18 May 2012

4 minute read

The Smiths use the information to refine herd management strategies that boost heifer conceptions, calves weaned and re-conceptions the following year. Their research contributed to the best management practices in the MLA publication Heifer Management in Northern Beef Herds.

The Smiths run a self-replacing, continuously mated Angus herd, and finish steers on native pastures to 600kg liveweight for the Jap Ox market.

Pasture production occurs on many soil types, in a region characterised by highly variable, summerdominant rainfall that averages only 200mm/year.

During the 2004—09 drought, the average dropped to 143mm, and only 98mm was recorded in 2008. To manage risk, the Smiths have focused on breeding hardy, highly fertile Angus cattle that have a strong growth response to even minimal rain.

At the end of every year, digestibility of grasses on the property drops below 50 per cent and palatability declines. Cows need to lay down fat as soon as summer rain arrives.

The Smiths use a profile of BREEDOBJECT estimated breeding values (EBVs) to produce females that lay down excess fat for energy storage in poorer seasons and maintain a body condition buffer after calving.

Bull selection emphasis is put on positive rib and rump fat, and 400- and 600-day growth EBVs are capped at breed average plus 20kg and breed average plus 15kg, respectively.

Reproductive performance results

The Tieyon research data showed large variations in heifer growth, body condition and resultant fertility between good and bad seasons.

Across good and bad seasons, there were wideranging average daily weight gains (ADG)—for dry heifers; pregnancy rates in heifers lactating for the first time at each muster; and average liveweight adjusted for stage of pregnancy (Av. LWAdj.) across good and bad seasons.

Adequate bodyweight and a good plane of nutrition (ADG) were critical for achieving good conception rates. Over one six-month period in the project, average heifer growth rates fell as low as -0.003 kg/day in the worst years of the drought and peaked at 0.73kg/day during a good season.

Pregnancy rates in lactating first-calf heifers averaged only 15—18% during poor seasons when cattle growth plummeted, but climbed to 74% in April 2011 on the back of two good rainfall years and correlating strong growth rates and improved body condition.

“Our goal now is to have first calf heifers and overall herd conception rates above 90% in good years,” Paul said.

“We have also noted that a higher percentage of heifers are re-conceiving in less than three months after calving in the good years than in the drought years.”

Managing for fertility

“The research project has proven that managing heifers to be in good condition before calving (about score 3.5 on a 1–5 scale) and at critical weights above 420kg before the next mating could significantly increase whole-herd fertility.”

At target mating weights of 300kg, maiden-heifer conceptions at Tieyon have averaged 83% during April musters.

To achieve this and strive for 90%, the Smiths have introduced a regimented approach to early weaning— even in good seasons—and now segregate heifers after weaning for preferential grazing management.

The average calf weaning age has been reduced from eight to five or six months of age, when calves weigh about 150kg or more. This maintains cow body condition and paves the way for higher re-conception rates in the future.

Weaners are fed hay in small yards for up to two weeks, and those selected as breeders are moved to better quality pastures at conservative set stocking rates to boost weight gain to about 300kg for the next joining.

Paul said many animal husbandry practices had been modified to avoid setting back cattle growth patterns.

These included using rings for steer castration, some supplementary feeding in poorer seasons, de-stocking and agisting when necessary, and regular vaccinations for botulism (every three years) and pestivirus (prior to first joining).

Progress report

The Smiths now run a younger breeding herd as a result of finetuning heifer management at Tieyon.

Cows are sold as 10-year-olds and the herd is replenished each year with young, hardy, resilient and more fertile stock.

Paul said profitability improvements were hard to measure because the business was still recovering from the severe drought of the mid-2000s, after which breeder numbers plummeted to 1,800 head.

“We are still here, our herd is improving and the outlook for our business is good,” he said.

“What helped us through was having a plan and we are still focused on collecting records, continuing to finetune management practices and improving our genetics.

“We now have excellent herd reproductive performance figures and have been able to make management and breeding changes based on that solid data.”