Impact of growth trajectory on sexual maturation in layer chickens

Abstract

Recent studies showed that apart from photostimulation, metabolic triggers may independently activate sexual maturation and egg production in chickens. However, the origin, mode of action, and specific target(s) of this metabolic control remain unknown. Beyond body weight (BW), we hypothesize that body composition (BC) and associated specific metabolic signals are involved. Thus, this study was conducted to determine the BW and BC thresholds triggering spontaneous sexual maturation in layer pullets under different growth trajectories. Day-old Lohman LSL lite and Lohman brown lite chicks (n = 210 each) raised in brooding cages under ad libitum (AL) feeding until 8 weeks of age were randomly allocated into individual cages and assigned to one of 3 experimental growth profiles; AL, breeder’s target (T), restricted 20% below target (R), (n = 70 birds/profile/strain). Birds had free access to water throughout the trial. All hens were maintained on 10 h of light (10 lux) throughout the rest of the study. Blood and tissue samples were collected throughout the study to measure plasma estradiol (E2) concentrations and organ weights, respectively. Furthermore, carcasses were subjected to Dual-energy X-ray absorptiometry (DEXA) analyses. All analyses were completed with SAS using the MIXED procedure. Results show that R treatment slowed (p < 0.001) growth, delayed age at first egg (FE) and egg production (p < 0.001) and resulted in lower BW at FE (p < 0.001), lower ovary weight and number of follicles (p < 0.001) compared to AL in both strains, whereas, the strain significantly impacted body weight (p < 0.0001), ovary weight (p < 0.001), BW at FE (p < 0.001), age at FE (p < 0.001), egg production (p < 0.0001), E2 (p < 0.0001) and body composition (p < 0.05). For DEXA, AL feeding (p < 0.001) increased fat deposition compared to R. Furthermore, there was a positive correlation between plasma E2 and bone mineral content (p < 0.01) and bone mineral density (p < 0.01). In conclusion, feed allocation impacted growth and BC in a strain dependent manner which resulted in differing age at sexual maturation and egg production. Furthermore, a body fat threshold between 10% to 15% appears to be required for the occurrence of spontaneously sexual maturation in laying hens.

Physiological role of dietary energy in the sexual maturity: clues of body size, gonad development, and serum biochemical parameters of Chinese indigenous chicken

“…As found in the results, the higher energy level in the diet increased the body weight before sexual maturity and advanced age at first egg. These results were congruent with the recent study ( Bahry et al, 2023 ). The body weight at first egg and abdominal fat weight were also found to be negatively correlated with the age at first egg.…”

“…The low dietary energy levels resulted in a smaller body weight and body size during the rearing time, while no difference was observed between 3 groups at sexual maturity except for interpubic distance. The similar results that low-energy level depressed the body weight and delayed sexual maturity was also found in previous studies ( van der Klein et al, 2018 ; Bahry et al, 2023 ). Likewise, there was no significant difference in body weight at sexual maturity in chickens fed different dietary energy contents in previous study ( Hocking, 2004 ).…”

Dietary exogenous phytase improve egg quality, reproductive hormones, and prolongs the lifetime of the aging Hy-Line brown laying hens fed nonphytate phosphorus

“…Moreover, Saleh et al (2020) reported that Mn is a cofactor in cholesterol synthesis which is precursor for the steroid hormone's production. Furthermore, Bahry et al (2023) found that plasma E2 have a positive correlation with bone mineral content and density. Therefore, we speculate that phytase might be prolong the lifetime of egg production through increasing the reproductive hormones and afforded sufficient minerals.…”

Effects of Metabolizable Energy Intake and Body-Weight Restriction on Layer Pullets: 1-Growth, Uniformity, and Efficiency

“…Egg-type pullets are known to have small BW difference when restricted-fed at 70% compared to ad libitum feeding by the time of photostimulation [32]. More recently, Bahry et al [13] showed that Lohmann Brown-Lite pullets fed ad libitum had greater BW when compared to target-fed or those fed 20% below the target BW. In the above study, pullets were fed conventionally [13], similarly to the present study, where the CON experiment showed larger BW differences in the ad libitumvs.…”

“…Restricted pullets have lower maintenance requirements, consuming less feed and being more efficient [11]. On the other hand, severe feed restriction during the rearing period can limit nutrient intake and decrease BW and egg production [12,13]. Additionally, restricted birds have increased lean mass deposition [14], which can further prevent birds from developing hemorrhagic liver syndrome [15], but also may decrease reproductive capacity.…”