Housing sheep under plastic has been proven as an economic route to easier winter and lambing management. Peter Hill relates one farms experiences and outlines todays polytunnel options
FOUR years after installing one of the countrys largest polytunnel sheep houses, Frank Moffat, manager at John Parker Farms, Droxford near Southampton, has no regrets about choosing the plastic-clad tubular steel frame structure in preference to a traditional building.
"We needed extra accommodation to ease lambing management which previously involved constantly moving sheep and lambs between different buildings on the farm," he says. "The polytunnel is proving an effective and economical solution."
The 1100-ewe flock at Wallops Wood Farm – comprising 350 Scotch half-breds and 750 Texel x Scotch half-bred ewes – makes use of the 21m x 75m (69ft x 246ft) structure for the best part of six and a half months a year. It provides over-wintering and lambing accommodation for the Scotch half-breds, plus post-lambing housing, weaning and fattening facilities for the rest of the flock.
Most polytunnel structures comprise a single span with a walkway or tractor passage down the centre. But this £20,000 installation (including internal fittings), is a triple-span design with two 8.5m (28ft) wide bays either side of a 4m (13ft) wide passage that provides feed and bedding trailer access between home-made wooden mangers.
"Before the polytunnel was installed, we had to move animals between different cattle buildings on the farm just about every day during lambing," explains Mr Moffat. "Now, apart from transferring ewes from conventional buildings barely 15m away, the whole operation is self-contained from when lambing begins to when the last lamb is drawn."
The sheep are housed from mid-November, with the later-lambing ewes occupying part of the polytunnel, and the main group of cross-breds in conventional buildings alongside. Ewes are shorn to make best use of available space and fed on a straw diet with a concentrate based on grass and lucerne nuts.
Lambing starts at the beginning of January; ewes are put in individual pens which are progressively removed to form groups of 10 ewes before the flock transfers – as numbers increase – to the polytunnel in groups of 160.
"At this stage, the flock is on a complete diet of maize, lucerne and molasses, plus 0.75kg of a soya-rape blend and 1kg of caustic treated wheat. Ewe concentrate feeding ceases after four weeks," explains Mr Moffat.
"Lambs have access to creep feed in a passage formed along the rear of the pens by an internal plastic netting division. But they also pick through the ewe diet which gets them used to the feed."
By the end of lambing – around Feb 10 – the polytunnel is home to some 640 ewes plus lambs which are drawn for Chittys to supply Waitrose from mid-March. The latest lambs go off the farm in early June.
Despite the large numbers, the plastic-clad structure has provided excellent accommodation, says Mr Moffat, with no pneumonia or other health problems that could be associated with housing conditions.
"We did have some ventilation panels cut into the roof of the main bays after the first year," he comments. "But, otherwise, the housing has performed as expected."
Trees down one side of the structure and an earth bank screen down the other may have contributed to a lack of cross-ventilation through the Tensar netting walls. But the roof vents – roughly 2m x 0.75m (6ft 6in x 2ft 6in) holes cut into the Visqueen plastic, framed in wood and left open – have cured the deficiency.
"No appreciable amount of snow or rain comes in but they make enough difference on a warm day to be worthwhile," says Mr Moffat.
Careful driving on the part of the telescopic handler operator – the house is cleaned out half way through its occupation and again at the end – has meant damage has come from external sources only.
"Some high winds took a bit of roofing off a nearby building and it sliced through the plastic," says Mr Moffat. "It was repaired easily enough and we were surprised at the suppleness of the plastic after four years."
Ultra-violet light will eventually cause the plastic to become brittle and prone to splitting. But, according to the polytunnel manufacturer McGregor, it should remain serviceable for up to five years or more (it is guaranteed for three years) before needing replacement.
The polytunnel at Wallops Wood Farm is in use for six and a half months a year says manager Frank Moffat.