Choosing breeds for producing profitable market lambs

Introduction

The Ontario sheep industry has yet to determine an optimum production system for profitability or what specific breeds and breed crosses will result in the most profitable enterprise to produce today’s premium lamb under Ontario conditions.

New entrants to the industry are faced with many breeds to choose from and little objective data. As a result, it is important for producers to have a strong business plan formulated before choosing breeds.

When starting in the sheep industry, it is important to determine the production system and the market product for the business before choosing the breed or breeds of sheep that will be used in the operation. It is much easier to evaluate the resources of the business operation, choose a production system, then choose a breed of sheep that will fit that system than it is to try to fit a breed into a production system that the breed was not designed for.

Production systems

The two main commercial production systems in Ontario are annual spring lambing and accelerated lambing.

Annual spring lambing

Annual spring lambing is an extensive, low-cost production system based on having a large flock that lambs when the highest feed requirements of the flock can be met using pasture. Profitable annual lambing enterprises:

• lamb once a year in April or May to maximize the use of grass and the conception rate and fertility of the ewes
• rely on hardy breeds or breed crosses with the following traits:
  • very strong mothering ability
  • excellent foraging ability
  • medium fecundity (lambing percentage)

Accelerated lambing

Accelerated lambing is a more intensive system based on prolific ewes and high production that aims to produce market lambs and cash flow throughout the year. Profitable accelerated lambing enterprises:

• lamb 3–5 times a year, timed to take advantage of best months for conception and fertility of ewes, maximizing use of pasture and use of buildings
• rely on prolific breeds or breed crosses with the following traits:
  • high fecundity (lambing percentage)
  • early maturity
  • extended breeding season

Common breeds

The most popular breeds tested in Ontario on the genetic evaluation program are Polled Dorset (Figure 1), Suffolk, Rideau Arcott and their crosses. These same breeds have the highest registration numbers both in Ontario and Canada (Table 1).

The benefit of choosing among the common breeds to start a flock is general availability and more accurate average performance information, resulting in more animals available for purchase and more choice among breeders.

Source: Canadian Sheep Breeders Association 2010

Breed performance

It is important to have good, expected average performance information when choosing breeds and formulating a business plan. Table 2 lists information on many breeds. Note that a number of breeds are only represented in one flock by very few ewes. As a result, the performance listed for breeds with little data may not be an accurate indication of average breed performance.

Crossbreeding

A profitable commercial sheep operation should take advantage of the benefits of crossbreeding.

Crossbreeding increases the efficiency of the operation by crossing two breeds that have high genetic merit for different traits. Maternal traits or reproductive traits tend to be negatively correlated to terminal, or growth and carcass traits — an animal that has more lambs born and more milk will tend to be less muscular, with poorer feed conversion and gaining ability.

It is difficult, if not impossible, to produce a sheep that is exceptional in both maternal and terminal traits, which is why there isn’t a sheep breed that has as many lambs as a Romanov and is as muscular as a Texel. This means that it is most efficient to use breeds with excellent maternal traits for the ewe flock and breed those ewes with rams from breeds that have excellent growth and carcass traits (Figure 2).

Ewe flock

In general, the ewe flock should be made up of medium-to-small ewes with good reproductive traits, rather than large ewes that grow fast. This helps control the largest cost for the enterprise — the feed cost. Larger ewes cost more to feed per year than smaller ewes.

Approximate ewe weight ranges are:

• small: 50–65 kg (110–145 lb)
• medium: 65–80 kg (145–175 lb)
• large: 80+ kg (175+ lb)

Plan ahead to maintain the maternal ewe flock in a crossbreeding program. Use rams of the same breeding as the ewes to produce replacement females and maintain the benefit of crossbreeding.

Examples of maternal breeds

• Prolific: Finn, Rideau, Polpay, Romanov, Outaouais
• Hardy: North Country Cheviot, Border Leicester
• Extended Season: Dorset, Finn, Rideau, Polypay, Romanov, Outaouais, Corriedale, Rambouillet, Columbia

Market lambs

Crossbreeding can be used to adjust the growth rate and size of market lambs. Choose a terminal sire breed to complement the ewe flock and produce the best carcass and growth rate for the production system and chosen target market.

Ontario has a market for several different weight classes of lamb. Send lambs to market when they have an optimum level of finish or carcass fat. The proportion of carcass fat is different between breeds and sexes but is most affected by degree of maturity or percentage of mature weight at slaughter.

Research conducted by Dr. Eric Bradford of the University of California in 2002 suggests that lambs should be marketed at a maximum of 60%–70% of the average of the mature weights of the ewes of the sire and dam breeds to avoid overfatness. The American Sheep Industry Association defines lean lamb as having a backfat thickness over the rib eye muscle between the 12th and 13th ribs of 2.54–6.35 mm (0.10–0.25 in.).

The American market prefers a slightly fatter carcass than markets in Ontario. As a result, in Ontario a maximum of 50% of the average of the mature weights will work better.

Tables 3 and 4 provide a guide to approximate slaughter weights based on the mature size of the ewes of the breed. The tables were developed using ewe and wether information on diets relatively high in energy. Use Table 3 for weights in pounds and Table 4 for weights in kilograms.

SBMW

sire breed mature weight

Target slaughter weight = ((sire breed mature wt. + ewe breed mature wt.)/2) x .50

Using the chart

If the production plan is to produce 90-lb lambs for the light lamb (80–94 lb) market, and the average mature weight of your ewes is 160 lb, use a ram breed whose ewes average 200 lb.

Estimates of average mature ewe weights for some U.S. breeds

• 104.4 kg (230 lb) - Suffolk
• 95.3 kg (210 lb) - Hampshire
• 90.7 kg (200 lb) - Columbia
• 81.7 kg (180 lb) - Dorset, Lincoln, Oxford, Shropshire
• 77.1 kg (170 lb) - Border Leicester, Corriedale, Dorper, East Friesian, Montadale, Romney, Targhee
• 72.6 kg (160 lb) - North Country Cheviot, Polypay, Rambouillet, Texel
• 68 kg (150 lb) - Coopworth, Romanov, Southdown, Tunis
• 63.5 kg (140 lb) - Cheviot, Clun Forest, Finnsheep, Katahdin, Merino, Perendale, St. Croix
• 59 kg (130 lb) - Cheviot, Scottish Blackface
• 54.4 kg (120 lb) - Barbados, Karakul
• 49.9 kg (110 lb) - Jacob
• 40.8 kg (90 lb) - Shetland

Remember that the average performance of the progeny will be approximately the average performance of the two parents. The growth rate of market lambs can be easily improved by using a fast-growing terminal sire.

For example, a Finn sheep ewe flock with an average growth rate of 0.25 kg (0.55 lb)/day crossed with a Suffolk terminal sire with a growth rate of 0.50 kg (1.1 lb)/day would have progeny that have an average growth rate of 0.375 kg (0.83 lb)/day.

Examples of terminal breeds

Canadian, Charollais, Southdown, Texel, Oxford, Hampshire, Suffolk, Ile de France

Replacement ewe lambs

In using breeds effectively, it is also important to consider how replacement ewe lambs will be produced. If they will be produced from within the flock, do not keep ewe lambs sired by the terminal sire. To sire ewe lambs kept in the flock, a ram must be chosen for his reproductive traits to ensure that the maternal reproductive traits are maintained. Otherwise, the maternal traits of the ewe flock can be lost over time.

For example, a Finn ewe flock may have an average of 2.5 lambs per lambing and the Suffolk sire’s dam may have an average of 1.6 lambs per lambing. The replacement ewe lambs as adults would have an average of 2.05 lambs per lambing and a larger mature body size than the Finn ewe flock. After a few generations, the ewe flock will no longer be specialized and could have very different maternal traits than originally intended.

SBMW

Sire breed mature weight

Target slaughter weight = ((sire breed mature wt. + ewe breed mature wt.)/2) x .50

Heterosis

Crossbreeding also results in heterosis — an increase in the performance of progeny compared to the average of the parents. This means that if a sire and dam, of different breeds, both gained 0.50 kg (1.1 lb)/day, the average gain of the progeny might be 0.55 kg (1.2 lb)/day.

Remember that if the two parental breeds are not similar in performance for a trait, the lamb will not be better than both parents, it will only be better than the average of the two parents.

For example, a growth rate of 0.25 kg (0.55 lb)/day crossed with a growth rate of 0.50 kg (1.1 lb)/day might only result in lambs with an average of 0.40 kg (0.88 lb)/day, which is better than the average of the parents (0.375 kg (0.83 lb)/day). In the literature, positive heterosis effects have been reported consistently for pre-weaning survival and growth traits. There is little evidence of any heterosis effect on carcass traits. The small heterosis effects on different traits when using crossbred lambs accumulate and can result in significant differences in overall productivity.

Conclusions

It is most important to formulate your farm business plan and choose your production system before deciding what breed or breeds of sheep will best fit your operation. The best breed of ewe will be a small- to medium-sized ewe that will produce the most efficiently to fit your production system. The most efficient system will make use of crossbreeding and use one breed of sire to produce replacement ewe lambs for the flock and a different breed of sire to produce market lambs.

References

Bradford, G.E. 2002. Relationships Among Traits: Growth Rate, Mature Size, Carcass Composition and Reproduction. Sheep and Goat Research Journal 17:38–41.

Leymaster, K.A. 2002. Fundamental Aspects of Crossbreeding of Sheep: Use of Breed Diversity to Improve Efficiency of Meat Production. Sheep and Goat Research Journal 17:50–59.

Thomas, David L. Breeds of Sheep in the U.S. and Their Uses in Production. Article. December 23, 2008.

This factsheet was written by Delma Kennedy, Sheep Specialist, OMAFRA.