Using birth fluids as a means of getting a ewe to adopt a lamb is the most effective method of fostering lambs, according to new research.
Trials by Moulton College, Northampton, found lambs fostered on to a ewe grew faster, produced higher quality carcases and cost less to rear compared with lambs put on to a milk machine.
The investigation was undertaken within Moulton College’s commercial flock of North Country Mules and was based on three groups of 84 ewes – each of which was involved in one of the three fostering methods being evaluated or the control group. Ewes were monitored for behavioural responses during and after the fostering process.
Birth fluids, ewe restraint and cervical stimulation were the three fostering methods undertaken within the first 30min of the birth of lambs. Birth fluids and cervical stimulation were carried out in individual pens.
Using birth fluid
Researcher Samantha Ward says when birth fluids were used the ewes were readily suckling both lambs within 20-30min of fostering taking place.
“We had a 100% success rate when birth fluids were used to smear the lamb to be fostered – and the ewe’s own single lamb. However, we had to take care not to make lambs excessively wet,” she says.
“The majority of farmers prefer to use birth fluids because they feel it’s a welfare friendly and less-invasive method of fostering. But some prefer to use head restraints based on the urgency of lambs to suckle milk and to avoid artificial rearing,” she says
Using head restraints
However, fostering using ewes held in head restraints only achieved a 64% success rate. Miss Ward says the failures occurred when ewes were released after four days and yet continued to reject the fostered lamb.
“Restrained ewes also experienced more stress and produced significantly higher heart rates and salivary cortisol concentrations, but those that did eventually accept their fostered lamb appeared to suffer no adverse effect on milk yield during the lactation,” she says.
However, even though restraining ewes was not as effective as using birth fluids, the results were still better than when lambs were reared artificially.
“Artificially reared lambs had worse carcass conformation which suggests those fostered on to a ewe are better in terms of flock productivity and income,” suggests Miss Ward.
Cervical stimulation as a means of acquiring birth fluids from a newly lambed single-bearing ewe – and used to smear on to a lamb to be fostered – achieved a 82% success rate.
“This method is also believed to stimulate a hormonal release replicating parturition and so triggering an assumption in the ewe that she has produced a second lamb,” she says.
Despite the varying methods foster lambs can be reared on to a year, results showed ewe-reared lambs gained significantly more weight than artificially reared lambs up to 90 days of age.
Miss Ward explains: “Conformation scores were better for ewe-reared lambs compared with those reared artificially. However, fostering methods didn’t have a significant effect on the growth rates, carcass or meat quality measurements for the lambs studied.”
Miss Ward’s work has also found that smaller foster lambs taken from a triplet and fostered with a large single lamb made significant compensatory growth to almost match the development of their sibling.
“There’s certainly an opportunity here for further investigation,” says Miss Ward.
What are the most popular fostering methods used (based on research by Miss Ward)?
- 93% of farmers prefer to foster lambs rather than artificially rear them
- 64% of farmers prefer to use birth fluids
- Only 19% of farmers use restraint crates
- Most popular combination is cervical stimulation of the ewe in addition to using birth fluids
- Most farmers also consider health of the ewe and ewe welfare before deciding on fostering method.
What method of fostering do you find has the most success in your flock? Why not share your tips at www.fwi.co.uk/livestocklines