Screw Claw

We bought a bull last fall for use on American cows purely for terminal show steers.  All of our other bulls are pretty strong maternally, we just needed a bull that would add bone and power to commercial American females.  He’s actually a PHA carrier (not the bull mentioned here, but yes, I thought he had the PHA phenotype from when I saw him) and so we already knew he’s terminal.

He was sound as could be at the sale.  We watched his feet closely to make sure he was correct.  Everyone who saw him back home was impressed by how well he moved and how sound he was for such a muscular, big boned bull.  He was described as “extra sound in his structure” in the catalog.  Honestly, the only reason we got him was his extra skin (which is a plus for what we do), his lack of neck extension, and his PHA status.

Well, he came out of the pasture with a screw claw this spring.

For the record, if I were a show jock I wouldn't mention the above.  I just want you to realize how honest a guy you have the opportunity to listen to here.  Sometimes it feels like you take me for granted and don't appreciate me like you did when we first met.

Since then I’ve been trying to find out everything I can about screw claw.  Like a lot of things, everyone seems to know exactly how it works but virtually nobody agrees with each other.  Rather than pretending I can make any sense of it all, here's everything I've heard/read...

Source – First clubby expert

It’s an autosomal recessive trait that has a tendency to come up in Heat Wave lines (the bull is a grandson).  There are very popular club calf bulls with it.

Source – Second clubby expert

Sometimes it will happen but he’s not sure what the genetic process is on it.  It won’t show up in the steers since they are typically done by the time they would display it.  He uses bulls with it and he just manages it by trimming the hooves of the bull once or twice a year.

Source – First veterinarian

It’s always passed on and any bull with it should be condemned.

Source – Second veterinarian.

He agrees it’s an autosomal recessive trait.  He refuses to pass bulls on breeding soundness exams if they have it but wouldn’t necessarily condemn a bull with it.  The only way he’d recommend using a screw claw bull is if it is for a strictly terminal operation where you don’t keep the replacement heifers.

He’s seen entire herds destroyed by breeders who refused to face the facts and kept everything out of the bulls.  When asked about breeds that he’s seen it in he said “Maine, a little bit in Beefmaster, Simmental, Simmental, Simmental, and SIMMENTAL” and I don't think I can justly convey the emphasis he put on that last "Simmental".

He claims his belief of the autosomal recessive nature theory resulted from a research paper but didn’t remember where it came from (if you know what he was talking about, PLEASE let me know).  He laughed when I asked him about the Huang Shanks paper mentioned below.

Source – Blackewlls’ Five-Minute Veterinary Consult:Ruminant, 2008

“The conformation of cattle seems to predispose some beef cattle to this disorder.  Affected beef cattle are usually heavy muscled with a wide rump.”

“Aggressive corrective hoof trimming” may be considered for growing animals.  It “may have a genetic component.”

Source – “Within herd estimates of heritabilities for six hoof characteristics and impact of dispersion of discrete severity scores on estimates” – Y.C. Huang and R.D. Shanks, 1995

Abstract Here

The heritability of corkscrew claw was calculated to be .05 which is just about as low a heritability as you can get.

“Low heritabilities with a relatively large proportion of permanent environmental variance to additive genetic variance implied that response to selection for a single score of corkscrew claw, interdigital dermatitis and sole ulcers would be small.”

“Large proportions of environmental variances were consistent with two hypotheses: (1) corkscrew claw may be influenced by other diseases or inappropriate hoof care…”

So what does all of that mean?  Most likely it means somebody will come along and leave a comment that all of the sources are wrong and that they’re the one who really knows how it works.  Bottom line, I like to be all ears on stuff like this but the more people/sources I listen to, the less I think I’ve learned.

p.s. Picture of a corkscrew claw. We had the bull mentioned above corrected of I'd post a pic of it.