• Isabel Vialoux

New docking regulations

There are new docking regulations coming into force on May 9th 2021. From this date, a sheep's tail cannot be docked shorter than the distal end of the caudal fold. This means that the docked tail needs to be long enough to cover the vulva in females and a similar length for male lambs.

The correct location to dock a lamb, source MPI (https://nzsheep.co.nz/site/wp-content/uploads/2020/12/42463-Tail-Docking.pdf)

The image to the right shows where the right location is to dock a lamb. The distal end means that the ring cannot be placed on the caudal fold (the pink part of the image), but just beyond that.


Docking is classed as a surgical procedure and there will now be two methods of docking that can be done legally: use of a rubber ring or a hot iron. This must be done before 6 months of age otherwise pain relief must be used and approved by a veterinarian. Research has shown that all the procedures used to dock tails are painful (Fisher 2011).


Why is this change being made? Lets take a look at some of the research around tail docking of lambs.


Key Points

  1. Pain indicators were more pronounced the shorter the tail was docked.

  2. Long and Undocked tails are the least justified, unless dags and flystrike are unlikely to occur i.e. lambs that are sent to the works early.

  3. Although dagging may be slightly more difficult when tails are docked at a slightly longer length, the decrease in acute pain and increased muscles around the base of the tail, outweigh this.

  4. The new regulations mean that sheep must have tails docked to the medium tail length (docked at the distal end of the caudal fold).

Firstly, why do we dock lamb tails?


Traditionally, docking has been important to reduce the build up of dags (dried faeces) around the rear of the lamb to reduce the risk of fly strike. However, the research around tail docking and faeces build up is inconclusive, with a New Zealand study, Scobie et al. (1999), reporting no relationship between tail length and cleanliness. The information around this is limited though so it is likely that this relationship is highly dependant on the farm environment and breed of sheep.


The same study also showed that docking makes shearing slightly easier. The study calculated that the average time spent shearing one sheep with an ultra short tail was 60 seconds compared with 72 seconds for shearing a sheep with a full length tail.


It is also believed breeding performance is improved in ewes with docked tails.


Let's now look at a New Zealand study that aimed to quantify both the pros and cons of tail docking lambs at different lengths.


This study compared lambs with the following tail lengths:

  • No-tail (4% tail remaining)

  • Short tail ("traditional docking" docked at the base of the caudal fold, 10% of tail)

  • Medium tail (covering the vulva in ewe lambs and at a similar length in males, 22% of tail)

  • Long tail (46% of tail remaining)

  • Undocked tails (100% of tail)

Let's call these the tail docking lengths.


Previously the docking guidelines have been directed by the risk of dags and flystrike on the welfare of the animal. This study looked at a few additional 'costs' associated with tail docking.


The consequences of docking at different lengths that were measured in this study included:

  1. presence of dags

  2. ease of dagging and shearing

  3. degree of pain and distress at docking

  4. formation of tail stump neuromas

  5. the weight of the rectococcygeal muscles.

Stump neuromas are an abnormal nerve growth and can be a result of a detatched nerve shaping into a stump i.e. the end of the tail after docking. Stump neuromas can cause a range of pain levels, from very painful to no pain felt at all. Stump neuromas can also resolve over time.


Recto-coccygeal muscles are the muscles at the base of the tail, just above the rectum. The recto-coccygeal muscles were bound to the rectum and vagina and their ends were inserted at the pelvis, and at the second tail vertebra.


Another potential consequence of tail docking could be an increased risk of prolapse. In a previous summary we have done, there was found to be no relationship between vaginal prolapse and tail length. We have not yet summarised the relationship between rectal prolapses and tail length, but stay tuned for a summary on this in the future.



There were three experiments reported in this paper, all tails were docked using a rubber ring.

The first experiment used 5 male and 5 female lambs (one male and one female for each tail docking length) to measure the distribution of dags and used 8 or 9 lambs per tail length at 8-months of age to examine the tail tip and measure recto-coccygeal muscles. The second used 10 female lambs for each tail docking length, and the third experiment used 25 male and 25 female lambs.


Experiment 1


Dagging and shearing required additional effort in Long and Undocked animals. There were no differences in average dag scores between tail length groups, but few lambs had dags in this study. Most lambs had dag scores of 0-2.


The study reported that shorter tail docking resulted in significantly lighter recto-coccygeal muscles as you can see in the graph below. However, they did not report the significance between each tail length, just that the shorter tail length (i.e. no-tail and short tail) had significantly lower muscle weight.


You can see in the graph that the No-tail and Short tail length are lower than the Medium, Long and Undocked tail lengths. This indicates less muscle around the rectum which could result in an increased risk for prolapse, however we will look at this in more depth in a future summary.


Graph 1. Average weight of recto-coccygeal muscles (g) in male and female lambs at different tail lengths.

There was evidence of neuroma development and degenerative nerve changes in the tail stumps of over half (15/26) of the No-tail, Short and Medium lengths compared with few of the Long and Undocked lambs (3/17). A Neuroma is an abnormal nerve growth that can cause pain long term.


This means that there is a risk of longer term pain associated with tail docking in lambs with a shorter length than those with longer tails, however, this is not always indicative of increased sensitivity and pain as some neuromas are resolved over time. I guess this nerve damage could be deemed unnecessary trauma as a result of tail docking.


An interesting addition to the results were that there was evidence of post-farm injury (injuries in transport or while in the yards prior to slaughter) to the base of the tail in Long or Undocked tail lengths. This could be a reason for favouring Medium length over the Long or Undocked tail lengths.


Experiment 2: Pain and distress indicators


In Experiment 2, behaviour after rubber ring docking was measured and included behaviours such as walking, standing, sitting, lying on their sides, turning towards their tails, rolling on the ground, and walking on their front knees. It was deemed that if the lamb was on the ground, the lamb was showing signs of pain and distress and if they were standing then they were not showing signs of distress.


The distressed behaviour peaked at 15-35 minutes. In the graph below you can see the peak number of lambs that showed signs of distress for each tail length and the number of lambs that were still showing signs of distress after 35 minutes. There were 10 lambs in each of these tail length groups, so you can see that all lambs with a Short tail were showing signs of distress.


Graph 2. The affect of tail length on the number of female lambs spending time on the ground (a measure of restlessness and thus pain and distress) peak number and number showing signs of distress 35 minutes after docking by rubber ring.

The shorter the tail the more lambs that showed signs of distress (lying on the ground). The shorter the tail the longer the amount of time spent displaying signs of distress. This shows that if the tail is docked to a longer length, then there is likely to be less time spent in pain.


Experiment 3: Dags


Only Short (traditional length) and Medium (new regulation length) tail lengths were compared for the amount of dags in this experiment.


The slightly longer length (Medium) was associated with more lambs that were likely to be difficult to dag. The measure of being 'difficult to dag' was the amount of dags on each lamb on a scale of 0, no dags to 5, fully covered in dags. There were 11/44 lambs that were difficult to dag in the Medium tail length group compared with 4/44 Short tail length lambs that were difficult to dag.


Overall, Medium tail lengths are likely to be more difficult to dag than Short, however, only the dag scores were measured in this study, not the time taken to dag the lambs.


The authors note, that in instances where dags and flystrike are not an issue (e.g. when lambs are slaughtered early in the season) then lambs should not be docked at all.



The authors concluded that Short or Medium length are both appropriate, however, there are instances where the longer, Medium length would be more appropriate as they are associated with less distress, stump neuromas and greater recto-coccygeal muscles.


The animal standards and guidelines are often set when determining if the harm to an animal is reasonable or necessary (is outweighed by the benefits). It is likely that this has occurred for tail docking, although dagging may be slightly more difficult when tails are docked at a slightly longer length, the decrease in acute pain and increased recto-coccygeal muscles outweighs this.


Also the increased importance placed on public perception could play a factor in this change, it is not acceptable to place an animal under unnecessary harm. What was deemed necessary in the past, is likely now deemed unnecessary. Therefore, resulting in the slight change in docking length.


The rules for tail docking length and method are changing. The new regulations mean that sheep must have tails docked to the medium tail length (docked at the distal end of the caudal fold) and can only be docked by using a rubber ring or hot iron. This is because docking is classed as a 'painful procedure' and in most cases, docking to a slightly longer tail length results in reduced pain.


The new docking regulations will be in place from May 9th 2021.


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Full Papers:

Fisher AD (2011). Addressing pain caused by mulesing in sheep. Applied Animal Behaviour Science, 135(3), 232-240.


Fisher MW and Gregory NG (2007). Reconciling the differences between the length at which lambs' tails are commonly docked and animal welfare recommendations. Proceedings of the New Zealand Society of Animal Production, 67.


Scobie DR, Bray AR and O'Connell D (1999). A breeding goal to improve the welfare of sheep. Animal Welfare, 8, 391-406.