5 June 2012

4 minute read

The MLA-supported Cash Cow study of more than 30,000 breeders in northern Australia found that breeder cow condition significantly influenced a cow’s ability to conceive again.

Cash Cow project data shows that females in poorer condition (ie below condition score 3) in the months prior to calving achieved significantly lower pregnancy rates in the next breeding season.

According to Mick Sullivan, Principal Beef Extension Officer with the Department of Employment, Economic Development and Innovation (DEEDI) at Rockhampton, breeders in condition score 3 or better at calving achieved superior re-conception rates to those in lighter body condition.

“We expect cows in a backward store condition (condition score 2) at calving to achieve a pregnancy rate of 20–50 per cent at the subsequent mating, whereas for cows in body condition 3 or better, a conception rate of 60–90 per cent would be expected,” Mick said.

“When cows get run down in condition, their ovaries shut down. It can then take some time after the seasonal break for these cows to regain body condition and for the ovaries to re-commence cycling.

“On a lot of poorer country, and particularly with first-calf cows, they will not cycle until weaned.

“Another benefit of cows in good condition at the end of the dry season is that they have body reserves which enable them to better cope with a late seasonal break, say late January instead of December.”

Mick said that northern cattle producers had three tools to manage breeder body condition: grazing management, weaning and supplementation.

Grazing management

Cattle need adequate pasture to meet their nutritional requirements, and Mick advised that stocking rate was “super critical”.

“If you’re overstocked, animals have to consume more of the lower quality parts of the pasture and also cannot obtain enough forage to satisfy their appetite. Nutrient intake is reduced and animals struggle to maintain body condition,” he said.

“At this time of year (April–May), it’s important to think about how much feed you have on offer. There is unlikely to be much pasture growth from May until the seasonal break, which in many cases won’t happen until December.”

Effectively, the feed on offer at the end of the growing season is what cattle have to survive on until the wet season. Tools such as Stocktake and grazing charts can be used to assess feed on offer, animal requirements and determine how long paddocks can be used.

Pasture photo-standards (2003) are available for most pasture types and are a valuable tool for assessing pasture yields.

Faecal NIRS (near infrared reflectance spectroscopy) assesses pasture quality and can assist planning for grazing management and supplementation. Another important consideration is maintaining adequate groundcover at the end of the dry season to prevent excessive runoff.

Weaning

Weaning is a powerful tool to manage cow condition, Mick said, because the nutritional requirements of a lactating breeder were around 50% above those of a dry animal.

The timing of weaning and the size of the calves weaned is determined by the type of country, seasonal conditions and breeder age.

“On tougher country, weaning earlier in the year and down to a younger age is critical because it’s a lot harder for cows to maintain condition,” he said.

Cows weaned March–May have time to regain body condition while there is still reasonable quality feed.

“On better country, say Mitchell grass downs or brigalow, it’s quite normal that you wouldn’t have to wean calves until May–June, but keep the season in mind,” Mick said.

“Well below normal rainfall by March is a warning to think about how to manage your breeders for the rest of the year, and to take steps to maintain cow condition, such as weaning earlier and weaning calves down to a younger age.”

Supplementation

While dry season protein supplements can play an important role in maintaining breeder condition, Mick suggested they were most effectively used in conjunction with grazing management and weaning.

“Dry season protein supplements are half as effective as weaning in reducing weight loss,” he said.

On phosphorus-deficient country, Mick said wet season phosphorus supplementation was also critical.