Research Roundup is a regular article bringing to your attention recent scientific papers that have been published. This is designed for farmers who want to keep on the cutting edge of new research and technology, with the understanding that ‘new’ information includes ‘ideas that are yet unproven’. The newer the science is, the more uncertain we are about the results – so take what you read with a pinch of salt. With this in mind, we can still report on what researchers are thinking about at the moment, giving us some idea of where we might be heading into the future.
Subclinical ketosis in dairy cows: does it matter?
For the very first edition of Research Roundup, I happened across two European research papers from the Journal of Dairy Science on the topic of subclinical ketosis. The Raboisson study was completed in August, and the Vanholder in May this year, so they’re both very recent pieces of research. It’s always interesting to see what’s trending in dairy science in different regions and subclinical ketosis is a relevant disease for Australian dairy farmers, but not one that we hear about very often.
As a brief explanation, ketosis is caused when cows have insufficient glucose to meet energy requirements – particularly in early lactation. To make up the difference, she moves reserved fat to her liver, where it is converted into ketones (also known as beta-hydroxybutyrate or BHBA). Ketones can be used for energy in place of glucose, but become toxic when there’s too much in the blood. Clinical ketosis (when ketone concentrations exceed ≥3.0 mmol of BHBA/L of serum – often seen as reduced feed intake and a drop in production) is just the visible tip of an iceberg. Cows suffering from subclinical ketosis (when ketone concentrations are between 1.2-2.9 mmol of BHBA/L of serum) are unwell but not severely enough to show visible signs. Subclinical ketosis can only be detected through testing.
But hang on, I hear you ask, if subclinical ketosis doesn’t cause a drop in production or intake, then does it even matter?
Unfortunately, subclinical ketosis is associated with increased risk of disease, reduced reproductive performance and milk quality issues. Our first study, which is a recent meta-analysis* of 23 publications by French researchers (Raboisson et al, August 2014), has uncovered the following results. According to their statistical analyses cows with subclinical ketosis are:
- 5.4 times more likely (than a healthy cow) to progress to clinical ketosis
- 3.3 times more likely to have an abomasal displacement (LDA or RDA)
- 1.9 times more likely to be culled or die early
- 1.8 times more likely to develop metritis
- 1.5 times more likely to retain foetal membranes (RFMs)
What does this mean for you? Well, these results drive home the importance of good feed management during the transition period. Particularly if you’re seeing a high incidence of these issues, it would be a very good idea to take a closer look at the nutritional management of your cows in the three weeks before and after calving.
So, we know that subclinical ketosis is important. But just how common is it? The researchers in our second study (Vanholder et al, May 2014) looked at 23 dairies in the Netherlands to see just how many cows are affected. Through blood testing, they found that 47.2 per cent out of 1,715 cows were affected by subclinical ketosis, and an additional 11.6 per cent had clinical ketosis. This is a mind-blowing proportion of the herd that is either experiencing reduced intake and lowered milk production as a direct result of clinical ketosis, or is indirectly at greater risk of the diseases above due to subclinical ketosis.
They also looked at the different factors that increased the risk of cows developing subclinical ketosis. These were:
- High body condition score (fat cows)
- High parity (second calvers and older cows were at greater risk of the disease)
- Cows that calve under winter conditions
- Longer dry periods
- Previous lactation length (the longer they were, the more likely cows would develop ketosis)
- Litres of colostrum produced
This study made me wonder what the prevalence of subclinical ketosis looks like in our herds. Some of these risk factors seem less important to us here as we have quite a different production system (for example, overly fat cows tend to be less of a problem here, and the winters are not as harsh). So, although it looks like ketosis is all the rage amongst European dairy scientists – how common is it in Australian dairy herds? Have you seen ketosis affect your cows? And if so, then what did you do about it?
1). Raboisson D, Mounié M, Maigné E. Diseases, reproductive performance, and changes in milk production associated with subclinical ketosis in dairy cows: A meta-analysis and review. J Dairy Sci 2014;97:7547-7563.
2). Vanholder T, Papen J, Berners R, et al. Risk factors for subclinical and clinical ketosis and association with production parameters in dairy cows in the Netherlands. J Dairy Sci 2014;98:1-9.
*A meta-analysis is a huge research project that systematically examines scientific papers based on a particular topic – in this case, 23 other publications. By doing this, one group of scientists can compare what each of the 23 other groups did, the results they got and the differences between them. Why would the same topic be studied 23 times? Well, each research team approaches it in a different manner, under different circumstances that can produce different results. An American scientist studying it in feedstall dairies might do it in a completely different manner to a New Zealand scientist looking at it in a pasture-based system. This meta-analysis allows us to compare apples to oranges to lemons, by cutting them all into a similar shape (known as ‘standardization’).