The flock is a Greyface Mule cross, which is mated with Suffolk or Charollais rams.
"The Greyface Mules are terrific mothers and very prolific. For the last four years, we've averaged 1.95 lambs per ewe," says Chris's wife, Sarah, who divides her time between the farm and working out of Roscrea as a garda.
"The Suffolk and Charollais throw good lambs that grade well.
"We have tried a Suffolk Mule cross ewe, but the jury is still out on those because, while the carcases are better, they just don't have the mothering instincts of the Greyface Mules, and the young ewes can be a bit mad to handle," she said.
With so many sheep to get in lamb, the Bourns carry about 50 breeding rams, which are topped up with five to six purchases at the pedigree sales every year.
"We paid anything from €400-650 for Suffolks at ram sales in Ballinasloe and Roscrea last year, but the Charollais at Tullow seem to be a bit more expensive at €600-800.
"We'd generally stick to buying from flocks that we know have produced rams that have performed well for us in the past. But you'd be shocked at how quickly rams wear out, and they just aren't as hardy as the crossbred equivalents," she said.
"We'll be looking for five star animals, but we also want to see good size, length, confirmation, legs and not too big a head for lambing."
Managing the actual mating is a tightly choreographed process that hinges on a rather unlikely element - college students' mid-term break.
"We generally take on about 10 vet students here every year. They come to us during the mid-term break, so that's when we want our peak to hit. We contact the college every year to find out when that's happening to figure out when to let in the rams.
"In theory there's two 12 hour shifts, from seven to seven. But we also have people starting at 12 to cover the transition and the evening time, which can be particularly busy," says Sarah.
"We're aiming for a really compact lambing season of about 3.5 weeks. After that, everybody's just too knackered to keep going at the same pace. For this reason, we don't use ewe-lambs, because they just stretch out the lambing season.
"To allow for this, we let vasectomised rams in with the sheep about two weeks beforehand to get them all cycling. Then we let in the first batch of rams, at a rate of one ram per 80 ewes. We keep the sheep in groups of about 400, so it's the equivalent of five rams. The next key decision is when to let in the second batch of rams, since you don't want them going in too early.
"We let them in about 10 days after the first batch this year, and ended up with too much pressure on in the first two weeks of lambing this year. So we're going to push that out to 15 days later this year. "The first rams go in without a harness, the second with a red marker, the third with a blue colour," explains Sarah.
Lisbeg farms facts
• 1,400ac farm in one block, with 160ac leased
• 300ac forestry, 560ac tillage, 700ac grassland• 1,500 ewes, with an average weaning rate of 1.72 lambs/ewe over the last three years
• Farm also accommodates 1,700 fattening bulls, heifers and bullocks
• Six staff plus Sarah and Chris and Chris's parents, Richard and Deirdre
• Richard and Deirdre also involved in developing high-end show-jumpers with Chris's brother Andrew, who is based in Florida
• Joe Carty in Tarpey Agricultural Advisors is the key advisor to the enterprise
An enterprising approach to the sheep farming essentials
"We split all the fields into 5ha paddocks in recent years, which allows us to graze them for about a week at a time with batches of 200 ewes and their lambs. We let in the cattle about two days before the sheep, and then move the cattle on two days before the sheep into the next paddock. We aim to be back in the same paddock again 28 days later," says Chris.
"We don't measure grass - it's one of the things on our hit list, but we do soil sample and reseed 5-10pc of the grassland every year. I plant it with a cereal crop, and keep it out of the rotation for a year or two before reseeding it again."
"We don't creep graze because the amount of fencing and gates that we'd need for this would be crazy," says Chris but lambs are creep fed throughout the grazing season. "I also feel that it helps us get our lambs away quicker by feeding throughout the season.
"We find it is more economical to feed a smaller amount of concentrates to lambs during the summer months when weather is typically good and get them finished earlier rather than feeding heavy amounts of concentrates to lambs in the winter and when thrive is poor."
The lamb creep is from Charlie Wynne's of Athy and includes molasses, mineral, soya hulls, high protein soya and lamb pellets, molasses beet pulp, flaked oats, along with flaked beans, maize and barley.
Shearing and showering
"We initially switched from shearing in the summer to shearing in January to maximise the amount that we could fit in the shed," says Chris. "But the ewes could find it really cold, so we've moved to a halfway house of shearing in September, so that we still get the benefit of more sheep in the shed, but without them feeling the harshness of winter in January.
"The downside is sheep going on their back in the summer, so that's why we shower them every three to four weeks during the grazing season. "We moved away from dipping about 10 years ago to a shower system designed by Cormac Engineering. It is basically a sprayer boom on the ground and mounted above the sheep in an enclosed tin hut. We can get about 15 in there at a time, and we find that it works very well, using less dip and being less stressful on both the sheep and operators."