According to Dr Andrew Pine of Rugeley-based Premier Nutrition, we should be looking for an average pre-calving CS of about 3.25 instead of the 2.75 a lot of people are now working to.
Speaking at the Dairy Show, he said some people were targeting 2.5 and 2.75 because of the need to avoid having fat cows, but it was not commonly realised that thin cows were also at risk from ketosis.
He said: “Controlled ketosis is a necessary requirement for normal lactation, as the biology of the cow is designed to produce ketone bodies to spare glucose for milk production.
"We have found from our TMS data that the risk of having a serious ketosis problem grows where we have too fat cows with scores beyond 3.75-4, but risk also grows where we have cows that are too thin pre-calving at 2.5, 2.25 and 2.”
The reasoning behind his claim is that a lower average CS means there is the risk of having more thin cows in the herd which are not only subject to ketosis themselves, but are more likely to suffer nutritional ailments and be less productive.
Dr Pine said: “Our advice is to arrange for an average target CS of dry cows between 3-3.25. We do not want them at 4.5 and certainly not at 2.25.
“The risk of having a lower CS target to achieve an average of 2.5 or 2.75 is you will end up with some cows over 2.5, but a lot of them below 2.5, at 2.25 and 2.
“Those thin cows are more likely to be a problem as they are likely to have a higher lameness incidence and have other metabolic diseases at or around calving which predisposes them to an increased risk of ketosis.
“We now know from our 50,000 TMS cow dataset, if a cow has less ability to lose bodyweight in early lactation, it can take milk out of the tank and reduce milk production by 1.5-2 litres at week four, which means a lower overall milk production.”