Jm. Watts et Jm. Stookey, Effects of restraint and branding on rates and acoustic parameters of vocalization in beef cattle, APPL ANIM B, 62(2-3), 1999, pp. 125-135
An animal's vocalizations may be a useful reflection of its subjective stat
e of welfare. We attempted to evaluate vocal response as an indication of a
nimal distress. Calves (n = 189) were randomly allotted to four treatment g
roups in a 2 X 2 factorial design, the factors being Branded vs. Not Brande
d and Restrained vs. Not Restrained. On four consecutive days calves were b
rought through a headgate and squeeze apparatus. Restrained calves were cau
ght in the headgate for 3 to 5 s. The remainder were stopped at the headgat
e but not restrained. On day 5, all calves were captured and restrained. Ha
lf the animals were hot-iron branded and half were sham branded using an un
heated iron. During branding, vocalizations were recorded. Digitized files
were used to generate an audiospectrogram and a power spectrum for each cal
l. We analysed 167 calls. During treatment, 65 calves vocalized. More brand
ed than non-branded animals vocalized (58/95 compared with 7/94, P < 0.0001
). Branded animals showed a greater frequency range in the fundamental, or
lowest harmonic, of the audiospectrogram, (68.04 Hz +/- 5.33 compared with
28 Hz +/- 8.74, P < 0.05), a higher maximum frequency (186.66 Hz +/- 5.19 c
ompared with 141.6 Hz +/- 6.6, P < 0.01). and a higher peak sound level (P
< 0.05). The previous 4 days of restraint did not alter the probability of
vocalizing, or any characteristics of the calls. This suggests that measuri
ng vocal response may be particularly useful when the effects of relatively
severe stressors are being investigated. The insensitivity of vocal respon
se to moderate levels of stress may offer an advantage over cortisol or hea
rt rate measurements which can reach high values in response to situational
factors, leaving little capacity to respond to treatment. Analysis of voca
lization may be among the more reliable and least invasive methods of asses
sing acute distress in cattle. Based on findings of this study, we suggest
that vocalization data should be interpreted as statistical properties of a
treatment group, rather than indicating the condition of any individual an
imal. (C) 1999 Elsevier Science B.V. All rights reserved.