Supplements are big business... but do they make a difference?

Supplements are big business... but do they make a difference?

Some have scientifically validated effects - for example, fluoride in our drinking water keeps our teeth healthy, and iodine in table salt has reduced the prevalence of goitre. But others are a little less certain.

For example, antioxidants were long thought to protect us against a wide variety of ailments, but studies have now turned up disappointing results.

More isn't always better either - megadoses of fat-soluble vitamins (A, D, E and K) can accumulate in the body and cause disease or death.

Now, I'm not a human doctor - so how does this apply to dairy cattle? Well, there are many supplements available for cows, so let's just look at one example.

Vitamin B12 plays an essential role in energy metabolism and is usually produced by microbes in the rumen.

However, blood levels of vitamin B12 tend to drop in early lactation as energy metabolism increases and the vitamin is secreted in milk.

So, supplementation after calving is popular on some farms - but does it really have an effect? Or are we just producing expensive urine?

To answer this question, I dug through the scientific literature.

Firstly, vitamin B12 was found to have a positive effect in Canadian studies performed on 14 Holstein heifers and 24 Holstein cows in 2005 and 2007.

Supplementing B12 and folic acid resulted in higher milk yields, as well as more solids, fat and lactose (when given weekly 10-milligram injections of vitamin B12, as well as 2.5g of folic acid and rumen-protected methionine).

Injections of vitamin B12 alone appeared to have little effect, with the researchers concluding that both elements were necessary to see a response.

Sounds good, right? Well, a 2013 study of 90 US Holstein heifers and cows found that weekly injections of 10mg vitamin B12 beginning 60 days before expected calving resulted in no significant differences in lactation yield or fat and protein components.

The researchers also looked at body weight, body condition, energy balance and dry matter intake, and observed no response.

Likewise, a 2005 study on 117 New Zealand Friesian cows found that a subcutaneous injection of 60 or 90mg long-acting vitamin B12 made no difference to milk volume, milk solids or fat and protein percentages during the lactation.

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Another 2014 study of 805 Canadian cows in 15 commercial dairy herds found that weekly injections of 10mg vitamin B12 and 320mg folic acid from three weeks before expected calving to eight weeks of lactation significantly reduced the incidence of calving problems in cows from 10.8 per cent to 5.3pc (but had no effect on heifers).

In contrast to the previous studies, however, the vitamin injection decreased milk fat concentration in the first 60 days of lactation.

Milk protein concentration increased, resulting in a lower fat-to-protein ratio. There was no effect on milk yield.

Treatment had no effect on conception rates but there was a reduction in days from calving to submission by an average of 3.8 days.

These effects varied between herds and were more pronounced in heifers.

Hmm. What can we take from these results?

Well, here's a few things to consider.

Firstly, scientific studies that simultaneously look at many parameters are likely to have significant findings by chance.

None of the pro-B12 studies corrected for multiple testing.

If they all consistently found the same thing, this would strengthen the case for running around with syringes full of the stuff - but while some found production effects, the others found health benefits.

The studies should not be ignored, but the evidence is not yet convincing.

Secondly, even if there is a legitimate benefit, the way the injection appears to be used on Australian herds - a single injection given after calving, without the addition of folic acid - would seem to be a much smaller intervention than those attempted in the pro-B12 studies.

If you were going to do it based on these studies, you'd have to add folic acid and increase the frequency of treatment.

Finally, the thing to remember about vitamins is that they're incredibly important ... if you have a deficiency. The evidence for consuming more than the required minimum is poor.

When you're a pirate dying of scurvy then vitamin C is life-saving, but when you eat a healthy diet, you simply pee the excess out.

Cows are more likely to be suffering from vitamin B12 deficiency when cobalt is low in the diet, particularly in sandy well-drained coastal areas.

If this is your herd, then extra B12 will be useful - keep an eye out for animals with rough, pale coats and reduced milk production.

Overall, however, I'd hesitate to recommend it for every herd, especially when you could rule deficiency in or out with the help of your local vet.

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