Should we calve beef heifers at 24-months?
THE question of whether we should calve our suckler beef heifers at 24-months-of-age is always open for good debate.
Depending on whether you operate a spring or an autumn calving system on your farm, the question of what weanling heifers you will be keeping as replacements, and what age you will be breeding them at, is going to come up from now on.
At the moment, in a spring calving system, we are at a stage when weaning and selling will be starting; and if operating an autumn calving system, introducing the bull or using AI will be getting near.
Therefore it might be an idea to start thinking about what heifers in the herd are most suitable for keeping as replacements based on their physical performance; performances of their dam and sire; and their projected suitability as replacements based on our EBI system.
Currently, the national average age of suckler replacement heifers calving for the first time is 31- to 32-months-old. Nationally there is a target for first calving of 24 months. Additionally, only 24 per cent of the national suckler herd is calving at 24 to 26-months-of-age.
If we are to calve our replacements at 24- to 26-months-of-age, it means we will be breeding them at 15- to 17-months old.
But is this achievable on your farm?
Studies carried out have shown that heifers that calved at 23 to 26 months had as good a calving interval – and calved down as soon again – as a second calver as heifers calving down in the older categories.
The study figures also show that younger heifers do have slightly higher calf-mortality, but we can argue that heifers, irrespective of age, will be more difficult to calve and, as the study showed, will need some assistance at calving.
Heifers that calved for the first time at 23 to 26 months had greater survivability in herds, with almost 40 per cent reaching fifth parity, compared with only four per cent of those that calved for the first time at 31 to 35 months.
Some tips that could be used to increase the number of heifers calved from 24- to 26-months-of-age could include:
Identifying your replacements early: Monitor all of your potential replacements as calves. By weaning-time, you should have identified the best-performing heifers from your best cows, and those that have been sired by bulls and have good maternal traits.
Feed appropriately over the first winter: Heifers should be 280kg to 320kg at weaning, which means that you will need them gaining a minimum of 60kg to 80kg over their first winter if you want them to reach the appropriate target bulling weight at 15 months.
Depending on your silage quality, this means that you will need 1kg to 3kg of a good-quality weanling ration per head per day over the winter to achieve 0.6kg gain per day.
Mature weight at bulling: If your mature cow weight is 700kg, you will need your heifers to be around 420kg at bulling.
Much lighter than this may mean some of the heifers are not cycling at the start of breeding, as puberty in heifers is more related to weight than age.
Calving ease of sire used: This is a critical point irrespective of what breed you choose to use on your heifers.
Selecting an AI or a stock bull with proven calving ease is crucial.
The target is to get these young heifers calved easily and give them every chance to go back in calve again as first-calvers.
Pre- and post-calving care: Once successfully bred, heifers need to be well-managed to achieve 80 per cent of their mature weight by the time of calving.
So if they average at least 0.6kg per day throughout pregnancy, they should easily achieve this target.
Even for their first lactation, heifers should be given priority care in terms of grass and feed in order to remain within the herd long-term ,as these heifers will be some of the highest genetic merit animals in the herd.
From a management viewpoint, calving heifers at 24 months means less groups of animals on the farm and higher output, which will ultimately mean greater sustainability.