Docking and Lamb Growth Study

Euan Templeton’s coastal Southland farm was the location for a two-year field trial during 2012 and 2013 on the effects of docking (tailing) lambs at different lengths. The results were that docking at either a short or long length, or leaving the tail intact has no long-term beneficial or detrimental impact on growth rates or time to reach slaughter. Results did show however, that leaving tails intact had a small positive effect on leg and total yield. The same effect was not seen in other trials carried out. Overall trial results indicate that farmers are not currently missing out on any large productive opportunities by leaving the tail longer or intact.

Euan Templeton has been leaving lamb tails un-docked for several years, especially singles, which are not docked, castrated or vaccinated. He did so to save work and to avoid what he thought was a growth check following docking. The numbers of classes of lambs left entire was extended until two years before the trial began. Euan decided to leave all tails on except for maternal breeding ewe lambs, from which the ewe flock replacements come. “We assumed there was a docking check, a 10-day period in which they recovered.” Euan was therefore keen to be involved in the trial to validate his assumption and pin down the animal health and welfare, processing and marketing consequences of tail docking at different lengths, or leaving tails untouched. The common reason for tail docking is to reduce dagginess and the risk of fly strike on the rear end.

Euan farms 445ha of flat land on the coast between Invercargill and Riverton, where annual rainfall is 1050-1100mm. He has 2380 ewes and 600 ewe hogget replacements, which are mated as hoggets to lamb as two-tooths. The maternal flock is Texel-Coopworth and he uses two terminal sires, Southdown and Sufftex. Good lambing percentages are around 155% and lamb covers are used for a few days to a week in bad weather. Mating begins mid-April and lambing is from September 10 onwards, with an aim to get the first drafting of lambs done around November 15 at the target weight of 35/36kg. Lamb weights average 18.5kg CW for the season and 55/56% yield on Viascan. Lambs are crutched once pre-Christmas and then cleaned up before they go to the works. They get a scabine scratch and five-in-one vaccine at tailing and a pre-wean drench. Those not drafted at weaning then get a second drench and may also be drenched in February and again in March. Euan is now using a triple drench.

Research was carried out by AbacusBio Ltd on four farms in Southland, Canterbury and Wairarapa in conjunction with Alliance Group Ltd, the UK supermarket group Sainsbury’s, Beef+Lamb New Zealand and the Ministry for Primary Industries’ Sustainable Farming Fund. The research investigated the effect of docking at various lengths or leaving the tail intact, on lamb growth rates to slaughter, carcass weight, meat yield, dag scores and crutching times.

Alliance Group General Manager Livestock Murray Behrent said there were many myths surrounding tail docking and the impact the practice was having on lamb growth to slaughter. Sainsbury’s joined the research because it was fielding questions from UK customers about tail docking and what the benefits were for carrying out such a practice. AbacusBio commented that some productive opportunities may exist in some farming systems from leaving the tails intact. These have arisen through improvements in understanding the effects that nutrition and parasite management have on dag formation, improved management through the removal of dags via crutching and the genetic selection of animals for faster growth rates and fewer dags. Some farmers also believe that leaving the tail intact may increase the muscularity of the hind quarter. Opportunities may also exist to increase revenue for farmers/processors if tails are longer, thus generating additional product for rendering or sale as a commodity.

The experimental design of the trial was a paired comparison where the effect of different docking treatments on lamb growth, carcass weight and saleable meat yield was measured between same-sex twin-born lambs rather than between unrelated individuals. That would minimise the effects of differences between the milking and rearing ability of the ewe. 300 sets of same sex twin-born lambs were tagged during lambing in September 2012 and 2013. Within 24 hours of birth they were tagged with an electronic ID, paddock number, visual tag number and week of birth recorded. Approximately 4 weeks later, siblings were randomly assigned to one of three treatments – short tail length vs. long tail length, short tail length vs. intact tail and long tail length vs. intact tail. When docked, the short tail length is approximately 3cm and the long tail length 6cm. If the tail of the lamb was docked, it was done using a rubber ring, with all ram lambs being left entire.

All trial lambs were weaned according to date of birth and at weaning weighed and dag scored. Siblings that reached the drafting weight of 36kg LW were sent for slaughter at Alliance Lorneville. Remaining lambs were run as one mob post-weaning and re-weighed and dag-scored regularly. When they reached the target weight of 42kg they were drafted for slaughter. At slaughter, lamb carcass weight and yield were recorded using Alliance ViaScan. The entire tail of each lamb was also collected, weighed (raw weight), skinned and re-weighed (tail product) to measure the amount of product generated from each tail.

491 sets of same-sex twin-born lambs (154 pairs of short vs. long, 176 pairs of short vs. intact and 161 pairs of long vs. intact) were slaughtered. The results were:

• Tail docking treatment had no effect on pre-wean live weight gain, weight at weaning and post-wean live weight gain.
• Tail docking treatment had a significant effect on dag score at weaning and post-weaning. At weaning, lambs with short and long tails had less dags than lambs with intact tails. At post-weaning, lambs with short tails had less dags than lambs with intact tails, with lambs with long tails having an intermediate score.
• Tail docking treatment had no effect on time to slaughter, carcass weight, Alliance ViaScan GR measurement or dressing out percentage.
• Tail docking treatment had a significant effect on total yield and leg yield but no effect on loin or shoulder yield. 

The overall results showed that leaving the tail longer or intact had no effect on growth rates from tail docking to slaughter and no effect on carcass weight. Some small positive effects of leaving the tail intact were found for total and leg meat yield. It was suggested this might be from the development of hind-quarter muscles used in wagging the intact tails. The same effect was not seen in other trials carried out.

Pre-wean live weight gain results indicated that leaving the tail longer or intact had no long-term detrimental or beneficial effect on growth rates from tailing to weaning for lighter or heavier lambs at the time of tail docking. It suggests that the early acute stress endured by lambs after docking has little or no detrimental effect on long term growth.

Overall trial results indicate that farmers are not currently missing out on any large productive opportunities from leaving the tail longer or intact.