Effects of age at photostimulation on reproductive efficiency and carcass characteristics. 2. Egg-type hens

Abstract

Increasing day length is the primary cue for the timing of sexual maturation in poultry. Typically, Single Comb White Leghorn (SCWL) pullets are reared under conditions of short days (8L:16D) until 18 wk of age. In this study, the effects of varying the age at photostimulation from 16, 18 or 20 wk of age were studied in terms of carcass composition at photostimulation and at sexual maturity, as well as reproductive performance.A flock of 1600 SCWL pullets (Shaver 288 strain) were housed in floor pens in light-tight facilities (8L:16D). All birds were provided with ad-libitum access to both feed and water. At 16 wk, 18 wk and 20 wk, 50 birds per treatment were moved to laying cages and provided to a photoperiod of 14L: 10D. An additional 288 birds per treatment were housed two birds per cage, and group egg production and feed consumption data were collected to 64 wk of age. At photostimulation (n = 20 birds per treatment) and on the day following the first oviposition, (n = 20 birds per treatment) birds were killed by cervical dislocation. All surviving hens were killed at 64 wk of age. All carcasses were studied in terms of selected organ weights and reproductive organ morphology. Birds killed at photostimulation and at sexual maturity were further studied for whole body carcass composition.Significant differences were found in dry matter, water, lipid and ash content among treatment groups at the age of photostimulation. As age at photostimulation increased, absolute weight of carcass fat, protein and ash increased. The percent carcass lipid content increased for all groups between photostimulation and sexual maturity with the 16 wk treatment group showing the largest increase. The time required to reach sexual maturity from the age of photostimulation decreased as the age at photostimulation increased. No significant differences were found in total egg production. The 16 wk group laid significantly smaller eggs. Delaying sexual maturity until 20 wk of age resulted in an increased prime sequence length and fewer pause days to produce approximately the same number of eggs as birds that were photostimulated at 16 wk of age. Key words: Chicken, egg-type hens, sexual maturity, egg production, carcass composition

Changes in the Control of the Hypothalamic-Pituitary Gonadal Axis Across Three Differentially Selected Strains of Laying Hens (Gallus gallus domesticus)

“…Intriguingly, despite the small window of body weight between strains at AFE, Smoky Joe hens continued to lag behind in weight at the time of and 1-week post-PS, suggesting that PS had an influence on the body weight increase of these hens. This is similar to studies in both broiler breeder and turkey hens, which showed that while body weight differed at the various ages of photostimulation, overall, there was no impact on the body weight of these hens at maturation ( Robinson et al, 1996 ; Applegate and Lilburn, 1998 ). Therefore, photostimulation was shown to only influence the age of the maturation process, potentially allowing these hens to reach their optimal body weight threshold at an earlier age.…”

Oviposition Patterns Associated with Prolactin Concentration in Domestic Chicken (Gallus domesticus)

“…It has been postulated that age at first oviposition is influenced by external stimuli in addition to the genetic constitution of the birds. The age at first ovulation is influenced by supplemental light (Eitan and Sollan, 1991;Robinson et al, 1996) or not (Lupicki 1994), in the present study maintaining birds at continuous light resulted in decrease in age at first ovipositon. Although the decrease was lower than those reported by Lupicki, (1994) the decrease was not significantly altered due to 2-bromo-αergocriptine treatments.…”

“…Robinson et al (2001) reported that early age at first oviposition impairs egg production since greater allocation of energy is towards ovary in young age, which might have caused impairment in ovarian control (Robinson et al, 1993). Secondly, limited body reserves would have been depleted by the time of peak egg production as reported by Robinson et al (1996). The results observed in the experiment indicate that high total egg production was primarily a function of higher rates of lay through out the laying period of 72 weeks, rather than age at sexual maturity.…”

Effects of Nutrient Density and Age at Photostimulation on Carcass Traits and Reproductive Efficiency in Fast- and Slow-Feathering Turkey Hens

“…2 FF = fast-feathering; SF = slow-feathering; CON = formulated as a standard commercial diet to meet breeder-recommended nutrient levels; HIGH = formulated to contain at least 8%, and not more than 15% more protein, including essential amino acids, than the CON diet; LYF = large yellow follicles on the ovary. growth, and organ development at SM (Yuan et al, 1994;Robinson et al, 1996b;Zuidhof et al, 2007). Delaying PS results in increased early egg size in broiler breeders (Joseph et al, 2002;Renema et al, 2007) and a reduction in the incidence of multiple ovulations in turkeys (Woodard et al, 1974).…”