Manage hormone implants for marbling
April 5, 2018
Animal scientists know hormone implants affect marbling distribution in the muscles of cattle. For higher quality grades, nutritionists may advise delayed or no implants, but adding value later must be weighed against the near-term payoff of $25 or more per head.
As new implants become available for use earlier and earlier in the calf's life, forgoing that technology may seem like an economic sacrifice, even for those who will retain ownership and market finished cattle on a packer grid.
Should producers have to choose between high growth and premium quality grade? What are the best options?
Brad Johnson, meat scientist and muscle biologist at Texas Tech University, said the latest generation of implants first introduced in 2007 can help cattlemen capture more growth on the front end without sacrificing quality grade later, if managed properly.
The key to having your cake and eating it, too, is the right combination of nutrition, hormone dose and implant timing, especially if the plan calls for re-implanting.
Johnson's team published two research papers that showed trenbolone acetate (TBA), a powerful anabolic steroid used in implants, is more detrimental to marbling than estrogen-based alternatives. TBA significantly reduced the expression of key transcription factors that send signals to tissues to grow as marbling cells. That's why he recommends using a low-dose estrogen option for grazing calves.
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Especially for young, lightweight calves, an overabundance of TBA can saturate hormone receptors.
"They can't respond to that much steroid early on and producers will see a dramatic reduction in marbling," Johnson said.
It's about selecting the right type of implant for the stage of the calf's life and managing the diet to help supplement growth without sacrificing the "taste fat."
"When you give a rapidly growing animal, like a really young, lean steer or heifer that has a lot of growth potential, a high dose, high-growth implant, they're going to respond as much as they can," Johnson said. "The more they respond, the more calories are necessary to support that muscle growth. So naturally, we have less calories to start depositing fat into these muscle intramuscular cells."
The rate of release of TBA might also impact marbling score, he said. In some combination implants, there's a rapid release of both TBA and estrogen initially but some newer implants have a special polymer coating allowing a slow release of the hormones over time, some as long as six months. Johnson said this method is more effective for quality production over a dramatic release of hormone each time a calf is implanted.
"I think the longer term and slower we can deliver these steroids, we'll get the positive impact on growth," Johnson said. "But yet we'll have less detrimental effect and in many cases marbling scores are similar to non-implanted cattle when we use some of these coated implants."
They could represent an opportunity to add value without sacrificing a premium eating experience.
Implant type and timing is vital, but more important to capturing growth and grade is nutrition.
Justin Sexten, ruminant nutritionist and director of supply development for Certified Angus Beef LLC, said some early implanting can be balanced with adequate nourishment.
"Calves need the proper nutrition to support the additional growth from the implant," Sexten said. "When they are just eating grass and milk, their nutrition is quickly used for lean muscle production. However, if we creep feed and balance with high-quality pasture, there's enough nutrition left over to build both muscle and fat stores."
With the right nutrition program, calves can reach that optimal level.
Still, calories pushed toward lean tissue growth early in the calf's life leave fewer marbling cells and less opportunity for lipid filling when calves reach the feedlot stage and there are extra calories available.
"If producers are feeding for a high-quality market, they've got to be very aware that they don't get too aggressive up front with their implants," Johnson said.
In the feedlot phase, higher dose implants have less impact on marbling because the cattle already have their marbling cells developed for filling with fat, he said.
According to a 2011 National Animal Health Monitoring System report, 96 percent of all cattle that enter the feedlot phase receive an implant. As use of this technology increases prior to that phase, with a negative effect on marbling each time, cattle with greater than average marbling potential may reach a point of diminishing returns, Johnson and Sexten said.
In that case, adding pounds of lean beef early may not pay out for the next person in the production chain. Now that two-thirds of fed cattle meet the predominantly black-hide criteria, the No. 1 reason they don't make it into the Certified Angus Beef brand is simply too little marbling. That's why efforts to add early pounds to Angus-influenced cattle should take care not to restrict early development of marbling cells.
"I think just understanding the biology of how these implants affect marbling, you can adjust things up front, yet still use a high-dose implant at the end to maximize quality carcass gain," Johnson said.