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Beef Breeder MANUAL
The number of heifers required for mating each year largely depends upon whether the herd is building up
breeder numbers, or only replacing those breeders being culled. Herd build–up includes:
• Increasing total breeder numbers; or •
Undergoing a considerable genetic shift within a stable sized herd. This genetic shift may be changing from
one breed to another, or changing the genetic type within the resident breed e.g. to an earlier maturity
type or superior body structure and growth rate. In each of these situations, a greater number of
replacement heifers will be required each year than when only replacing culled adult breeders in a stable
sized herd. It is envisioned that most of the destination farms
for Australian heifers will be increasing their breeder numbers, so a selection process with this in mind is the
focus. While the process is known as ‘selecting replacement
breeders’, in practice it is often a case of selecting out the heifers not desired as replacement breeders, with
those remaining in the group considered suitable for joining. Identifying those individuals who do not meet
a minimum requirement in terms of their likelihood to become productive and proitable breeders is the
purpose of the selection process. Selection process must consider several aspects:
• Weight • Body condition score
• Body conformation • Health.
In general the older, heavier heifers at weaning have the greatest chance of going on to become fertile,
productive cows. Segregating out the smaller and younger heifers is therefore an important irst stage of
the selection process.
5.7.2. Targets for Heifer Development
For young heifers to become productive members of the herd, they must achieve production targets at
various stages of their early development to ensure that they stay on track through until they reach maturity. Ideal
weight and age targets are presented in the table below Table 5.3. If these targets are not being met at any point
in their growth cycle, the reason should be determined and if practical, changes made to management to
achieve the targets.
Table 5.3. Suggested weight-for-age targets that young British breed female cattle should aim to achieve to optimize their chances of becoming productive breeders.
Stage of Production Age months
Liveweight kg Early weaning optional
3 to 4 100 to 150
Weaning 6
150 to 200 Yearling
12 300 to 320
First mating 14-15
300 to 360 After irst calving
24 380 to 450
Mature adult weight 36
550
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Cold Winter Climates
Heifers begin cycling at around 52 of mature body weight, but ideally heifers should be between 55 and
65 of their mature body weight at irst mating. For cattle with a mature weight of 550kg, the likely expected
size of Australian cattle currently being supplied to cold climate countries, this equates to a target weight of
300kg to 360kg at 14 to 15 months of age if it is intended to calve heifers at two years old.
Heifers below 300kg should not be mated until they gain more weight, as lower conception rates and increased
calving diiculties will likely be experienced by heifers mated at these low weights.
BCS is another strong indicator of breeding potential. Heifers must have suicient body reserves to initiate
oestrus cycling, with optimal conception rates occurring at a body condition score of at least 3.0 at joining. Thin
or lean animals with a body condition score of 2.5 or less, are less likely to conceive within a restricted joining
period.
The fundamentals of desirable body conirmation and structural soundness are common for all types and ages
of cattle, and are therefore relevant to the replacement heifer selection process. Similarly, all heifers selected as
replacements must be in good general health.
5.7.3. Feeding Heifers
