Over the past two decades research in milking management has focused on decreasing the time that units are attached to cows by researching optimal teat stimulation and prep-lag time, pulsation ratios and liner compression and raising automatic take-off settings.
Optimal teat stimulation and prep lag time
Prep Lag time is the time from the start of teat stimulation, to milking unit attachment.
Nearly 50 years ago (1980) Ram Sagi achieved, a higher milk yield, milk flow rate, and a shorter “machine on time” on 12 cows, that had at least 20 seconds of manual stimulation and a lag time of not less than 60 seconds.
Until 1994, more controlled studies on small numbers of cows and the same stimulation routine, showed similar results.
About two decades ago with the onset of electronic computerised monitoring of milking efficiency and milking parlour throughput, it was possible to see if optimal teat stimulation and prep lag time was practiced in commercial herds during each milking.
At the 5th IDF Mastitis Conference in 2010, Ginsberg et al. presented an analysis of the milking procedures, individual cow performance during milking, irregular milking operations and parlor throughput efficiency from 32 herds with thousands of cows supporting the results of the pioneering experimental work.
This presentation showed that low peak flow times and bimodality indicates that the udders were not properly stimulated or that the cluster was attached prematurely.
Today, an optimal teat stimulation and prep lag time of 60 to 90 seconds is recommended and/or practiced on most farms world-wide.
Pulsation and Liner Compression
Cows have been milked with the same basic assembly of a teat-cup shell and liner for the past 100 years. The results of many comparative experiments indicate that liner dimensions, design and composition usually have a greater effect on milking characteristics than any other machine factor.
The exact time when milk flow starts depends mainly on the mounting tension and wall thickness of the liner together with the pulsation rate and ratio.
During the past 35 or more years, various attempts have been made to measure or to estimate, by mathematical modeling, the force, pressure or compressive load applied by the liner to live teats or to various designs of artificial teats.
The remarkably wide range of published values suggests that the different measurement methods have great influence on the results obtained.
It is likely that each method provides a measurement of different aspects of liner compression, average over a surface area, maximum at a point, pressure applied to the teat canal and/or other forces applied to the teat. (Mein, Reinemann and Thompson 2013).
ISO defines pulsation as the cyclic opening and closing of the barrel of a teat-cup liner, primarily to limit the development of congestion and edema in the teat tissues during machine milking by providing massage to the lower part of the teat in the closed liner (d-phase).
Liner Compression is defined as the mean compressive pressure which is applied to the inner tissues of the teat apex by the liner during the d-phase whereas over-pressure is defined as the mean compressive pressure, above that required to stop milk flowing from the teat, which is applied to the inner tissues of the teat apex by the liner during the d-phase. Thus, over-pressure is a major component of Liner Compression.
The opening and closing time (a and c phases) of the liner are dictated by the length and diameter of the pulsation tubing and are constant with all types of pulsators.
Electronic computerised monitoring of pulsation characteristics has allowed us to manipulate the pulsation rate or the length of the b and d phases to achieve the ISO-specified minimum d-phase of 150 milliseconds, in order to have sufficient time to provide congestive relief of the teat end during the d-phase. Longer than 150 milliseconds will reduce milking speed, as a larger percentage of the pulsation cycle will be in the massaging phase rather than being in the open milking phase (b-phase).
To ensure fast, complete and gentle milking, milking speed is optimized when the duration of the b-phase is between 500-600 milliseconds and teat end vacuum within a range of 32–42 kPa during peak milk flow.
In order to facilitate easier analysis and better understanding of what is happening during the milking process; (milking time tests) the IDF Milking Equipment and Methods action team initiated the development of a quarter milking analysis-device that is small and light enough to be taped to a teat-cup during milking. This device logs the vacuum during milking at 4 points in the milking cluster and has made the performing of milking time testing like: teat end vacuum levels, vacuum fluctuations, liner slips, pulsation settings or take-off settings much easier and more feasible to perform.
Take off settings
Over-milking starts when the milk flow from the alveoli to the teat cistern is less than the flow out of the teat canal.
Automatic cluster takeoffs were introduced in the 1970`s to measure the total milk flow from all four quarters of the udder to the cluster and remove the cluster at a pre-determined flow rate.
In the vast majority of cows the front quarters of the udder produce less milk than the back quarters, therefore the front quarters “milk out” before the back quarters (Rasmussen 2004). Despite this knowledge, historically cows were considered “milked out” when the milk flow rate decreased to 200 gr/min and most ACR’s were set to this level.
Early studies by Sagi (1978) and Rasmussen (1993) concluded that the cluster can be safely detached at a flow rate of 400 gr/min.
More studies between 1997 and 2010, with different management strategies, goals and higher detachment settings, supported the results of these previous studies. (Stewart & Reid 1997, Stewart et al. 1999, Stewart and Godden et al. 2002, Maggliaro and Kensinger 2005, Billon et al. 2007, Jago 2010).
Field experience in the last 20 years demonstrates that adjustment of the factory default settings on automatic cluster removers, regardless of the number of milkings or daily yield, can significantly improve teat condition and parlor throughput, while maintaining the quality and volume of milk harvested.
Recently take off settings on more than 20 farms milking three times a day in Northern New York State (Virkler et al QMPS, Cornell, in publication 2019) were raised to 1270 gr/min, a kilogram per minute higher than the original take off settings of half a century ago.
As in all of the previous studies, all of the farms showed a reduction in milking unit-on time while maintaining the quality and amount of milk harvested, additionally to a significant improvement of teat tissue condition.
Nonetheless there are large differences in the minimum take off setting recommendations by milking advisers in different countries as well as the default settings of the milking equipment suppliers, spurring work by experts of the IDF Machine Milking and Methods action team, to compile a bulletin “Teat cup and cluster removal strategies for cows and small ruminants” that was published last year
Over the past two decades we have shown that good teat stimulation with a prep-lag time of not less than 90 seconds, together with optimization of the ratios of the b and d pulsation phases in milliseconds (not %) and raising automatic take-off settings, has led to higher milk flow rates, thereby decreasing the average time that the milking unit is on the cow, with no detrimental effects on milk production or udder health.
This allows producers to milk more cows at each milking shift with no additional labor cost.
Additionally by alleviating the negative impact of machine milking on the teat tissue, we see a significant improvement of teat tissue condition consequently enhancing animal well-being in the milking parlor.