Lambing is typically an annual affair. For most sheep breeds, the autumn brings about the natural mating season. Lambs arrive in the spring, when grass is greening up, providing a plentiful diet. But commercial sheep production requires a year-round supply of lambs, and accelerated lamb production methods can make it feasible for producers to fulfill those needs.
An accelerated system is one in which the birth interval is decreased to less than a 12-month cycle, Richard Ehrhardt, Ph.D, Small Ruminant Specialist at Michigan State University said.
Ehrhardt discussed two primary methods of accelerated production in a recent webinar, “Accelerated Lamb Production: An Opportunity to Build Markets and Increase Production Efficiency.”
With more than one lambing season each year, a farm can provide both large animals for the traditional market, as well as smaller 50 pound “roasters” for the ethnic market. The accelerated method also offers producers a cushion against market pricing fluctuations, and allows the establishment of new markets, ones which require product availability throughout the year, he said.
Producers who are able to maintain a rate greater than 1.3 lambs marketed per ewe per year, in an annual system, are candidates for transitioning to an accelerated program.
“It’s unlikely this (accelerated) system is going to be a profitable option,” if that rate isn’t being met in an annual program, he said.
The accelerated systems are management-intensive, and require a greater initial investment in infrastructure. Because lambing will occur during cold weather, a barn with good ventilation and climate control, large enough to house about 2/3 of the flock, is advised. The ability to feed to a higher plane of nutrition throughout the year, as the sheep are working harder, and very good control of chronic diseases, which become more emphasized in accelerated herds, are necessary.
“The diet is very important in maintaining good out of season breeding success,” he said. “Continue feeding these accelerated animals as if they are in early lactation. It is possible to get ewes to breed during lactation, but it’s hard to sustain over a multi-year period. Nutrition management is important.”
In field observation, Ehrhardt reports that poor quality forages limit the dry matter intake, which in turn limits the ability for the ewes to breed out of season, impacting the spring conception rate. Neutral detergent fiber content and digestibility, as well as starch content, seem to be limiting factors.
Accelerated programs have 41 percent greater ewe productivity over annual breeding systems. Ewe replacement rates will be slightly higher, primarily due to issues with mastitis, as a direct result of increased days of milk. Studies from Canada, where accelerated production is more common than in the United States, have shown that an “accelerated system isn’t more expensive” and results in a greater net income per ewe, per lamb, per unit labor, and on an enterprise basis, Ehrhardt said.
Two accelerated programs
Ehrhardt discussed the STAR program, developed by Brian Magee and Doug Hugue, from Cornell, in the 1980s, as well as the eight-month program. The STAR program features five lambings in three years, with ewes lambing every 7.2 months, while the eight month accelerated program has three lambings in two years. In both of these systems, the flock is divided into two management groups. Ewes in late pregnancy or lactation are in one group, and ewes exposed to rams or in early pregnancy are in another.
In the STAR system, the lambing and breeding periods are synchronized, but the lactation period is variable. There is a 30-day lambing period, a 30-day breeding period, and a variable lactation period of 43-73 days. Lambs weaned at 43 days can be a management difficulty, he said.
“What’s important to understand about the Cornell STAR system is it is a market-driven system. It’s all about creating a consistent marketing capacity of lamb,” Ehrhardt said.
With the eight month system, producers can target specific holidays when lamb demand is high, or plan for labor availability, he said. It provides ewes with more time to recover, and breeding periods can be lengthened beyond 30 days. Unlike the STAR system, however, a ewe who is not bred will have to wait 120 days for the next breeding period. In the STAR system, there is only a 72 day period between breeding times.
Increasing breeding success
There are numerous tools which producers can use to enhance an accelerated program. Manipulating the amount of light, in order to mimic the natural fall breeding pattern, as well as using hormones to increase successful out-of-season breeding, are two such methods. The Food and Drug Administration has approved the use of progesterone to increase the likelihood of spring breeding, as well as to synchronize breeding.
Light priming involves manipulating the amount of light exposure. In Canada, at CEPOQ, Quebec’s research center for sheep production, sheep are exposed to alternating four-month light intervals, convincing them that it is October, and time to breed, no matter what season it really is. Sheep are exposed to eight hours of dark, and 16 hours of light, alternating with the 16 hours of dark, and eight hours of light.
It is a “very effective,” but intensive and expensive management system, Erhardt said. “Whether or not this is profitable enough is an arguable point.”
Another system of photo-manipulation is an extended daylight system. In this protocol, sheep are exposed to 24 hours of light for 60 days, then receive barn ambient light only, for another 60 days. If this is done during the winter months when “these ewes are already in your barn being fed,” it requires no special management other than the lighting. Rams are introduced at the end of the ambient light period. This method has shown a large increase in aseasonal conception rates among flocks of seasonal ewes.
Another concern with aseasonal breeding is insuring male libido out of season. Increasing feed to 40 percent over maintenance levels, using light priming as for ewes, and selecting the best breeds are important.
Not all sheep breeds can be aseasonal in fertility. Horned Dorset, Merino, Finn, Romanov, Rambouillet and hair breeds of West African descent are the best for aseasonal production. Some of these breeds are naturally aseasonal, originating near the equator, where day length is not as variable. Other breeds have been genetically selected for aseasonal fertility. Cross breeding increases aseasonality, Ehrhardt said.
Accelerated systems are not for everyone. The desire to highly manage the flock, and the ability to do so, is critical. Factors to consider before beginning an accelerated program include your land value, the quality of your forage — whether it is grazing or machine-harvested, the labor available during various lambing periods, the need for a well-insulated barn, and flock genetics. While an accelerated system will require more initial costs, higher productivity will mean that a well-managed accelerated program will have lower fixed costs per lamb, over time.
“It is just one of a number of strategies to improve the efficiency of sheep production,” he said.