Luminaires and livestock: lighting a livestock building properly

In a livestock building, light is not a matter of working comfort: it acts on the animals' biological rhythm, their feed intake and their reproduction, while determining the work of the farmers in rooms that are often windowless, humid and hosed down. Designing it means dealing with two subjects at once: a zootechnical subject, specific to each species, and an equipment subject, the resistance of the luminaire in a corrosive atmosphere. This article covers cattle, pigs, sheep and horses; the poultry sector, which has its own lighting programmes, is the subject of a dedicated article on LED poultry lighting.

Photoperiod, the first lever of livestock lighting

In farmed mammals, the daily duration of lighting drives the secretion of melatonin, a hormone produced during the dark phase. Lengthening the light day reduces this secretion and alters the animal's hormonal balance. It is this mechanism, and not intensity alone, that explains most of the effects observed in production. The installation must therefore be programmable, and the dark phase counts as much as the lit phase: a building lit all night by poorly placed night lights will not give the expected results.

Dairy cattle: 16 hours of light, 8 hours of darkness

This is the best-documented application. Reference work on dairy barns converges on 16 to 18 hours of lighting followed by 6 to 8 hours of darkness, at a level of around 100 to 200 lux measured at the animals' eye level, and not on the floor. The reported gains in milk production are between 5 and 16 %, an average often quoted around 8 %, with an increase in feed intake of around 6 %, effects that set in within three to four weeks. The reasoning is reversed for dry cows, for which a short photoperiod, around 8 hours, is associated with a better following lactation; heifers, on the contrary, benefit from long days from weaning to puberty. The same building therefore often has to manage several programmes, hence the value of dividing it into independently controlled zones.

The milking parlour is also a workstation

On the animal side, abrupt contrasts between the holding area and the platform must be avoided, as they slow the cows' entry. On the human side, the milker must assess the condition of the udder and the appearance of the milk, which requires a much higher level in the pit. The French Labour Code sets minimums for workrooms, recalled in the MSA guide to cattle buildings: 120 lux in a workroom, 200 lux in a permanently occupied windowless room, 40 lux in circulation areas. These are regulatory floors, not design targets. Our solutions are in the LED lighting for cattle farms range.

Pigs: 40 lux and 8 hours, a regulatory obligation

Pig farming is the only one, among the species covered here, to have a figure that is legally enforceable. Directive 2008/120/EC, transposed by the French order of 16 January 2003, provides that pigs must be exposed to light with an intensity of at least 40 lux for a minimum of eight hours a day, in natural, artificial or mixed light, for all categories of animals.

The threshold is assessed at the level of the animals, including in the least well served pens: it is uniformity that determines compliance, not the average. The needs of the operators exceed those of the animals, particularly for health monitoring; as pigs tolerate marked contrasts poorly, a uniform base level supplemented by localised reinforced zones is better than oversized general lighting. See the range dedicated to pig farms.

Sheep and goats: light as a tool for out-of-season breeding

In small ruminants, lighting is used first of all to shift the breeding season: a phase of artificial long days is followed by a return to short days, the change in photoperiod triggering the resumption of sexual activity. Protocols in the sheep sector set 16 to 18 hours of lighting during long days, with a minimum of around 200 lux at the ewes' eye level, as documented by the Inn'Ovin field report. The difficulty lies in uniformity over long, low sheep houses cluttered with hay racks: a lack of uniformity deprives part of the flock of the planned dose and renders the protocol ineffective.

Horses: seeing without dazzling

The horse has vision adapted to low light but adapts slowly to changes in intensity. In an indoor arena as in a stable, the issue is not the raw level but the control of glare and shadow areas: a luminaire visible in the rider's field of view, or alternating light and dark bands on the track, is enough to cause refusals. The principles are close to those of sports lighting: sources out of the direct field of view, careful uniformity right into the corners. For competition arenas and outdoor schooling areas, the EN 12193 standard adjusts the requirements according to the level of practice. In stables, a soft light without bright spots is preferred, with luminaires out of reach and impact-resistant. Our selection for equestrian centres meets these constraints.

Animals do not see what you see

Cattle, pigs and horses are dichromats: they have only two types of cones, against three in humans. In cattle, sensitivity peaks are around 450 nm in the blue and 555 nm in the green. Perception of red is weak, which is sometimes used to light circulation areas at night without interrupting the dark phase: a practice to be validated species by species. Above all, remember that a colour temperature in kelvins says nothing about the spectrum emitted: two luminaires stated at 4000 K can have different effects on the animal.

Flicker is a second difference in perception: several species perceive rapid variations in flux that the human eye no longer detects. A low-end driver or poorly implemented dimming then generates stress that the farmer cannot see. Ask for the flicker values, some products showing a Pst LM indicator below 1.0, and check the compatibility of luminaire and dimmer before ordering.

Dawn and dusk dimming: the transition counts as much as the level

An abrupt change from darkness to full lighting causes panic movements, crushing and injuries, whatever the species. Gradual simulation of dawn and dusk, over several minutes, gives the animals time to move calmly to their resting area or their trough. This is an established practice in poultry management that carries over to other sectors, particularly where milking robots maintain permanent circulation. A consistent chain is still needed: a luminaire dimmable over the whole useful range, a suitable driver, reliable controls, preferably on a standardised bus as detailed in our article on DALI and KNX control systems. A point often neglected: deep dimming, below 10 %, is the range where flicker defects appear.

Withstanding the building: washing, ammonia, humidity

Washability and ingress protection rating

Between two batches, the building is washed with a high-pressure jet, sometimes with hot water and alkaline detergents. IP66 guarantees dust-tightness and resistance to powerful jets. The IP69K rating goes further: the test, described by the DIN 40050-9 standard and then taken up by ISO 20653, subjects the luminaire to a jet of 80 to 100 bar, with water at 80 °C, nozzle at 10 to 15 cm, at four successive angles of 0, 30, 60 and 90 degrees. This is the relevant level wherever cleaning is done with hot high-pressure water.

Ammonia and corrosive gases

The air in a livestock building is laden with ammonia from manure, to which hydrogen sulphide and organic dust are added depending on the case. These compounds attack seals, varnishes, aluminium alloys and above all copper connectors. A lighting failure in a livestock building rarely comes from the LED: it comes from the electronics or corroded cable entries. To check: materials, stainless steel screws, quality of the seals, a balancing valve limiting condensation, a documented ammonia resistance test.

Electrical safety in a humid environment

Premises housing livestock fall under part 705 of the NF C 15-100 standard, whose scope explicitly covers stables, cowsheds, poultry houses and piggeries. As animals are more sensitive than humans to touch voltages, these requirements reinforce protection: supplementary equipotential bonding connecting the conductive parts accessible to the animals, suitable residual current protection, choice of equipment according to the atmosphere. The MSA guide recalls the use of a 30 mA residual current device in the humid and corrosive atmospheres of milking. On this aspect, the regulations in force and validation by the installer take precedence.

Why sealed tubular luminaires are the answer in livestock buildings

The tubular shape is not aesthetic but functional: a smooth, closed tube offers no recess where dust and manure accumulate, rinses clean in one pass and matches the geometry of a long, narrow building.

The REXSHOCK TUBULAR IP range was designed for these atmospheres: IP69K in the PMMA version or IP67 in polycarbonate, IK10, 130 to 150 lm/W, 20 to 60 W for 2,600 to 9,000 lm, 316L stainless steel accessories, anti-condensation depressurisation valve, stated resistance to ammonia and sulphurous vapours, lifetime of 54,000 hours at L90. To renovate existing sealed luminaires, the REXTUB GLASS T8 tube offers 160 lm/W, a 320-degree beam and flicker-free operation, to be found in lamps and tubes. The whole range is in our livestock section.

Benchmark figures by species

| Situation | Illuminance | Duration | Status |

| --- | --- | --- | --- |

| Lactating cows | 100 to 200 lux at eye level | 16 to 18 h of light | Zootechnical |

| Dry cows | Short photoperiod | About 8 h of light | Zootechnical |

| Pigs, all categories | 40 lux minimum | 8 h minimum per day | Regulatory |

| Ewes, out-of-season breeding | 200 lux minimum at eye level | 16 to 18 h in long days | Sector protocol |

| Windowless workroom | 200 lux | During occupation | Labour Code |

These values are starting points, not a sizing: only a calculation based on the actual geometry of the building, with heights, obstacles, reflections and maintenance factor, is authoritative. That is the purpose of the photometric study before purchase, equally valid for other demanding agricultural buildings such as wine cellars.

Frequently asked questions

What ingress protection rating should be chosen for a livestock building?

IP66 is the acceptable minimum when pressure washing is used. As soon as cleaning is done with hot high-pressure water, which is common in pig farming and in milking parlours, aim for IP69K. If the luminaire may be immersed, add an IP67 or IP68 requirement, which IP69K does not cover.

Is dimmable lighting mandatory in livestock buildings?

It is not a regulatory obligation, but it is what makes it possible to take advantage of the photoperiod without abrupt transitions. Without dimming, only fixed times remain, with instant switch-ons that generate stress. It becomes essential as soon as a building manages several batches or physiological stages.

Is the illuminance level measured on the floor?

No. Zootechnical and regulatory thresholds are assessed at the animals' eye level, a height that varies greatly with the species. A measurement on the floor, or directly under a luminaire, can suggest compliance that does not exist in the least favoured areas.

Can an LED renovation be limited to changing the tubes?

Yes, if the existing luminaires are sealed, in good condition and correctly positioned. If the housings are corroded, the seals aged or the layout insufficient for the uniformity sought, complete replacement is necessary. A prior audit makes it possible to decide objectively.

Designing your installation with a design office

Successful livestock lighting combines a lighting programme suited to the species and the physiological stage, uniformity verified by calculation and equipment sized for ammonia and high-pressure washing. These three aspects are validated before purchase, not after installation.

Get in touch with our technical partner, the Luminance-Consulting agency, a lighting solutions consultancy since 2013. Audit of the existing installation, photometric study in DIALux and support through to acceptance: 1 Route de Bartres, 65100 Adé. For a cost estimate of Rexylum equipment, request your quotation.