These targets are set to maintain the linear growth achieved during the pre-weaning phase
The target body weight at the end of the postweaning phase is 17% of the mature body weight (MBW). For a Holstein cow with a mature body weight of 650kg this means a weight of 111kg at 3 months of age, achieving an average daily gain (ADG) of approximately 800g per day.
Weaning is an important event as the calf completely transfers from a liquid-milk to a solid-based diet whilst maintaining growth, performance and health. This transition period is stressful for the calf. Its immunity can reduce and its susceptibility to disease increase. So it is crucial that any stress is minimized immediately after weaning (link for tips for smooth weaning). The weaning stage is successful when the rumen has achieved adequate physiological development to support the calf’s nutritional requirements from the fermentation and digestion of solid feed (link to rumen development).
When to wean?
Weaning usually takes place between five and 12 weeks of age and is dependent on the weaning system in place that might, for example, be early weaning at six weeks or traditional weaning at eight weeks. The transition period usually happens over four weeks – two weeks pre-weaning and two weeks post-weaning – but this will be based on the weaning management system.
The decision to wean should be based on solid feed intakes, which reflects the rumen development, rather than on age or live-weight. This will help to maintain high intakes during weaning and prevent growth checks.
The ability of the calf to consume starter feed at weaning is proportional to the volume of liquid feed being offered; when the calf still consumes large amounts of liquid feed, the intake of solid feed is limited. Gradual weaning, where liquid feed is reduced over time in volume and frequency of feeds, will stimulate solid feed intake and is preferred over abrupt weaning. The target for Holstein calves is a minimum of 1.5kg of calf starter feed for at least three consecutive days. This though depends on the individual calf.
Irrespective of the weaning period, the calf should always have access to fresh calf starter, clean water and roughage from the start of the rearing period. This aids early rumen development.
How to wean
Bucket rearing system
Step down the amount of milk and frequency of feeds in the seven to 14 days up to weaning. This should encourage an increase of solid feed intake, improve the efficiency of gain and maximize the economic performance of the calf. (Link to feeding schedule)
Automatic feeders reduce the daily volume of milk on offer over a pre-defined period up to weaning. This results in a gradual weaning process with minimal labor input and results in a smoother transition for the calf.
Irrespective of the rearing system, individual weaning targets should be set and management should support the nutritional and health requirements of the calf. Only healthy calves that are eating and growing strongly should be weaned.Back to top
Good housing conditions contribute to efficient youngstock rearing and ensures their potential growth from the nutrients in the diet is achieved and not wasted by spending energy on staying warm or fighting off high pathogen loads. Poor housing conditions, such as poor ventilation, can lead to poor feed intakes, low growth rates and poor feed efficiencies. It can also have serious long term effects on lifetime lactation.
In general terms there are three simple principles for good housing conditions for each stage of the rearing period
Excess moisture, originating from the animals and bedding, combined with heat is an ideal breeding ground for pathogens. This increases the risk of pneumonia so should be avoided. Excess moisture from leaking gutters, water troughs or broken buckets should also be avoided.
The air around calves should be similar to the outside air. Stale air has a much higher viable airborne pathogen load.
Fresh air is important but draughts are very dangerous. The right air speed will depend on the age and number of animals in the building. The air speed itself, within a barn, is the product of the air inlet and air outlet size and position. A smoke test will help to determine air movement in buildings.
All three principles can be controlled by The Stack Effect
The Stack Effect
The stack effect works by air flowing past the animals, which is warmed up through heat generated by the animals, and rising to the top where it leaves the building through the outlet. As the warm air leaves, negative pressure draws in fresh air from the inlets.
However, this only works if there is enough heat generated by the animals to create the effect. Youngstock create less heat than adult dairy cows and this needs to be taken into account. If, for example, the building is too wide for the number of stock being housed, the cool air can drop instead of leaving through the outlet. A smoke test can help determine whether the stack effect is working.
Appropriate lighting is important, especially during the breeding phase to stimulate the oestrus cycle. For housed animals, 10% of the natural light should be able to reach the pens from clear roofing panels. For artificial lighting conditions, the intensity should be between 100 and 200 lux. Artificial light should resemble natural lighting and follow the daily pattern of natural light.
Housing requirements for calves
Hygiene and pens space regulations
Hygiene is very important, especially in the first months of life when the calf is more susceptible to pathogens. To keep the pathogen load low, regular cleaning of feeding materials is essential.
Young calves lose relatively more heat and have a lower tolerance to cold than older heifers or cows. The temperature at which the calf needs to spend extra energy on keeping warm is referred to as the Lower Critical Temperature (LCT). LCT is dependent on body weight, air speed and moisture level as illustrated in the table below.
If the calf stays warm then energy consumed can be used for growth rather than for staying warm.
Summary of the practical considerations to keep calves warm:
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*Mature Body Weight (MBW) of Holstein heifers is 650kg