In an attempt to avoid some of the problems of the freshly-calved cow, one of the critical aspects is ensuring pre-calving cows are neither too fat nor too thin. Jeremy Hunt reports.
Ensuring dry cows spend the correct length of time in both the far-off and transition groups, and that they are managed according to their body condition score, are two key areas of dry cow management which could still be improved upon, according to vet James Husband.
“I am encouraging more herds to blood test their cows within 24 hours of calving to see if they are suffering from subclinical milk fever.
“If there isn’t a problem, then the use of expensive dry cow products may not be warranted. You need the data to make appropriate decisions.”
Mr Husband, of the Evidence Based Veterinary Consultancy, says forages fed during the dry period need to be as low as possible in potassium.
“This is very important. The target I like to aim for is to have less than a third of the cows, excluding heifers, in the first 24-hours post calving with a blood calcium level of less than 1.8 millimoles per litre.
“I am encouraging more and more herds to do this blood test. Samples are taken and stored in the fridge. Once there are say six to 10 samples they can be sent for testing, but it is important to be mindful of the time so there’s still an opportunity to use that information to improve prevention strategies for the cows about to calve.
“Taking a blood calcium test in the first 24 hours after calving, as well as a ketone test to check for blood ketones at five to seven days after calving, not only provides cover for milk fever but also flags up potentially higher levels of ketosis.
“This way a herd is covering itself against the two major metabolic diseases. If there is a higher prevalence of hypocalcaemia there may be a need to go back and look at the herd’s milk fever prevention strategy.
“The blood calcium level is very strongly related to several other metabolic diseases – it’s a gateway disease that can cause displaced abomasums, retained cleansings and endometritis. It’s strongly related to metabolic issues that will trip a cow up in early lactation.”
Mr Husband says achieving the correct condition score at drying off is very important.
“Ideally when cows are dried off they should be in condition score 2.5-3.0 and should be carrying the same amount of condition at calving.
“And one thing I’m in favour of is taking some condition off fat cows in the far off dry period if it’s necessary,” says Mr Husband.
“Lowering the starch and sugar levels in the dry period for very fat cows is something you have to do. If you have fat cows at drying off I’d give enough time for a longer dry period with more time spent in the far-off group, but even if it doesn’t actually take the condition off them, taking the starch and sugar out of the diet should theoretically increase their insulin sensitivity so they are not verging on being diabetic when they calve.
Mr Husband recommends that some condition can be taken off fat cows in the far off dry period if necessary.
“In herds where there are fat, late lactation cows I’d consider having a dry period offering a feed that was very low in terms of energy density. These fatter cows could have an extended dry period to potentially take some condition off them.”
But, he stresses, it is crucial for every cow, whether it is fat or thin, to have at least three weeks in the transition group no matter how long it has spent in the far-offs.
Mr Husband says the amount of condition which can be taken off fat cows depends on the length of the period they are dry.
“So an in-calf cow in condition score four could be taken down half a condition score during the dry period while on a very low energy density diet in the far-off group.
“But this needs to be done over a longer dry period – say 70 days or more – because the transition period must be three weeks. To take half a condition score off while a cow is in a three-week far-off group is too risky.
He recommends fat cows are dried off earlier so they calve down carrying the correct level of condition.
“With herds feeding a single TMR diet it’s not possible to micro-manage body condition score in late lactation, so they can get fat especially if the cow has a long calving interval.
“Overfeeding cows with starch during the dry period is a risk, especially when maize silage is being fed.
“I see more fat late lactation cows than thinner ones, but where cows are light in condition I’d still run them in the two groups – far-off and transition – but I’d switch them to the transition group ration a bit earlier to give them longer to gain condition.
“Some herds run a one group dry cow system very successfully but I prefer the two-group system for this reason,” says Mr Husband.
Cows coming into the dry period which are light in condition can be difficult to get weight on.
“It is hard for cows to gain more than half a condition score during a standard dry period. There are some suggestions if you overfeed these thinner cows for longer periods – say longer than six or seven weeks – on a high energy density diet it can cause them to be somewhat insulin resistant when they calve.
Mr Husband is reluctant to ‘push’ thinner cows too much and would not advise a high energy transition ration.
“Palatability of the diet is very important, but I would be wary of piling in huge amounts of starch at an energy density of 11- 11.5MJ/kg. I prefer to aim for 10-10.5MJ/kg and a starch level of 10-14% during the transition period.
“There is evidence showing if you overfeed for too long during the dry period there is a much higher risk of fatty liver,” he says.
High dry matter intake is vital for either fatter or thinner cows in the immediate post calving period. Palatability and adequate trough space are critical.
“Body condition will drive the risk levels of fatty liver and excessive fat mobilisation, but it’s essential to get freshlycalved cows to eat as much as they can.
“Forages must be highly palatable and any straw being fed must be processed extremely well so cows can’t sort through the mix.
“One of the problems we see in a lot of herds, where there is a glut of fresh calvers going through the system, is the short amount of time some cows spend in transition and often in fresh cow groups, if present.
“If you follow back the herd’s health records you will see time and again that the cows with the problems occurred at a time when the herd’s management was under pressure, as for example from a glut of calvings.
“So avoid too many group changes, too many diet changes and not enough time spent in the transition group.
“Some cows may only spend 10-days in there so it is often the underlying trigger that causes metabolic diseases,” says Mr Husband.