Jm. Watts et al., Variability in vocal and behavioural responses to visual isolation betweenfull-sibling families of beef calves, APPL ANIM B, 70(4), 2001, pp. 255-273
In order to assess the value of vocal response as an indicator of welfare i
n cattle, it is necessary to investigate factors which influence vocal beha
viour of individuals, that are independent of the specific environmental co
nditions to which they are exposed. The effect of parental differences, sex
, age and weight on vocal responses of calves to visual isolation were exam
ined. The relationship between vocal response and the amount of body moveme
nt during isolation were also evaluated.
Seventeen full-sibling families of beef calves (N = 130) were created by br
eeding five sires with 13 superovulated dams. Embryos were transferred into
unrelated cows, which reared the calves to weaning age. Vocal response of
calves and body movement were measured on four occasions, while they were v
isually isolated for 1 min on a single animal scale platform. The first two
observations were made on the day of weaning (mean age 166 days) and the f
ollowing day. At the third and fourth observations their average ages were
278 and 350 days, respectively. On the four occasions 33.3, 34.8, 27.8 and
38.6% of calves, respectively, vocalized. Both sire and family had a signif
icant influence on the number of vocalizations and acoustic properties of t
he sounds. Electronically-measured movement while on the scale was also inf
luenced by sire and family, but there was no relationship between vocal res
ponses and body movement. There was a tendency (P = 0.08) for older and the
refore heavier calves to produce longer vocalizations. In the final observi
ng session, age and weight were positively correlated with fundamental freq
uency and the sound pressure level at the frequency of greatest intensity,
and negatively correlated with the loudest harmonic. At the last two observ
ations, significantly more heifer calves than bull calves vocalized. There
was little difference between the acoustic properties of heifers' and bulls
' vocalizations.
The considerable individual variability in vocal response within a group of
identically-treated calves is partly due to parental genetic influences th
at an independent of rearing and early experience. Other endogenous charact
eristics such as sex, age and weight also influence vocal response. But the
re is: no clear relationship between individual temperament (as assessed by
the amount of body movement during isolation) and characteristics of vocal
response. (C) 2001 Elsevier Science B.V. All rights reserved.