Lamb Losses from Birth to 6 Months

New Zealand Journal of Agriculture, Volume 97, Issue 3, 15 September 1958, Page 265

Lamb Losses from Birth to 6 Months

A paper given at the Ruakura Farmers' Conference Week by D. C. DODD, Veterinary Diagnostic Officer, Department of Agriculture Animal Research Station, Hamilton

THE period in a lamb's life from birth to 6 months is obviously a very important one ’ from both economic and health considerations. It has been estimated in a survey conducted by the New Zealand Meat and Wool Boards' Economic Service that every year about 4,000,000 lambs fail to reach weaning or sale age. The potential loss is therefore about £10,000,000 to £12,000,000. The figure of 4,000, covers all losses, but I intend to deal only with losses that occur in lambs that are born alive and normal and absolutely free from any infectious disease. A separate figure for losses in this group is not available.

THE causes of lamb losses vary greatly. Some are accidental, some are preventable, some are curable, and some are incurable. The ones which we can prevent or cure are the ones which we are going to talk about.

Before getting on to specific diseases let us consider firstly why, if a lamb is born perfectly healthy, so many become infected with disease producing organisms, and how . these organisms get into the body. The most important diseases occur as the result of either wound infection or of infectious bacteria being taken in through the mouth. The first wound which all lambs must sustain is the rupture of the navel cord, so that within minutes of being born the cord becomes contaminated with bacteria and there is . danger of infection with . a disease producing variety. This brings us, then, to the first group of diseases, known as navel infection.

When the navel cord is still moist and contains the freshly clotted blood it provides an ideal place for bacteria to grow. In order to minimise this danger the cord normally dries very quickly and ceases within a day or two except under wet conditions to become a means of entry for bacteria. Broadly, two different types of infection occur: the first causes rapid, death from blood poisoning within the first few days and the other a slower death in one or two weeks (but sometimes longer) by forming abscesses at the navel and in various organs, especially the liver and lungs.

Most lambs with the blood poisoning type are found dead and can quite easily be picked by their appearance; they putrefy and blow up rapidly, the belly is swollen, and the skin of the belly and inside the thighs has a bluish appearance. When you open them, you find under the skin around the navel a layer of dark reddish bloodstained gelatinous material; inside the abdomen all the organs have a similar dark red appearance and there is usually much dark blood'

stained fluid in the abdomen and in the sac around the heart. The organisms which cause this type of infection belong to the clostridial group; they are always present in the soil and commonly infect wounds, causing blood poisoning or, more specifically, blackleg, malignant oedema, and tetanus. Owing to the rapidity of death in these cases of navel infection treatment is usually too late, but I believe that it is always worth trying an injection of penicillin. Even if you were to save only one in ten, you would more than recover the cost of the penicillin. As treatment is unlikely to be suecessful, it is fortunate that we can

prevent this disease by vaccination of the ewes 3 weeks before lambing. There is no need for me to go into the details of this. The problem can be discussed with your veterinary surgeon or Livestock Instructor. As these blood poisoning organisms are always present in the soil, it is important that you lamb your ewes on well grassed paddocks away from the sheep yards and places where sheep tend to camp; such places are always a greater source of infect ion than “clean” paddocks . The things to remember about this type of navel infection are (1) that it is the most common, (2) that it affects lambs less than a week old, and (3)

that it can be prevented by vaccination of ewes before lambing.

The other types of navel infection are less common and cannot be prevented by vaccination. When pus forming bacteria enter the navel cord they usually form a local abscess just inside the body and then spread to the liver and often the lungs and joints; in the liver and lungs there may be dozens of small abscesses. Lambs affected with these organisms usually die at one to three weeks, but some live longer and a few even thrive and are eventually killed as fat lambs. Only then are the signs of infection (multiple liver abscesses) found. Treatment of lambs with this type of infection with penicillin is most unlikely to be successful, so that losses from this cause simply have to be written off as a natural hazard.

Post-marking Infections

The next wounds which all lambs must suffer are those that occur at marking time; the same type of organisms that infect the navel cord infect marking wounds. There are a number of different methods of marking lambs, but I do not intend to enter into an argument on which is the best. There are champions for each method, and my advice is to stick to the one you like best.

It is as well to remember, however, that all of these methods cause wounds through which bacteria can enter the body. Again we have the clostridial type which causes blackleg and malignant oedema (blood poisoning) and another member of the same group which causes tetanus.

The same remarks, as far as treatment and prevention of blood poisoning are concerned, apply here. Some can be saved by penicillin, while those from ewes which have been vaccinated will still have a fair degree of protection.

With regard to tetanus I think it fair to say that the use of rubber rings does seem to favour the development of this disease; only occasionally does it become a problem. Though tetanus is easily prevented, it is notoriously difficult to cure. Occasionally success may be obtained by the use of penicillin and tetanus antiserum, but generally it is a waste of time and money.

If you use the knife for marking your lambs, there is little danger of infection with blackleg or tetanus organisms because the wounds are large, well drained, and open to the air. Pus forming and certain other organisms can, however, still gain entry through these wounds and .often set up infection in the limb or spinal joints.

By your own efforts you can do much to reduce the incidence of these infections by using clean methods at marking time. Don’t mark your lambs in the sheep yards and don’t use dirty instruments. The soil of sheep yards

is always heavily contaminated with bacteria, so you would be wise to set up temporary yards for marking in a well grassed paddock.

If you use instruments and particularly a knife, make sure that you thoroughly clean and boil it before use; then during marking keep a tin of disinfectant beside you and wash the knife in it frequently. It wouldn’t be such a bad idea, you know, if you were to have two knives and change them after about every tenth lamb, keeping the spare one in disinfectant.

If you are unlucky enough to strike an outbreak of joint infection (arthritis) after docking, you must get in quickly with penicillin if you want to save the lambs. If the infection localises in the spinal joints, you won’t notice anything wrong with a lamb until it becomes paralysed, by which time it is too late to save it.

Enterotoxaemia or Pulpy Kidney

An infection which enters through the mouth and the only one which we will discuss is enterotoxaemia or pulpy kidney, an important, if not the most important, cause of death in lambs. Some understanding of how this disease develops will help you to appreciate the methods of prevention and control.

Basically pulpy kidney is the result of the rapid multiplication in the small intestine of an organism which is normally present after being picked up by the lamb from the pasture. This organism produces a powerful toxin or poison which is absorbed from the lower part of the small intestine. If this is so, you will ask then why all lambs don’t get pulpy kidney.

The reason is that normally there are insufficient organisms present to produce enough toxin to do any damage, but if for some reason the passage of the contents through the intestine is slowed . down, the organisms multiply rapidly and produce sufficient toxin to set up the disease. Unfortunately for the fat lamb producer this set of circumstances occurs more often in the best lambs than in the tail of a mob. The disease is usually more prevalent on the best pastures and can occur at any age from birth onward, though in our experience in the Auckland Province it is most common these days at 10 to 15 weeks.

In the most common form of the disease death occurs in a matter of hours after the onset of symptoms, so that rarely do you ever see an affected lamb alive; most are found dead. If you do find an affected lamb before death, it is obviously in pain, may be scouring a little, and finally goes into a convulsion with head thrown back, frothing at the mouth, and paddling of the legs.

When you open a lamb which has died from pulpy kidney there are fairly characteristic changes to be seen, but only if it has been dead for a few hours; if it has just died or been killed in the final stages, very few changes are present and a diagnosis is difficult, but if it has been dead for a few hours quite characteristic changes are usually present.

The sac around the heart is filled with a clear, slightly yellowish fluid which often has changed to a thick jelly-like clot; the kidneys are soft and mushy, hence the name pulpy kidney, and have obviously degenerated much more than the other organs, which are still firm. The intestines are very fragile and cannot be run out, as they break with the slightest pull; they are also much thicker than normal and the chain of associated lymph nodes is swollen and juicy and up to about four times normal size. Remember that these changes and particularly the pulpy state of the kidneys are not present until a few hours after death.

Prevention and Control

The methods of prevention and control of this disease are from your point of view the most important aspect. It is not my intention to go into careful detail, but to give you the general principles of prevention and control. Likewise it is not my intention to say that you must use this or that method. I believe that the disease must be considered finally as it applies to each farm and that can only be done by you in discussion with your veterinary adviser. Now the prevention of pulpy kidney, is by vaccination either of the ewes or the lambs; but which you vaccinate depends on the age at which the lambs are affected.

If from previous experience it is known that you can expect most of your losses in lambs up to about 6 weeks old, you must vaccinate the ewes, but if most losses are after this age, you must vaccinate the lambs at marking time.

If losses occur both before and after 6 weeks, you must vaccinate both the ewes and the lambs.

Vaccination of the ewes transfers protection to the lambs by means of antibodies in the first milk or colostrum; this type of immunity lasts for. only a , few weeks and, of course, if for any reason a lamb does not get colostrum, it is not protected. If the ewes have never been vaccinated before, even as lambs, they have to be injected with the vaccine twice; the first dose can be given at any convenient time providing it is given at least a month before the second; the second should then be given as near as possible to 2 weeks before lambing.

As lambing is spread over a few weeks, it is advisable to divide the

ewes into an early and late lambing flock and treat them separately for the purpose of the second vaccination; this is done so that as many ewes as possible will get the second dose of vaccine about 2 weeks before lambing.

In subsequent years it is necessary to give the ewes only one injection of vaccine to boost the immunity just before lambing. One difficulty that you may strike is the unknown vaccination history of bought in ewes, so that you do not know whether they have been vaccinated once or twice or if ever.

As the immunity conferred by the milk of the vaccinated mother lasts for only a few weeks, vaccination of the lambs is necessary if most losses tend to be in lambs over 6 weeks. To give really good protection two injections should be given. It should be convenient to give the first injection at marking time at about 2 to 3 weeks and the second can be given 3 to 4 weeks later. The first dose of vaccine does confer some immunity, but it often is insufficient if a bad outbreak occurs later. What the first dose really ' does is sensitise the body to a second injection later and when this second dose is given the body responds more quickly and gives a stronger and longer lasting immunity.

If you wish, you can, having given the first injection, delay the second until an outbreak of pulpy kidney is threatened. Now don’t take me up wrongly over this.

I don’t mean that you go out one morning to have a look at your flock and say “Ah yes, I think we’re going to have an outbreak of pulpy kidney, I’d better vaccinate the lambs again,” just as you’d look at the sky and say “Mm, I think it’s going to rain.” You don’t know that an outbreak is threatened until you start to get losses. This method is obviously a bit risky, for there is a delay of a few days before the second injection takes effect.

Now if you haven’t vaccinated the ewes or the lambs and you have an outbreak of pulpy kidney, all is not lost, for you still have pulpy kidney antiserum to fall back on. This is more expensive than vaccination, but has the advantage that it gives immediate though only a short protection. A few years ago the antiserum was used very little, but during, the past 2 years there has been an unprecedented increase in the amount of antiserum used. Reports from veterinary surgeons who have used antiserum in serious outbreaks show that the antiserum can be of very great value and in many cases losses ceased immediately.

Apart from these methods of prevention and control certain other recommendations are usually made. Anyone who has had experience of this disease in his lambs knows that

the most serious losses usually occur in the best and fastest growing lambs on very good pastures. Because of this we advise farmers to give the flock a check by moving it to a poorer pasture, if one is available. This will often cut losses considerably, but has obvious disadvantages, for it is well known that young growing animals take a long time to pick up again after a check like this. Vaccination alone sometimes causes sufficient check to growth to hold an outbreak until immunity develops. Whereas the disease is most common in the most forward lambs, it is by no means unknown in flocks that are not doing well, so it would not be wise to check them any more by cutting down the food intake. Over-eating of lush pasture is not, then, the only factor predisposing lambs to pulpy kidney.

This now brings me to the relationship between tapeworm infestation and pulpy kidney. There does seem to have been an increase in some areas in both these conditions in lambs and because both occur at the same time we have heard it said that tapeworms cause pulpy kidney. I will agree that this could look like cause and effect, but just because two things happen at the same time it does not follow that one caused the other.

There is no doubt as to the true cause of pulpy kidney and that is the production of a toxin by a specific organism in the intestine. Tapeworms by interfering with the passage of the contents of the intestine either through their bulk or perhaps by irritation to the intestine may well predispose a lamb to pulpy kidney, but they do not cause it.

I have seen many lambs that died of pulpy kidney both with and without tapeworms and I have seen many that had a heavy tapeworm infestation and were sold as first-class fat lambs.

My advice to you would be this: if you feel you must do something about the tapeworms, dose the lambs with nicotine-copper sulphate drench, but if pulpy kidney is also occurring, don’t neglect to do something about it too.

The subject of pulpy kidney is very complex. For this reason it is impossible and would indeed be foolish of me to say that you must do this, that, or the other to prevent or control pulpy kidney on your farm. Each case must be considered on its merits and advice given accordingly; if you are worried by this problem, have a talk with your veterinary surgeon or Livestock Instructor and get the advice to suit your farm.

Other Causes of Lamb Losses

Most other causes of lamb losses tend to be sporadic and as an overall percentage they are very low, but on individual farms they can be quite

serious. Some of the more important of these are copper and cobalt deficiency, white muscle disease, leptospirosis, and stomach worm infestation. White muscle disease occurs in the South Island only and occurs mainly on legume-dominant pastures and is somehow tied up with a deficiency of vitamin E.

The other four conditions can either be prevented or controlled and I intend to make only a few comments on each.

Copper deficiency is usually seen in lambs under 4 months and is shown by either a staggering gait or very fragile bones which fracture easily. It does not cause unthriftiness. An affected lamb cannot be saved by dosing with copper, but a soil deficiency can easily be overcome by topdressing. . .

Cobalt deficiency rarely occurs until after weaning and causes unthriftiness and marked loss of weight if the deficiency is severe. Dosing with cobalt gives a rapid response.

Leptospirosis has been seen in a number of flocks from different districts in lambs about 3 to 6 weeks old. The main features are jaundice and redwater. This disease is transmissible to man and causes a very serious illness, so if you find any lambs which die and have a distinctly yellow skin leave them alone. Call in your veterinary surgeon at once and get advice on how to treat any sick lambs and prevent it in the remainder.

Stomach worm infestation, or haemonchosis, is not in our experience a serious cause of losses in lambs up to 6 months, but may occasionally cause trouble. Lambs should not have to run the risk of heavy worm infestation if the ewes are kept relatively free from worms. If heavy infestation does happen, remember that these worms are blood suckers and can be killers and that lambs in prime condition can and do die from stomach worms alone. This is a fact which many sheep farmers are loathe to accept.

Immediate drenching with phenothiazine as soon as stomach worm infestation is diagnosed is imperative if the lambs are to be saved, but do not expect dramatic improvements in condition, for lambs which have become anaemic will pick up slowly. Put them on to your best pastures and give them every chance to get back into good condition.

This is by no means a complete list of the causes of lamb losses, but I have covered the important ones. I do not expect you to become your own veterinary surgeon and be able to diagnose all these diseases, but if you remember that you can keep navel infection and pulpy kidney under control and make an honest effort to do something about them, most of your worries about lamb losses in this age group will be over.