Precise feeding during the dry period is essential if farmers are to have healthy and productive dairy cows, according to a leading Dutch vet.
Speaking at a recent DairyCo farm walk in Cornwall, Dirk Zaaijer said that inaccurate feeding during the dry period caused tremendous problems after calving and throughout the entire lactation. Although many farmers were aware of problems caused by negative energy balance, this was only part of the issue.
"There is a close link between fertility and nutrition," he said, adding that many cows were taking longer and longer to conceive after calving, primarily due to inadequate nutrition during the dry period.
With 70-80% of a cow's energy derived from the rumen, it was essential to feed for optimum rumen health, said Mr Zaaijer. This meant maximising vital bacteria and rumen fill, ensuring a decent rumen mat, and feeding for optimum papillae growth, through which nutrients were absorbed. The best feed for dry cows was good quality grass silage, providing the correct balance of acetic acid - for calf growth and milk fat, and propionic acid - for glucose production, with minimal butyric acid, a cause of ketosis.
Cereals and maize silage often contained too much propionic acid, leading to excessive glucose production and fat cows, he explained. "Very often the dry cow is being overfed and that is a real problem." Fat deposition in the liver reduced liver function and its ability to produce glucose when needed, leading to a negative energy balance after calving. If insufficient volatile fatty acids were fed during the dry period, cows could not form decent rumen papillae, leading to problems in absorbing feed in the critical two months after calving. "You must always get your forage and feed tested so that you know what you're feeding," stressed Mr Zaaijer.
Cows grazed over the dry period should be kept on bare paddocks with low phosphate and potash contents, he added. They should be supplement fed with good quality grass silage or straw (with a chop length of 4-5cm), sugar beet or fodder beet - all of which were nutritionally ideal and good for rumen fill. Producers should monitor their dry cows to see if they were eating well and always had full rumens, said Mr Zaaijer. "Dry cows should never look hollow, as they will be breaking down their body fat. But body condition is of less importance than whether a cow wants to eat all the time." A cow that was off its feed was a sure sign that something was wrong - as was a dull and starey coat. "It is a signal for the farmer to do something."
Often producers increased concentrate feed levels sharply after calving to boost milk yields - but the high levels of propionic acid could very quickly cause acidosis. This would kill off rumen bacteria and produce lipopolysaccharides, which blocked the production of luteinising hormone and therefore delayed ovulation, he added. "This is what is happening in most cows these days, and that is why the calving interval is extending and extending - because the cows don't ovulate."
Incorrect feeding during the dry period could also cause milk fever, due to poor metabolisation of Calcium. This, in turn, reduced rumen function and accordingly increased the risk of acidosis and delayed ovulation. Milk fever also affected uterine contractions, and therefore increased the risk of E-Coli infection, said Mr Zaaijer. "Milk fever is one of the biggest problems on dairy farms - and for every case there are five sub-clinical cases."
Any health challenge that reduced a cow's willingness to eat could lead to further problems like displaced abomasums (DA) after calving, he added. "The rumen should drop down and fill the space when the cow has calved - but if it's not full, it won't, leaving more space for a DA."
Fortunately, all of these problems could be addressed by correct feeding during the dry period. "You do have to be precise. But you can feed one dry cow ration to keep it simple. Avoid fat cows in late lactation, keep their rumens full, and increase concentrate levels wisely after calving. It's all preventable - it's all about management."