There are certain groups of fed cattle that receive beta-agonists that have serious welfare problems at the packing plant. This problem became obvious to the industry when Lilly Edwards-Calloway from JBS showed a video of lame, stiff-gaited cattle at the National Cattlemen’s Beef Association (NCBA) summer meeting in early August.

Edwards-Calloway also stated that at least 20% of the cattle received at two JBS plants during hot summer weather were more difficult to drive out of the holding pens. She used words such as “tender-footed, lethargic, stiff, and no energy.”

 On the same day as the NCBA meeting, Tyson announced it would stop buying cattle fed the beta-agonist Zilmax™ because some animals at its packing plant were “unable to move and had difficulty walking.” Other major packers later announced they would no longer accept cattle fed Zilmax as well.

In my opinion, the cattle shown on the JBS video were suffering. Since the introduction of beta-agonists, I have made many similar observations. Many people called them anecdotal, but I have observed stiff gait and sore-footed walking in all four major types of fed cattle –Holsteins, Angus, Brahman crosses and mixed beef breeds with no Brahman influence.

Cattle okay at the feedlot but problems evident at the plant

Since the NCBA meeting, I’ve had discussions with people who work at both feedlots and packing plants. An obvious pattern has started to emerge.

First of all, some groups of cattle on beta-agonists are fine, while others have problems. A common problem is that while cattle may be fully mobile at the feedlot, they get progressively worse as they advance through the various handling and transport steps from the feedlot to the plant.


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Cattle may arrive at the plant with a stiff gait and, after having rested in the plant holding pens, become more reluctant to move. They act like they have both stiff muscles and sore feet.

A possible explanation for the worsening of the problem as cattle move through the handling and transport steps could be muscle fatigue. Zilpateral enhances the growth of “fast-twitch” fibers, a type of muscle fiber that fatigues more easily. A paper in the Journal of Animal Science (Baxa et al. (2009) 88:330-337) states that zilpateral feeding is associated with a transition away from slower fibers (slow twitch) to faster fiber types (fast twitch).

Both discussions and my observations indicate that when a problem occurs with beta-agonists, it is most likely to be associated with:

Hot weather.

• Zilpaterol – there are more problem cattle compared to ractopomine.

• Big cattle or heavy-muscled cattle.

• Uneven effects within the same lot of cattle. Half the cattle may be normal, and 5-10% severely affected. This may be due to uneven feed intake. Chris Reinhardt from Kansas State University presented data at the NCBA meeting that showed that 75% of cattle reduced feed intake on Zilmax, and 25% maintain the same feed intake. Another possible cause of problems may be poor feed mixing and some animals getting an overdose.

• Death loss during the late stage of feeding increased on beta-agonists, according to Guy Loneragen of Texas Tech University. He also presented at the NCBA meeting.