Social Environment Alters the Duration of Rapid Yolk Deposition in Eggs of Domestic Hens.

Abstract

AbstractThe social environment can drive female birds to alter their investment in reproduction in the form of greater incubation behavior, more parental care, and greater allocation of physiological mediators to yolks. However, less is known about how social variables impact the speed at which females grow ovarian follicles in preparation for ovulation. We hypothesized that the social environment would influence how long ovarian follicles remain in rapid yolk deposition before reaching the size necessary for ovulation. For 8 d, we tested the effects of three types of social interactions: no social engagement (control), engagement with the same four females (social group 1), or engagement with the same four females plus six randomly selected roosters (social group 2). Starting on day 5 of engagement, we collected eggs and measured egg and yolk masses and yolk diameters. Then we stained the yolks with potassium dichromate to quantify the number of days the ovarian follicle spent accumulating yolk. We compared the results of the treatment groups with those of the control hens that were kept in individual laying cages throughout the study. The number of eggs laid, the yolk mass, and the yolk diameter did not differ among any of the three groups, but hens exposed to both females and males produced yolks with significantly more rings than hens in the other groups. Thus, the presence of males appeared to lengthen the time it took for ovarian follicles to reach the size needed for ovulation but did not result in larger or heavier yolks.