Dairy cows’ fear of people: social learning, milk yield and behaviour at milking
Introduction
There is increasing evidence that man–animal relationship can have major impact on both production and welfare of farm animals. Dairy cows’ fear of humans can reduce milk production and change their behaviour at milking (Albright and Arave, 1997, Hemsworth and Coleman, 1998) and a reduction in milk yield has been reported for cows milked by relief milkers (Lidfors et al., 1999, Knierem, 1991). Distance kept to a person has often been used as a measure of fear, and some studies show a correlation between distances that cows keep from a person and milk yield (Seabrook, 1994, Rushen et al., 1999, Breuer et al., 2000). In contrast, some studies show no relationship between the distance kept to people and milk production (Dickson et al., 1970, Purcell et al., 1988). However, approach or avoidance of people may not directly relate to physiological signs of stress in the presence of people. For example, we found that defecation during aversive treatment decreased as the treatment was repeated, even though the cows continued to avoid the people treating them (Munksgaard et al., 1997). Factors that influence approach/avoidance behaviour and the relationship to milk production, therefore, need to be investigated in more details.
Gentle handling can reduce the level of fear and make it easier to handle the animals (Boissy and Bouissou, 1988, Hemsworth et al., 1989). However, farmers only have a limited amount of time. If animals are capable of social learning (Nicol, 1995), this may have practical applications; handling of selected demonstrators could reduce the level of fear in a larger group of animals. Studies of social influences on learning in farm animals are few, and have mainly examined feeding preferences (Albright and Arave, 1997, Clarke et al., 1996, Nicol and Pope, 1994, Provenza, 1994) and the acquisition of simple operant responses (Lindberg et al., 1999, Veissier, 1993). No studies have yet examined the social learning abilities of cattle in the context of handling by humans.
In this study, we examined whether milk yield and behaviour was influenced by the presence of an unfamiliar person or a handler who previously had treated the cows either gently or aversively. We also examined whether the distance kept to a handler changed when cows had been observing this handler treating their neighbours.
Section snippets
Animals and housing
In Experiment 1, we used 16 Danish Holstein cows in their first lactation (102±15 days post partum) to examine the effects of fear of people on milk yield (group A), and four cows (two cows in their third lactation and 1 each in their first and second lactation) and six pregnant heifers (1–3 months before expected calving) to examine whether responses to people could be affected by treatment of the neighbouring animals (group B). In week 2 of the Experiment, one cow was omitted in group A due
Distance scores during tests
In Experiment 1, group A, before treatment there was no significant difference in the distance kept from the two handlers (Fig. 1). After three treatments, the distance kept from the gentle handler decreased and the distance kept to the aversive handler increased, and there was a significant difference in distance kept from the aversive and the gentle handler (Fig. 1). Treating the cows for further three times did not significantly change the distance kept to the two handlers. In both tests 2
Discussion
The cows rapidly learned to avoid the aversive handler and approach the gentle handler supporting our previous work (de Passille et al., 1996, Munksgaard et al., 1997) and again shows the ease with which cows distinguish between different people wearing different colour clothing. However, milk yield and residual milk did not differ when either the gentle or the aversive handler was present at milking, even though the cows’ behaviour differed according to which handler was present.
During milking
Acknowledgements
We are grateful to Gynther Nielsen and Anton Steen Jensen for technical assistance and to all the staff at the dairy barn for their help.
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