Ability to digest explains part to between cow feed efficiency variability
Résumé
Improving feed efficiency may be a solution to increase farms economic and environmental sustainability,
through decreasing feed consumption and maintaining or increasing milk production. The main issue is to
understand why inefficient cows need to consume more feed than the most efficient ones independently of
their energy requirements level. Feed inefficiency could result from a lower dry matter (DM) diet digestibility:
inefficient cows need to consume more feed than the efficient ones to cover their energy requirements. The aim
of this study was to assess the relationship between feed efficiency and DM diet digestibility in dairy cows.
Sixty Holstein cows were fed ad libitum a unique TMR during the 238 first days of lactation. Feed efficiency
was defined as the residual energy intake (REI). The 60 individual REI were calculated as the residuals of the
linear regression of cumulated net energy intake (UFL) not corrected for digestibility differences on cumulated
requirements for fat corrected milk yield, metabolic BW, BCS, empty BW gain and empty BW loss. The
cows were dosed with ytterbium oxide as an external marker during 2 periods of 14 days (2 × 5 days of rectal
faecal sampling) to assess individual mean DM digestibility (known individual DM intake). Intake level (kg
DMi/kg BW) explained 14% of REI variation and DM digestibility explained 9% of REI variation. Intake
level explained 15% of DM digestibility variation. The more efficient the cow is, the lower the intake level is
and the higher its digestibility is. Further investigation is planned to test the hypothesis that inefficient cows
would be able to increase their feed efficiency through restricting their feeding level.