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Successful calf-rearing depends on the integration of nutrition, environment and health management skills. The time from birth to weaning represents the most critical phase for the young calf. The success of this first rearing phase depends on farmers paying special attention to detail. Among the most important is establishing a sound calf-nutrition programme.
Milk replacer (MR)
When selecting a MR, the decision should be based on targeted growth requirement of the calf and the farming operation (dairy versus beef). Once a powder is selected, the amount offered will depend on the calf body weight, desired growth rate and nutritional composition.
Where it is practical, two different MRs could be used on the farm at the same time. In this instance, a very high specification, digestible powder (high-quality skim or whey proteins; minimal plant proteins) could be used in animals that are less than two weeks old and have a limited ability to digest non-milk protein, and a more economical powder in older calves where the digestive system is better developed to cope with cheaper ingredients.
Typically, it should be easily possible to feed MR at a 125g/litre concentration and many units feed at 150g/litre concentrations. Under most circumstances the recommendation is that a standard MR is offered at a feeding rate of six litres (125g/l), equating to 750g of powder per day. Such an intake will sustain a targeted growth rate of 700g per day up to weaning, or 100kg live weight at 12 weeks for Friesian bull calves. However, a significant number of farms fail to feed sufficient quantity of powder to meet the basic nutritional requirement of calves.
There is growing evidence from the US that high growth rates in early life promotes both better health in calves and productivity in their adult life. It is suggested that accelerated growth rates of 900g to 1,000g calf/day could be achieved from birth to weaning for high genetic merit dairy heifers. However, in order to achieve this high growth rate in the first two months of life, a daily MR allowance of 1,250-1,500g/day with a crude protein content of 26-28% is required. When investigating this, Irish data showed there was there was no growth or intake response to increasing the crude protein content of the MR from 23% to 28%.
Feeding a high (1,200g/day) compared to a low level (600-700g/day) MR diet for the first 56 days had no effect on carcase weight or carcase characteristics for steers slaughtered at 24 months. Also, no productivity benefit in either milk yield or milk solids were found for the heifer calves offered these high MR allowances. Excessive MR intake will also suppress concentrate intake, thereby delaying weaning.
Once-a-day feeding (for two- to three-week-old calves)
Calves are fed once per day and typically receive 2.5-4 litres per feed (depending on liveweight/size of the calf), at higher concentrations of 170g/l to 200g/l. If feeding once a day, rigorously stick to 24-hour feeding intervals. Calves should be fed at the same time each day and preferably early in the day.
The introduction of a once-a-day milk-feeding system does not affect calf performance or health but will reduce labour requirements. This will give the farmer extra time to identify health issues such as scour or pneumonia early. Importantly, for a once-a-day system, farmers should not compromise on calf health inspection and calves should be checked at least twice per day for signs of ill health
Digestion
Calf-rearing is a high-cost phase and farmers should aim to get the calf off milk and onto solid feed as early in life as possible. This means developing the rumen and in turn changing the calf from a pre-ruminant (depending on liquid diets) to being a ruminant animal which can digest concentrates and roughage. Consumption of starch-based concentrates drives rumen development. Once the calf eats concentrates, the rumen begins to supply nutrients produced by fermentation and a population of rumen bacteria begins to grow.
Fermentation of the starch component of grain produces volatile fatty acids (VFA), particularly butyrate, which stimulates growth of rumen papillae, essential for the absorption of nutrient in the rumen. After about three weeks of eating concentrates, the calf’s rumen will have enough bacteria fermenting enough feed to supply a substantial amount of energy. From a management viewpoint, rumen development can be assisted by providing free-choice water and a high-quality concentrate in the first few days after birth.
The earlier starch is digested by the calf, the faster rumen development occurs. It takes about 21 days to develop the rumen papillae from the initial time that concentrate is fed. Therefore, nutritional management plays a crucial role in determining rumen development and, in turn, weaning age.
Concentrate intake
Ideally, concentrate and water should be offered to calves within three to four days of birth. Calves should be eating some starter by five to seven days of age. Calf starter should be high-quality and coarse in nature to provide the best texture for calves. Avoid finely ground, dusty feeds. Dusty diets may lead to increased incidence of respiratory disease. A good concentrate should contain 17-18% crude protein, the necessary mineral and vitamin supplements and have an energy value of at least 12 MJ/kg feed DM. Always try to encourage starter intake. Keep the calf starter as fresh as possible and only feed small quantities. Clean out mouldy or spoiled feed and replace with fresh feed daily. Ensure feed buckets and troughs are the correct height to enable easy access for the calves.
Feeding roughage
Calves in general do not need roughage (hay or straw) during the pre-weaning period (less than eight weeks old). Roughage such as hay is not required until a time when the calves are consuming about 2kg to 2.5kg of concentrate, which typically doesn’t occur until after weaning.
A general recommendation would be to offer hay starting at week eight and monitor starter intake to ensure that hay is not being overeaten. Including too much roughage would lower the energy content of diets and would not therefore be beneficial.
When a calf has unrestricted access to large amounts of roughage, rumen capacity increases. However, excess roughage intake results in a pot belly condition. To limit this, research from Teagasc recommends a concentrate to roughage (hay) ratio by weight of eight to one is satisfactory. Long forage is beneficial to promote the growth of the rumen muscular layer and maintain the health of rumen epithelium. However, its role in early rumen development scratch-concept is unfounded.
Weaning Calves
Depending on the feeding strategy, calf weaning age can vary from five to 10 weeks. However, age is not the main criteria for weaning. Weaning decisions should be based on the calf’s solid feed intake. Once a calf is consuming 1.3% to 1.5% of its body weight as dry feed, this will provide sufficient nutrients to maintain its weight and grow without liquid feed. For Friesian dairy calves, this equates to weaning when the calf consumes 1kg of calf starter per day for three consecutive days. To stimulate concentrate intake, the general advice is to reduce liquid feed consumption by 50% per day one week prior to desired weaning date. Indeed, once the calf is eating starter and the rumen is developed sufficiently, there is limited evidence to indicate any difference between abrupt weaning and gradual reduction in milk intake.
As previously mentioned, measuring the starter intake is a crucial component to a successful weaning strategy. By monitoring starter intake, farmers can adjust weaning dates for calves that fall behind due to an illness, and wean only those that are healthy and eating well.
Given the cost and labour associated with calf-rearing, numerous studies in the US have looked at early weaning options. The general conclusion is that there were no differences between calves weaned at four to six weeks versus eight weeks of age, provided excellent management practices were in place on farms. However, calves must be a minimum of four weeks old before you consider weaning. Calves can be ready for weaning by four to six weeks of age, but it is critical to acknowledge that early weaning cannot succeed without early rumen development. If the rumen is not prepared and functional, the calf will suffer a growth check for up to three weeks after weaning.
Importantly, if the rumen is not adequately developed, this post-weaning growth slump will occur at any age or calf weight. Rumen development takes about three weeks to occur, so successful early weaning will require that grain and water be consumed within the first week of life.
Weaning imposes significant stress on calves due to changes in their diets, housing and environments. Simple management practices can reduce stress. Give calves time to adjust to weaning – wait at least a week after weaning before you move calves to a new house. If group housing, keep the group small and try to keep the ration the same as before weaning for first two to three weeks. Also, avoid management stressors, such as dehorning and vaccination, around the time of weaning.
SHARING OPTIONS: