As spring calving herds steam full speed ahead towards calving, it is worth taking the time to check if we are doing everything we can in order to reduce the incidence of transition diseases. These will have a negative effect on production and fertility.
So what are the facts? Spring calving dairy cows are by no means immune to transitional issues and therefore it is worth putting in place strategies to prevent them.
Roche (2003) has reported a subclinical hypocalcemia incidence rate in grazing cows in New Zealand of 33%, where clinical milk fever incidence was only 5%. A Chilean study of spring calving cows found that 56% of the cows studied developed at least one clinical or subclinical disease after calving.
The incidence of individual diseases was 8.8% for retained placenta, 4.2% for clinical hypocalcemia, 11.7% for clinical mastitis, 41.1% for metritis, 19.9% for subclinical hypocalcemia and 16.6% for subclinical ketosis.
It was found that higher BHBA concentrations (Ketosis) and lower calcium concentrations during week 1 of lactation was associated with severe cases of metritis – and that low serum calcium concentration during the same time period was associated with more than one clinical disorder post-calving.
Higher risk post-calving
It is well documented that 25% of deaths occur in the first 60 days post-calving in intensively managed cows. A New Zealand study found that the risk of death in the first month post-calving was 3-6 fold higher than during the rest of the lactation.
The incidence of transitional diseases can have a profound effect on the number of days it takes to get cows pregnant. For a block calving system this can have serious financial implications.
By this time of year spring calving cows are so close to calving that there is little point in trying to manipulate Body Condition Score (BCS). In reality any attempts to do so at this stage will only impact negatively on performance. The objective now is to minimize the incidence of both sub-clinical ketosis and milk fever.
As calving approaches, DMI drops by somewhere in the region of 30%. However, energy requirements remain largely unchanged, which means that the energy density of the diet actually needs to increase. Negative energy balance at this stage will lead to mobilisation of body fat and the onset of ketosis.
The most effective solution is to feed a dry cow role which increases energy intake and also has the correct mineral balance to prevent sub clinical milk fever. This is achieved in two ways: firstly by increasing the intake of magnesium above the antagonistic capacity of forage potassium; secondly by providing anionic salts which reduce the DCAB of the diet, creating a milk metabolic acidosis which promotes the mobilisation of calcium from the bone.
Correct close-up nutrition should also include supplementary vitamin E and selenium. Inadequate vitamin E and selenium intake during the dry period has been shown to reduce colostrum volume (Lacetera etal., 1996). Equally as important, supplementary vitamin E has been shown to reduce udder oedema and the incidence of RFM, as well as promoting neutrophil chemotaxis and superoxide production in early lactation; two important functions of the immune system (Politis etal.,1995,1996).
It is naive to think that spring calving cows are not susceptible to transition diseases or that investing in correct transition nutrition does not make financial sense. An investment of £25 per cow would result in less transitional diseases, less premature deaths and less empty cows.
If you would like any advice on your spring calving herd or diets for your transitioning cows please contact one of the Dairy Technical Team.
Dr Huw McConochie
Head of Dairy Technical Services