UW Student Research: Predicting Liner Performance: How Liners Impact Milking

Contributor: Sonia Gomez

Born in Northern Spain, in a rural area surrounded by small dairy farms, Sonia’s interest in dairy production began when she was young and increasingly grew ever since. She graduated as a veterinarian in 2003 from the University of Santiago de Compostela, and worked as a veterinarian practitioner in her own team for nearly ten years, visiting farms in Spain and Portugal. In 2009 Sonia moved to Madison in order to start a Master’s program with Dr Reinemann in milking machines. She is enjoying her research in liners performance.

Predicting Liner Performance: How Liners Impact Milking

The 2007 revision of International Standard ISO: 5707, Milking Machine Installations – Construction and Performance, states “The user’s manual shall include… sufficient data to be able to choose the liner for a herd,” and “the desired average liner vacuum and/or the desired average liner vacuum during phase b and phase d of the pulsation chamber vacuum records.”  Recent research at the University of Wisconsin Milking Research and Instruction Lab has been conducted to investigate the interaction between liner properties (liner compression, dimensions, materials and shapes) and milking machine settings (vacuum level and pulsation phase durations).  The methods developed to predict liner performance can be used by milking machine manufacturers to provide guidance to users to choose liners and milking machine settings to balance the goals of milking quickly, gently and completely.

Liner dimensions

The liner dimensions specified in ISO 3918 include the mouthpiece diameter, mid barrel diameter and mouthpiece depth.   Mouthpiece depth is a new measurement to provide the user with information to determine the minimum teat length that can be massaged for a specific liner.  The range of mouthpiece depths for commercial liners ranges from about 20 mm to over 45 mm, or a ratio of more than 2:l from lowest to highest. Mouthpiece and mid barrel diameters range from just under 20 mm to over 30 mm, or a ratio of 1.5:1 from lowest to highest.

Liner Compression and Overpressure    

The primary milking machine influence on teat-end hyperkeratosis is the compression applied to the teat-end during the d-phase of pulsation.  Low compression translates into better teat-end condition (reduced hyperkeratosis or teat-end roughness).  The compression developed for any individual liner will also increase with the milking vacuum level.  A new dynamic method of measuring overpressure using the start of milk flow was used to rank the compression applied by a range of commercial liners (Fig. 1). The ratio from lowest to highest overpressure is over 6:1 or more than 3 times larger than the range of liner dimensions. These differences in overpressure we highly correlated with teat end hyperkeratosis scores in field studies.

Mouthpiece Chamber Vacuum                                    

The vacuum developed in the mouthpiece chamber (MPC) plays a major role in the development of congestion in the teat wall, especially during the low flow period of milking (Fig. 2), and the formation of rings at the base of the teat. Methods for measuring MPC vacuum and interpreting its effects on teat wall congestion will be presented.  Teat wall congestion and teat ringing can also have a significant influence on the ease of unit removal.  This information can be used to specify the retract delay (to allow claw vacuum to be reduced before detachment) for automatic detachers.

Vacuum Level and Pulsation settings

After the liner is selected the vacuum level and pulsation settings must be chosen for each individual farm.  We have developed methods to predict the effect of milking vacuum level and pulsation settings on milking speed, teat-end congestion and the risk of developing hyperkeratosis for a specific liner.  An example of the results of one of these liner performance maps is shown in Figure 3.  This information has been previously unavailable to milking managers and we hope that these methods will be used to take some of the mystery out of milking.

References

Mein GA and DJ Reinemann, 2009.  Biomechanics of Milking: Teat – Liner Interactions. Paper Number: 09743, Written for presentation at the 2009 ASABE Annual International Meeting, Reno, Nevada, USA

Reinemann, DJ  and GA Mein, 2010. Review of milking biomechanics research. Proc. 5th IDF Mastitis Conference: Mastitis Research into Practice, JE Hillerton ed. New Zealand Veterinary Association for Coninuting Education, Christchurch, NZ, pp 436-443.

Reinemann, D.J., R. Bade, M. Zucali, C. Spanu and P.L. Ruegg, 2008. Understanding the Influence Of Machine Milking On Teat Defense Mechanisms.  IDF International Conference on Mastitis Control, The Hague, NL.