Crucial period for cows

Smithton Veterinary Service’s Neil Leighton carries an ultrasound machine used on cattle used to detect pregnancies down to five to six weeks. Picture: Bodey Dittloff.

Biology. Disease management and effective calving programs are essential to a productive winter for dairy farmers, according to Smithton vet Neil Leighton.

Based at the Smithton Veterinary Service for the past 25 years, Mr Leighton recently took part in two Animal Health Information days hosted by DairyTas in Smithton and Burnie, with his presentation focusing on the importance of farm biosecurity.

In the winter-spring herds, dairy farmers are thinking about the upcoming calving period, and autumn calvers have already started the process of mating preparation and planning.

Mr Leighton said most farmers stuck within the two main periods “to maintain a tight calving season”.

“The main reason for winter-spring calving is all about feed: matching peak pasture production with peak milk production,” he said.
“Autumn calving herds are generally chasing higher milk payments, but have higher feed costs.

“It’s all about getting the cows in calf as efficiently as possible to achieve one calf per cow per year.”

An estimated 60,000 adult dairy cattle are across paddocks in Circular Head, with the Smithton Vet Service currently in the process of checking around 10,000 to 12,000 Autumn cows prior to mating season.

Mr Leighton added Tasmania was “one of the few states where dairy is rising”, with 90 per cent of the clinic’s work involving cattle from Cape Grim to Rocky Cape.

“The big difference now, because of the size of the herds, is the size of the jobs,” he said.

“Instead of one or two cows, we’re often going out to work with larger numbers.”

Artificial Insemination is commonly used by most farmers for around six weeks, followed by herd bulls for a further six to eight weeks.

However Mr Leighton said the insemination process is not always straightforward: “Dairy cows have been bred for production, and one of the first things that suffers is fertility,” he said.

“Some cow traits are more heritable than others. Fertility is not highly heritable, so farmers and vets have to work very hard to get cows back in calf.”

The issue of risk management for diseases aligns closely with calving and reproductive performance, with common infections such as Salmonella and BVDV (Pestivirus) potentially affecting general health and fertility.

The bacteria ‘Mycoplasma’ has recently caused particular concern for some herds, with the highly contagious bug causing abnormal milk (mastitis) and lameness (swollen joints) in cows.

“It can be really difficult to manage if it gets into a herd,” he said.

“Farmers need to be planning their vaccination programs to protect against diseases like Salmonella and calf scours well before the start of calving.”

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