Three important targets to raise the desired number of healthy, fertile, productive heifers:
1. Keeping calf mortality to a low level
2. Maintaining good calf growth
3. Maintaining good calf health
It is highly recommended that performance indicators are used to monitor how well your farm is meeting its targets in order to improve performance. These indicators are called key performance indicators (KPIs). KPIs serve as excellent tools for benchmarking, decision making and following up on the effect of changed practices. Different but overlapping KPIs are used for the three target areas.
Keeping calf mortality to a low level
The proportion of heifer calves lost during rearing often reaches 20%. If calf deaths during calving and the first 24 hours are included this figure is even higher. After a difficult birth the most common causes of death are diarrhea in the first month of life and pneumonia at a later stage. Disparities between herds in terms of reproductive losses are very large, but the good news is that some producers have losses well below 10%.
The urgency of increasing cow longevity in dairy production is often addressed but calf mortality is rarely considered, however, it would be more correct to include these losses in our calculations. Cow longevity begins at birth!
In particular, poor reproductive performance combined with poor calf survival could result in a shortage of new heifers entering the milking herd. Only in herds with very good health do we recommend raising fewer than 35 heifers calving per 100 cows on a yearly basis.
Using KPIs to keep track of calf losses and calculate availability of heifers
· Number of calvings per year or month
· Number of pregnant heifers
· Stillbirth frequency (deaths within 24 hrs)
· Mortality: week 1
· Mortality: month 1
· Mortality: months 2–3
· Mortality: months 4–6
· Culling/Mortality: 6 months to calving
· Keeping a record of causes of death/reasons for culling
Maintaining a good growth rate throughout the rearing period
Growth rate and nutrient intake prior to weaning have been shown to have a significant effect on milk yield, superior to genetic selection for production. Genetic selection yields around 70–120 kg milk per lactation. Pre-weaning calf nutrition and management can yield at least 4 times more milk than genetic selection for the first and second lactation.
In reality, there is wide variation in growth rates between herds and individual animals and there is virtually no advantage in restricting weight gain in any calf or heifer. The scientific evidence of the benefits of maintaining high growth rates for calves with good nutrition is overwhelming.
KPIs for tracking growth rate
It is recommended to measure weight gain during the following periods:
· Birth to weaning
· Weaning to six months
· Weaning to breeding
· Breeding to calving
Maintaining good health throughout the rearing period
Health issues have a detrimental effect on calf growth and later performance of the milking cow. For example, calves treated with antibiotics have been shown to produce around 500 Kg less milk in first lactation compared to non-treated calves.
Here again, health status varies among herds, with the proportion of calves treated with antibiotics ranging from 0 to 100%. In addition, KPIs for calf mortality are also useful for monitoring calf health. Calf mortality not only causes shortages in the availability of new heifers but is also a strong indication of a calf health problem.
KPIs for tracking calf health
· Antibiotic treatment of calves
· Mortality: month 1
· Mortality: months 2–3
· Mortality: months 4–6
· Growth rate from birth to weaning
· Growth rate from weaning to 6 months