The effect of different degrees of 'positive' human-animal interaction during rearing on the welfare and subsequent production of commercial dairy heifers

A 3-year study tested the hypotheses that brushing each heifer for 5 min per week in the weeks preceding calving (long term positive treatment: PT) while the heifers were unrestrained, is sufficient to improve subsequent parlour behaviour and production, and this could be influenced by the extent of the PT. Four intakes of commercial dairy heifers (total n 148) managed under typical UK conditions were divided into treatment (T) and control (C) groups. The PT for the four treatment groups comprised of brushing each heifer for 5 min per week in the weeks preceding calving for either 30 min, 65, 155 or 245 in total for the different groups (equating to 6, 13, 31 and 49 weeks before calving). In the first 4 weeks after calving T heifers had 19% faster milk letdown (P < 0.01) than C. Kicks in human presence accounted for 7.1 % of the variation in milk yield (r(2) = 0.071, P < 0.001) and 46% of C's kicks were in human presence compared to 38% of T (P < 0.05). In the first week after lactation T heifers who had received 30 min of PT stamped 59% less at udder handling (P = 0.017) compared to their respective C. The T heifers who had received 155 min of PT during rearing displayed violent kicks 74% less than their C (P < 0.10). Heifers who had received 65 min PT had 75% less time spent on them during the milking routine (P < 0.075). This was reflected in a significant difference in milker's score. Heifers appear to settle between Weeks 3 and 4 as there are no significant differences in behaviour of all heifers as a group. There was a treatment and week interaction for many variables and in Weeks 3 and 4 there are still differences in milking parlour variables between Tand C at Week 4. This suggests that the PT quickened the T heifers' acclimation to the milking routine. Toconclude 30 min of PT in the 6 weeks prior to calving appears sufficient to reduce subsequent fear response to humans in the parlour demonstrated through improved behaviour when being milked. (C) 2008 Elsevier B.V. All rights reserved.