Tip Spraying of Sheep for Parasite Control

New Zealand Journal of Agriculture, Volume 99, Issue 5, 16 November 1959, Page 431

Tip Spraying of Sheep for Parasite Control

By

L. K. WHITTEN,

Parasitologist, Department of Agriculture Animal Research Station, Wallaceville

TIP spraying of sheep for the control of keds and lice is a recent development which has become very popular with New Zealand sheep farmers. The success of the procedure depends on the deposition of enough insecticide on the fleece in such a way that it comes into contact, sooner or later, with all the parasites present. It should persist in the wool for long enough to give a complete kill of the next generation of parasites hatching out from eggs or pupae.

IT is clear that tip spraying cannot give complete saturation of the fleece and therefore it is suitable only for use with insecticides that possess the property of diffusing down the wool fibre and spreading in that way throughout the fleece. Only three insecticides -in ■ common use - at present diffuse sufficiently rapidly to justify their use in surface application. These are dieldrin, aldrin, and diazinon. The concentration of the insecticide in the spray fluid used for . surface application is much greater than that used in plunge dipping or saturation spraying. Speed of Sheep Passing through Spray A large number of factors can influence the amount of wash that is deposited on the sheep. One of the most important is one over which we have only limited controlthe speed at which the sheep passes through the chute. Observations at Wallaceville have shown that sheep from the same pen may travel at rates from 1 ft per second to 7 ft per second and that between three and four times as much fluid is deposited on the slowest as on the fastest moving sheep. An adequate amount of insecticide must be deposited on the sheep that moves most rapidly through the spray, and naturally all other sheep will receive more than they require. Recommendations for dilution are based on this requirement. Space between Sheep Another important factor in determination of the amount of wash wasted is the space between successive sheep. When sheep are running head to tail

less wash will obviously be wasted than if there is room for another sheep or two between them. Pressure When the pressure falls below the recommended one, owing to a faulty gauge, reduced pump revolutions, or to blockages, the amount of fluid deposited is reduced. The reduction in deposit is much less than that due to speed differences. In one test a machine running at half pressure still deposited only 30 per cent less fluid per sheep. Length of Wool Length of wool has an important bearing on the amount deposited per sheep. A sheep with 3| in. of wool retained,..twice as much fluid as one with . only J in. of wool. But if one considers the amount of insecticide deposited per pound of wool instead of the amount retained per sheep, the situation is entirely different. The sheep with | in. of wool retained four times as much insecticide per pound of wool as did the one with 3J in. This point is a very significant one, as it serves to stress the importance of using tip spraying methods when the : wool is as short as possible. Under these conditions, complete parasite control is much more likely

to be achieved than when v the wool is longer. .. \ Factors Governing Efficient Operation . Efficient operation in tip spraying depends on the following factors: 1. Pressure. Recommended pressures should be maintained throughout. Motors, pumps, and gauges should be checked regularly. The, water supply should be clean and nozzles should be watched closely for signs of blocking. 2. Concentration. The manufacturer’s recommendations should be followed in every detail, and dilutions should be made accurately. 3. Wool length. Spraying should be done with the wool as short as possible and, in any case, not later than three months after shearing. 4. Speed. The chute should be set up so that the sheep run through it without interruption and at the fastest possible rate. If necessary, provide drainage to prevent the accumulation of surface liquid in the yards which may cause sheep to baulk. All sheep must be properly treated. Failure to do this might necessitate re-treatment of the entire flock later.