If the feed on offer is good quality wet season pasture, that is highly digestible and high in protein, calves weaned as light as 100kg don’t need any supplements. However, very few enterprises wean over the wet season as most are generally calving at that time in northern Australia. Most weaning occurs from the beginning of the dry season.
When weaning occurs with adequate green feed available, the only supplements that may be required are phosphorus, copper, cobalt or selenium. Chemical analysis of grazing pastures will provide a guide to the availability of these minerals.
The main challenge for beef enterprises, particularly in northern Australia, arises when calves are weaned during a period of declining feed quality. Supplementation programs can be designed for weaners of various weight ranges on a low or declining level of nutrition as shown below.
Figure 2: Weaner feeding decisions
*Calves <150 kg require a minimum of 15% crude protein for unrestricted growth
Table 2: Supplement requirements for weaners of various ages and weights on two different pasture qualities
The cost benefits of feeding supplements to weaners depends on supplement prices and the value of the animals. There may be little benefit in supplementing heavy weaners unless their survival is compromised by other events such as sudden cold/wet periods. Other benefits created by good weaning supplementation practices include selling steers earlier and ensuring heifers achieve their critical mating weights at joining. See Figure 3 for an example of achievable weight gains for supplemented and unsupplemented weaners.
Figure 3: Weight gains of supplemented and unsupplemented light (150kg) and heavy (250kg) weaners over 15 months
The feed values of commonly fed supplements in weaner diets can be found in Weaner management in northern beef herds.