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Shedding light on milk-production benefits (Oct 23)

Optimising lighting in housing, for both milkers and dry cows, will improve health, welfare and productivity. We spoke to an independent consultant to find out more.


Small changes can often add up to a significant improvement in margins, and one change that could benefit many herds and dairy businesses is investing in lighting.

“Producers are increasingly familiar with how making small changes such as in managing a cow’s time budget and providing sufficient trough space can improve yields,” says lighting specialist Richard Hooson, from “However, one cost-effective gain that is often overlooked is managing lighting levels – both in terms of quality and quantity – in cow buildings.” All mammals are influenced by circadian rhythms, which are physical, mental, and behavioural changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark.

“These rhythms are in-built hormonal responses to allow a cow to maximise growth, reproduction, and yield,” says Mr Hooson. “And these responses have been honed through thousands of years of evolution. “What we now better understand is how we can influence management to optimise the responses by working with the cow’s natural body clock to maximise milk yield and welfare.”

Longer days

Mr Hooson adds that there is research that shows that offering milking cows a 16-to-18-hour day and between six and eight hours of ‘night’ will increase yields by up to 16%, compared to cows in a group experiencing a 12-hour day and 12-hour night.

The ideal is to achieve a long day photo period (LDPP), which replicates a typical spring day. “It is this ‘long day’ that increases milk yield,” says Mr Hooson. “This is because daylight affects cows’ hormonal levels, particularly melatonin.”

Melatonin is a sleep hormone that is produced in response to darkness, and it can interfere with the production of other hormones involved in milk production. “Exposing cows to extended daylight hours can suppress melatonin production, and this leads to higher levels of other hormones, such as prolactin, which stimulates milk production. Conversely, where days are short or light levels are low milk production is reduced.”

Mr Hooson has been measuring the quality of dairy cow lighting during the past 12 months in dairy housing across the UK and says there are many opportunities to achieve marginal gains by optimising lighting. The target is to achieve daylight equivalents of 200 lux. “I compared the results for 43 milking-cow sheds on 10 units. The average showed a minimum lux level of 34 between lights and 154 lux directly beneath the lights.

“Despite most producers thinking cow-house lighting was adequate on their units, overall it was poor, and the ‘consistency’ of lighting was also an issue, which meant there were opportunities to increase production by correcting these problems,” says Mr Hooson.

Darker period

“While we need to target the LDPP at 200 lux, milking cows must have a darker period of between six and eight hours in every 24-hour period. If lights cannot be turned off completely, consider dimming them from 200 lux down to between 30 and 50 lux. There are some simple timers and lux level switches on the market that will allow this process to be easily automated.”

Mr Hooson adds that, on many units, lighting configurations have been developed in an uncoordinated way without due consideration to overall light levels. “Using a lighting plan ensures a consistent 200 lux of light is being achieved across each shed with no bright spots and no dark patches.” He stresses that lights must be correctly positioned and not just suspended from convenient structures. “A common mistake I see is a 150 to 200W spotlight being mounted too low, which concentrates the light in a small area and disrupts overall lighting.”

Light colour is also important and often overlooked. “With any artificial lighting system the objective is to mimic sunlight, which contains a high proportion of light in the blue part of the spectrum.

“This part of the spectrum is important as it is the most effective at suppressing melatonin,” explains Mr Hooson. “While some artificial lights contain sufficient blue others do not. Sodium lights, for example, and some LEDs contain little blue light. So producers should only purchase lights containing sufficient blue light, in the 460-to-480nm range. Off-the-shelf factory lights are for factories – not cows.”

The quickest way to determine how much the lighting is affecting performance and to identify where improvements can be made is to carry out a lighting survey, which measures lux and light spectrum levels. He says funding may be available to do this, free of charge, in England and Wales.

“Using spectrometer readings for each of the main livestock areas, the survey will review minimum and maximum lux readings as well as testing sufficiency of blue light. Readings are taken after sunset, so are for artificial lights only.

“Using the report, it is possible to plan changes to the lighting system covering total light levels, colour spectrum and timing to allow a more effective configuration to be installed,” adds Mr Hooson. “Automation can simplify how the system is controlled and help reduce overall running costs, including switches with integrated light meters.

Winter lighting

While milking cows need longer and lighter days, he says dry cows need exactly the opposite. “The first rule is not to light dry-cow housing. We need dry cows to rest and have a ‘long night’, so natural winter lighting is perfect for them.

"By all means have an inspection light, but this only needs to be between five and 50 lux maximum. A good dry-cow rest period has been proven to lift milking yields by more than three litres per day compared to a control group, so reducing dry-cow lighting should be a priority and will also save on running costs.

“The return on investment, which is influenced by how long cows are housed, is typically around 12 months for all-year-round housed systems. These cows benefit most from improved lighting and will also see the greatest return on investment.”

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