Based on farmers’ experiences it appears they’re also a much more permanent fixture than the typical sawdust bedding. Many haven’t replaced the stones they put in originally up to five years ago and say there’s no sign they will need replacing any time soon.
A combined DairyNZ and AgResearch study is backing up what a growing number of farmers are finding, with no animal health or welfare issues coming to light (Dairy Exporter, August, page 136).
Waikeria Prison, south-east of Te Awamutu, has used the system for five years and still has the original stones. The 2700-cow operation’s farm manager Jimmy Emery said 750 calves were reared every year on the stones and rather than having any detrimental effects, the bedding looked to provide advantages. Unlike sawdust the rocks don’t get soggy and stay damp, draining quickly and retaining heat from the sun.
“They’re a bit like hangi stones. When you put your hand down on the stones where a calf’s been laying it stays warm for quite a while,” he said.
Five years ago the Corrections Department upgraded the calf pen facilities and put in the stones, having seen they were working well for others. Emery said they appeared to tick all the boxes in terms of animal health and welfare, as well as cost and reducing workload.
It’s important to put the work in setting up the system. Good drainage needs to go in, with a layer of about 250-300mm of washed river stones laid on top. To make good bedding the stones must be a specific size and shape and must be washed to ensure there are no silty fines attached, which can turn to concrete once wet.
Stones about 40mm in diameter are ideal, rounded with no sharp edges. If they’re much bigger or smaller they become uncomfortable for the young animals and difficult to walk on.
Emery said the previous sawdust bedding had to be dug out and replaced two to three times over the calf-rearing season, while no one has had to touch the stones since they were put in.
The area where the feeder sits was open to the sky, so rain washed away most of the excrement deposited and the action of kicking up the stones as calves moved around the pens created a self-cleaning effect across the rest of the pen, he said.
“If we had to I guess we could get the high-pressure hose on the stones to clean them off but we’ve never had to. They look just like they’re brand new.”
Emery said they had watched the health of the calves closely and there hadn’t been any increase in foot problems or other issues.
“There’s no smell of ammonia in the sheds, the calves are happy and I think they probably do better on them,” he said.
Southland farmers Philip and Denise van der Bijl and their daughter and son-in-law Yvonne and John Lang have used washed river stones in their calf pens for five years and have found the calves have done just as well, if not better, than when they used sawdust.
They also rear calves on a big scale, with 750 going through the sheds each year – 450 replacement heifers and 300 bull calves.
They farm in north-western Southland, 17km south of Mossburn. The weather at calving can be challenging, with snow, icy driving rain and frosts, so it’s important that new-born animals are warm and dry.
Although the grey river stones intuitively seem like a cold, hard bed for a young calf the animals show no signs that’s what they experience.
Philip said they made the move to river stones after hearing about them from friends in Taranaki. Sawdust had become difficult to find, with the type that was most readily available too fine.
“We got to the point we had to rotary hoe it all the time so it wouldn’t turn to a slurry,” he said.
It was wet and mucky and maintaining it through the busy calf-rearing season just added stress and workload.
They replace their stones every year at a cost of $15,000, or $20/calf reared, but their son Chris, who runs another of the family’s farms in Reporoa, hasn’t needed to replace stones in his calf pens for five years.
“His calf shed isn’t as deep as ours so it gets a lot of sunlight right through to the back of the pens. It’s also sitting on pumice soils so drainage is good,” Philip said.
Last season DairyNZ and AgResearch carried out a study looking into the stones and used the van der Bijls for the investigation. DairyNZ animal husbandry and welfare team leader Dr Nita Harding said 20 calves were monitored on the river stones and 20 in neighbouring pens that had sawdust as a bedding.
The calves’ temperatures and the ambient air temperatures were taken at regular intervals throughout the day and night over a period when the calves were about one week old, with similar recordings carried out again when they were six weeks old.
Harding said the health and behaviour of the animals was also observed and recorded, along with the cleanliness of the environment and the calves. Animal health was also monitored.
The idea of using river stones as a bedding seemed counter intuitive to good husbandry but no detrimental effects on the animals could be found, Harding said.
The study has continued on a Waikato farm this season and has expanded to look at three stocking rates – 1m2, 1.5m2 and 2m2/calf over an eight-week period rather than six weeks, with growth rates also recorded.
Early indications from the research suggest no significant problems with the stones compared to other beddings. However, detailed analysis of behaviour through video recordings was yet to be completed, Harding said.
Anecdotally farmers had reported that in terms of health and hygiene calves were easier to manage on stones and their animals did just as well, if not better, on them, she said.
But it had been important to collect objective, scientific information to ensure those reports could be backed up and the Ministry of Primary Industries (MPI) animal welfare (dairy cattle) code of welfare minimum standards was being met.
Not only was it important to make sure animals were being well cared for but the sound evidence could be needed to defend the practice from detractors.
