Effect of age and body weight at photostimulation on the sexual maturation of broiler breeder pullets transferred from 8L:16D to 16L:8D

Effect of early photostimulation at 15-weeks of age and everyday spin feeding on broiler breeder performance

To prevent broiler breeders from growing too quickly and becoming too large for optimum reproduction, their dietary intake is restricted. While current restricted feeding programs, such as skip-a-day feeding (SAD), improve the economic efficiency of broiler breeder operations, this management practice impacts bird welfare. There is an interest in finding strategies that could reduce the impact of feed restriction during broiler breeder rearing. This research investigated the effects of feeding pullets on an advanced growth curve for early photostimulation at 15 wk (15P) or standard growth curve for photostimulation at 21 wk (21P), using either an every-day-spin feeding program (EDS) or SAD feeding, on the reproductive parameters of broiler breeder hens in a 2 × 2 factorial arrangement. Overall, advancing the growth curve (15P) decreased blood corticosterone levels compared to 21P, but EDS resulted in higher blood corticosterone levels compared to SAD. At the end of rearing in both 15P and 21P, EDS pullets weighed less than SAD pullets. The onset of egg production was 20 and 24 wk of age for the 15P and 21P hens, respectively. Despite an earlier onset, 15P hens did not produce more eggs than 21P hens through 65 wk of age. Egg weight was reduced for 15P compared to 21P until 30 wk of age. The 15P hens had a greater number of double yolk eggs than the 21P hens. Fertility and hatch were not impacted by the advanced growth curve and early photostimulation. Although the current research indicates the potential to reduce feed restriction associated welfare issues by rearing broiler breeder pullets for an earlier photostimulation onset, further research in needed to determine if this management technique can be improved to optimize hen reproductive efficiency.

Untargeted LC-MS-based metabonomic analysis of the effect of photoperiod on the testes of broiler roosters

Photoperiod is an important factor that stimulates the reproductive performance of broiler breeder roosters. However, the mechanism by which photoperiod affects the reproductive performance of broiler breeder roosters has not been fully studied. To study the effects of different photoperiods on the reproductive performance of broiler breeder roosters, 120 Arbor Acres broiler breeder roosters aged 20 weeks were randomly assigned to three groups (n = 40), and the three groups were treated with different photoperiod regimes: control (CTR; 12.5 h of light and 11.5 h of dark, 12.5 L: 11.5 D), short day (SD; 16 L: 8 D) and long day (LD; 8 L: 16 D). Serum and testes were collected after 4 weeks of feeding, and testosterone-related indices were detected. We found that testosterone synthesis in the testes of broiler roosters was boosted with prolonged of photoperiod. Subsequently, metabonomics was used to identify the differential endogenous metabolites that may affect the function of the testes in breeder roosters. We found compared with other groups, the concentrations of creatine, uridine monophosphate, phosphoribosyl pyrophosphate, dCMP, α-D-glucose and citric acid in the SD group decreased significantly (p < 0.05), and glyoxylic acid, D-ribose 5-phosphate, deoxyuridine and orotic acid in the SD group increased significantly (p < 0.05), while the CTR group and LD group showed no significant difference (p > 0.05). The concentrations of linoleic acid and α-linolenic acid in the LD group were increased significantly (p < 0.05) than those in the CTR and SD groups. Compared with the CTR group, the concentrations of histamine in the SD and LD groups were significant increased (p < 0.05). The 13 of the different metabolites could be used as candidate biomarkers for different photoperiods affecting testosterone synthesis, may be used to molecular breeding of high reproductive performance broiler roosters.

Effect of age at photostimulation on sexual maturation and egg-laying performance of layer breeders

The objective of this study was to determine the effect of age at photostimulation on sexual maturity and performance of layer breeders. A total of 192 fourteen-wk-old White Leghorn (WL) breeder hens were randomly allocated to 4 treatments of 48 birds each, with 2 replicates per treatment. The birds were photostimulated at 16 (PS16), 18 (PS18), 20 (PS20), and 22 (PS22) wk of age. Four birds per treatment were randomly selected to evaluate sexual organ development at 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. The ovary weight, large yellow follicles number (LYF), oviduct weight, and oviduct length of PS18 increased sharply after photostimulation. Conversely, the increase in PS16 was not observed until 2 wk after photostimulation. There was no difference in age at sexual maturity between treatments (P > 0.05). The PS16 had the longest interval (28 D) from photostimulation to 5% egg production, while PS22 reached 5% egg production 7 D before photostimulation. The PS22 had lower peak production (P = 0.02) and less egg production (P = 0.02) than other treatments. The PS16 had more broken and abnormal eggs (P = 0.01) and lower hatchability (P = 0.04) than other treatments. In conclusion, photostimulation at 16 and 22 wk of age decreases hatchability and egg production, respectively, and photostimulation at 18 wk is appreciated for the WL breeder hens.

Early photostimulation at the recommended body weight reduced broiler breeder performance

To synchronize the onset of sexual maturity in the face of high BW variation, the age at photostimulation has been increasing in the broiler breeder industry. This experiment studied the effects of increased BW and earlier photostimulation on broiler breeder reproductive performance where within-treatment BW uniformity was very high. The experiment tested BW and age at photostimulation treatments in a 2 × 2 factorial arrangement. Hens (n = 120) were fed with a precision feeding system to allocate feed individually following the breeder-recommended target BW (Standard) or to a 22% heavier target BW curve reaching the Standard 21 wk BW at 18 wk (High). Hens were photostimulated at either 18 wk (18WK) or 21 wk (21WK) with a 16L:8D photoschedule. Age at first egg (AFE) and individual egg production to 55 wk were recorded. Differences were reported as significant if P ≤ 0.05. The AFE was decreased and maturation interval between photostimulation and AFE was shorter for hens on the High BW treatment compared to the Standard BW treatment (178.1 vs. 194.7 d and 41.8 vs. 58.2 d, respectively). Hens on the 21WK treatment had a decreased AFE compared to the 18WK treatment (177.0 d vs. 195.9 d) and their maturation interval was shorter (30.0 d vs. 69.9 d). The CV for AFE was higher in the 18WK treatment compared to the 21WK treatment (28.2% vs. 11.2%). Total egg production was higher for hens on the High BW treatment compared to the Standard BW treatment (129.4 vs. 92.8, respectively). Total egg production was higher for hens on the 21WK treatment compared to the 18WK treatment (138.4 vs. 83.8, respectively). Egg weight of Standard BW × 18WK hens was lower compared to High BW × 18WK hens. Current recommended breeder BW may be too low for optimal sexual maturation after photostimulation. It is concluded that even when BW variation is minimized, photostimulation at 18 wk of age is not recommended.

Temporary exposure of prepubertal, somatically-mature broiler breeder females to stimulatory photoperiods

1. Individually-caged Ross 308 broiler breeders were transferred temporarily at 147 d from 8 to 14-h photoperiods and back to 8 h at 5-d intervals from 5 to 25 d and at 32 d. Control birds were maintained on 8 h or transferred permanently to 14 h. 2. Five long days had minimal effect on age at first egg, between 10 and 25 long days progressively accelerated sexual development, and maximum advance was achieved by 32 long days. However, a model involving the ogive of a normal distribution with a mean of 14 long days and an SD of 5.3 indicated that 28 long days would be sufficient to maximise sexual development. 3. The similarity of this model for broiler breeders with one previously produced for egg-type pullets suggested a common physiological mechanism for photosexual responses to two opposing changes in photoperiod.

Model to predict age at sexual maturity in broiler breeders given a single increment in photoperiod

1. Data from 9 experiments in which broiler breeder pullets had been photostimulated at two or more ages were integrated to produce a model to predict age at 50% egg production following a single increase in photoperiod during rearing. 2. It was clear that the photosexual response in broiler breeders was strongly influenced by the feed allowance and hence the rate of prepubertal growth. Regressions for birds given either a constant photoperiod or a single increase indicated that mean age at 50% lay advances by 2 d for every 100-g increase in body weight at 20 weeks. 3. The general response of broiler breeders was similar to that previously reported for egg-type pullets, but with important changes in the ages at which the birds progressed from one physiological state to the next, depending on body weight. 4. Broiler breeders, unlike modern egg-type pullets, exhibit juvenile photorefractoriness and, depending on their body weight, require up to 20 weeks to dissipate this (faster growth allows quicker dissipation). As a consequence, a group of birds grown to a typical weight of 2.1 kg at 20 weeks do not start to be photoresponsive until about 10 weeks and are not uniformly responsive until 19 or 20 weeks. A transfer to a stimulatory photoperiod before a bird has dissipated photorefractoriness causes a delay of about 3 weeks in its sexual development, and this results in a bimodal distribution of ages at maturity when a flock is photostimulated between 10 and 20 weeks. 5. Once photosensitive, the response of broiler breeders to an increment in photoperiod is between 0.50 and 0.65 of that observed in ISA Brown egg-type pullets. However, a flock of broiler breeders with typical feed restriction starts to mature spontaneously under the influence of the initial photoperiod from about 25 weeks. 6. There is a difference of only 1 to 3 d in age at 50% egg production between a flock transferred to 11 or 12 h followed by further increases to 15 or 16 h and one increased abruptly to one of these photoperiods, and so this model can be used to predict maturity in a commercial flock of birds even though they are likely to be given a stepped, rather than a single, increase in photoperiod.