PATHOLOGY - Lamb Ill Thrift

Question 1

What is ill thrift?

Answer 1

Ill thrift is the failure to maintain condition and bodyweight or failure to grow as expected

Question 2

What are the three main lambing systems in the UK?

Answer 2

Spring lambing flocks
Early lambing flocks
Store lambs

Question 3

Describe briefly the timeline for a spring lambing flock

Answer 3

Spring lambing flocks lamb in the spring and thus lambs tend to be put out to pasture with their mothers within a few days of life. The lambs are then usually finished and sold in the autumn when the price will be the lowest (as there will be the most plentiful lambs at this point in the year)

Question 4

Describe briefly the timeline for early lambing flocks

Answer 4

Early lambing flocks lamb in December/January and thus lambs tend to be kept inside until weather and pasture conditions improve. The lambs are then usually finished and sold in the spring when the price will be the highest

Question 5

What are store lambs?

Answer 5

Store lambs are lambs bought in the autumn to be finished and sold

Question 6

Why is efficient lamb growth so important?

Answer 6

Efficient lamb growth is so important as the longer lambs are on the farm, the more resources they will use, however if they are finished and sold at an optimal time there will be more resources left for the ewes to help prepare them for the next lambing season (such as grass, feed, decreased housing pressure etc), and there will be reduced PGE and fluke problems. Furthermore, the earlier lambs are sold, the higher price they will be sold for at market and the better growth rates they have the better the meat quality will be at slaughter

Question 7

What is the target daily live weight gain for lowland lambs pre-weaning?

Answer 7

300g/day

Question 8

What is the target daily live weight gain for lowland lambs post-weaning?

Answer 8

200g/day

Should be aiming for 250g/day if finishing on grass

Question 9

What is the target daily live weight gain for hill lambs pre-weaning?

Answer 9

240g/day

Question 10

What is the target daily live weight gain for hill lambs post-weaning?

Answer 10

200g/day

Should be aiming for 250g/day if finishing on grass

Question 11

What are the benefits of regularly weighing lambs?

Answer 11

Regularly weighing lambs allows for the monitoring of growth and daily liveweight gain, and weighing at specific points in their development can help to identify potential factors involved in altering growth rates and thus help to make more informed management decisions

Question 12

At which points should lambs ideally be weighed?

Answer 12

Birthweight
8 weeks old
Weaning
Fortnightly post-weaning

Question 13

What is the target birthweight for lambs?

Answer 13

4.5 - 6.5kg

Question 14

Which main factors can influence lamb birthweight?

Answer 14

Ewe nutrition during late gestation
Ewe disease status during gestation
Genetics

Question 15

What is the target weight for lambs at 8 weeks old?

Answer 15

20kg

Question 16

Which main factors can influence lamb weight at 8 weeks old?

Answer 16

Ewe nutrition during late gestation and lactation
Ewe lactation performance
Ewe mothering performance
Ewe disease status
Ewe management

Question 17

Why is ewe nutritional status so important to lamb growth rates pre-weaning?

Answer 17

Ewe nutritional status has a direct effect on the birthweight and vitality of the lambs as well as the quality and quantity of the colostrum and milk produced which is the most energy dense feed a lamb will receive. Thus, grass and pasture management, as well as maintaining BCS with adequate nutrition is essential for for ewe nutrition and milk production

Question 18

What is the target weight for lambs at weaning?

Answer 18

Minimum weight of 16kg but ideally over 25kg

Question 19

At what age are lambs weaned?

Answer 19

Lambs are typically weaned after 12 weeks old (as this is when they become less reliant on milk)

Question 20

(T/F) There is expected to be a drop in weight at weaning in lambs

Answer 20

TRUE. There is expected to be a drop in weight and daily liveweight gains at weaning as lambs are no longer reliant on energy dense milk, however this decline should be temporary

Question 21

What is indicated by a persistent decrease in weight and daily liveweight gains in lambs at weaning?

Answer 21

A persistent decline in weight and daily liveweight gains in lambs at weaning indicates they were weaned too early

Question 22

What is indicated by a large increase in weight and daily liveweight gains in lambs at weaning?

Answer 22

A large increase in weight and daily liveweight gains in lambs at weaning can indicate weaning was done too late, and the lambs had started to compete with the ewes for nutritional resources

Question 23

When would delaying weaning be appropriate?

Answer 23

Delaying weaning would be appropriate if there is plenty of good quality grass available for both the lambs and ewes so they don’t have to compete for nutritional resources. Furthermore, delayed weaning reduces parasite challenge for the lambs as the ewes essentially ‘hoover’ up some of the larval challenge

Question 24

When would early weaning be appropriate?

Answer 24

Early weaning would be appropriate if there is limited grass available for the ewes and lambs to prevent competition for nutritional resources, as the lambs will be overcompeted by the ewes and their growth rates will decline

Question 25

What are the main influences on lamb weight post weaning?

Answer 25

Lamb nutrition Disease status

Question 26

What is the daily dry matter (DM) intake for lambs?

Answer 26

2.5 - 3.5% of their bodyweight

Question 27

What can lambs consume to reach their target dry matter intake?

Answer 27

Milk Grass Forage crops Concentrates ## Footnote Be aware that lambs will become less reliant on milk and thus the other factors are very important

Question 28

What are the potential causes of nutritional deficits and consequently poor nutrition in lambs?

Answer 28

Poor milk yield and quality Poor ewe management Poor quality pasture Inadequate grass length Unpalatable feed Inadequate feed face space Inadequate lying space to ruminate Lack of fresh, clean water that is readily available and easy access

Question 29

What is the minimal feed face space for lambs?

Answer 29

0.3m per lamb

Question 30

What is the minimal space required for lambs to lie down and ruminate?

Answer 30

0.9m^2 per lamb

Question 31

What is the optimal pasture length for lambs?

Answer 31

5 - 8cm

Question 32

Which techniques can be used to optimise pasture quality?

Answer 32

Rotational grazing and maintenance of clover can be used to optimise pasture quality and consequently lamb nutrition as this allows the pasture adequate time to recover from grazing and allow for a high proportion of nutritious plants on pasture

Question 33

What are the main causes of ill thrift in pre-weaning lambs?

Answer 33

Nutritional deficits Parasitic gastroenteritis (PGE) Nematodirosis Coccidiosis Lameness Prolonged effects of neonatal disease

Question 34

Which two diseases arise in lambs in the spring?

Answer 34

Nematodirosis and coccidiosis both arise in the spring and cause very similar clinical signs, furthermore these parasites can cause co-infection resulting in more severe clinical signs than either diseases on their own

Question 35

Describe the epidemiology of coccidiosis in sheep and lambs

Answer 35

Adult sheep cycle and shed low numbers of Eimeria oocysts, contaminating the environment. Eimeria is always present within a flock however the adults have developed immunity and thus clinical disease is only seen in naive animals. Naive lambs early in the lambing season will ingest the oocysts shed by the adults and augment the contamination through shedding larger quantities of oocysts into the environment. However, these lambs are generally not exposed to a high enough infection pressure to develop clinical disease, so they develop immunity without showing clinical signs. However, lambs born later in the lambing season will be exposed to higher infection pressures and thus are more likely to develop clinical disease. This usually occurs when these lambs reach 3 weeks old due to the prepatent period of eimeria, although clinical disease can be seen in lambs sold and moved to a new farm (i.e. store lambs) where they can be exposed to a new species of Eimeria and develop clinical disease as the acquired immunity is species specific

Question 36

What is the pre-patent period (PPP) for eimeria?

Answer 36

3 weeks

Question 37

What are the risk factors for coccidiosis?

Answer 37

Lambs born late in the season Lambs 3 to 8 weeks old Lambs moved to a new farm Poor hygiene (specifcally wet, faeces accumulated areas) Short grass

Question 38

Why is poor hygiene a risk factor for coccidiosis in lambs?

Answer 38

Oocysts survive well in wet, cool conditions where faeces has accumulated

Question 39

Why is short grass a risk factor for coccidiosis in lambs?

Answer 39

Short grass causes lambs to graze closer to the ground where eimeria oocysts accumulate

Question 40

What are the clinical signs of acute coccidiosis in lambs?

Answer 40

Dark, mucoid diarrhoea ± blood Dehydration *(this is what kills the lambs)* Abdominal pain Anorexia Ill thrift/weight loss Depression

Question 41

What are the clinical signs of chronic coccidiosis in lambs?

Answer 41

Chronic ill thrift and poor growth rates

Question 42

What causes chronic coccidiosis?

Answer 42

Chronic coccidiosis is caused by long term damage to the intestines due to eimeria infection

Question 43

How do you diagnose coccidiosis in lambs?

Answer 43

History (grazing, management etc.) Clinical signs Faecal oocyst counts Response to treatment Post mortem

Question 44

Why are faecal oocyst counts so challenging to interpret in lambs?

Answer 44

Faecal oocyst counts are very challenging to interpret in lambs as there are many species of Eimeria that can infect lambs however only a small proportion of these species are pathogenic, and you have to have a very high oocyst count in combination with appropriate history and clinical signs to have a suspective clinical diagnosis. Furthermore, make sure to sample from several animals within the group as clinical signs can begin before oocyst shedding

Question 45

What is required for definitive diagnosis of coccidiosis?

Answer 45

Speciation to determine if the Eimeria is pathogenic

Question 46

What are the limitations of speciation to diagnose coccidiosis in lambs?

Answer 46

It takes several days to get speciation results back and by that points lambs will have started to die, so you have to treat based on a suspective diagnosis however the speciation results can be used to help guide future prevention

Question 47

What are key post mortem (PM) features that can be used to diagnosis coccidiosis in lambs?

Answer 47

Merozoites in smears from intestines of freshly dead animals Histopathology of intestines from freshly dead animals ## Footnote Have to collect sample within 20 mins of death due to rapid autolysis of the intestinal mucosa

Question 48

How can you treat acute coccidiosis?

Answer 48

Fluid therapy (usually oral unless high value lamb) Anti-inflammatory drugs Remove lambs from source of infection Anticoccidial drugs | Treat all lambs in the group with anticoccidial drugs

Question 49

What are the anticoccidial drugs licensed for sheep in the UK?

Answer 49

Toltrazuril Diclazuril

Question 50

What is the main difference betwen toltrazural from diclazuril?

Answer 50

Toltrazuril treats all stages of eimeria infection so only has to be administered once, however diclazuril only treats the later stages of disease to needs to be repeated 2 weeks after initial adminstration

Question 51

Why are sulphonamides not a recommended treatment for coccidiosis?

Answer 51

Some vets use sulphonamides in the treatment of coccidiosis in lambs, however sulphonamides are coccidiostatic and thus eimeria will resume their lifecycle as soon as treatment is ceased and clinical disease will arise

Question 52

How can you prevent coccidiosis in lambs?

Answer 52

Muck out sheds regularly Avoid dampness in sheds Rotational grazing Keep lambs born later in the lambing season in different sheds/pasture Seperate age groups Decrease stocking density Maintain optimal pasture height Preventative anticoccidial drugs

Question 53

What is decoquinate?

Answer 53

Decoquinate is a coccidiostatic drug which can be put into the ewes feed prior to and after parturition to decreased environmental contamination and thus exposure of naive lambs to oocysts. Decoquinate can also be used to treat lambs however it has to be used for 28 days due to being coccidiostatic to prevent the eimeria lifecycle from resuming

Question 54

When are preventative coccidiocidal drugs appropriate?

Answer 54

Coccidiocidal drugs (such as toltrazural and diclazuril) can be used preventatively in lambs that have been moved to a high risk area for coccidia. Administer these drugs pre-emtively 2 weeks after the lambs have been moved

Question 55

What is one of the main limitations of preventative anticoccidial drugs?

Answer 55

Preventative anticoccidial drugs may prevent lambs from developing an immune response

Question 56

What are the main causes of ill thrift in post-weaning lambs?

Answer 56

Nutritional deficits Mineral deficiences Parasitic gastroenteritis (PGE) Liver fluke Lameness Prolonged effects of neonatal disease

Question 57

Which mineral deficiencies have the most profound effect on growth rates in post-weaning lambs?

Answer 57

Cobalt deficiency Selenium deficiency

Question 58

What is the function of cobalt?

Answer 58

Cobalt is required by ruminal microbes to synthesise vitamin B12 which is essential for metabolism

Question 59

What are the risk factors for cobalt deficiency in sheep?

Answer 59

Soil type Geographical location Dry weather Fast growing pasture Low amount of clover on pasture

Question 60

What are the clinical signs of cobalt deficiency in pregnant ewes?

Answer 60

High perinatal lamb mortality Reduced milk yield

Question 61

What are the clinical signs of cobalt deficiency in lambs?

Answer 61

Watery ocular discharge Unkempt fleece Anaemia Diarrhoea Anorexia Poor growth rates/ill thrift Hollow sublumbar fossa Hepatic encephalopathy (due to ovine white liver disease)

Question 62

How can you treat cobalt deficiency?

Answer 62

Injectable vitamin B12 to promote appetite followed by other methods of supplementation such as repeated injectable vitamin B12 or oral supplementation if the pasture is cobalt deficient

Question 63

What are the clinical signs of selenium deficiency in lambs?

Answer 63

Poor growth rates/ill thrift Impaired immunity

Question 64

What are the clinical signs of selenium deficiency in adult sheep?

Answer 64

Reduced fertility Weak lambs born White muscle disease

Question 65

How can you treat selenium deficiency?

Answer 65

Injectable selenium Oral supplementation | Be careful as overdosing selenium can be toxic

Question 66

How do you diagnose mineral deficiencies in post-weaning lambs?

Answer 66

History (grazing, weather etc.) Clinical signs Soil/pasture testing Serum mineral levels Liver biopsy (as these minerals are stored in the liver, indicates more long term deficiencies) Post mortem

Question 67

How does liver fluke affect lamb growth rates?

Answer 67

Liver fluke in ewes can cause poor ewe BCS which will result in low lamb birthweight and poor colostrum and milk production which will consequently affect lamb growth rates. Liver fluke in post-weaning lambs can cause direct ill thrift and poor growth rates

Question 68

How does lameness affect lamb growth rates?

Answer 68

Lameness in ewes can cause poor ewe BCS which will result in low lamb birthweight and poor colostrum and milk production which will consequently affect lamb growth rates. Lameness in pre-weaning and post-weaning lambs can cause direct ill thrift and poor growth rates