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Mid-winter is a good time to weigh replacement heifers and review performance since animals were housed.
Weighing now will give a good indication of which heifers are likely to meet target breeding weights by May or June.
Along with choosing animals from the most fertile and best milking cows in the herd, meeting a minimum target breeding weight is also important when selecting replacements.
This is particularly important if heifers will calve at 24 months of age.
Heifers that are well developed when they go to the bull are better equipped to cope with gestation and lactation.
Meeting minimum breeding target weights means there is less chance of animals being stunted and an increased chance of getting heifers back in-calf again.
Targets
Heifers should weigh at least 60% of mature cow weight when they go to the bull.
This means heifers should weigh at least 420kg when breeding starts.
Ideally, the heavier these animals weigh, the better.
At 15 to 16 months of age, heifers are 450 to 480 days old, so it is more than feasible to have animals around 420kg to 450kg when breeding starts.
Action
Replacement heifers should be prioritised for an early turnout to grass, just as soon as ground conditions allow.
On a silage diet with 2kg/day of concentrate, heifers are unlikely to be gaining much more than 0.5kg to 0.7kg/day.
Once they return to grass in early spring, weight gains will exceed 1kg/day on good-quality grass during March, April and May.
Therefore, the earlier these animals get to grass, the more likely they are to exceed minimum breeding target weights.
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