This article first appeared in our sister publication, Dairy Farmer.
With millions of calves reared annually, calf rearing makes a significant contribution to the dairy industry.
Calves that are reared as replacements must be well-reared so they achieve good lifetime productivity. Generally, these calves are bred from the best genetics in the herd.
There are several calf-rearing systems farmers can use but, whatever the system, there are some fundamental principles that are the foundation of all successful rearing.
The main aim of any system is to have significant rumen development by 5-8 weeks of age. This will enable calves to be weaned off milk but continue to achieve good daily growth rates of 0.7-1.0kg.
Calving
Cows should be in the best possible condition at calving and be eating a diet that is adequately balanced in nutrition to ensure they produce high-quality colostrum.
Calving cows on dirty feedpads or muddy paddocks should be avoided where possible as newborn calves are susceptible to infections and environmental stress.
Calves have the highest rate of sickness and death of any age group on the farm. It is vital to their survival and wellbeing they are not exposed to the elements or less-than-ideal conditions.
Calves should be removed from the paddock as soon as possible after birth and preferably within 12 hours. Navels should be dipped or sprayed with iodine and if a need has been identified, cord clamps applied. Clamps help to prevent infections from entering and travelling up through the navel, and speed up the drying process.
Housing
Calves should be kept indoors for at least three weeks in facilities that are clean and dry.
Individual pens are ideal but often impractical. A more practical solution is to have pens that can hold 10-15 calves. Pens should be separated by solid dividers to prevent contact between the different groups.
Calves should be housed with similar aged animals for effective group management. They should have adequate space – two to three square metres per calf – as overcrowding can cause stress and increases the risk of illnesses.
Pens should be well ventilated at higher levels but free from any draughts at lower levels. Good ventilation will prevent a build-up of ammonia.
Veterinarians say drainage is essential so calves are not sitting in cold, wet conditions. The base should consist of metal or gravel and be covered with a deep layer of sawdust, wood shavings or bark, which should be topped up or changed regularly.
Another important thing is to have an isolation pen. Any calf that is sick or showing signs of illness should be removed immediately to prevent any diseases from being passed on to other calves. Ideally, these animals should not be returned to their original pen, but remain in the sick pen for the duration of the housing period.
All pens should be cleaned and thoroughly disinfected with Virkon or something similar on a regular basis.
Colostrum and feeding
At birth, calves have no antibodies so it is essential that newborns receive at least two litres of colostrum within the first six hours and a further two litres within 12 hours. This colostrum should be fresh and from the first milking of healthy cows that are milked within 12 hours of calving.
Colostrum provides an important source of specific immunoglobin antibody protection. This helps protect calves against a variety of bugs, and provides non-specific immune factors and nutrients.
An estimated 40% or more of dairy calves have total or partial failure of colostral transfer. This can lead to poor growth, illness and even death. Good quality colostrum, ingested within 12 hours of birth, has long-term positive impacts on growth, health and production.
Tests are available to determine whether a calf has had adequate colostrum, which are especially useful if the calf was born overnight and not removed from its mother for several hours.
A blood sample can be collected from calves aged from 24 hours to seven days to measure the level of colostral transfer.
The feeding of calves can be either ad libitum or restricted.
On milk replacement, calves need to be fed 600-800grams/day of milk powder at 20MJME/kg of milk powder. The mixing strength can be increased to lower feed volume and encourage earlier and more solid feed intake.
On whole milk, calves should be fed 10-12% of their body weight per day. Calves reared outdoors or in cold, wet conditions will require a higher feeding rate. Calf rearers should at least aim to double birth weight by 56 days of age.
Vets say a common mistake is to cut feeding levels in the first two weeks to avoid diarrhoea. In reality, this results in under-nutrition, puts the calf under undue stress and can lead to scouring.
Calf starter pellets or meal can be used immediately and should be 18% protein and contain a coccidiostat. As soon as calves are on pasture, a 16% protein meal is adequate.
Good quality calf rations are formulated to maximise rumen development, and forages such as hay and straw do not stimulate rumen development and may lower pellet and meal intakes – so should be avoided if possible.
Meal should remain a part of their diet until they have a body weight of around 100kg.
Weaning
Target weaning weights differ for jerseys and Friesians but when they are around 65kg and consuming more than 1.5kg of meal or pellets they can be weaned off milk.
Before shifting them out onto pasture, keep them indoors for a few days to identify any calf not eating sufficient meal.
Calves should be weaned onto clean high-quality pasture that is free from parasites. Ideally, it should be around 2000kg/DM/ha.
Paddocks should provide shelter as wind and rain can cause stress and illness in calves. Natural shelter such as trees or hedges is ideal but temporary shelter erected from hay or straw bales can also be effective. Shelter cloths or plastic should be avoided as calves will chew these.
Bobby calves
Farmers across the country are reducing their bobby calf numbers and although bobby calves may not be as important as replacements, they still require the same level of care and attention as they are a source of export income for the dairy industry.
The Animal Welfare Act is recognised throughout the dairy industry and sets out guidelines. Calves must be at least four days old, have worn feet pads, a dry withered navel and be clean and free of disease or injuries.
Importantly, bobby calves must be fed only milk. Any antibiotics found in their system can lead to huge penalties for the farmer. All calves must be tagged and a declaration form for each mob completed prior to pick-up.
