Rumen temperature monitoring to assess feed efficiency of dairy cows
Résumé
Improving feed efficiency can be seen as a solution to increase farms economic and environmental sustainability as it contributes to decrease feed consumption and maintain or increase production. The main issue remains to measure feed efficiency on farm because total feed intake is only available in a few research facilities. However, new monitoring devices offer interesting perspective to find a predictor to assess feed efficiency. Assuming that water intake is highly associated to feed intake, we hypothesized that water efficiency, measured by rumen temperature, could be a predictor of feed efficiency in dairy cows. Feed efficiency and rumen temperature were monitored during the 238 first days of lactation for 60 Holstein cows fed ad libitum a unique TMR. Feed efficiency was defined as the residual energy intake (REI) calculated as the residuals of the linear regression of cumulated net energy intake (UFL, not corrected for digestive interaction due to intake level) on cumulated requirements for fat corrected milk yield, mean metabolic BW, mean BCS, empty BW gain and empty BW loss. Rumen temperature were monitored every 5 min with a rumen thermobolus (San’Phone®, Medria). The daily sum of the difference between the rumen temperature corrected for water intake and raw rumen temperature was used as an indicator of water intake (WI). Water efficiency was defined as the residual water intake (RWI) calculated as the residuals of the linear regression of estimated WI on cumulated milk yield and mean BW. RWI explained 29% of REI variability with a coefficient of correlation of 55%. Feed efficiency assessed with REI can be measured indirectly with RWI which only requires on farm affordable phenotypes: rumen temperature, milk yield and BW. RWI appears as a promising way to include feed efficiency in a genomic selection strategy.