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Energy Efficiency of Grazing Ruminants – Stacey Gunter

Stacey focused on techniques for measuring energy efficiency to calculate Metabolisable Energy in grazing cattle and explained a new method that is measuring energy efficiency in the field, using an automated head chamber system that measures methane, carbon dioxide and oxygen in the breath of animals as they put their head in a trough to consume a ration.

The ‘gold standard’ of measuring energy efficiency of animals is using respiration chambers for complete gas exchange measurement. This method only allows short term measurement and does not allow in field use. There are many factors such as animal welfare issues, stress causing decreased feed intake (usually approximately 20% reduction) and disrupted feed selection which mean that respiration chambers are not always reflective of the ‘real environment’ for an animal. Also, it is very expensive.

An alternative to respiration chambers is the Greenfeed automated head chamber system, which draws a breath cloud from an animal each time they visit a trough, and simultaneously measures methane, carbon dioxide and oxygen. This new technique was used in a 77 day experiment with cattle, using alfalfa pellets to entice animals into the machine to measure breath clouds. Results calculated from these experiments were very close to other research using respiration chambers, which supports this new technology. More extensive research to validate results is planned.

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