DairyNZ’s interest in calf welfare prompted it to look at calf shed bedding, after farmers started using river stones, particularly where sawdust was in short supply.
Conducted by Agresearch, the work started with monitoring calves reared on river stone or sawdust on a South Island commercial dairy farm in spring 2013.
They found that calves reared on river stones spent about an hour less lying down each day, played less, and had lower skin surface temperature.
Skin temperature is indicative of the thermal properties of the bedding material. This is important because calves reared in colder conditions might need to expend more energy to keep warm. The calves found the stones less comfortable, and in cold areas the stones didn’t have the same thermal properties as sawdust.
Leg health issues like lameness and joint inflammation were observed in further studies and calves on stones wore the hair off their knees. While sawdust was regarded as a better bedding material, it could be expensive, hard to get hold of, and must be managed properly.
The next step was to look at sand, as used in European and United States cattle systems, pea metal, which has good drainage properties, and chipped recycled car tyres, as used in horse arenas.
These were compared with sawdust, at AgResearch’s Tokanui research dairy farm.
There was no significant difference in lying behaviour or physiological indices of stress, such as cortisol levels, between the groups. But the calves’ skin surface temperature was a little lower on the sand and pea metal, as expected because of the lower insulatory properties of these substrates.
Some farmers reported crusting of sand which limited drainage, but that wasn’t observed in the trial because calves kicked it up and kept the surface relatively fresh.
Chipped car tyres must be passed through a magnetic field several times to remove wire, increasing the cost. River stones can differ greatly in size and shape depending on their source. Stones from the South Island are often flat and smooth, whereas the North Island stones are more like quarry stones.
“Management of any calf bedding material is critical,” AgResearch senior scientist Dr. Mhairi Sutherland, who led the research, said.
“No matter what the bedding material, it should be comfortable, and it is important to have good drainage to keep the surface dry. The stocking density should be reasonable, and for sawdust, adding fresh material regularly will help to keep the surface clean and dry”.
The influence of colostrum quality, quantity, and age on calf health and growth rate is generally accepted. But colostrum quality varies between cows, between seasons, and drops rapidly within hours of calving. A correlation between colostrum quality and hygiene of the milking plant, vat, and feeder has been observed. Farmers can’t assess which cows have high-quality colostrum suitable for newborn calves, and which produce lower-quality colostrum more suitable for older calves, because there’s no suitable cow-side test.
This is the ultimate aim of research being done at Massey University’s Dairy 1 Farm, led by senior lecturer in dairy production Dr Penny Back. Her own experience rearing calves to pay her way through university and her dairy farming interests provided some of the motivation.
“Many farmers find they follow recommended feeding guidelines but their calves fail to reach target liveweights,” Back said.
“Calves have no antibodies at birth, so they depend on colostrum for this, as well as energy from the high fat and protein content. All the immunoglobulins (IgGs) that a cow has are parked ready in the udder, ready to go once she calves, and it plummets once she is milked”.
Colostrum is the first and one of several important steps to healthy calves and meeting target weights.
Background work to developing a quick and easy cow-side colostrum test has included setting IgG levels for colostrum suitable for newborn and older calves.
Values recorded in New Zealand are often lower than those recorded in overseas research. In NZ, research has been done on commercial farms at the first milking, which might be up to 24 hours after calving. In overseas research, under more controlled conditions, the test may be made soon after calving.
“It is appropriate that calibration is based on the actual NZ dairy situation,” Back said.
Other background work included the relationship of IgG of dam’s colostrum, bulk colostrum, and calf serum (blood).
Some calves don’t get good colostrum from mum, but do from the bulk colostrum. Others can get good quality colostrum but don’t have high serum IgG levels. These have failure of passive transfer (FPT).
Central to this research has been a handheld Opti Digital refractometer, also known as a Brix meter, which determines IgG level by measuring the refracted light to which the sample has been exposed. The farmer need only turn it on, add the sample and read the result, which would indicate whether the colostrum was fit for newborns or older calves. These instruments retail at $488.
“Collecting this data would possibly be viewed by farmers like weighing calves. It’s seen as another job at a busy time of the year, but once the numbers make sense and become very useful, it becomes addictive, much like a golf score,” Back said.
The researchers sampled cows’ colostrum from test buckets. Farmers could do this too but a quicker, more convenient test might be possible by stripping foremilk samples. Before the cups were attached, high-quality colostrum for newborn calves could be directed to test buckets, or lower-quality colostrum for older calves could be directed to the colostrum vat. The correlation of colostrum quality between stripped foremilk and colostrum collected in a test bucket has yet to be established, and is key to the success of this proposal.
Like most dairy veterinarians, Te Awamutu-based Emma Cuttance attends many calf health problems. A Sustainable Farming Fund and DairyNZ-funded project is looking at calf health in NZ dairy herds, with a focus on colostrum and FPT.
The research group surveyed 106 farms across nine regions, with 4000 calves studied from birth to weaning. They found a third of the surveyed calves had FPT, with a prevalence range between farms from 5% to 80%. Calves from older cows were more likely to have FPT, possibly because older cows have a greater volume of colostrum, which dilutes the IgG content. FPT was more common in calves born in the peak of the calving season, presumably because of staff workload.
South Island calves had a higher incidence of FPT. While they are unsure why, it might be influenced by cow-staff ratio, or transition feeding from crop to calving influencing cow colostrum.
Further work needs to be done to find out why this difference is occurring. Some of the farms that leave the calves on their mothers had the lowest incidence of FPT. While tube-fed calves had a higher incidence of FPT than dam or bottle-fed calves, Cuttance was quick to point out it wasn’t the administration method that was responsible.
“It was not necessarily the feeding method, but that the colostrum being tube-fed could only be described as very poor quality. Only 9% of all the colostrum samples taken had a high enough IgG level for newborn calves, and only 8.5% had acceptable contamination levels.”
Colostrum IgG levels could have been low because colostrum was pooled, with the poorer-quality colostrum effectively diluting the better-quality product.
Even if farmers pooled just first milking colostrum this was likely to happen because of differences in colostrum quality between cows. Contamination is caused by poor hygiene practices. The nature of colostrum and lack of refrigeration mean it’s an ideal medium for bacterial growth. Everything that comes into contact with colostrum must be kept scrupulously clean by scrubbing, hot water, and detergent-sanitisers. This includes drums, lids, and stirrers.
“If you wouldn’t drink it, then don’t even think about feeding it to your calves,” Cuttance said. For colostrum being stored, preservative must be added.
While calves with FPT were more likely to get sick, in this study there was no significant difference in weaning weights. Of the 4000 calves initially studied, 1800 would be followed with three-monthly weighing, and pregnancy statistics and first-year production recorded and analysed.
Cuttance’s advice was for farmers to blood-test their calves to determine the prevalence of FPT. If they had a high rate of FPT, colostrum quality and the factors which affected this needed to be checked.
An update of this work will be presented at DairyNZ’s CalvingSmart workshops, which will be run throughout the country from early June to mid-July. They will include best practice and latest research for calves up to four days old. Details are on the DairyNZ web site.
One more thing about calves:
It might be tough times on the dairy farm, but for some Kiwis life has challenges all the time. Let’s hope NZ dairy farmers will continue their wonderful support of the IHC calf scheme this year.
