The target for the pre-weaning phase is to wean calves at eight weeks old and at double their birth weight.
The target body weight is 13% of the mature body at weaning. For a Holstein cow with a mature body weight of 650kg, this means a weight of 85kg at weaning, achieving an average daily gain (ADG) of approximately 800g/day. So a 40kg calf at birth should reach 80kg at weaning.
The new-born calf rumen is relatively small and undeveloped. Nutrients from the milk are digested and absorbed by the abomasum and intestines. As the calf starts to eat creep feed this solid food will enter the rumen, the calf will start to ruminate and the rumen will grow.
The primary goal at weaning is to have a developed rumen that can supply sufficient energy to the calf to maintain its growth. However, there are factors that can either stimulate or inhibit the development of the rumen in terms of size and rumination and development of the rumen wall.
The rumen wall development can be stimulated by feeding starch rich components, like concentrates or grains. Feeding only grass or hay will not be adequate to stimulate rumen wall development.
Feeding ad lib concentrate or a muesli in the first 10 weeks is the most effective way to achieve a well-developed rumen wall. Additionally, feeding some roughage as a source of structure is necessary to start rumination and to prevent rumen acidosis. A short (2-3 cm) chopped straw or hay with a low protein level and high NDF content is preferred. Most importantly, the calf has to have access to fresh water.
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Availability of fresh clean water is key in milk-fed calves to stimulate solid feed intake and rumen development to prepare for smooth weaning.
Milk needs to flow into the abomasum and prevented from entering the rumen. Water, however, needs to flow directly into the rumen to stimulate rumen development. This is achieved through feeding water in buckets at ground level. Availability of water will increase early intake of solid feeds and it can also decrease the risk of rumen acidosis in young calves.
It’s generally accepted that water and solid feed intake are highly related and as feed intake increases, water intake will follow similarly. Also water intake will be higher with higher environmental temperatures.
Source: Kertz, 1984Back to top
Feeding roughage, along with concentrate and water, has shown to improve calf health and growth.
This roughage should be chopped and fibrous. As a guide, it should give a scratchy feeling when it is held in hands. The sole purpose of a roughage is to stimulate rumination and the renewal of cells lining the rumen wall, by sketching off old dead cells.
It is often assumed that calf hay should be soft and high in protein. For rumen development, high levels of protein from roughage can actually inhibit rumen wall development. Also, soft hay does not scratch the rumen wall.
Roughage – hay or straw – should also be fresh and tasty. Old or moldy roughages are not likely to be eaten by the calves.
Lack of good quality roughages can result in calves eating straw bedding. Besides a suboptimal rumen development, this can also increase the incidence of diseases, like coccidiosis.
Feeding fresh, chopped and fibrous roughage is one of the key elements of successful rumen development.Back to top
The calf is susceptible to health problems in the pre-weaning phase, up to eight weeks old. Diarrhea is probably the most commonly occurring problem:
Diarrhea is the most common cause of death in young calves. It is almost entirely avoidable with good management. The highest risk period is from birth to one month of age. Avoiding dehydration is vital and it is often the most important factor to ensure calf survival.
The two most important factors in preventing diarrhea are ensuring correct hygiene in the calf and dam environment and good quality colostrum, easily accessible and in the correct quantities. Focusing on these two factors will go a long way to ensuring calf health.
Diseases that occur within five days of birth usually originate in the dam or calving environment whereas after seven days of age problems usually develop from the calf environment. Early identification of sick calves is necessary, so they can be treated.
Frequently occurring types of diarrhea and possible origin.
2. Respiratory infection
After diarrhea, respiratory infection is the biggest health issue affecting calves. It is estimated to cost a minimum of £ 50 (€70) per sick calf, due to lost growth, additional labour, longer rearing period, more feed and milk replacer and treatment cost. Respiratory infection can be caused by viruses like Infectious Bovine Rhinotracheitis (IBR), bacteria such as Pasteurella multocida and/or mycoplasma.
One of the most important steps in the prevention of respiratory infection is to recognize the symptoms. The following are a list of symptoms to look out for:
There are two ways to handle this infection: prevention and treatment.
Prevention is the most important and calls for correct management. Housing and environment of calves is crucial and this includes maintaining an appropriate stocking density (1.5m2 of floor space and 6-10m3 of air space) and having proper ventilation to reduce humidity and remove respiratory pathogens and ammonia.
Bedding must be dry and there needs to be adequate drainage with calf houses cleaned out regularly. And calf groups with different aged calves should not be mixed. Older cattle and calves should not be in the same air space; these animals will carry different infections and have different antibody levels.Back to top
3. Rumen drinking
Another health issue that can occur during the pre-weaning phase is rumen drinking, which can cause diarrhea. Rumen drinking is caused by an incorrect esophageal groove reflex and can be recognized by grey clay-like manure. Rumen drinking can be caused by:
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A calf milk replacer must be safe and nutritious. ProviMilk calf milk replacers are designed with this in mind and to provide an optimal growth curve, before and after weaning. By balancing the amino acids, the calf can get more out of the milk with the same level of protein. All ProviMilk calf milk replacers contain NuStart™ that supports the immunity and health of the young calf.
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 (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 (rumen development).
When to wean?
Weaning usually takes place between 5 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 4 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.
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. Young stock 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