PhD student Michaela Gibson and a team at Massey University are exploring what could be causing the fractures, which can affect up to 25% in some herds.
“It’s something that isn’t well recorded and I think with the scrutiny dairy farmers are under, they are probably reluctant to admit they had a heifer break a leg,” Gibson says.
Gibson is two years into her PhD and her work is focussed on the growth and development of dairy heifers.
“I’m looking at how heifers grow and trying to pinpoint where they are most susceptible to growth checks,” she said.
“One of the things we’re seeing in heifers with fractures are growth arrest lines which tells us there are periods of inadequate nutrition causing a growth check but we don’t know where. “I’m trying to understand how heifers grow and what affects it.”
The research incorporates several projects and data is collected from various sources, including other trials from Massey.
They have relied on word-of-mouth to raise awareness that they want bones from heifers who have suffered fractures to scan and analyse. In their first year they had 13 cases and last year they received 120.
“We didn’t really have any expectations and wanted anything we could get and thought we had done well in that first year. Last year was even better,” Gibson recalls.
“We had a group of vets in the South Island that were helpful and more awareness will bring more to the surface.
“There isn’t really an option to indicate how a cow died in recording programmes. We can’t tell if it was lameness or an accident so the database doesn’t have the info we need.”
They are looking at fractures that are truly spontaneous,” she explained.
“For example, the heifer could be walking across a flat paddock or turning in a milking shed when it happens. The odd fracture looks different and they suspect those are due to trauma, but these happen only occasionally.
The window of risk starts just before calving and it can happen up to four months after calving.
Heifers have weak bones as they are not at peak bone mass and their bodies are under extreme stress with their first calving and lactation.
“It seems like that’s the tipping point when the calcium draw from lactation is high, but it’s hard to determine the cause when there’s so many things involved,” Gibson said.
“Some farmers might only have one or two, while other farmers are strongly affected and that’s one thing we are trying to work out: why some heifers are more susceptible than others.”
Gibson grew up on a lifestyle block in Levin. She loved the outdoors, rode horses, and has always had a passion for science. She originally wanted to be a vet till she did some work experience in a vet clinic and decided she would rather get into agricultural science.
A school friend went to university a year ahead of her and passed on some great advice which helped her plan her studies. She then went on to complete a Bachelor in Science with a double major in animal science and genetics Massey.
She also completed a Masters looking at the effects of Theileria Ikeda on bull fertility and libido. But after four and a half years studying, she needed a break. She took a role on a local egg farm while she was job hunting and to catch her breath.
While working on the egg farm she applied for a research technician role, which helped her realise she wanted to do her own research one day. She landed a temporary role with MPI tracing Mycoplasma bovis for four months, and during this time she was talking to lecturers at Massey about potential projects for her to gain a PhD.
“There were a lot that were data or sheep-based, but I really wanted to be involved in something about dairy cows,” Gibson recalls.
“When this one came up about heifer fractures, the molecular side really appealed to me.”
Working out of the Massey campus she keeps on track with her work by treating it like a job and giving herself mini deadlines.
“It’s not like undergrad study where there’s regular deadlines and lecturers keeping track of you. It’s all self-directed and you have to create your own accountability.”
She is enjoying what they are doing and hopes their work will help identify ways to minimise the risk of the incidence of fractures for heifers in the future.
“Farmers shouldn’t take their replacements for granted. They can seem like a money pit before they are milking but it’s important what they do to get them to that two year mark,” Gibson said.
“Spending a bit of extra money is a lot better than possibly losing 25% of your replacements.”
