Pinealectomy and Light Environment Effects on Testicular and Comb Development in the 46-Day-Old Broiler Cockerel

Abstract

Four replicate experiments were conducted to determine the effects of pinealectomy and environmental lighting on testes and comb weights in the broiler cockerel. Birds were housed in brooder batteries under a 14L:10D fluorescent white light regime for 2 weeks and then allotted to light-controlled chambers. Surgery was performed when the chicks were 3 to 5 days old. The fluorescent light treatments were 14L:10D green (narrow-band, 545 nm peak), 14L:10D cool white, and constant darkness. At the end of the 46-day experimental period, testes weights were determined and comb weight recorded. Pinealectomy did not affect testes weights or comb development. Darkness significantly (P less than .05) depressed testes and comb weight. This suggests that lack of light, but not pinealectomy, affects circulating hormone levels and/or tissue responsiveness in the young cockerel.

Identification of molecular pathways and candidate genes associated with cocks’ comb size trait by genome-wide transcriptome analysis

“…Comb size is a complex trait affected by many factors, including hormone concentration 8 , 9 and light schedule 10 , 11 . Capons with significantly reduced testosterone levels have small combs 12 .…”