New dry cow diet eradicates milk fever and associated symptoms Removing grass silage from the dry cow diet and replacing it with a ration of maize silage, straw and a specially formulated pre-calving concentrate, has seen an 85% reduction in the number of retained cleansings and the almost entire eradication of milk fever at Henry Lewis’ Tack Farm at Bromyard in Herefordshire.

The Tack Farm herd consists of 420 pedigree Holsteins that produce an average of 10,500 litres per year. The flying herd is housed all year round and is fed a TMR ration. However, for the past two years, herd manager Mark Lewis, has struggled to reduce incidences of milk fever, retained cleansings and displaced abomasums.

“It isn’t that we’ve got a particular problem with freshly calved cows, more a case of wanting to reach new levels of efficiency and herd health,” Mr Lewis explains. “We have never had more than a few cases of milk fever per month, and only a handful of displaced abomasums, but we felt that by taking a closer look at our dry cow ration we could reach new heights of performance.”

At calving there is a 25 fold increase in the demand for calcium. And, as modern genetics lead to continually higher yields, the lack of available calcium is resulting in a growing incidence of milk fever related problems. Cows also need calcium for muscular strength and stamina, not only to expel a calf, but also to cleanse the uterus of placental tissue.

If sufficient calcium cannot be accessed during and post-calving, when appetites can be reduced, calving can become more difficult, milk initiation will be delayed and cleansing will be detrimentally affected. These symptoms can result in huge economic losses not only in terms of increased veterinary fees, but also in terms of lost yield and subsequent fertility issues.

With the help of Gill Dickson, ruminant sales specialist for Wynnstay, the herd’s dry cow diet has been given a complete overhaul. The first major change was to eliminate grass silage from the ration. “Grass silage on many dairy units can be high in potassium,” Mrs Dickson explains. “This is due to improvements in grassland management and increased levels of slurry being spread on silage ground rather than grazing pastures.”

Increased levels of potassium can cause cows to become too ‘alkaline’ and less efficient at handling calcium. Consequently, freshly calved cows tend to suffer from milk fever and its associated sub-clinical symptoms of retained cleansings, extended calving, displaced abomasums and poor milk initiation.

In traditional dry cow systems, calcium supply is limited in order to trigger the cow’s natural calcium re-absorption mechanism. However, by lowering the cation-anion balance (CAB) of the diet and making the cows’ tissues more acidic, the ration will stimulate the re-absorption of calcium and allow for proper muscle function, especially in the rumen and uterus.

Dry cows at Tack Farm therefore receive 3kg/day of Wynnstay Prepare nuts for a period of three weeks prior to calving. This specially formulated compound provides a source of anionic salts to reduce the pH of the gut as well as an inclusion of propylene glycol to provide a direct source of energy and make the ration more palatable. The nuts supplement a core dry cow ration of 20kg maize silage, 3kg wheat straw, 1kg spey syrup, 150g urea and 100g limestone.

“Semi-CAB regimes work well for moderate to high yielding herds and have some really advantageous benefits,” Mrs Dickson explains. “By providing a reservoir of readily available calcium at calving, not only will there be fewer incidences of milk fever, but cows will also have an improved appetite post calving and will reach peak milk production much sooner.”

CAB diets have been around for the past 10 years but many farmers have been reticent to adopt the idea, Mrs Dickson reports. “There is a popular misconception that these diets are expensive and complicated to implement. But that is far from the truth. All that is required is regular silage analyses to assess whether or not a particular batch of forage is suitable for feeding to dry cows. If the potassium content of the silage is too high and the cows’ blood becomes alkaline, the silage is simply excluded from the dry cow ration and substituted with a more suitable component such as maize silage which is much safer for close-up cows.”

Prepare nuts are fed at a rate of between 1kg and 3kg per cow per day depending on forage quality, and cost between 60 pence and £1 per day per animal. At just 10 pence more expensive per cow per day than traditional dry cow cake, the cost of introducing Prepare nuts to the ration is easy to justify when compared to the costs associated with displaced abomasums, retained cleansings, reduced yields and veterinary bills for remedial surgical procedures.

The new diet was introduced at Tack Farm at the end of July 2009, with some extremely encouraging results showing after just three months. “Since we switched from grass to maize silage and introduced the Prepare nuts we have seen an 85% reduction in the number of retained cleansings,” Mr Lewis reports. “And I can count on one hand how many cases of milk fever we have seen.”

Mr Lewis also reports a number of further benefits. “It used to take a lot of effort, and drenches, to bring freshly calved cows back into prime condition. Now the cows are much brighter and are keen to eat soon after calving down. They also have more energy during calving and we have fewer assisted calvings as a result.”

The cows are also bulling much more strongly than before, with first service conception rates also expected to improve, and are producing higher quality colostrum which aids calf vitality.

“The nuts are available in bulk, but we choose to feed manually from a 25 kg bag as that gives us an extra opportunity to see the cows at the feed barrier and identify any animals that may be off colour. It is a very simple system that has worked well so far. As long as we continue to see the benefits, there is no need to introduce any further changes,” Mr Lewis remarks.

But Mrs Dickson advises that farmers considering a CAB diet should consult a knowledgeable nutritionist first. “It is always worth seeking expert advice before making significant changes to diet and absolutely essential to test the CAB value of silage so that the new ration can be formulated accordingly. Once established on a new diet, cows will exhibit considerable improvements at calving and will be more likely to perform well throughout the subsequent lactation.”

▲back to top▲