Takao Oka

A genetically female brain is required for a regular reproductive cycle in chicken brain chimeras

Sexual differentiation leads to structural and behavioural differences between males and females. Here we investigate the intrinsic sex identity of the brain by constructing chicken chimeras in which the brain primordium is switched between male and female identities before gonadal development. We find that the female chimeras with male brains display delayed sexual maturation and irregular oviposition cycles, although their behaviour, plasma concentrations of sex steroids and luteinizing hormone levels are normal. The male chimeras with female brains show phenotypes similar to typical cocks. In the perinatal period, oestrogen concentrations in the genetically male brain are higher than those in the genetically female brain. Our study demonstrates that male brain cells retain male sex identity and do not differentiate into female cells to drive the normal oestrous cycle, even when situated in the female hormonal milieu. This is clear evidence for a sex-specific feature that develops independent of gonadal steroids.

Effect of Supplemental Japanese Pepper Seed on the Palatability of Feed in Chicks

The present study aimed to establish whether supplemental Japanese pepper seed (JPS) affects feed intake in broiler chicks under ad libitum conditions. Experiments were designed to estimate the acute effect of JPS on feed and water intake using 5%–20% JPS supplemental feeds. JPS supplemental feed demonstrated a tendency to suppress feed intake and water intake in a dose-dependent manner during the 2 h post-feeding period, and chicks seldom ate 20% JPS supplemental feed at 1 h post-feeding. No significant difference was observed in the rectal temperature between groups during the 2 h post-feeding period. In a 5-h feeding experiment, no JPS level had any effect on feed or water intake in chicks. These data suggest that the adverse effect of JPS may be due to volatile stimulation; however, the effect disappears after 5 h post-feeding.