Assessing feed efficiency in early and mid lactation and its associations with performance and health in Holstein cows

Objectives were to evaluate the associations between residual dry matter (DM) intake (RFI) and N (RNI) in early lactation, from 1 5 wk postpartum, mid 9 15 assess production performance risk of diseases cows according RFI lactation. Data 4 experiments including 399 Holsteins used this study. Intakes DM N, yields milk components, body weight, condition evaluated daily or weekly for first 105 d postpartum. Milk yield by 305 postpartum was also measured. Incidence disease 90 survival up 300 Residual calculated lactation as observed minus predicted values, which based on linear models that accounted major energy sinks, output, metabolic changes, adjusting parity, season calving, treatment within experiment. Cows ranked RNI categorized into quartiles (Q1 = smallest RFI, Q4 largest RFI). Increasing efficiency resulted decreases (depicted Q1 Q4; ?0.93, ?0.05, ?0.04, 0.98 kg/d), DMI (16.0, 16.9, 17.3, 18.4 net (NEL) (26.8, 28.4, 29.0, 30.8 Mcal/d), NEL balance (?9.0, ?8.1, ?8.2, ?5.5 Mcal/d) during but no differences changes energy-corrected associated with (Pearson r 0.43, Spearman ? 0.32) (r 0.44, 0.36) 0.91, 0.84). Similarly, 0.42, 0.35). During more efficient consumed 3.5 kg/d less 19.3 vs. 22.8 kg/d) 31.6 25.8%), at same time 39.0 39.4 38.6 39.3 components did not differ compared quartile least cows. Furthermore, 305-d yield, incidence Collectively, rankings are repeatable across stages. The most feed-efficient Phenotypic selection measurements is improved without affecting health dairy