Which type of cubicle kerb design best cuts sand loss?
By Jonathan Long
BEFORE considering sand as a bedding medium, producers must consider what effect sand losses of 1.5-2t/cow/year are going to have on their slurry handling facilities and housing design, according to Graeme Lochhead of GFA-RACE.
"There is no doubt that housing cows on sand cubicles reduces mastitis incidence. However, losing up to 2t of sand/cow can cause untold damage to slurry scrapers and pumps."
Following recent high straw prices there has been increasing interest in sand as a bedding medium, particularly in larger herds where all year housing is becoming common practice, says Mr Lochhead.
"With renewed interest in sand and increases in herd size, it is important to find ways of minimising sand losses, particularly where herds use automatic slurry scrapers."
Essential to minimising sand losses is cubicle kerb design, without an effective retaining kerb large quantities of sand are lost to the slurry pit.
However, achieving a suitable kerb design for sand is something which has received little attention in the past, explains Mr Lochhead.
"Designing a new 550-cow sand bedded unit for the Institute of Animal Health at Compton, Berks, provided an opportunity to work on kerb design.
"With a herd of that size automatic scrapers were the only sensible choice; tractor scraping would be too time consuming. However, sand wear on the systems moving parts and its impact on slurry storage and spreading facilities meant we had to keep as much sand as possible in the cubicle," he says.
To assess sand retention with a series of kerb designs, Mr Lochhead set up eight trial cubicles with four different kerbs. "The cubicles were identical in every other way, and included an 200mm (8in) deep sand bed."
The first design tested and the simplest to install and maintain was a 15mm (0.6in) thick steel plate. While the design was simple and relatively cheap, there is no depth of kerb for cows to step on and large sand losses were experienced because cows tended to play with the bedding material at the kerb edge, reports Mr Lochhead.
"This kerb is ideal from both an installation and maintenance aspect, and is particularly suited to automatic scrapers because it gives a clean straight edge for scrapers to work against. But large sand losses experienced with this kerb limit its potential."
The second kerb to come under the spotlight was a 150mm (6in) concrete kerb with angled top edges and a stainless steel sleeve. Results from this kerb are encouraging, with less sand loss than the steel plate, explains Mr Lochhead.
"Cows tended to knock the sand out of their feet when they stepped onto and off the kerb, helping to keep sand in the bed. The stainless steel cover also helps with scraper performance, giving a clean straight edge for scrapers to work against."
But stainless steel is expensive and cost is a major factor in limiting its use in cubicle kerbs, adds Mr Lochhead.
With an eye on keeping costs down, while capitalising on the benefits of the second kerb, the third kerb uses the principles of the second design, but without stainless steel.
The kerb is a 150mm (6in) deep concrete kerb with an angled top lip on the scraper passage side, this design gave better sand retention levels than the stainless steel kerb and resulted in significantly less sand gouging than had occurred in cubicles with the first kerb.
The final design to be trialled was a standard road kerb. "These were put in almost as a control cubicle as we already had previous experience of working with them," explains Mr Lochhead.
While the road kerbs were cheap to obtain and easy to install, they did not match the purpose-designed concrete kerb for sand retention.
Losses of sand from cubicles will never be eliminated, but limiting losses with kerb designs has to be the best method of saving wear and tear on slurry handling systems.
"There is no doubt that sand is going to be lost from beds. The aim must be to minimise sand losses, so repair and replacement costs on slurry handling systems can be kept to a minimum."
Final choice of kerb for the IAH unit was the third design, although Mr Lochhead is keen to try the first design in greater numbers to assess its long term potential. "This design kept losses to a minimum and is relatively cheap to install," he adds. *
Graeme Lochhead, of GFA-RACE, says a 15mm steel plate (top left) may be cheap and simple, but it allows cows greater opportunities to play with sand and results in larger losses. A 150mm deep concrete kerbs (bottom left) came out best in the trial and will be installed in the new IAH dairy unit.
• Angled front lip.
• 150mm (6in) deep.
• 200mm (8in) high.
GRA-RACE will be exhibiting at the Dairy Event. See the Official Guide in next weeks issue.