Calves can be fed elevated levels of milk replacer safely and this approach also offers health and growth-rate benefits, as well as improving heifers’ lifetime productivity.
TEXT PHIL EADES
Ensuring calves get off to the best possible start and optimising pre-weaning growth are the foundations for lifelong health and performance, reduced age at first calving and total rearing costs, and lower total farm emissions.
Feeding elevated levels of milk replacer is an effective way to optimise pre-weaning performance, according to Trouw Nutrition GB’s Laura Tennant. She says that new research is helping dispel many of the myths surrounding how much milk replacer can safely be fed. Research commissioned by Trouw Nutrition GB asked producers: how many litres of milk or milk replacer do you feed at the high points of your feed curve?
The results showed that 65% of respondents still feed six litres, or less milk, replacer per calf per day, with only 11% feeding eight litres or more. “But to achieve increased calf health and performance, calves need to be fed a minimum of eight litres of milk per day,” says Dr Tennant.
Organ development
“Feeding calves milk replacer as close to appetite as possible optimises the development of their key organs, including the liver, kidneys, gastro-intestinal tract, and mammary tissue. Milk allowance is the main driver of gut health both pre- and post-weaning, and feeding calves well sets them up for the future and ensures better lifetime performance.”
Dr Tennant says the usual issue raised by producers when urged to feed more milk is concern that the abomasum may be overloaded, resulting in milk replacer passing into the rumen. But she points out that the abomasum is actually able to significantly increase capacity, allowing greater milk intakes.
“Research shows that three-week-old calves will voluntarily consume up to between six and eight litres of warm milk in one meal without milk entering the rumen or any indications of abdominal pain or discomfort.
“So traditional beliefs about restricting the volume fed per meal to prevent the possibility of ruminal overflow are incorrect. Producers can actually feed significantly more milk per meal. Increasing total daily intakes offers a myriad of benefits.
“The abomasum actually has the capacity to accommodate fluids significantly greater than two litres at a time, acting like a stretchy ballon,” she explains. “Studies also show that calves have the ability to slow down the rate of abomasal ‘emptying’ to control blood glucose. So calves can self-regulate.
“If calves will readily consume more milk, and in so doing achieve higher total dry matter intakes, then it makes sense to make the most of this opportunity. But the feeding management has to be refined to exploit this opportunity.”
The start point is to select a milk replacer formulated for feeding at elevated levels. Dr Tennant explains that the closer a milk replacer resembles cows’ milk, the more closely it will support calves’ biology and meet their nutritional needs.
Many commercially available milk replacers contain more lactose and less fat than bovine whole milk. Most milk replacers are typically low in fat, on a dry matter basis, compared to whole milk, which is around 30% fat. High lactose can be a particular problem as it accounts for 50% of the osmolality of milk replacers. Osmolality is a measure of the concentration of particles in a solution and is calculated by adding the concentration of sugars, such as lactose and minerals.
“The osmolality of cows’ milk is close to 300mOsm/kg and significantly increasing or decreasing osmolality from this target level can impact digestibility and increase the risk of gastrointestinal problems and enteric infections, including nutritional scours,” says Dr Tennant.
Having selected an appropriate milk replacer, she says producers should follow a milk-feed curve and refine calf-feeding protocols, and stresses the importance of building milk intakes quickly. “Aim to be feeding eight litres per day by the end of week one because this will help train the abomasum and develop the metabolism of the young calf.
“Calves will have no problem drinking high volumes of milk. If left on the dam they would be consuming between 10 and 15 litres per day by end of week one. Feeding frequency, however, must be more than once a day. Sufficient intakes can be achieved on twice-daily feeding, providing there’s sufficient time between feeds.”
Dr Tennant also says that calves should be fed using a teated bottle or bucket. “Feeding from a flat-bottomed bucket with no teats will not allow high volume intakes or satisfy the suck reflex,” she explains. “And the oesophageal grove has to work against gravity because calves will drink too fast.
“Meals also need to be far enough apart to feed high volumes, ideally with 12 hours between feeds. If this is not possible then look at amending portion size. Portions don’t need to be the same size in the morning and afternoon if achieving a 12-hour interval is difficult. For example, three litres could be fed at 7.00am and five litres at 3.00 or 4.00pm.”
Dry-feed consumption
It is also a misconception that higher milk-feed rates suppress dry-feed consumption. Feeding more milk is actually important for rumen development because it will stimulate calves to eat more concentrate, which is essential for effective weaning.
Dr Tennant advises a three-week weaning period with an initial step down in milk fed followed by a gradual decline. She emphasises that calves should be eating 1kg concentrate per day at the start of weaning, building to between 3kg and 4kg per day by the end of weaning (see Figure 1).
Black line = milk feed per day
Blue line = calf starter
Figure 1: Recommended feed curve for elevated milk intakes and
optimal calf development
“It is vital to monitor performance and progress to ensure calves stay on track. Calves should be weighed at birth, at three and six weeks old, and at weaning,” she says. “Use the data to measure how well they are performing, looking for a minimum daily liveweight gain of between 0.8kg and 1kg. And monitor concentrate intakes closely in the run-up to weaning to ensure they are sufficient to allow calves to be weaned.
“Science clearly shows the benefits of feeding more milk replacer and, by fine-tuning of feeding management, there is no reason why it cannot be adopted on all dairy units,” Dr Tennant concludes.