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Health and Management Practices on US Sheep Operations

11 August 2014

USDA

Producers sometimes inadvertently bring disease onto their operations by adding new animals to their flock.

US sheep reportAbout one-third of US sheep producers minimised their risk of acquiring new disease in their flock by not adding new animals, other than by natural birth, according to the USDA report Health and Management Practices on US Sheep Operations, 2011, which was recently released.

The longer an operation goes without adding animals, the higher the certainty that no asymptomatic, but infected, animals exist in the flock.

Operations that did not add sheep during 2010 were considered “closed” flocks.

On average, rams had not been added to closed flocks for 3.7 years, while ewes and lambs had not been added to closed flocks for 9.0 and 8.4 years, respectively.

Reproduction management

An accurate annual estimate of the actual lamb crop is an important measurement of flock productivity.

Nearly all operations can provide their lambing rate, but it is not always clear how the rate is measured. For some operations in the largest lamb producing States (especially range flocks), the pre-docking period is an enigma.

Therefore, their lambing rate is based on the number of lambs docked divided by the number of ewes bred. This method has its limitations.

For these operations, the entire period from lambing to docking cannot be examined to determine whether the majority of lambs are lost to predators, a lack of colostrum, poor mothering, scours, pneumonia, or other causes.

Losses are difficult to prevent if the cause of loss remains unknown.

Nearly half of all operations (47.3 per cent) calculated the lambing rate by determining the number of lambs born divided by ewes bred.

Over half of large operations (54.9 per cent) determined lambing rate by estimating the number of lambs docked divided by the number of ewes bred.

The producer-expected lambing per centage overall was 1.50.

Small and medium operations had a higher expected lambing rate (1.53 and
1.47, respectively) than large operations (1.23).

Controlled internal drug release (CIDR) devices were approved for use in the United
States in 2009.

Overall, 6.7 per cent of operations used CIDRs in 2010, and 95.6 per cent of these operations would use them again.

Three quarters of operations that used CIDRs used them for out-of-season breeding.
Placentas can harbour infectious organisms and should be removed as soon after lambing as possible.

Removing placentas is especially important on high-density operations in which ewes are clustered and exposure to placental organisms is high.

In general, 67.9 per cent of operations usually removed placentas from the lambing area.

Composting and throwing out for carnivores were the two most common methods for disposing of placentas (30.8 and 28.0 per cent of operations that removed placentas, respectively).

Diseases and Control Methods

Nearly all operations (92.0 per cent) had an APHIS-assigned flock identification number.

Overall, producers on 84.8 per cent of operations were either very or somewhat familiar with scrapie.

Of these, about half (47.3 per cent) implemented genetic selection for scrapie control, and of these almost all (98.8 per cent) used replacement rams genetically less susceptible (RR alleles) to scrapie.

Toxoplasmosis and coxiellosis (Q fever) are common causes of abortion storms in sheep flocks, yet producers on 28.5 and 52.0 per cent of operations had not heard of toxoplasmosis and Q fever, respectively.

Vaccines can reduce the prevalence or severity of disease and are an integral part of any flock management programme.

Overall, 81.6 per cent of operations used vaccines in 2010.

The highest percentage of operations vaccinated against enterotoxemia and tetanus (71.4 and 64.5 per cent of operations, respectively).

A higher percentage of herded/open range flocks vaccinated for sore mouth compared with other flock types.

Because the sore mouth vaccine is comprised of live virus, vaccinating against sore mouth is only recommended when a flock is already infected with the virus.

The highest percentage of operations that vaccinated for sore mouth (70.6 per cent) used a commercially available sore mouth vaccine.

Antibiotic Use

Record keeping is an essential part of responsible antibiotic use. Records should include the name of the antibiotic used, animals treated, date treated, and reason(s) for treatment.

During 2010, 69.0 per cent of operations administered oral, injectable, or topical antibiotics to lambs or ewes to treat any disease.

Just over half of operations that administered antibiotics (51.0 per cent) kept antibiotic-usage records.

The most commonly treated illness on sheep operations was respiratory disease; for operations that gave any antibiotics, 67.7 per cent treated sheep for this illness during 2010.

The antibiotic class used most frequently to treat respiratory disease was penicillin (29.9 per cent of operations), followed by tetracycline (19.2 per cent) and florfenicol (13.6 per cent).

Further Reading

You can view the full report by clicking here.

June 2014

 

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