Photoperiodic lighting (16 hours of light:8 hours of dark) programs during incubation: 1. Effects on growth and circadian physiological traits of embryos and early stress response of broiler chickens

📖 Top 20% JournalOct 24, 2012Poultry science

Long Daylight Exposure During Incubation Affects Growth, Body Clocks, and Early Stress in Broiler Chickens

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Abstract

Embryos incubated under a 16L:8D photoperiod for the entire incubation period exhibited a daily rhythm of melatonin at internal pipping and hatching.

Incubation in darkness did not produce a daily rhythm of melatonin in embryos.
The group with light exposure during the last week of incubation had rhythmic plasma melatonin only at hatching.
A lower increase in blood corticosterone level was observed in embryos incubated under light for the entire period compared to those hatched in darkness.
No significant differences in brain malondialdehyde concentration were found across incubation lighting conditions.
Increased breast muscle weight was noted at hatching in embryos exposed to light during the last week.
Overall, photoperiodic lighting during incubation may enhance chick adaptation to the posthatching environment.

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This study was conducted to evaluate the effect of a 16L:8D photoperiod during incubation, either during the whole incubation period (Inc(0-21d)) or the last week of incubation (Inc(14-21d)), on embryo growth, incubation performance, and light:dark rhythm of plasma melatonin and corticosterone in relation to early stress responses of newly hatched chicks to the posthatching environment. A dark incubation condition (Inc(Dark)) served as control. Three batches of eggs (n = 1,080, 1,320, 720) from Ross 308 broiler breeders were used in the experiment. Embryos from Inc(0-21d) presented a daily rhythm of melatonin at internal pipping and hatching, but Inc(Dark) embryos did not. The Inc(14-21d) group had rhythmic plasma melatonin at hatching only. A L:D rhythm of corticosterone was apparent at hatching. A significant incubation × sampling time interaction suggested that a lower increment in blood corticosterone level in Inc(0-21d) at 8 h posthatching (light period), as compared with hatching (dark period) values, might be associated with probable changes in the hypothalamic-pituitary-adrenal axis in Inc(0-21d) through incubation lighting. This finding may also suggest improved adaptation to the posthatching environment. Incubation lighting did not consistently affect brain malondialdehyde concentration; the only difference between groups was higher concentrations at hatching in Inc(14-21d), whereas incubation groups at the internal pipping stage had similar values. Mean relative asymmetry (RA) did not differ with incubation lighting. The malondialdehyde and RA results indicate that neither lighting nor darkness during the overall incubation exacerbated embryo oxidative and developmental stress. An increased breast muscle weight was observed at hatching only in Inc(14-21d). The Inc(0-21d) group had increased embryo weights relative to egg weight and decreased residual yolk but had no effect on chick weight, relative heart and liver (% of embryo weight), hatchability, embryo mortality, incubation time, oxidative stress, or mean RA. In conclusion, these results provide further evidence that photoperiodic lighting during incubation (Inc(0-21d)) may improve adaptation of chicks to a novel environment at hatching, possibly giving birds a better start for early posthatching development.

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