MORTALITY AMONG YOUNG FAT LAMBS.

New Zealand Journal of Agriculture, Volume XXXVI, Issue 3, 20 March 1928, Page 149

MORTALITY AMONG YOUNG FAT LAMBS.

INVESTIGATIONS IN SEASON 1927.

D. A. Gill,

M.R.C.V.S., D.V.S.M., Assistant Officer in Charge, WaJlaceville Veterinary Laboratory.

Trials of Preventive Measures. In addition to continuing the. research commenced in 1926 in Central Otago— which an account was given in the Journal for April, 1927, under the title of “‘Pulpy Kidney’ Disease of Lambs” — experiments were carried out during the past season in that district regarding the efficacy of the various preventive measures adopted for the purpose of combating the loss from this trouble. In spite of every effort to have these trials conducted under adequately controlled conditions, when it came to the point the controls were not as thorough as they might have been, owing to unavoidable circumstances connected, with the season, &c. However, the results obtained are considered more reliable than any hitherto published in this connection, and it is felt that it will be useful to farmers who suffer losses of lambs to give an outline of the various experiments.

(l) OVERSTOCKING FROM LAMBING ONWARDS.

This was tried on a farm where heavy losses had been experienced for several years past. A paddock of 120 acres, where numerous deaths occurred last season, was partly ploughed and fenced off, so that 40 acres of the area was left in grass (very old pasture,' mainly couch with a little rye-grass, suckling-clover, cocksfoot, and fescue), and eighty ewes were placed on the 40 acres about a fortnight before lambing. Deaths commenced here on 9th October. About the 20th the stock in the paddock was increased to 100 ewes and 116 lambs, although the older ewes were going back in condition. This paddock showed the highest death-rate on the farm--approximately 10 per cent., compared with an average death-rate in the other paddocks of about 4I per cent.

Another somewhat similar experience may be mentioned. A farmer who lost heavily in the preceding year was visited early this season when deaths were just commencing. As an experiment he put two

mobs of ewes and lambs into one paddock. A further visit later in the season found this paddock grazed very close indeed, with the ewes and lambs in anything but prime condition, and yet there had been a considerably heavier loss in this overstocked paddock than in the others.

Apart from its not checking the death-rate, this practice is bad, because it certainly throws the ewes back in condition even if the lambs are not markedly affected. If persisted in, it means a considerable loss on the wool, besides greatly prejudicing the chance of getting the usual percentage of lambs away in the first draft to the freezing-works.

(2) EFFECT OF MARKING.*

Contrary to experience in many parts of New Zealand, particularly the North Island, marking appeared to have little, if any, beneficial effect as far as the mortality in Central Otago was concerned. In several instances deaths were few up to marking, and then during the succeeding few days were greatly increased. Several such instances were carefully investigated, and, save in a few cases, the deaths following the marking could not be attributed to blood-poisoning or other effects of the operation. In other cases, where marking was undertaken when a high rate of mortality was occurring,, there was a check in the losses, but only for three or four days, and it seems very probable that this was due rather to the exercise, yarding, &c., entailed by marking than to the operation itself.

(3) EFFECT OF EXERCISE.

Only one controlled experiment was made, but several farmers tried it in a more or less haphazard fashion. The controlled trial gave the following results : Exercised mobs (totalling from 800 to 1,000), average death-rate 2| per cent. ; unexercised controlled mob of ninety lambs, loss eight, or approximately 9 per cent.

In another case the whole flock was exercised except the two-tooths, and here the death-rate was —Exercised mobs, average loss approximately 3 per cent. ; unexercised two-tooths, average loss approximately 6 per cent.

A third farmer drafted out his twins and placed them on rich feed —low-lying rye-grass and clover paddock, thence to rye and lucerne, and finally to rye and cow-grass. He did not exercise these lambs. His singles were on terraces showing good feed—rye-grass, clover, and some cocksfoot—but not as good as that given to the twins —and in addition they were exercised daily. The difference in the death-rate of the two mobs is certainly striking in view of the popular opinion than twins are more or less immune from this trouble. It was as follows : Among singles, exercised, approximately 4 per cent. ; among twins, unexercised, approximately 10 per cent.

The manner in which exercise was carried out in these cases was neither consistent nor particularly thorough, but is the best most farmers can do at such a busy time of the year. It consists of driving sheep about in the paddock with the dogs for a varying time each day. Some days a good half-hour might be devoted to a particular mob, whereas the next day only sufficient time might be available to rush

them a few hundred yards or so. In spite of this, however, the cases quoted may be taken as fair examples, and they certainly show a saving in the losses.

(4) EFFECT OF YARDING.

Two different methods of yarding were tried. One proved of little if any benefit, whereas the other seems to offer the best means of prevention available.

y ar ding N ightly.

From the time the lambs were a week to ten days old the mob was yarded up into a corner of the paddock (fenced off with standards and wire netting, with a big wing thrown out for driving purposes) every afternoon about 5 o’clock, and let out again about 8 or 9 o’clock the following morning. Details of the two cases in which this method was carried out are as follows :—

(a) Loss among yarded mob, 7-4 per cent. ; losses among other lambs (excluding twins and two-tooths), approximately 3 per cent. This was the only controlled experiment of its type, and obviously in this single instance the large amount of extra work was worse than useless.

(&) In the second case there was not a proper control. Out of about forty-five early lambs, eight were lost from this disease, and judging by this a heavy death-rate among the main lot of lambs was anticipated. Advice was given to draft off the' twins and to yard the single lambs each night as described. This was done, and as the twins were on good feed and no preventive measures were adopted they were, in a. sense, controls. The losses were—among singles, yarded nightly, i-8 per cent.; among twins, not yarded, 1-9 per cent. In previous years this farmer had had about the same loss among his twins as this season, but a much heavier mortality among his singles, so that he may have benefited more in reality than is shown by the figures. This method entails a very great deal of extra work, especially when several paddocks have to be dealt with, and, on the face of it, appears of very little use as a preventive.

Yarding for Twenty-four Hours every Seven Days.

The method of yarding was the same as that described for nightly yarding. Once a week the mob was yarded up in the morning and left in till the same time the following day. Where this method was adopted it gave very good results. One farmer, who gave it a tentative trial last season on his own initiative, consented to test it thoroughly this season with an adequate control. His results, which speak for themselves, were as follows : A mob of 434 lambs was divided into two equal lots ; one lot was yarded for twenty-four hours every seventh day; the other was not yarded. The loss in the yarded lot was J- per cent; the loss in the unyarded lot was 3 per cent. Out of 160 twin lambs (80 pairs) eight died. He then yarded the lambs for twenty-four hours ; one was found dead in the yard, and none died afterwards. Out of some 1,900 lambs his total loss was under thirty, and of this total fifteen died out of 377 that were not being yarded. Thus the average deathrate over the whole flock was less than 3 per cent. The death-rate among the yarded lambs approximated 1 per cent., and that among

the unyarded lambs was approximately 4 per cent. Reckoning a lamb’s value at the moderate figure of £1, a saving of 3 per cent, of lambs in this mob of . 1,900 was equivalent to £57. It is a note-; worthy fact that the death among the yarded lambs occurred either in the yards or just before yarding. It would appear, from this that possibly an interval of seven days is too long, and that about five days would be better.

Another farmer had nine lambs die in a certain paddock. He was then persuaded to yard the mo for twenty -four hours; no more deaths occurred here for eight days, when one was found sick and died later; the lambs were then yarded again, and no more died. In another paddock where a heavy death-rate occurred last season three lambs died; the mob was. then placed on a ploughed paddock for twenty-four hours, after -which the deaths stopped.

One more case is worth quoting. A farmer who had lost sixteen lambs out of 270-odd was of opinion that nothing would check the deathrate ; but as he happened to have a ploughed paddock conveniently placed he agreed to put the whole mob there for twenty-four hours. Only two more died after this was done.

SUMMARY.

The results of this season’s experiments in prevention of the disease mav be summarized as follows :—

(1) Overstocking paddocks from lambing onwards is useless, and apt to be actually harmful. ' ■

(2) So far as Central Otago, at any rate, is concerned, the check in the death-rate caused by marking is negligible ; therefore this operation may be regarded as quite inadequate as a preventive measure.

(3) Exercise is certainly beneficial.

(4) Yarding nightly is cumbersome, and appears also to be of very doubtful benefit, besides giving the lambs a check.

(5) Yarding for twenty-four hours once a week has given very good results, with the additional advantage that it is the easiest method of all those tried. It is practicable on almost every farm where the losses occur, and a great point in its favour is that it gives neither ewes nor lambs any noticeable check. It is for the farmer himself to judge whether an interval of seven days or a shorter one of, say, five days does most good in his own particular case.

There seems to be a feeling amongst farmers who suffer from this mortality that preventive measures mean taking a great deal of trouble, and that it is very doubtful if benefit is derived. The foregoing outline shows definitely that a considerable measure of relief is obtainable. The principal difficulty is that on most farms the ewes are not drafted into mobs as they lamb. It is but rarely that the size of the paddocks precludes this. In the great majority of cases it is a practice which might easily be undertaken, and the comparatively few farmers who do it state that with a little foresight and organization it is quite simple and takes very little time, besides making subsequent handling of the flock much easier. Very little thought will show that the preventive measures here advocated can only be properly applied where this system of drafting has been carried out.

Other Investigations and Opinions.

. Apart from the foregoing experiments, investigations of a technical nature were carried on concerning the exact nature of the disease, and several fresh points were acquired. As a result the work of investigation is still being carried on at Wallaceville, though it must necessarily be slow. No useful purpose would be served by publishing the lines of research being followed, and this will not be done unless something tangible and conclusive is obtained.

Arrangements are already on foot for a series of fresh experiments in different districts next season —concerned with the possibility of preventing the disease by the use of sundry mineral licks.

It may be well, in view of the fact that such opinions have been advanced by men of some authority and hence adopted by many farmers, to repeat definitely that the disease causing the mortality is not lockjaw (tetanus) ; neither is it pneumonia. The theory recently advanced in Southland that the common weed sorrel is the cause is dealt with in another article.

Note. —The writer wishes to acknowledge his indebtedness to the authorities •of the Medical School, Dunedin, for the many facilities granted him in connection with this investigation; also to Mr. David Weir, Inspector of Stock, Ranfurly, for his ever-willing assistance.

* This term as commonly used also includes castration and/or tailing.