Due to the rumen development issues discussed earlier, management and feeding should be considered relative to age/weight categories. For example, 4 week old calves will have a less developed digestive system than 8 week old calves, and will therefore need to be fed and managed differently.
However, for ease of management, weaners can be grouped as follows:
The number of calves weaned voluntarily at this age in a beef herd is small, however it sometimes becomes necessary, and there may be a few orphans as well.
At this young age, the rumen micro-organisms and digestive enzymes are not developed sufficiently to enable calves to survive on a non-milk diet. Consequently, a milk replacer is required.
It is critical for the long-term health of the calf that it receives sufficient colostrum (and therefore antibodies) from the cow in the first six or so hours of life. Where possible, calves should be left on the cow for several days post-calving. As the calves will have to progress to other feeds, it is advisable to allow them free access to a high energy, high protein, grain-based mix and good quality hay. Intakes of these will be small.
Milk replacer should be fed at about 10% of body weight per day.
From about one week of age, calves need only be fed once per day.
Calves should preferably be fed via a calfeteria set up or bottle fed, rather than bucket feeding. Remember, the teat sucking action is needed to close off the oesophagus to avoid milk getting into the undeveloped rumen, where it will ferment.
Small digestive upsets in pre-ruminant calves regularly cause scours and potentially, dehydration, or longer term effects.
Provide free access to a high energy, very high crude protein (18–21%), grain-based ration.
At this age, intakes will be very low to low, particularly at the start. There is a range of specialist commercial products available. However, where the facilities and feedstuffs are available, a home-made mix, would be suitable.
Free access to cereal hay or good quality forage sorghum is desirable. Preferably not lucerne, as it can be too rich and cause scours.
Intakes of feed other than milk will usually be very low, but access to them allows calves to become accustomed to the feeds and to develop their digestive systems.
Most weaners will weigh between 50–75kg at 4–6 weeks and 85–100kg at 10 weeks.
At this stage, there is generally no need for a milk replacer. A high energy, high crude protein (16-20%), grain-based diet is preferable at this stage.
Suggested diets for weaners 4–5 to 10 weeks old:
Where available, reasonable quality hay is preferred e.g. good forage sorghum or cereal hay (preferably not lucerne). However, because the primary function of the hay is to develop the rumen, a poorer quality roughage e.g. barley straw, could be used provided the weaners are accessing sufficient intakes of grain. As straw will be less palatable, starting with a better quality hay will ensure calves start eating more quickly.
Straight vegetable protein meal can be used instead of a grain ration (often providing a higher level of dietary protein), however it will be less balanced for other nutrients/additives (e.g. minerals, vitamins, Rumensin) and may prove more expensive to feed at the required levels.
On a macro mineral scale, vegetable protein meals are regularly low in calcium or low relative to the phosphorus level. Some vegetable protein meals fed as a major component of the diet may cause digestive upsets and are far better suited as a key ingredient in a ration.
Even though many early weaned calves have been eating whole cottonseed with their mothers prior to weaning, it is not recommended as a core part of the diet for very young weaners. This is because of the potential toxic effects of the gossypol from the whole cottonseed, and reduced intakes/digestive upsets, due to the high oil content.
Molasses based diets are also not preferred for these very young weaners as their digestive systems are typically not well enough developed thus causing scours. However, if other options are not available, or the molasses mix is only a component of the diet, it can be used safely. The biggest challenge is achieving a ration that is sufficiently high in energy and true protein (lower energy and protein = lower expected performance).
Urea, while a cost-effective way to increase protein content of rations, cannot be utilised by very young calves and may be toxic. Therefore, urea should not be used in diets for very young weaners. See the later section on feed mixes for further information.
To ensure normal development and performance later in life, the target weight gain should be as close as possible to what would be achieved on milk in a normal season. This is often around 0.8 to over 1kg per head per day (less in poorer environments). The minimum target weight gain is around 0.5kg per head per day.
The nutritional requirements of weaners weighing 100–150kg are somewhat less stringent in terms of quality, but intakes will obviously increase if fed ad lib.
Suggested diet for weaners 10 weeks to 4–5 months:
Grain-based mixes can be continued for these older calves (1kg per head per day = 3 parts crushed grain : 1 part vegetable protein meal) if it is more convenient or cost effective. At the same levels of feeding, higher growth rates could be expected. The total protein level in a grain mix could be dropped a little compared to a mix suitable for younger weaners, and a low level of urea could be included to provide some of the protein and reduce the ration cost.
Whole cottonseed fed at restricted levels (e.g. 0.5kg per head per day for a 130kg weaner) could also be considered as a part of the diet. Weaners of this age are regularly fed at higher levels, but responses are extremely variable because the high oil content regularly causes digestive upsets. Straight vegetable protein meal is also an option, but again the cost (if fed as the sole source of concentrate feed) may exceed other options.
Typically, weaners in this category are considered ‘normal’ weaners and the level of management required is therefore reduced. However, supplementary feeding is still likely to be required if drought conditions have persisted. Suitable options include molasses mixes, grain mixes, straight protein meal and whole cottonseed. It would be preferable to still target weight gains of around 0.5kg per head per day until the weaners reach at least 200kg.