Short-term application of prestimulation and increased automatic cluster remover threshold affect milking characteristics of grazing dairy cows in late lactation

It was hypothesized that reducing cow cluster-on time by increasing automatic cluster remover (ACR) thresholds above 0.4 kg/min would require premilking stimulation of the mammary gland to maintain milk yield. This was tested by examining the interaction between 4 ACR thresholds and 3 premilking treatments over an 8-wk period with 96 mixed-age Friesian-Jersey cross cows being milked twice per day in late lactation (average production: 13.9 kg/d). The 3 premilking treatments were attach cluster immediately (control), attach cluster 60 s after entering the dairy (delay), or remove 2 squirts of foremilk from each quarter and attach cluster 60 s after entering the dairy (Prep). Four ACR thresholds were chosen, where the cluster was removed after the milk flow rate was less than 0.2 (ACR2), 0.4 (ACR4), 0.6 (ACR6), and 0.8 kg/min (ACR8). Measurements included individual cow milk yield, cluster-on time, average milk flow rate, maximum milk flow rate, time from cluster attachment to average milk flow rate, milk yield in the first 2 min, time from maximum milk flow rate to end of milking, and the milk flow rate at predetermined intervals during each milking session. Composite milk samples were collected weekly at a.m. and p.m. milkings to determine composition and somatic cell count (SCC). On 3 occasions during the experiment, postmilking strip yield was measured. No interactions were detected between premilking treatment and ACR threshold in any of the measured variables. Cows receiving the Prep treatment had a 5 to 9% shorter cluster-on time than the control treatment. Milk yield, SCC, postmilking strip yield, and maximum flow rate were not different between the 3 premilking treatments. Cluster-on time of the ACR8 cows was 21 to 29% less than ACR2, but SCC and milk production variables were not different between the 4 end-of-milking treatments despite higher strip yields as ACR threshold increased. Increasing ACR threshold offers the potential to reduce the duration of milking without detriment to overall productivity. The results of the premilking treatments indicate that to achieve the most efficient routine, the operator should attach clusters as close as possible to the first bail in rotary dairies to increase bail utilization in pasture-based systems. If cluster attachment can be sped up and ACR threshold lifted, significant potential exists to decrease herd milking duration and improve labor productivity.