Capacity studies on DeLavals sort gate DSG10

Sammanfattning: In the dairy production it is necessary to be able to sort cows. Dairy cows are sorted for many different reasons i.e. regrouping into production strings or for treatments i.e. inseminations, pregnancy and health checks, vaccinations or hoof trimmings. One labour saving way of conducting sorting is by using an automatic sort gate. DeLaval’s sort gate DSG10 is a multiple sort gate that can sort cows in up to five different directions when the dairy cows are returning to the barn from the milking parlour. The sort gate capacity is calculated during the planning process with a theoretical formula based on parlour capacity (cows/hour), percentage of cows to be sorted, distances within the sort gate system, walking speed and time for one cow to pass the DSG10. In this study the two constants in the formula, walking speed andtime for one cow to pass the DSG10, were evaluated through time studies conducted on four dairy farms in Sweden and the United States of America.The time studies were conducted by clocking cows when passing through the DSG10 sort gate. To be able to compare the conditions on the different farms these were documentedconcerning layout in the sorting area, animal environment and management strategies on the farms with photographs, measurements, sketches and interviews with farm staff. From the collected data it was found that walking speed of cows is about 1 m/s. It takes in median 6 seconds for unsorted cows to pass the sort gate and 17 seconds for sorted cows to pass the DSG10. It was found that lame cows walked slower than other cows. Therefore a percentage was added as an extra parameter to the formula to allow for lame cows. The time for all unsorted cows to pass the sort gate was lowered to 5 seconds and an extra time of 4seconds for every lame cow was put in. However, when evaluating the different formulas it was concluded that lame cows can still be a tricky figure to use, since it can be difficult to forecast the herds claw health.On farms with parlour capacities under approximately 350-400 cows per hour it is sufficient with one DSG10, and on farms milking up to about 800-850 cows per hour it wouldtheoretically be enough with two DSG10’s working at a time. These approximations will be lowered if distances within the sort gate system, percentage of cows that is to be sorted and percentage of lame cows are high.