Managing heifers for lifetime productivity
The heifers you select for breeding from the current year’s weaned calves will influence future herd productivity.
For this reason, it is important that they are genetically superior for commercially important traits than the dams in the current breeding herd.
A balance between fertility and carcass traits is the goal and this will differ for each production system and target market.
In general, there is an economic benefit in calving heifers at two years of age, as they are likely to have a higher lifetime production than heifers caving at three years of age.
In southern Australian beef production systems heifers are therefore expected to calve for the first time between 22 and 24 months of age and in about 12-month intervals subsequently.
Age of puberty is a heritable trait which has been shown to determine: the ability of a heifer to become pregnant in her first joining season; rebreed and remain in the herd in subsequent years, as well as affect her lifetime production.
It is not surprising then that selection for early age of puberty has been suggested as the simplest method for improving breeding cow longevity and profitability.
For heifers to express their genetic potential, getting in-calf early and rearing a good quality calf every year, one must not forget that adequate nutritional management is essential, as some body condition targets need to be met at crucial times (joining and calving).
In addition, growth must not be hindered by parasite burdens, trace element deficiencies or other diseases, emphasising the importance of best practice health husbandry. Further information on condition scoring methods and targets can be found on: Condition Scoring of Beef Cattle.
Appropriate growth pre and post-joining is also beneficial in preventing birthing difficulties in heifers (steady growth patterns ensuring heifers are not too fat or thin).
Bull choice is also important to avoid difficult births. Estimated Breeding Values (EBVs) can be of great assistance in selecting bulls.
Use of bulls with high Calving Ease Direct and low Birth Weight EBVs are recommended for the heifer breeding herd.
Scrotal size EBVs in bulls is also related to their own fertility and the fertility of his progeny (both male and female), higher EBVs for this trait are favourable.
Comprehensive material on the definition and uses of EBVs can be found on: A basic guide to Breeplan EBVs.
Visual inspection of bull conformation should also be used in the selection process not only to avoid characteristics that may increase birth difficulty events (big head, angular shoulders) but also to ensure long term productivity.
Detailed information on bull visual inspection is provided on: Bull Soundness -Structural.
None of these bull selection procedures will be of much use if the bull has fertility problems or is physically unable to breed.
An annual Veterinary Bull Breeding Soundness Exam will ensure they are fit for the job and avoid unpleasant surprises when it is time to check if the heifers are in-calf. Further information on this type of examination can be found on the Australian Cattle Veterinarians website.
A good understanding of heifer visual conformation and its effect on calving difficulty and longevity is important when selecting replacement heifers. Further information on this subject can be found on: Beef conformation basics.
Combining carcass EBV information and visual inspection are also important to maximise carcass traits, ensuring the herd is well muscled (which will increase profit) but also has adequate fat cover.