Free cow traffic in automatic milking systems (AMS)
a case study on nine commercial dairy farms in Sweden
In Automatic Milking Systems (AMS), cows are kept in a free stall barn equipped with one or several milking units (MU). The cows? activities in the system are called cow traffic. There are three types of cow traffic systems: guided, partly-guided and free. Free systems have no gates, allowing the cows access to the feeding and resting areas at any time. This study pre-sents the results of on-farm research on such free systems, especially with a view to produc-tion results, feeding and management routines, animal health, and housing. The underlying field work was undertaken on nine commercial dairy farms in Sweden and comprised of man-ager (farmer) interviews, own observations at the target-barns, and the acquisition of standard data that were collected and stored by the farms? AMS software programmes. The data, cov-ering the system responses and interactions of 837 lactating cows in 15 MUs over a period of 30 days were subsequently processed by aid of the statistical pc-programme SAS and Micro-soft Excel.
With each of the 15 investigated MUs shared by 40 to 65 cows, the milking frequency varied from 2.50 to 2.84 milkings per cow and day at intervals between 8.4 and 9.6 hours. While there was no relationship between milking frequency and annual milk yield or herd size, the latter clearly affected milking intervals in a positive fashion. The number of non-milking (ex-tra) visits to the MUs varied between 0.71 and 1.51 per day. When cows paid up to two extra visits and five visits in total to the MUs, milkings took place at shorter intervals and were more evenly distributed over the day. However, no additional positive development in milk-ing interval could be seen for more than two extra visits. There was a tendency for a signifi-cant negative correlation (p