What is the difference between polled and scurred?

Can polled cows make a difference in your herd? If you want to save money on dehorning and achieve better animal welfare routines, then the answer is “Yes”.

In this article, we will explain if a polled bull can have horns and how polledness and scurs are different from one another. We will also look at how two different genes control polledness and the scurred condition in cattle.

Focus on polledness

Horn is a kind of bone growth from the cranium and it can have many different designs. They can be small or big, curved or straight and bend in different directions.

The variation is breed specific which indicates that it is controlled by genes. If the horn is missing, it is called polled. In some cattle breeds, the polled gene has been a part of the breeding program for many years; hence, many of the animals in the breed are polled. In other breeds, the polled gene is not observed.

Research indicated that the polled trait is controlled by one pair of genes. As in the case of human beings, in cattle, each individual has two copies of most of the genes, and one of the copies is passed along to the offspring.

A calf inherits a gene from the mother (dam) and one from the father (sire). In this case, a gene for polledness or horns from each parent. A polled animal that has inherited one polled gene and one horned gene from the parents is called heterozygotic polled, while an animal which has inherited two polled genes from the parents is called homozygotic polled.

A dominant gene

The polled gene is dominant over the horned gene. If an animal inherits the polled gene from just one of the parents, the animal will be polled. This gives a great opportunity to breed many polled animals fast. But how is the polledness inherited from generation to generation?

In the figure, you can see that the mating of a homozygotic polled (PP) animal with a horned animal (hh) will only give polled animals.

The “P” shows the polled gene, while the “h” shows the horned gene. If the animal just has one polled gene (P), it will have no horns.

If the horned animal (hh) instead is mated with a heterozygotic polled (Ph) animal, only half of the offspring will on average be polled. It becomes a bit more complicated if two heterozygotic polled animals are mated. In this case, 75% of the offspring will be polled and out of the them, 1/3 will be homozygotic polled (PP).

When a homozygotic polled (PP) animal is mated with a heterozygotic animal (Ph), all the offspring will be polled and half of the offspring will be homozygotic polled.

Scurs are less common on cows

Scurs are a kind of horn and they can have many different forms, but they grow slower than a normal horn. However, scurs do not normally grow on the cranium, so they are loose if you hold and move the “horns”.

There’s no test for scurs, so to be sure, it is necessary to perform a scan of the cranium and the horns. The reason is that some scurs will crown a small bit to the cranium, so they do not move when you try to move them.

The good thing for you, as a farmer, is that bulls much more often have scurs than cows do, and that polledness affects scurs.

To make it simpler, we start to reduce the number of animals where scurs have an effect. If the animal has two horned genes and therefore is horned or two polled genes and therefore is homozygotic polled, scurs have no effect.

The scurred condition has an effect when the animal has one polled gene and one horned gene, and therefore is heterozygotic polled (Ph).

Scurs are controlled by one pair of genes like polledness. If the animal has two genes for Scurs (Sc-Sc), both male and females will get scurs. On the other side, if the animal does not have any genes for scurs (sc-sc), the animal will not get scurs and will be totally polled.

If the animal has one gene for scurs and one normal gene (Sc-sc), the animal is heterozygotic for scurs. In this case, there will be a difference between males and females. The males will, in this case, get scurs, while the females will not get scurs and therefore will be totally polled. In table 1, you can see an overview of scurs and polledness.

Gene pair in the animal	Females	Males
PP ScSc	Polled	Polled
PP Scsc	Polled	Polled
PP scsc	Polled	Polled
Ph ScSc	Scurs	Scurs
Ph Scsc	Polled	Scurs
Ph scsc	Polled	Polled
hh ScSc	Horned	Horned
hh Scsc	Horned	Horned
hh scsc	Horned	Horned

Why are there polled bulls with horns?

Scurs is the reason why some of the polled bulls have “horns”, but in your herd, most of the polled females will be totally polled.

Next time you see a picture of a polled bull with horns, please remember those are scurs, and therefore, he can still give polled offspring.

Can a polled bull have horns? No, he can’t have horns. However, the polled bull can have scurs which look like horns. Remember that a polled bull with scurs still gives the polled gene to 50% of his offspring, and they will be polled, but some of them can have scurs.

In VikingGenetics’ breeding programmes for VikingHolstein, VikingRed and VikingJersey, there is focus on polledness. Reality has shown the benefits farmers can get out of polled genetics. Those advantages can be seen in the bottom line when dairy farmers avoid investing in dehorning. On the other hand, using genetics from polled bulls also counts as a good animal welfare practice.

Jakob Lykke Voergaard

Product Manager VikingRed