Replacement heifers are the future of your herd, but how often do you weigh them to monitor performance? Dairy Specialist at Teagasc, Mark Treacy offers some key tips.

Although much emphasis is placed on choosing the best available genetics to produce quality heifers, how well these animals are reared will have a large influence on whether their true potential is realised or not when they become part of the miking herd.

Underweight heifers will be less likely to go in calf or may end up calving later in the calving season. Even where these animals do go in calf, there are still negative consequences, with underweight heifers being shown to have poorer production and longevity within the herd.

Targets

Heifers should calve down at around two years of age, at 90% of their predicted mature cow weight. Achieving target heifer weights throughout the rearing period is key to achieving this. To calculate predicted mature cow weight, use the maintenance sub-index value of the heifers from your EBI report.  A maintenance value of €0 indicates a mature cow weight of about 640kg, with every €1 increase resulting in a 5kg drop in mature cow weight.

Most farmers are aware of the importance of having heifers at 60% of mature cow weight at breeding. However, it is important that heifer weight is monitored throughout the rearing process to identified issues early when they can still be easily rectified.

Ideally calves should be weighed. Where a weighing scales is not available on farm, they can often be rented in the locality, or a weigh band can be used as an alternative method.

At this stage, most of this year’s replacement heifer calves are just past the first key target weighing date of three months of age and should therefore be at least 20% of mature cow weight.  Preferential treatment should be given to calves which are behind target, with the most practical method being to run as a separate group.

Where heifers are underweight, it is also important to review how they were managed up to now, so similar issues do not occur again next year. The next key target will be to have this year’s heifer calves at 30% of mature cow weight at 6 months of age.

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