Rumen load index and chewing time index good indicators of rumen environment?

Subacute ruminal acidosis (SARA) is a digestive disorder in cows with negative economical effects on milk production. NorFor uses the indicators rumen load index (RLI) and chewing time index (CTI) to ensure a healthy rumen environment in order to achieve a high NDF digestibility and to avoid SARA. When the NorFor system was validated (Volden et al., 2011) it was concluded that increased rumen load index was related to reduced NDF digestibility but it was difficult to find a relationship between rumen load index and ruminal pH. However, this was done on a very limited number of studies.

In a Master thesis, veterinary student Trine Fredslund Jensen worked with a more extended validation, based on 7 American studies with 36 different diets. The aim was to clarify if there is a relationship between rumen load index, chewing time index and SARA. She also wanted to evaluate if the recommended maximum value of 0.6 for the rumen load index and the recommended chewing time of min 32 minutes per kg DM for a diet in NorFor, are appropriate in order to prevent SARA. Results showed that rumen load index is significantly correlated with ruminal pH, milk fat content and the ratio between acetic acid and propionic acid in the rumen. Increased rumen load index decreases all these three variables. However, chewing time index was not significantly related to rumen parameters.

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Patrik Nordgren, CEO