Poor fertility in replacement heifers is often due to them being under target weight by mating start date (MSD); however, this can be avoided if the weight and weight gain of replacement heifers is regularly monitored throughout the rearing process.
If the average weight of the mature herd is known, target weights for both calves and in-calf heifers can be calculated based on this.
It is best to weigh all heifers individually, but another option is to weigh a representative group and get an average weight based on this.
So, for example, if the mature body weight of the herd is 580kg; the target weight for calves – at six months – is 174kg, for in-calf heifers it is 405kg and pre-calving they should weigh 522kg.
- Calves (six months) – 30% of mature weight;
- In-calf heifers (approx. 18 months) – 70% of mature weight;
- At calving (24 months) – 90% of mature weight.
If contract rearing, it is essential that these target weights are met by the contract rearer.
In regard to in-calf heifers which are under target weight, but hopefully in-calf, these animals can be run with the main herd or let out with the calves so they have access to the best-quality grass.
Late/weak calves
All farms have late or weak calves that may need that little bit more attention.
In the case of calves being under target weight, either meal or grazing ahead of the older calves in a leader-follower system can be implemented. 1-2kg of meal can be fed to these calves, but meal should not replace good-quality grass.
If calves are on good grass, they will gain 0.8kg/day (100kg in 125 days). The response to feeding meal for calves which are on target is poor.
Calves should also be dung sampled regularly and dosed accordingly. Excessive dosing will only result in a low immunity.