A TIGHT calving pattern is the key to a productive beef herd.
In an average beef herd of 280 cows, the difference in conception rates of 60 per cent over six weeks compared to 50 per cent over nine weeks, is worth $6000 to the farmer.
- AT A GLANCE
- Who: Bruce Allworth
- What: beef
- Why: tight calving for higher profit
- Where: Holbrook, NSW
- Report: KIM WOODS
That's the message from Holbrook veterinarian Dr Bruce Allworth.
Dr Allworth told a recent Riverina beef field day that most beef herds had pregnancy rates of 90-95 per cent.
"But we need to know over what period are we getting that rate," Dr Allworth said.
"Is it 95 per cent over six or 12 weeks?"
Dr Allworth said the benefits of a tight calving pattern were better grown and older replacement heifers.
Liveweight, age and nutrition were the critical factors when joining.
"Spring joining is easier on heifers as they are on a rising plane of nutrition," he said.
Research in South Australia found that for every 10kg rise in liveweight, pregnancy rates increased 7 per cent.
Dr Allworth said 280kg was a critical mating weight for beef heifers being joined over two cycles, or six weeks.
Twelve-month-old heifers would need to weigh 340kg liveweight to achieve similar conception rates as a 14-month-old heifer at 280kg.
Dr Allworth recommended pregnancy testing heifers 13 weeks after the bulls go into the herd.
"Once the heifers are calving over a tight period, look at the cows and cull any late calvers - this might take three to four years," he said.
And, don't forget the bulls. Dr Allworth urged farmers to make sure their bulls are in good working condition before joining by checking for physical soundness, serving ability and health status.
"I recommend single sire matings as a dominance effect can occur in multiple joinings," he said.
"If a dominant bull breaks down, conception rates could fall.
"In my own herd, I use one bull to 45 heifers over a 21-day joining period."
Charles Sturt University's professor of veterinary reproduction, Peter Chenoweth, said the heritability of fertility in beef cattle was low.
But fertility did respond well to hybrid vigour with crossbred females showing a marked improvement.
Prof Chenoweth said choosing bulls on scrotal circumference could improve fertility.
For bulls with a scrotal measurement 1cm above the herd average, their daughters would achieve puberty four days earlier than average.
Analysing pregnancy testing information was important for beef producers, he said. Information could be used to analyse patterns, make predictions and evaluate the breeding season.
