Poor feeding can cause lameness

      A study of foot lameness in Taranaki showed 65% of lameness in cows is caused by walking to the milking shed and another 10% by individual cow variation.  This leaves around 25% of variance unexplained, for which nutritional factors may be responsible.

      Poor nutrition, in particular sub-clinical acidosis leading to laminitis, results in a weakening of the hoof, making it more susceptible to injury.

Looking after the rumen

      Feed eaten by the cow has to be digested by “bugs” or microbes in the rumen.  The microbes ferment forages and most other feeds, producing proprionic and acetic acids, which are absorbed through the rumen wall.

      Plant protein is incorporated into microbial protein and the microbes then pass into the cow’s intestine to be digested.  Keeping the rumen fermenting well is like making wine.  The fermentation has to occur in a balanced an controlled way, otherwise it will result in incomplete fermentation and/or toxins being produced.

      Therefore, care is needed in feeding the rumen microbes, so the fermentation process is enhanced rather than being upset.

What is laminitis?

      Laminitis is inflammation of the soft tissue under the sole and wall of the hoof claw.

     This inflammation damages the joint between the hoof and the tissue underneath an weakens the claw, making it more susceptible to injury.  Laminitis occurs when toxins are released into the blood stream, commonly as a result of acidosis, which occurs when the pH of the rumen becomes acidic (below pH6).

      This is usually associated with excessive levels of readily-fermentable carbohydrate (sugars and starch), which the microbes in the rumen are not able to convert into organic acids an lactic acid fermentation results.

      This may occur when cows are fed readily-fermentable carbohydrate, such as grain, kiwifruit and other high carbohydrate feeds, specially if these are introduced rapidly without giving time for the rumen microbes to adapt.

      Silages contain significant levels of lactic acid and can contribute to rumen acidity.

      It appears from some measurements taken from cows on pasture diets that their rumen pH is dropping below 6 at times, particularly when they are on lush, improved pastures.  The source is the weak organic acids, such as proprionic, butyric and acetic acid.

      The secretion of bicarbonate in saliva normally controls acidity in the rumen.

      When the cow swallows, she takes bicarbonate into the rumen to buffer the pH that is to neutralise the acid.

      Normally, a cow secretes 150-250ml of saliva a minute and to do this she needs to chew for 9-10 hours daily.  If we increase the amount of chewing she does, particularly chewing of her cud, she will produce more saliva and therefore secrete more bicarbonate into the rumen to counteract the acidity.

      Chewing is stimulated by fibre, or what we call effective fibre.  That is, food particles more than 1.7cm long.  When the pasture is lush, there will be insufficient effective fibre to stimulate the required amount of chewing.  This can happen on spring and autumn pastures.

     The best counter measure is to introduce a small amount of fibre, ideally straw, but hay may be the best option available.  Adding a buffer will help. Sodium bicarbonate is often used, but its activity is very short, so magnesium oxide, which lasts longer, may be more effective.

by Chris Pyke, Intelact Consultant