Cover story

Heifer tracks

The figures took pastoralist Keith Holzwart aback. The owner-manager of Avago Station, situated 600 km south of Darwin, guessed that second calvings were fewer – but not that much fewer. “I often wondered if the calving percentages and the weaning percentages were what everybody said they were, then how come we weren’t turning off more cattle in the Territory? It just didn’t add up,” notes Holzwart. “But Tim’s work made us realise how much we didn’t know, and he quantified what we didn’t know. He put figures to it. They were major surprises for us.”

Avago was just one of 14 stations across the Territory that participated in the Heifer Research Project undertaken by Schatz and his small team between 2004 and 2009. They documented the problem, showed the scale of the problem, and came up with strategies for addressing that problem. Much of their valuable research will be added to the larger Cash Cow project currently taking place across northern Australia. Cash Cow is looking at the productivity of mobs on commercial properties in northern Australia. Broader in scope, the research will identify and quantify the factors behind mob-level reproductive performance.

Schatz’s research showed that producers can double their fi rst calf pregnancy percentages by increasing body condition through setting moderate stocking rates, using better paddocks and providing mineral supplementation. “As a general rule – when the cows are skinny not many of them get back in calf, or it takes a long period of time until they build up enough condition to start cycling again and have another calf,” explains Schatz. “So if you can maintain your animals in good condition, then you’re much more likely to get a calf every year. But if your animals are in poor condition, they might only have a calf every second or third year.”

Although the research results were dramatic, they were unchallenged by producers. Because of the huge scale of numbers on Territory cattle properties, it is often very difficult to know what is happening among individual animals. To find out the researchers had to enlist pastoralists to participate over the lengthy testing period. They then went onto the participating properties and tagged up heifers by putting radio frequency identification devices in their ears, allowing the scientists to individually identify animals and record data electronically.

“They’re bloody brilliant. They’re interested. They’re dedicated, enthusiastic and work well and truly above beyond what they’re paid to do because they have a very personal interest in it. There’s a very special relationship between the [department] and the pastoralists.”

The device - a button ear tag - has a radio frequency identification number on it, so when the animals pass a reader antenna in the crush, their unique ID number is recorded, along with their weight and whether they are lactating or not. Then the heifers are pregnancy tested and, if they are pregnant, a determination is made on how many months pregnant they are.

About 7000 animals were monitored it was found that problems arise because lactation places a great nutrient drain on the animal’s body as heifers produce milk for their first calf as well as trying to finish their own growth into maturity. Their body condition deteriorates as nutrients are mobilised for lactation. Often their condition gets really poor with the end result being low pregnancy rates for the second calf.

Schatz believes that the prime factor affecting conception rates is the animals’ condition during the mating periods. Pastoralists should aim for a start of mating weight of 280 kg in maiden heifers (300 kg for pure Brahmans). He produced a pair of charts that show the pregnancy rates that are likely from different mating weights. Producers can then use those charts to budget and work out how much they can afford to spend on supplementation if they aim to feed animals up to a higher weight. “It brings a bit of science into it rather than just guesswork. People can work out their likely return on investment if they spend money on increasing heifer joining weights,” says Schatz.

Holzwart is already trying to make sure his heifers are up to weight before putting them with bulls. Over the five year period, he was impressed at the way Schatz and his team of government researchers went about their work. “They’re bloody brilliant,” exclaims Holzwart. “They’re interested. They’re dedicated, enthusiastic and work well and truly above beyond what they’re paid to do because they have a very personal interest in it. There’s a very special relationship between the [department] and the pastoralists.”

If Territory cattlemen take the recommendations on board, they will see a higher ratio of heifers having their second calves without missing a year and, at about $300 per weaner, even a small rise in calving rates will mean substantial financial returns. “The Territory industry is really progressive now,” says Schatz. “The producers are interested in the science and they know that they have to run an efficient business if they want to be profitable. We’ve got a lot of dynamic research happening now, a really good relationship with our producers, and we’re doing this research in partnership with them.”