Options to Improve Ewe Performance: Animal Health Variables

Summary of paper prepared by Justin Hurst BVSc, Veterinarian, Nufarm Ltd

Contents:

Introduction
Trace Elements
Reproductive Losses
Metabolic Disease
Toxicities
Internal Parasites
Conclusion

Introduction

What animal health variables influence the profit from your ewe flock?

70% of all lamb deaths can be avoided by good ewe and lamb nutrition and preventive measures. Each ewe lost between mating and lambing is equivalent to two ewes wintered and over two lambs tailed.

1. Trace Element Deficiencies
• selenium
• cobalt
• iodine
2. Reproductive Losses
• Toxoplasmosis
• Campylobacter
3. Metabolic Disease
• Pregnancy toxaemia(sleepy sickness)
• Milk Fever
4. Toxicities
5. Internal Parasites

Important animal health management points:

1. Nutrition - quantity and quality of feed is inextricably linked to animal health.
2. Problems property specific and "trial" results are only indicators of trends or potential benefits.
3. Curative action is a cost. Preventative can give returns of 400 to 600 % returns on investment. Animal health management needs to be integrated with annual stock management and the times that losses can occur.

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Trace Elements

Selenium

Signs:

• Infertility due to embryonic mortality 3 to 4 weeks after conception.
• White muscle disease leading to death of lambs, born dead or soon thereafter.
• Ill thrift and poor growth.

Management:

Important times and classes of stock for supplementation are:

• Ewes and rams before mating to improve fertility
• Mid to late pregnancy for foetus and increase in selenium content in milk.
• In growing animals to prevent ill thrift.

Other points:

• Oral and injectable supplementation short acting.
• Controlled release supplementation of ewes best treatment.
• Excess supplementation can be toxic.

Cobalt (Vitamin B₁₂)

Signs:

• Decreased dry matter intakes leading to poor growth rates and wool production.
• Increased peri-natal mortality of lambs.
• Enhanced susceptibility to gastrointestinal parasitism.

Management:

• The efficacy and duration of effect of available cobalt or vitamin Biz supplements is vast.
• Result of the effect of climatic conditions and stock classes on cobalt availability and requirement.
• They include cobalt pasture spray or fertiliser, vitamin 812 injections or cobalt boluses.

Copper

• Not commonly limiting for ewe production.
• Chronic deficiency in association with environmental factors.
• Variation in copper requirement in recently imported breeds, with cases of copper deficiency in pure Finn sheep and copper toxicity in pure Texels.

Iodine

Signs:

• Goitre.
• High lamb mortality and low birthweights.
• Depressed wool production.

Management:

• Oral dosing with potassium iodide.
• Iodised oil injections.

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Reproductive Losses

Toxoplasmosis

Toxoplasmosis is a protozoan infection leading to embryonic loss, abortion, or birth of weak or dead lambs, in immune naive sheep. Infection through ingestion of cysts in the faeces of young or immunosuppressed cats.

Low levels of infection are common (less than 5%), but epidemics can occur in naive flocks with dry/dry rates over 20%. Barren young ewes generally show no other clinical effects but wasting of older ewes has been noted.

Management via live toxoplasma vaccine given once at least four weeks prior to tupping, as well as avoiding feeding supplements contaminated by cats.

Campylobacter

Infection with Campylobacter fetus in the last trimester of pregnancy can cause abortion or lamb death soon after birth. The bacterium are very contagious and spread via contamination of pasture by aborted material or ewe discharges. Management by vaccination (primary and booster vaccinations), and through reducing stock density and isolation of infected animals.

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Metabolic Disease

• Pregnancy toxaemia (sleepy sickness)
• Milk Fever

Occur in late pregnancy - caused by faults or changes in the nutritional management of the flock. Can be confused with superphosphate poisoning. Treatment by injection of calcium borogluconate, and oral energy solutions (propylene glycol) with Vitamin B₁₂ and Iodine for sleepy sickness. Must be given early.

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Toxicities

• Sporedesmin
• Zearalenone
• Ryegrass endophyte
• Phyto-oestrogens

Effect ewe profitability through reduction in fertility at mating - liver damage ( Facial Eczema) may effect lifetime performance. Diagnosis difficult, management based on avoidance of known susceptible pastures and genetic resistance.

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Internal Parasites

Gastrointestinal parasites are potentially the most significant production limiting disease in sheep. Includes reduced feed intake, reduced wool and milk production, as well as increased bodyweight loss and reduced lamb weight at birth.

Profitable ewe farming requires Parasite Management, not just Worm Control. Why?

Two recent changes in our thinking involve the effect of different stock classes on pasture contamination, and our ability to determine if pasture is "safe".

Young stock will always have higher FEC's - ewe flock contributes up to half the total egg output on a farm, due to their higher faecal output.

Sources of parasite egg contamination of pastures.

Controlled release and persistent action anthelmintics has allowed management of the direct cost of internal parasites to the ewe as well as having an affect on lamb survivability and production. With the prolonged action ofCRC many or all of the benefits of parasite management around parturition can be obtained. Potential benefits for lactation in high fecundity ewes, leading to significant increases in lamb weight weaned per lactating ewe.

Prolonged action anthelmintics may be indicated around lambing where ewe bodyweight/condition less than optimal.

Timing of the peri parturient rise in faecal egg output, (or reduction in ewe immunity) is variable between years and age classes. High FECs may occur throughout winter, particularly in young stock. Preventing the effect of parasitism pre lambing has been shown to be able to influence lamb birthweight and survivability, hence ncreasing kilograms of lambs weaned per hectare.

 

Effect of time of albendazole CRC treatment of Merino ewes on lamb survival

(adapted from Mulvaney 1997)

	Property A			Property B
No. days prelambing of treatment	-65	-37	-14	-48	-35	-16
Lamb survival %	87.5	86.5	78.5	77.1	61.9	52.9

To determine if intestinal parasites are limiting ewe production the following factors should be considered:

• ewe C/S
• potential lamb drop
• potential nutrition
• ewe FEC
• FEC and type other stock
• pasture "safety" assessment

Anthelmintic use as a one off event should include nutrition, body condition, trace mineral status, and stocking rate as well as Faecal Egg Count data. Long term productivity benefits or costs (resistance and immunity development) need to be considered and traded off against current financial considerations and farm goals.

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Conclusion

Animal health must be preventative and needed to give excellent returns on investment. Through careful planning and monitoring, including selection of time and classes of stock to be treated and use of whatever "safe" pasture that can be created, major benefits of parasite management can be achieved with minimal effect on farm worm resistance status.

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