Yattendon’s Farms Director Alastair Jeffrey takes up the story: “Some years ago we spent a lot of time studying the optimum size for our herd. We knew that we needed to achieve milk production of 4.5 to 5 million litres annually. Based on a yield of 8,500 litres per cow, we settled on a herd size of 550 cows.”

To accommodate the cows a new shed was completed in Autumn 2002. Like everything else on the 3,628 hectare (9,000 acre) Yattendon Estates, it exudes a sense of quality and good design. “The people who designed the shed took care to get as much light in, and foul air out, as possible,” Alastair explained. “But right from the start we saw problems in the herd including high levels of mastitis as well as fertility issues with cows not coming into calf.

“We suspected it was a heat stress problem as the atmosphere in the shed could be stifling when the temperature rose. On days when temperatures on the roof of the building reached 24 - 28 degrees C, we found that the ‘stack’ system – designed to take hot air up and out – was actually going into reverse and trapping hot air in the shed.

“The need to improve ventilation was clearly urgent but it was likely to require significant investment. To make the case for this we commissioned a study from a firm of consultants, which initially was inconclusive.”

At about this time Adrian Moore suggested the Megafan, which T H White has been importing from the USA and installing with very successful results. These virtually silent 24ft diameter, low speed fans shift high volumes of air, and although capital costs are higher than conventional box fans, the running costs are massively less.

Alastair Jeffrey then called in Red Engineering, prepared a thermodynamic model of the building which fully

So, much of the Yorkshire boarding was first removed from the sides of the shed, opening it up to achieve the maximum possible ventilation through convection alone. Then, with the expenditure approved, T H White installed nine Megafans – three in each aisle of the shed – a £45,000 installation which is the largest in the UK so far.

Moving air from the Megafans breaks up the moisture-saturated boundary layer surrounding the cow’s body, accelerating evaporation to produce a cooling effect.
On hot days a Megafan will equalise uneven temperatures that occur at different levels in the shed’s air space, forcing unused heated air from the ceiling down to floor where it can have a positive impact. This heat differential can be in excess of 9 deg C from ceiling to floor.

“Since the installation was completed in May the results have been dramatic,” enthuses Alastair. “The atmosphere in the shed is cool and fresh, the cows are relaxed and content and milk yield has already increased by 0.68%, or 91 litres per cow per annum!

“Perhaps best of all is that the current running costs are just £6.46 per day for all nine Megafans. With energy prices soaring that will give us huge savings and make it even faster to recover the capital costs.
“We leave the Megafans running all the time – even at night – and we will probably leave them running on many winter days too, especially when we get still, foggy or damp conditions.

“T H White has really made a difference to our business over the last year,” concludes Alastair. “Every time you have a problem and pick up the phone to them, everything just seems to be sorted.”
A happy customer then!

For further information on dairy installations from T H White, or the Megafan, call Adrian Moore on 01373 465941 or 07860 247376.