Spontaneous steatosis stimulation in geese induces liver fattening but impacts sexual maturation and muscle growth in a sex-dependent manner

Experimental mimicry of premigratory environmental conditions results in a transient corn hyperphagia associated with a spontaneous liver steatosis in male Greylag geese. Our study aimed to i/ determine the feasibility of the induction of a spontaneous steatosis in female geese and ii/ evaluate its reversibility. Six-week-old Greylag Landaise geese (Anser anser) were randomly assigned to a control group (40 males and 41 females) or a spontaneous fattening group (SF; 118 males and 122 females) separating the sexes. Controls were fed a grower diet and exposed to a 10 h daylight cycle throughout the experiment. SF birds were exposed to a progressive reduction in day length from 10 to 7 h/day and submitted to a quantitative feed restriction with a grower diet between 8 and 19 weeks of age, followed by an ad libitum corn feeding period until 31 weeks of age, after which the grower diet was provided again until 33 weeks of age to study the reversibility of steatosis. Ten Control and 30 SF birds per sex were slaughtered at 31 and 33 weeks of age to evaluate liver fattening. Female SF geese had a lower feed intake during the second part of the corn feeding period (25-31 weeks of age, P < 0.05), but had equivalent aptitudes to develop a spontaneous steatosis (liver weight and lipid content, P > 0.05), than male SF geese. However, breast muscle growth was penalised in females (P < 0.05). Compared to controls, sexual maturation was strongly hindered in both SF males and females (gonad weight, P < 0.05). Regarding reversibility, in males, SF birds had equivalent liver weights to controls at 33 weeks of age while liver lipid content remained higher (P < 0.05). As control females initiated a steatosis, conclusions on reversibility in that sex were difficult to make. Finally, mortality occurred at the end of the corn feeding period in both sexes in SF birds. Our study enabled us to demonstrate that male and female geese had equivalent aptitudes to develop a spontaneous steatosis, associated with a lower feed intake in females. However, coupled with the protein-deficient composition of the corn-based diet, this lower feed intake could lead to exacerbated protein deficiencies in females, evidenced by a penalised muscle growth in these animals. Reversibility of spontaneous steatosis and mechanisms underlying its onset should be further explored in order to preserve the bird's health and welfare.