Health at grass

Published 20 April 12

Health at Grass

Problems associated with health at grass manifest themselves in two main ways, instant digestive type and long term herd performance issues, explains Chris Coxon, DairyCo extension officer.

"It is usually more straight forward to identify the cause of the instant 'digestive type' problems such as hypomagnesaemia (grass staggers) and bloat.  But those that are longer term issues, with the potential for body condition change which can influence fertility in the milking cow and lead to calving problems in the dry cow, are often harder to identify and address," says Chris.

"However, the key to controlling both these issues comes back to the same principle - know what the grass is worth, what proportion of the diet it makes up, and balance accordingly.

"An easy statement to make on paper but by using the Forage for Knowledge grass recording results, alongside developing your own farm recording of assessing growth rates, it is possible to get a good understanding of the main components on dry matter, energy and protein. Your own growth rates will give you a good match for grass intakes and completes the picture," he adds.


"The management strategies for staggers are well versed but the condition still affects a high number of farms.

"You will be lucky to see the early symptoms of a 'nervous' flighty cow and a staggering gait as the onset is usually very rapid and fatal.  Hence the clear need to take basic steps to control the condition with supplementing magnesium being the main action, either through your concentrate feed or direct into a TMR ration. Your feed supplier or nutritionist should guide you on the appropriate inclusion but 60g/cow/day of calcined magnesit somewhere in the ration is the usual standard.   

"To further minimise the problem, management such as avoiding potash application in the spring is recommended, as this can lead to 'easy' uptake by the plant, offsetting the magnesium level in a rapidly growing grass plant."

"Don't forget that slurry has high levels of potash so early doses on grazing can exaggerate the potential risk.  Also trying to minimise sudden ration changes and supplementary feed reductions are good practices to adopt."


"For those farms with clover rich swards the potential of bloat is a risk but with some practical management the problem is readily controlled. 

Turning 'hungry' cows onto lush new pasture, together with foggy, wet days will increase the risk, as will changing from a grass sward to a clover rich field in one feed. 

As with any diet too much variation adds to the digestive upset potential, and overall if concerned closely monitor cows one hour after turnout to check for distress.

If the risk is looking high anti-foaming agents are available for either drenches or water supplies."

Chris continues: "For the longer term issues the use of records will be key to highlighting the problem areas.  What the dry cow ate six to eight weeks ago will have a large bearing on the health of the freshly calved cow. Peaks in the occurrence of metabolic disorders relating to fatty liver diseases such as retained foetal membranes, must be documented well to diagnose the original cause. 

"The management of dry cow rations being the main focus on many farms now, and with the high potential feed value that grass offers together with its poor cation:anion balance, the potential in a ration needs to be managed well to limit intakes if drys are at pasture.  Balance it with a low energy fibre source such as straw that will satisfy the appetite without compromising the important need to maintain the body condition of the dry cow.  

"Work with your vet and nutritionist to assess the dry cows as well as the milkers during the season, with a review of last season's problem areas always a worthwhile exercise.

"Overall grass should be viewed and fed just like any other forage," says Chris. "If you analyse it and judge the intakes well to keep the diet as consistent as possible, and use the data available to adjust rations as the season progresses, the incorporation of grass into a ration should lead to low levels of problems.The benefits should appear in helping to lower feed costs while maintaining or hopefully increasing business performance." 

For more information on health problems at grass see both Grass+and Feeding+.