dipping with those of pour-on and injection.
Brief comparisons of the mechanics of sheep plunge dipping with those of pour-on and injection. The Pollution Reduction Programme assumes that it is necessary to dip sheep for ectoparasite control apparently because of the absence of proven alternatives. Sheep dipping is considered a tradition on many sheep farms but there are many reasons to question its sustainability especially as the stream surveys carried out in the south west area of Wales have found extensive pollution events from both cypermethrin and diazinon. If the former is withdrawn there will be a greater number of diazinon incidents resulting from the likely wider adoption of diazinon based sheep dips.
Although diazinon is not as toxic as cypermethrin, it still has a detrimental affect on aquatic invertebrates at the concentrations found in impacted streams. The observations given below are not listed in any particular order. Points in favour of plunge dipping: a. Cheapest method in treating a large flock in terms of the cost of the toxicant but not taking the cost of disposal, site cleansing and post dipping precautions into account. b. Quick turn over in well laid-out set-ups. Against plunge dipping: a. Handling the dip concentrate is a serious health hazard. b. Although possibly the most effective way of treating animals, plunge dipping is possibly the most inefficient way of pesticide use as there is much waste.
Only part of the pesticide will be retained in the target area, the rest being disposed of on good agricultural land or dripped over hard surfaces and pasture where it continues to be potent and hazardous in the environment. c. A large volume of spent dip has to be disposed of safely within the Ground Water Directive that has strict site demands that have to be compromised in most hilly high rainfall areas. Because sheep farms seldom have the necessary equipment for handling surplus ‘dip chemical’ their disposal is often contracted out and contractors are not noted for their integrity. d. Large quantities of contaminated water are generated in washing down dip surrounds, clothing, utensils and transport vehicles and this water is unlikely to be disposed of in the correct manner. e. Careful measurement of all materials is required, including initial water volume and a continuous record kept for volume top-ups to maintain the correct dip strength. f.
Animals receive a variable dose of material due to ‘stripping’ and topping-up. g. Plunge dipping is very stressful to sheep. h. Ewes must be in the bath for the prescribed time (very rarely achieved) and be completely submerged at least once. i. Lambs need to be barrel dipped – in small groups, possibly more than once. j. Faeces and other contaminants, eg straw (which ‘strip out’ active ingredients) has to be removed from the dip bath frequently. This material is highly contaminated and has to be disposed of in a prescribed manner. k. It is recognised that dipping can induce sheep blowfly strike. l. Mis-mothering can be a big problem. m. Dipping can be stressful to farmers/operators wearing the correct protective clothing especially on a good day for dipping (warm and sunny). n.
The use of buffer material to aid containment of dip poses further problems of safe disposal.( see i. above). o. Dip baths per se are a hazard. They will fill several times each winter and the contents are most likely to be emptied as clean water although contaminated. p. Dipping requires a drying spell and sheep have to be kept away from water courses which would be most difficult after “winter” dipping in high rainfall areas and in wet seasons. q. Dipping is likely to need extra manual help to ensure smooth running. r. A disposal permit is required and possibly a contractor hired. s. A constant worry over possible leakage of dip fluids and prosecutions Alternatives to plunge dipping: Showering and jetting are not considered as good practise as the treatments may not readily penetrate a tight fleece and would therefore readily wash off in wet weather. Adjacent land is contaminated and the washing down water has to be contained for safe disposal.
They are stressful to animals. The use of pour-ons involves pouring a measured dose of the chemical along the animals dorsal mid-line. An efficient application will give good protection for a period similar to that of dipping. Pour-ons development was investigated in Wales in the early 1980s and the farmers involved in the trials invariably adopted the new method. Advantage of pour-ons a. Pour-ons offer economy in pesticide use and there is no problem with disposal at the end of the day. Containers must be returnable and it is suggested that the disposal cost is paid for when purchased. b. No problems in calculating the correct concentration rates which is essential when dipping. c. No special facilities are required other than normal gathering pens and gated runs. d. The pouring on procedure is readily learnt. e. Each animal receives the correct dose. f. Animals are treated far more quickly and there is no end of day chore of yard cleaning and safe disposal of surplus dip. g. No stress to animals. h. Mis-mothering problems are minimal. i. Small batches of sheep can be treated as and when necessary. j. There is closer contact with the sheep allowing good shepherding. k.
The practice is less weather dependent with no essential aftercare. l. No stress to farmer/operator and protective clothing requirements are minimal. m. Far more environmentally friendly than dipping with less chance of watercourse pollution. n. The cost of the upkeep of the dipping area is saved. o. Fleece will have less residual pesticide. (IPPC legislation based on EU council Directive 96/61/EC). a. Injectables have the same advantages as pour-ons and in addition offer a better control of sheep scab. Some may also control internal parasites. b. It requires less labour than dipping, and injecting is already a common practice on sheep farms. Dipping needs to be phased out and sheep farming brought into the modern era. Farm literature relating to the control of sheep skin parasites should list all effective methods. Ceri Evans and George Sykes (WSTAA) 24:03:200