Autumn is a good time to start thinking about which heifers from this year’s spring-born calves are suitable to keep as replacements.

There is no point in waiting until next May to decide which heifers are big enough for breeding or if you need to buy additional heifers because you do not have enough replacements to go to the bull.

The heaviest spring-born calves are most likely born during the first half of your calving period. These calves will be born to the most fertile cows and will make ideal replacements.

The heaviest calves will also be reared by the best milking cows in the herd, again making them suitable replacements.

Traits

Fertility and milk production are the two main traits to select replacement heifers on, rather than colour or breed type.

To successfully calve heifers at 24 months of age and get them back in-calf again, it is important they are well developed by the time they go to the bull next year.

Priority management

The key period in which to get spring-born heifers properly developed for breeding at 15 months of age is during the first winter.

Getting sufficient weight gain from weaning until spring turnout can be a problem. Where possible, replacement heifers should be kept as a separate group to increase their weight gain during the winter housing period.

Liveweight will have a greater influence on getting heifers cycling than age. Heifers need to be a minimum of 60% of mature cow weight when bred at 15 months.

This means that the average cow weighing 700kg needs to be around 420kg liveweight when served at 15 months.

A March-born heifer calf should weigh around 290kg if housed on 1 October.

Typical weight gain over a 180-day winter for a weanling heifer on 70 DMD silage and 2kg of meal will be 70kg to 80kg.

This means heifers are gaining at least 0.5kg/day over winter and allowing for some weight loss for two to three weeks post-housing.

This will bring turnout weight up to 360kg to 370kg, making the 420kg breeding weight a realistic target to achieve next June.

Replacement heifers should also be the first group of cattle to go out to grass next year as early as possible.

Early spring grazing will provide a period of compensatory growth provided that cattle are lean at turnout time.

Read more

Managing the suckler cow around weaning time

Priority management when housing cattle