Mike Neary, Extension Sheep Specialist, Purdue University
(Previously published on the Purdue University Extension web page)
The purpose of this 
article is to examine the pros and cons of each system and how they can fit individual producers goals and operations. Neglected in this discussion is fall lambing, which is not an attempt to minimize this as a viable management system. Fall lambing is viable, with the proper genetics and feed resources.
Early or Winter Lambing
Early lambing systems have some definite advantages over other systems. High on the list is labor availability. Many farmers don’t have as many demands on their time during winter as they do during spring. Fieldwork, planting, calving, etc., are all time-consuming and high input periods. There simply may not be enough time to lamb out a bunch of ewes. This is a real and practical consideration, since the lambing season is the highest labor input of the sheep production year.
Another advantage is that historically, lambs reached the highest price of the year during the Easter period. Lambs born during the winter had a good chance of fetching a higher price than those born around Easter. However, this has not been the case the last 3 to 5 years. Prices have not been appreciably higher in the spring and in some years, have actually been lower. Thus, this advantage has been diluted somewhat.
Those producers that winter lamb can usually carry more ewes on their pastures, since their feed requirements are only at the maintenance level. Also, lambs don’t compete for a possible limiting resource; pasture.
Certainly, those producers that raise purebred breeding stock or lambs for youth projects will continue to lamb in the winter. The scheduling of shows favor an older, larger individual to be competitive.
A successful winter lambing system must have some important characteristics. Of primary concern is reproductive performance. Ewes must be genetically able to cycle and conceive for early lambs. Not all ewes are capable of this. Ewes must give birth to and wean more than one lamb to have a positive financial return. There are simply too many feed, housing, and labor inputs to spread out over just one lamb. Commercial sheep producers that winter lamb need to be marketing around a 160-200% lamb crop to make money.
If lambing occurs during winter, then adequate facilities need to be available. Housing is, of course, a big consideration. An area for ewes to drop lambs, lambing pen area, several mixing areas for ewes with young lambs and an area for ewes that are not close to lambing are all needed.
Health programs for winter lambing ewes are critical. The fact that the sheep are in close proximity intensifies health problems. Mastitis, pneumonia, and scours are big concerns in winter lambing systems.
Late or Spring Lambing
Late lambing has some definite advantages over winter lambing. The synchronizing of the sheep production cycle to the cycle of forage growth allows for the maximum utilization of non-harvested forages. In general, this allows for lower cost of production than a winter lambing system. The decreased cost and labor associated with the decreased use of harvested and stored feeds is a powerful advantage.
Late lambing takes advantage of utilizing the spring flush of grass at the high nutrient requirement period of lactation. Also, with cool season forages, another smaller spurt of forage growth occurs in the late summer/early fall period. This is advantageous in preparing the ewe for breeding.
The advantages of maximum forage utilization are multiplicative. Reduced labor involved in feeding harvested feeds, cleaning up facilities and sheep management procedures are powerful advantages. Reducing labor in the sheep operation is a big advantage to lambing late.
Labor at lambing is reduced primarily because the threat of bone-chilling cold temperatures has passed and ewes don’t have to be checked every 2-4 hours. The chances of lambs freezing are severely reduced. That’s not to imply that adverse weather won’t occur during the spring, it does, but the extreme cold is less likely to occur.
Spring lambing has an advantage in that the breeding and lambing seasons are shorter and more condensed. Breeding ewes in late October through early December ensures that all ewes of any merit are fertile. Rams are also more fertile in this time period. The result is that most of the mature ewes should settle within two cycles (32 days) and the lambing season should last only about 35 days. Many times, winter lambing flocks have a 60 – 90 day lambing period, resulting in shepherd burnout and a non-uniform size in the lamb crop.
Spring lambing can also offer more management flexibility. Leaving some wool on the ewes for the winter period allows for outside wintering on crop residues, pasture overgrowth or poorer quality hay. Using large round bales can decrease labor and cost of winter feeding. Ewes can be lambed inside barns as with winter lambing programs or with the right type of ewe, they can be lambed on pasture. Ewes and lambs can be kept in mixing pens around barns or can be moved to pasture shortly after birth. Lambs can be raised on grass with their mothers, offered creep grazing or offered creep feed. The point being, management and nutrition programs can be made more flexible. Thus, one can tailor their program to the market and feed resources available.
Another large advantage is healthier sheep. Late lambing sheep generally spend less time in the barns and more time outside on pasture. This results in less health problems, especially healthier lungs.
To lamb late and go right to grass with the ewes and lambs requires a top notch parasite and predator control program. Young lambs are especially susceptible to both of these problems. Without a sound parasite treatment program, lamb mortality can be high and growth rate and thriftiness will be low. Predators are always a concern with any age sheep, but young lambs are an easy target for coyotes.
Pasture management has to be better in a spring lambing program and/or the carrying capacity of breeding ewes has to be reduced on a per acre basis. Fertilization, plant species choices, rest and recovery periods, etc., all require increased inputs and management.
Regardless of time of lambing, for lambs to be sold as finished they need to be fed a grain-based diet for at least 30 days to meet acceptable U.S. standards for grade, yield and carcass size. So even if late lambing on grass occurs, unless one is selling lightweight lambs or feeder lambs, some grain will need to be fed to most lambs.
Conclusions
There is no absolute best way to raise sheep. The diversity of production systems is an attractive feature of sheep. They can be raised totally in confinement, totally on grass or any system in-between. Whether to lamb early or late is an individual’s preference. Feed resources, land prices, climate, level of predation, marketing opportunities and labor availability will factor into the decision on when to lamb.
**Editors note: Please take note that this piece was first published in The Working Border Collie, Inc. in 1995. Although this article is a bit dated, a lot of the information provided is extremely relevant and applicable to sheep production today.