Hemsworth, P. H., Barnett, J. L., Coleman, G. J. 1993. The human-animal relationship in agriculture and its consequence for the animal. Animal Welfare 2, 33-51.

The results of our research on both experimental and commercial animals, particularly pigs .. demonstrate that the productivity and probably the welfare of a substantial proportion of farm animals may be at risk due to high levels of fear of humans. Animals who were subjected to rough handling were stressed, and this depressed their growth and reproductive performance. Not surprisingly, they also were fearful of people. On other farms, the stockmen were gentle and considerate with their pigs. These animals were not stressed, they produced better and readily approached people.