Genetics – A Question about Spots on the Ears

By Wendy Allison, Wairarapa

In the last article in our series about genetics, readers were invited to submit any questions they might have about genetics.  Lovato Sara, an Italian breeder of Brogna Sheep, an endangered breed native to Veneto emailed the following comments and question.

Note:  the original email was written in Italian, and Google translate was used to convert it to English. Some of the original email text has been edited or omitted.

From Lovato Sara

The Brogna sheep is of medium size on 50kg; its main feature is that it has a red / brown background and white fleece. At birth it is red spotted, and in the area of the fleece, as the fleece grows, it becomes white and the spotting remains exclusively on the legs and head.

In recent years, however, there has been the presence of births of black lambs from white parents. It was already known of the existence of the black recessive gene, but it began to occur very frequently.

In lambs born white to mixed parents, in my case white ram and black ewe, I noticed an intensification of the background red and the presence of black spots, more or less defined. Could this be an indicator of transmittability of the black color?

The presence of these spots is  also identified in certain white adults, ears and paws area. I would like to be able to identify the carriers without specific genetic tests, but with visual tests that will give the highest percentage of chance that the lamb will be born black.

Wendy’s Answer

I’m interpreting your question to be whether spots on the ears indicate an animal is heterozygous for colour.

I will assume that your sheep are red/brown as a tan expression of white/tan on the agouti locus rather than as an expression of brown on the brown locus. This is because if they were brown (rather than white/tan), crossing a black ram over a red/white ewe would produce a black lamb, and you’ve said that this cross produces red/white lambs (sometimes with black spots). You can easily check this by looking at the nose leather, which should be black (not brown).

If the nose is black, this means that the colour of the wool is not from recessive brown genes but from white/tan, and the hair/wool is tan coloured. It would be possible to breed black lambs from white/tan parents if recessive colour is present in your flock. You’ve mentioned that you know black exists as a recessive gene in the breed, and you should be able to easily select for black lambs by keeping and breeding from black lambs and from the parents that produce them. You should be able to predict what colour lambs they will have using the punnett squares as in the first article about genetics on the BCSBA website.

Small black spots on ears and legs are reasonably common in other breeds with white/tan dominance. They are generally not considered to be a sign of carrying black on agouti as they also happen on animals that do not carry the black gene – however I have noticed in my own flock that white animals carrying the black gene do seem to more commonly have noticeable small black spots on ears and legs.

Your own breeding records will be the most useful thing to help you know if this is an indicator in your flock. If you know which animals are mixed white/black and keep records of which ones have these spots and which don’t, it should become clear within a few generations if it is a reliable indicator for you, however at this point I would not assume that an animal with black spots on its ears is carrying the gene for black.