Light, sound and air quality get presented at trade shows as three versions of the same idea: sensors, a controller, better chicks. They are nothing of the sort. One of them has thirty years of published trial work behind it, one is a monitoring technology being sold as a treatment, and one has been sitting in your machines since they were installed, quietly deciding hatchability while nobody measured it.
Key takeaways
- CO2 above 0.5 % in the setter during early incubation reduces hatchability, with the effect pronounced near 1 %.
- Green LED photostimulation trials use low intensity at eggshell level and intermittent cycles, precisely to avoid heating the eggs.
- Acoustic monitoring classifiers reported in 2025 reach around 94 to 95 % accuracy at identifying distress-related vocalisations.
- Any supplier claim you cannot trace to a study with a DOI should be treated as marketing until proven otherwise.
Light: the intervention with an actual body of trial data
Light during incubation is the one of the three with a substantial experimental literature, and it concerns a specific application: monochromatic green light delivered to the developing embryo, not general illumination of a plant room.
Published trials report that green LED stimulation during the later part of incubation, typically from around embryonic day 15 to 18 through to hatch, is associated with higher body weight and breast muscle mass at hatch and through the first days of life, with mechanisms traced to satellite cell proliferation and to raised plasma growth hormone and IGF-I. Other work using low intensity green light reports increases in embryo weight, chick length and hatchability.
Two details from those protocols matter more than the headline. Intensity is deliberately low, measured at eggshell level rather than at the lamp, and regimens are intermittent, commonly 15 minutes on and 15 minutes off, specifically because continuous illumination heats the eggs. In a machine where you are already fighting to hold eggshell temperature at 37.8 °C, an uncontrolled light source is a heat source first and a stimulus second.
The honest summary is that the effect is real in trial conditions, modest in size, and dependent on wavelength, intensity and timing being right. It is not a retrofit that improves a poorly run incubation programme.
Sound: listening is much further along than broadcasting
The commercially useful development in sound is not playing music to birds. It is using vocalisation as a continuous, non-invasive welfare signal, and the evidence base here has moved quickly.
Work published in 2025, including a machine learning framework in the journal Sensors, reports classifiers trained on acoustic features that distinguish stress-related vocalisations with accuracy in the region of 94 to 95 %. Distress calls have a recognisable signature, repetitive and high in energy, and a microphone samples the whole population rather than the handful of birds a camera happens to frame.
What this technology gives a hatchery or a rearing house is an alarm, not a diagnosis. It flags that something changed at three in the morning, which is precisely when nobody is there. Claims that broadcasting sound improves production are a different proposition altogether and rest on a much thinner evidence base; we would want to see the trial before paying for the speakers.
Air quality: the oldest lever, still the least measured
Carbon dioxide is the parameter that most repays a sensor, because the tolerance changes through incubation and almost no one tracks it continuously.
In the first days in the setter, tolerance is low: concentrations above 0.5 % reduce hatchability, and the effect becomes pronounced near 1 %. Work by Bruggeman and colleagues in 2006 showed that broiler embryos tolerate a gradual rise to around 1.5 % by day 4 held through to day 10, after which ventilation is generally managed back towards 0.4 %. In the hatcher the picture inverts again: once internal pipping begins, a controlled elevated CO2 concentration is associated with a narrower hatch window without a penalty in chick quality.
Ammonia belongs in the same discussion, less in the machines than in the chick holding room and in transport, where accumulated litter and poor air exchange put a measurable respiratory load on birds that have not yet drawn a proper breath. Effective ventilation reduces the concentration of harmful gases, which is unglamorous and remains the single most reliable statement in this whole field.
| Technology | Maturity | Reasonable expectation |
|---|---|---|
| CO2 monitoring and ventilation control | Mature, well documented | Recovers hatchability lost to a ventilation setting nobody had reviewed |
| Acoustic welfare monitoring | Emerging, strong recent results | An early alarm outside working hours, not a diagnosis |
| In-ovo green light stimulation | Experimental to early commercial | Modest gains in early growth, conditional on precise protocol |
| Broadcast sound or music | Weak evidence base | Nothing you should budget against |
How to read a supplier’s claim
Precision livestock farming, abbreviated to PLF, is the umbrella term for all of this, and it has reached the stage where the marketing runs ahead of the data. A workable filter takes about ten minutes per claim.
Ask for the study, not the brochure figure. A claim worth acting on comes with a citation you can look up on PubMed or Google Scholar and a DOI that resolves to a real paper. Then check three things in that paper: the species and age of the birds, the scale, and whether the comparison was against a properly run control or against a deliberately poor one. Percentage improvements quoted without any of that context are not results, they are advertising, and a figure that appears in a sales deck without a traceable source should not survive into your business case.
What we would install first, and what we would wait on
Given a fixed budget, we would spend it on measurement before stimulation. A CO2 sensor logging continuously in each setter and hatcher, cross-checked against eggshell temperature, tells you whether your existing machines are running at their real capability. That is usually where the recoverable hatchability sits, and it costs a fraction of any new system.
Acoustic monitoring comes next, because it covers the hours nobody does. In-ovo lighting is worth trialling on a controlled proportion of your sets, with a genuine control group, rather than adopting across a plant on the strength of published trial results obtained under conditions that may not resemble yours. Sequencing these decisions is really a question of what to modernise first and what it returns, and the order rarely matches the order the technologies arrive in.
Three questions worth settling before you sign
Can these systems replace hands-on inspection?
No. They shorten the delay between a problem starting and someone knowing about it. The inspection that follows is still done by a person, and the breakout that explains the result is still done by hand.
Does existing equipment need replacing to add sensors?
Usually not for air quality: standalone logging sensors work in most machines and give you the data before you commit to integrated control. Light stimulation is the case where retrofitting into an old setter is genuinely difficult, because placement and intensity at eggshell level are the whole protocol.
What is the most common implementation failure?
Data that nobody reads. A logger installed and then left unexamined for a season is a cost with no return, which is why we treat the review routine as part of the specification rather than something to organise afterwards.
Ventilation is also your energy bill
Every improvement in air exchange has a running cost attached, and the two decisions are usually taken by different people on different budgets. They are worth taking together.
Sources: Bruggeman et al., 2006, on carbon dioxide tolerance during incubation; published research on monochromatic green light photostimulation during incubation and post-hatch growth, indexed in PubMed; machine learning framework for acoustic poultry welfare monitoring, Sensors, 2025; technical guidance on setter and hatcher ventilation from incubation equipment manufacturers. Consulted August 2026.
Published previously, fully revised on 8 August 2026. This article is general technical guidance for hatchery professionals. Trial results cited were obtained under specific experimental conditions and are not performance guarantees for a commercial plant. Any change affecting bird health or welfare should be discussed with the veterinarian responsible for your site.