Managing cow reproduction: an overview
To consistently achieve a high level of cow reproductive efficiency, management is required that results in:
- a high proportion of cows becoming pregnant early in the optimum conception period,
- pregnancy testing to remove non-pregnant cows or cows that conceive late, and
- ensuring high cow and calf survival through to weaning, during which time pregnancies for the next calf crop are established.
The following are some of the key elements of management required to consistently achieve high reproductive efficiency. Each of these elements is discussed in more detail in other documents.
Managing cow condition
Managing cow condition is a key component in improving reproductive rates. Poor nutrition is often the leading cause of sub-fertility in breeding herds in northern Australia. During the dry season a lactating cow’s nutrient requirements usually exceeds what she is able to consume from the pasture. As a result cows lose body condition, and then have difficulty conceiving following calving.
A cow should be in condition score 3 or above (on a 1–5 scale) at calving if she is to get back into calf again within the 85-day window to produce a calf each year (i.e. within a 12-month time frame). Body condition of the cow at the time of calving determines how soon a cow starts cycling and conceives post-calving (see Body condition scoring).
For most businesses, the key strategies in maintaining cow body condition during both wet and dry seasons are:
- Cattle control (to improve management capacity)
- Pasture management: appropriate pasture utilisation (feed available)
- Weaning management (to remove stress of lactation)
- Mating management (to reduce dry season lactations)
- Strategic supplementation (to correct nutritional deficiencies).
Cattle control is primarily a function of fencing and the capacity to muster and handle cattle as required. Where basic management is not satisfactory, higher-order management such as seasonal mating becomes proportionately more difficult and less efficient.
Pasture management (feed available)
Appropriate pasture utilisation and adequate distribution of good-quality water points is fundamental in managing cow body condition and achieving consistently high reproductive efficiency. For more information see Grazing land management.
Weaning is critical in managing the period of time a cow lactates. A lactating cow requires considerably more energy and protein than a dry cow (see Nutrient requirements of beef cattle). Weaning removes the stress of lactation which in turn lowers a cow’s nutritional requirements and reduces body condition loss. A vast amount of research has shown that lactation also suppresses cycling. A cows’ chances of cycling are improved simply because the suckling calf is removed.
Managers must time weaning to achieve the best compromise between weaner growth and loss of cow condition. Astute managers start weaning before cows start to slip, and time weaning rounds to minimise the degree of condition loss in lactating cows. Special supplements are needed for young weaners to meet their nutritional requirements for their growth. For more information see Weaner supplements.
Despite well-established folk-lore, research also shows that temporary weaning for 48-72 hours by itself has little or no significant fertility benefit.
If infrastructure development allows, seasonal mating will markedly assist lactation period management and overall business efficiency. The key objective of seasonal mating is to reduce the period of lactation in the dry season. This will preserve body condition, support healthy egg development and ovarian function for cycling, and improve herd reproductive performance. Mating should be timed to restrict or eliminate dry season lactations. For more information see Seasonal mating.
Dry season supplements should only be used to enhance effective management, not as a primary management tool to manage nutrition. Under poor pasture conditions in the dry season when crude protein (CP) levels maybe as low as 5%, the pasture diet does not supply enough protein to meet the needs of an average size lactating cow. At 5% CP this dietary deficit in protein may be in the order of 480g. A 30% urea supplement will only supply 172g of protein if 200g per day is eaten. So for lactating cows it is difficult to correct this dry season protein deficit with a urea dry lick. For a dry cow it is easier to correct the dry season deficit in dietary protein, due to the lower nutritional requirements of a dry cow. For more information see Nutritional management of breeders.
Holding condition on pregnant and lactating cows keeps the ovaries in a ready state to cycle. If cows are allowed to lose condition it is generally too expensive to recover enough condition to warrant any increases in pregnancies during lactation. One exception is Spike feeding where an energy concentrate is fed to cows during late pregnancy for 50 days before calving during a period when cows would otherwise have been losing condition. This strategy is most economical when applied to maiden heifers seasonally mated, and where energy supplements can be accessed effectively.
Wet season supplements are necessary to correct major mineral deficiencies, which can impact significantly on feed intake, growth rates and fertility. The key mineral deficiency in northern Australia is phosphorus. For more information see Phosphorus supplementation.
Nutritional supplements can help to rectify management errors, but in most cases, supplement efficiency is much greater when based on good management.
A good heifer management program is essential to improve reproductive performance in the breeding herd. In heifers, age and weight at puberty is highly variable. Generally, if well-managed heifers reach 350kg by the end of their first mating, the probability of pregnancy is high. Heifers may require supplementation in some years or a special paddock after weaning so they achieve these weights.
As heifers are still generally growing themselves when they have their first calf, they should be seasonally mated so that they calve at the right time of the year. Nutritional stress is significant during their first lactation. A heifer that calves at the ‘right’ time for her first calf is much easier to manage than one that calves out of season. For more information see Heifer management.
Pregnancy diagnosis is a valuable tool for beef producers and impacts on short term profitability through sales decisions. Pregnancy testing or foetal aging results will give an indication as to the conception rate in seasonally mated herds, as well as the calving pattern and spread. This allows producers to make decisions about which cows to cull (e.g. dry empty, late pregnant) and which to identify or segregate. In turn, it assists with decisions about keeping more pregnant replacement heifers or purchasing heifers or pregnant cows. In herds where mating is uncontrolled pregnancy testing also enables producers to identify and separate high risk cows due to calve in the late dry season. For more information see Pregnancy testing – utilising results.
The primary infectious diseases that affect reproductive efficiency in north Australia are botulism, vibriosis and pestivirus. Leptospirosis and trichomoniasis are a problem in some situations. Botulism and vibriosis vaccination are recommended in most areas. Diagnosis and financially-viable control measures for all diseases should be on advice from your local cattle vet: e.g. vibriosis vaccination is recommended universally in bulls, but only strategic use in female cattle.
Part of the cost of producing each weaner is the cost of having bulls. North Australian research shows that no more than one bull per 40 cows is required (2.5% bulls). Lower bull percentages enable use of higher-value bulls, but with the proviso that bulls are not sub-fertile or infertile.
All bulls should pass a Bull Breeding Soundness Examination (BBSE) before their initial mating. Bulls passing a full assessment and those that do not suffer injury, disease or mismanagement, generally remain fertile for many years. However, all bulls should have an annual check-up before mating, particularly for single sire herds and where lower bull percentages are used.
Stress, whether it is caused by poor nutrition, relocation, mismanagement of bull groups, or being non-adapted, all cause sub-fertility. Fertility, and particularly semen quality, can be substantially suppressed for two months or more until relief from the stress is achieved.
Good managers minimise stress in bulls, particularly in the two months pre-mating and during mating. Some strategies to achieve this include:
- purchase and relocate new bulls well in advance of mating and acclimatise them carefully
- keep bulls in forward condition
- never use in excess of 4% bulls
- cull bulls before they reach 10 years of age.
- Aim for cow condition to be score 3+ at calving
- Maintain adequate pasture resources
- Minimise or eliminate dry season lactation (weaning and mating management)
- Strategic use of supplements
- Appropriate disease management
- Bull management (condition and soundness)
There are many more complexities than discussed in this broad overview and specific advice should be sought from your cattle vet or beef advisor.
Geoffry Fordyce, Queensland Alliance for Agriculture and Food Innovation, and Felicity Hamlyn-Hill, formerly Queensland Government.