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Accurate measurement of herbage intake rate is critical to advance knowledge of the ecology of grazing ruminants. This experiment tested the integration of behavioral and acoustic measurements of chewing and biting to estimate herbage dry matter intake (DMI) in dairy cows offered micro-swards of contrasting plant structure. Micro-swards constructed with plastic pots were offered to three lactating Holstein cows (608±24.9 kg of BW) in individual grazing sessions (n=48). Treatments were a factorial combination of two forage species (alfalfa and fescue) and two plant heights (tall=25±3.8 cm and short=12±1.9 cm) and were offered on a gradient of increasing herbage mass (10 to 30 pots) and number of bites (~10 to 40 bites). During each grazing session, sounds of biting and chewing were recorded with a wireless microphone placed on the cows? foreheads and a digital video camera to allow synchronized audio and video recordings. Dry matter intake rate was higher in tall alfalfa than in the other three treatments (32±1.6 v. 19±1.2 g/min). A high proportion of jaw movements in every grazing session (23 to 36%) were compound jaw movements (chew-bites) that appeared to be a key component of chewing and biting efficiency and of the ability of cows to regulate intake rate. Dry matter intake was accurately predicted based on easily observable behavioral and acoustic variables. Chewing sound energy measured as energy flux density (EFD) was linearly related to DMI, with 74% of EFD variation explained by DMI. Total chewing EFD, number of chew-bites and plant height (tall v. short) were the most important predictors of DMI. The best model explained 91% of the variation in DMI with a coefficient of variation of 17%. Ingestive sounds integrate valuable information to remotely monitor feeding behavior and predict DMI in grazing cows. Fil: Galli, Julio Ricardo. Universidad Nacional de Rosario; Argentina Fil: Cangiano, Carlos Alberto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina Fil: Pece, M. A.. Universidad Nacional de Rosario; Argentina Fil: Larripa, M. J.. Universidad Nacional de Rosario; Argentina Fil: Milone, Diego Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación en Señales, Sistemas e Inteligencia Computacional. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Instituto de Investigación en Señales, Sistemas e Inteligencia Computacional; Argentina Fil: Utsumi, S. A.. Michigan State University; Estados Unidos Fil: Laca, E. A.. University of California at Davis; Estados Unidos

Acoustic monitoring of the ingestive behavior of grazing sheep was used to study the determinants of intake rate and to estimate dry matter intake (DMI) based on biting and chewing sounds. Each of three crossbred ewes (85±6.0kg body weight) were tested in 16 treatments resulting from the factorial combination of two forage species (orchardgrass and alfalfa), two levels of biomass depletion (tall=30±0.79cm and short=14±0.79cm) and four numbers of bites (20, 40, 60 and 80 bites). During each grazing session biting and chewing sounds were recorded with a wireless microphone placed on the ewe's forehead and connected to a digital video camera for synchronized audio and video recording of ingestive behavior. Dry matter (DM) intake rate was higher for alfalfa than orchardgrass (9.4±0.64 vs. 7.8±0.58g/min, P0.05), because sheep increased biting rate (from 17±1.6 to 28±1.6 bites/min, P