Precision feed restriction improves feed and milk efficiencies and reduces methane emissions of less efficient lactating Holstein cows without impairing their performance

摘要

A possible driver of feed inefficiency in dairy cows isoverconsumption. The objective was therefore to testprecision feed restriction as a lever to improve feed efficiencyof the least efficient lactating dairy cows. Aninitial cohort of 68 Holstein lactating cows was monitoredfrom calving to end of ad libitum feeding at 196± 16 d in milk, with the last 70 d being used to estimatefeed efficiency. For a given expected dry matter(DM) intake (DMI) during ad libitum feeding, offeredDMI during restriction was set to observed DMI of the10% most efficient cows during ad libitum feeding forsimilar performance. Feed restriction lasted during 92d, with only the last 70 d being used for data analyses.A single diet was fed during ad libitum and restrictionperiods, and was based on 64.9% of corn silage and35.1% of concentrates on a DM basis. Individual DMI,body weight, milk production, milk composition, andbody condition score were recorded, as well as methaneemissions. Feed efficiency was defined as the repeatablepart of the random effect of cow on the intercept in amixed model predicting DMI with net energy in milk,maintenance and body weight gain and loss within parity,feeding level, and time. Milk energy efficiency wasestimated in the same way, predicting net energy inmilk instead of DMI. The 15 least efficient cows ate2.6 kg of DM/d more than the 15 most efficient cowsduring ad libitum feeding with 2 g/kg of DMI lowermethane yield, but similar daily methane emissions.Feed restriction decreased DMI by 2.6 kg of DMI/dfor the least efficient cows, which was 1.8 kg of DMI/dmore than the most efficient cows, and decreased dailymethane emissions by 49.2 g/d for the least efficientcows, which was 22.4 g/d more than the most efficientcows. Feed restriction had no significant effect on milk,body weight, or body weight change. Feed restrictionreduced the variability of both milk energy and feed efficiencies,as shown by a decrease of their standard deviationfrom 0.87 to 0.69 kg of DM/d for feed efficiencyand from 1.14 to 0.65 UFL/d for milk energy efficiency.Despite narrow efficiency differences, the most efficientcows during ad libitum feeding remained more efficientduring feed restriction (r = 0.46 for feed efficiency and0.49 for milk energy efficiency). The 2 efficiency groupsno longer differed in feed efficiency during precisionfeed restriction. Precision feed restriction seemed tobring the least efficient cows closer to the most efficientcows and to reduce their methane emissions withoutimpairing their performance.