The Pamphlet Collection of Sir Robert Stout: Volume 29
It is very important that the yards should be so planned that they are easily worked, and of such a height and strength as will render it impossible for any of the sheep to break away before dipping.
Duration and Heat of Bath.—When the fleece is short, the bath should be administered at a temperature of 120 degrees Fahrenheit in the winter, and at 110 degrees in the summer, at which it should be the endeavour to keep it throughout the dipping (the thermometer being tried every other dip full); and the sheep should be allowed to remain in the dip from 60 to 80 seconds, and as much longer as they can stand it; for with short fleeces they dry almost immediately after being put into the draining yards, and if the bath was not severe both as to temperature and duration, they would stand less chance of being cured than if they were in full fleece or nearly so, whereby they take out and retain" more of the mixture. As the mixture cools, it will be necessary to keep the sheep longer in it, say from one-and-a-half to page 164 two minutes altogether, but in no case should the temperature be allowed to fall below 100 degrees. "When the fleece is long, the heat of the mixture should be maintained at a temperature of from 100 to 110 degrees in the summer, and from 105 to 115 degrees in the winter, and the sheep should be kept in the dip nearly, though not quite, as long as when the fleece is short. These periods are given by way of a guide for the purpose of timeing the process, which ought to be carefully attended to, but it will be for the person in charge to see that while the sheep are thoroughly saturated and kept as long in the dip as they can stand it, none of them are detained till they are in danger of being drowned.
While it only takes 30 seconds to kill the scab insect with the mixture at 90 degrees, it will live for 10 or 12 minutes in the same mixture at 45 to 50 degrees. It will thus be seen how very essential a high temperature is to the success of the dipping, and as a case in point, it may be stated that an owner at a long distance from Sydney, ran short of materials, and effected a thorough cure with half the ordinary strength of ingredients, by keeping the temperature of the bath at fully 130 degrees. There is little doubt, too, if we are to judge by the experience of the process of incubation of eggs by artificial heat, but that the high temperature here given destroys many of the eggs of the insect, which, at the time of the dipping, are still in the skin, and not near maturity. Indeed, if the destruction of the acari and their eggs on the sheep were all that was necessary to a permanent cure, there are good grounds for supposing that this might be effected by the high temperatures sometimes attained in the Turkish bath, without the use of any medicaments.
Second Dipping.—One dipping if carefully and thoroughly performed as directed, is said, in some hands, to have made a cure; but the practice ought always to be to dip twice at an interval of from ten to twenty days to make the matter a certainty; for not only will any sheep, which may have been imperfectly dressed at the first dipping be thus certain of being thoroughly so at the second, but all the acari which were in an embryo state in the skin at the first dipping and thus escaped destruction, would, by the time the second was carried out have reached maturity, and would be destroyed.
Third Dipping.—This may be necessary at times, when any doubt whatever is cast upon the efficacy of the dressing administered. Thus it is most essential, when sheep are exposed to a fall of rain, or allowed to go into water shortly after dressing, and especially so when their fleeces are short.
Lambs Dipped.—Where lambs are dropped about, or shortly after the second dressing given to their infected mothers, they should be properly dipped as soon as they are able to stand the operation, for by running on the infected ground, they would otherwise stand a good chance of becoming diseased.page 165
Rams Dipped.—As rams are bad swimmers, care should be taken that they are not allowed to leave the dip until they are thoroughly dressed, which their heavy fleeces and twisted horns render somewhat difficult. They should, of course, be put through by themselves, and no more than seven or eight of them should be put into the dip at once, while every part of their heads and necks should be thoroughly saturated.
Dipping Stragglers.—Although it should happen, as it is to be hoped it will, that the two dippings effect a cure, the use of the dip will not then cease, for in or near a district where scab has existed, it ought to be an established rule with the sheep owner, for at least twelve months after the last cure of infection in or near his neighbourhood, that every sheep which has strayed off his run, or has mixed with those belonging to other runs, should on recovery be carefully dipped either once or twice, according to the character of the ground on which it was found, or of the sheep with which it had mixed.