Spring-Lambing for Consistent Profitability
Livestock Update, April 1995
Steve Umberger, Animal & Poultry Sciences, Virginia Tech
Lambing in the spring capitalizes on the reproductive merits of a spring-lambing flock, and takes advantage of spring, summer, and fall forages for lamb production. Spring-lambing reduces the capital outlay required for labor, facilities, and purchased feeds. Studies comparing fall-lambing, winter lambing, and spring-lambing production systems found spring lambing to consistently be the most profitable production system of the three. The higher profitability of spring lambing is attributed primarily to improvements in ewe fertility and prolificacy. Because of the seasonality of breeding inherent in most breeds of sheep, fewer ewes lamb in the fall and winter, with fewer lambs born per ewe lambing.
Spring-lambing occurs during the months of March, April, and May. Lambs graze with their dams in the spring and throughout most of the summer. After weaning, lambs remain on pasture until marketed as slaughter lambs or feeder lambs in the late summer and fall. Grazing management, internal parasite control, predator control, and lamb marketing strategies are key elements essential to a successful spring- lambing program.
Crossbred ewes are recommended for commercial spring-lambing flocks. Crossbred ewes wean more pounds of lamb than the average of the purebred ewes that make up the cross. Numerous breeds and their crosses are available. Breeds commonly used in commercial spring-lambing flocks include Suffolk, Dorset, Hampshire, and Rambouillet. Unless producers have the time and facilities required for artificial rearing, the incorporation of highly prolific breeds of sheep, such as the Finnsheep and Romanov, into crossbred ewes used for spring-lambing should be avoided. Ewes have there highest lambing percentages in the spring. Therefore, breeding programs that further enhance prolificacy create a management hardship in the form of excessive triplet and quadruplet births. Suffolk x Rambouillet crossbred ewes imported to Virginia from southwest Texas, commonly referred to as "western ewes", have been used extensively for spring- lambing. When managed properly, western ewes have the potential to produce 170% or greater lamb crop in the spring. A three-year research study conducted in Virginia showed 9% of western ewes having triplet-born lambs in the spring compared to 38% triplet-born lambs from 1/4 Finnsheep x 3/4 western ewes. Although the breed has been used very little in Virginia, the conditions under which the North Country Cheviot was developed make it a potentially attractive breed for spring-lambing. Their lambs are vigorous at birth and the ewes are reported to make good mothers.
The breed of ram used for spring-lambing flocks is dependent on the type of lamb marketed. Lambs expected to reach slaughter weights of 120 to 125 lbs should be sired by heavy muscled Suffolk, Hampshire, or Suffolk x Hampshire rams. Lambs produced for the ethnic market or lambs expected to reach slaughter weight at 100 to 110 lbs should be sired by rams of earlier maturing breeds such as Dorset or Cheviot. Attempts to finish lambs on forage alone should be limited to lambs sired by rams of earlier maturing breeds. Lambs sired by rams of later maturing breeds will not consistently produce an adequate degree of finish from forage alone, even when carried to heavier market weights.
Barn-lambing, pasture-lambing and, most commonly, a combination of barn- and pasture-lambing are used in the spring. Both assisted- and unassisted-lambing are practiced in Virginia. Assisted-lambing involves frequent observation of the flock at lambing time, and the placement of ewes and their lambs in individual lambing pens after lambing. Weather permitting, ewes with single lambs and ewes with strong, well-claimed twin lambs spend little, if any, time in the lambing pens. Assisted lambing establishes the milking status of the ewe and the general health and well-being of her lambs. The major goal of assisted lambing is to minimize lamb death loss. Unassistedlambing generally occurs in the late spring when weather is less of a factor, and is used on farms where few facilities are available for lambing and labor is limited. Ewes are left to lamb on pasture with a minimum of assistance provided. Because flock lambing percentages are highest during the spring, lamb mortality rates are greater with unassisted lambing. For this reason, unassisted-lambing is discouraged. Budget analyses have shown that other than market price, the percentage of lamb crop marketed annually has the greatest impact on profitability of production. Therefore, it is to the producers' advantage to provide assistance whenever possible.
Spring-lambing gives producers the opportunity to take full advantage of the inexpensive gains attained from grazing lambs on spring, summer, and fall forages. Lambs born in March, April, and May graze with their dams in the spring and throughout most of the summer. Research conducted in Virginia has clearly shown that lambs gain approximately .15 lb more per day when left on the ewe through late August versus weaning in July and grazing ewes and lambs separately. After weaning, lambs are left on pasture and remain there until marketed as slaughter lambs or feeder lambs. Retention of feeder lambs to graze fall pastures, aftermath hay fields, or fall and winter annuals before placing them in a feedlot for grain finishing tends to be consistently more profitable than marketing lambs as feeders in the late summer and fall.
After lambing in the spring, lactating ewes are set-stocked (not-rotated) at the rate of four to six ewes and their lambs per acre until mid to late June. Set-stocking gives ewes and their lambs the opportunity to be more selective in their grazing behavior, which promotes more desirable levels of milk production and greater lamb gains. Set-stocking at relatively high stocking rates in the spring helps to control the spring flush in forage production, while allowing approximately onethird of the spring pasture to be fenced off for hay production. Rotational grazing programs designed for the movement of sheep every 10 to 14 days are instituted in late June and July to improve both pasture and lamb production. More intensive rotational grazing systems where higher stocking densities are used promote more complete forage utilization, but also require greater input costs in the form of fence and water, and may result in higher levels of internal parasitism, increased risk of coccidiosis, and impaired lamb performance.
For improved late-summer performance, spring-born lambs should be sheared by early July. In a Virginia study, average daily gain was .05 lb greater for shorn versus wooled lambs over a 90day grazing period during the summer and early fall. Even though, shorn and wooled lambs were slaughtered at the same live weights, shorn lambs had higher carcass dressing percentages and a more desirable fat cover than carcasses from wooled lambs. An economic analysis taking into account the additional costs required for shearing still showed a clear advantage for summer shearing of spring-born lambs.
Lamb gains are not uniform throughout the grazing season. In general, lamb gains exceed .60 lb per day in the spring, average approximately .30 lb per day in July and August, and are approximately .40 lb per day in the fall. In late summer and fall, lamb gains can be improved by .15 lb per day by supplementing 1 lb of corn or barley per lamb daily. Depending upon the time of marketing, these additional gains may or may not be cost effective.
Internal parasitism can dramatically affect grazing lamb performance on spring, summer and fall pastures even to the point of death. Contrary to statements that rotational grazing helps control internal parasites, research has clearly demonstrated that internal parasite larvae are capable of surviving on pasture for more than a year. Therefore, most short-duration rotational grazing programs (rest periods of 15 to 30 days) are not beneficial for the control of internal parasites. An effective internal parasite control program should not rely solely on the use of anthelmintics. Use of drugs as the only method of control often results in an increased incidence of internal parasite resistance. Whenever possible, sheep should be placed on "clean pastures" to slow down the rate of reinfection. Examples of clean pastures include:
Critical times for treating sheep for internal parasites are:
Treatment dates should be marked on a calendar to reduce the risk of losing sheep from a failure to treat on time. Underdosing of anthelmintics results in accelerated rates of resistance by internal parasites. Because anthelmintics are administered on the basis of weight, it is important to take weights of a representative sample of the animals being treated so that proper dosage amounts can be calculated.
The risk of predation is greater with production systems that have pasture-lambing and/or lamb grazing components. Winter born lambs usually remain in drylot or confinement up through marketing, and, as a result, are less susceptible to predation. For this reason, a number of producers use winter- lambing as a tool to minimize their losses from predation. Sound predator control strategies must be developed and in place for farms with a spring-lambing program. Predisposing factors to losses from predation include:
The two primary predators in Virginia are dogs and coyotes.
Producers should work with their extension agent and/or an employee of USDA Animal Damage Control to develop strategies that prevent predation by coyotes and dogs. Typically, measures that prevent coyote predation will also control dogs. The importance of properly constructed fence cannot be overstated as a tool for protecting sheep from dog and coyote predation. Highly effective, safe, and inexpensive electric fencing systems has made fencing for predator control more practical. High tensile smooth wire electric fence is cheaper and easier to construct than most traditional types of fence. Electrified boundary fence is one of the most effective tools for predator control, and provides an opportunity to tie in temporary electric fence to facilitate pasture subdivision. Boundary fence for sheep should consist of at least five strands of electrified high tensile wire, with wire spacings from the ground up of 6, 6, 8, 10, and 12. Other forms of control include:
Most lambs produced from a spring-lambing program are marketed as feeder or slaughter lambs. In general, the production of feeder lambs will not generate as much income as the production of slaughter lambs. However, when managed properly, feeder lamb production still returns a consistent year to year profit for producers. Feeder lamb production is particularly attractive to new producers. After lambing, the only major management input that remains until marketing is the control of internal parasites. With feeder lamb production, profitability is highly dependent upon the percentage of lamb crop marketed. A goal of 150% lamb crop marketed is not unrealistic and assures a breakeven price for producers of approximately $.42/lb. In general, heavier lambs at the time of marketing make up for a lower percentage of lamb crop marketed and contribute to higher levels of profitability. Another factor to consider when marketing spring-born lambs is the historically low lamb market that occurs in September and October of each year. If possible, producers should avoid marketing lambs during this period. Leaving lambs on fall pasture, grazing aftermath hay fields or supplementing grain on pasture during the fall are all strategies that can be used to delay the time of marketing. When all available forage resources are depleted, lambs are placed in a feedlot to be fed to heavier weights using a whole-grain feeding program.
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