The winter period presents several challenges for calf rearing and most issues that we see as vets can be traced back to problems with the environment and management. Diseases such as pneumonia and scours are caused in part by a poor environment; and any control measures for these diseases start by ensuring sheds are clean, well ventilated and not overcrowded.
There are a number of different housing systems available for calves, but whichever you choose it is important to consider the important factors that will affect the environment around the calf; ventilation, temperature, humidity and bedding.
In the housed environment, a constant supply of fresh air is essential in preventing respiratory and other diseases together with improving production. Good ventilation removes stale, humid air, which helps ensure that viruses and bacteria cannot survive for long outside the animal. Even in cold weather a good supply of fresh air is essential; but always make sure the airflow is above the level of calves, as animals kept in draughts will not perform because energy will be diverted from growth into simply maintaining their body temperature. Watch out for gaps under doors and gates as they will permit draughts right at the level calves lie at. If calves are housed in an exposed or tall building, consider making lower covered areas where they can keep warm.
As the environmental temperature drops it is not unusual for producers to see reduced growth rates as calves will burn extra energy to keep warm. The body temperature can be affected by environmental factors such as air temperature, radiant temperature, air speed and relative humidity. The lower critical temperature (LCT) is the temperature below which an animal requires additional energy to keep warm. In the first three weeks of life the LCT is between 10 and 15oC, as the calf grows its ability to cope with the cold improves and the LCT drops, calves over 3 weeks of age have a lower critical temperature of around 6oC. During the colder months it is possible to maintain growth rates by increasing the amount of feed the calves are receiving (either by increasing the volume they receive or for those animals on milk replacer increasing the concentration). There is obviously a cost associated with this, but it is recouped by the increased growth rates and also the reduced incidence of disease as well-fed animals have a better immune function.
For young calves, calf jackets are also a very useful tool for providing protection from the cold. Consider using jackets for calves under the age of 3 weeks when temperatures fall below 15oC. The calf must be dry before you put a jacket on to it and it is important to always wash jackets between calves to avoid transmission of diseases such as scour. The common question we get asked is when is best to take the jacket off? I always advise leaving the jacket on until the calf reaches weaning or has outgrown it. When it is time to take the jacket off always do this in the morning when the environmental temperature is going to be its highest, this allows the calf to adjust before the temperature begins to fall overnight.
High levels of humidity allow pathogens to persist in the environment and spread from calf to calf. Good ventilation is important to reducing humidity, but humidity can be further reduced by ensuring good drainage and minimising standing water in the environment. The preparation of milk feeds results in a large amount of liquid in the environment, so where possible preparation and cleaning should occur away from where the calves are housed. Remember adding water to the environment will also reduce the temperature as energy is used to drive evaporation.
It is important to provide enough clean bedding to reduce contact between the calf and soiled straw. Calves like to nest, and it is important they have sufficient straw to keep them warm and minimise stress. Always aim that there is enough fresh straw in the beds so that when a calf is lying down its legs are covered.
The winter period can often present a challenge for youngstock rearing with many farms experiencing increased problems with diseases such as pneumonia and scours. Taking steps to protect calves from the cold and ensuring that they are warm and dry will reduce the risk of disease and also help to maintain the growth rates which are vital for their long-term performance.
Do contact your local Westpoint practice if you would like advice on youngstock housing and management.
Written by Tim Potter BVetMed PhD MRCVS, Senior Clinical Director.