Variability in vocal and
behavioural responses to visual isolation among full-sibling families of
beef calves
J.M. Watts1, J.M. Stookey1,
S.M. Schmutz2 and C.S. Waltz1
1Department of Herd Medicine
and Theriogenology, University of Saskatchewan, Western College of Veterinary
Medicine, Saskatoon, Saskatchewan, Canada, S7N 5B4. 2Department of Animal
and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan,
Canada, S7N 5B5
To assess the value of vocal response as a welfare indicator, it is necessary to investigate factors which influence vocal behaviour, irrespective of the specific treatments which animals experience. The effect of parental differences, sex, age and weight on vocal responses of 130 heifer and bull calves and the relationship between vocal response and body movement during visual isolation were measured.
Five sires and 13 superovulated dams were used to create 17 full-sibling families of calves (2-17 calves/family) by embryo transfer into unrelated cows, which reared them to weaning. Behaviour was observed on four occasions during 1 min isolation on a scale platform. Observations were made following weaning (mean age 166d), the next day, and at mean ages 278d and 350d. Movement was measured using an electronic device connected to the scale. During the first two sessions we observed which calves vocalized. During the last two sessions calls were recorded for spectrographic analysis.
On the four occasions 33.3%. 34.8%, 27.8% and 38.6% of calves vocalized. Sire and family significantly influenced the number of vocalizations, duration, fundamental frequency, loudest frequency, intensity and loudest harmonic. Mean movement scores were influenced by sire (P<0.001) and family (P<0.001), but there was no relationship between vocal response and movement. During the third observation older calves gave longer calls (r=0.39, P<0.02), weight and call length showed a similar trend (r=0.30, P=0.08). In the final observing session, age and weight were correlated with fundamental frequency (rage=0.55, rweight=0.53, P<0.001), sound intensity at the loudest frequency (rage=0.41, P<0.01; rweight=0.53, P<0.001) and loudest harmonic (rage=-0.51, rweight=-0.50, P<0.001). At the last two observations, more heifers than bulls vocalized (P=0.015 and P=0.012, respectively). There was little difference between the acoustic properties of heifers' and bulls' vocalizations.
Sibling and half-sibling beef calves share characteristics of their vocal behaviour, even when gestated and raised by unrelated cows. Some individual variation in vocal response is inherited independently of the effects of early experience. Sex, age and weight also influence vocal response. But there is no clear relationship between the amount of body movement during isolation and characteristics of vocal response.