Lambs may be orphaned in several ways. The mother may die, lambs may be abandoned by the mother or they may be taken from the mother due to health problems or an inadequate milk supply. Although we can step in and provide milk and warmth that a mother normally provides, the mother can do a better job and save us considerable time and expense.
Fostering lambs is the process where foster mothers are found for lambs that have been orphaned. There are several methods for grafting lambs onto ewes. It is important to understand ewe behavior. Nearly all ewes reject lambs that are not their own (alien lambs). Discrimination of their own from alien young is based on odor cues. Ewes recognize lambs by sight, sound, and smell. Final discrimination of their own from alien young is based on differences in odor.
Methods of grafting
Orphan lambs may be grafted onto ewes by six different methods.
Slime grafting involves rubbing alien lambs with amniotic and placental membranes at the time of parturition. It must be performed soon after birth and depends on the successful recovery of slime.
Wet grafting involves dipping the alien lamb in a water-based solution such as salt water to get rid of the lamb's own smell in order to trick the ewe into accepting the lamb.
Skin grafting is also based on the principle of lamb-specific odor transfer. An un-decomposed dead lamb is needed and the pelt must be removed from the dead lamb's body. The pelt sometimes becomes rancid, however, and may attract insects while being worn by the alien lamb. It is not always successful, and the ewe must be restrained for several days before the lamb is fully accepted. This takes a lot of time.
Vaginal stimulation involves gently inserting the hand into the ewe's vagina to mimic the birthing process. It must be performed soon after delivery. This method of grafting can also be used in combination with other methods.
Restraint fostering is about 70% successful but it takes a lot of time and space in the barn. It takes on average four days to successfully graft using restraint fostering.
Odor-transfer fostering with stockinettes
Odor-transfer fostering with stockinettes is a fostering technique using stockinettes. The stockinettes are orthopedic stockings, like those used under casts. They can be purchased at an orthopedic supply store for under 50 cents each. A simple pattern can be used to cut out the stockings to fit lambs. The cloth "jackets" become impregnated with odor of the lamb.
Transferring the jacket of a ewe's own lamb to an alien lamb imparts own-lamb odor to the alien. Fostered alien lambs wearing own-lamb jackets smell enough like own-lambs to elicit maternal behavior from their foster mothers.
Lambs wear the stockinettes for 24 hours before being switched. The ewe is taken away from their own and the alien lambs for three hours so lambs will be hungry and suckle. Ewes should be far enough away so lambs cannot hear them. After three hours, the own-lamb and alien-lamb jackets are switched. The lambs keep the jackets on for 48 hours (after own and alien lambs are put in with ewe) to make sure the ewe has accepted them.
Odor transfer using stockinettes is successful for both substitution and add-on fostering.
Substitution fostering involves grafting or substituting an alien lamb for the ewe's own lamb that has died, in most cases. If the lamb to be grafted on is older than the ewe's own lamb, its legs may be tied up for 15 minutes so the ewe can smell the lamb without it being overly aggressive to milk. There is a 90% success rate with this method.
Add-on fostering means you are giving a ewe with one lamb another lamb. With some breeds such as Finn Sheep, more triplets and quadruplets may be born. Add-on fostering works well to even up lambs to ensure adequate milk. This method has shown to be about 70% successful. This is about the same success rate as restraining the ewe but it take a lot less time, 1.5 days versus 4 days with restraint.
Odor-transfer represents a relatively rapid and efficient technique for fostering alien young on postpartum ewes. The age of the fostered lambs is not as critical as with some of the other techniques. Some lambs 7–12 days old have been accepted. This is one management technique that could make raising sheep more profitable. It allows ewes to raise as many lambs as their milk production will allow.
In order to make fostering lambs most successful, it is important to find a foster ewe as soon as possible. While waiting for a foster mother candidate, tube feeding of the lamb or holding a ewe while the lamb suckles is recommended rather than bottle feeding. Bottle lambs are usually difficult to train to suckle from a ewe.
The cost of milk replacer is high and cow milk is not as nutritious to lambs as sheep milk. It is more profitable and less time consuming to graft lambs onto ewes rather than bottle feeding them.
This article was revised from CCES 201 (November 2000) written by Amy Peters, former livestock faculty in Coos County, Oregon.