During the last couple of months bull sales of many breeds have been held across the state. These have traditionally been timed for autumn calving herds.
At these sales bull breeders of polled breeds generally identify any bulls in their catalogue that have scurs.
Scurs are small horn like structures that in young cattle are usually not attached to the skull.
They often look like small horn buds, and can vary in shape and length. In older cattle they can sometimes attach to the skull like a horn.
Having scurs is a separate trait to being polled or having horns. Genetic researchers have found the gene controlling it lies on a different chromosome to that gene affecting the horn status of the animal.
Are there any disadvantages to sale bulls being identified as having scurs if we know it is a separate trait to horns in Bos Taurus cattle?
Whilst these animals should be identified, it is interesting that some bull buyers won’t bid on scurred bulls, even when they think it might be a separate trait.
What’s going on here?
Breeders of polled cattle just don’t want horns.
They don’t want bulls that may be heterozygous for the trait – in other words bulls that carry the horn gene.
If any of their cows back home are carriers they run the risk of some horned calves if the bull is also a carrier.
Fortunately many seedstock producers publish the results of their animals being tested for the horned gene.
Are bull buyers justified with this reasoning to ignore scurred bulls?
Firstly, if they as buyers of bulls are hesitant to buy scurred animals then maybe the buyers of their sale progeny may also be hesitant in buying any scurred progeny.
Secondly there is literature that suggests there may be an interaction between different copies of the two genes and that some scurred male cattle are more likely to carry one copy of the horned gene.
American work suggests that in Poll Herefords, avoiding using sires with scurs should increase the frequency of the gene for polled – ie less chance of the horned form of the gene.
Often we see scurs in male cattle more than in female cattle. Scurs are a sex influenced trait.
They’re not ‘sex linked’ where the gene is on the X chromosome, but rather ‘sex influenced’ where the expression of the trait is different between males and females.
Generally it is believed that in male cattle the scur form of the gene is dominant- in female cattle it is recessive.
Heterozygous carriers of the gene will only show scurs in males. We tend to see scurs more in bulls than in cows.
Finally there is also some work suggesting that the frequency and size of scurs is related to the shape of the poll. More cattle with flatter polls had scurs than cattle with peaked polls!
Interesting enough, but usually there are far more interesting and economics things to select cattle for!