BY: Peter Smith
WA Dept of Agriculture- Karratha
Beef Development Officer
Ph: (08) 9144 2065
pcsmith@agric.wa.gov.au

• To improve the lifetime reproductive performance of females.
• Reduce stress on heifers calving for the first time.
• Improve overall breeder herd performance.
• Improve profitability of the business of producing cattle and beef.

It can be difficult to increase the reproductive rate of extensively managed breeder herds. One of the reasons for this is the difficulty associated with recording the performance of individual breeders and culling those that produce less calves.

Employing management practices that influence the performance of the whole herd without complicating the current management system has the potential to improve the efficiency and profitability of the whole business.

The development and adoption of sound weaning and weaner management practices has the potential to improve the performance of many herds. The next opportunity to improve whole herd performance by improving the management of part of the herd is to improve the contribution heifers make.

Heifer management system

There is an opportunity to manage heifers to improve their lifetime productivity and at the same time identify less fertile females. Fertility is not as highly heritable as traits like growth but it is highly repeatable. This means that heifers, which calve early the first time, will continue to calve more regularly during her lifetime.

The aim of a heifer management program then is about identifying these more productive heifers and ensuring they calve at the ‘right time’ the first time. This will help ensure that they establish a regular calving pattern and that overall breeder performance of the herd is improved over time.

Identifying more productive heifers

Research has shown that heifers that continue to gain weight in the dry season immediately following weaning (assuming weaning by June/July in northern Australia) until the season breaks will reach puberty at a younger age and at a lighter weight than heifers that lost weight during the same period of their life.

Supplementation with urea & sulphur and some of the ‘soft’ high intake blocks might be sufficient to ensure improved heifer performance following weaning to achieve earlier puberty in some areas. In poorer seasons and on lighter country, supplements of protein meals, grain based pellets or molasses based supplements might be required or more appropriate to ensure continued growth of heifers following weaning.

Timing the first mating

Once heifers reach puberty they can become pregnant. It is important that the timing of this first pregnancy and calving is planned to occur at the ‘right’ time of the year. The ‘right’ time for calving is usually the topic of some debate. It is suggested that the ‘best bet’ right time should be determined with the help of long term rainfall records.

Early lactation places a very high nutritional drain on heifers that are still trying to grow. It therefore makes sense that calving should be planned to commence just prior to the probability (based on historical records) of receiving useful rain. The ‘best bet’ right time for heifers to calve will obviously vary for different areas of northern Australia.

Mating

Based on experience in other areas of northern Australia it is suggested that heifers are control mated for a period of no more than 3 months for their first mating. This will concentrate calving into the preferred time of the year.

Depending on the environment and the growth rate of heifers following weaning it may be feasible to mate heifers as ‘yearlings’; that is during the first growing season following weaning. In environments where heifers do not reach puberty until they are approaching two years of age, control mating two year old heifers for a period of no more than three months is recommended; once again to ensure heifers calve for the first time at the right time.

Young bulls that have preferably been assessed for breeding soundness should be used for the mating of these heifers. Young bulls are less likely to harbor and spread infertility diseases like Vibriosis and should have superior genetics to older bulls in the herd. Heifers are part of the genetic future of the herd and using genetically superior bulls will marginally hasten genetic improvement in the herd.

Selection for fertility

It is strongly recommended that any heifers that have not reared a calf or have a calf on the ground by the time they are 3 years old be culled from the breeder herd. This practise can be applied in any herd situation. Heifer segregation is not required, only an easily visible age marking system.

Three year old heifers that come through the yards that are well grown and dry should be seriously considered as sale propositions. If they are only going to put their first calf on the ground when they are around four years of age they wont put too many calves on the ground during their lifetime and are best replaced with heifers that have exhibited better breeding potential by putting their first calf on the ground as a three year old.

Unless sufficient heifers conceive as yearlings to satisfy herd replacement needs, little culling on fertility should take place following yearling mating. Culling for soundness, breed type, temperament should take place before any mating.

It is suggested that two year old heifers should be pregnancy tested at a convenient time following mating. Empty heifers should be sold or speyed to ensure sub fertile females don’t find their way into the breeder herd. The timing of pregnancy testing is not critical as heifers can be culled back to the desirable calving period based on their stage of pregnancy.

Managing first calf heifers

It is well accepted that heifers calving for the first time can be serious survival risks, particularly if they calve at the wrong time of the year. Adopting a heifer management system as suggested reduces this risk by ensuring that heifers calve for the first time at the ‘best bet’ right time. In addition, as heifers are segregated as a group they can receive special treatment, supplements etc., without the problem of having to feed the whole herd.

Calves should be weaned from these heifers when the youngest are around 120 kg. These weaners will require some special attention but the heifers will continue to grow and be in better condition to calve as three year olds. From then on they are set for life.

Summary:

• Supplement weaner heifers well following weaning to ensure they reach puberty at a younger and lighter weight.
• Segregate heifers from the main breeder herd and run them as a separate group at least until they wean their first calf.
• Determine, with the help of long term rainfall records, not memory, the probability of receiving useful rainfall or break in the season.
• Select a ‘best bet right time’ for heifers to calve.
• Determine time of mating to ensure calving commences at the ‘best bet right time’.
• Depending on heifer development, control mate as yearlings for no more than 3 months to young bulls that have passed a breeding soundness evaluation.
• Mate as two year olds for no more than 3 months.
• Pregnancy test following mating and select only pregnant heifers that will calve at ‘the best bet’ right time.
• Cull any non lactating or non pregnant two year old heifers from the breeding herd.
• Wean heifers calves at around 120 kg and look after these weaners well – feed and management.

© WA dept of Agriculture December 2002-  This source: http://www.cattlefacts.com.au

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