Technical note: Estimation of feed intake while grazing using a wireless system requiring no halter.

A simple, compact bite counter was used to record dairy cow jaw movements. This information was used to estimate feed intake. The device is composed of a pendulum, a microcontroller, and a transmitter attached to a collar. The microcontroller memory can store the number of bites over 10-min intervals for up to 3 mo and has a battery life of more than 1 yr. The number of bites measured by personal observation, and the values reported by the counter were compared for 5 multiparous, nonlactating Holstein cows. The correlation was linear with an R(2) value of 0.9, unaffected by rumination, and little affected by walking. The collar system avoided the problems often experienced with counters attached to halters. The utility of the bite counter recordings in estimating intake was tested using 8 multiparous lactating cows. The slopes of the regression lines relating the number of bites to feed intake were dependent on the level of available pasture mass (120 or 190 g standing dry matter/m(2)). The feed intake could be estimated by applying linear regression to the number of bite counts versus pasture disappearance. In both cases the R(2) values of the regression lines were >0.7. Although the counter recorded jaw movements during grazing when the head was down, it did not record rumination or mastication when the head was raised because the counter/collar did not contact the jaw in this position. The bite counters were easy to attach to the cows using the collar and could be used effectively by farmers and researchers.