A comparison of the effects of feeding treatments and lighting on age at first egg and subsequent laying performance and carcase composition of broiler breeder hens

Abstract

The effects of the growth curve from 15 to 20 weeks, age at photostimulation and pattern of photostimulus on sexual maturity, egg production and egg weight were evaluated in two trials with broiler breeder females to 56 and 34 weeks of age (housed in litter pens and individually caged, respectively). Carcase composition and reproductive morphology of hens varying in laying efficiency were measured in the second trial. Trial 1: Four growth curves were applied from 15 to 20 weeks to pullets housed in litter pens. Birds were transferred from 8- to 10-h photoperiods at 20 or 24 weeks of age, followed by weekly increments of one hour to reach a 16-h final photoperiod. Lower-than-recommended body weights at 20 weeks significantly delayed sexual maturity, reduced peak rate of lay, total eggs and mean egg weight. However, double-yolked egg production was lower, resulting in non-significant differences in settable egg numbers between body weight treatments. Birds reared to the heaviest body weight exhibited a significantly advanced sexual maturity, but total egg numbers, peak rate of lay and mean egg weight were not significantly affected. However, the laying of more double-yolked eggs resulted in a decrease in the number of settable eggs. Delaying photostimulation to 24 weeks significantly retarded sexual maturity, reduced total and settable egg numbers, and increased mean egg weight. A tendency for fewer double-yolked eggs was observed. Trial 2: At 19 weeks, birds were selected from the 4 body weight categories in Trial 1 and moved to individual cages in 8 rooms. Five lighting programmes were applied. The pattern of photostimulation applied did not affect any of the production traits measured. At 34 weeks, 24 birds were selected for the analysis of reproductive morphology, presence of internal or multiple ovulations, and carcase composition. Eight hens showing an early age at first egg and regular egg production records, 8 birds showing erratic laying performance and 8 non-layers were killed for this purpose. There were no differences in carcase composition or reproductive morphology between these groups. No internal ovulations or double or multiple ovarian hierarchies were observed. The results presented confirm that broiler breeders do not require a lighting stimulus in order to initiate ovarian activity and that, where no lighting stimulus is given, body weight or feeding level plays a critical role in stimulating the birds to attain sexual maturity. However, when a lighting stimulus is given, factors such as body weight and body composition become relatively less important in regulating the age at sexual maturity.

Early photostimulation at the recommended body weight reduced broiler breeder performance

“…The maturation interval for the 21WK treatment in the current study is comparable to these results, but the maturation interval of the 18WK treatment is much larger. Previously, hypotheses were proposed that the rate of sexual maturation after photostimulation increases, when photostimulation occurred later, such that for every day that photostimulation was delayed, AFE was delayed between 0.21 and 0.40 d (Yuan et al, 1994 ; Robinson et al, 1996 ; Renema et al, 2001b ; Joseph et al, 2002 ; Ciacciariello and Gous, 2005 ; Pishnamazi et al, 2014 ). However, in the current study, AFE was advanced by 19 d when photostimulation was delayed by 21 d, resulting in an advance of 0.90 d for every day that photostimulation was delayed.…”

Modelling egg production and nutrient responses in broiler breeder hens

“…02 and 0 . 04 of all eggs laid between 25 and 60 weeks and Ciacciariello & Gous (2005) reported a rate of approximately 0 . 04 from 23 to 56 weeks.…”

Genetic effects of polymorphisms in candidate genes and the QTL region on chicken age at first egg

“…Although environmental factors such as body weight, body composition as well as age are critical for the onset of sexual maturity [1-4], but the trait is also determined by its genetic components. Studies of human showed that 50%-80% of the variation in pubertal timing is determined by genetic factors [5,6].…”