Brainstem auditory evoked potentials (BAEP) in dairy calves

Abstract

Brainstem auditory evoked potentials (BAEP) are useful to diagnose neurologic and genetic disorders in cattle but normal parameters and its application to detect changes in hearing are not demonstrated. The aims of this study were to develop a protocol for obtaining BAEP in Holstein calves and to establish the normal parameters of peak latencies, interpeak latencies (IPL) and waveforms of BAEP in this species. Ten male Holstein calves, aged 2.5 months and weighting 90.7 ± 4.0 kg were used. All animals were previously sedated with 0.08 mg/kg xylazine hydrochloride administered intramuscularly. The BAEP analysis was recorded using the IHS SmartEP-ASSR program connected with electrode needles placed on the standardized locations of the animal's head. Monoaurally presented broadband click stimuli (0.1 ms) were used for BAEP stimulation, with contralateral masking of 30 dB SPL. Stimuli were presented at a rate of 35.5 pulses per second (PPS) and evoked responses were collected and averaged 450–1500 times for each sound intensity. Earphones were inserted into the ear canal to present the acoustic stimulus and to attenuate environmental noise. Peak latencies, IPL, waveforms and auditory thresholds were recorded and analyzed in the right ear and were like those described in previous papers in adult male bulls. Auditory thresholds obtained in all animals were 33 ± 1.5 dB SPL. Peak latencies were 1.4 ± 0.07 ms (Peak I), 2.4 ± 0.10 ms (Peak II), 3.3 ± 0.10 ms (Peak III), 4.4 ± 0.19 ms (Peak IV) and 5.6 ± 0.28 ms (Peak V). IPL were 1.9 ± 0.12 ms (IPL I-III), 4.1 ± 0.29 ms (IPL I-V), 2.2 ± 0.19 ms (IPL II-V) and 2.2 ± 0.19 ms (IPL III-V). Brainstem auditory evoked potentials are a minimally-invasive method to evaluate level of audition in Holstein calves. In addition, BAEP is a method that can be applied in young calves and it would work on-farm to select the animals with better conditions.