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Monday 23 October 2017

Sheep Tech: High mortality but lambing rate is good

Sean Conway is on track with Teagasc targets for a mid-season lambing flock with ewes at 1.61 lambs per ewe put to
Sean Conway is on track with Teagasc targets for a mid-season lambing flock with ewes at 1.61 lambs per ewe put to
ADDITIONS: Sean has installed a batch foot bath at the end of the race. A 10pc solution of zinc sulphate is used comprising of 1kg zinc sulphate to every 10 litres of water

Tom Coll

Lambing commenced on Sean Conway's farm on March 10 and was compact as planned with the last lamb born on April 14. Sean is working to the Teagasc targets for a mid-season lambing flock with ewes currently at 1.61 lambs per ewe put to the ram and ewe lambs at 1.11 lambs per ewe lamb put to the ram.

Mortality in the ewe flock is at 10pc which is good considering four ewes aborted due to toxoplasmosis and five died prior to lambing – three on their backs and two with ruptured prolapses. Mortality in ewe lambs was high at 22pc; this included seven abortions also due to toxoplasmosis following foetal diagnoses in Sligo Regional Veterinary lab.

All ewes lambed outdoors, but ewe lambs were housed for lambing due to poor weather. Ewes rearing twins received concentrate supplementation at 0.75kg per head per day up to April 1 due to poor growth and insufficient grass supply.

Supplementation of the twin rearing ewes enabled them to reach peak milk yield at three weeks post lambing. Sean's goal is to finish 90pc of lambs off grass with no concentrate input. Concentrate fed per ewe to date is as targeted at €8 per ewe.

Flock Health

Earliest born lambs were dosed on April 19 with a white worm drench following the Department of Agriculture website forecast by the nematodirus advisory group.

They advise that lambs in the south and westerly coastal areas should be dosed with a suitable anthelmintic from mid-April while those in the rest of the country should be dosed from late April.

Sean's flock graze the same fields each year which increases the risk of infection. He plans to use faecal egg counts from June onwards to determine when future dosing is required. In the case of nematodirus it is the larvae that cause the damage to the intestine and so the nematodirus forecast is the best method of predicting when to dose.

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Farmers should be aware that that the symptoms of a nematodirus outbreak are similar to an outbreak of coccidosis or 'black scour'. Dehydrated lambs collect around drinkers before dying. Sean has no history of coccidosis on the farm.

Two years ago he took part in a lameness study carried out by Teagasc and UCD's School of Veterinary Medicine. Final year student Fergus Hannon visited the farm and assessed all sheep for lameness and identified the causes of lameness in Sean's flock; 9pc were lame on the day of the visit with a third of these suffering from foot rot (mainly in ewes), another third were cases of scald, mainly in lambs, the remainder was due to shelly hoof.

Sean has since installed a batch foot bath at the end of the race. A 10pc solution of zinc sulphate is used comprising of 1kg zinc sulphate to every 10 litres of water.

This is topped up prior to each use and totally cleaned out when faeces builds up in the bath. Ewes and lambs are put through the foot bath every two to three weeks over the summer period, usually when gathered for other jobs such as dosing, shearing and draughting.

Sheep stand in solution for three to five minutes and are then let stand on clean concrete for up to one hour. Lambs that are badly lame are treated with alamycin spray when the hoof dries. Ewes with foot rot are treated with an antibiotic, usually oxytetracyclin. Only ewes with overgrown hooves are foot trimmed with foot shears that have been disinfected between each hoof.

Sheep are then returned to a paddock on the farm that has not been grazed for approximately three weeks, normally the next paddock in the rotation. The bacteria that cause foot rot can survive on the pasture without sheep for a maximum of two weeks.

Sean had a few cases of scald in lambs over the past week, but this has cleared up following a recent run through the foot bath and an application of alamycin spray.

Soil fertility

Soil samples were taken last February to establish the current soil fertility status and lime requirements of the farm. Twelve samples were taken, each representing a 4ha block. Three samples were index 1 (<3mg/l) for phosphorus (P), seven were index 2 (3-5mg/l), while only two were in index 3 (5-8mg/l).

The pH ranged from 4.91 to 5.65. Half of the samples were index 2 for potassium (50-100mg/l) and 50pc were index 3 (100-150mg/l). Sean's first aim is to correct the pH of the soil by applying two tonnes of ground limestone per acre across the entire farm. Fields closed for silage will be limed after crop removal to ensure no interference with preservation.

Slurry was applied to silage ground after grazing by sheep at a rate of 3,000 gallons per acre supplying around 16 units of P to match that removed by the harvested crop.

Two bags of 18:6:12 and a bag of CAN per acre were applied seven days later to improve soil P level. Around 80 units of nitrogen per acre, including nitrogen from the slurry, was supplied.

18:6:12 will be applied to grazing ground for the remainder of the year based on grass demand. Sean's soil analysis results are typical of samples taken by discussion group members in groups I facilitate across Sligo and Leitrim.

The majority of samples taken this year show that fields require lime and are deficient in phosphorus and potassium. Soils with a pH of less than 6.3 can be up to 70pc less efficient in the use of applied nitrogen, phosphorus and potassium.

The application of lime to increase soil pH to the target 6.3 level can release the equivalent of 50-60 units of nitrogen per acre on an annual basis.

Back at Sean's farm, all lambs will be weighed in the next two weeks and again at weaning and prior to sale. Lambs are electronically tagged and details of lamb performance and slaughter data will be outlined in future articles.

  • Tom Coll is a drystock business and technology adviser with Teagasc's northwest regional unit.

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