| Many of today's dairy farms are very large and operate up to 24 hours/day. The equipment in use is expensive, sophisticated and durable. Owners expect, after investing large amounts of money in fixed assets, that such assets be fully utilized and generate a reasonable pay back. It is a business and there is nothing wrong with the logic. Cow, Milking Machine, Man Interaction
Where problems occur often relates to the unique situation where a human being is using a mechanical device to remove milk from a living dairy cow. Given this three-way interaction it is quite possible that problems may occur with any of the three individual components or among the components. Years ago, before milking machines, it was simply man interacting directly with the cow so only two of the three components were involved. In the future, as robotic milkers evolve, machines may be programmed to milk cows in a prescribed manner every time and no direct human involvement will occur. For the foreseeable future however most dairy operations will continue to have the three-way interaction of cow, man and machine and it will have to be managed properly to achieve optimal results.
For example, if the cows are nervous such as first calf heifers, or the udders are very uneven, three teated or sore it often causes difficulties. These factors tend to put cows under a lot of stress and the stress may override the positive signals normally associated with teat preparation and result in poor letdown. When the equipment does not function properly due to whatever reason, problems! If the milker is unfamiliar with or ignores proper milking procedures, problems! Each of these possibilities is very real and has to be resolved for the overall system to perform up to its potential.
Milk Letdown and Teat and Udder Preparation
One specific topic that I feel needs to be addressed is the actual procedure of milking so that man, machine and cow all perform at their optimum. It starts with understanding the details of milk letdown and the timing of various events.
It is critical to understand what constitutes complete letdown. When cows enter the milking center, leaking milk, it may be misleading. There may be enough milk in the teat cistern to create pressure and leaking. This is common amongst early lactation, high producing cows. This often does not represent true full-scale milk letdown. The way to produce complete milk letdown is to stimulate the teat and teat ends so that the nerves carry signals to the brain and cause natural oxytocin release. This in-turn is carried by the blood supply to the udder where it causes milk letdown. Oxytocin produces an effect in the udder somewhat like squeezing out a sponge.
Milking also requires that the teats be clean, dry and sanitized prior to units being attached in order to be in compliance with milk production rules and regulations. Generally we combine teat sanitation and stimulation of the teat nerve endings into the pre-milking routine. Ideally 2-3 squirts of milk should removed from each teat. This allows detection of significantly abnormal milk. Squeezing the teats and passage of milk through the teat opening is a strong stimulus promoting oxytocin release.
Following this, pre-milking teat dip should be applied to the teats and left on for a period of approximately 30 seconds for maximum benefit in terms of teat sanitation. The teat end should be rubbed while the teat dip is present to help clean and sanitize the teat opening. Finally, a minute after the stripping has been done, teats need to be wiped clean with a single service towel, paper or cloth, and then units should be attached. This interval is critical. Milkers may develop inappropriate habits either through failure to understand the letdown mechanism or due to training that over-emphasizes rapid preparation and unit attachment to save time.
Consequences of Inadequate Teat and Udder Preparation
Frequently what happens is that cows enter the milking facility, teat dip is applied and then within 10-15 seconds it is wiped off and the units are hung. Another routine may involve only a dry wipe of the teats and units are immediately attached. The problem with these approaches is that the pre-milking stimulus is minimal and the cow's body cannot react and experience a complete letdown in 10-20 seconds. The milk that initially enters the milking cluster is only what was in the teat and udder cisterns and once that is removed there is no milk to harvest until letdown occurs and the teat cistern is filled. This situation may lead to a number of issues, all of which are concerning.
One concern is that the liner, for a period of time, is opening and closing on a teat that has no milk. The industry has always been concerned about this issue when it occurs at the end of milking and all automated take-off systems signal machine removal a reasonable time after the flow rate has reached a predetermined low level. This minimizes the time the teat end is exposed to system vacuum with little or no milk flowing. While there may still be a bit of milk left in the gland, the benefits of getting the unit off promptly far outweigh the benefits of harvesting this small volume of residual milk. When this same issue occurs at the beginning of milking the negative concerns are the same in terms of possible damage or injury to the teat end.
Consequences of Inadequate Teat and Udder Preparation
Staph aureus may develop resistance to antibiotics approved and frequently used to treat mastitis. Frequently they are resistant to penicillin based products which, as a group, are the most commonly used products
for treating mastitis infections. Veterinarians may do sensitivity testing to determine which antibiotics are most likely to work, but frequently what should work, based on lab
testing and actual field results, does not correspond.
Early Milking Fall-offs and Liner Squawks
A second concern, when units are attached too soon after initial stimulation, is that the lack of significant milk flow may result in the unit falling-off shortly after attachment or experiencing significant liner squawking, both of which are a concern. The reason for these is simple. Attaching units too quickly means the teat has not swelled due to milk letdown resulting in more likelihood of air being able to pass between the liner and the teat wall. Once the teat cistern milk is removed the liner is attempting to hang on to an empty teat. Frequently it can't and starts to squawk or, worse yet, falls off. Small teated cows and heifers are probably the most vulnerable. This may result in a lot of units having to be reattached at the beginning of milking.
Ideally the milking unit should be attached, approximately one minute after preparation, to a fully distended teat. It will then seal better and stay where it belongs.
Maximizing Peak Milk Flow Rates; Minimizing Milking Time
Finally, there is evidence from a number of studies that indicate properly prepping cows and then attaching milking units approximately one minute later results in higher peak milk flows. This in turn leads to complete milkout in a shorter period of time. Attaching units too quickly after prepping the teats tends to lead to lower peak flows and longer machine on time.
Milking routines therefore need to be developed that allow thorough preparation and stimulation of the teats followed by unit attachment one minute after this is complete. There a number of routines involving one or more milkers that will allow this to happen but the key is to make it happen the same way every milking. Cows are very much creatures of habit and they respond best to consistent routines. Deviations throw them off because they do not quickly adjust to such changes.
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