Calf protein benefit is not proven
DAIRY HEIFER calves don’t need the huge hike in crude protein content of milk replacers that US work has suggested, according to research projects in Ireland and Northern Ireland.
Studies in the USA have suggested a benefit in increasing milk replacer protein content up to 30%, closer to that of whole milk. Most current UK milk replacers are about 23% crude protein.
In the USA feeding high protein replacers increased growth rates up to 1kg a day. But researchers and replacer suppliers are concerned about the economics of such rations for UK and Irish heifers and met at the British Society of Animal Science conference in York to discuss recent research.
One Teagasc study in Ireland, reported by Richard Fallon, compared 23% and 30% crude protein milk replacers, both fed at 600g of powder a day and 1200g a day. All milk replacer was fed warm by bucket.
“We saw a response to increasing the level of milk replacer, but not in the level of protein fed.” Calves fed low protein replacer at the higher rate grew at 760g a day up to eight weeks compared with 690g at the lower rate, and averaged 860g and 950g a day to 16 weeks, respectively. On the higher protein rate, growth rates to 16 weeks were 900g a day at the lower feed rate and 990g at the higher rate.
At the Agricultural Research Institute of Northern Ireland two studies fed five litres or 10 litres of replacer with 120g of powder/litre at 23% and 30% protein, through automatic teat feeders. One study used spring-born calves, the other autumn-born, both were high genetic merit.
Researcher Hannah Wicks said both studies show higher liveweight gain in the first four weeks when you feed more milk replacer, but that disappeared by eight weeks.
“And there was no huge benefit from a higher protein content. It doesn”t appear that high milk protein replacer at a low level is any better than feeding more milk replacer at lower protein,” she said.
One potential reason for the difference between US and Irish work is that in the UK some essential amino acids are added to replacer to achieve target levels, said John Twigge of Nutreco Agriculture and Trouw Nutrition. “I am not sure whether they do this in the USA.”
He reckons the amount of milk powder fed is more of an issue than its protein level. “Offering more energy and protein is likely to get a response. In Italy and Germany they feed much more milk powder than in the UK.” He also pointed out increasing protein in milk replacer to 30% would add £70/t to prices.
There are also downsides to feeding more milk replacer powder when it comes to weaning. When more replacer is fed concentrate intakes pre-weaning will be lower, said Mr Twigge.
There also remains the question of what is optimum growth. “In the UK, for some years the aim has been cost-effective growth,” said Maggie Gould of replacer supplier Volac International. “A 23% protein replacer fed at a typical level supports growth of 650g a day. We need to decide whether there is any benefit from growing calves faster in the first eight weeks of life.”
Dr Fallon suggests ensuring daily growth is 750g a day to 12 weeks, which should equal about 700g a day in the first six weeks.
Jennifer Bell of SAC Dumfries reckons it”s worth considering feeding six litres of milk replacer a day to calves to increase growth rates, but not necessarily of higher protein. “However, we cannot say this saves money because these studies don”t yet have lactation results.” These will be reported at a later date.
Miss Bell also added that nutrition is only one element of acheiveing good growth. Other issues influencing growth include when the calf is taken from her dam, number of meals given, volume of milk at each meal, calf housing and stockmanship.