David, who farms at Marrabel, South Australia, with his wife Paige and parents Ian and Roz, said a trial on a much smaller scale a few years ago gave them the confidence to proceed with the maternity ward on a much larger scale this year.
"This year, we'll lamb down over 400 ewes in the shed," David said.
"There were 83 ewes in the first lot, mostly scanned with multiples."
The Mernowie set up involves a large shed near the sheep yards which has been fitted out with small pens and a watering system. The stud Merino ewes that have been artificially inseminated are put into the pens after the first one in a mob lambs.
"Because these ewes are AI'd, the mob tends to lamb over five or six days," David said.
The Rowetts run four programs of AI each two or three weeks apart. This means they know exactly when the lambs are going to drop and have time to get the ewes in and out of the shed before the next mob is due.
"As soon as the first one or two lambs drop, we put the mob into the shed," David said.
"We bring them in really slowly and quietly - no dogs. They walk in and settle in very quickly.
"The main reason we started doing this was so we could easily record pedigrees on our stud lambs. We generally have to DNA test or mother up to record pedigrees. This is a lot easier."
David said the stud's goal is to identify the ewes consistently leaving the top lambs so they can be embryo transferred.
He said all the ewes are good mothers because for 30 years, the Rowetts have been culling ewes that have a lamb and fail to rear it.
The pens are bedded down with straw, which takes a lot of labour to set up but will be good for at least two mobs of ewes.
The two-to-three weeks in between the mobs gives the straw time to dry out. It is topped up before the second mob comes through, then might all be cleaned out and replaced before the third mob.
The sheep spend a maximum of only a few days in the shed. The ewes and lambs are moved back out to lucerne pasture as soon as the lambs are strong enough, generally about 24 hours after birth but occasionally longer for multiples.
Single-born lambs are often ready to go after half a day. David said that people tell him this all sounds like a lot of work, but that it isn't really.
"We go through the shed twice a day to check the ewes and walk out the ones that are ready to go," he said.
FEWER LAMBS LOST
Aside from the time and cost saved by no longer needing to DNA test or mother up, David has noticed a reduction in lamb losses.
"I don't have exact figures yet, but early indications are we should conservatively expect to reduce lamb losses by 5-10%," he said.
Because the lambs are in the pen with their mothers, there is no mismothering. The ewe doesn't need to walk off to get water and the first born lamb of multiples can't wander off as its sibling is being born.
"It's also easier to pick up any ewes having difficulties during lambing and help where needed."
David said a conservative estimate would be that they save an extra 30 lambs that would have been lost out in the paddock.
He said that another advantage was being able to use ewes that had lost their lamb as a surrogate for a lamb from another ewe's triplets.
Given the close proximity of the ewes to their lambs, the chance of success is increased and it's easy to keep an eye out in case it doesn't work, in which case the triplet lamb can be quickly moved back to the ewe.
"Once we get the Merino lambs through the first 24 hours, their survival is generally good," David said.
"If we get bad weather during lambing, we don't have to worry about it. We don't have to worry about trying to find them shelter if we get rain. Hot weather can be difficult at lambing too, and in the shed we don't have the problem of a ewe getting up and walking to the trough to get water and leaving her lamb behind."
DOLLARS STACK UP FOR STUD
David said the shed cost about $25,000 to set up with pens and water.
"We've worked on a payback period of about three to four years," he said. "It may be quicker.
"This year we should get over 500 lambs in the shed. If we had to DNA test them, that alone would cost about $10,000. Plus we may get about an extra 160 lambs that we would have lost out in the paddock. They're worth about $200 each, so the economics of it stack up for us."
The Mernowie shed will also double as a venue for the stud's annual ram sale.
"We generally sell 200 to 280 rams each year, and the shed set up will be perfect for that," David said.
"It's convenient because it's right next to the sheep yards, so it's easy to move sheep in and out."
David Rowett, Mernowie Poll Merinos