Short communication: Evaluation of an eating time sensor for use in pasture-based dairy systems

摘要

The assessment of grazing behavior is importantfor research and practice in pasture-grazed dairy farmsystems. However, few devices are available that enableassessment of cow grazing behavior at an individualanimal level. This study investigated whethercommercially available Smarttag “eating time” sensors(Nedap Livestock Management, Groenlo, the Netherlands)were suitable for recording the grazing timeof cows. Smarttag sensors were mounted on the neckcollars of multiparous Holstein-Friesian cows in a herdin Taranaki, New Zealand. Cows were randomly selectedeach observation day from the milking herd for 8separate days across a 1-mo period. Trained observersconducted 90-min observation periods to evaluate therelationship between the sensor eating time measureand grazing time. A set of 5 defined cow behaviors (2“head up” and 3 “head down” behaviors) were assessed.In total, observations of 37 cows were recorded in 14sessions over 8 d in the study period, providing 55.5total hours of observations. Observation data werealigned with sensor data according to the sensor timestamps and grouped into matching 15-min intervals.Interobserver reliability was assessed both before andafter the main trial period, and the mean percentageeating time per observer had a coefficient of variationof 0.46% [mean 93.2, standard deviation (SD) 0.425]before and 0.07% (mean 96.3, SD 0.074) after. In themain trial, the relationship between observed (mean70.8%) and sensor-derived (mean 69.3%) percentageeating time over the observation period gave a Pearsoncorrelation coefficient of 0.971, concordance correlationcoefficient 0.968, mean difference 1.50% points, and SD5.8% points. Therefore, sensor-identified percentage“eating time” and observed percentage active grazingtime were shown to be both very well correlatedand concordant (in agreement, with high correlationand little bias). Therefore, the relationship betweenobserved and sensor-derived data had a high degreeof agreement for identifying cow grazing activity. Inconclusion, Smarttag sensors are a valid and useful toolfor estimating grazing activity at time periods of 1 hor more.