Successful heifer rearing can contribute to a profitable dairy operation. However, be aware that the opposite is also true! Unless sold off, pre-lactating heifers do not generate any farm income and are often seen as an expense, writes Riaan van der Walt, ruminant technical manager at Meadow Feeds.
The quality of heifers – marked by genetic merit, health status, growth rates, size, etc. – has a pronounced impact on total farm income once these animals enter their first lactation at approximately two years of age.
It is important to acknowledge that rearing a successful heifer starts at birth and not when she is pregnant or close to calving. Health status in young calves is extremely important. Keep in mind that for every clinically ill calf, there may be several affected animals that do not present clinical symptoms.
There is a direct negative correlation between calf morbidity and lifetime production. Calves that experience disease events in the first months of life tend to leave the herd much sooner than their healthy peers.
What is calf morbidity?
Morbidity refers to disease or induced stress events that may impact negatively on an animal’s health and require treatment. Quite often, morbidity results in death which are expressed as % mortality.
The main goal in heifer rearing is to raise the required amount of healthy, high-potential young animals that are well-grown at breeding and achieve the required size and weight when they calve down for the first time. An effective colostrum programme and a hygienic environment are key fundamentals to achieving low morbidity and mortality rates to rear healthy and productive heifers.
There are two main reasons why dairy operations need to rear heifers:
- Maintain or grow the milking herd numbers.
- Ensure genetic progress in the herd.
The importance of maturity and weight at calving
Research literature commonly reports that heifer maturity and target weight plays a big role in a dairy cow’s production lifetime. Heifers reach puberty at around 9-10 months and should achieve approximately 45% of mature body weight at this age. They are ready to breed from 14-15 months at a target weight of 55% of mature body weight. Mature body weight for a herd is considered the average weight of lactating cows in their 3rd or later lactations.
Heifers should be weighed regularly to ensure they achieve a target weight of 85% of mature body weight when they calve down at approximately 24 months of age.
Are maturity and body weight at calving equally important?
It is generally accepted that body weight at calving is more important than maturity.
Although it is costly, it would be better to breed heifers 6-8 weeks later at their target weight instead of calving earlier, but under target. A 95% positive correlation has been reported between 1st lactation milk at 70 days in milk (DIM) and milking herd average. The ideal average daily gain to achieve target weights at breeding and calving depends on the breed but typically ranges from 0.7 – 0.8 kg per day.
For example, the average milk production of a Holstein herd is 10 000L per cow per lactation with a mature weight of 720kg and an average milk production of 5% of live body weight. If heifers calve down at 5% below a target weight, the potential opportunity cost in terms of lost milk production in their first lactation will be as follows:
Target calving weight = 720 x 85% x 5% = 30.6L per day.
Actual calving weight = 720 x 80% x 5% = 28.8L per day.
The smaller heifers are likely to achieve a daily milk production of 1.8L less than the heifers that calved down at target weight.
Heifer-rearing practices have a material impact on the health status and thus, the growth and quality of the heifers that are produced in a dairy operation. It is critically important to ensure that management or environmental conditions do not limit the ability of the future milking herd to express its genetic potential.
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