"TVSP"

Again the argument on the length of the tail dock in sheep has surfaced. The tail has many functions; the tail at the full length in the ewe, will protect the udder from chilling. A Scottish Blackface on the hill retains all the tail, because the shepherd knows that in the extreme conditions that the ewe will be raising her lamb, the udder needs protection to prevent chilling and possible mastitis. Very often, when a sheep is defecating, it will shake the tail to spread the fecal pellets.

But what happens if the tail is left long on our lush pastures. Soft feces collect under the tail, making an ideal site for fly strike. Flies lay eggs in and around the fecal mass, hatching into maggots which will attack the flesh under the tails, even entering the rectum and vagina. A lamb with fly strike is not a pretty site and will almost certainly die.

However, completely removing the tail to prevent fly strike has its problems too. Certainly, some rectal prolapses may be genetic in origin, but many are the result of this tail removal. The problem lies in the anatomy of the region; the anus and the vulva are held closed by sphincter muscles, circular muscles round these openings, which relax to allow feces and urine to be passed. To have strength, any muscle must be attached to a bone of the skeleton; these muscles have two attachments to the underside of the tail bones. One runs forward and the other back along the tail. When a tail is docked short, the rear muscle attachment is removed, thus weakening these muscles.

The weakness may not be apparent immediately, but very often a tailless sheep will invert the rectum when passing feces. Eventually the rectum will not completely return, leading to a prolapse. In the late 80s, the vogue was for tailless sheep, and there was a significant problem with prolapsing ram lambs in the test station. As tails were left longer the problem disappeared.

Every year at lambing, there are queries on prolapsing ewes in the last month of pregnancy. In many cases a contributing factor is a short dock and the loss of half the muscle attachment. In the last month of pregnancy, the muscles of the pelvis including the retainer muscle of the vagina and the sphincter muscle of the vulva are relaxing under the influence of hormonal change in preparation for lambing. An already weakened vulva muscle is made weaker by these hormonal changes; the result is a vaginal prolapse. Of course, prolapses will occur in ewes with longer tails because of other factors, such as selenium deficiency at this stage of gestation.

Each method of docking, the rubber ring, the knife, the Burdizzo and knife will produce the same results if performed with care and correctly. At the moment the recommended site is at the end of the web underneath the tail. As this may leave too short a tail in the adult ewe, work is underway to determine the correct site.

The Code of Practice recommendation to dock to the lower lip of the vulva in ewe lambs and to below the rectum in the ram is a compromise between no dock, with the risk of flystrike, and a complete dock with the possibility of rectal and or vaginal prolapse. This recommendation was agreed to by the committee which included producers, veterinarians, and members of the humane society with input by provincial sheep associations. This compromise also addressed the concerns of the humane movement that docking was an unnecessary mutilation. So the question remains, why to continue to very short dock or completely remove the tail when the compromise length satisfies the health needs of the sheep?

This Infosheet was authored by: Dr. S. John Martin, BVM&S, MRCVS, OMAFRA Veterinary Scientist, Sheep, Goat and Swine

For more information... regarding tail length contact Dr. S. John Martin, BVM&S, MRCVS at: jmartin@omafra.gov.on.ca

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