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Mixer maintenance key to maximising performance (Nov/Dec 2021)

The mixer wagon is the second most-used piece of machinery on dairy units, so it’s vital to ensure it’s working efficiently. How can producers check, and what regular maintenance is essential?


A typical feeder wagon on a 200-cow unit, mixing 45kg freshweight of a diet per cow per day for a 200-day housed period will handle close to 2,000 tonnes of feed per winter. And producers, quite rightly, need and expect it to work consistently and accurately to mix the correct ration. But Promar consultant Jonathan Hill says many feeder wagons are failing to operate at maximum efficiency and urges producers to invest time in improving feeder operation.

Check knives: excessive wear reduces chopping and mixing performance

“Like any machine, feeder wagons must be well-maintained, properly calibrated and used correctly. If any of these three is not 100% right then performance will suffer.”

He says the starting point is good maintenance is making sure the knives are correctly fitted and in good condition. It is important the operator knows how many knives should be fitted and what the signs of excessive wear are. Sharp knives chop the diet effectively and ensure a homogeneous mix. Once they start to lose their edge the quality of mix and the chop length will decline. The knives at the bottom will often wear out more quickly as considerable pressure is placed on them. Mr Hill says sharp knives require less power to deliver a mix and can help reduce mixing times.

“Take the time to check the knives regularly and replace as needed to keep the feeder working well. Also regularly clean the feeder out to remove stale feed.

Feeder calibration

“Calibration is also crucial to make sure ingredients are added correctly. With high feed costs, it is more important than ever to make sure cows get the amount they need. Weigher inaccuracies are often the cause of diets not feeding as expected. I would recommend calibrating the feeder once a month.”

Mr Hill says that correct operation is also essential. He says it’s not uncommon to hear cows don’t milk as well on the day the usual feeder wagon driver isn’t working. “Anyone tasked with feeding cows needs to follow a standard procedure to ensure consistent feed is supplied. Feeds need to be added in the correct order for the type of feeders and mixing times need to be adhered to. Feeding cows is not a job that can be rushed. Overfilling is a common problem and the cause of poor mixing. Feeder wagons have a stated capacity for a reason so don’t exceed it. Make sure you have sufficient PTO power, as running with a smaller tractor or reduced RPM to save costs is a false economy. Mr Hill adds if the feeder wagon is well maintained, correctly calibrated and used correctly it will work more consistently and efficiently, helping improve performance and reduce costs.

Massey Feeds’ Dai Lewis says inefficient feeder wagon operation can result in inconsistent and under-performance. “If the feeds are not mixed evenly there is a risk of uneven distribution of concentrates. On one unit I visited, most of the straights were distributed at the start of the run, leading to all the cows fighting to eat across a short feed face because they were after the straights ahead of the forage.

“This increased the risk of acidosis in those cows, while others will be consuming a lower energy diet and will either lose milk or body condition.”

Rumen health

A key objective of a TMR diet is to help improve rumen health by reducing fluctuations in rumen pH, typically caused by irregular supply of carbohydrates. If the diet is not mixed and fed out correctly it will impact rumen health, leading to reduced yields and falls in milk protein and butterfat. Over-mixing, in particular, can compromise diet structure.

Mr Lewis says it’s important to watch how a load is mixed to ensure the process is effective. “Few feeder wagon operators spend time watching how a load mixes, but it can provide good feedback.

“It is not unusual for the wagon to mix effectively when it is only partially full, and problems occur as more weight is added. This is an indication that knives may need replacing.

“If low inclusion ingredients don’t mix well, try adding them down the side wall instead of directly over the augers, as these ingredients can stick to the augers and will then never mix.

“And definitely make time to watch a mix when forages change. Wet silages have a tendency of ‘balling’ and not ‘chopping’ correctly, while dry silages may not mix as well. So it may pay to add some water.”

Regular checks and routine maintenance of diet feeders not only maintain operating efficiency, but also extend the working life of the machine and could save on fuel, according to KUHN UK’s John Lovell.

Key areas for attention include: drivelines and PTOs; gearboxes; tubs, augers and knives; discharge; running gear; and control and weigh cells.

“Ensure the PTO is the correct length for the tractor; if too short, it could slide out and end up buckled,” says Mr Lovell. “Guards should also be in good condition, and fitted and chained at both ends. And all grease points on the PTO shaft and drivelines should be greased every 50 to 100 hours.”

All gearboxes should be checked for leaks to ensure correct oil levels are maintained. In KUHN mixer wagons, gearbox oil should be changed every 1,500 hours. Tubs, augers, and knives also require regular inspection. Knives should be intact and not excessively worn. If worn, they require more power and time to chop and mix feed, and this can impact ration quality. Wear to the auger can also affect mixing quality. If increased mixing times are occurring despite knives having been changed, it may be that augers need to be changed or re-flighted.

Feed out: Mixer efficiency is key to maintaining herd performance

“Producers should check all discharge door runners are clear so they move freely and close fully. Monitor the condition of any conveyors or elevators, and tensioners should be checked and adjusted to prevent slippage.” Running gear including chassis, axles, tyres, and brakes is also important. All should be checked daily. “Nut indicators can be fitted to provide a quick visual check of the tightness of wheel nuts. Brakes should be checked routinely and, if the machine is to travel on public roads, at least 25% braking efficiency is required. A handbrake capable of locking two wheels on the mixer should also be fitted,” says Mr Lovell.

Weigh cells

And, finally, check control boxes and weigh cells, which involve high-level technology. “Their accuracy is critical to the performance of the mixer. If there is any doubt about the accuracy of the weighing, always consult the dealer, rather than attempt any adjustment or recalibration yourself,” he stresses.

Taking time to walk down the feed fence after a load has been put out is crucial. “Is it mixed consistently? Are there signs of uneven incorporation concentrate?” asks Mr Lewis.

He says cows are the best critics regarding ration mixing feeding. “If they all crowd in one part of the feed fence then there will be a reason for this. Sorting is a sign of poor mixing and is more prevalent with drier forages. “So look at rejections before refilling the troughs. What if anything is left?

“Time invested in making sure the feed wagon is working and being used as effectively as possible will be time well spent as the cows will milk better, make better use of the diet and help maintain margins,” he adds.

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