John Gonzalez – Grow Promoters and Beef Tenderness

(John) My name is John Michael Gonzalez, I’m an Assistant Professor in the Department of Animal Sciences and Industries. I am a Muscle Biologist, and today at Cattleman’s Day, I will be speaking about the effects of growth promotants on meat tenderness. What we’ll present today is an NCBA study that we got funded in conjunction with the Beef Cattle Research Center here at K-State and also North Dakota State University where we studied two different growth promoting programs. The first program is an implant program where we implanted an aggressive implant during 75 days before harvest and then our second treatment group would have been some heifers that were supplemented with the implant and also the beta-adrenergic antagonist zilmax , or zilpaterol hydrochloride. And our overall goal there was to actually look at the biology of the muscle and take measurements to quantify what effect the growth promotants were having on the biology of the muscle and its influence on tenderness. What we ended up finding was that when you supplemented the implant and compared it to an animal that was not supplemented with a growth promoting technology they had steaks at day three of aging that were 20 percent more tougher than a control animal. When we supplemented the zilmax on top of the implant it increased the difference in sheer force to 40 percent when you compared it to control animal. Now, what we did next is actually aged out these steaks, or steaks from these animals to 35 days of post mortem aging, and what we ended up finding was around day 14, the implanted animals stage sheer force values became the same as the controls. Unfortunately the zilmax and the implant combination animals had tougher steaks at day 14, and day 21 and day 35. Thus indicating that extended aging does not alleviate the negative tenderness effects of both those growth promoting technologies. Next thing that we did was that we actually looked at the muscle structure and what we looked at was myofibrillar proteins are the cross sectional area of muscle fibers, which are the cellular unit of muscle. When you looked at that, the implants and the combination group of zilpaterol and implants increased cross sectional area of our three fiber types by anywhere depending on what treatment you’re looking at. But in general it was around 20 to 28 percent increase in fiber types there. Next what we looked at and what I’m especially interested in in my research program is the collagen component. Collagen is not heavily studied in meat science and muscle biology. It’s usually seen as a protein that there’s not much we can do to influence after the animal is harvested. And so we ended up looking at was the amount of soluble collagen, which is good collagen that is solubilizes during cooking and is easy to bite through. And we looked at the amount of insolubilized collagen, which I would say is bad collagen and that provides resistance when you try to bite through your meat item. And then we combine those two measures to get an overall total collagen content. In our study we found that both growth promoting technologies did not influence the amount of collagen. Collagen solubility or insolubility, are overall collagen amount. So, that would lead us to believe that those growth promoting technologies do not influence that part of our meat tenderness system. Currently what we have going on in the university because… or in my laboratory which we’re interested in and where we’re going as a lab group, is looking at collagen cross linking and how to influence it in the live animal and also what happens post mortem because from this study we actually found that we can break collagen cross links as the meat is aged, similar to what is seen in the myofibrillar component. And so what we’re doing as a group is looking at breed effects and also I’m doing a little further analysis of growth promoting effects on collagen cross linking and its influence on tenderness.

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