Does the time of day when recently fresh heifers are introduced to the lactating herd affect their acclimation and subsequent performance? A group of British researchers, led by farm animal welfare specialist Niamh O’Connell at Queen’s University Belfast/Agri-Food and Biosciences Institute, conducted a study to find out.
Fresh heifers were introduced into five groups of 18 animals each (12 cows and six heifers). Non-experimental heifers were removed from the groups as new heifers were added. The study compared the outcomes of heifers added between 6 and 8 a.m. (after morning milking) to those of heifers added between 4 and 6 p.m. (after evening milking).
Each experimental heifer was observed for a continuous two-hour period immediately after joining the resident group. In addition, each heifer was observed during four, five-minute periods (at 30-minute intervals) during the two-hour period after feeding on one day each week for one month after introduction to the group.
Introducing heifers to the resident group after evening milking appeared to improve welfare during the initial mixing period by decreasing levels of aggression to which they were exposed. However, this treatment did not promote an increase in overall lying behavior. There was no statistical difference between the two groups in terms of bodyweight or body condition loss.
Heifers in the morning group had higher feed intakes during week two after mixing and spent longer periods of time feeding, and it is suggested that this reflects an increased willingness to compete for food. However, milk yield did not differ between treatments. Overall, the decrease in received aggression, coupled with a lack of adverse effects on production performance, suggests that it is beneficial to introduce heifers into the main dairy herd after evening milking.
This research was reported in the July 2010 edition of the Journal of Dairy Science.