Arrazola, A., Dicker, K., Vasseur, E. et al. 2020. The effect of early housing and companion experience on the grazing and ruminating behaviour of naïve heifers on pasture. Applied Animal Behaviour Science 226, 104993.

Calves reared on pasture learn to graze from their dam and conspecifics during weaning. Social learning can be beneficial for calf performance and welfare, and pair-housing and companionship on pasture have been proposed as management practices to develop efficient foraging behaviour. Yet, the interaction between early housing and the experience of a companion on the development of grazing and ruminating behaviour is unknown. The objective of this experiment was to investigate the effect of early housing and experience of a companion on heifer behaviour during their first grazing season. The experiment was designed as a two by two factorial with six replicates per factorial combination repeated over two seasons. In each season, 12 focal heifers were single- or pair-housed before the experiment began. At the start of each trial season, the focal heifers were placed on pasture for the first time and paired with an unknown companion heifer of similar bodyweight and age. Half of the focal heifers were paired with a naïve grazer companion and the other half with an experienced grazer companion. The experiment started when the newly formed pairs of heifers were placed on pasture (day 0). Posture and behaviour (grazing, ruminating and others) were recorded during the morning and afternoon for both heifers using scan sampling every two minutes for six hours per day on days 1, 2, 3, 10 and 17 after pasture placement. Data were analyzed separately for focal and companion heifers, using generalized linear mixed models, with pen nested in the model as the experimental unit and days on pasture as a repeated measure. The early housing and the experience of a companion had a synergistic effect over time on the percentage of time that focal heifers were ruminating (early-housing: P = 0.048; and companion experience: P = 0.049) but not grazing (early-housing: P = 0.40; and companion experience: P = 0.27). Pair-housed heifers placed on pasture with experienced heifers were ruminating more (14.1 ± 1.5%) than single-housed heifers with naïve heifers (9.8 ± 1.5%; P = 0.02). Over the duration of the experiment, the patterns of grazing and rumination behaviour during the morning and afternoon were similar between focal and companion heifers. These results suggest that early socialization and grazing with an experienced companion (i.e. social model) influence ruminating behaviour on pasture in first grazing season heifers, probably due to social facilitation.

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