Prevalence of downer cows in new National Milk Fever Survey

DISEASE SURVEY RI Farm

THE results of the National Milk Fever Survey, launched by Boehringer Ingelheim Animal Health, manufacturer of Bovikalc, has been analysed, with some interesting findings emerging.

The survey, which generated responses from 187 farmers, found a wide degree of variation in how well the signs and possible consequences of milk fever are recognised – with some significant knowledge gaps that could be preventing the condition from being tackled effectively, in particular the inappropriate use of calcium injections for prevention.

The survey found that 78 per cent of farms had experienced downer cows on their farm in the past 12 months, with one third reporting that this was a frequent occurrence. On average, farmers reported six cases of milk fever on their farm each year. This level of clinical milk fever is clearly a significant headache for the farms concerned, but the survey results suggest that subclinical milk fever and its possible consequences may be having a greater impact.

Subclinical milk fever can be a factor in many common fresh cow conditions such as ketosis, endometritis, retained foetal membranes (RFM), displaced abomasum (LDA), stillbirth and reduced milk yield. The vast majority (87 per cent) of farms reported at least one of these conditions occurring sometimes or frequently in the past 12 months, suggesting that many subclinical cases could be flying under the radar.

Whilst awareness of the signs of clinical milk fever was high amongst survey respondents, there was a more mixed awareness of the possible consequences of subclinical milk fever.

Sixty-five per cent knew that retained foetal membranes are associated with milk fever, however just a third recognised the link between milk fever and LDAs, and only a quarter were aware of the link between milk fever and stillbirths.

Farmers were concerned about all the costs associated with milk fever – not just the cost of treatment, but also the cost of lost productivity and the hidden costs. The relative importance of different costs varied considerably amongst farms. Comments on the impact of milk fever included “the subclinical side can be very expensive” and “prevention is definitely cheaper and easier than cure”.

Almost all farms had some measures in place to prevent milk fever, the most common measures being a low calcium diet and/or magnesium supplementation for all dry cows. Many herds were also targeting higher risk cows with calcium supplementation at calving.

When asked about what type of calcium supplementation they were using to prevent milk fever, it was concerning that many farmers are using calcium injections as a preventative measure.

Kath Aplin, Veterinary Adviser at Boehringer Ingelheim Animal Health, comments: “Whilst calcium injections are vital for treating cows with clinical milk fever, they can be counter-productive if used as a preventative measure.

“The artificial boost in a cow’s blood calcium can stop her hormonal system from mobilising her own calcium, so after an initial rise, her blood calcium levels rapidly drop again.

“An oral bolus such as Bovikalc, which contains anionic calcium salts, has a different effect – it not only provides calcium, but also helps the cow to mobilise her own calcium reserves, which is exactly what she needs to do to stay healthy in the longer term as her milk yield ramps up.”

Kath continues: “There is good evidence that targeting high risk cows with a calcium bolus such as Bovikalc reduces the risk of subclinical milk fever, and with it, the incidence of fresh cow conditions, even in herds with a well-balanced dry cow diet and with clinical milk fever well under control. Studies have shown that the cows benefiting most from calcium boluses are lame cows and high yielding cows, but a whole herd approach – bolusing all cows above second lactation – is a simpler option for many herds and is also consistently cost effective.”

The survey revealed the cows that most commonly received a bolus were older cows. Only three per cent of herds were targeting lame cows for calcium bolus supplementation, and 14 per cent were targeting high yielding cows. This highlights some groups of cows that might benefit from calcium bolus administration at calving to reduce the risk of developing those costly conditions associated with subclinical milk fever.

When choosing a calcium bolus, farmers consistently valued ease of use and the amount of calcium provided above other criteria, with cost ranked as much lower importance.

Kath says the Boehringer team will continue to share its whole herd protocol with farmers and the evidence supporting the use of calcium supplementation.

“One Bovikalc bolus given at the first signs of calving and one given immediately after calving is our recommendation, with a further one to two given at 12-15 hour intervals if necessary. It’s simple but could help farmers have healthier herds, with reduced costs and improved productivity.”

She concluded: “I would like to thank the farmers who took part and generously took the time to share their experiences with us. Our team will be doing all we can to provide support and resources to ensure they receive the help they need to more effectively manage milk fever and its consequences on farm.”

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