There are many risks associated with calf rearing.
Disease caused by infections, nutrition and calf accommodation can impact growth and limit performance during the first few weeks of life.
Diarrhoea accounts for more deaths during the first month of life than any other disease. Up to 40% of deaths in this age group are due to infection that is picked up either in the calving pen during the first few hours of life or afterwards in the calf house resulting in scour.
There is a huge risk of disease transmission during the first few hours of life therefore prompt removal of the new born calf is vital. In addition, calves that are suffering with diarrhoea can contribute to the spread of infection in the shed. The most common agents causing diarrhoea, rotavirus, coronavirus, Cryptosporidium parvum and E-coli enter the digestive tract through the mouth. They multiply rapidly causing damage to the lining of the tract resulting in loss of body fluids and large volumes of diarrhoea being passed out. As well as this, there is a reduced ability to absorb nutrients from the milk provided so sick calves can become very weak. Due to the multiplication of viruses and bacteria in the digestive tract and large volumes of faeces produced by scouring calves, the shed quickly becomes contaminated. Early isolation of sick calves is an important control measure to limit the spread of infection. Good hygiene procedures are essential to avoid calves from consuming milk that has been contaminated with infectious agents contained within faeces. Buckets and stomach tubes should be thoroughly rinsed and washed with an effective disinfectant after each feed.
Calves are born with no immune protection and rely on colostrum as their only source of antibodies to provide defence against infectious agents. The volume, quality and timing of the first feed are critical to reducing the chances of a calf developing diarrhoea. All calf feeding equipment should be clean and free of dirt or milk from previous use. For calves born to Holstein cross Friesian cows, early intake of at least 10% of birth weight within the first two hours of life is vital. Antibody absorption in the digestive tract decreases rapidly after this time. Hence feeding the calf soon after birth is important. Colostrum quality can deteriorate by 4% every hour after calving due to the switch over to milk production. Milk produced in the udder after calving results in a dilution effect therefore milking the dam soon after calving is necessary to ensure a high concentration of antibodies are collected and fed. It can be useful to measure the quality of colostrum using a densimeter or Brix refractometer. These are simple to use and can be purchased in most agriculture stores. Talk to your vet for a demonstration on how to use either tool. Both devices give an estimate of the density of the colostrum. The greater the density is, the more antibodies are likely to be contained within. Only colostrum of greater than 22% on the brix refractometer or in the green zone using a densimeter should be provided for the first feed. Dam vaccination using Rotavec Corona to boost the concentration of antibodies against E-coli, rotavirus, coronavirus is key to ensuring improved protection. Cows can be given a 2ml dose of Rotavec Corona into the muscle between twelve and three weeks prior to calving. During this time colostrum produced will have an improved concentration of antibodies against the three most common infectious agents causing neonatal diarrhoea. Feeding transition milk or colostrum from vaccinated dams during the first two to three weeks of life will provide local immunity in the guts due to a washing effect. The presence of antibodies in the digestive tract can provide further protection against disease.
The thermoneutral zone is the ideal environmental temperatures range in which calves do not use extra energy trying to either stay warm or cool down. The thermo-neutral zone for calves less than three weeks old is between 15oC to 25oC. Traditional feeding of 8-10% body weight in milk or milk replacer will provide the maintenance requirements for a calf with low growth rates under ideal conditions and no disease challenge. Calves need extra energy in the form of milk if there is a disease challenge due to the demands of the immune system. When the shed temperature drops extra milk needs to be given to compensate for the increase in energy used in trying to stay warm. An extra 1% for every 1oC drop below 15oC and an extra 2% for every 1oC drop below 10oC can be given as an increase in milk fed.
Pre-weaned calves are very sensitive to cold temperatures and draughts therefore a housing assessment can be useful. Deep straw bedding allows calves to create a small nest which they use to stay warm. Straw should cover the legs so they are no longer visible when calves are lying down. Damp bedding absorbs body heat energy, which in turn limits growth during this fed efficient period. Energy lost to damp conditions should to be replaced by providing more feed to ensure growth is not impacted.
Concentrate feeding is vital for rumen development. Poor rumen function post weaning leads to a pot belly appearance due to the inability to utilise the forage diet provided. Eating calf ration as early as possible is necessary to support the fermentation and digestion of solid feed after weaning. A lack of fresh clean water limits the amount of starter ration calves are willing to consume. To encourage optimal concentrate intake a supply of fresh clean water and starter ration within the first few days of life is crucial. A decision to wean should be made when a calf has doubled in birth weight by 56 days and is consuming more than 1kg of dry matter for three consecutive days.
Disease at an early age can limit future performance and longevity within the herd. Avoiding the risks associated with disease requires a holistic approach focusing on breeding for resilience, meeting nutritional requirements, providing suitable housing that promotes growth as well as vaccination to ensure good immune protection against common diseases. Most importantly, healthy animals don’t require treatments, perform better, last longer and have more productive lives within the herd than those that succumb to disease.