Dr Jean Margerison, specialist in dairy nutrition at Massey University, believes giving calves the right start in life will pay dividends when they make it into the milking herd. Maximising liveweight gain in the milk-fed phase of the heifer rearing process presents an unrepeatable opportunity to boost udder development and subsequent milk yield.
“At that stage the mammary is going through quite a special stage,” she said.
“It is growing as fast as the calf and there is plenty of research that clearly shows that growing calves faster prior to weaning will give them better mammary development.”
Research showed that higher growth rates – daily average liveweight gain in excess of 600 grams/day – resulted in improved growth of the udder with more milk-producing parenchyma tissue.
“Fat lay down is more likely to occur at puberty, and that will occur at around about 40% of mature weight. The faster you grow, the sooner you get there – but you are not likely to get there during that milk feeding stage. It is a fabulous, one-off opportunity.”
Growth rates vary with breed. Jersey calves will grow more slowly than Friesians. Margerison said proportionally, weaning weight should be about double the birth weight.
“If you are averaging 650g/day in a Jersey and 750g/day for Friesians, you are doing well. Each additional kilo of liveweight gain during the milk feeding period increases the milk yield of heifers.”
Some calves will actually lose liveweight in their first week, with most probably only growing about 200g/day in the first and second week. This liveweight gain increases linearly and towards weaning they will be gaining 1kg/day.
It can be tempting to feed ad-lib milk to maximise liveweight gain. However, Margerison warned that prolonged feeding of high milk levels combined with the high fat content of New Zealand milk would leave the calf’s rumen poorly developed. This would mean at weaning the calf would suffer weight loss and struggle to transition onto a pasture and meal diet.
“You do not want to be using a lot of milk to drive liveweight growth, end up with poor rumen development, and then lose that liveweight when you wean them. You end up paying twice and milk is very expensive.”
A calf can consume about 10% of its liveweight daily in milk, so a 40kg calf can consume about four litres of milk initially. As the calf grows this can be increased to 5-6l, but much more will reduce meal intake and rumen development.
“If it doesn’t eat meal then you will get very poor rumen development – when you wean it, it doesn’t have the digestive system developed to eat what it has got to eat, pasture and some meal.”
If adopting ad-lib milk feeding, backing off the milk at some point to ensure meal uptake three to four weeks pre-weaning is critical for success.
Ideally, calves should be on ad-lib meal and fibre rations.
“It is doing you a favour and is much cheaper than milk – you want the calf to be limiting it, not you.”
‘You do not want to be using a lot of milk to drive liveweight growth, end up with poor rumen development, and then lose that liveweight when you wean them.’
The use of pre- and pro-biotics is becoming more common. Margerison cited research undertaken at Massey that showed calves tended to put more weight on in the first few weeks of life when receiving them.
“Always look for products that have got good quality published research behind them, otherwise you do not know if they are going to work or not – there is no proof,” she said.
“You are looking for good quality, peer-reviewed research that clearly states a statistically significant improvement was achieved. If it wasn’t significant from a statistical point of view you have not got a good proportional chance that it will work for you.”
The critical first 12 hours
Getting that feed of fresh, good quality colostrum within the first 12 hours of life for a calf is critical for getting off to a good start.
“Our calf rearing systems, the fact that we have so little shed space by and large, we have a turnover of calves going into it, increasing disease challenge, that we calve in potentially hard wet conditions in spring, sets up a whole bag of challenges for the calf,” Dr Jean Margerison said.
Calves are born without any level of immunity to disease. Ruminant placentas are incapable of transferring antibodies from the dam. For the first 12 hours after birth a calf is able to absorb antibodies – the immunoglobulin proteins in fresh colostrum – through the gut wall, into the blood. After six hours, a barrier to this absorption starts to develop. After 12 hours, this barrier is almost complete although the antibodies in colostrum offer some protection by neutralising some pathogens in the digestive tract.
The first feeds should be from good quality colostrum, collected from cows milked within 12 hours of calving – effectively their first milking. The concentration of immunoglobulin in the milk declines post-calving, meaning the calves will not be able to absorb enough given the volume of milk they are able to consume in a day.
Margerison said colostrum should be fed fresh, or if not used straight away it should be refrigerated to prevent bacteria developing and heated gently prior to being fed.
Colostrum could be pooled and stored to be fed to older calves with refrigeration or through the use of a colostrum keeper, which would acidify the milk to restrain bacterial growth.
Feeding regimes depended on what system best suited individual farming operations. She recommended twice-a-day feeding for at least the first week while the calves were being transitioned on to whatever form of milk – stored colostrum, wholemilk, milk replacer – they would be reared on.
Tube feeding the first colostrum was acceptable if carried out by an appropriately trained person to ensure correct administration, although her preference was to use it only in situations where calves clearly had empty bellies and refused to drink.
Collecting calves twice a day – earlier in the morning and later afternoon – and feeding newbies soon after collection should ensure colostrum requirements would be met.
The importance of fibre
While indoors, calves also need access to fibre.
Dr Jean Margerison said fibre helps rumen development by sloughing off the keratin coating that covers the developing rumen wall, specifically the papillae – the tiny finger-like projections that increase surface area. Recently completed research at Massey University showed that hay performed the task well with no improvement in growth rate feeding other lower neutral detergent fibre, higher protein fibre options.
“We were looking into it because in the background there have been some saying calves could consume too much fibre, subsequently limiting intake. Anything fibrous is going to reduce feed conversion efficiency per kilo – but in a calf, the point is what that fibre does and most of all how fast the calf grows.”
Margerison said outdoor calves benefited from being offered meal and fibre, as long as it could be protected from the rain.
