Pituitary weight and gonadotrophin concentration, body weight and ovarian weight in growing and mature female Turkeys exposed to different light regimens

Synopsis

Anterior pituitary weights and gonado‐trophin concentration, body weight changes and ovarian weights were followed every two weeks in three lighting treatment periods in spring hatched turkeys. In the growing period (12 to 20 weeks of age), all of the characters changed with the increasing age of the birds while no changes were associated with the lighting treatments (either 14 hr of light daily or natural daylight). During the conditioning period (20 to 28 weeks) anterior pituitary weight, body weight change and ovarian weight all increased with increasing age. No changes were found in anterior pituitary gonadotrophin concentration. Body weight change and ovarian weight were also greater in birds maintained on range as compared with birds treated with 6 or 14 hr of light daily. In the production period (28 to 40 weeks), the birds were divided into laying and non‐laying groups. In the laying group, no differences were found in the three characters studied (ovarian weight not included) within the ages studied. In the non‐laying group, the birds on range had greater body weight increases within the 34th to 38th week than the birds on the other lighting treatments. More of the birds given 6 hr of light during the conditioning period were classified as layers in the production period than birds treated with either 14 hr or natural light (14.3 decreasing to 11.5 hr) during the conditioning period. Once a bird had started laying, a decided drop in anterior pituitary gonadotrophin occurred.