. 2021 Jul 16;8:678500. doi: 10.3389/fvets.2021.678500

Table 1.

Examples of environmental effects on parents, their eggs, and their offspring in chickens.

Parental treatment	Type of bird, age at treatment and duration	Effects on the parents	Effects on the eggs	Effects on yolk-hormone levels	Effects on development, behaviour and physiology of the offspring	Epigenetic effects	References
Food restriction	Broiler breeder ♀ 60–65 woa for 6 wks	≈ Fertility	N.D.	N.D.	≈ Hatchability ↑ Hatch window ↓ Hatch weight, ↓ naval quality^♀ ≈ BW, tibia length, % left ventricular weight ≈ Ascites incidence to 6 woa ↑ Abdominal fat^♀ ^{adlibitumfeed} at 6 woa	N.D.	(1)
Diet high omega 3:6 ratio vs. high omega 6:3 ratio	WL ♀ adult for 6 wks	↑ FCM ≈ Food intake ≈ BW ≈ Laying rate	↓ Egg mass ↓ Yolk mass	↑ P ↑ A4 ↑ E2	↓ BW at hatch ≈ Growth rate to 1 woa ≈ Food neophobia at 4-5 doa ↑ Latency to eat, ↓ time eating at novel feeder at 6 doa	N.D.	(2)
Unpredictable access to food	WL♀♂ 26 woa for 11 d	↑ FCM ≈ BW	N.D.	≈ CORT	≈ BW at hatch ≈ Growth rate ↑ TI at 22 woa ↓ Food competition at 23 woa	N.D.	(3)
Unpredictable light-dark rhythm	WL, RJF ♀♂ 35–260 doa	↓ Spatial learning	N.D.	≈ CORT	↑ BW at hatch^RJF ↑ Growth rate to 8 doa ↑ Food competition at 21 doa ↓ Slower spatial learning^WL at 33 doa	Corr: Brain gene expr. parents and offspring	(4)
Unpredictable light-dark rhythm	WL ♀♂ 26 doa - adult	↑ Foraging pecks ↑ Pref. easy-found food ↑ Growth young^♀ ≈ Food competition	N.D.	↑ E2 ≈ CORT ≈ A4 ≈ T ≈ DHT	↑ Pref. easily-found food at 55–57 doa ^♀ ↑ Pref. high-energy food at 216 doa ↑ Food competition at 189 doa ≈ Food competition at 22 doa ↑ BW gain 66–105 doa ↑ Survival to 40 woa	Corr: Brain gene expr. parents and offspring	(5)
Moderately high ambient temp	WL ♀ 22–27 woa	↑ Body temp. ≈ CORT ≈ Feed intake ≈ TI ≈ Laying rate	↓ Egg mass ≈ % Yolk mass	↑ P ↑ T ↑ E2 ≈ CORT ≈ A4	↑ Chick quality score at hatch ↓ BW 0-20 doa ≈ Body temp. at 0 and 6 doa ≈ Feed intake to 3, 11, and 17 doa ↓ Pref. high-energy food at 10 doa ↓ Pref. sucrose solution at 21–22 doa ↓ Distress calls - novel food at 12 doa ≈ Latency to eat novel food at 12 doa ≈ TI at 7 doa ≈ Open field behaviour at 23–24 doa ≈ Adult hen BW and laying rate	N.D.	(6)
Unpredictable human movement, rough handling vs. predictable human movement, gentle handling	WL ♀ Adult for 5 wks	↓ Fertility ↓ Prox. to human ↑ Vigilance ↓ Feeding ↓ Exploring ↓ Resting ≈ FCM ≈ BW ≈ Laying rate	≈ Egg mass ≈ Egg comp	↓ P ↓ E2 ≈ A4 ≈ T	≈ Hatchability, BW hatch ≈ Pref. familiar vs. unfamiliar chicks at 20 doa ≈ Fear of human hand at 3 doa ≈ Fear of novel food at 8–9 doa ≈ Fear of NO at 8–9 doa ≈ Detour test behaviour at 10 doa ≈ Open field behaviour at 15–16 doa ≈ Social discrimination at 19 doa ≈ Social reinst. at 20 doa	N.D.	(7)
CORT implant	WL ♀ ISA Brown ♀ 33 woa Egg collection for 20 days	↑ CORT ↓ P, T, E2^WL ↓ Laying rate^WL	↓ Egg mass ↓ Yolk mass ↓ Alb. mass + shell mass	↓ P ↓T ≈ E2	≈ Hatchability and sex ratio ↓ BW at hatch catch-up by 4 woa ↓ Food competition at 9 doa ≈ Time near NO at 11 doa ↓ Visual lat. with NO at 11 doa ≈ Open field behaviour at 14 doa ↓ TI at 28 doa and 24 woa ≈ CORT restraint at 10 woa ↑ Baseline T at 12 woa ≈ Baseline T at 24 woa ↓ Immune response at 12 woa	N.D.	(8)
On-farm variation: tests and analysis conducted on flock level/flock averages	Dekalb White ♀♂ ISA Brown ♀♂ 40 woa	Corr. ↑ fear NO ^↓ BW, egg mass ^ feed intake^DW, ↑ Fear human ^*↑ Mortality^ISA	Corr: ↑ CORT ^* ↓ egg mass	N.D.	Corr⁺ ↑ CORT ^↑ SFP at 1 woa^DW ↑ 5-HT ^↑ SFP at 1 woa^DW ↑ F score ^↑ SFP at 1 woa^DW ↑ 5-HT ^↑ distress calls at 1 woa ↑ F score ^↑ distress calls at 1 woa ↑ F score ^↑ distress calls at 5 woa^DW N.A. parent stock ^* fear offspring N.A. parent stock ^* GFP offspring N.A. parent stock ^* feather damage N.A. parent stock ^* CORT or 5-HT	N.D.	(9)
Unpredictable stressors: isolation, cold ambient temperature, feed/water deprivation and handling	WL ♀♂ Daily during 4-26 doa	↑ BW adult^♀ ↑ Assoc. learning^♀ at 50–51 doa ↓ CORT restraint ≈ T^♂ ≈ E2^♀	↑ Egg mass^3of12d	↑ T ↑ E2^1of3d	↑ BW^♂ at 56 & 74 doa ↓ BW^♀ at 2 doa and ↑ BW at 74 doa ≈ Open field behaviour at 33–34 doa ≈ Social reinst. at 39-40 doa ≈ TI at 46-47 doa ↑ Assoc. learning response at 51-52 doa ≈ Correct assoc. learning at 51-52 doa ↓ CORT restraint^♂	Corr⁺: Thalamus gene expr. parents and offspring	(10)
Repeated food frustration, restraint and social isolation	WL ♀♂ At 2 woa At 8 woa At 17 woa For 6 days	↓ Growth rate² ↓ Vigilance NO⁸ ↓ TI^{2, 8} ↑ CORT restraint at 29 woa⁸ ≈ Emerg. at 30 woa ≈ Rec. restraint ≈ TI at 31–32 woa	↑ Egg mass ^2>17andC	N.D.	↑ BW hatch^17vs.C ↑ BW at 4 woa^{8vs. 2} ≈ BW at 11 doa and 8 woa ≈ Open field behaviour at 11 doa ≈ TI at 18 doa ↑ Emerg. at 23–24 doa^17vs.C ↑ CORT restraint at 7 woa^8vs.C	Corr: Brain gene expr. parents^{2, 8, 17} and offspring at 7 woa	(11)
Unpredictable stressors: simulated predator, air horn, unfamiliar conspecific, restraint, crating, transport	5 strains adult ♀: Brown 1 and 2, White 1 and 2, WL Daily for 8 d at 32, 52, and 72 woa	↑ CORT (acute) ≈ Basal CORT	N.D.	N.D.	≈ Hatchability and sex ratio ↓ Late embryonic mortality^{Brown 2 and White 2} ≈ BW at 0–17 woa ↓ Distress calls at 5–10 doa^{White 2} ≈ TI at 9 woa ≈ CORT ≈ Fear responses	N.D.	(12)

5-HT, whole blood serotonin; A4, androstenedione; alb, albumen; assoc, associative; BW, body weight; C, control; comp, composition; CORT, plasma corticosterone; corr, correlation; corr+, positive correlation; DHT, 5-alpha-dihydrotestosterone; d, days; doa, days of age; DW, Dekalb White hybrid; E2, oestradiol, emerg., emergence test (latency to emerge); FCM, Faecal CORT metabolites; F score, feather score (feather damage); GFP, gentle feather pecking; ISA, ISA Brown; lat, lateralisation; N.A., no association; N.D., not determined; NO, novel object; P, progesterone; pref, preference; prox., proximity; RJF, Red Junglefowl; rec., recovery; reinst., reinstatement; expr., (gene) expression; SFP, severe feather pecking; T, testosterone, TI, tonic immobility duration; temp, temperature; WL, White Leghorn; woa, weeks of age.

Superscripts: effects found in a specific strain, sex, age, or treatment group.

↓ Lower; ↑ higher; ≈ similar; ♀ hens;

^♀

effect only in hens;

♂ cockerels;

^♂

effect only in cockerels;

with (e.g., association a*b).

1: van der Waaij et al. (51); 2: De Haas et al. (52); 3: Janczak et al. (53); 4: Lindqvist et al. (54); 5: Nätt et al. (55); 6: Bertin et al. (56); 7: Bertin et al. (57); 8: Henriksen et al. (58); Henriksen et al. (59); 9: de Haas et al. (60); de Haas et al. (28); 10: Goerlich et al. (61); 11: Ericsson et al. (62); 12: Peixoto et al. (63); Peixoto et al. (64).