Lighting in a hot climate: the programme week by week

Why light controls laying

The hen “reads” the length of the day. When days get shorter or stay short, her body keeps growing without preparing to lay. When days get longer, she receives the signal to start laying. The farmer uses this signal:

• During rearing, the day length decreases: the pullet grows, gains her weight and skeleton, without maturing too early.
• From 19 weeks, if the weight is reached, the day length increases step by step: laying starts.
• Throughout laying, the day length stays stable at 16 hours: it never decreases.

A pullet stimulated before reaching her weight lays too early, lays small eggs, and lasts less long. A hen whose light drops in full lay slows down, sometimes for weeks.

The hot-country lighting programme

This programme is designed for countries between 20° North and 20° South, where the day length changes little through the year. Ivory Coast is in this zone.

Source: Novogen (Novogen Brown management guide, 2024).

Read the table in two parts: up to 18 weeks, the light goes down from 22 hours to 12 hours; from 19 weeks, it goes back up in steps to 16 hours, and each step has its target weight.

In an open-sided house: natural daylight plus supplementary lighting

In an open-sided house, the sun lights the hens all day. The total day length is the natural daylight plus the supplementary lighting, switched on before sunrise or after sunset. In Ivory Coast, natural daylight stays close to 12 hours all year round: that is why, from 13 to 18 weeks, you can simply keep the natural day length from 14 weeks.

• Note the time of sunrise and sunset at the farm: it is the basis of your programme.
• During brooding, the long durations (22 h, 20 h, 18 h…) are obtained by lighting part of the night; this night lighting is then reduced week after week.
• For stimulation, supplementary lighting is added before sunrise or after sunset: for example, at 19 weeks, one more hour of lighting.
• To reach 16 hours with a day of about 12 hours, you therefore need about 4 hours of supplementary lighting, split between morning and evening.
• A timer avoids forgetting and times that change from one day to the next.

Lighting pitfalls

• Increasing too early: light added to a flock that has not reached its weight, or a brightly lit laying house when the pullets come from a short programme.
• Reducing during laying: power cut without backup, burnt-out bulb, timer out of adjustment, a guard who switches off earlier.
• Irregular light: times that change from one day to the next; the hen needs a fixed rhythm.
• Poorly spread light: dirty or widely spaced bulbs, dark corners; some hens receive less than the programme.

Each pitfall shows in the figures: a flock that comes into lay too early with small eggs, or laying that drops for no obvious reason. Before suspecting the feed or a disease, check the light.