As we saw in the last chapter, some fast-growing lambs from lowland flocks go to slaughter straight from the ewe, but many more lambs remain on farms after being weaned. Some purebred lambs and a large number of crossbred females, such as Mules, Mashams and halfbreds, produced to be breeding ewes in the future, will be managed so that they look at their best for the autumn sales, or will be kept for breeding on their farm of birth. Many other lambs remain to be fattened either on their farm of birth or to be sold at autumn store sales. These include crossbred lambs by terminal sires such as the Texel and Suffolk, male or castrated Mules, or other recognized crossbred lambs and surplus purebred males or castrated males, particularly from hill flocks.

Weaning is a stressful time for lambs, and, combined perhaps with transport, sale through a market and a change of grazing, it is not surprising that these management changes can precipitate various disease outbreaks. Although many lambs will finish during the autumn months, some will remain, often to be housed and fattened indoors to supply the market during the winter before next year’s early lambs arrive for the Easter market.

Fig. 509 Store lambs: in late autumn they will be taken inside in batches for fattening to provide a supply of finished lambs at intervals through the winter.

Replacement Lambs for Breeding

Management of this category of lambs will depend on the breed, type of farm, and whether they are to be retained on the farm of birth or sold in the autumn breeding sales. Female hill lambs may be overwintered on the farm of origin where forage and supplementary feeding will be necessary in hard winters, or, commonly, may be sent to the lowlands to winter on better pasture, for example on dairy farms. If this is the case it must be clear who has responsibility for inspecting them, which must be done regularly, and dealing speedily with any problems that occur. Some lowland ewe lambs and crossbreeds such as the Mule will be put to the ram in their first autumn so must be kept growing without getting over-fat. They need to have achieved 60 per cent of their adult weight by tupping time if they are to perform satisfactorily.

Whatever their category, lambs of this age group are all susceptible to the diseases described below, so appropriate vaccination schedules, good worm control and identification of any trace element deficiencies are crucial.

Disease Problems

The main disease problems potentially affecting lambs of this age group during the autumn and winter after weaning are:

Clostridial Diseases

Lambs that have had a full course (two injections) of clostridial vaccine well before weaning should be protected against the common clostridial diseases (see Chapter 4). Those that have not been vaccinated are at high risk, particularly from pulpy kidney (enterotoxaemia), which is often triggered by a move on to new pasture. Affected animals, often the best, are usually just found dead, although occasionally neurological signs may be seen before death occurs. Diagnosis is made at post-mortem examination based on the characteristic changes in the kidneys that give the disease its name, together with no vaccination history.

The vaccine is cheap and effective, so it is difficult to understand why many animals remain unvaccinated. Bought-in lambs with no history of vaccination present a particular problem – they should receive their first injection as soon as possible after purchase, and should be kept away from lush grazing such as aftermath until vaccination is complete, if that is possible. When buying lambs such as these, always enquire about vaccination status in detail – don’t rely on the seller just saying they are vaccinated, as they may have received only one injection.

Pasteurellosis

Systemic pasteurellosis caused by Bibersteinia (Pasteurella) trehalosi is an important disease of this age group of lambs, and commonly results in sudden death. Trigger factors include any stressful event such as movement, change of diet and bad weather. Vaccination can be carried out with either a combined clostridial/pasteurellosis vaccine or a pasteurellosis vaccine alone (see Chapter 4). This vaccine is much improved now, although it cannot be guaranteed to give complete protection because the disease involves a variety of strains of the organism, not all of which can be included in the vaccine.

The main problems associated with this disease are that it often occurs soon after store lambs are purchased or moved on to new pasture, before any vaccination programme can be completed for bought-in animals; and the stress of gathering can precipitate disease outbreaks. It can therefore be problematic to deal with. One possible strategy is to give an injection of antibiotic at the same time as the first dose of vaccine, but it is best to discuss this with your vet based on a firm diagnosis after postmortem examination, or on previous experience of the disease.

Parasitic Gastro-Enteritis

It is usual practice at this stage to worm lambs on purchase, or before moving them to new safe pasture (for example, aftermath) after weaning. Before anthelmintic resistance started to become a problem this system worked very well, enabling good growth rates with little further dosing being necessary. Now, however, the view is that if lambs are to be put on safe pasture it is important to try to prevent contamination with anthelmintic-resistant worms. For homebred lambs, leaving the best ones undosed will ensure that a small population of susceptible worms is carried on to the new pasture, sufficient to allow the lambs to develop their own immunity without having a damaging effect on their growth. For bought-in lambs you don’t know what worms they are bringing with them. One strategy is to yard them and dose with two different wormers, before turning them out a day later. As we have stressed before, this is a complicated subject and it is worth taking advice based on the latest knowledge, as the advent of new worming drugs may alter things.

If lambs are grazing contaminated ground, roundworms continue to be a major cause of failure to thrive at this stage when these lambs should be gaining weight. Severe worm infections can leave permanent damage to the gut, meaning lambs continue to do badly even if an effective anthelmintic has been given. A poor diet, low in protein, also has an adverse influence on how well lambs tolerate worm infections. Trace element deficiencies are often blamed for this sort of picture, but chronic worm damage does need to be considered, too.

Liver Fluke

Acute fluke may cause deaths in the autumn if weaned lambs are put on pasture containing a fluke habitat, particularly if the summer has been wet. Drenching with a specific liver fluke treatment may be necessary, based on the forecast of acute fluke being likely. Triclabendazole is usually the treatment of choice, as this is effective against very young fluke, unless a resistance problem has been identified on the farm.

Trace Element Deficiencies

Failure to thrive has been associated with deficiencies of cobalt, copper and selenium, although the possible effects of poor nutrition and/or roundworm infection should always be investigated before providing expensive trace element supplementation ‘just in case’. Diagnosis of a trace element deficiency will involve some or all of past flock history, area and type of farm, clinical examination, blood sampling, post-mortem examination, liver samples and response to test treatments.

Cobalt

The most common deficiency to cause ill thrift is cobalt. It is actually a deficiency of vitamin B12, of which cobalt is a crucial component. Clinical signs are weight loss, poor appetite, poor open fleece, anaemia, and discharge from the eyes. Whilst various sampling as listed above can be carried out, if cobalt deficiency is suspected, injecting lambs with vitamin B12 can give a rapid answer, though any improvement is fairly short-lived. Best of all, weigh the lambs, treat some lambs and leave some untreated, and re-weigh in three to four weeks, comparing the two groups. If the treated lambs have improved and the untreated ones have not, this indicates that treatment of the whole group should be carried out.

While injection with vitamin B12 is effective in the short term, it is not really practical as a long-term solution. There are various ways of supplying cobalt, of which drenching with a cobalt solution or administering cobalt bullets are the most common. Cobalt is one of the trace elements contained in soluble glass boluses, but these also contain copper and selenium so may not be appropriate in all affected farms.

Copper

A deficiency of copper can be responsible for ill thrift, but is quite rare. The most common situation in which it has been identified is where hill land has been improved by liming and the application of fertilizer. Where lambs had previously thrived on the unimproved land, they did badly on the improved land, showing poor weight gains and poor quality wool growth. What happened was that the lime and fertilizer made copper less available in the grazing. Supplementation with copper sorted out the problem.

This scenario is in fact less likely to happen now, as this type of reclamation of hill land is no longer carried out.

Selenium

Some areas of the country are known to be selenium deficient, and growth of lambs in this age group may suffer if they are not supplemented. Blood sampling to measure an enzyme in red blood cells that contains selenium is helpful in diagnosis. Supplementation is by injection, selenium bullet administration or use of the soluble glass boluses containing cobalt, selenium and copper if indicated.

Other Chronic Diseases

The on-going effects of earlier disease outbreaks may still be evident in this age group. These include chronic pneumonia, lungworms (most anthelmintics deal with these, so they rarely cause disease on their own), chronic lameness (especially footrot and contagious ovine digital dermatitis – see Chapter 14) and chronic joint problems such as erysipelas.

Fattening Lambs

Fattening Lambs on Brassicas and Roots

Brassica and root crops are commonly grown to provide grazing for fattening lambs in the autumn and winter. The two main problems associated with them are physical (muddy fields in wet weather) and poisoning (particularly associated with some brassicas). To avoid these, grazing should be limited, and access to a grass field should be provided at all times.

Specific Problems of Housed Fattening Lambs

The housing of tail-end lambs to fatten them during the winter is common practice, and brings with it specific potential problems. Housed animals must always be provided with a clean source of fresh water.

Fig. 519 A mixed bunch of store lambs recently housed for fattening. Their fleeces are still wet, which could lead to problems with pneumonia – quite likely unless the ventilation is good. Try to house animals when they are dry.

Pneumonia

Pneumonia occurs where housing conditions are poor with restricted ventilation. Although prior vaccination against pasteurellosis will help to control this, poor air circulation can overcome any protection given by the vaccine. In addition, a combined infection with respiratory viruses and bacteria called Mycoplasma species will inevitably happen when groups of lambs from different sources are mixed, and is a common cause of respiratory problems. Although antibiotic treatment may help, improving the ventilation is the only long-term solution.

Rumen Acidosis

Rumen acidosis occurs when housed lambs are introduced too quickly to a diet high in grains. The rumen microbes that do most of the digestion of food are easily killed if food high in starch is introduced too quickly: lambs go off their food, look dull, bloated and uncomfortable, and in severe cases may die. This problem can be prevented by supplying plenty of good forage and introducing whole grains into the diet slowly, giving the rumen flora time to adapt.

Urethral Calculi

Male lambs and particularly castrated males (wethers) housed for fattening are vulnerable to stones developing in the bladder (see also Chapter 8). These are actually more like sandy particles and can block the urethra. This is a serious, fatal condition if not recognized quickly, and even if it is recognized, it may not be possible to treat successfully or economically. Wether lambs are most susceptible because they have a narrow, undeveloped urethra compared with entire males. Lambs with a blocked urethra are often not noticed until the urethra has ruptured, allowing urine to leak into the skin of the lower abdomen, by which time the affected animal is dull and will eventually die. Early signs of obstruction are abdominal pain, kicking at the abdomen and crouching to attempt to urinate.

Treatment is difficult and not worth attempting except in early cases as previously described; your vet may attempt to snip off the urethral appendage, and if this is the only part obstructed, the lamb may be able to pass urine again. Other more complicated surgical procedures are possible, but rarely financially viable. More advanced cases should be humanely destroyed.

There are two main causes that should be investigated in the event of an outbreak: the water supply, and the mineral content of the diet.

The water supply: Plenty of fresh, clean water should be supplied: if it is not, the lambs will not drink sufficient and their urine becomes concentrated, precipitating stone formation.

The mineral content of the diet: The important minerals to consider are calcium, phosphorus and, particularly, magnesium. If these are unbalanced, stone formation is precipitated. Manufacturers of commercial fattening diets are well aware of this potential problem, so it is more likely to occur if the lambs are being fed on a home-mixed diet. Ewe rations commonly contain increased amounts of magnesium and should not be fed to this class of stock.

Further cases are likely within the affected group, but can be reduced by giving a daily dose of ammonium chloride – your vet will give details.

Fig. 524 Introducing grains too quickly into the diet can cause rumen acidosis, particularly if the grain is crushed. Whole grains are digested more slowly.

Fig. 525 A case of urethral obstruction – note the large swelling around the prepuce under the abdomen.

Fig. 526 Plenty of clean water should be available. This waterbowl is clean but is leaking, making the surrounding area wet.

Fig. 527 The water in this tank is decidedly murky and needs cleaning out. Bowls are easier to keep clean.