2008. Monitoring pasture quality using brix measurements. Novel Ways, Hamilton.

Billman, E., et al. 2023.  Brix as an indicator of sugar content and nutritive value in alfalfa and orchardgrass herbage. https://www.ars.usda.gov/research/publications/publication/?seqNo115=399930a...

Donaghy, D. J. and Fulkerson, W. J. 1997. The importance of water-soluble carbohydrate reserves on regrowth and root growth of Lolium perenne (L.). Grass and Forage Science. Volume 52, 401-407.

Lemus, R. 2014. Brix Level in Your Forage: What does it mean? Mississippi State University Extension Service Forage News. Vol 7, iss 2. Forage News - February 2014 (msstate.edu)

Smith, K.F., Reed, K. M. F., and Foot, J. Z. 1997. An assessment of the relative importance of specific traits for the genetic improvement of nutritive value in dairy pasture. Grass and Forage Science. Volume 52, 167-165.