NEW METHOD of DIPPING SHEEP

New Zealand Journal of Agriculture, Volume 71, Issue 4, 15 October 1945, Page 341

NEW METHOD of DIPPING SHEEP

By '

J. E. DUNCAN,

wool

Supervisor, Wellington.

Australian Power-spray System Tested in N.Z.

THE idea of spraying or showering sheep is by no means new, and has been in operation in Australia, particularly in Queensland, for a good many years. In New Zealand at. least one shower dip has been in existence in Canterbury for 10 years or more. The method used in these instances could be called the gravity system, as the dip is lifted by a pump to a flat galvanised iron roof perforated with many small holes, and falls like rain on the sheep in the pen below. The main disadvantages were that the small holes easily blocked up, necessitating continuous sweeping of

the roof, and the sheep were not thoroughly wetted to the skin all over. For these reasons the system > never became widely popular, and was not considered to comply with the legal dipping requirements of most of the States concerned. Power spraying, is quite a different proposition, and here an engine-driven centrifugal pump is used to deliver a large volume of dip under considerable pressure from specially-designed spray nozzles. With the pressure available it is an easy matter to have nozzles on or beneath the floor as well as above and at the sides of the pen,

so that the sheep are sprayed from directions and thoroughly .wetted, ne'w, and the%riter isVware were first placed on the market in Australiawhere they were developed -in 1939. Since that time they have made considerable progress, and many improvements have been incorporated, including rotating overhead sprays in place of the original fixed type. Dips of the new type, which are covered by certain patent rights, rapidly became popular, as their efficiency was demonstrated. The dipping regulations were altered in several of the Australian States, to legalise their use, once the authorities were satisfied as

to their effectiveness, and from this stage onwards many hundreds were sold.

In 1941 it was decided to import one of these dips from Australia, to test under New Zealand conditions, but owing to shipping and supply difficulties it was not until the end .of 1944 that this dip actually arrived. In a way this was probably an advantage, as the model eventually sent included all the latest patented features and improvements. The dip was finally installed at the Ruakura Animal Research Station, near : Hamilton, but unfortunately owing to various unavoidable delays, including the railway strike, the work was not completed until almost the end of the dipping season this year. For this reason the trials carried out were not as extensive as was desirable, but as will be seen from the results the dip seems to have fulfilled the claims originally made for it.

Description of Dip

The general layout and design should be clear from the photographs, particularly the heading block and Fig. 3. Reduced to its simplest terms the layout consists of (1) a circular pen fitted with sliding entrance and exit gates where : the sheep are sprayed; (2) one, or preferably two draining pens, of orthodox design; ’ (3) a sump or reservoir to hold the dip and receive the run-off from the dipping and draining pens, via a perforated strainer; and (4) a powerdriven centrifugal pump to circulate the dip and force it through the nozzles.

Fig. 1 shows the circular concrete base of the pen, which is 14ft. inside diameter, with a raised' outer rim' a foot wide all round to retain the dip, giving an over-all diameter of, 16ft. This circular concrete floor has a slight fall or slope towards the far side (nearest the •’ woolshed) where there is an opening in the raised rim, which carries the surplus dip back via a channel to the main reservoir, where it is used again. This opening can be seen almost below the righthand edge of the sheets of iron. The pipe uprights which: form the frame can be seen, and several of the curved sheets of galvanised iron are already attached. The inner and outer rings of pipe on the floor, with their attached spray nozzles, can also be clearly seen. The overhead rotating spray arms are plainer in Fig. 2, which shows the completed enclosure. These two arms are attached to a central fitting, which allows them to rotate freely. There is a single central spray nozzle immediately below the ' rotating fitting, and a multiple spray nozzle at the end of each arm, which in . addition carries a special supplementary jet set at an angle which provides the propulsive effort

to turn the arms. , Alteration of the angle at which this jet is set alters the speed of rotation of the arms. ■ Fig. • 3 shows the general arrangement, with a 400-gallon mixing-tank in the foreground and the main sump or reservoir just showing in the left foreground behind the 40-gallon drum. The size of this reservoir is not critical, but depends to some extent on the number of sheep to be dipped. The one installed, shown in Fig. 4, comfortably holds 800 gallons, and was found quite satisfactory. Its dimensions are approximately 6ft. deep, sft. 6in. long, and sft. wide, but the shape does not matter much, and a circular reservoir would be just as effective. The capacity of this reservoir was checked by pouring into it measured quantities of water, 100 gallons at a time, and chiselling permanent marks into the concrete, to indicate the levels, which show up in Fig. 8. Fig. 4 shows the large flexible suction hose leading up to the centrifugal pump and the smaller delivery hose, which connects up with/ the pipe system leading to the dip. In the foreground is the by-pass channel which is. used to divert rainwater away when the dip is not in use. The long strainer can also be seen, which measures approximately Ift. in width by 6ft. in length. It is of galvanised steel, perforated with a great number

of small holes, about % 2 i n - i n diameter. Anything passing these holes is too small to block up any of the spray nozzles. Fig. 5 gives a better view of this strainer, and the concrete channel, which returns the used dip from the circular pen via the two pipes. The run-off from the draining pens • also enters at this point, which can be clearly seen in Fig. 6. When the dip is not in use two screwed plugs are inserted in the pipes ’to prevent rainwater entering the reservoir (which is normally covered over), and this water is diverted through the by-pass previously mentioned. When the dip is in use the by-pass is blocked with one of the screwed plugs. Fig. 6 also gives a good idea of the action of the strainer and how effectively it removes droppings, wool, and other foreign matter which normally contaminate the ordinary type of dip. From time to time this accumulation is swept down to the lower end of the strainer and removed with a square-mouthed shovel. Fig. 7 shows the completed pipework. The tap on the left is used for filling the reservoir and also the mixing-tank, by means of a hose. The branch pipe from the main supply leads to the pump via the stop-cock, and is used for priming , the pump when starting the day’s X operations. Although this branch pipe is not

strictly necessary, it is a great convenience and much easier than priming the pump with a bucket. The other tap on the extreme right is to allow air to escape while the pump is being primed. It serves , another useful purpose, in that before and after dipping plain water can be circulated through the system, and a hose attached to this tap while the pump is running provides a highpressure jet of water for cleaning down the draining pens, etc. The pump is covered by the low lean-to roof at the top of the picture. Fig. 8 shows another advantage of the system. By disconnecting the pressure hose and starting the pump the dip is circulated at high speed and pressure through the pump, and the powerful stream quickly and thoroughly mixes the dip as shown in the picture. A 5 h.p. electric motor in the wool-shed serves the dual purpose of driving the shearing plant and grinder, and also the pump, by means of the belt shown in Fig. 8, which comes out through a slot cut in the wall. When the pump is shut off while the pen is being filled or emptied the easiest way of doing this is by shifting the belt on to the loose pulley, and this is done by a long extended handle marked X in Fig. 8. Fig. 9 shows the two control valves. The one on the vertical pipe leads to the overhead sprays, and the horizontal one to the floor sprays. They may be turned on separately or together, as desired, and can both be shut off without stopping the pump. No damage results, as centrifugal pumps have this characteristic that although the outlet is completely shut off while the pump is running, pressure will not build up beyond a safe maximum. Fig. 10 shows the floor sprays in operation. It will be noticed that the outermost ring of sprays is set inwards at an angle, while the rest point vertically. . Very complete coverage is given by these sprays, and when the pen is properly filled with sheep they are thoroughly wetted from below, without much of the spray coming up high enough to get in their eyes and noses. As the nozzles project several inches above the floor, sheep do not tramp on them. In practice it was found most satisfactory to turn on the top and bottom sprays separately, as each set then received the full pressure and volume of dip. The sliding entrance gate, which is hung from grooved rollers running on the top ring of the framework, appears on the right of. the picture.

Fig. 11 shows the top sprays working, and really gives an inadequate idea of the big volume of liquid which issues from the multiple nozzle at each end of the spray arm. It will be noticed, however, that complete coverage

is obtained— cones of spray from the nozzles overlapping and also reaching the side ~ walls of the pen. The small suppiemen-' tary jets, one of which can be seen here, are set to give a relatively slow, speed of rotation to the overhead sprays of about five revolutions per minute. This means that each sheep receives only a momentary deluge from above as the spray passes, and there is an ample breathing gap before the next lot arrives. There is no possibility of drowning, as in any of the standard dips, and the behaviour of the sheep seems to indicate that they don’t object to the process to nearly the same degree.

Sheep don’t, as a rule, display their feelings by facial expression, but when the bottom sprays are first turned on and they get sprayed with “rain” from the ground they certainly look as near to bewilderment as sheep can get. Fig. 12 shows both sets of sprays operating at once, and the practice was adopted of turning on the bottom set again as well as the top set, just before the sheep went out, to give them a final all-over wetting. Fig. 13 shows the dip in action, with the overhead sprays working. The man at . the control valves is timing the spraying by his watch, and this practice was adopted throughout. A two-minute sandglass would be ideal for this purpose.

Fig. 14 shows the sheep leaving the dip. There is a spray nozzle on either side of the exit gate, which gives them a final squirt as they leave. Trials at Ruakura It was, mentioned previously that owing to unavoidable circumstances the tests with the dip had to be left almost to the end of the dipping season, and by this time the sheep on the property were carrying fully three months’ growth of wool. In a way, this was an advantage, as it gave the new dip an unusually severe test for wetting and penetrating powers. Unfortunately, or perhaps fortunately for the farm manager, the sheep were carrying very few parasites, and to' begin with it was impossible to demonstrate actual killing effects. It was realised that given a good . dipping material effective killing of parasites, would follow, provided thorough penetration and wetting were accomplished. At first sight it would seem easy by casual examination to determine if the sheep were wet to the skin, but in practice it was not an easy matter.. The moment the wool was parted to see how the dip had penetrated, fluid ran in from the outside of the fleece along the parting, and in any case the hands were wet, and it was difficult to tell, with any certainty, how much, if any, dip had reached the skin. For this reason a more critical test was devised, and a powdered watersoluble dyestuffmethyl violet—was

sprinkled sparingly right on the skin in a number of “strategic” positions. About a dozen positions were selected on each sheep, including such places as beneath the neck, under the brisket, under the belly and the crutch, in the “armpit,” and along the flanks, as well as on the topknot, the back of the neck, the back, etc. The wool was carefully parted in these positions, and a little of the dye, which is almost black in the dry state, carefully placed on the skin, where it adhered to the grease present. The wool was carefully rearranged, and the individual staples placed back in their original positions. When these sheep were dipped along with others there was no need to give them a close examination afterwards, for they showed large and obvious purple splotches in all the areas where the

dye had been placed, proving that the dip had reached the skin and the dye. Tests were made with different lengths of immersion, and it was found that two minutes on the bottom sprays, followed by two minutes on the top sprays, ' were ample to thoroughly wet crossbred sheep carrying up to 3J months’ growth of wool. Southdowns could be wetted in a minute on each set of sprays, i.e., two minutes in all. As the makers of the dip stress, thoroughness . rather than speed should be the objective, and even if the sheep were given half as long again, i.e., six minutes under the sprays, the method would still be quicker than many of our present dipping systems, quite apart from its other advantages. The . dip erected at Ruakura is called a “60-sheep model” by the Australian makers, but their

estimate is based on Merinos, and it was found during the trials that with the larger Romneys 50 would be a fairer average. The circular pen should be packed reasonably full for the best results, and the number , the pen actually held varied from 40 very large-framed Romneys to 85 lambs. Speed with Efficiency Approximately . 2,900 sheep and lambs on the. Ruakura farm were dipped, using a powder dip, and it was found that the dipping cycle averaged six minutes—a minute to fill the pen, four minutes under the sprays, and a minute to empty. This worked out at 500 thoroughly-dipped sheep per hour —a figure which could not be equalled by any of our present dipping installations, with the possible exception of some of the larger types of -swim dips, very few of which are being built nowadays. Although the general efficiency and particular advantages of the rotating power-spray dip had been demonstrated by the time the Ruakura sheep had been dipped, it was still felt that it would be desirable to try it out on sheep heavily infested with parasites. The local Inspector' of Stock, Mr. G. R. Mackintosh, was able to locate a pen of old ewes which were very heavily lice-infested and carrying, -in addition, a number of ticks. Fifty-nine of these were transported right to the dip by truck, to avoid the possibility of infesting the Ruakura sheep, and given the standard treatment of four minutes under the sprays—two bottom and two top—again using a powder dip. As these ewes were , very thin, there was no difficulty in getting them all into the dip at once, and after sufficient time in the draining pens they were carted back by truck to an isolation paddock. Mr. Mackintosh followed up the results of the dipping, and it was found that all lice had been killed within 30 hours of dipping, when the first inspection was made. At this stage some of the ticks had . been killed, but some were still alive. These ticks would either be freshlyhatched ones or more probably simply those which had not fed since dipping, for, unlike lice, ticks are not killed simply by contact with a standard dip, but only when they ingest it when feeding. (With a quick-acting dip containing derris, or similar rotenone-bearing substance, the ticks are killed in a similar manner to the lice, i.e., by contact with the dip). At the second inspection, 72. hours* after : dipping, all the remaining ticks were dead, so the ultimate results could be considered 100 per cent, effective. Spray Dipping Advantages In the revised edition of bulletin No. 181 on sheep dipping the advantages, claimed for the power-spray

system of dipping were set out. Now that the tests at Ruakura have been carried out, it is possible to give at first-hand experience under New Zealand conditions. ’ (a) The sheep are not 1 knocked about; consequently losses are kept down to the bare minimum’. Even low-conditioned sheep and ewes close to lambing could be safely dipped if necessary. Many of the usual risks associated , with dipping valuable stud rams are eliminated. (b) As the sheep received no rough treatment or sudden plunge into the dip, they offered little objection to •dipping, so the amount of labour required was greatly reduced, and nobody even “got a sweat up.” A man and a boy can easily work the dip, and even one man with good ■dogs would not find it difficult. The sheep enter easily, as the exit gate (which is directly opposite the entrance—see Fig. 13) is of cyclone .wire, and the sheep in the draining pens act as decoys, being in full view of

those entering. Fig. 14 shows the leisurely fashion in which the sheep are leaving the dip; in fact, this might almost be classed as a disadvantage, as they have to be chased out.

(c) Dipping is rapid compared with present methods; 500 sheep per hour were dipped without difficulty. Four sizes of this type of spray dip were manufactured in Australia, rated at 30, 60, 90, and 120 sheep capacity. The model tested is a 60-sheep one, so with the largest model it would be fair to assume that upwards of 1,000 sheep per hour could be dipped.

(d) Economy in the use of dipping fluid, which can be used to a much lower level than with any of the

standard types of dips. It was found that dipping could be continued till just over 100 gallons were left. With an improved design of reservoir with a sloping floor, it is probable that dipping could continue even longer before the ~ foot-valve was expose , thus allowing the pump to suck air. , (e) As the design, necessitates and incorporates efficient screening, it removes much foreign matter from the dip (see Fig. 6), and reduces the risk of dip stain to a minimum. It can any type of dip equally we , ana , the continual circulation is a £ rea t advantage with powder dips, as it keeps them thorough y mixed an t he powder particles in suspension. already mentioned, the pump can use( ? as Y eI J convenient and thorough, method of carrying out the initiai mixing o the dip (see ig. on - (f) The first cost is no higher than that of a standard type of dip of comparable capacity. The approximate landed cost in New Zealand of the framework, entrance and exit gates,,

galvanised iron, all piping hoses and valves, and centrifugal pump, would be in the vicinity of £110 at present, t o this must be added the cost of the concrete work and fences round drann g pens, but these costs var so much according to circumstanceS) g. ( the availability of shingle an( san d, whether farm labour is use( i e t c< ’ that no useful estimate can be given ’f or this part of the job. No doubt those interested could make their own estimates on the following basis:—Area of concrete in floor of c ii a r pen, approximately 200 sq. ft., all j east 4in . thick and preferably reinforced. The rim, which is 1ft. wide , j s included in the above area, bu |. concrete iH be at least 6in. thick, giving a total of about 75 cubic fee t Area of concrete in draining p ens , ap proximately 350 sq. ft., at least 3in. thick, and preferably reinforced, plus a raised rim all round, requiring about 92 cubic feet in all. The reservoir is of the dimensions given above, and has reinforced walls 6in. thick.

The total quantity of concrete for this will be , approximately 90 cubic feet, plus, say, another 10 cubic feet of concrete for the gutter and its raised rim. The total quantity of concrete required for the whole installation is, therefore, about -267 cubic feet, or very nearly 10 cubic yards. (g) This type of dip would seem to be ideally suited for installation at public saleyards, or as a community dip for the use of a number of small flock-owners, on account of its speed of operation and the fact that each user could put in just enough of the dip of his own choice to suit his requirements, and would have the great advantage of starting off with clean dip. This principle applies also to the use of the dip for large flocks, where the. .reservoir is allowed to become almost empty after dipping, say 1.500 sheep, and is then quickly replenished with fresh dip already prepared in the mixing-tank. This would be in marked contrast to present practice with many large flocks, where thousands of sheep go through the dipping bath, which is topped up from time to time and ultimately resembles pea-soup in consistency, and liquid manure in colour and smell. Disadvantages The tests at Ruakura did not reveal any serious disadvantages, and these should have been evident after dipping 2,900 sheep. It is only fair, however, to take the - following into account: —

(a) Some form of motive power is necessary to drive the pump. On many properties this would present no difficulty where a suitable engine or electric motor was already available, or the power take-off from a tractor, could be used. The difficulty would arise only where the existing engine or motor was of insufficient power to drive the pump, as a minimum of 5 h.p. is required for this type of dip. The small 30-sheep model requires only 4' h.p., but the large 120 model required about 12 h.p. for the pump. (b) There is, of course, the cost of oil fuel or electricity to be considered, but as , dipping even a large flock by this method- is relatively quick, the cost will not be a large item, and is offset to a considerable extent by economies in other directions. Discussion It would appear from the evidence of the trials that power-spray dipping has much to recommend it, particularly for larger flocks. For a single small flock the original outlay might be considered rather heavy, but if the flock-owner- arranged to dip for several of his neighbours,, the installation would certainly be justified, and with a reasonable charge for this service the first cost would be liquidated in a few years. In Australia well over a thousand of these power-spray dips had been installed by early 1944, and the makers still

had many orders waiting. At the moment none of these dips is obtain--1 able for export to New Zealand, but it is probable that a limited number may be available in the course of the next six months. Under the terms of ' the present Stock Act this type of . dip ' does not strictly comply with the- legal definition of dipping, which means “plunged or immersed.” The results of the Ruakura trials have been sufficiently convincing, however, to warrant the general use of the method, and it is unlikely that any action would be taken against anyone using the power-spray system before a suitable amendment is introduced to legalise the new method. It may be of interest to anyone considering the installation of a powerspray dip to replace any of the standard types to note that a good deal of the existing installation can be salvaged if of suitable type and in good condition. The original dip (or a portion of it in the case of a longswim) can be used as the reservoir, and the existing draining pens can frequently be incorporated in the new layout. Where the original draining pens are very large one of them can be used as the foundation for the circular pen and the other kept as it is,, or. subdivided to continue in use as a draining ' pen. Where an adaptation of this sort is possible considerablesaving can be made. Acknowledgments Thanks are due to the Public Works; Department’s staff in Hamilton for assisting in building and testing the dip. All photographs are by the author.