Yearling mating lifts income 20%

Making a plan early allows time to set heifers and cows up for successful calving and mating later this year, Rachel Joblin writes.

Mating as a yearling isn’t for everyone. On some farms there isn’t the feed available to guarantee success year-on-year. Where the farm is set up for it, the returns can be significant.

Comparing the same feed profile of yearling mating versus two-year mating on today’s prices, the additional cattle revenue generated can be more than 20%. On a farm with 200 mixed-age cows, this equates to $37,000 which well and truly covers any additional cost (labour, vets, bull, etc).

The intangible benefits also mean mating heifers can have a positive impact on the lifetime performance of the cow herd by greater fertility pressure on the herd. Only heifers that go through puberty early and get in calf early are retained as replacements.

Under the right management, heifers that get in calf early continue to get in calf early as a MA cow and any non-performers are culled early, speeding up genetic gain.

To minimise the risk of failure, liveweight (LW) targets must be set and regularly monitored. There are no silver bullets, LW drives performance. This ensures the heifers will hit puberty and are cycling when they are joined with the bull.

As mature cow weights have shifted over the past 10-20 years, target yearling mating weights have shifted along with them. The consensus now sits at 60% of mature weight for the first mating as a yearling and 85% of mature weight for mating as a two-year-old. For a 550kg cow this equates to a 330kg LW target (300kg min) when she is mated as a yearling and a 470kg target (450kg min) when she is mated as a two-year-old.

For most hill country farms weaning a 180kg heifer calf, this requires 60kg of LWG over the autumn and winter (400g/day), and 90kg of LWG in the spring (1kg/day). This level of performance requires priority feed (allocated crop, grass rotation, rotated with hoggets, etc.)

Getting in calf early

The value of getting in calf in the first or early in the second cycle cannot be overstated. It gives a tight calving spread for ease of management, longer interval to cycle and get back in calf (see post-partum oestrus below), a heavier calf at weaning (more days on earth) and sees the cow stay in the herd longer as she is unlikely to be dry or late.

To manipulate this process, it is common practice to mate as many heifers as possible that meet the grade (weight and type) and then restrict the mating period to 42 days (two cycles). Some farms with good history of performance pull this back to 32 days (1½ cycles). Top-end performance with a two-cycle mating interval would be an in-calf rate of greater than 90% against industry average at 84%.

There are two schools of thought on timing of mating. Some mate their heifers 20 days before their MA cows, others on the same date. There appears to be about a 50:50 split. This division of policy is largely centred on the postpartum oestrus period. This is the time it takes for the heifer or cow to cycle again after calving. Most research suggests the period is 40-60 days for MA cows and 60-80 days for heifers.

When conditions are below optimum (restricted intake, low BCS), this period can be stretched out by up to 60 days. This postpartum oestrus period becomes a crucial number when added to the 280-day calf gestation length.

• 70 days postpartum oestrus + 280 days gestation = 350 days (inside the 365-day breeding cycle)
• 100 days postpartum oestrus + 280 days gestation = 380 days (outside the 365-day breeding cycle).

If a cow’s postpartum oestrus is extended to 100+ days for successive calvings, the cow becomes a late, then a dry-dry and her time is over.

To get around the heifer’s longer postpartum oestrus, some farmers adopt the strategy of mating their yearling heifers 20 days earlier than the MA to ensure there is enough time for the 2-year-old heifer to cycle in line with their MA bull date.

The contrary view is to mate the yearling heifers on the same date as the MA cows and take the view that for every day later a cow is calved, the postpartum oestrus is also reduced by one day (she cycles sooner). This is put down to an increase in pasture quality and quality, longer day length and higher air temperatures.

Feeding at key times

From a weaner to mating as a yearling, the heifer needs priority treatment. Regular weighing needs to occur along the way to track progress. Steady and consistent LWG over winter is recommended to ensure the heifer is not compromised early in her life. With specific management areas set up in the spring, yearling heifers can easily achieve growth rates north of 1kg/day.

Through mating, the heifer needs to stay on this rising plane of nutrition. Post-mating, the aim should be to keep the heifer growing at 0.5kg/day until early winter. This is the most effective way to minimise calving difficulties, as the bigger the heifer, the more in proportion she is to her calf. Restricting the heifer during early stages of pregnancy is unlikely to impact the birthweight of the calf.

Ensuring this weight is on early also gives a greater chance of the heifer meeting her two-year-old mating weight target the following year. In the last 50 days before calving, the aim should be for the heifer to maintain her condition. Any LWG noticed is the calf growing inside her. It is recommended not to overfeed during this time as excess fat around the birth canal can make calving difficult. The most common strategy is to keep heifers fit on the hills before being brought down to calving blocks.

Nutrition in the three weeks leading up to calving has significant bearing on the postpartum oestrus period. It is important heifers (and MA cows) do not lose any condition during this time.

Post-calving, the system needs to be set up to ensure the heifer’s feed intake is unrestricted. During this time, she is under a massive amount of pressure as she is lactating, gaining LW, and going through the physiological change of starting to cycle again.

Underfeeding at this stage results in the greatest re-breeding failure rates. For this reason, it is crucial that the calving date lines up with the creation of a surplus of feed in the farm system. If this cannot be guaranteed, the calving date needs to be revisited.

Develop a plan with your vet for animal health.

From weaning onward, common practice is to drench weaner heifers every six weeks through to early winter. One drench is given in the early spring as a yearling and then depending on performance/ assessment they can be drenched again in the summer and/or autumn.

Most cattle will require a lice pour-on coming out of winter.

Trace elements need to be monitored. Copper is used strategically on most properties and administered either in a bolus or injection form. An effective Lepto and BVD vaccination policy is required to protect the herd (and yourself).

Yard weaning or intensive management and human contact early in the heifer’s life will ensure the itstay calmer during calving beat. Calve close to yards and monitor regularly so assistance can be offered quickly. Be prepared to assist with 5% of the line.

The recommended bull ratio is 40:1 for two-year-old or experienced bulls. This number can drop to 25:1 if using yearling bulls. Choose a bull specifically bred for calving ease as any growth rate penalties will be offset by a reduction in calving difficulties. Other EBVs to consider include days to calving, scrotal size and milk. Talk to your breeder about matching bulls to your heifer mating programme.

Planning and managing heifers for successful mating starts now. Getting the feeding, LW gains and animal health right through winter and spring will produce a heifer that is more likely to be a high performer for her lifetime.

• Rachel Joblin is a BakerAg consultant.