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Synchronous lying may be an indicator of positive welfare in dairy cows. However, little is known about whether farms differ in the level of lying synchrony and how consistent this is within a farm. Moreover, the level of synchrony may vary within the day. Accelerometers used for estrus detection of cows enable continuous monitoring of synchronous lying of herds. We studied the level, timing and duration of synchronous lying in 8 Holstein Friesian or Holstein dairy herds across 1 year, in relation to grazing and milking management (robotic milking, 2x and 3x daily milking). In 'winter' months (November-March), herds were housed; in 'summer' months (May-September), 6 of 8 herds had access to pasture for 5–8 h per day, the other 2 herds were full-time housed. April and October were excluded because of variable management. Herds had 0.9–1.4 cubicles available per cow. After cleaning individual accelerometer data, herd average lying time was computed per 15-min (900 s) interval. An interval was defined as synchronous lying when the herd average lying time > 540 or > 630 s (i.e. assuming 60% or 70% of the herd was lying). Daily synchronous lying time was defined as the number of synchronous intervals × 15 min. A general linear model was used to assess effects of farm, season, and their interaction on synchronous lying time per day; with Tukey-adjusted pairwise comparisons. Correlations were made per farm per season to assess the association between total daily lying time and synchronous lying time. Across all herds and calendar days, the highest level of synchrony reached was on average 78%. Most synchronous lying occurred between 2AM and 6AM, though this was not true for all farms. Synchronous lying occurred least between 4 and 8 PM. Across farms, average synchronous (60% threshold) lying time per day was 5.9 h in summer (range: 2.7 – 7.9 h) and 5.5 h in winter (range: 1.6 – 9.1 h). In 3 out of 6 farms with grazing, synchronous lying time was higher in summer due to occurrence of synchronous lying during periods with pasture access. On 2 farms, synchronous lying time was higher in winter than summer due to increased synchronous lying at night. Across farms, average daily lying time and synchronous lying time generally showed moderate correlations. Monitoring synchronous lying in dairy herds using accelerometers was feasible, and 24-h synchrony patterns seemed consistent within farms. Its validity as a positive or negative welfare indicator requires further study. • Accelerometer data of cows was used to assess lying synchrony of 8 dairy herds. • Synchronous lying per 15-min was defined as average lying time exceeding 60% or 70%. • Synchronous lying occurred most at night and during periods with pasture access. • Farms showed distinct and consistent herd patterns in timing of synchrony. • The average duration of synchronous lying for a 60% threshold was 5.7 h per day. [ABSTRACT FROM AUTHOR]

From calving, dairy cows are typically milked for about a year, and subsequently managed to have a non-lactating or ‘dry period’ (DP) before next calving. However, the use of a DP may reduce cow welfare because typical DP management involves the cow changing groups and ration. Also, the DP results in a severe negative energy balance after calving. Shortening or omitting the DP may have beneficial effects on cow welfare through fewer changes in management before calving, and a lower milk yield after calving. Our objective was to assess the effects of no DP and a short DP (30 days) with associated management on feeding, lying, and number of steps of dairy cows in late gestation and early lactation. Feeding behaviour was recorded by computerized feeders for 122 periods (42 with a short DP and 80 with no DP) from week −6 to week 7 relative to calving. Steps and lying behaviour of 81 of these cows (28 with a short DP and 53 with no DP) were recorded with accelerometers in week −4 and in week 4 relative to calving only. Effects of DP treatment and parity on behaviour were analysed with mixed models. Before calving, cows with a short DP were fed a DP ration, and moved to a dry cow group. During this time, cows with a short DP spent more time lying (13.7 vs. 12.6 h per day; P = 0.01) and feeding (240 vs. 209 min per day; P < 0.01), and stepped less (663 vs. 1130 steps per day; P < 0.01) than cows with no DP. After calving, all cows were fed the same lactation ration and were housed in the same herd. Cows with a short DP, however, had a lower feed intake (35.7 vs 39.1 kg per day; P < 0.01), and spent less time lying (10.7 vs. 11.6 h per day; P = 0.03) after calving than cows with no DP. Milk yield was negatively correlated with daily lying time (r: −0.22; P < 0.05), but was not correlated with daily feeding time. Also, less time was spent on both lying and feeding after calving than before calving. These results indicate that lying time was not constrained by feeding time. Lying time was positively correlated with energy balance (r: 0.28; P < 0.01). Compared with a short DP with associated ration and group changes, no DP reduced lying time and increased the number of steps in late gestation, and resulted in a higher feed intake and longer lying time in early lactation. [ABSTRACT FROM AUTHOR]