Dairy cow performance is routinely assessed using milk recording data, Co-op test results, ICBF fertility reports etc. Do you get a chance tomonitor the performance of your herds next generation, the future of your herd?
Do you get the time to weigh your calves and replacement stock to monitor growth rates?
In practice, heifer rearing receives low priority on Irish dairy farms and achieving target weights unfortunately is neglected by many. Reduced levels of management will result in heifers that may not calve at 24 months of age, be underweight, have lower survival rates to third lactation and reduced milk yields as a consequence of failing to achieve the target weight for age targets.
Adequate growth rates from birth are essential for replacement heifers to reach puberty. Puberty in heifers is more closely related to weight than age. As a result good growth rates are required to get heifers to reach puberty and hit target liveweight milestones during the first two years of life.
Growth rates are influenced by numerous factors including breed, nutrition and health status. As a result they are an excellent measure of youngstock management. From birth to calving heifers need to grow on average by 0.7kg/day to reach a mature bodyweight of 90% at first calving.
From Birth to Weaning
Calves born this spring should have doubled their birthweight by weaning (8 weeks). Weaning management will help to avoid the growth check that can normally occur during the transition from milk to solid feeds. Calves should only be weaned when they are consistently eating between 1-1.5kg of concentrate per day. This ensures that the rumen has developed well enough that calves can receive their energy requirements from other sources once milk is withdrawn.
From Weaning to 9 months of age
After weaning calves ideally should be weighed every 4-6 weeks to track growth. This can be carried out with a weighing scales in the crush when regular jobs such as dosing or vaccination are being carried out to minimise additional labour requirements. Assessment of average daily gain allows for more continuous and regular monitoring of heifer growth. Monitoring of growth rates can be used to identify animals failing to meet targets. Manage heifers that are falling behind before they are more than 10% below target. Research shows that whenheifers deviate off their target growth path by more than 10% it is very difficult to catch them up when relying on grass alone. At Rhyno Mills we have carefully formulated Rhyno Special Calf 19% Nut and Rhyno Supreme Heifer Rearer Nut which has been proven to provide the energy and the protein to help below target heifers to catchup.
The first big target in the heifer’s growth path is to achieve 30% of mature liveweight at 6 months of age. We are looking to focus on lean growth (muscle and skeletal) and not fattening heifers during this period. Lean growth results in an increased frame size while maintaining consistent body condition. Improved skeletal development results in better developed heifers that experience fewer calving difficulties. Rumen capacity can also be limited by age so a high energy, high protein concentrate along with grazed grass is critical to ensure growth rates are maintained (Rhyno Special Calf 19% Nut). We are trying to capitalise on energy efficiency when heifers are young. The heifer’s ability to use feed efficiently declines with age. It is at peak during the milk feeding period. A heifer can double her liveweight in her first three months of life, but typically it takes another nine months before she doubles her weight again. Also the protein concentration requirement of the heifer declines as the heifer gets heavier because the relative weight gain slows down. So feeding higher protein nuts such as Rhyno Special Calf 19% Nut and the Supreme Heifer Rearer 19% from weaning until breeding will help grow and develop your heifers and keep them on target.
Summary Targets
From 9 months to mating. Focus on heifers achieving puberty (45% mature liveweight) one to two months pre-mating and continued growth to mating (60% mature liveweight at 15 months) to improve conception rates.
Mating to 24 months. Weight should be gained over this year targeting 90% of mature liveweight at 24 months. Body condition reflects how well an animal has been fed for the last 6-8 weeks whereas weight relative to liveweight targets is how well the heifer has been fed over her life.
How to work out your herds mature liveweight
Every herd will be different but a good guide for these target weights is to weigh some mature cows in your herd (3rd Lactation or more) and use the average liveweight of these cows as your herds mature liveweight. Use this average mature liveweight to calculate the key target liveweights.
Heifers should weigh the following percentages of their expected mature liveweight at the listed ages:
- 6 months of age – 30%
- 15 months of age – 60% (key target at first mating milestone)
- 24 months of age – 90% (key target for first calving milestone)
Ensuring the best possible development of replacement heifers is critical and, although it needs to be accomplished at low cost, heifer performance must not be compromised. To make sure your calves are on target use Rhyno Special Calf 19% Nut and Rhyno Supreme Heifer Rearer Nut as part of your Heifer rearing programme this summer.