As the future of every dairy herd, replacement heifers need to reach their full potential.
According to Teagasc, the average cost of rearing a replacement heifer is €1,533 per head.
How a replacement heifer is raised has a direct impact on how that animal grows, and future performance of that animal through fertility and future lactations.
By setting targets and regularly monitoring these targets, problems can be identified early, and solutions put into place both to solve and prevent future difficulties and make savings both in costs and in labour.
A typical Holstein Friesian calf is born at or around 38kgs of live body weight.
This calf will be expected to reach 550kgs by 24 months of age, or the age of first calving.
To do this, the calf must grow on average 710g per day over this 24-month period.
This important time can often be neglected with one study revealing that only 2% of UK farmers regularly weigh their replacement heifers.
Weighing of replacement heifers can be done with weighing scales/bridge in a crush.
To reduce costs, these scales can be shared amongst neighbours, but this carries a large biosecurity risk, unless scales are thoroughly washed and disinfected after use.
Weigh-bands (girth tapes) are a more cost-effective option. Measure calves at birth, and again when handled, for example when they are vaccinated, wormed or inseminated.
Young animals are best able to convert feed to live weight gain.
To cost effectively achieve target breeding weights, growth should be maximized during the milk-fed period.
This can be done with access to whole milk volumes of at least 13% of body weight or the equivalent in a high protein milk replacer, early access to concentrates (within the first few days of life, for healthy rumen development) and access to quality housing and husbandry, including colostrum management, vaccination, bedding, water and fibre availability and stocking density etc.
This can all be gone into much further detail in discussion with your vet.
To achieve 24-month old calving, heifers must be in calf by 14-15 months. Fertility increases up to the third cycle after puberty, so puberty must be reached at least 6-9 weeks before the expected first service dates.
Puberty is expected at 40% of mature body weight, breeding should occur at 55-60% of mature body weight, with calving at 85-90% of mature body weight.
In fact, body weight and body condition score are far more important than the heifer’s age for mating.
For example, it is possible to mate Holstein Friesian heifers at 13 months of age, once they have achieved 330kgs and a body condition score of 3.25.
Care at the same time should be taken not to over-condition replacement heifers. As pre-pubertal heifers grow, their mammary or udder tissue grows at a faster rate than the rest of the body.
If the overfed heifer lays down more fat cells than a normal, fitter heifer, this can have a negative life-long impact on the amount of milk producing cells grown in the udder, and on the heifer’s capacity to produce milk.
It is therefore recommended not to exceed growth of greater than 800g per day in heifers of 3-10 months of age.
Delayed puberty, through poor weight gain and growth rates, will delay age of first service and age at first calving, further increasing costs of replacement production.
Over wintered calves fed a typical 70% DMD silage-only diet typically attain growth rates of 300g/day, making concentrate supplementation a requirement to reach targeted growth rates.
Concentrates fed should be high energy, with 15-16% crude protein. Testing of forages can better allow planning ahead to reach targets.
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