Recent research is helping dairy farmers re-think calf milk feeding strategies for optimum health and lifetime performance. Volac nutritionist Caitríona Mullin talks about what the future holds.
The dairy industry is starting to wake up to the fact that it may have been underfeeding calves for quite some time, but the next step change will be driven by improvements in the quality of pre-weaning diets fed to the nation’s calves. That’s the view of Volac nutritionist Caitríona Mullin, who says the specialist young animal nutrition company is ready to meet the technical challenge.
“We know that feeding a good heifer calf up to 900g of milk replacer daily may be needed to meet optimum rearing targets – and absolutely crucial if you want to calve heifers down at 24 months. But more importantly, we also know feeding modern dairy calves to this level makes sound economic sense,” she says.
Caitríona points to studies showing that calves gaining 800g a day have the potential to produce 450 litres more milk during their first lactation, compared with calves reared on a traditional system gaining only about 500g per day.
“Research also shows that feeding higher milk replacer levels leads to fewer calves failing to reach a second lactation. So providing the necessary nutrition to sustain rapid growth rates (>750g per day) during the first two months of life should not only result in more efficient and economical heifer rearing, but also deliver greater lifetime milk output when these replacement animals join the milking herd,” she says. She adds that if milk replacer intakes are restricted, calves simply look for nutrition from the other feeds available and invariably this means eating more concentrates.
“But this can limit early growth because the rumen is not developed to efficiently digest solid starter feeds until around four weeks of age,” Caitríona points out.
“Calves on a high-quality, precision-formulated milk replacer are receiving a highly concentrated energy source – so much so that to achieve the same energy intake from a solid starter feed requires a dry matter intake 1.5 times that of the milk. What’s more, further research has shown that there is a large amount of important early life development in the pre-weaned phase. The development of both mammary cells and the gut – and metabolic programming –all take place during this crucial early life period, so feeding high levels of milk enables us to take full advantage. It’s also the time when feed conversion efficiency is at its highest.” The importance of feeding calves more milk has also been supported by recent research at Harper Adams University, albeit with male calves. In this study with British Blue x Holstein and Holstein bull calves, starting at 15.4 days old until weaning six weeks later, calves fed 150g/day more milk replacer were 5.6kg heavier, on average, at 12 weeks of age. “The team at Harper noted that the calves fed higher levels of milk were healthier and had better faecal and coat bloom scores, concluding that this was possibly because their immune status was better. They have also stressed that across all the calf trials they have done, calves recording lower daily liveweight gains never catch up, which really does highlight the importance of the industry capitalising on this highly efficient early growth phase.”
Cold weather Caitríona states that, during cold weather, calves may need to be fed even more milk. “When temperatures fall below 15°C calves under three weeks of age need more feed to hit growth targets and boost immunity.
“Under mild weather conditions (15°C-25°C), for dairy calves to grow at an average of 750g per day in their first few weeks of life they need to be fed at least 750g of milk per day alongside dry feed and water.
“But when the temperature plummets you need to feed more. And if the temperature drops below freezing, daily energy requirements increase by up to 30 per cent.”
She also makes the key point that high moisture levels or draughts just exacerbate the problem. “In fact, draughts of just 5mph can make calves feel 8-10°C colder,” she says. Caitríona stresses that it is vital that all newborn calves receive adequate good-quality colostrum (at least three litres within two hours of birth), whatever the ambient temperature.
“When it comes to milk feeding in cold weather, you really need to step up the level of milk solids by 100g per day for every 10°C temperature drop below 20°C,” she advises.
“This is best achieved by feeding milk more frequently and, in fact, this only mimics natural feeding behaviour when the weather gets colder. If calves are given the choice they will feed at least three times a day – and if given free access to milk, possibly up to 10 times a day – drinking little and often. Keeping bedding plentiful, clean and dry is also important, and consider too the use of thermal calf jackets. By not taking measures to either keep calves warmer or increase nutrition during extended periods of cold weather, you could be compromising animal health through a reduced immune function and daily growth will also be reduced. And it’s important to remember too to maintain good milk intakes even if calves are scouring,” she adds.
Optimise protein quality Caitríona believes that the main priority for dairy heifer calf nutritionists is to convince farmers to feed these valuable milking herd replacements appropriately.
“It is also important to recognise that although water and energy are the first limiting nutrients for the young calf, feeding high-quality protein is also crucial. After water and energy, protein is the next most important nutritional component of the diet,” she says.
“The nutritional requirement for protein in the young ruminant animal – whose digestive system in the first few weeks of life is very similar to a mono-gastric – is better referenced by looking at the availability and digestibility of the amino acids supplied. Breaking this down further, there are essential amino acids that cannot be synthesised by the pre-ruminant calf and these must be supplied in the diet in sufficient quantity to ensure the maintenance of normal bodily functions and growth,” Caitríona points out.
She adds that the absolute amount of each amino acid (in g/day) required by the pre-ruminant calf will depend on a number of factors including liveweight, health status, energy supply and the target daily liveweight gain. “When formulating diets the term most commonly used to describe protein is ‘crude protein’ – but this is simply a measure of the nitrogen (N) content of animal feed multiplied by a conversion factor of 6.25. Sadly, there is no correlation between the amino acid content of a feed and the crude protein declaration on the label,” she says.
High-quality milk replacers
Caitríona says Volac is always examining how best to ensure its milk replacers meet the crucial balance between energy level, ideal amino acid balance and cost efficiency.
“With the current volatility in dairy markets (dairy protein supply and cost), there is increasing industry-wide interest in replacing a proportion of the dairy protein in milk replacers with vegetable protein. However, when precision formulating diets using non-dairy proteins, both the physical and nutritional attributes of the alternative protein sources must be taken into account,” Caitríona says.