Effects of Maternal Omega-3 Supplementation, Sex, and Strain on Chick Behaviour During Social Isolation

Omega-3 fatty acids transferred from breeder hens to their developing offspring via the egg may affect the offspring’s emotional reactivity and fearfulness. In one experiment, broiler (meat) parent flocks were fed flaxseed or control diets during rearing, laying, or both. In a second experiment, ISA Brown and Shaver White layer (egg) parent flocks were fed flaxseed or control diets throughout rearing and laying. Male and female broiler offspring and female layer offspring underwent a five-minute social isolation test at 4–6 days of age. Vocalisations, escape attempts, and freezing (immobility) durations were recorded. In the broiler experiment, maternal laying diet and sex interacted to affect vocalisation frequency (χ2 = 5.57, p = 0.02). Male broiler chicks from the flaxseed maternal laying diet vocalised most frequently (p < 0.04). An interaction between the rearing diet, laying diet, and sex affected escape attempts in broiler offspring (χ2 = 6.03, p = 0.01). Control-control males made the fewest escape attempts. In the layer experiment, no maternal diet effects were observed in any offspring, but Brown chicks vocalised substantially more than White chicks (χ2 = 4.56, p = 0.03), and White chicks spent more time frozen (χ2 = 5.86, p = 0.02). We found sex-specific effects of maternal flaxseed diets on measures of anxiety and fear of broiler chickens in social isolation. Genetic strain-dependent effects in layer chickens suggest differing behavioural responses to isolation.