Maximising fertility in tough seasons

15 April 2016

Producers have been warned that Southern Australia’s extended dry spell has placed serious pressure on cattle reproductive performance.

However, according to cattle consultant Rod Manning, who will be speaking at next Wednesday’s MLA More Beef from Pasture ReproActive Workshop at Mansfield, there are strategies producers can use in  tough times to maximise  heifer and cow pregnancies within controlled mating periods.

“Nutrition is a major driver of fertility which is important in southern systems where we expect to join heifers at 15 months and calve them down at two years,” he said.

“If nutritional demands are not met, body weight and reproductive capacity are sacrificed first.

“Females need energy to switch on their reproductive cycle, or in the case of heifers, reach critical mating weights to stimulate puberty and cycle.

Feed now to reach critical mating weights

Critical mating weight is the weight at which 85% of a herd is pregnant within two cycles.

“If you think your weaner heifers will struggle to make that 300-320kg target at 15 months, plan early to increase their energy intake,” Rod said.

“Failing to do this will affect growth, particularly pelvic development, delay puberty, increase the risk of dystocia and lead to fewer pregnancies within that six-week joining period.”

Interestingly, Rod said genetic selection  has contributed to increased the critical mating weights of maiden heifers during the past decade as more focus has been placed on higher growth rates in young cattle

“It used to be 260-280kg, now with larger cattle, it’s more like 300- 320kg,” he said.

“We really want them at 320kg at joining so they are about 440kg at the point of calving.”

Look after the young ones

Lactating first calf heifers,  which according to Rod have the highest energy requirements of any stock class, are the animals most at risk in tough times.

“They have to have enough nutrition post calving and adequate body condition to ensure that they return to oestrus quickly enough to get back in calf,” he said.

“They require energy for maintenance, growth, lactation and reproduction and once body condition score falls below three, it’s a slippery slope,” he said.

Rod said the ability to accurately body condition score, which will be demonstrated during a practical yard session at the workshop, is critical to running a successful beef breeding business.

“Body condition score three is the sweet spot we should all be aiming for,” he said.

Save a cow’s fertility, wean early

According to Rod, when to wean is a function of cow condition. Once a cow begins to slip in condition, below body score 3, a weaning date should be set.

“Running a cow-calf unit when the season is tough and feed is scarce is the most inefficient use of the pasture available,” he said.

“By weaning calves at four-and-half  to five  months, a cow’s energy requirements are halved, she can be treated as a dry unit and calves given priority for feed.

“In severe dry conditions, calves can be weaned at a minimum of 100-120 days old and about 120kg but you need to be very good nutritional manager to attempt this.

“The calves will require high quality feed, about 10.5 to 11 of metabolisable energy in the form of pellets or grain and very good silage or lucerne.”

Joining periods – stick to your guns

Rod said maiden heifers should be joined for six weeks and cows for six to eight weeks – regardless of seasonal conditions.

“Don’t be tempted to leave bulls in for longer,” he said.

“If they join later, you never get them back and this leads to uneven calf drops, lower average weaning weights and less replacement heifers making their critical mating weights.”

The Mansfield ReproActive Workshop will also feature cattle veterinarian Anna Manning, of Delatite Veterinary Services, who will talk about joining periods, bull management and health and reproductive disease management.

The workshop:

When: Wednesday, April 20
Time: 8.30am – 1.30pm
Where: ‘Davilak’, 22 Tin Hut Lane, Mansfield, Vic
Cost: $35 includes ReproActive materials, refreshment and lunch
RSVP: Register online at for information and directions.

For more information:

 Anna Manning T: 0400 369 177 E:


For more information on improving reproductive efficiency visit the More Beef from Pastures module

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