Thursday 29 September 2016

Sheep: Lamb growth rate is down on last year as weather takes toll

Tommy Boland

Published 20/04/2016 | 02:30

Weather has affected lamb growth rate.
Weather has affected lamb growth rate.

The more things change, the more they stay the same. This time last year we were worrying about grass growth on the experimental platform. This year we are in slightly better shape as we had more grass at turnout, but anything which was grazed is very slow to recover.

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Soil temperature has dropped on the Smart Grass site from 7C in early April to a low of 5C on April 11. This is borderline for grass growth and is reflected in grass growth grates of just 13kg/DM/ha on the perennial ryegrass (PRG) and the PRG and white clover swards.

The multi species swards are doing better with growth rates of 30kg/DM/ha in the week to April 11. While this helps in the short term, it is just a comparison over a single week and is not indicative of overall performance.

Average figures can be very misleading and there is wide variation in these growth rates. The PRG paddocks grazed this spring are only growing at a rate of 7kg/DM/day while the paddocks not grazed since closing are growing at 21kg/DM/ha.

There is still adequate grass supply available so we are not supplementing concentrates and with warmer weather forecast grazing should improve in the coming week.

This low grass growth rates on the hill at Lyons is in contrast to the dairy platform which grew 46kg/DM/ha per day during the same week.

Much of the difference is linked to elevation and aspect of the hill site, though there was also slightly higher nitrogen application on the dairy platform.

However with the low soil temperatures and high rainfall on the hill ground there is little benefit to nitrogen application until soil temperature increases.

The cold and wet weather conditions this spring increase the risk of grass tetany in suckling ewes and we are often asked how we deal with this risk in the absence of concentrate feeding.

For the last few years we have used a slow release magnesium bolus on the experimental ewes. This is a three week bolus and appears to be working in so far as we have not lost ewes to grass tetany during its usage.

There are only seven ewes from the second round of repeats left to lamb at this stage and these are lambing outdoors with minimal supervision.

The non-experimental ewes have finished grazing the silage ground and are now grazing the hill ground where they will remain until weaning.

Lamb growth rate to three weeks of age is also down about 8pc to just over 300gm per day compared to last year.

Again much of this can be put down to the cold wet weather conditions and the subsequent effects it has on reducing the ewes dry matter intake and her ability to extract energy from the grass she consumes.

International appeal

The international appeal of the Lyons sheep flock continues and we have two PhD students from Poland working with us at the moment.

Martyna Monka and Anna Wyrostek who are studying at the Agricultural University of Wroclaw are working with Connie Grace on the Smart Grass trial and Mark Boland who is looking at feed ingredient quality as part of a Department of Agriculture Research Stimulus Project - FEFAN.

More information on the Smart Grass project will be presented at the IGA sheep conference which will take place in Lawless' Hotel in Aughrim on April 26, followed by a visit to John Pringle's farm.

Other topics for discussion include information on the Teagasc Pasturebase project and increasing grass utilisation plus Neil Perkins from Wales outlining his 2,400 ewe operation.

Dr Tommy Boland, lectures in sheep production and ruminant nutrition at UCD's Lyons Research Farm, in Newcastle, Co Dublin

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