Polytunnels for livestock are often seen on sheep farms around lambing time, but they are also being used to provide ideal conditions for calf rearing.
The environment in which calves are reared is fundamental to the health and performance of those animals.
With this in mind, when Martin Edwards looked at doubling the size of his calf rearing business, he looked at a range of different building designs and set-ups before embarking on two three-span polytunnels.
Mr Edwards, who farms at Yewdale Farm, Garstang, Lancashire, explains the two 38-metre by 22.5m structures can each accommodate 200 calves.
He is also using existing sheds to rear calves, so at any one time he can have up to 700-head on the farm, giving him an annual throughput of about 2,000 calves.
He explains: “We have been rearing calves for Dunbia’s integrated supply chain for five years, but after two years of doing it we decided to double the size of the operation.”
To gain ideas for new calf accommodation options, Mr Edwards visited some units in Scotland.
He says: “We saw all different types, ranging from very high tech to much more low-tech options. But the best calves we saw were in polytunnels.
“I had already seen calves reared in polytunnels while on holiday in New Zealand and I liked them over there too.”
The polytunnels at Yewdale Farm have now been up for about 18 months, and Mr Edwards is pleased with how the calves are performing in them.
“The polytunnels are light and fresh. There are no damp, dark corners like we have in our original sheds.”
And Mr Edwards says this environment is also producing good results.
“We are seeing better growth rates, and less disease and mortality,” he explains.
Mr Edwards adds the calves reared in the polytunnels perform better than the calves reared in the farm’s existing sheds and are achieving, on average, 0.2kg more in terms of daily liveweight gains.
The calves arrive at Yewdale Farm at two to three weeks of age, at a minimum of 50kg and leave at 16 weeks old. Most come from local dairy farms and Mr Edwards says he aims to have a batch of up to 100 calves all settled into a shed within nine days.
On arrival the calves are BVD tag and tested, vaccinated for pneumonia and are given an electronic eartag.
Calves are fed powdered milk replacer for the first four weeks they are on the farm, with access to an ad lib cereal-based ration. During this time they are in the ‘milk’ polytunnel, which houses 14 pens of 14 calves.
Mr Edwards says: “For feeding the milk, we have a 500-litre tank which we put the milk in, and then pump it down a pipe into reservoir compartment feeders.”
Calves are weaned gradually and then moved into the ‘weaned’ polytunnel, where they are batched in four groups of 50. Here, they stay on the cereal-based ration, along with straw.
Everything is weighed on arrival, and then after three to four weeks to make sure growth is on track for weaning, and then again after calves have been on-farm for 12 weeks.
Mr Edwards says: “The EID tags means weights are easily recorded into our farm management software.”
Average daily liveweight gains is normally about 1.2kg and Mr Edwards says mortality rates are less than 0.5 per cent.
The structures themselves cost about £20-25 per sq.metre, which includes erection costs, and Mr Edwards estimates it has cost about £140,000 for the two structures at his unit.
But he says the extra cost was due to him spending more on the concrete base and pre-cast concrete panels, which form the lower part of the polytunnel sides.
“It is possible to do it much cheaper, but I spent a lot on levelling, stoning and concreting the base which falls away to dirty water drains and tanks.
“I also wanted to be able to easily wash and disinfect the buildings in between batches, so went for pre-cast concrete panels to clad the sides.”
While lower overall building costs are often a consideration when leaning towards polytunnels rather than a conventional calf house, Mr Edwards says he strongly believes the polytunnels provide calves with an optimum environment.
He says: “Cost was part of it, but I was not purely looking for the cheapest option. I wanted to double the number of calves I was rearing, but also do a better job of it.”
Ventilation in the structures is provided by 1m-high mesh sides positioned above the 1.2m-high concrete panels.
“The mesh provides a wind reduction of about 40-50 per cent, so it prevents any drafts but still lets some air in”, says Mr Edwards.
This is supplemented by positive pressure ventilation fans installed at one end of the polytunnel, which blow fresh air along polyducting and downwards into the pens.
Roof-mounted extractor fans also removes stale air out through the roof, and can be used to reduce any excess heat during warmer weather.
Mr Edwards says this all helps keep the air in the structures fresh.
"It is all about having good air flow. This helps keep the bedding dry and takes the dampness out of the air. As a result we are seeing much less pneumonia.”
Mr Edwards says so far there has been no problems with high temperatures, with the white polythene used to cover the structure providing significant shade, about 30-35 per cent, as well as good light transmission.
He says: “On really hot days, it is actually cooler in the polytunnels than outside.
Looking ahead, Mr Edwards is set to increase the throughput further, and has plans to put up another two polytunnels to accommodate a further 400 calves.