Vitamin D shows promise in transition

03 Jul, 2017 01:04 PM
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Rachael Rodney won the Australian Dairy Conference Young Scientists Communication Award.
What we're feeding in our work is a semi-activated form of vitamin D, called calcidiol,
Rachael Rodney won the Australian Dairy Conference Young Scientists Communication Award.

Researchers at Scibus and the University of Sydney are dishing up transition diets including calcidiol and anionic feeds and seeing exciting improvements in cow health and productivity.

The transition from late gestation to early lactation is a risky time for dairy cows. About 80 per cent of the diseases that affect adult cattle occur during this time leading to substantial costs to industry and have negative animal well-being outcomes.

Rachael Rodney is a PhD student working at Scibus and the University of Sydney looking into what cows are fed in the weeks before calving to improve cows' transition to lactation and reduce impacts of metabolic disease.

Miss Rodney said that incidence of disease during this period was high due to a large, and sudden, increase in demand for energy, protein and nutrients at the onset of lactation.

Giving birth was a risky business in

all species.

"When cows are unable to meet the sudden change in demands either from their diet or reserves stored as body tissue, they can get into trouble," Miss Rodney said

"How cows are managed during this pivotal time, particularly what they are fed, has long-lasting effects on their production and health."

Miss Rodney said that they were particularly interested in milk fever, a condition that occurred when cows had low blood calcium.

"Between 3 per cent and 10 per cent of cows suffer milk fever, although this can be much higher on some properties," she said.

"Milk fever results in decreased production, increased incidence of other health problems, and in severe cases, cows can die.

"Reducing milk fever is all about prevention. Getting the mineral balance and dietary cation-anion difference (DCAD) right in the pre-calving diet will make a big difference."

The DCAD describes the relationship between potassium, sodium, chlorine and sulphur ions in the diet. Where the DCAD is negative, the body becomes slightly acidic, increasing the sensitivity to hormones involved in calcium metabolism and encouraging bone turnover.

"On farm, we aim to give close-up cows a negative DCAD diet to prevent hypocalcaemia," Miss Rodney said. "We can do this by using anionic feeds in the diet to increase the intake of chlorine and sulphur.

"Only a very small amount of calcium is available from body reserves, including bone, so increasing calcium absorption from the diet is really important."

This has led them to start examining the effects of feeding supplementary vitamin D to transition cows.

Often called the sunshine vitamin, due to the body's ability to produce it when exposed to sunlight, vitamin D is essential for many metabolic functions, including an essential role in calcium absorption and metabolism.

It might seem unusual to feed cattle a vitamin they produce naturally, but Miss Rodney discussed that there were different forms of vitamin D.

"Just like people, cows produce enough vitamin D for normal metabolic functions," she said. "However, this vitamin D must undergo two transformations in the body to become useable.

"What we're feeding in our work is a semi-activated form of vitamin D, called calcidiol, and at higher doses than cows can make naturally."

In work conducted with the University of Florida Miss Rodney and colleagues fed close-up cows either vitamin D3 (the form of vitamin D made in the body from exposure to sunlight) or calcidiol, in combination with either a positive or negative DCAD diet for three weeks before calving. Cows that were fed the combination of calcidiol and anionic feeds had higher concentrations of calcium in their blood both before and after calving.

A negative DCAD diet eliminated cases of clinical milk fever, down from 23 per cent, and calcidiol reduced incidence of retained placenta from 31 per cent to 3 per cent and metritis from 42 per cent to 23 per cent.

Miss Rodney said these treatments were not just having positive effects on incidence of disease but looked promising for milk production as well.

"The cows fed calcidiol produced almost three extra litres of milk and 250 grams more milk solids each day," she said. "Changing something for just three weeks before calving is having long-lasting effects on cow health and productivity.

"This research is exciting because it shows that increased production doesn't have to come at a cost to health if metabolism is properly integrated."

Miss Rodney said that despite such promising results, this was just one piece of the puzzle.

"Getting the diet right is a balance," she said. "This type of treatment must be combined with high-quality transition diets and good management into lactation".

Miss Rodney is working with Adjunct Professor Ian Lean at Scibus, to continue this work as well as examining the effects of other ingredients in the diet, such as fats and protein, on dairy cow health, production and fertility. Their research is supported by Scibus, the University of Sydney, Dairy Australia, DSM, Arm and Hammer Animal Nutrition and the University of Florida. D

*Rachael Rodney presented this paper as part of the Australian Dairy Conference Young Scientists Communication Award, which she won.

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