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Does tail docking method influence breech flystrike in later life?

By Jen Smith, CSIRO Agriculture

February 2016

 

There are several common methods for tail-docking lambs in Australia. Have you ever wondered whether your chosen tail-docking method has an effect on the breech flystrike rate in your flock later on? A study has been conducted to investigate this and it turns out there is no consistent difference between the four methods described below.

A trial was conducted at the CSIRO property, Chiswick, near Armidale, NSW, where the flystrike season usually runs from October to April inclusive.

The sheep used were the 2012- and 2013-drop progeny of the Armidale breech flystrike genetics flock, which included both the Resistant and Susceptible flystrike selection lines.

These sheep are managed under flystrike challenge conditions, with no use of preventative chemicals, and they have flystrike records across years.

Breech flystrike associated with these four tail-docking methods (images shown below) were compared:

  1. Regular hot docking iron
  2. Te Pari Patesco hot docking iron (a gas knife with rotating anvil intended to stretch bare skin over the end of the docked tail.)
  3. Knife
  4. Elastrator ring

Regular hot docking iron
Regular hot docking iron
Tepari Patesco hot docking iron
Tepari Patesco hot docking iron
Knives
Knives
Elastrator pliers and rings
Elastrator pliers and rings


The same lamb-marking contractor was engaged in both years and the brief was to dock female lambs to the tip of the vulva, and males to equivalent length or slightly shorter.

Breech flystrike was recorded as the count of breech strikes for the season when the sheep were weaners, yearlings and adults.

The overall breech flystrike rates across the year and sheep class groups ranged from 9.9% to 18.5% (with no use of preventative chemicals). Compared to the previous 10 years, these were low to moderate flystrike challenge years.

Weaner breech strike. As might be expected, the year the weaners were born (due to the ensuing seasonal conditions), their selection line (whether Resistant or Susceptible) and their sex (females have urine stain contributing to breech strike) all had significant effects on weaner breech strike. The birth-rearing type (twin or single) also had a significant effect, with twins tending to have lower rate of breech strike.  Based on evidence earlier in the project, this is due to twin lambs being less wrinkly and is thought to be associated with lower early life nutrition. The age of their dam, and their weaning age did not have significant effects on weaner breech strike.

The tail docking method also didn’t have a significant effect when averaged across years. However, there was a significant interaction between birth year and tail docking method; this means the flystrike rate from the different tail-docking methods was different in different years. Specifically, among the 2012-drop progeny those tail docked using the Te Pari Patesco hot docking iron experienced significantly lower weaner breech strike than using a knife, but in the 2013-drop, the Te Pari Patesco hot docking iron resulted in significantly higher weaner breech strike than all of the other tail-docking methods. The reason for this difference across years is not known.

Yearling breech strike. Birth year, selection line and sex were also significant effects on yearling breech strike, but tail-docking method was not significant. For yearlings, there was no interaction between birth year and tail-docking method.

Adult breech strike. Only the 2012-drop ewes that were retained for breeding had adult breech strike records, so there were no birth year or sex effects to consider. Whether they were from the Resistant or the Susceptible selection line had a significant effect on adult breech flystrike (i.e. there was more strike in the Susceptible line). Fertility also had a significant effect on breech flystrike in the breeding ewes; those pregnant to lamb at the start of the flystrike season had a lower adult breech strike rate than those that were dry (19% versus 31%). There is evidence that this is associated with differences between wet and dry ewes in wool coverage of the breech and crutch, and staple length grown, but that is another story.

The tail-docking method did not have a significant effect on adult breech strike.

Conclusion

There is no evidence for a consistent effect of tail-docking method on breech strike rate. Based on results from this study, no firm conclusion can be drawn about the relative merits of different tail docking methods with respect to later-age breech strike rates.

This study was conducted in a summer-dominant rainfall region where dag is usually not the problem that it is in southern Australia. The results obtained here may not hold in those regions where dag is a persistent issue, or in flocks or regions where more of the breech strikes start on the tail rather than breech (i.e. below the tail). In this flock, very few (less than 5%) of breech strikes are regarded to have started on the tail. The scar pattern arising from tail-docking, or wool overhang on the end of the docked tail may become more important in flocks and regions where dag is an important factor in breech flystrike susceptibility, or where more of the strikes commence on the tail.

This study only examined the possibility of an association between tail-docking method and breech flystrike in later life. There may be implications of the different tail-docking methods with respect to post-tailing infection rates and lamb welfare at tail docking, but that was not the subject of this study. Other studies are underway by CSIRO at Armidale on the animal welfare implications of tail-docking and castration methods.