In 2016, I conducted a study*, supervised by Dr Joe Brady BVSc, to determine the impact of the Breeching Process (now known as Sheep Freeze Branding) applied to the tail and perineal breech of merino lambs at lamb marking. We measured the average body weight gain and average fleece weight in the period following the cryogenic process and compared this group to a surgically mulesed with Tri-Solfen group and a lamb mark only group acting as the control.
What we found was that the surgically mulesed group had a lower average weight gain compared to the breeching process group, in both the first and second weight interval periods. This lower average weight gain was particularly noticeable in the first weight interval period, where the average weight gain for the surgically mulesed group was 50% below that of the breeching process group.
The comparison between the breeching process and the lamb mark only groups (the control group) showed was no average weight gain difference between the breeching process and lamb mark only groups throughout the trial period. From this study it is evident by the average weight gain comparisons that the breeching process did not have a negative impact on the lambs.
We also determined that there was no average weight gain difference between the breeching process group and the lamb mark only group in the first weight interval period.
The average weight gain over all periods, totalling 267 days, was 1.1kg lower in the surgically mulesed group compared to the breeching process group. The initial difference between these two groups in the first revisit period was 1.3kg. The average weight gain over all periods, totalling 267 days was 0.1kg lower in the breeching process group compared to the lamb mark only group.
Table 1: Comparisons of weight gains (total kg)
There was only a small difference in the fleece weights between the groups, with the surgically mulesed group fleeces 0.1kg lighter than those of the breeching process and lamb mark only groups.
Table 2: Fleece weights
From this, we can see that the surgically mulesed group received an initial setback that was quite marked compared to that of the breeching process group. This was evident at the first revisit, where there was a 50% reduced average weight gain.
After 267 days of the trial, the surgically mulesed group had an average weight gain that was still less than the average weight gain of the breeching process group. This is evidence that the impact of the surgical mulesing procedure was having a prolonged effect on average weight gain for the lambs that were mulesed.
*References the study A comparative study on the impact of the Breeching Process, on merino lambs by J. Brady and J. Steinfort, 2016.
Access the complete study a comparative study on the impact of the breeching process on merino lambs.
Dr Richard Shephard completed the statistical analysis of the comparative trial, which you can access here.