12 Lactating Ewes and Growing Lambs to Weaning

Milking sheep form only a tiny proportion of sheep kept in the UK, although they are an important part of the sheep industry in some countries in southern Europe, for example, southern France, Spain and Greece. It is beyond the scope of this book to go into any detail of the specific problems of milking flocks; sufficient to say that, as far as problems associated with lactation are concerned, mastitis is a major issue. Much of the wealth of information available about mastitis in dairy cattle can be applied to dairy sheep. Early removal of lambs from dairy ewes can lead to problems associated with artificial rearing, which are the same as those encountered when artificially rearing orphaned or surplus lambs.

For all other flocks, lamb growth in the first eight weeks or so is very much a reflection of the ewe’s milk yield. After this, lambs increasingly become independent of the ewe, feeding on grass and creep food if available, although the ewe still contributes a little in the form of milk. Lambs can manage without milk from between five and six weeks of age, although they will struggle if milk is abruptly withdrawn, for example, if the ewe dies, if they have not been used to eating creep feed.

Lambs are usually weaned when they are approximately sixteen weeks old, allowing a three-month period for the ewe to regain condition before the next tupping time (the rule of thumb of five months pregnancy, four months lactation and three months recovery is a useful one to remember). Fast-growing lowland lambs will often reach slaughter weight before sixteen weeks (twelve weeks is about the minimum), so will be taken straight off their mothers to go for slaughter. If the ewe has twins and only one lamb is taken, this can sometimes lead to mastitis problems. Leaving lambs with the ewe beyond about sixteen weeks is of little benefit to the lambs, but reduces the recovery time available to the ewe, so very late weaning is to be avoided.

Fig. 475 For dairy flocks, milking routine and hygiene is just as important as it is for dairy cattle.

Fig. 476 The first two weeks after birth are over, but there are disease risks in the period to weaning for both ewe and lambs.

Fig. 477 Lambs born and raised indoors for the Easter market face very different disease risks from those reared outdoors. Coccidiosis is a major problem in this type of system.

Fig. 478 The risks for hill ewes and lambs are rather different from those faced by lowland ewes and lambs. In this sort of environment diseases spread by ticks are a major threat. The common tick-borne diseases are tick-borne fever, which temporarily lowers resistance against other diseases; tick pyaemia, which results in abscesses developing in joints and internal organs; and louping ill, an often fatal viral disease.

Fig. 479 If rapid lamb growth is the aim, or if ewes’ milk is limited, provision of a creep-feed area allows lambs to be fed, but not the ewes.

Fig. 480 For heavily stocked lowland ewes and lambs the main disease risks are acute mastitis and hypomagnesaemia for the ewes, and internal parasites for the lambs. Roundworm control is very important (see Chapter 7).

The two most important diseases that affect ewes during this stage are mastitis and hypomagnesaemia (grass staggers). Both can result in sudden death of ewes, often before the lambs are able to survive independently, thus causing problems for the shepherd in getting the orphaned lambs to survive. For the growing lambs there are a number of important diseases to which they are susceptible at this stage, particularly coccidiosis, nematodirosis, parasitic gastro-enteritis (PGE) and trace element deficiencies.

Fig. 481 Ewes are very vulnerable to acute mastitis at peak lactation. It is not particularly common in newly lambed ewes unless the lambing environment is dirty. This ewe’s udder looks fine.

Fig. 482 Ewes rearing triplets are at particular risk of getting teat lesions and/or acute mastitis, so should be managed separately if possible, giving extra feed to the ewes and creep feed for the lambs.

Specific Diseases of Lactating Ewes

Mastitis

Lactating ewes are very vulnerable to mastitis. The udder tissue is highly active, particularly in ewes rearing twins and triplets. Acute mastitis mostly occurs during the peak of lactation, whereas chronic mastitis becomes evident around weaning time. Although we do not know a great deal about what predisposes ewes to mastitis, the following factors are implicated, certainly in acute mastitis: chilling of the udder in bad weather; not producing enough milk for the number of lambs they are rearing. In the case of ewes rearing triplets the lambs are constantly competing for milk, so they hang on to the teats with their sharp incisor teeth, causing injuries.

Signs of acute mastitis include being off their food, dullness, dragging a back leg, and lying for long periods. Always examine the udder of a ewe that becomes ill during lactation.

Most mastitis cases, acute or chronic, are caused by two particular bacteria: Staphylococcus aureus (found on the skin), and/or Mannheimia haemolytica (one of the causes of pasteurellosis). Acute gangrenous mastitis (‘black bag’) can occur in a matter of hours, resulting in a very sick or even dead ewe. The affected half of the udder quickly turns from being hot and inflamed to cold and blue. At this stage, saving the affected half is impossible, and the main aim is to save the ewe with the help of antibiotic and anti-inflammatory drugs that your vet is likely to supply. Nursing the ewe is also beneficial – bathing and stripping out the affected teat and trying to tempt her to eat. Her lambs will also need attention if they are under six weeks of age, but they often do not take well to bottle feeding at this stage.

Some ewes do manage to survive the acute disease without treatment – this sometimes happens in hill ewes that are not seen very frequently, and the first the shepherd knows about it is at weaning when the ewe comes in with half the udder partially or completely missing. Ewes cannot be sold through a market until the udder is largely healed.

Chronic mastitis is often the end result of a mild infection during lactation, which becomes evident after weaning. By the time that palpable changes are present in the udder, no treatment is possible and affected ewes are usually culled.

Prevention of mastitis is difficult. If acute mastitis in lactation is the main problem, try to provide shelter for the ewes during bad weather and make sure ewes are only left with the lambs they can comfortably rear, provide extra concentrates for the ewes and creep feed for the lambs. Letting ewes rear triplets is always risky, but can be successful if they are managed as a separate group. Sometimes flocks experience problems where ewes appear to be unaffected at weaning, but subsequently develop mastitis. If these are valuable pedigree ewes it may be worth considering using intramammary antibiotic tubes at weaning, as used in cattle. Care must be taken that the contents are infused as cleanly as possible, and tubes should not be split between the two teats. Weaning management is also important – remove all lambs at the same time and put the ewes on bare pasture to rapidly reduce milk production; however, do not deprive them of water.

Fig. 483 This ewe’s udder looks normal, but needs to be palpated to be sure.

Fig. 484 This ewe had acute gengrenous mastitis several weeks previously, resulting in several areas of tissue that are dead and will eventually slough off.

Fig. 485 A case where most of the affected gland has sloughed off, and is now in the process of healing.

Fig. 486 Part of one side of the udder has been lost, with a remnant of tissue still attached. Beware of trying to remove lumps like this by just cutting them off, since they usually have large blood vessels in them. This lump could probably be removed by using a castration ring over the narrow neck.

Fig. 487 All that remains here is a healed scar where the affected half of the udder sloughed off. Healing can take many months.

Fig. 488 A very enlarged and lumpy-looking udder – check for chronic mastitis.

Teat Lesions

These usually begin as abrasions caused by the sharp teeth of lambs hanging on to teats as they suck. They often lead to mastitis and have two main causes: orf infection, or staphylococcal infection. As we have already seen, orf spreads from the mouths of infected lambs to the ewes’ teats, and vice versa. Orf is difficult to deal with, as the virus infection will run its course. Application of antibiotic spray may help to speed healing by its astringent action and through preventing secondary infection. See Chapter 4 for details on vaccination – this should be done for the ewes well in advance of lambing time. If the vaccine is used in lambs be careful that it is applied in a hidden area that the ewe will not contact – inside the elbow is the usual site. Also bear in mind the danger of human infection when handling the vaccine and infected animals.

Staphylococcal infection arises when teats are damaged by the sharp teeth of lambs and skin bacteria invade, causing nasty painful scabby areas at the base of the teats. The most common reason for this problem to occur is shortage of milk – either thin ewes rearing twins or ewes rearing triplets.

Treatment must be given quickly and vigorously; if not, it is highly likely that mastitis will intervene, and ewe and lambs will all suffer the consequences. Your vet is likely to prescribe injectable antibiotics, a non-steroidal anti-inflammatory drug, and perhaps local anaesthetic cream to rub on the teats to make it more comfortable for the ewe to let her lambs suck.

Fig. 489 This ewe has a severe teat lesion, and has also developed mastitis. She will not be able to feed her lambs from this half of the udder, and needs treatment.

Fig. 490 A severe staphylococcal infection of the skin at the base of both teats. This is extremely painful, and often the ewe will not let the lambs suck. Mastitis is a common sequel.

Hypomagnesaemia (Grass Staggers)

Magnesium is not stored in the body, so a regular daily intake is required. Fresh, rapidly growing spring grass, particularly grass that has been fertilized with nitrogen, is very low in this mineral, so ewes rearing two or more lambs, which have a particularly high daily magnesium requirement, are very susceptible to deficiency if their diet is not being supplemented. Ewes with singles and hill ewes grazing poorer environments are less likely to be affected.

The signs of hypomagnesaemia develop very rapidly – affected animals are very nervous and jumpy, and develop convulsions or can just drop dead. The most frequent picture is that ewes are just found dead with hungry lambs beside them.

If found alive, treatment is by injecting 40–60ml of a commercially prepared 25 per cent magnesium sulphate solution, together with the same volume of 20 per cent calcium borogluconate solution, under the skin, although not all treated animals recover. Prevention is by supplying a source of magnesium in the diet during the danger period. This can be done by feeding concentrates with added magnesium, administering a magnesium bolus, or by dressing the pasture with calcined magnesite. Although this seems expensive, the loss of several ewes and the stunting or death of their lambs can mean substantial losses in a vulnerable flock.

Fig. 491 Fast-growing spring grass is associated with hypomagnesaemia.

Fig. 492 Ewes rearing twins on fresh spring grass are especially at risk of hypomagnesaemia.

Fig. 493 Collapsed lactating ewes that lie quietly are more likely to be suffering from hypocalcaemia than hypomagnesaemia. Treatment is by injection of calcium under the skin.

Fig. 494 This ewe was badly affected with kangaroo gait. You can see that her front legs are abnormally knuckled over at the fetlocks, and she is trying to walk with her back legs right under her body. She recovered after several weeks, during which she had to have food and water carried to her.

Other Diseases of Lactating Ewes

Hypocalcaemia

Although this is more commonly seen just before lambing, it can also affect ewes after lambing. So any collapsed lactating ewe should be given an injection of 50–80ml 20 per cent calcium under the skin unless there is another obvious cause of the problem. They should soon respond if it is a straightforward case.

Kangaroo Gait

This is an unusual and intriguing neurological condition that occasionally affects lactating ewes. They lose the ability to use their front legs, which knuckle underneath them, and use their back legs to move, looking a bit like a kangaroo, from which the disease gets its name. Badly affected ewes may not be able to stand at all. Most ewes do gradually recover, with this perhaps happening faster if her lambs are weaned as soon as possible. It is important that affected ewes are put in a small paddock and given food and water if they cannot get to it themselves. The cause of this condition is unknown.

Fig. 495 A ewe with woolbreak; otherwise she is perfectly healthy, and the wool will regrow normally.

Woolbreak

Woolbreak is common after lambing, especially in ewes that have had pregnancy toxaemia, a bad lambing, or mastitis, although some ewes just lose their fleece through natural shedding. The wool is lost because the fibres are weakened and break, but it later regrows normally. Woolbreak is not accompanied by any abnormal itching; if ewes are losing their wool and are itchy, sheep scab or lice should be suspected.

Specific Diseases of Growing Lambs

Clostridial Diseases and Pasteurellosis

Lambs from fully vaccinated ewes are protected against clostridial diseases by colostral antibodies for the first twelve to sixteen weeks. After this they become vulnerable, particularly to pulpy kidney, unless they themselves receive a full course of two injections four to six weeks apart. If and when to vaccinate growing lambs is always a finely balanced decision, and will usually be based on past experience. Most lambs slaughtered by five to six months, and many older than this, are not vaccinated, but it is always a risky strategy to adopt. Remember that colostral protection against pasteurellosis is much shorter – only two to five weeks – so if this disease is an issue, vaccination of lambs will have to be started by three weeks of age. Weaning is a particularly stressful time and may trigger disease shortly afterwards. If this type of disease outbreak has been experienced in the past, the lambs should definitely be vaccinated so they complete their course well before weaning. (See Chapter 4 on vaccination.)

Fig. 496 Thriving, healthy lambs from hill ewes.

Fig. 497 A group of healthy-looking lowland lambs.

Ill Thrift in Growing Lambs

For the first eight weeks or so when lambs are dependent on the milk of their mothers, anything that lowers milk yield will affect growth adversely. The most common reason for this, as we have seen, is mastitis, which can leave a few stunted lambs among a mostly thriving flock. Poor nutrition of the ewes at this stage as a result of lack of grass will have a more general impact, with ewes losing weight and lamb growth affected. Apart from these reasons for reduced growth, there are two main groups of diseases that can have a major effect:

• Diseases caused by internal parasites.
• Diseases due to trace element deficiencies – those responsible for poor growth tend to be more apparent after weaning and will therefore be dealt with in Chapter 13. Other problems caused by selenium and copper deficiency will be mentioned below.

Investigating the cause of ill thrift in lambs usually requires veterinary and laboratory expertise. It is easy to assume that either worms or mineral deficiency is the cause, and to spend a considerable amount of money on treatments that might well be inappropriate without confirmation from laboratory tests, perhaps with post-mortem examination of typically affected lambs, too.

Diseases Caused by Internal Parasites

Coccidiosis, nematodirosis and parasitic gastro-enteritis, all of which lead to scouring, ill thrift and deaths, have already been addressed in Chapter 7, so only the key points will be summarized here.

Coccidiosis

• Coccidiosis occurs mainly in intensively reared lambs kept indoors for more than a few days.
• It can occur outside where ewes and lambs are heavily stocked at pasture.
• The disease affects mainly lambs up to eight weeks of age.
• Ewes produce low numbers of oocysts, but lambs produce many millions – early-born lambs act as the source of infection for those born later.
• Damp, poorly bedded pens increase the risk of disease.
• Effective drenches are available for treatment or to be given strategically to prevent disease.

Fig. 498 Lambs near weaning age will be at risk from clostridial diseases if they have not received a full course of two injections of vaccine.

Fig. 499 These lambs are just at the stage when they will pick up coccidial oocysts from the bedding. Disease can occur from three to four weeks of age.

Fig. 500 Artificially reared lambs may be at particular risk of coccidiosis if they are kept in pens where ewes and lambs have been previously. To avoid this risk they should be kept in pens that have not had lambs in, or that have been thoroughly cleaned.

Fig. 501 Rearing lambs on wire mesh is not common in this country but is done occasionally in areas where straw bedding is difficult to obtain. It does mean that they will not get coccidiosis as the faeces fall through the mesh, so contamination with coccidial oocysts does not occur.

Nematodirosis

• Nematodirosis affects lambs at grass.
• It is transmitted on pasture from lambs born one year to those born the next year.
• Lambs older than twelve weeks are rarely affected, although recently disease has been reported in the autumn in older animals.
• The occurrence of disease depends on the weather – mass hatching of infective larvae occurs after sensitization by cold, followed by a 10°C rise in temperature, so disease only occurs if susceptible lambs are grazing at the time of mass larval hatching.
• The likely occurrence of disease can be predicted, and strategic dosing carried out if necessary.

Combined Infection with Coccidia and Nematodirus

If lambs are infected concurrently with these two parasites the consequences can be more severe than those caused by either parasite alone, and deaths are likely to occur. Laboratory examination of carcases and faecal samples is likely to be necessary to confirm the dual infection. Treatment of surviving lambs with both an anthelmintic and anticoccidial is then necessary, and supportive treatment for dehydration may be needed as well.

Parasitic Gastro-Enteritis (PGE)

This important disease caused by mixed infections of roundworms has also been addressed in Chapter 7. The key issues are as follows:

Fig. 502 These lambs may be at risk of nematodirosis, depending on previous grazing patterns and weather. They will certainly be increasingly at risk of PGE as the grazing season progresses, unless roundworm control is adequate.

Fig. 503 Lambs of this size should be finished as quickly as possible so as to avoid the main worm challenge that builds up by early summer.

Fig. 504 Fast-growing, muscular lambs are most likely to develop white muscle disease, although it can be seen in other types of lamb, too.

• Large numbers of infective larvae build up on pasture in the late spring and early summer – these come from overwintered larvae on the pasture and from ewes in the period around lambing and early lactation.
• Larvae numbers can be reduced by dosing ewes around the time of lambing and three to four weeks into lactation, or by using an anthelmintic with persistent action around lambing.
• This must be part of a planned approach to controlling roundworm infection.
• It must involve the responsible use of anthelmintics to reduce the development of anthelmintic resistance in the flock.
• Drenching lambs based on faecal egg counts rather than blanket treatment at set times.
• Getting finished lambs from lowland flocks away as quickly as possible before the larval population builds up.

At the risk of repetition, do take advice on this important and complicated subject.

Trace Element Deficiencies

Ill thrift caused by a deficiency of cobalt and, less commonly, copper and selenium, is usually more of a problem in weaned lambs, so will be covered in Chapter 13. However, there are two specific problems of lambs in this age group caused by trace element deficiencies: delayed swayback and white muscle disease.

Other Diseases of Growing Lambs

There are several other diseases that may be seen from time to time in this age group of lambs.

Erysipelas Arthritis

This disease is caused by the bacterium Erysipelothrix rhusiopathiae, and, like neonatal polyarthritis (joint ill), is picked up in the first days of life. However, instead of becoming obvious straightaway it can be weeks or even several months before it becomes apparent that lambs have developed joint problems as a result. The most commonly affected joints are the knees, hips and stifles, and these become enlarged, with damage to the joint surfaces. Unlike with joint ill, the joints are not distended with fluid or pus. If the disease is confirmed (by blood sampling usually), a vaccination programme can be included in the flock health plan – see Chapter 4 for more details. Badly affected lambs will not thrive and are better humanely slaughtered on welfare grounds.

Fig. 505 This lamb has enlarged knee joints and its right stifle is also affected. The most likely cause is erysipelas infection.

Fig. 506 Some lambs from lowland ewes may go straight to slaughter before weaning, but removing only one of a pair may predispose the ewe to chronic mastitis.

Nephrosis

This degenerative kidney disease occasionally causes lambs to become dull, lose weight and eventually to die. As the cause of this condition is unknown there is no method of prevention.

Border Disease

This viral disease has already been mentioned as a cause of abortion and the birth of ‘hairy shaker’ lambs. Sometimes persistently infected lambs that are not visibly abnormal at birth, later fail to thrive and may die. While alive they act as a source of infection to other uninfected sheep, and are a particular risk to pregnant ewes; so if this disease is diagnosed in a flock it is best to cull any poorly thriving lambs.

Weaning Procedures

By about sixteen weeks of age, lambs should be ready to be weaned as they are able to thrive independently of the ewes. The ewes themselves need a period of recovery before the next tupping time, particularly if they have reared twins or triplets – about three months’ recovery time is usually allowed, which enables them to regain body condition, remembering that it can take at least a month on good grazing to gain one condition score.

Weaning is best carried out abruptly, removing lambs from the sight and hearing of the ewes. Usually they are moved to aftermath following hay or silage making – although this lush grass can cause problems, as will be seen in the next chapter. Worming at this stage is usual, but the risk of carrying only resistant worms to the new pasture is high if all lambs are wormed and moved immediately. The most recent recommendation is to leave the best lambs untreated so they will carry a small population of susceptible worms to the new pasture. Ewes should be put on bare pasture so their milk dries up as quickly as possible to reduce the risk of mastitis. They should not be deprived of water.

Artificially reared lambs can be weaned from about six weeks of age but must be supplied with creep feed, hay and water from a few days of age. Artificial rearing is expensive, but can be successful if done skilfully, with attention to detail.

Fig. 507 A group of successfully artificially reared lambs that have been weaned. They have creep feed, hay and water available.

Fig. 508 Lambs from hill ewes are unlikely to be ready for slaughter at weaning, so should all be separated and put well away from the ewes.