Polled genetics in Sussex cattle

During the 1950’s various breeders in the UK started crossing their pedigree Sussex cows with Red Angus bulls.

In South Africa this practice was first recorded in 1957 when P.Pretorius from Windhoek crossed cows from his Keres herd with a Red Angus bull. Bruce Evans advised him to keep meticulous records of these animals, even though they could not be registered at the time. The first polled animals to be imported was two cows in 1977, but they did not produce any lasting progeny.
The British Society closed it’s herdbook in the 1880’s after recording all of the pure Sussex cattle in the country at the time. The South African herdbook was never really open to start with as all of our foundation animals originated in England. In the 1980’s both the South African and UK breed Societies opened their herd books. Breeders who owned any polled animals now had the chance to register them in a seperate section of the herd book. As long as the herd books were in print there was a seperate section for polled animals. The progeny of any horned and polled animals were recorded in this section regardless of the progeny’s phenotype.The purpose was to keep the horned section of the herd book pure.

In the early 2000’s a group of breeders from South Africa visited Australia and imported the semen of three bulls. These were Willyung Mervin, Willyung BeeGee and Willyung Jack. The next imports were in 2011 when Huntersvlei imported Wellington 3rd of Goldstone, Mayfield Poll Captain 2nd and Mayfield Poll Captain 3rd. There are thus various polled bloodlines in the Society, but only a few breeders who focus on this trait. Initially there was a lot of interest among breeders but this interest dimished mainly due to the lack of depth and muscling in the earlier polled animals.

The commercial market in South Africa started demanding more polled bulls to decrease their labour and time spent dehorning. However the breeding of polled animals is not a quick process, so allow me to describe the theory and registration practices demanded by the Society.

For the purpose of this explanation pure polled animals are designated with the letters PP. Horned animals are designated the letters HH and a cross between polled and horned animals are designated as PH. When an animal has two of the same gene alleles it is described as homozygous (PP or HH). When it has two different alleles it is describe as heterozygous (PH).
It is important to understand that none of the polled bulls that were initially imported were homozygous, meaning not one of them had two polled alleles in their DNA. All were heterozygous or PH. However, the polled gene is dominant so a heterozygous animal will always appear polled or with scurs.

When these bulls are mated to horned cows (HH) there is a 50% chance that the progeny will be heterzygously polled (PH) and a 50% chance that they will be homozygously horned (HH). It is important to understand that an animal with horns carry no polled gene, regardless if it was born of polled parents.

When two heterozygously polled (PH) animals mate there is a 25% chance that the progeny will be homozygously polled (PP), a 50% chance that they will be heterozygously polled (PH) and a 25% chance that they will be homozygously horned (HH).

The challenge in the breeding of polled animal lies in the fact that apart from all the selection criteria regarding muscling etc. we now add another criteria in the form of polledness. The easiest way to determine the polled status of your calves is to keep records of the animals that were dehorned. This is unfortunately not possible in cases where dehorning paste is used. The surest way however is to have the animals DNA tested for the polled gene. This test clearly indicates whether the animal is homozygously or heterozygously polled.

Few breeders might be aware of the fact that the Society has clear rules regarding the registration of polled animals. These rules originated long before DNA tests for the polled gene were available. The Society’s Constitution determines that any polled animal’s name must have the suffix depicting its polled status beuing either P, PP or PH. These regulations can be viewed under the by-laws of the Constitution on the Sussex website.

The constitution further determines the Society needs to be notified in the event of a horned calf arising from the mating of animals with the designating letters P or PP. In the event of horned progeny arising from the mating of polled animals, the parents registered as P or PP shall be re-registered as PH. These rules and regulations originated from a time when herd books were still printed and polled animals as well as any horned animals born of polled parents were registered in a seperate section of the herd book. As the records started to be kept electronially this system fell by the wayside, although Logix still makes provision for the recording of an animal’s status which appears online and in printed catalogues.

It may appear as too much administration for the breeders of today to enter into the world of polled breeding, but at the time of writing these by-laws DNA testing for the polled gene was not yet available.The Constitution might have to be ammended to accomodate the advances in technology. What is however very clear out of the above regulations is that the opening of the Sussex Herd Book to polled animals was not taken lightly.

To ensure the quality of the polled animals bred and to move in a direction where all of the polled animals bred are homozygously polled, it is important that any breeder planning on breeding polled animals have a clear and consice breeding plan and program. Random breeding en the sellling of non-verified polled animals will only cause damage to the Sussex breed’s reputation. Have all your polled bulls’ DNA tested for the gene and insist on the results of any polled bulls bought in. Also have all the cows in your polled prgram tested. This is the quickest and surest way to breed homozygously polled animals.

To protect the value of the horned herds it is also of utmost importance that no horned animal out of polled parents be sold to stud breeders as a horned animal. Rather sell these bulls to commercial breeders as horned bulls, because as previously mentioned, no horned animal born out of polled parents carries the polled gene.

For any queries about polled breeding program guidelines or the DNA testing involved feel free to contact me at enrico.cronje@re.co.za.