Around the world, there is a widespread practice of shortening lambs' tails by cutting in long-tailed sheep breeds. This is done primarily to prevent bacterial infections and insect attacks, otherwise known as flystrike. However, it should be noted that this practice inflicts pain and stress on the animals. Studies have identified genetic variability in sheep tail length, including the role of the HOXB13 gene. We investigated gene expression differences between the GG genotypes (long-tailed animals) and CC genotypes (short-tailed animals) using the qPCR method in thirteen rams of the Improved Jezersko-Solčava breed. Results showed that in skin samples from the tail and rump, the HOXB13 gene is expressed significantly differently between the CC and GG genotypes, varying along the cranial-caudal axis. At the tip of the tail, the HOXB13 was expressed almost 13 times higher in the CC genotype than in the GG genotype, and about five times higher in samples from the middle of the tail. In both genotypes, the expression of HOXB13 increased towards the tip of the tail. However, in internal organs, we did not observe significant differences in expression between the two genotypes, with very low or no expression detected. The results further confirm the hypothesis of the causality of the HOXB13 gene in determining the tail length through the molecular mechanism of differential expression in the cranial-caudal direction of the tail. Applying these insights in sheep production through breeding or biotechnological applications could reduce or even eliminate the need for the painful procedure of tail shortening, thus improving animal welfare.
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