Managing replacement heifers is a key part to the farming enterprise as they are the future to maintaining or growing the herd. However, rearing replacement heifers represents a significant cost, with the average cost of rearing a heifer until calving around £1800.
If we take an example of a 100-cow herd with a 25% replacement rate, this equates to a rearing cost of around £45,000 per year. Rather than the cost associated with heifer rearing, think about this stage as an investment that can deliver better returns, as it is known that faster growing heifers get pregnant sooner, produce more milk, lower replacement costs and a greater lifetime productivity.
Therefore, good heifer growth rates will increase profitability, especially as it is heifer bodyweight (and not age), that drives the onset of puberty and allows for earlier breeding. However, how do we know if heifers are growing well? To do this we need to set some target weights to monitor using scales or weigh bands.
As cow size and bodyweight vary between breeds and herds, target weights are expressed as a proportion of the mature herd bodyweight (this is the average bodyweight at calving for cows in their third lactation onwards). Table 1 shows the target weights and an example using 650kg mature bodyweight.
Using Table 1:
l If a 60 day old calf is weaned at 80 kg
l The target weight at service is 358 kg
l The target growth from weaning to service is 278 kg (358kg – 80kg) over 360 days
l This is an average of 0.77 kg per day.
To achieve a growth rate of almost 0.8 kg per day requires a combination of good nutrition and health.
The stage between weaning and puberty is critical, as during this time nutrition affects frame development and exploiting this results in taller, more resilient cows.
The aim is lean body growth that takes advantage of the high growth efficiency at this time. As rumen capacity may be limiting at this age, high energy and protein diets are needed, of which well-managed pastures can provide. However, monitoring bodyweight is important, as pasture supply does not always meet feed demands. If heifers are under target, feeding good quality, high energy and protein concentrates can improve growth rates and supply essential mineral and vitamin requirements.
Weaned calves can be vulnerable to coccidiosis and worms, often seen as loose faeces and reduced growth rates. Rotating the young stock grazing and maintaining good drinker and feeder hygiene can help keep parasite burdens low. With worms, many farmers treat heifers within a month of turnout to keep pasture burdens low. Target the heifers at risk and ensure they receive the correct dose for their weight.
Rotating the treatment will help prevent resistance build up. Another option is take faeces samples to your veterinary surgeon or veterinary lab for parasite monitoring, which allows for strategic and targeted treatments. Where incidences of blackleg have occurred on farm, clostridial vaccination is essential, which requires two injections given four weeks apart before the risk period.
Good health and nutrition helps heifers meet growth and age targets, resulting in successful and cost effective heifer rearing and high levels of lifetime performance. Your nutritionist can help you set growth targets and your veterinary surgeon can help you with vaccination and parasite control advice.