THE MERCK VETERINARY MANUAL
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Extensive Grazing Systems for Sheep

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Veterinary services for sheep are typically not readily available in the poorer areas of the world unless provided by governments to satisfy exports to other countries. Where veterinary services are available, private practitioners are mostly called upon by extensive grazers that confine their sheep during the colder periods of the year for feeding. Veterinarians are often needed to manage lambing problems such as scours/diarrhea outbreaks, baby lamb mortalities, and other major disease outbreaks. Because predation from coyotes, wild cats, bears, wild pigs, wolves, dingos, etc (depending on the country), usually accounts for the major losses during the rest of the year, private practitioners are generally not a part of flock health and management programs in these systems. However, extensive management systems often use government or university veterinary extension education and services where provided.

Veterinarians can use a request to solve a current problem from such a producer to also educate and advise on flock health. This is more common in extensive grazing units in which sheep are confined during the winter months and so are available for handling and examination. Abortion, still births, weak lambs, and open ewes require accurate diagnosis, and management of these problems can evolve into development of a vaccination program, breeding sounding examinations for rams, looking at mineral and protein supplementation programs, and other preventive programs.

Baby lamb deaths require formal diagnostic aid, which can be used to develop preventive programs for Escherichia coli, coccidia, Mannheimia, white muscle disease, and navel ill. Starvation deaths should lead to examining ewe body condition, preparturient supplementation, mastitis control, and lambing management in general.

Some knowledge of range land nutrition, including toxicities and deficiencies common to the area, feed costs, labor problems, and markets, in addition to knowledge of sheep diseases, is very helpful when giving advice and providing preventive programs and management changes to extensive grazing producers. The aim is to increase net farm income rather than just control disease. Although the diagnosis, treatment, and control of disease are important, an overall management change that will contribute to longterm profitability may be far more important. Net income per hectare/acre should be the major consideration of any recommended change.

A flock health plan, tailored to the specific needs of a large producer, should include: 1) a good mineral/nutritional supplementation program (after determining any deficiencies); 2) control of external parasites (internal parasites may not be a problem on arid ground but that should be determined); 3) prevention of diseases for which cost-effective vaccines are available; 4) methods to prevent introduction of contagious diseases, such as sore mouth/scab, caseous lymphadenitis, footrot, epididymitis/brucellosis, and Johne disease; and 5) improvement of the number of lambs weaned per ewe bred, with enhanced ewe and ram fertility and reduced lamb mortalities (may be related to nutritional program).

In most sheep operations, wool is not the major source of income, so the economic outcome from an outbreak of disease or a serious nutritional problem is usually obvious. However, in operations in which wool is the predominant source of income, a moderate parasite burden or nutritional deficiencies can cause ill-thrift, reduced kilograms of wool shorn per head, and reduced fiber diameter. This outcome may result in a more valuable fleece and thus, no reduction of income. In this situation, reduced health of the ewes may not be obvious. A ewe that does not conceive or aborts in the first 3 mo of pregnancy will produce more wool than a ewe that rears a lamb, because a ewe rearing a lamb has a higher nutritional requirement and produces less wool than a dry ewe. However, in most places, the price of lamb, somewhat influenced by pelt price, is worth far more than that of the wool.

In some areas of the world, veterinarians may be able to go beyond a flock health program by developing a comprehensive flock management advisory service. This service would adopt a whole farm approach that considers the physical and financial resources of the farm/ranch and the interaction of livestock production with other activities such as cropping and pasture production. The stocking rate, type of stock run, timing of husbandry procedures, marketing strategies, and risk management should be reviewed as part of the program. A financial analysis of the farm as a business and preparation of farm budgets and gross margin analyses is a key part of most programs. However, this type of service has not been readily adopted by producers in most places, and most veterinarians do not have the expertise.

Last full review/revision January 2015 by Marie S. Bulgin, DVM, MBA, DACVM

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