Stock Health Strategies for grazing high protein pastures

30/05/2011 3:27:38 PM

Dr Colin Trengove

Losses of stock can be due to the highly digestible nature of legume dominant diets with high nitrogen and low fibre content. This predisposes animals to a rapid build up of ammonia in the rumen & nitrogen in the blood which can lead to sudden death

Losses of lambs and young rams are a common occurrence in winter/spring from a condition known as Red Gut.  It occurs every year, but is more prevalent when seasonal conditions suit the growth of lush clover or lucerne dominant pastures – especially those that have been winter cleaned.

 

Typically lambs or adult sheep and even weaner cattle are found dead without signs of a struggle.  It can be confused with enterotoxaemia (pulpy kidney), but a post mortem usually reveals an enlarged cherry red intestine and the animals don’t tend to “go off” as quickly as with ‘entero’.

 

Losses are due to the highly digestible nature of legume dominant diets with high nitrogen and low fibre content.  This predisposes to a rapid build up of ammonia in the rumen & nitrogen in the blood which can lead to sudden death.  As a consequence, few sick animals are found.

 

Prevention Strategies - Options include:

• Do not winter clean legume pastures ie leave the grasses and weeds in the pasture mix.  The purpose is to provide greater variety in the diet and reduce the overall fermentable nitrogen intake.  This is a good strategy provided grass seeds are not a problem and the pasture is primarily for grazing. 

 

• Allow grazing of more native or ‘rougher’ pastures ie rotate between the legume & ‘native’ pasture at least every 3 days.

 

• Provide low protein pasture hay or straw as an ad lib supplement in the paddock at all times to ensure adequate fibre intake & restrict the high nitrogen/protein intake. This does not hamper growth rate as it provides a more balanced diet. 

 

• Feed ad lib oats or barley while grazing legume pasture to balance the excess nitrogen in the diet & optimise weight gain. This is best provided via a self-feeder where the access to grain can be restricted to prevent grain overload or acidosis.

 

• Give a one ml (or cc) dose of Vitamin A, D & E under the skin every 8 weeks as a preventative treatment as non-protein nitrogen such as nitrates and nitrites can be excessive in lush green pasture and result in blocking the formation of vitamin A in the liver.  This is an essential vitamin for immune strength in the animal. 

 

• Spray the pasture with a foliar mineral mix every 2 months including: 2kg/ha magnesium sulphate (Epsum salts), 1kg/ha Solubor Boron, 200gm/ha copper sulphate, 100 gm/ha cobalt sulphate & 2kg/ha molasses to promote good stock & pasture health.  Use coarse spray jets & include copper last along with warmed molasses (dilute with hot water) to ensure easy mixing & spraying.

 

• Ultimately, it is advisable not to allow livestock to have continuous access to risky legume dominant pastures.  Best to follow the recommendations of comprehensive soil and plant tests provided by experienced consultants as the Australian Perry Agricultural Laboratory www.apal.com.au to encourage a more sustainable strategy.