Considerations when increasing cow size

30 June 2016

There are always jokes about “size matters” but when it comes to mature cow size, how big or how small your average cow is can have a significant impact on profitability.

According to John Webb Ware, senior consultant with the University of Melbourne’s Mackinnon Project, who will be presenting on the topic at the Border Beef Conference later this month, during the past 25 years cow size has been slowly increasing to now average about 550-600kg for British breeds at body condition score 3.

John said (using Angus as an example) the good news is that this has occurred with very little increase in birth weights but with significant improvements in growth Estimated Breeding Values (EBVs), particularly 400 and 600 days.

Bigger can come at a cost

The news to be mindful of, however, is that cows at the larger end of the spectrum cost more to feed and will be no more profitable at high stocking rates with potentially higher risk, more variability in profit and potential consequences on herd fertility if the herd is later maturing and leaner.

Optimising profit

So what cow size will place producers in a position to optimise profit while minimising risk?

According to John’s research, using CSIRO decision making tool GrassGro™ and based on a self-replacing Angus herd on phalaris and sub clover-based pastures using historic climate data, the answer very much depends on stocking rate and pasture utilisation.

“With low stocking rates (pasture utilisation about 35%), increasing cow size was more likely to be more profitable but as stocking rates increased, the benefit of increasing cow size diminished due to increasing feed costs,” he said.

“At high stocking rates (pasture utilisation about 55%), large cows were no more profitable than medium size cows but profit was more variable (higher risk) with larger cows.”

John said a 75% increase in cow size from 400 to 700kg increased its maintenance requirement by 59% - from about 51MJ/day to 81MJ/day for dry cows.

“The DSE rating for dry cows also increases, from 6 to 9.5DSE/head with cow size increasing from 400 to 700kg,” he said.

Size is not the only consideration

Despite impacts of cow size on fertility and reproduction not being factored into John’s study, he highlighted potential risks.

“Herds with larger frame size, especially leaner, can be later maturing,” he said.

“Any increase of frame size of the herd shouldn’t be considered alone but with other traits such as birth weight, calving ease, fat cover and days to calving.”

More information

John Webb Ware T: 03 9731 2225 E:

Read further information on cow size in this recent More Beef from Pastures newsletter article.

Conference details

The Border Beef Conference, supported by MLA’s More Beef from Pastures and the BetterBeef Network, is on Wednesday 20 July, from 8.45am to 4pm, at the Albury Entertainment Centre, 525 Swift St, Albury.

 To purchase tickets go to

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