Why do young brown layers at the peak of lay produce more double-yolk eggs than older, late-phase hens?

Ovulation in commercial brown layers is controlled by the hypothalamic-pituitary-ovarian axis. At the onset of lay (18 to 24 weeks of age), young pullets experience a massive, sudden surge of reproductive hormones (specifically follicle-stimulating hormone, FSH, and luteinizing hormone, LH) stimulated by increasing day-length. Because their endocrine feedback loop is highly active and not yet fully synchronized, the ovary occasionally develops and ovulates two follicles (yolks) simultaneously or within a very short 2-to-3-hour window. Both yolks enter the infundibulum and travel down the oviduct together, receiving a single shell. As the flock ages and reaches peak lay (around 30 weeks), their hormonal secretion stabilizes into a highly regulated, 24-to-26-hour rhythmic cycle, making double ovulation extremely rare. Farmers can study reproductive endocrinology in the Poultry Encyclopedia, buy nutritional hormone-stabilizing feeds on Poultry Plaza, monitor daily prices on Poultry Rates, and trade on Murghi Mandi.