BREED-DEPENDENT AND GENDER-DEPENDENT DIFFERENCES IN EYE GROWTH AND FORM DEPRIVATION RESPONSES IN CHICK

This study investigated the influences of breed and gender on the resp onse to form deprivation and subsequent changes (recovery) when normal vision was restored. Two breeds of chickens, the White Leghorn and br oiler cross, were compared, as well as male and female chicks for the White Leghorn breed. Normal eye growth was faster in the more rapidly growing broiler chicks; gender-differences were not as great as breed- differences although male White Leghorns ultimately became heavier and showed slightly greater normal eye growth than females. While both br eeds showed high myopia and axial elongation in response to form depri vation, they differed significantly in the magnitude of their response , with White Leghorns showing more myopia and greater axial elongation and also recovering more slowly. Responses to form deprivation were s imilar for both genders, with respect to both the amount of myopia and axial elongation produced, although the female chicks recovered faste r. Together these observations indicate that, although the overall pat tern of response of form deprivation is consistent across both breed a nd gender, related quantitative differences in responses can be expect ed and need to be taken into account in experimental design and cross- study comparisons.