Vocal behaviour as an indicator of welfare in cattle
I investigated the use of vocal behaviour in cattle as an indicator of welfare. The first study (Chapter 3) investigated effects of restraint and branding on 189 beef calves. Branded animals gave more, higher, louder vocalizations than controls. Some unbranded animals vocalized, suggesting that restraint during branding may be aversive. Chapter 4 used 17 full-sibling families of calves (N = 130), created using multiple ovulation and embryo transfer, raised by unrelated recipients. Behaviour was measured during visual isolation. Vocalizations varied due to sire and family, suggesting vocal characteristics are partly genetically inherited. Age, weight and sex also influenced responses. Chapter 5 evaluated 307 calves of 4 phenotypic breed groups during routine processing and visual isolation. Phenotype influenced amounts of vocalization, but not acoustic characteristics. More calves vocalized during processing and calls were acoustically different than during isolation. In Chapter 6, steers and bulls (N = 119)were evaluated in visual isolation while other unseen cattle were present, or not present, within the handling facility. Proximity and vocal behaviour of unseen companions increases likelihood that an individual will vocalize. Bulls vocalized more than steers. Chapter 7 studied cow-calf pairs while separated and attempting to reunite, in extensive conditions. As time between nursings increases, so does probability that animals will vocalize. Usually both vocalized while searching, or neither. Vocalization probably indicates motivation to reunite, and may be part of their strategy to locate each other. Measures of the amount of vocalization may be useful in welfare assessment, but should be used alongside other measurements, and to indicate status of groups not individuals. Measures of acoustic properties are preferred. Vocalization of cattle in testing environments is influenced by genotype, phenotype, age, weight, sex, gender and presence and activities of companions. If not controlled, these factors could confound the effects on vocal behaviour of the conditions being evaluated.