Behavior and physiological responses to acoustic stimuli in Taurine and Zebuine cattle

Taurine and zebu cattle behave distinctly modulated by their genotype and previous experience. We hypothesized that the greater reactivity of Zebu compared with Taurine cattle during daily routine management practice is partially due to the faster perception of sounds. This study aimed to evaluate behavioral and physiological variables of taurines and zebuines before and after the exposure to six acoustic stimuli and a control (without acoustic stimulus). Thirty-nine cows, comprising 19 Aberdeen Angus, AA (Bos taurus taurus) and 20 Nellore (Bos taurus indicus) were enrolled in this study. Six acoustic stimuli were evaluated. The three sounds evaluated were calves mooing, dogs barking and handler commands (e.g. stimulating displacement of cattle), and the sound frequencies were low (65 Hz), intermediate (8 kHz) and high (20 kHz). At each acoustic stimulus, we considered the first behavioral reaction expressed by the animals and the behaviors were registered in an ethogram. Immediately before and after the acoustic stimuli test, we measured body temperature with a thermographic camera (IRT) at the right and left lacrimal caruncles, and at the muzzle as well we determined blood glucose concentration. Further, on other date, reactivity was evaluated using flight distance and behavior score and the interaural distance was measured. The study was conducted according to factorial considering genetic group and acoustic stimuli, and each cow was considered an experimental unit, totaling 39 cows (19 AA and 20 Nellore). AA and Nellore cows did not exhibit any of the behaviors linked to hearing in the absence of sound stimuli. All acoustic stimuli provoked behavior reactions in both groups, notably handler commands, dogs barking, low and high frequencies lead to increased frequency and odds ratio of presenting head movement, ears directed towards the sound source in Nellore compared with AA. Blood glucose concentration and IRT measured at the muzzle were similar for groups, while IRT at the both lacrimal caruncles increased after acoustic stimuli test only in Nellore group. The interaural distance was shorter in Nellore compared with AA cows. Nellore cows had greater values for behavior score and flight distance than AA cows. Compared with AA cows, Nellore cows are more reactive and exhibit higher frequency of behaviors related to sound perception (e.g., head movement, ears in alert position or directed towards the sound) probably linked to faster sound perception due to their shorter interaural distance.