One step at a time ...

Feed CMR and wean gradually to avoid growth set backs

Achieving a 24-month calving age is much easier if calves get off to the best possible start. Sound nutritional management and feeding a calf milk replacer are both key to maximising growth rates and minimising set backs.

Good nutrition in the early stages of a heifer's life will result in greater live weight gains later on, as well as increased milk production in her first lactation. So says Volac's Maggie Gould, citing evidence from global independent trials that have repeatedly demonstrated that heifers fed on calf milk replacer grow more rapidly in the first six weeks of life, can achieve liveweight gains that allow them to calve successfully at 24 months old, and can also produce more milk in their first lactation. "Studies from Denmark and Israel have reported additional yields of up to 1.6 litres more milk per day for heifers that had gained an extra 300g per day liveweight in the first six weeks of life," she says.
"And even the first feed can make a difference. According to trial findings from the University of Arizona, heifer calves fed a higher amount of colostrum in the first hour of life and then reared in an identical manner to those fed the lower amount, went on to produce more milk in each of the first two lactations, which translated into an additional 550 litres of extra milk per cow."

Flying start
She adds that it is essential to remember that the calf is not just a smaller version of a mature cow: "It must be fed in a way which matches its ability to use the feed provided. If liquid milk is restricted to a low level in the first six weeks, then growth will be restricted and this can have knock on effects on future performance.
"Getting calves off to a flying start is all about providing a feeding programme that will take advantage of the calf's huge potential for fast, efficient growth."
Mrs Gould adds that for herds targeting high milk yields, it is essential to choose the right system for rearing the newborn calf, because as the trial findings indicate, feeding the heifer calf for better growth from the moment she is born can have a significant impact on how she performs in the future.
NWF calf specialist James Slater agrees that producers looking to calve heifers at 24 months old need to focus on getting calves off to a good start.
"Calving at two years old is a major factor determining the life time profit of a cow. Over the entire rearing period a calf will need to grow an average of O.8kg per day and how her first 12 weeks of life are managed can have a significant impact on the entire growth period," he explains.

Growth targets
Calves need to grow at an average rate of 4kg per week from birth to weaning. When weaned at around 49 days old she must already weigh 69kg and be able to maintain a growth rate of 5kg per week. As a rule of thumb, if calves are 25 kg heavier than their birth weight they are ready to wean. At 12 weeks old she needs to weigh at least 100kg.
The heifer management system must be designed to achieve these target growth rates. After three days on colostrum calves should receive two litres of milk replacer twice a day for 10 days and building up to three litres twice a day. Mr Slater advises against econornising on sub standard milk replacers. He argues that cheap replacers are cheap for a reason and are often based on poor quality ingredients of poor digestibility. He also advises producers never to feed discarded milk to heifer calves as it increases the risk of enteric diseases. "The time around weaning is absolutely crucial as many calves are not fully prepared for weaning. If, when milk supply is stopped, they are not able to effectively digest the new diet, this will lead to a deficiency in nutrient supply and a fall - or check - in growth rate. "When you expect and need a calf to grow at a rate of 5kg per week you can't afford a check in growth - the calf will struggle to make it up. It is not unusual for calves to suffer a growth check equivalent to two weeks growth or 10kg, when the rumen is not properly developed.
"So to avoid this calves should be consurning around 1kg per day of concentrates for two consecutive days before they are weaned. If intakes are lower than this it may pay to delay weaning."
Mr Slater says it is essential that the rumen is being developed while calves are still on milk and the key to effective rumen development in calves is the early indusion of dry feeds in the diet. "Where calves are fed pellets containing lucerne and other quality fibre sources to achieve a minimum 14.5% NDF, the rumen villi develop more rapidly than where long fibre is the only source available," he adds.

Step weaning
Trials at Writtle College have shown that step weaning cuts calf rearing costs by 12%. Compared with traditional abrupt weaning, step weaning brought substantial savings of 18p per kg liveweight gain, worth almost no per calf over the 10-week rearing period. And step weaning also gave further savings in labour requirements and calf liveweight gain increased by 20% (see table 1).
Three-week-old Continental cross Holstein Friesian heifers were introduced to 23% protein Volac Blossom calf milk replacer fed at 150g per litre in order to achieve higher growth rates than in traditional bucket rearing systems. All calves were fed 2.5 litres twice per day for the first three weeks.
One group continued on this regime until abrupt weaning after five weeks and the other went onto a step weaning system with 2.5 litres fed once a day during week four, reducing to two litres fed once a day during week five. The calves were housed in groups of five in straw bedded pens and offered 17% protein calf starter feed ad-lib throughout the five-week period.
"The step weaned group began to show a weight gain advantage immediately after the mille was restricted to one feed of 2.5 litres per day in the fourth week and concentrate intake increased. This trend was maintained up to and afterweaning," explains Maggie Gould.
"Reducing the milk fed at this stage drives up the amount of concentrate eaten, speeds up rumen development and subsequently enhances growth rate. By the end of the 10-week study, the step weaned calves were, on average, 11.3kg heavier than those abruptly weaned. "And this equates to a substantial and cost effective improvement in performance that cannot be ignored in today's economic climate."

text Rachael Porter
Cow Management, November 11, 2009
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