A failure to properly maintain mixer wagons and monitor the effectiveness of mixing are two easily solved issues that could increase milk production this winter on many farms.

This was the key message from Dr Jeff Weyers, a US dairy nutritionist with Zinpro who was speaking at a farmer meeting at Angus Kerr's 400-cow dairy unit at Chrochmore Farm, Crocketford near Dumfries.

Dr Weyers, who has considerable experience working with TMR feeders, says that in many cases, performance can be improved to produce a better mixed diet.

“I am amazed how few farmers take the time to look inside their wagon when it is working to check how well it is mixing the diet. Mixer operation is probably the part of the feeding process that receives the least attention, but it has a huge impact on what the cows are actually fed."

Although his experience is primarily with tub mixers, he says the principles he discusses apply to all types of feeder wagon.

Starting point, he said is to make the knives and kicker plates are correctly fitted and in good condition as in his experience, it is not unusual for operators to actually know how many knives should be fitted and what the signs of excessive wear are. The same is true for the kicker plates which help move feed around a vertical mixing wagon.

Dr Weyers explained that as considerable pressure in placed on the bottom of the augers, the knives at the bottom will often wear out quicker.

“Once you know the machine is well maintained, invest time in looking at how well it is working. A good starting point is to actually watch as a diet is mixed as this is the only way to identify how well it is mixing the diet.

“Watch an entire load as it is filled and mixed. Look for dead spots where ingredients are not being moved and mixed. Their existence is a sure fire sign the diet fed out will not be the diet as intended because it is not being thoroughly mixed.

“Dead spots are commonly caused by worn or incorrectly fitted kicker plates and knives but can also form around the discharge doors. If the door area is worn, it can lead to feed getting caught and not getting moved around correctly. Another common source of dead spots is incorrectly set baffles. If the baffles are too far in, they will slow the mixing process enough to cause feed to stop mixing.

He added that it is common for wagons to effectively mix when it is only partly full with problems occurring as more weight is added which can be an indicator that the components inside the tub are getting worn or missing. This includes the knives, kicker plates and possibly the augers.

Dr Weyers also said that if you watch when ingredients are loaded it is possible to see how well they are incorporated and he recommended adding small inclusion ingredients down the side wall instead of dumping directly over the augers as these ingredients can stick to the augers and will then never mix properly in a small load. When feed remains on the augers it usually doesn’t get pushed off until the wagon reaches a capacity to the height of the auger. During small loads, the feed stuck to the auger may never actually get mixed with the entire TMR.

Load size will affect mixing efficiency too and both small and large loads are a problem. “Overfilling is a common problem and a root cause of poor mixing in my experience. Feeder wagons have a stated capacity for a reason so don’t exceed it.”

In addition, he stressed the need for sufficient PTO power, arguing that running with a smaller tractor or reduced RPM to save costs is a false economy. It is important to keep the PTO running throughout the mixing period to keep feeds moving and mixing too and to load and mix ingredients on a level surface.

The final check farmers should do is to look in the feeder when emptying has finished. If there is feed left on the augers and around the edges then check the kicker plates and make sure the leading edge of the auger is close to the side wall, he said.

With margins under pressure, Dr Weyers argues that a properly maintained and operated feeder will have big benefits, improving accuracy and consistency of feeding while reducing problems with SARA and rumen health.

“We have seen increases of 2kg/cow/day from the same diet, just by replacing the knives and kicker plates and making sure the wagon was doing its job. That’s a lot of potential extra income over a winter feeding period,” he concluded.