Increased take-off level in automatic milking systems – effects on milk flow, milk yield and milking efficiency at the quarter level.

Successful management of an automatic milking system (AMS) requires effective functioning of the milking unit (MU). It is well established that an increased detachment level, i.e. earlier removal of the teat cups at the end of milking, can decrease milking time substantially with minimal to no milk yield loss. However, these studies were all conducted at cluster level, and some studies suggest an increase in residual milk or strip yield at increased cluster detachment levels, which indicates decreased udder emptying. These effects of milk flow for cluster detachment are not necessarily translatable into quarter-level milking, which is standard in AMS. The effects of quarter-level detachment levels on milking efficiency and milk flow profiles in AMS have yet to be established. The aim of the study by Dr. S Ferneberg and colleagues was, therefore, to investigate how different detachment levels at the quarter level would affect milk flow profiles and milking efficiency. The sudy was published in the Journal of Dairy Research, Volume 86 of 2019, page 85 to 87, the title being: Increased take-off level in automatic milking systems – effects on milk flow, milk yield and milking efficiency at the quarter level. 

Thirty dairy cows were allocated into six groups balanced by lactation number, lactation stage, breed, and milk yield, and subjected to a 3 × 2 factorial arrangement of treatments in a Latin square design. The treatments were take-off level (TO) at milk flow rates of 0.48 kg milk per minute (T0.48), 0.30 kg milk per minute (T0.30), or 0.06 kg milk per minute (T0.06) from individual quarters with a milking interval of about 7.5 hours. Each treatment period lasted 7 days and the data from the last about 10 milkings per cow and treatment period were used to evaluate treatment effects on milk flow.                                                                                                                            

The mean flow was increased with greater TO without any effects on peak flow or the time to reach peak flow. The total milking time decreased at both the udder and quarter level with greater TO level, with the longest milking times with T0.06. However, the total milk yield at udder or quarter level, or in the different flow phases, did not differ between treatments. The greatest detachment level reduced the total milking time by 0.5 minutes per milking without decreasing the amount of milk. The actual flow at TO was for all treatments lower than the set TO level, which together with the over-milking phase length shows a higher occurrence of over-milking in T0.06 compared to T0.30 and T0.48. This discrepancy between the set TO and actual TO levels is due to the delay time from the signal for TO and actual TO, in this case 6 seconds. Over-milking should, theoretically, be eliminated when milking at quarter level, but in the current study, milk flow dropped below the over-milking limit and, sometimes, to 0 before take-off occurred. This was likely due to short, steep decline phases. This occurred in all treatments, but the time from set TO to actual TO was greatest at T0.30, while the length of the over-milking phase was longest on T0.06. The duration of the increase phase was approximately 0.5 minutes for all treatments, but was longer for T0.06 compared to T0.48. The plateau phase was approximately 1 minute long and the duration was not affected by treatment. The decline phase was longer with lower TO, but with no difference in milk yield harvested during this phase. This indicates sufficient emptying of the udder occurred when the greatest detachment level was applied.                                                                                                                                                                                                                                    

The data suggested that milk flow decreased to a rate below the over-milking limit within the 6-seconds delay time required for termination in all treatments, but the duration of over-milking was shorter for the greatest detachment level compared to the other treatments. The researchers concluded that setting a detachment level at a greater milk flow rate will reduce the duration of over-milking without affecting the amount of milk  when applied to cows in mid-lactation during quarter-level milking. They also suggested that the steepness of the decline phase of the milk flow curve might have a larger effect than the actual detachment level on the duration of over-milking.