Careless Dipping Is A Waste Of Money Uses of Various Types of Dips

New Zealand Journal of Agriculture, Volume 60, Issue 2, 15 February 1940, Page 101

Careless Dipping Is A Waste Of Money Uses of Various Types of Dips

- By -

J. E. DUNCAN,

Wool Instructor, Livestock Division, Wellington.

IN a short article of this nature it is not intended to deal at any length with the history of dipping, but the illustrations reproduced will no doubt be of interest in view of the great contrast they represent compared with modern methods. Apparently the art of “salving” can be traced right back to the earliest days of shepherding, and is recorded in Britain as far back as A.D. 1280. In those early days tar was rubbed into the fleece as a remedy 'for scab, but .during the nineteenth century flockmasters began to compound it with other substances, such as grease and rancid butter, in an endeavour to overcome the inevitable staining of the wool - which took place. Salving was undoubtedly a slow and back-breaking job, and the early methods of dipping (Fig. 2) which began to replace it at the beginning of the nineteenth century were little better. It was really colonisation which ushered in the process of dipping, as we know it today, for necessity again proved to be the mother of invention when the early pastoralists were faced with the necessity of treating their ever-increasing flocks in an expeditious manner so were evolved the swim dips and draining pens and other equipment with which every sheep farmer is now all too familiar.

Does Dipping Pay ? In New Zealand the sheep farmer is not left to decide whether dipping is necessary or desirable, as he is required to dip by law. For this reason a small minority of the farming community still regard the annual dipping as a necessary evil and something to be got over as quickly and with as little trouble as possible. There is more than a grain of truth in this view, provided the emphasis is placed on the word “necessary,” and provided the speed with which the job is disposed of does not interfere with its efficiency. There is no doubt that poor workmanship in dipping sheep is a bad investment, because if it is done in a slipshod manner the money spent on materials and labour is largely wasted, as the sheep receive no lastbenefit.

The conditions which go to make for successful dipping will be fully discussed in a subsequent article, but it will not be out of place here to mention the damage done by parasites in the fleece and something about the particular parasites which cause it. In New Zealand we are fortunate in not having to cope with scab, which has proved such a scourge in some, of the other sheep-raising countries. In 1881 it was estimated that there were 700,000 sheep suffering from this trouble in New Zealand, but by 1893 scab was finally eliminated by a rigorously enforced policy of control, which included shooting some of the affected sheep where they were located in inaccesible areas. Today we have only lice and keds to cope with, although they can be quite bad enough. Damage by Parasites Although cases of sheep actually dying from the attacks of these parasites must be very rare indeed, the amount of damage which they cause is nevertheless great, anjd may be summed up as follows: — (1) Bad infestation with keds (ticks) causes permanent staining of the fleece (due to their excreta) and consequent loss in value of wool. .(2) Instead of devoting their whole time to growing wool and mutton, parasite-infested sheep devote much of their time to rubbing,

scratching, and biting themselves so that they thrive badly and damage their fleeces. (See Fig. 3). Lice cause an intolerable amount of irritation, and although it is a moot point whether they actually bite through the wool fibres, they cause much indirect loss and . spoilage of ' the fleece, due to the sheep rubbing against fence posts, etc. Keds, although they do not appear to cause the sheep the same amount of irritation, suck . quite appreciable quantities of blood if present in large numbers. (3) An indirect source of loss is that sheep weakened by the ravages of parasites fall a prey to other diseases which normally they could resist; nor can ewes which are thriving badly be expected to produce robust lambs. (4) Although it is a punishable offence to offer lousy sheep for sale in a public yard, there are nevertheless cases where this happens and clean sheep become infested, with consequent loss to their owners. (5) As dipping does not improve the .fleeces of clean sheep, the total

cost of the operation must be debited to lice and keds. No accurate cost of dipping our flocks each year is available, but the cost of dipping materials alone approaches £150,000 per annum, and when the cost of providing labour, plant, etc., is all taken into account the total cost must be very much higher. It is equally impossible to estimate the cost of the damage done by the parasites or what it would amount to if they were left uncontrolled, but one thing is self-evident careless dipping is sheer waste of money. Parasites Concerned The parasties which give us trouble in New. Zealand are several species of lice and the sheep ked, frequently and erroneously referred to as the sheep “tick.” The most common species of lice familiar to most sheep farmers is commonly called the red-headed sheep louse (scientific name, Trichodectes sphaerocephalus or T. ovis) , and is a very small wingless insect (about one millimetre or one twenty-fifth of an

inch in length) which, because of its pale colour, is not always easy to see among the wool. It is ilustrated in Fig. 4, and receives its common name because of the head and thorax being a rusty reddish colour. Its mouth-parts are designed for feeding on scales and other debris on the surface of the skin, and at no time does it suck blood. It is very active in its habits, and has great tenacity of life, which, coupled with its ability to breed very rapidly, enables it to infest a clean flock in a very short time, for although it never leaves its host at any other time, it can transfer itself very rapidly when sheep are in contact. For example, a single lousy ram can infest a whole flock in an incredibly short time. 1 The eggs, or “nits,” which are of a dirty white colour, are attached to the wool by a sticky secretion. The young lice which hatch from them are very similar to the parents except in size, and moult several times before reaching maturity. The length of the life cycle varies considerably according to

conditions, but it is probably about three weeks under the usual conditions. The symptoms of lousiness are rubbing, biting, scratching, and general uneasiness. The lice congregate near the skin, mainly on the upper parts of the neck, shoulders, back, and thighs; in other words, they are thickest where the sheep has the greatest difficulty in reaching them, although in bad cases they may be spread all over the body. Other Species Two other species of louse have occasionally been found in New Zealand, namely, the face-louse (.Linognathus ovillus) and the leg-louse (Haematopinus pedalis). The former is extremely rare, and the 'latter, although found more often, is of little economic importance, as it causes the sheep very little inconvenience and is easily controlled by ordinary dipping. It is about twice the size of the ordinary redheaded louse (see Fig. 5), and is confined almost entirely to the . sheeps’ legs, where, being a blood-sucker, it remains relatively stationary. The ked (Melophagus ovinus) is not a true tick, but an insect, a degenerate fly which has lost its wings and so become a permanent parasite on the sheep. It is shown in Fig. 6, but its rusty brown appearance must be familiar to all sheep men. Its mouth-parts are entirely adapted for sucking blood, yet, strangely enough, it seems to cause the sheep a good deal less irritation 'than the much smaller biting lice. . Lays No Eggs Unlike most insects, the female ked lays no eggs. It retains the eggs with-

in her body until each one is deposited as a fully-grown larva, which changes into the familiar pupa almost immediately after it has been attached to the wool by a sticky secretion. This smooth, shiny-brown, barrel-shaped pupa is about one-eighth of an inch long, and the colour of an apple pip. When it hatches in due course it gives rise to the adult ked, < which begins to feed almost immediately and, after mating, soon completes its life cycle once more. Here again there seems to be considerable variation in this period according to conditions,

but it is approximately correct to place it between three and four weeks. The habits of the ked and the symptoms of its infestation are in many ways similar to those described for the red-headed sheep, louse. It, too, never purposely leaves its host except to transfer to other sheep when they are in contact, which it does very rapidly, and it is most numerous in similar parts of the body to the lice, but, being darker in colour and much larger, it is easier to see. On warm days the keds sometimes! crawl up to the surface of the fleece. Infestation Clean flocks of sheep frequently become infested with lice and/or keds in what appears to be a most mysterious fashion. Men or dogs (although not. the normal hosts) may accidentally ’ carry these parasites. Hence the wisdom of dipping all dogs at the same time as the sheep. Any goats on the property should also be dipped. Sheep rubbing against a boundary fence may pick up parasites from bits of wool rubbed off by the neighbour’s sheep, and stragglers getting through fences or sheep coming from a public saleyard are other potential sources of infestation. 1 Other sources of re-infestation are:— The practice of dipping rams, stud sheep, lambs, etc., at a different period from the dipping of the general flock,

failure to dip lambs and ration sheep, allowing neighbours, to dip in your bath, travelling sheep along, roads and stock • routes, and the proximity of these to boundary fences. It is interesting' to note that the openfleeced Lincoln type of sheep is most easily and soonest re-infested, while, conversely, dense-woolled sheep, such as Merinos, are much more difficult to re-infest, presumably because the parasites find difficulty in moving between the closely-spaced wool fibres. Dipping Materials Although there is not nearly such 'a variety of dipping preparations on the market in New Zealand as in some other sheep-raising countries, there are nevertheless enough different makes and types available to cause the novice to wonder just which one he ought to use. The following classification may be of some help in this respect. The six main groups of dipping substances used in various parts of the world for dipping sheep are: —

(1) Arsenical. (2) Cresol. (3) Coal tar. (4) Lime-sulphur. (5) Nicotine. (6) Various combinations of the above. In New Zealand, because of the absence of scab, we are not concerned with class (5), and class (4) is seldom used nowadays because of its harsh effects on the wool and poor lasting qualities. Very few, if any, farmers in New Zealand now attempt to make their own dipping materials, which is really false economy in any case, so that only the proprietary dips at present on the market have to be considered. These may be broadly divided into two main groups: — A. Poisonous dips. B. Non-poisonous dips.' It should be noted, however, that this classification is an arbitrary one, as there are on , the market a few dips which combine the properties of both groups, and in any case the term “nonpoisonous” is really a misnomer, for although these dips are relatively a good deal less poisonous than those in group A, they nevertheless contain poisonous ingredients which, under certain conditions, can be dangerous. Their mode of action on the parasites is, however, different, and this will be mentioned presently.

A. —Poisonous Dips. • The basic ingredient used in all poisonous dips is the powerful poison arsenic, which may be present in various forms, such as arsenious oxide, sodium arsenite, arsenic pentoxide, and various sulphides of arsenic. Sulphur may also be present in the free state as well as combined with the arsenic, and usually these chemicals are associated with other ingredients, such as coal tar oils (namely, . cresols and phenols), Derris resin, soft soap, etc., according to the particular type of dip which they constitute. Poisonous dips may be further subdivided according to type into three groups, viz.:— (1) Powders. (2) Pastes. (3) Fluids. (1) The poisonous powder dips enjoy the greatest popularity of any type on the market at present, and most firms nowadays sell a quick-acting (Q.A.) type. These, in addition to sulphur and arsenic compounds, contain a Derris preparation, the active poisonous principle of which is known as “rotenone.” Space does not permit any allusion to the interesting history of this substance. Suffice it to say that, while it is very toxic to all cold-blooded creatures (for example, its use as “Derridust” against garden pests), it is harmless to warm-blooded animals. Although soft water is preferable for use with all dips, the powder dips will work fairly satisfactorily even with hard water, but they must be thoroughly mixed and kept agitated throughout the dipping. When properly used they have considerable lasting power in the fleece.

(2) Poisonous pastes are also offered by quite a number of manufacturers, and of late years have become increasingly popular. They contain similar ingredients to the powders, and may also be of the quick-acting type, but the ingredients are compounded with soft soaps and certain oils so that they can be completely emulsified with water and do not require constant agitation once properly mixed, but in most cases it is essential that if the water is hard it be properly softened before use. The makers of the better class of these dips claim that by virtue of certain of their oily ingredients they have good lasting power in the fleece, and this seems to be borne out by results in practice.' (3) Poisonous fluid dips have little lasting power in the fleece, being much simpler in composition than those already mentioned. They have little to recommend them except their cheapness, and are largely being displaced by other types today. B. —Non-poisonous Dips The basic ingredients of non-poison-ous dips are coal tar products obtained as by-products of gas manufacture, and are chiefly cresol (also known as cresylic acid or “liquid carbolic”), and other tar acids and tar oils. These fluids are not themselves soluble in water, but by adding emulsifying agents, such as a vegetable oil soap, I•_ „ -. , . « drifts .

it is possible to get them dispersed into extremely fine globules (like the butterfat globules in milk), which form a stable emulsion in water, and which do not separate out on standing. Hard .water interferes with this emulsifying action, and there is a danger of the concentrated cresol, etc., separating out and floating as a layer on top of the dip, where it can be very harmful, or even fatal, to the sheep. ■ - When only hard water is available it is necessary to soften it by adding from 21b. to 101 b of washing soda for each 100, gallons of water. If there is any doubt about the matter it can easily be settled by mixing the dip in miniature in a clean glass jar, using the correct proportions. If, after standing for an hour, an oily mass of globules appears either at the top or the bottom of the liquid either that water should be avoided or suitably softened before use. The non-poisonous dips can be subdivided into two groups only: — (1) Non-poisonous pastes. • (2) Non-poisonous fluids. (1) The non-poisonous pastes may, in addition, contain the quick-acting ingredient Derris, which considerably enhances their value. Some makers claim to include special ingredients which make them miscible with hard water, but too much reliance should not be placed on these claims. They are quite effective against parasites, but have no lasting power in the fleece to protect against re-infestation. Whatever popularity is enjoyed by certain types is due in no small measure to the vegetable oils which they contain, leaving the fleece in very attractive condition. (2) The non-poisonous fluids are effective only at the time of use, and have no lasting power. Their popularity is not great, and is waning. Uses of Various Types ' The various dips will be considered in the same order in which they have already been mentioned. For the main dipping, where a thorough kill of parasites and protection against re-infesta-tion is required, only the poisonous dips are suitable, either in powder or paste form. Poisonous fluids have no lasting power, except in a prolonged spell of dry weather, and therefore cannot be considered suitable. At present the majority of users appear to prefer the powder dips, but certain of the paste forms are gaining rapidly in popularity.

It would be out of place here to enter into any further discussion on the respective merits of these types, as

they each have their advantages and disadvantages, but there are few farmers who will not have had these

eloquently pointed out to them by representatives of the various dip-manu-facturing firms. The only safe guide is to make a practice of dealing only with reputable and well-known firms, and if a dip is found to give thorough satisfaction year after year there is little point in changing from it. Both the non-poisonous types may be said to be designed for temporary dipping, and cannot be considered suitable for the main dipping. The pastes are usually high in cost, so that where it is desired to dip oft shears as a protection against infection of cuts or for other temporary dipping, such as lambs about to be fattened on rape, or dipping prior to shearing, it will usually suffice to use a non-poisonous fluid. It is not intended to mention here any of the special types, such as bloom dips, which are marketed to fulfil a breeder’s fad. As dips they have no special advantages, and it is a moot point whether anyone is ever deceived by the artificial colouring of the wool. From the wool point of view, possibly it does no harm, but certainly no good. Action of Dips Dips kill the parasites by acting on them in one or more of the following ways: — (1) As stomach poisons. (2) As respiratory poisons, entering through the spiracles (breathing pores). (3) By absorption through the cuticle (outside “shell” of insect). (4) By suffocation by closing the spiracles. A. The poisonous types of dips act chiefly as stomach poisons, although absorption through the cuticle and spiracles probably also occurs to a considerable extent. B. The non-poisonous dips kill mainly by suffocation, and are sometimes referred to as contact poisons. Derris induces immediate paralysis on contact, and ultimate death. The oils

tend to stop up the spiracles, and also enter the body by this route. With a slow-acting (the standard type which does not include Derris) powder dip, live parasites may be found the day after dipping, but this should not be taken as proof that the dip is ineffective, because these parasites will ultimately be poisoned when they feed. In the case of the non-poisonous dips (which depend on coal tar products for their action) and dips containing Derris, all parasites should be killed in 24 hours or less. No dip has yet been devised which will sterilise all the “eggs” of both lice and keds, so that ultimately some of these will hatch out. For this reason -quite apart from the possibility of re-infestation—a good dip requires to give protection for a month after dip- . ping, and to have a reasonable prospect of attaining this the sheep must carry a fair growth of wool at the time of dipping which will hold, and continue to hold, the poisonous ingredients. When To Dip The time of dipping is largely governed by the Stock Act, which stipulates‘that, with certain exceptions (set out in detail in the Act) , all longwool and crossbred sheep shall be dipped each year in the North Island between January 1 and March 31, and elsewhere than in the North Island between January 1 and April 30. However, within the stipulated period there are a number of factors which govern the actual date of dipping: (1) The Date of Shearing.— Nearly all dip manufacturers recommend dipping merinos at least four (preferably six) weeks after shearing, and for crossbreds not sooner than two months after shearing. The reason for allowing these lengths of time is to allow sufficient wool to grow to carry out a good quantity of dip. The Merino fleece, being so much denser, does not need the same length to hold enough dip, and 1 because of its very greasy nature too much growth of wool could prevent proper penetration of the dip right down to the skin. Although the practice is rarer in this country than in Australia, some owners dip straight off the shears in a carbolic (non-poisonous) dip as a protection against infection of shear cuts, and then later at the proper time give a second dipping in a poisonous dip. Dipping sheep with

open wounds on them in a wash that has been allowed to become dirty is worse than useless. It has been proved that bacteria can live in a dirty dip, particularly of the arsenical (poisonous) type, and infect sheep suffering from cuts, abrasions, or dog bites with blood poisoning, which rapidly proves fatal. (2) Climate and Altitude. These factors will also have to be considered to ensure suitable weather for dipping. (3) Shelter.— The shelter available has its influence, as excessively hot sunshine or cold winds should be avoided. (4) Neighbours. possible, a farmer should dip about the same time as his neighbours to lessen the risk of reinfestation. (5) Public — Where the farmer uses a public dip or a neighbour’s dip, he will usually have to take his turn, and cannot then always dip at the most suitable time. (6) Water Supply. drought may make dipping temporarily impossible, and there are certain provisions in the Stock Act allowing an extension of . time to cover this contingency.

»3eii— Illi—— till- .1111— mi——nu— Illi——||||——llli——llli——llli— I i I | This is the first of a series of I j three articles on dips and 1 | dipping. The second one will 1 = deal with the actual operation | 1 of dipping, and the third with j I the choice and construction of j I suitable plant. They will later | j be published together in bul- § j letin form, including plans and 1 j- diagrams of the various types ! [ of dips. j —mi— mi— mi—mi—mi—mi——mi—mi——mi—