Relationship between rumination time, metabolic condiitons and health status in dairy cows during the transition period

The main objective of this experiment was to monitor the rumination pattern during the transition period in primiparous (PR) and pluriparous (PL) dairy cows and to investigate its relationships with metabolic conditions, milk yield and health status. The study was carried out in an experimental free-stall barn, and involved 32 Italian Friesian cows (9 PR and 23 PL) during the transition phase. The rumination time (RT) was recorded with an automatic system (HR-Tag) and data were calculated and summarized in 2-h intervals. Blood samples were collected during the transition phase to assess biochemical variables related to energy, protein, and mineral metabolism, as well as markers of inflammatory conditions and some enzyme activity. Daily milk yield, body weight, nutritional condition and health status were also recorded. The average RT before calving (-20 to -6 d) was 463 min/d in PR (range 270 to 620) and 522 min/d in PL (range 411 to 640). In the early lactation (15 to 40 DIM), the average RT was 504 min/d in PR (range 400 to 585) and 562 min/d in PL (range 414 to 685), and was positively correlated with milk yield (r = 0.36; P < 0.001). The RT reached the minimum at calving d (262 min/d in PR and 278 min/d in PL). Before calving the percentage of RT during the nighttime was 60% in PR and 62% in PL; while the values decreased after calving (55% in PR and 57% in PL respectively). During the first weeks of lactation, PR showed a lower RT than PL in the 2-h intervals that included milkings. Cows with lower RT before calving maintained lower RT after calving, and suffered a greater frequency of disease than cows with higher RT in late pregnancy. Moreover, cows characterized by mild inflammatory conditions, and without health disorders or only mild health disorders during the puerperium, showed a higher average rumination time (over 520 min/d) during the first ten days of lactation. Conversely, the lower level of rumination time (450 min/d) during the first few days of lactation was observed in cows with subclinical diseases or health disorders. Cows affected by clinical mastitis during the trial showed a reduction of RT and a change of its variability already some days before the drug treatment. Our results suggest that the automatic measurement of rumination time is useful to predict calving time and to obtain information on health status of the animals in a critical period as the transition phase.