Posted on 2016-01-07 11:08:00
We mustn’t forget that early weaning the cross bred dairy calf is a challenge created by ourselves. Left to its own devices a calf suckling the cow would naturally wean somewhere between 6 and 9 months old and start eating grass, leaves and weeds. We should also remember that calves would not ‘naturally’ eat grain, but have stomachs built to digest fibrous feeds. By domesticating ruminants and manipulating their diets we have actually taken on responsibility for these vulnerable animals and it’s important we bear this in mind when implementing systems to get the best performance out of calves in our care. We want to make the most of their excellent feed conversion in the milk phase, but convert them to dry feed as soon as feed conversion drops off. In practice this means weaning around 8-12 weeks old.
When you consider the challenges the modern calf meets in the first 12 months of life, it’s hardly surprising that some have digestive upsets from time to time. Frequently the calf is born in a dry cow yard which may have been occupied for several months and has a high bacterial load. Sometimes the calf will fail to suck in the first six hours of life, or take insufficient colostrum. In the first weeks of life the most common reasons for scouring would be ingestion of pathogens such as rotavirus, cryptosporidium, coronavirus, salmonella and enterotoxic E Coli . Providing sufficient good quality colostrum, improving hygiene, and reducing stocking rates will control most of these problems in early life. However, as weaning approaches, there are often concerns around ‘gut health’ as calves tend to scour just before or just after weaning.
There are a number of factors conspiring together to produce this scenario. Firstly, the calf is born with a very weak immune system and depends entirely on its mother for passive transfer of antibodies. As time goes on its own immune system starts to function, but by the time weaning comes around at 6-8 weeks of age the immunity passed on from the dam is waning and the calf itself is still pretty poor at producing its own antibodies. The change of diet from milk to grain at weaning also stresses the calf which is then predisposed to pneumonia and other diseases such as coccidiosis.
With careful management, the weaning process can take place seamlessly, but demands care and attention.
- There are 3 targets for weaning:
- The calf must be a minimum of 6 weeks old and well grown (double birthweight)
- It should be eating 1.5kg/day for 3 consecutive days. (Amounts will vary from day to day)
- It should be cudding.
- To ensure complete conversion from milk to concentrates, there are a number of strategies which will help.
The most important target is to grow the calf quickly, so it is physiologically developed enough to withstand the weaning process. This means doubling (or even tripling) the birthweight, usually by 8 weeks old. Research carried out at Universities of Saskatchewan & Alberta with Trouw Nutrition in 2015 also indicated that calves weaned later have a less permeable gut lining and are less likely to suffer digestive upsets post weaning. Ref.Lifestartscience.com
Trouw research has also compared calves weaned at 6 weeks and 8 weeks old. The studies at the Universities of Guelph and Alberta showed the calves weaned at 8 weeks were 9.8% heavier at 10 weeks old, digested starch more efficiently and showed fewer signs of systemic stress than the 6 week weaners. Ref.Lifestartscience.com
The dry feed should be a mixture of cereals, high quality protein and fibre. The cereals contain starch which is broken down to volatile fatty acids which promote the growth of the rumen papillae. The protein must contain balanced amino acids to promote optimum growth, and the fibre helps to stimulate the wall of the rumen and encourage cudding. High inclusions of cereals with insufficient fibre and too much starch will trigger acidosis, scouring, poor appetite, and poor performance. Choose a specific ‘starter diet’ with a minimum of 18% protein. It’s only for a short time, until 10-12 weeks, but it’s worth the investment to get them off to a good start. Offer ad lib from 3 days old, but allow calves to clean up daily, so fresh food is on offer daily. Discard soiled, mouldy, fausty smelling feed. Also pay attention to the height of the trough and its length. In a group pen allow 0.3 m /calf trough space as bullies will prevent others from feeding at peak times.
Calves are herd animals and perform better in social groups. Grouping before weaning encourages competition for food. Work carried out by Alex Bach has shown that calves grouped together before weaning had better dry feed intakes at weaning than those kept in single pens. Ref IRTA. Bach et al 2010 Calves fed on ad lib milk, restricted milk, or on a computerised feeder should be stepped down slowly over 10-14 days to ease the stress of weaning and allow the important grain digesting bacteria to establish and multiply up in the rumen. Keep the milk mixing rate constant, but reduce the volume of milk day by day, to keep the diet consistent. Water can be offered via the teat to help the weaning process. Once milk is withdrawn the calf depends on the cereal digesting bacteria which will be responsible for producing the volatile fatty acids which the calf needs for energy and growth. An abrupt rapid introduction of grain at this stage could trigger a scour, so must be done gradually. Conversely, introducing too much fibre as once will not cause scour, but it will slow performance.
A source of effective, stemmy fibre is important. This can be long fibre given as straw in racks. Any straw or stalky hay will suffice, so long as it’s clean and free from mould. If straw is chopped, it should be 2-3 cm long and all straw should be provided fresh daily. Sweet, soft hay is not ideal at this stage as the calves will eat large quantities and ignore the concentrates. This is counter-productive, as the calves need the starch in the concentrate in order to develop the rumen papillae. These papillae will be the site where nutrients are absorbed when the calf becomes a ruminant. Soft hay can be introduced once the rumen activity is established, from 3 months onwards.
- Make sure the calf is a minimum of 8 weeks old and has doubled its birthweight (minimum). Offer a good quality, digestible, 18% protein ‘Calf starter’ diet. Keep it fresh.
- Clean Straw (preferably chopped).
- Water (cleaned twice/day).
- House calves in groups prior to weaning.
- Step down milk feeding slowly and monitor dry feed intakes, aiming for 1.5kg/head/day. Provide a source of fibre ideally as chopped straw.