The behavior of dairy cattle in the transition period: Effect of blood calcium status.

The aim of this study was to objectively assess, using an automated behavioral monitoring system, the association between lying and activity behavior in the pre-calving, calving, and post-calving period between multiparous and primiparous cows with either a) normocalcemia b) subclinical hypocalcemia or c) clinical hypocalcemia at calving. Behavioral data and blood serum samples were collected from 51 multiparous and 21 primiparous Holstein dairy cattle. Blood samples from the coccygeal vein were taken within 24h of calving and serum was analyzed to measure total calcium concentration. Cows were classified into one of three categories: normocalcemia (serum calcium concentration ≥ 2.0 mmol/L), subclinical hypocalcemia (serum calcium concentration below 2.0 mmol/L, absence of clinical signs), and clinical hypocalcemia (clinical signs and successful treatment). An activity sensor (IceQube, IceRobotics Ltd., South Queensferry, United Kingdom) was fitted to the right hind leg of cows 3 wk prior to their expected calving date. Data for lying time, standing time, number of steps, and the total number of standing and lying bouts (postural transitions) were automatically collected and summed into 15-minute blocks. Behavioral variables were summarized into 2h periods and 24h periods prior to analyses. Mixed-effect models were used to analyze cow behavior in the entire 14 d before calving (d -14 to d -1), on the day of calving, and the entire 21 d post-calving (d 1 to d 21). In the precalving period, multiparous cows with normocalcemia had fewer postural transitions (18.5 ± 6.9 no. /d) compared to cows with subclinical hypocalcemia (23.5 ± 8.0 no. /d) and clinical hypocalcemia (23.5 ± 8.6 no. /d). However, there was no association between blood calcium status on lying time (min /d) or step count (no. /d) for multiparous cows. For primiparous cows, the step count of cows with subclinical hypocalcemia remained constant across the period, whilst the step count of cows with normocalcemia decreased from 842.8 steps/ d on d -14 to 427.5 steps/ d on d -1. Post-partum, cows with clinical hypocalcemia were less active (fewer steps) and spent 88 min/d (1.5 h) and 125 min/d (2.1 h) more time lying down compared to cows with subclinical hypocalcemia and normocalcemia, respectively. This shows that clinical hypocalcemia is associated with significant long-lasting behavioral effects on cows during the critical post-partum period.