Ask the Vet

Polled Bulls

Depending on genetics, some calves a polled bull sires may develop horns or scurs. (Progressive Farmer photo by Victoria G. Myers)

Question: We bought a polled bull to get out of the dehorning business. Now, some of the calves are developing horns. It is mostly the bull calves, but we have a few heifers with them. I have been told they are not really horns but are scurs. In any case, some of them are getting fairly large, and we may have to remove them. I thought the polled bull would get rid of all horns?

Answer: Scurs are small, hornlike growths that develop at the same site as horns and can range from a "thumbnail" patch to several inches long. They are usually not attached to the skull.

Horns and scurs have separate but related inheritance. Scurs only develop in heterozygous polled cattle (Pp). Homozygous polled cattle (PP) will not develop scurs. While the polled gene (P) is dominant in all European cattle, the scurred gene (S) is dominant in bulls and recessive in females. Both homozygous scurred (SS) and heterozygous scurred (Ss) bulls can develop scurs, while only homozygous scurred (SS) females can develop scurs. Horned cattle cannot have scurs, since horns develop where scurs would.

So let's look at your herd. If both heifers and bulls have scurs, you must have both the horned gene (p) and the scurred gene (S) in your cow herd, since your cattle have horns and some of the heifer calves have scurs. Your bull would have to be heterozygous (Pp) polled and carry at least one scur gene for his heifers to have scurs. Another consideration is that some of these calves could be horned and not scurred. It gets a little confusing, and I could complicate it even more with the "possible exceptions" and the inheritance of horns in Brahman-influence cattle, but this covers most cases.

So what can you do? At this point, you could sell this bull and buy another bull that has been tested and found to be homozygous polled (PP). That would solve your problem. You could also dehorn any horned calves as soon as possible and remove the scurs that get large enough to be a concern.