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Spring-born weanling heifers that will be retained for breeding next summer should be managed as a separate group over winter.
This allows the group to get priority management and feeding, making heifers more likely to meet target breeding weights next May and June.
In herds where heifers calve down at 24 months of age, the heavier these animals are when they go to the bull, the better.
The more developed heifers are, the greater the chance of animals calving down successfully and going back in-calf.
Targets
Replacements should weigh at least 60% of mature cow weight at the start of the breeding period next May or June. The next target is to weigh 90% of mature cow when they calve down.
In a herd with an average cow weight of 700kg, this means a minimum breeding weight of 420kg. If cows are more typically 750kg, then increase the minimum breeding weight to 450kg.
Weight gain
For a March-born heifer weaned at 1 November and weighing 280kg, this animal needs to gain 140kg by 1 June to meet a breeding target of 420kg.
This equates to an average daily gain of 0.66kg/day over a 212-day period. If the target breeding weight is 450kg, then average daily gain increases to 0.8kg/day.
Diet
Achieving this level of weight gain from a silage diet is difficult, unless feed quality is high. Even then, concentrate feeding will be required.
Feed heifers 70% DMD silage and 2kg/day of concentrate over winter and target the group for an early turnout. Feeding average-quality silage will put heifers under pressure to hit target weight gains.
Having replacement heifers separated for priority feeding makes it easier to target concentrates to maintain weight gain.
Health
Make sure heifers are treated for worms and fluke, as well as regularly covered for lice.
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