22 October 1999

Sandy beds might be best

Sand, dry cow housing and

breeding may help in the

battle against environmental

mastitis. Marianne Curtis

reports from the British

Mastitis Conference

BEDDING cow cubicles with sand could help to cut mastitis considerably.

But for producers sticking with straw, care should be taken to ensure it arrives dry, says independent consultant John Hughes.

Speaking at the British Mastitis Conference, Mr Hughes explained the merits of using sand as a bedding material. "Washed sand is a very safe material for cows. It is inert and provides no means for bacteria to grow, minimising exposure of the teat-end to bacteria.

"Although straw yards offer many welfare advantages, especially in the control of lameness and reduction of stress there is an increased environmental mastitis risk."

Mr Hughes believed there was a strong argument for housing dry cows and heifers in sand-bedded cubicles to a depth of 10cm (4in).

Conditioning sand daily by raking is essential to avoid it becoming hard. It should also be replenished often enough to keep it level with cubicle kerbs, he advised. At calving, he suggested transferring cows to a box bedded with 15cm (6in) sand topped with clean straw.

But using sand may not be practical on every unit, warned Mr Hughes. "Sand can block drains and grind out bearings in slurry spreaders. Slurry lagoons cope better with sand than above-ground tanks because it settles out more effectively."

For producers using straw yards, he said recent MDC-funded research undertaken by Liverpool vet school had highlighted the importance of checking the moisture of bought-in straw. Four farms in Cheshire took part in the study, designed to evaluate straw as a bedding material.

Ideally straw moisture content should not exceed 15%, he said. Although bales bought by producers participating in the study often appeared normal, some tested at more than 30% moisture.

"Straw with a moisture content of more than 20% is useless for bedding and extremely expensive, as more than a third of the purchase is water. Devices are available to test straw moisture content. It is worth checking moisture before unloading straw, and bales with more than 20% moisture must not be used."

Even in yards where dry straw is used, muck beneath the surface heats up causing moisture to rise to surface layers. On still winter days when the relative humidity outdoors is high, moisture cannot escape from buildings.

"When outside humidity is high, the bedding surface can reach 98-100% relative humidity and this can coincide with peak levels of environmental mastitis." Natural ventilation is inadequate in these situations and fitting an extractor fan may be the only way to remove moisture from the building, he suggested.

Allowing adequate space for cows in yards also minimises exposure to mastitis bacteria, said Mr Hughes. "Space allocation for cows should vary with stage of lactation rather than simply cow number because quantity and consistency of faeces and urine production varies.

"High yielding, freshly calved cows need at least 6.5m sq each, 5.57m sq is adequate for mid and late lactation cows and dry cows can remain clean on 4.6m sq."

BEDDINGCHECKLIST

&#8226 Consider sand.

&#8226 Straw moisture should be 15% or less.

&#8226 Consider mechanical ventilation.

&#8226 Allocate space according to lactation stage.