Relationships between energy balance during early lactation and cow performance, blood metabolites, and fertility: A meta-analysis of individual cow data

This study was designed to contribute the understanding of relationships between energy balance (EB) in early lactation [4 21 d milk (DIM)] and fertility traits [interval start luteal activity (SLA), interval first observed heat (FOH), conception artificial insemination (AI)], their associated with cow performance blood metabolites 4 150 DIM. Individual data (488 primiparous 1,020 multiparous lactations) from 27 experiments analyzed. Data on performance, EB (on a metabolizable basis), were available for all cows, whereas progesterone (to determine SLA) periodic metabolite 1,042 1,055 lactations, respectively. cows analyzed separately, sets 2 parity groups divided into quartiles (Q1–Q4) according average during DIM (EB range Q1 Q4: primiparous, −120 −49, −49 −24, −24 −3, −3 92 MJ/d, respectively: multiparous, −191 −79, −79 −48, −48 −22, −22 93 respectively). Differences production compared. In (4 DIM), moving Q4 mean DMI intake increased ECM decreased. During same period, fat content, fat-to-protein ratio, plasma nonesterified fatty acid β-hydroxybutyrate concentrations decreased, protein content glucose both cows. When examined over entire experimental period many trends intakes remained, although magnitude difference much reduced, did not differ The percentage FOH before 42 (from 46 72% 41 58% cows). Interval calving SLA decreased increasing DIM, these occurring 9.8 10.2 earlier, respectively, compared (primiparous cows), 7.4 5.9 (multiparous For each 10 MJ/d decrease delayed by 1.2 0.8 However, neither days AI nor that conceived affected daily either or this is likely reflect return less metabolically stressed status at time AI. These results demonstrate reduced lactation, had no effect service.