Use of Automatic Cluster Removers in Milking Dairy Cows

Posted: May 7, 2005

The primary goals in milking dairy cows are to get as much milk as possible from each cow while keeping labor costs low and maintain high milk quality.

 In order to achieve these goals there are several important decisions that farmers make. These include milking frequency, cow preparation routine, type of equipment to purchase, and when the end of milking occurs for each cow. Milking equipment manufacturers have developed automatic cluster removers (ACR, also known as automatic take-offs) to determine end-of-milking. Automatic cluster removers determine when the milk flow rate is low enough to detach the milking machine from the udder. Use of this equipment allows greater consistency than is possible with manual machine removal and also allows for a reduction in labor. As dairy farms get larger there is more pressure to increase the pounds of milk/unit of labor or pounds of milk/hour of parlor operation. Thus, there is interest in optimizing parlor efficiency.

To really take advantage of automatic cluster removers, dairy farmers need to have the correct settings for milk flow rate. In general, the higher the flow rate setting, the quicker the unit will determine the end-of-milking. This is desirable from the standpoint of reduced labor costs and is thought to reduce the stress on teat ends. Overmilking from excessive milking time may lead to mastitis. However, there is likely a point at which a higher ACR setting leads to a reduction in milk yield. Since most farm income comes from milk sales, the loss in milk is very undesirable. Thus, the correct ACR setting on a farm is likely a compromise between machine-on time and milk yield. The primary purpose of our study at Penn State was to evaluate the effect of three ACR settings (1.06, 1.32 and 1.76 #/min) on machine-on time and milk yield. A second objective was to determine if there was a difference in response between heifers and older cows.

The study used 60 lactating Holsteins (20 heifers and 40 lactating cows). Cows were milked twice per day. The three ACR settings were studied over 12 weeks in a design that was balanced for days-in-milk and stage of bST cycle. Data were collected from almost 10,000 individual cow milkings in a double-10 parlor with an Afifarm system for automatic data collection.

Results showed that there was a significant reduction in machine-on time as the ACR setting was increased.

ACR Setting
ACR Setting
ACR Setting
Machine-on time (min) 6.3 5.9 5.6
Milk Yield/cow/milking (#) 43.4 43.8 42.5

Cows milked 0.4 minutes/milking quicker when the setting increased to 1.32 #/min flow rate, and an additional 0.3 min faster when the setting was increased to 1.76 #/min. There was no significant difference in milk yield as the ACR setting increased from 1.06 to 1.32 #/min, but there was a significant reduction in yield as the setting increased to 1.76 #/min. The 1.3 pounds of lost milk per milking that we observed at the 1.76 ACR setting may represent a substantial herd loss if multiplied by the number of milkings per day, times the number of cows milked. The average milking time for the 1.32 setting was 5.9 min, which is very acceptable for cows that averaged 87.6 #milk/day. The number of cases of clinical mastitis was also not different among the three groups. There were 3, 2 and 3 cases for the 1.06, 1.32 and 1.76 ACR settings, respectively. Longer studies must be performed before we can make definitive statements about the effect of ACR setting on somatic cell counts, but this study showed no obvious differences. Our study also showed that there was no difference in response between heifers and cows, so that one parlor can milk both groups equally well.

Some caution is needed in interpreting these results. Herds with significantly different milk production, different milking frequency, and different pre-milking routines than ours may lead to somewhat different results. However, the principles will likely be similar.

In conclusion, it appears that the best ACR setting for most PA dairy farms may be to select the highest ACR setting that does not reduce milk yield. An ACR setting of 1.32 # milk/minute was optimal in our study. This approach will allow farmers to harvest the optimal amount of milk while reducing machine-on time, labor costs, and potential teat-end stress.

Complete results and full discussion are in: (Magliaro and Kensinger, 2005. J. Dairy Science 88:148-153.)

R. S. Kensinger, Professor of Animal Nutrition & Physiology
and A. L Magliaro, Research Aide, Dept. of Dairy & Animal Science