By ROGER A. HIGH
Ohio State University Extension
COLUMBUS — With increasing production costs, livestock producers really need to evaluate each animal and decide whether that animal is a productive creature or “just on the payroll.”
Marginal producing ewes and rams should not be maintained in the flock. Culling is one of the tools that should be implemented to increase the efficiency of the sheep flock.
But what criteria should a producer use to base their culling decision?
Open ewes are the greatest contributor to low-weaning percentages and are costly in terms of feed, labor and management. When deciding which ewes should be culled from the flock, first eliminate those open ewes and those that have lost lambs due to excessive lambing difficulty, as well as those ewes that have prolapsed or have shown that they are prone to a prolapse condition.
A ewe that does not breed one time will lose a significant amount of her lifetime production potential. It will take the returns of two to three productive ewes to pay for the maintenance of one open ewe.
One of the top reasons for culling ewes and rams is health issues. Health issues can be a large drain on time, labor and resources. Such health issues as chronic foot rot and foot scald make management of the flock more difficult. Sheep that are limping from foot rot and foot scald perform poorly and should be culled from the flock.
Mastitis is another health issue which causes damage to the udder and causes low milk production. Also check eyes for cloudiness or other issues that may cause vision problems.
A third reason that should be considered for potentially culling a ewe is her soundness and udder quality. Non-functional ewes are those that have lost all or part of their udder’s function. These ewes create management difficulty because they generally cannot produce enough milk to maintain the nutritional needs of their lamb(s), thereby creating a need to orphan or bottle feed the lambs so they can survive until weaning.
Structurally unsound ewes (incorrect feet and legs, mouth) and hard keeping, emaciated ewes should also be considered as culling candidates, as their nutritional needs are much higher than the average of the ewe flock and there is no reason to continue producing these types of genetics as possible replacements.
Late lambing ewes are the fourth potential culling criteria. As a producer, you will need to look at your lambing distribution during the lambing season and identify those ewes that lamb during the third, fourth, or later lambing cycles. Generally ewe lambs and ram lambs born in the earlier lamb groups will be the most productive sheep in the flock.
A producer should keep in mind whose fault it was that the ewe bred in a later heat cycle. Reasons that are not the fault of the ewe includes an inadequate nutritional (flushing) program prior to breeding season and a second reason may be ram infertility.
In general, the primary reason that a ewe flock does not breed early is due to ram infertility and the primary reason that a single ewe does not breed early is due to ewe infertility at an inappropriate time of the year.
Rams will generally have lower fertility early in the breeding season, (July, August and early September) and will have higher fertility later in the breeding season (late September, October and November), so a ewe may be cycling normally in the early breeding season, but due to ram infertility, she may not become pregnant.
Heat-stressed rams and infertile rams will generally need 60 days to become fertile enough to impregnate the females. If the entire ewe flock is not settling in the first two heat cycles (34 days), then a ram infertility problem should be suspected, and another ram should be placed with the ewes if you are to expect a lamb crop during that production year.
A fifth potential reason for culling a ewe is age. You should not automatically cull a ewe that is six years of age, but you should consider if she can effectively make it through another year. Consider things such as maintenance, breeding, lambing and lactation.
Ewes need to be culled while they still have a cull value, because dead ewes have no value. If she can effectively produce another set of lambs without requiring more of your time and attention, then she can be maintained in the flock.
Another reason for culling a ewe should be for genetic progress reasons. Based on your records and performance data of your flock, cull ewes most likely produce poor quality lambs with lower than average production and growth traits such as weaning weights.
Use multiplicative genetic adjustment factors (60-day, 90-day, and 120-day weights) to determine the productivity of a ewe. These multiplicative genetic adjustments are based on the age of the ewe, the type of lamb birth (single, twin or triplet) and the sex of the lambs born to the ewe.
As an alternative, you may choose to enroll in one of the genetic improvement programs. A 2-year old’s adjustment for twins is different than a 6-year-old’s adjustment for twins. It may be detrimental to the flock to only select and keep females based on actual data rather than using genetic adjustment data.
Culling an animal for poor disposition is often over looked; however, this practice can save a lot of stress down the road on your shepherd. Ewes that are difficult to maintain in a grazing situation, run through temporary fence or jump gates should not be maintained in the flock.
Ewes that step on and lay on lambs in the lambing pens because of a poor or flighty disposition should not be maintained, either. In some part-time operations, ewe disposition is a very important item to consider when making culling decisions, due to lack of time in dealing with mis-mothering, injured and poor doing lambs.
Culling is a better tool for eliminating dysfunctional or nonprofitable ewes than for building genetic improvement. The vast majority of the genetic capability of the ewe comes from the rams that you have used in the past.
Some individuals recommend replacing 15 percent of the ewe flock annually. The decision to cull ewes over time will change from one year to the next, depending on feed supplies and feed costs, the need for cash flow, current lamb prices and your production cycle.
Since cull ewes can be included as part of the income segment on the balance sheet, you should watch the markets and market your cull ewes at a time when they are the most valuable. This market varies depending on the need for cull ewes, the amount of ewes and rams coming to market at any one given time and the body condition of the ewes that are being culled.
Generally, the thinner ewes will have a higher value per pound of body weight and may even create more total dollars than those ewes that are fat.