The effect of a green and blue monochromatic light combination on broiler growth and development

One Health: Circadian Medicine Benefits Both Non-human Animals and Humans Alike

Circadian biology's impact on human physical health and its role in disease development and progression is widely recognized. The forefront of circadian rhythm research now focuses on translational applications to clinical medicine, aiming to enhance disease diagnosis, prognosis, and treatment responses. However, the field of circadian medicine has predominantly concentrated on human healthcare, neglecting its potential for transformative applications in veterinary medicine, thereby overlooking opportunities to improve non-human animal health and welfare. This review consists of three main sections. The first section focuses on the translational potential of circadian medicine into current industry practices of agricultural animals, with a particular emphasis on horses, broiler chickens, and laying hens. The second section delves into the potential applications of circadian medicine in small animal veterinary care, primarily focusing on our companion animals, namely dogs and cats. The final section explores emerging frontiers in circadian medicine, encompassing aquaculture, veterinary hospital care, and non-human animal welfare and concludes with the integration of One Health principles. In summary, circadian medicine represents a highly promising field of medicine that holds the potential to significantly enhance the clinical care and overall health of all animals, extending its impact beyond human healthcare.

The Behavioral and Productive Characteristics of Japanese Quails (Coturnix japonica) Exposed to Different Monochromatic Lighting

The purpose of this study is to examine the impact of monochromatic illuminations at wavelengths of white (400-700 nm), green (560 nm), yellow (580 nm), blue (480 nm), and red (660 nm) on the performance and behavioral traits of Japanese quails throughout their fattening period. A total of 300 quails in five lighting experimental groups were housed in their conventional rearing cages. Weekly live weights of quails were measured individually, developmental stability was determined, and behavior and fear tests were performed. The body weight averages of quails exposed to blue, green, and yellow light were determined to be greater than those exposed to white and red light (p < 0.05). In terms of the mature weight parameter and the weight of the inflection point of the Gompertz growth model, the averages of the quails exposed to green and blue monochromatic lighting were higher (p < 0.05). The most negative findings on aggressive behavior were observed in birds exposed to monochromatic yellow and red light. Although the body weight of quails exposed to yellow monochromatic lighting was similar to that of quails exposed to green and blue monochromatic lighting, green and blue monochromatic lighting produced the best results in terms of growth, behavior, and developmental stability characteristics. Consequently, it is believed that consistently using green or blue monochromatic lighting programs when raising Japanese quails may provide economic advantages to the producers.

The signal pathway of melatonin mediates the monochromatic light-induced T-lymphocyte apoptosis in chicken thymus

Our previous study revealed that under monochromatic red light (RL), the melatonin nuclear receptor reduces the proliferation activity of broiler thymic lymphocytes through the P65 signaling pathway. The main objective of this study was to investigate the signal mechanism by which RL decreases thymic lymphocyte proliferation. Initially, broilers were purchased and randomly assigned to be fed under white light (WL), red light (RL), green light (GL), and blue light (BL). Pinealectomy was performed 3 d later, and the broilers were euthanized after 14 d. The results showed that the expression of the antiapoptotic proteins Bcl-2/Bcl-xl decreased under RL, while the expression of the pro-apoptotic factor Bax/caspase-3 and the pro-inflammatory factors INF-γ/TNF-α/IL-6 increased. After pinealectomy, the expression of Bax/TNF-α/IL-6 increased in conjunction with the decrease in Bcl-2 expression. In vitro experiments demonstrated that exogenous melatonin decreased the expression of Bax/TNF-α/IL-6 in thymic lymphocytes of chicks reared under RL. This melatonin-induced effect was enhanced by SR1078 (RORα/RORγ agonist) but attenuated by SR3335 (RORα antagonist) and BAY (P65 antagonist). These findings revealed that the melatonin nuclear receptor RORα/RORγ promotes the expression of the pro-apoptotic factor Bax/caspase-3 and the pro-inflammatory factors INF-γ/TNF-α/IL-6, while inhibiting the expression of the antiapoptotic factor Bcl-2/Bcl-xl. Our research suggested the signaling pathway of monochromatic red light impacts the apoptosis of thymus lymphocytes in broiler.

Improvement of weanling pigs immune status and metabolic condition using ultraweak light

Weaning stress is the most common issue in swine farms, which increases mortality and morbidity. The use of artificial light is an option for modifying the immune system and metabolic pathways. This study aimed to evaluate the influence of ultraweak light (Photonia) on growth performance, immune system and metabolism of weanling pigs, and the carry-over effect on the growth performance in postweanling growing stages. A total of 30 weaned pigs with an average initial body weight of 7.06 ± 0.11 kg (age: 21 days) were allotted two treatments (Control and Photonia) with 15 replicates. The pelleted form diets were prepared for pigs in three phases including phase 1 (Days 0-14), phase 2 (Days 15-28) and phase 3 (Days 29-48). The gain-to-feed ratio (G:F) of pigs was significantly greater in the Photonia treatment. On Day 28, a higher concentration of immunoglobin A (IgA) (p < 0.01) and IgG (p < 0.01) was observed in the Photonia pigs. On Day 48, the Photonia treatment showed a greater serum IgA (p < 0.01) and IgG (p < 0.05). The concentration of interleukin (IL)-6 was decreased (p < 0.05) in the Photonia treatment. At Day 48, the concentrations of tumour necrotic factor-α, IL-1β and IL-6 in serum were decreased (p < 0.05) in pigs in the Photonia treatment. Metabolic pathways analysis showed that the Photonia treatment increased the d-glutamine, d-glutamate, alanine, aspartate, glutamate and phenylalanine compared with the control treatment. In conclusion, the use of Photonia for weanling pigs is recommended due to improved G:F, immune status and activation of amino acids metabolic pathways including d-glutamine, d-glutamate, alanine, aspartate, glutamate and phenylalanine.

Impact of different light intensities to Japanese quail eggs on hatching results and post-hatch performance

The study aims to evaluate dichromatic light with different intensities during incubation on pre- and post-hatch performance of Japanese quail. In completely randomized design, 600 quail hatching eggs were evenly divided into 4 treatments, 3 replicates, and 50 eggs in each. These eggs were provided with lighted incubation [dichromatic light; green-red (GR) with three different intensities 150, 250, and 350 lx] with lighting schedule (12L: 12D), and one treatment was the complete dark period during incubation and considered as control group. After hatch, 300 quail chicks were equally divided into four treatments (3 replicates and 25 chicks in each). Effects of GR light with different intensities during incubation were evaluated on hatching traits and post-hatch performance of Japanese quails. Regarding hatching traits, hatchability was better in all the treated groups (150, 250, and 350 lx of GR light during incubation) compared to complete dark. In terms of embryonic mortality, early embryonic mortality was lower in the 250 lx group, mid embryonic mortality in dark, and late embryonic mortality in the 150 lx group. Furthermore, an ideal chick spread and growth performance (weight gain, feed intake, feed conversion ratio, and liveability) was reported in 250 lx group compared to other treated groups. Serum chemistry values were higher in dark group compared to 150, 250, and 350 lx groups. Pre-slaughter weight was higher in 250 and 350 lx group than 150 lx and dark group, whereas carcass weight was better in 350 lx group compared to dark. In conclusion, stimulation of dichromatic light (green + red) at 250 lx to Japanese quail eggs positively influenced hatching traits and post-hatch growth performance of Japanese quail.

Evaluation of Light Color Manipulation on Behavior and Welfare of Broiler Chickens

This experiment evaluated the effect of light manipulation on the behavior and welfare of broilers using 280-day-old Arbor-Acre chicks, which were weighed and assigned to 7 treatments having 4 replicates and 10 birds per replicate. The light treatments were as follows: white light (WH), blue light (BL), green (GR), blue light switched to green light at 14 days (2BG), green light switched to blue at 14 days (2GB), blue light switched to green light at 28 days (4BG), and green light switched to blue light at 28 days (4GB). Feeding, drinking, resting, standing, walking, foraging and preening behaviors were observed using the scan sampling method. Behavior and welfare parameters such as footpad dermatitis and hock burn were evaluated and analyzed in a Completely Randomized Design. The results showed that feeding behavior of birds of BL, 2BG, and 2GB treatment groups was significantly higher (P < 0.05) than those of WH and GR at the starter phase. At the finisher phase, resting behavior of birds of 4GB was similar to those of 2GB but higher than those of the other treatments. It was concluded that switching of light from green to blue (4GB) at four weeks of age fostered ideal behavior and stimulated growth in broilers but had no effect on welfare parameters.

Effect of photoperiod during incubation on embryonic temperature, hatch traits and performance of two commercial broiler strains

Provision of light during incubation has shown the potential to enhance hatching traits and affect posthatch productivity, physiology, and behavior. In this study, 2 repeated trials were conducted to investigate the effect of photoperiod and strain on the embryo temperature, hatching traits and posthatch growth performance of 2 commercial strains of broilers (Ross 308 and Cobb 500). In each trial, hatching eggs were randomly distributed into 6 incubators with 3 photoperiod treatments: blue LED light for 12 h d^-1 (12L:12D) or 18 h d^-1 (18L:6D) during entire incubation were compared with no illumination condition (DARK). Data were analyzed as a 3 × 2 factorial arrangement with the trial as the blocking factor. Embryos incubated under 12L:12D and 18L:6D had lower air cell temperature (P < 0.05) than the DARK embryos from d 13 of incubation onward except on the day of candling. The response of air cell temperature to periodic illumination differed between 2 strains. Cobb embryos had lower air cell temperature in 12L:12D than those incubated with 18L:6D from d 16 of incubation onward, whereas lower air cell temperature was found in Ross embryos when illuminated with 18L:6D photoperiod compared to those under 12L:12D. The 12L:12D treatment was associated with improved (P < 0.05) navel closure condition of hatchlings. There were no differences in hatchability, embryo mortality, body weight, or length at hatch among photoperiod groups or its combination with strain. No differences in production parameters were found between DARK and illuminated groups. However, 12L:12D had heavier (P < 0.05) body weight on d 14 of age and higher (P < 0.05) body weight gain than 18L:6D from d 7 to 14 of age. The results of this study indicate that providing blue LED light up to 18 h d^-1 has no detrimental effect on production of broilers, however, 12L:12D light regime improved chick quality at hatch compared to DARK and resulted in heavier birds by d 14 compared to 18L:6D.

Effects of LED Lights with Defined Spectral Proportion on Growth and Reproduction of Indigenous Beijing-You Chickens

Light presents an important exogenous factor for poultry. This study examined effects of LED lights with different defined spectrums on growth and reproduction of indigenous Beijing-You chickens. A total of 576 one-day old female chicks were divided into 16 rooms, and each were exposed to four different lights: LED A (21% green light, 30% blue light, 24% yellow light, and 25% red light), B (35%, 35%, 18%, and 12%), C (27%, 30%, 22%, and 21%), or compact fluorescent lamps (CFL, 15%, 28%, 41%, and 16%). Results showed that feed intake and feed conversion ratio were comparable among treatments throughout the 17 week rearing period (p > 0.05). LED C showed similar body weight gain with CFL, but higher than LED A and B. The CFL birds start to lay on 132.25 d, while LED B did not lay until 148.25 d. The age at 50% egg production did not vary among groups (p = 0.12). Total egg number until 43 week of LED B was higher than others (p < 0.05). Therefore, LED lights with defined spectral proportion have different effects on chickens' growth and reproduction. The LED C promotes the prepubertal growth, and the LED B provides proper sexual maturation age and better egg-laying persistence.

Continuous exposure to red light induces photorefractoriness in broiler breeder pullets

The management of body weight (BW) in broiler breeder pullets is critical to offset the negative correlation between their growth potential and reproductive success. Therefore, a precision feeding system was developed to allocate feed individually based on real-time BW in more frequent, smaller portions. However, this system requires access beyond the 8 h daylength of the rearing period. Since green and red spectra have been shown to stimulate growth and sexual maturation, respectively, this study aimed to evaluate the impact of continuous supplemental illumination of feeders with monochromatic wavelengths on sexual maturation. Furthermore, the best combination of supplemental and daytime lighting for optimizing the pullet-to-hen transition period was investigated. This study contained a 2 × 4 × 2 factorial arrangement, with 2 daytime lights (dtRED and dtGREEN; n = 2 rooms), 4 supplemental lights (sBLUE, sGREEN, sRED, and sCON; n = 12 pens), and 2 supplemental intensities (High and Low). At 3 wk of age (woa), 480 female Ross 708 chicks were randomly distributed across treatments (n = 10/pen). All birds were feed restricted per management guidelines and maintained under 8 h of dtRED or dtGREEN. Birds were photostimulated at 20 woa with 14L:10D. All birds were weighed weekly, with age at first egg (AFE) and production rate calculated weekly per pen. Birds under sRED were heavier than all other treatments from 27 woa to the end of the study (P < 0.001; 30 woa), resulting in hens that were over 400-g heavier. This resulted from a delayed AFE and lower production rate under sRED, with higher intensity further hindering reproductive performance (P < 0.001). Interestingly, despite the inhibitory effect of continuous red lighting (sRED) on reproduction, dtRED resulted in a 3.15% higher rate of lay than dtGREEN. Therefore, this study suggests that while red light remains superior at stimulating reproduction, continuous red supplemental lighting results in photorefractoriness. Thus, we recommend green light in PF systems.

Ecological footprint of poultry production and effect of environment on poultry genes

The growing demand for poultry meat and eggs has forced plenty of changes in poultry production in recent years. According to FAO, the total number of poultry in the world in 2019 was 27.9 billion. About 93% of them are chickens. The number of chickens has doubled in the last 30 years. These animals are the most numerous in Asia and America. Hence, poultry meat is the most frequently obtained type of meat in recent years (it is 40.6% of the obtained meat). Focusing on lowering production costs has led to process optimization, which was possible by improving the use of animal genetics, optimizing feeding programs, and new production technologies. The applied process optimization and production increase practices may also lead to a deterioration of the ecological balance through pollution with chemical substances, water consumption, and natural resources. The aim of this paper was to review the current state of knowledge in the field of the ecological footprint of poultry production and the impact on environmental genes.

The effect of monochromatic, combined, and mixed light-emitting diode light regimes on growth traits, fear responses, and slaughter-carcass characteristics in broiler chickens

This study aims to determine the effects of blue and green monochromatic, blue-green combination, and blue-green mixed led lighting systems on growth, fear, and carcass characteristics of broilers reared in an extensive indoor system. Experimental groups were formed as follows; 1-conventional (incandescent), 2-blue, 3-green, 4-blue-green combined (blue for the first 10 days, then green), 5-green-blue combined (green for the first 10 days, then blue), and 6-blue-green intermittent (alternating every 5 min) monochromatic lightings. It was detected that the average values of the body weight of chickens at 42 and 56 days of age in the green-blue group were higher than those of the other treatment groups (both P < 0.05). It was determined that the broilers in the green and green-blue groups had higher means of the β₀ parameter of Gompertz model. The tonic immobility, emergence test, home cage avoidance test, a looming human test, and box plus experimenter test were applied to determine the fear responses. It was determined that the worst results for fear responses of broilers were in the intermittent lighting group and green-blue combined group. As a result, it was determined that the application of green monochromatic lighting in the first 10 days of the fattening period and blue monochromatic lighting in the following period positively affected growth and slaughter-carcass characteristics. However, it was found that broilers reared under green-blue combined lighting had high fear levels.

Does light color during brooding and rearing impact broiler productivity?

Light color during brooding and rearing may impact broiler production; however, literature results are inconsistent. To address this, the effects of 3 wavelength spectra on broiler performance in 2 sex and 2 genotypes (Ross YPMx708 and EPMx708) were studied. Broilers were raised (d 0–35) under wavelength programs provided by LED light bulbs (blue (455 nm), green (510 nm) or white) under similar intensities (clux). Two trials were conducted (total number of birds =  14,256; 6 room replications per lighting treatment; 18 replicate pens per light × sex × genotype). Data were analyzed as a 3 × 2 × 2 (wavelength × sex × genotype) factorial design, with trial as a random variable block and wavelength nested within rooms (Proc Mixed, SAS 9.4). Birds raised under white light were heavier than under blue or green light at d7 (P = 0.004), and green at d14 (P = 0.03). Feed intake, gain-to-feed efficiency and flock uniformity (d15, 28) did not differ. Mortality only differed at wk 5, when broilers raised under white light had higher mortality than those raised under blue (P = 0.03). YPM-708 were heavier at 21 d (P = 0.007), 28 d (P = 0.001), and 35 d (P < 0.0001), had a better total feed conversion rate (P < 0.0001), higher mortality for wk 1 (P = 0.001), lower mortality during the last wk (P = 0.02) and better uniformity at 28 d (P = 0.01) than EPM-708 broilers. Males were heavier at all measured ages except d0 (d7-P = 0.03, other weeks P < 0.0001), had better total feed conversion (P < 0.0001), increased weekly mortality except for wk 1 (wk2-P = 0.04, wk3-P = 0.002, wk4, 5, and total-P = 0.0001) and were less uniform (P = 0.0002) than females. YPM-708 and EPM-708 males had higher total feed intake (P < 0.0001), and males raised under white light had higher mortality than females raised under white or blue light (P = 0.01). To conclude, the use of specific light colors (blue and green) had only minor impacts on broiler production when light intensity was equalized and balanced for bird spectral sensitivity, and its use to improve productivity does not appear to be advantageous for broilers in a commercial setting.

Chicken Incubation Conditions: Role in Embryo Development, Physiology and Adaptation to the Post-Hatch Environment

The chicken hatching egg is a self-contained life-supporting system for the developing embryo. However, the post-hatch performance of birds depends on several factors, including the breeder management and age, egg storage conditions and duration before incubation, and the incubation conditions. Studies have determined the effect of incubation factors on chick post-hatch growth potential. Therefore, chick physical quality at hatch is receiving increasing attention. Indeed, although incubation temperature, humidity, turning and ventilation are widely investigated, the effects of several variables such as exposure of the embryo to high or low levels, time of exposure, the amplitude of variations and stage exposures on embryo development and post-hatch performance remain poorly understood. This review paper focuses on chick quality and post-hatch performance as affected by incubation conditions. Also, chick physical quality parameters are discussed in the context of the parameters for determining chick quality and the factors that may affect it. These include incubation factors such as relative humidity, temperature, turning requirements, ventilation, in ovo feeding and delay in feed access. All these factors affect chick embryo physiology and development trajectory and consequently the quality of the hatched chicks and post-hatch performance. The potential application of adapted incubation conditions for improvement of post-hatch performance up to slaughter age is also discussed. It is concluded that incubation conditions affect embryo parameters and consequently post-hatch growth differentially according to exposure time and stage of exposure. Therefore, classical physical conditions are required to improve hatchability, chick quality and post-hatch growth.

Broiler behavior differs from males to females when under different light wavelengths

It is well established that different light wavelengths affect broiler behavior. The present study aims to evaluate the effect of four light wavelengths on broiler behavior from 1 to 42 days of age. Birds were housed at a stocking density of 13 birds/m2, in 32 boxes of 1.56 m2. The experimental design was a completely randomized factorial of 4 × 2 (four colors × two sexes), with four replicates. Behavioral variables were accessed through cameras and observed in person thrice a week for 30 min per day in three different periods. Data were organized according to age groups and analyzed by a data mining approach with the different light wavelengths as the classes. Natural behavior defined by stretch, dust bath of male broilers reared in environments with green and blue light was more relevant to the classification of male broilers' behavior (96.9 and 96.9% accuracy and 0.8 and 1.0 of class precision of behavior classification, respectively). Blue and green lights affected the behavior of male broilers starting at 7 days of age, increasing the presence at the bird feeder, and reducing the idle period.

Interactions between color and intensity of LED light on growth performance, serum biochemical profile, immune response variable, and nutrient apparent utilization in broiler chicken

This study investigated the effects of light-emitting diode (LED) color and intensity of broilers. One-day-old Cobb-500 broilers (n = 648) were fed nine groups with six replicates; three light colors (white, blue, & green) and intensities (for 1 to 7 days, viz., 20, 40, and 60 lx; for 8 to 42 days, viz., 5, 10, and 15 lx) were applied. Test lasted for 42 days. Results indicated that compared with blue light, 60-lx white light for 1 to 7 days increased the average daily gain (ADG) and average daily feed intake (ADFI) of broilers (p < 0.01). In the 10-lx light groups, the levels of interleukin-2 (IL-2) and the concentrations of albumin (ALB) (p < 0.05) increased. Moreover, the nutrient apparent utilization for ether extract (EE) under 10-lx green light was higher than that under 15-lx blue light (p < 0.01). The interaction effects of light intensity and light color had an extremely significant influence on the ADG for 1 to 7 days, IL-2 level, ALB content, and EE apparent utilization rate (p < 0.01) and had a significant influence on the ADFI and F/G for 1 to 7 days (p < 0.05). The production performance of broilers reared in three-layer cage could be improved by using 60-lx white LED light for 1 to 7 days and 5- to 10-lx green LED light or 10-lx white LED light for 8 to 42 days.

Light Color and the Commercial Broiler: Effect on Ocular Health and Visual Acuity

Light is a critical management factor for broiler production, and the wavelength spectrum, one of its components, can affect bird physiology, behavior and production. Among all the senses, sight is important to birds, and their visual system possess several adaptations that allow them to perceive light differently from humans. Therefore, it is critical to consider whether the exposure to monochromatic light colors influences broiler visual ability, which could affect behavioral expression. The present study examined the effects of various light colors on the visual systems of broiler chickens. Ross 708 males were raised from 0 to 35 days under three wavelength programs [blue (dominant wavelengths near 455 nm), green (dominant wavelengths near 510 nm) or white]. Broilers were given a complete ophthalmic examination, including chromatic pupillary light reflex testing, rebound tonometry, anterior segment biomicroscopy and indirect ophthalmoscopy (n = 36, day 21). To assess ocular anatomy, broilers were euthanized, eyes were weighed, and dimensions were taken (n = 108, day 16 and day 24). An autorefractor was used to assess the refractive index and the corneal curvature (n = 18, day 26). To evaluate spatial vision, broilers underwent a grating acuity test at one of three distances–50, 75, or 100 cm (n = 24, day 29). Data were analyzed as a one-way ANOVA using the MIXED procedure or Proc Par1way for non-normally distributed data. Significant differences were observed for refractive index and spatial vision. Birds raised under blue light were slightly more hyperopic, or far-sighted, than birds raised under white light (P = 0.01). As for spatial vision, birds raised under blue light took less time to approach the stimulus at distances of 50 cm (P = 0.03) and 75 cm (P = 0.0006) and had a higher success rate (choosing the right feeder, P = 0.03) at 100 cm than birds raised under white light. Improvements in spatial vision for birds exposed to blue light can partially explain the behavioral differences resulting from rearing broilers under different wavelengths.

Improving Gander Reproductive Efficacy in the Context of Globally Sustainable Goose Production

The goose is a popular poultry species, and in the past two decades the goose industry has become highly profitable across the globe. Ganders low reproductive performance remains a barrier to achieving high fertility and hatchability in subsequent flocks. To address the global demand for cheaper animal protein, various methodologies for improving avian (re)production should be explored. A large amount of literature is available on reproduction traits and techniques for commercial chicken breeder flocks, while research on improved reproduction in ganders has been carried out to a lesser extent. The present review aims to provide a comprehensive literature overview focusing on recent advancements/techniques used in improving gander reproductive efficacy in the context of ensuring a globally sustainable goose industry.

Prolonging photoperiod promotes testosterone synthesis of Leydig cells by directly targeting local melatonin system in rooster testes

The study investigated the effects of prolonging photoperiod on the synthesis of testosterone and melatonin in roosters, and the effect of melatonin on testosterone synthesis in rooster Leydig cells as well as its molecular mechanisms. We randomly divided one hundred and twenty 20-week-old roosters into three groups and provided 6, 12.5 and 16 h light, respectively. The results showed that prolonging photoperiod promoted testosterone synthesis, decreased melatonin production, and inhibited the expression of melatonin membrane receptors MEL1A, MEL1B, MEL1C, and aralkylamine n-acetyltransferase (AANAT) in rooster testes. Subsequently, rooster Leydig cells were isolated and treated with 0, 0.1, 1, 10, and 100 ng/mL melatonin for 36 h. The results suggested that melatonin inhibited testosterone synthesis in rooster Leydig cells, and silencing MEL1A and MEL1B relieved the inhibition of melatonin on testosterone synthesis. Additionally, melatonin reduced the intracellular cyclic adenosine monophosphate (cAMP) level and the phosphorylation level of cAMP-response element binding protein (CREB), and CREB overexpression alleviated the inhibition of melatonin on testosterone synthesis. Furthermore, pretreatment with cAMP activator forskolin or protein kinase A (PKA) activator 8-bromo-cAMP blocked the inhibition of melatonin on CREB phosphorylation and testosterone synthesis. These results indicated that prolonging photoperiod promoted testosterone synthesis associated with the decrease in melatonin production and membrane receptors and biosynthetic enzyme of melatonin in rooster testes, and melatonin inhibited testosterone synthesis of rooster Leydig cells by inhibiting the cAMP/PKA/CREB pathway via MEL1A and MEL1B. This may be evidence that prolonging photoperiod could promote testosterone synthesis through the inhibition of the local melatonin pathway in rooster testes.

Centennial Review: History and husbandry recommendations for raising Pekin ducks in research or commercial production

By some accounts, ducks were domesticated between 400 and 10,000 yr ago and have been a growing portion of the poultry industry for decades. Ducks specifically, and waterfowl in general, have unique health, housing, nutrition and welfare concerns compared to their galliform counterparts. Although there have been many research publications in regards to health, nutrition, behavior, and welfare of ducks there have been very few reviews to provide an overview of these numerous studies, and only one text has attempted to review all aspects of the duck industry, from breeders to meat ducks. This review covers incubation, hatching, housing, welfare, nutrition, and euthanasia and highlights the needs for additional research at all levels of duck production. The purpose of this review is to provide guidelines to raise and house ducks for research as specifically related to industry practices.

Providing colored photoperiodic light stimulation during incubation: 1. Effects on embryo development and hatching performance in broiler hatching eggs

Providing lighting schedule during incubation has been shown to improve chick quality and reduce stress posthatch. This study was conducted to evaluate the effects of providing light of different colors during incubation on embryo development, air cell temperature, the spread of hatch, and hatching performance. Four batches of eggs (n = 2,176, 1,664, 1,696 and 1,600) from Ross 308 broiler breeders were used in the experiment. In each trial, eggs were randomly distributed into 4 lighting treatments. The incubation lighting treatments included: incubated under dark as control, illuminated with white, red or blue lights for 12 h daily. There were no incubation lighting treatment differences in embryo development, the spread of hatch, hatchability, embryo mortality, hatch weight, chick length, navel closure quality, yolk-free body weight, or relative spleen weight. However, embryos incubated under red light had lower average air cell temperature than those in dark, white or blue light treatments. This finding may suggest higher melatonin secretion during the scotophase when illuminated with red light. Male chicks incubated under dark had a higher bursa of Fabricius weight than males illuminated with blue light. In conclusion, these results suggest that the red, white and blue light stimulation during incubation had no negative effects on hatchability, embryo mortality, spread of hatch or day-old chick quality, but may have potential impacts on immunity and energy metabolism in broiler embryos.

Providing colored photoperiodic light stimulation during incubation: 2. Effects on early posthatch growth, immune response, and production performance in broiler chickens

Previous findings have reported that providing light during incubation can affect hatchability and chick quality. This study was conducted to investigate the effects of providing light during incubation on posthatch broiler production parameters, thermoregulation and immune response. Lights with different wavelengths were used over the course of four separate hatches. Ross 308 broiler hatching eggs were randomly distributed into 4 lighting treatments for each hatch. The incubation lighting treatments included: dark as control, white, red, or blue lights for 12 h d^-1 (200 lux at egg level). Broilers hatched from each incubator with the same gender were placed into one of 8 sets of pens (3 pens/set) and raised under 18 h d^-1 photoperiod. Six birds per pen were immunized intraocularly with AviPro ND-IB Polybanco vaccine on d 10 and 21 posthatch. Chicks hatched under white and blue lights had heavier (P < 0.05) body weight and higher (P < 0.05) feed consumption than the control group during the first 6 h postplacement. No differences in vent temperature were found among treatments at 24 h posthatch (P > 0.05). Chicks hatched with light stimulation however had more stable (P < 0.05) cloaca temperature at 36 h posthatch. No differences in average body weight gain, feed consumption or feed conversion ratio were found among lighting treatments between d 7 and d 35. On d 14 of age, birds hatched from red light had higher (P < 0.05) total IgG concentration than those hatched under dark, blue or white light. These results indicated that in ovo light stimulation with different wavelengths did not affect growth parameters of broilers at market age. Providing photoperiodic blue and white light during incubation improved the production parameters of broilers during the first week posthatch.

Effects of Monochromatic Lighting During Incubation and Vaccination on the Splenic Transcriptome Profiles of Chicken

Lighting is a crucial environmental variable in poultry operations, but illumination during incubation is relatively understudied. The ability to stimulate development or immune performance using in ovo lighting is a promising approach for improving poultry health and welfare. This study investigated how monochromatic green light during incubation and vaccination method and timing affected chicken splenic gene expression patterns. We performed this study with 1,728 Hy-Line white layer eggs incubated under two light treatments during incubation: continuous dark and continuous green monochromatic light, over the entire incubation period. Half the eggs in each light treatment received in ovo vaccination, applied on embryonic day 18 (ED18). The remaining half were vaccinated by spraying on hatch day. After hatching, the light treatments followed the industry-standard lighting regimens. The study had six treatment groups with light-dark pairs for non-vaccinated, in ovo vaccinated, and post-hatch vaccinated. We assessed splenic gene expression at ED18 and at 7 days post-hatch (PH) in all the treatments. We isolated and sequenced 24 mRNA libraries on the Illumina platform, followed by bioinformatics and differential gene expression analyses. RNAseq analysis showed between 62 and 6,755 differentially expressed genes (DEGs) between comparisons, with the most prominent differences observed between ED and PH samples, followed by comparisons between vaccination methods. In contrast, light vs. dark treatments at ED showed limited effects on transcriptomic profiles. However, we observed a synergistic effect of lighting during incubation on post-hatch vaccination responses, with differentially expressed genes (DEGs) unique to the light treatment showing stimulation of cell proliferation with significance for immune activity (inferred from gene ontology terms). Gene ontology and pathway analysis indicated biological processes like cellular component organization or biogenesis, rhythmic process, developmental process, response to stimulus, and immune system processes were explained by the DEGs. While lighting is an important source of circadian stimulation, other controlled studies are required to clarify whether in ovo circadian entrainment plays a role in modulating immune responses.

A comparison of white/red and white/blue LED light fixtures on Pekin duck production, stress and behaviour

1. The objective of this study was to determine the effects of two mixed LED light spectra on duck production, stress and fear responses. Pekin ducks were reared under either white/red (WR) or white/blue (WB) LED light.2. No differences were observed in feed conversion ratio (P = 0.690) or d 35 body weight (P = 0.919). Furthermore, no differences were observed in plasma interleukin-12 concentrations (P = 0.449), anti-keyhole limpet haemocyanin IgG titre (P = 0.503) or composite physical asymmetry score (P = 0.839). WR caused lower heterophil to lymphocyte ratios (0.40 ± 0.03, P = 0.029) and plasma corticosterone concentrations (4498 ± 534 pg/ml, P = 0.038) than WB (0.58 ± 0.08; 6518 ± 795 pg/ml, respectively). No differences were found in the number of attempts to induce tonic immobility (TI) or in inversion intensity. A shorter latency to first head movement during TI (9.44 ± 1.22 s, P = 0.06) and an overall shorter latency to right from TI (25.66 ± 2.99 s, P < 0.001) was observed for birds under WR compared to WB (20.91 ± 6.01 s; 58.76 ± 8.86 s). The duration of time spent in the second stage of TI, where birds observed their environment using head movements while still remaining immobile on their backs, was shorter in WR (16.23 ± 1.73 s, P = 0.001) compared to WB (37.85 ± 6.38 s).3. The results indicated that rearing ducks under WR caused less stress susceptibility and fear responses compared to ducks under WB. Pekin duck welfare may be compromised by blue LED light exposure, even at supplemental levels utilised in commercial poultry lighting.

Effect of dietary L-tryptophan supplementation and‏ ‏light-emitting diodes on growth ‎and immune response of broilers ‎

Light-emitting diodes (LEDs) lights are more energy-efficient and provide adequate illumination compared to compact fluorescent (CFL) lamps and incandescent light (ICD) bulbs. However, as new light sources, the LED lights may have a stress effect on broiler chickens. Thus, this study aimed to determine the effects of dietary L-tryptophan (Trp), as an anti-stress agent and different color temperatures of light-emitting diodes on immune responses and growth performance of male broiler chickens. Four hundred and eighty day-old Ross 308 male chicks were used from day 1 to 42. The chicks were randomly distributed into six treatment groups in a 2 × 3 factorial arrangement [0 or 1 g Trp per kg diet along with neutral-white (4286 K), warm-white (2990 K), and incandescent (2790 K) light bulbs] with four replicates of 20 chicks each. Results showed that dietary Trp and Trp×light interaction did not affect growth performance, immune responses, a total number of leukocytes, and different leukocytes count (heterophil, eosinophil, monocyte, and lymphocyte) of male broiler chickens. However, LEDs’ different color temperatures significantly affected the feed conversion ratio (FCR) and primary antibody of sheep red blood cell (SRBC). The FCR was the lowest in the warm-white light, and primary SRBC antibody titers of the chicks were the highest. In conclusion, although adding Trp to male broiler diets did not affect the growth performance and immune responses of chickens, the warm-white light improved the FCR and primary SRBC.

Effects of photoperiod on thyroid gland development and function in growing chicks: a biochemical and morphometric study

Context Light treatment has a regulatory role in some growth-related functions, including thyroid development in chicks. Aims This study aimed to investigate the effects of different photoperiod treatments on thyroid organ weight and serum thyroid hormone concentrations of broilers by use of biochemical and histological methods. Methods After the hatching, 120 broiler chicks (Ross) were divided into two main groups according to sex. Both groups were then split into two sub-groups based on photoperiod treatment: 16 h (i.e. 16 h light:8 h dark) and 24 h (24 h light:0 h dark). Thyroid gland and blood samples of six animals from each group were obtained after slaughtering at 7-day intervals from Day 14 after hatching to Day 42. Serum concentrations of free triiodothyronine (FT3), free thyroxin (FT4) and thyroid-stimulating hormone (TSH) were determined by the chemiluminescence method for all groups. Thyroid weight, bodyweight and thyroid follicle diameter were also measured. Key results Thyroid weight:bodyweight ratio generally started to increase from Day 14 to Day 42, with no significant (P &gt; 0.05) difference among the groups at the same age. For both male and female broiler chicks, morphometric measures increased as birds grew. Serum FT3 and TSH concentrations slightly decreased and serum FT4 concentrations increased in growing chicks of both sexes. Conclusions Extending the photoperiod from 16 to 24 h had no effects on thyroid gland development or functions in terms of both biochemical and morphometric parameters in broiler chicks. Implications Continuous light has minimal effects on thyroid functions of growing broiler chicks to Day 42.

Metabolism of Melatonin Synthesis-Related Indoles in the Turkey Pineal Organ and Its Modification by Monochromatic Light

The metabolism of pineal indoles is closely related to alterations in the light and dark phases of a daily cycle. Recent research showed important interspecies differences in the pineal biochemistry, and a strong impact of monochromatic light on many physiological processes in birds. Therefore, the aims of study were to characterize the metabolism of melatonin-synthesis indoles in the pineal organ of the domestic turkey, and to determine the changes occurring in this metabolism under the influence of different wavelengths and intensities of light. For this purpose, 3-week-old turkeys were kept under 16 lx white light, or under blue, green, and red light with intensities of 16, 32, and 64 lx during the photophase, and after 7 d were sacrificed at 4 h intervals. The activities of melatonin-synthesizing enzymes and the contents of indoles were measured in the same pineal organ. The results revealed that the activities of tryptophan hydroxylase and arylalkylamine N-acetyltransferase, and the levels of all tryptophan derivatives had significant daily changes in birds kept under each light condition used. The profile of pineal indole metabolism in 4-week-old turkeys was characterized by high-amplitude rhythms in the activity of arylalkylamine N-acetyltransferase and the contents of N-acetylserotonin and melatonin, equal relative amounts of serotonin and 5-hydroxyindoleacetic acid, and higher content of melatonin than N-acetylserotonin. The monochromatic light significantly modified the pineal indole metabolism, and its effects were dependent on the color and intensity of light. Pronounced changes occurred in the level of serotonin synthesis and the daily rhythm course of melatonin synthesis.

Effect of various monochromatic light-emitting diode colours on the behaviour and welfare of broiler chickens

This study was conducted to evaluate the effect of different monochromatic light-emitting diode colours on the behaviour and welfare of broiler chicks. A total of 750 one-day-old chicks were used and lighting was set up as follows: pure blue (PB, 440–450 nm), bright blue (460–470 nm), sky blue (480–490 nm), greenish blue (500–510 nm), and green (530–540), while fluorescent white (400–700 nm) was used as a control. Birds were placed into 30 independent light proof pens and each light treatment was replicated five times with 25 birds in each pen. Video was recorded and behaviour was evaluated twice per day and observed five consecutive days in a week. Broiler welfare was evaluated using the characteristics of gait score, tibia dyschondroplasia, tonic immobility duration, and heterophil:lymphocyte ratio. In results, sitting, walking, and ground pecking behaviour were influenced by the light colour from 0 to 7 d. Extending the rearing period from 8 to 21 d resulted in increased sitting behaviour and decreased walking and pecking behaviour in chicks in the PB treatment (P < 0.05). When the growth period was extended further (22–42 d), sitting behaviour increased when chicks were exposed to PB light (P < 0.05). The effect of light colour did not significantly influence welfare of broiler chicks. Thus, the present results suggest that PB light colour decreased broiler chickens movement and thus increased duration of sitting behaviour. These results would be helpful to choose light colour for broiler producers.

Evaluation of light colour manipulation on physiological response and growth performance of broiler chickens

Artificial illumination, including light quality, is crucial in modern broiler management. The aim of this study was to examine the effect of a switch in light colour on the performance of broiler chickens in tropical environments. A total of 280 1-day-old Arbor acre male chicks were used for this study and were weighed and assigned to different light environments viz. white (WH), green (GR), blue (BL), GR switched to BL at 14 days (GB), BL switched to GR at 14 days (BG), BL switched to GR at 28 days (BGG) and GR switched to BL at 28 days (GBB) having four replicates of ten birds each. Body weight, weight gain, feed intake and feed conversion ratio were recorded weekly. Blood samples were collected from 2 birds per replicate weekly for the determination of plasma triiodothyronine (T₃), haematology and serum biochemical parameters. The experiment was laid out in a completely randomised design. Results showed that the final body weights of the birds in GBB and GB were comparable but higher than those of the other treatment groups. Feed intake of the chickens in WH was similar to that of BG but higher than those of the other treatment groups, while FCR of the birds in WH was higher (P < 0.05) than the other treatment groups. Plasma T₃ of the birds in GR was comparable to that of birds in BL but significantly higher than those of the birds in WH and a similar trend was also observed at weeks 1 and 2. Heterophil/lymphocyte ratio (H/L) of the birds in WH was significantly higher than those of BL and GR whose values were similar to those in GB and BG. Heterophil/lymphocytes of the birds in WH was higher than those of BG, GR, BGG, GB and GBB but similar to those of BL. The breast muscle of the birds in GBB and GB was similar to those of BGG and GR and significantly higher than those of WH, BL and BG. Based on the results obtained in this study, it was concluded that the use of green light up to 28 days in combination with blue light stimulated the growth of broiler chickens and manipulation of light colours can be used to improve the welfare and performance of chickens.

The effect of supplementary ultraviolet wavelengths on the performance of broiler chickens

Qualities of the light environment, such as the spectral composition of light, have been shown to impact growth and performance of broiler chickens. UVA light is visible to broiler chickens, whereas UVB wavelengths promote endogenous vitamin D synthesis, which could support their rapid development. The aim of the current study was to investigate the impacts of supplementary UVA and UVB wavelengths on performance indicators of broiler chickens. Day-old Ross 308 chicks (n = 638), reared to a target stocking density of 33 kg/m², were randomly assigned to 1 of 3 lighting treatments: A) White light emitting diode (LED) and supplementary UVA LED lighting (18-h photoperiod); B) White LED with supplementary UVA and UVB fluorescent lighting providing 30 μW/cm² UVB at bird level (lights on for 8 h of the total photoperiod to avoid overexposure of UVB); and C) White LED control group, representative of farm conditions (18-h photoperiod). Mortality was recorded, and broiler chickens were individually weighed at 8, 15, 22, 27, and 34 D of age. Generalized linear models and nonlinear mixed effects models (Gompertz curve) were fitted to determine the effects of UV wavelengths on broiler mortality and growth performance. UV did not impact breast or leg weight of broiler chickens but was associated with differences in mortality, growth, and end weight. Broiler chickens provided with UVA for the full 18-h photoperiod had slower initial growth than control broilers and a reduction in mortality. Results from male broilers reared with supplementary UVA + UVB for 8 h indicated they could reach finishing weights sooner than controls, which supports the potential for UVA + B to improve the growth performance of males. Results suggest that the provision of supplementary UVA + UVB wavelengths may improve the performance of male broiler chickens. The reduction in mortality in the UVA only treatment may warrant further investigation. The inclusion of UV wavelengths within poultry lighting regimes represents a promising area of further study.

Effect of embryonic and post-hatch photo-stimulation with variable light sources on hatchability, endocrine parameters and growth performance in broiler chicken

The objective of this study was to investigate the effects of embryonic and post-hatch photo-stimulation with variable light sources with respect to hatchability parameters, hormonal profile and growth performance of commercial broiler chicken. Uniform sized Cobb broiler eggs (174) were procured from commercial hatchery and incubated in three different groups with arrangement of variable colour light source [Control group; Red light photo-stimulated (675 nm); Green light photo-stimulated group (575 nm) of light]. After hatching, as per earlier grouping, chicks hatched out from respective groups reared under continuous lighting in normal, red, green light up to six week of age in standard management condition in battery cages. The result of the present study indicated that photo-stimulation of incubated eggs with different lights sources had no significant effect on hatchability percentage and hatching time. Green light photo-stimulated group showed significantly higher body weight gain with better feed conversion ratio than red and control groups from 0 to 6 wk of age. Feed intake did not differ significantly within the groups. Green light photo-stimulation promotes growth performance traits via stimulating circulating level of gonadal axis and somatotrophic axis hormone. The results of the study provide evidence that green light photo-stimulation used in this study is beneficial in terms of improved growth performance without affecting hatchability in broiler chicken.

Effects of different light durations during incubation on hatching, subsequent growth, welfare, and meat quality traits among three broiler strains

Present study was aimed to evaluate the hatching traits and subsequent performance of broilers strains under the intermittent and continuous light regime during incubation. In total, 2250 eggs from Hubbard classic, Cobb-500, and Ross-308 strains (750 eggs from each of same age breeders) were incubated under three different light durations. First treatment was the incubation totally under darkness where no light was able to penetrate in the assigned section of machine. In the second treatment, eggs were incubated at 12 h of lightness and 12 h of darkness. In the third treatment, the eggs received lightning of 24 h. Data were collected for hatching traits and hatch window, growth performance, welfare aspects, and meat quality. A two-way factorial analysis was performed using SAS software applying Duncan's multiple range test. The results showed that hatching traits were improved when Hubbard breeder eggs were provided with light period of 12 h. However, gait score was non-significantly different among the treatment. The meat quality was better in Hubbard broilers obtained after 12 h of intermittent light during incubation. Blood biochemistry was also improved in Hubbard broilers of 12 h of light duration. It was concluded that 12 h of light period during incubation is beneficial for getting better hatchability and subsequent performance of Hubbard broilers.

Effects of white, yellow, and blue colored LEDs on milk production, milk composition, and physiological responses in dairy cattle

Light emitting diode (LED) is more energy efficient than incandescent or fluorescent light. This study was to evaluate effects of different colored LEDs on milk production, milk composition, and physiology of Holstein cow. According to milk production and parity, cows (n = 186) were allotted to four treatments: control (natural daylight), white, yellow, and blue LED groups. Of these, 40 cows that had passed 57 day-in-milk were used. Yellow and blue LED groups demonstrated greater rates of decline in milk production than control and white LED groups. At the finish point, milk fat, protein, and lactose contents were the lowest in the blue LED group, whereas milk-urea-nitrogen levels were the highest in the yellow and blue LED groups. Extended exposure to blue LED light lowered antioxidant enzyme activity and insulin-like growth factor-1 levels. Prolactin concentrations were higher in the white and blue LED groups than in the control. Cortisol level was the highest in the blue LED group among the groups. Nonesterified fatty acid levels in the yellow and blue LED groups decreased to the greatest extent compared to the start point. These results suggest that blue LED light can decrease milk production and generate more stress than white and yellow LED lights.

Effects of a two-phase mixed color lighting program using light-emitting diode lights on layer chickens during brooding and rearing periods

The behavior, growth and development, and production performance of poultry are affected by the light environment. The influence of light results from a combination of light sources, light intensity, light color, and the photoperiod regimen. With light-emitting diode (LED) lamps applied in poultry housing systems, specific light colors are desired for each time period for layer chickens. The objective of this study was to investigate the effects of a 2-phase mixed color lighting program (phase 1: blue-green, 1 D-13 wk; phase 2: yellow-orange, 14-20 wk) using LED lights on the blood parameters, skeletal development parameters, and sexual development parameters of caged layer chickens during their brooding and rearing periods. Fifty-two chickens were raised from 1 D to 20 wk of age in each of the 4 treatment groups with 3 replicates, with white (400-700 nm) light at phase 1 and phase 2 (WL treatment as the control); blue-green (435-565 nm) light at phase 1 followed by yellow-orange (565-630 nm) light at phase 2 (BG-YOL treatment); yellow-orange LED (565-630 nm) light at phase 1 and phase 2 (YOL treatment); and blue-green (435-565 nm) light at phase 1 and phase 2 (BGL treatment). The results showed that the serum Ig concentrations of the layer chickens in the BG-YOL treatment and BGL treatment were higher than those in the WL treatment at 13 wk of age (P < 0.05). At the age of 20 wk, the serum glucose concentration levels of the pullets after the WL and BGL treatments were lower than those after the YOL treatment (P < 0.05). Compared with the WL treatment, the YOL treatment significantly increased the bone mineral density of the layer chickens (P < 0.05), and BG-YOL treatment promoted the development of the sexual organs (oviducts and ovaries) of the laying hens at the age of 20 wk (P < 0.05). For the 50% egg production age, the YOL treatment was earlier than the other 3 treatments. This study demonstrated that appropriately staged spectral control using LED lights could have positive effects on the immune performance, bone development, and production performance of caged layer chickens during their brooding and rearing periods.

Impacts of colored light-emitting diode illumination on the growth performance and fecal microbiota in goose

Besides on the reproductive performance, the light also has an important effect on the growth in birds. In the present study, we for the first time investigated effects of colored light-emitting diodes (LED) on both growth performance and fecal microbiota in meat geese. We randomly selected a total of 120 geese at birth (0-day), divided them into 3 groups evenly (i.e., 40 geese each group), and then reared them under 3 colored light-emitting diodes (i.e., blue, red, and white) with the same photoperiod for 9 wk, respectively. We collected fecal samples at the experimental day 35 and 63, respectively. We observed that geese in blue light had higher body weight than those in red and white lights at the early stage of the experiment but showed lower body weight at the late stage, particularly at day 63 (P < 0.05). Interestingly, we found that the relative abundances of 3 dominant bacteria phyla, Firmicutes, Proteobacteria, and Cyanobacteria, were comparable among 3 groups at day 35, while at day 63, the blue light group had the significantly (P < 0.05) lowest and highest abundance for Firmicutes and Proteobacteria, respectively. Functional enrichment analyses revealed that the fecal microbiota in the red light group was mainly involved in metabolism at day 35, whereas at day 63, the fecal microbiota were engaged into membrane transportation and transcription. In contrast, the blue light group had more enriched pathways relevant with membrane transportation at day 63 than day 35 and had several pathways involved in metabolism at day 63 as well. Collectively, our results revealed that the light with different colors affects the growth performance of geese via the gut microbiota, which in turn influences the digestion and absorption of geese.

Effect and molecular regulatory mechanism of monochromatic light colors on the egg-laying performance of Yangzhou geese

Photoperiodic control is essential for manipulating the reproductive performance of avian species. This study was conducted to assess the neuroendocrine mechanisms that regulate reproductive functions of Yangzhou geese when there are different monochromatic light colors from light emitter diode (LED) sources. A flock of geese was divided into four groups with white, red, blue, and green light treatments being imposed. The results indicated that peak laying rates and reproductive performance were greater in geese treated with white or red as compared with blue or green light treatments. The fertilization rate of eggs and hatchability of fertilized eggs were greater with the white or red as compared with blue or green light treatments. There was a greater abundance of OPN5, Dio2, c-Fos, and GnRH-I mRNA in the hypothalamus earlier in the treatment period and abundances of these hypothalamic factors were greater with the white or red light treatments. Abundances of pituitary LH beta and FSH beta mRNA increased at a lesser rate with the blue or green light treatments and were in greater abundances with the white or red light treatments. The lighting regimen also resulted in photo-refractoriness with there being greater abundances of GnIH, VIP, and PRL mRNA with the use of white or red light treatments. The results indicate that the use of white or red monochromatic lights while imposing a long photoperiod of 11 h daily could result in sustaining functions of the reproductive system of Yangzhou geese for considerably longer times, thus, resulting in greater egg-laying performance.

The effect of different wavelengths of light during incubation on the development of rhythmic pineal melatonin biosynthesis in chick embryos

Rhythmic pineal melatonin biosynthesis develops in chick embryos incubated under a light (L)-dark (D) cycle of polychromatic white light. The spectral sensitivity of the embryonic pineal gland is not known and was investigated in this study. Broiler breeder eggs (Ross 308, n=450) were incubated under white, red, green or blue light under the 12L : 12D cycle. Melatonin was measured in extracts of pineal glands by radioimmunoassay. The daily rhythm of pineal melatonin levels in 20-day-old chick embryos was confirmed during the final stages of embryonic life under all four wavelengths of light with expected higher concentrations during dark- than light-times. The highest pineal melatonin levels were determined in chick embryos incubated under red and white light and lower levels under green light. The incubation under blue light resulted in the lowest melatonin biosynthesis. Pineal melatonin concentrations increased substantially on post-hatching day two compared with pre-hatching levels and we did not find differences between birds incubated and kept in either white or green light. Our results demonstrate a selective sensitivity of the chick embryo pineal gland to different wavelengths of light. Rhythmic melatonin production is suggested as a possible mechanism, which transfers information about the quality of ambient light to the developing avian embryo.

Evaluation of the Impact of Light Source on Reproductive Parameters in Laying Hens Housed in Individual Cages

Higher light wavelengths have been shown to stimulate extra-retinal photoreceptors more efficiently than lower wavelengths to promote reproduction in poultry. We developed a light emitting diode (LED) bulb that emits 60% of its light in the red spectrum (LED-R), and evaluated the effects of different light sources on growth and reproduction in commercial layer hens. Three rooms equipped with either 100W incandescent, 15W compact fluorescent (CFL), or 10W LED-R bulbs were populated with 96 Lohmann LSL-Lite layers housed in individual cages from 14 to 69 weeks of age (woa). Pullets were initially maintained on a 10-h photoperiod, then photostimulated at 18 woa. Surprisingly, regardless of the light source, plasma levels of estradiol peaked at 16 woa, 2 weeks before photostimulation, and egg-laying was initiated at 19 woa. As a direct correlation between age at first egg and body weight was identified, metabolic cues most likely served as a primary trigger to initiate sexual maturation prior to photostimulation. Overall egg production and cumulative egg numbers were similar among treatments. Interestingly, a second increase in estradiol was observed at 52 woa under all treatments, suggesting an additional ovarian stimulation, possibly associated with an additional follicular recruitment at that age. Overall, changes in estradiol concentrations were more pronounced in hens maintained under LED-R light than in hens exposed to incandescent and CFL, especially for the second increase, suggesting that a higher amount of red light leads to stronger ovarian activity. Maintaining hens under LED-R bulbs also resulted in lower feed consumption, which combined with the lower energy consumption of LED-bulbs (LED-R: 306 kW; incandescent: 2,514 kW; CFL: 422 kW) could reduce the production cost.

Layer pullet preferences for light colors of light-emitting diodes

Light colors may affect poultry behaviors, well-being and performance. However, preferences of layer pullets for light colors are not fully understood. This study was conducted to investigate the pullet preferences for four light-emitting diode colors, including white, red, green and blue, in a lighting preference test system. The system contained four identical compartments each provided with a respective light color. The pullets were able to move freely between the adjacent compartments. A total of three groups of 20 Chinese domestic Jingfen layer pullets (54 to 82 days of age) were used for the test. Pullet behaviors were continuously recorded and summarized for each light color/compartment into daily time spent (DTS), daily percentage of time spent (DPTS), daily times of visit (DTV), duration per visit, daily feed intake (DFI), daily feeding time (DFT), feeding rate (FR), distribution of pullet occupancy and hourly time spent. The results showed that the DTS (h/pullet·per day) were 3.9±0.4 under white, 1.4±0.3 under red, 2.2±0.3 under green and 4.5±0.4 under blue light, respectively. The DTS corresponded to 11.7% to 37.6% DPTS in 12-h lighting periods. The DTV (times/pullet·per day) were 84±5 under white, 48±10 under red, 88±10 under green and 94±8 under blue light. Each visit lasted 1.5 to 3.2 min. The DFI (g/pullet·per day) were 27.6±1.7 under white, 7.1±1.6 under red, 15.1±1.1 under green and 23.1±2.0 under blue light. The DFT was 0.18 to 0.65 h/pullet·per day and the FR was 0.57 to 0.75 g/min. For most of the time during the lighting periods, six to 10 birds stayed under white, and one to five birds stayed under red, green and blue light. Pullets preferred to stay under blue light when the light was on and under white light 4 h before the light off. Overall, pullets preferred blue light the most and red light the least. These findings substantiate the preferences of layer pullets for light colors, providing insights for use in the management of light-emitting diode colors to meet pullet needs.

The quantitative models for broiler chicken response to monochromatic, combined, and mixed light-emitting diode light: A meta-analysis

Although many experiments have been conducted to clarify the response of broiler chickens to light-emitting diode (LED) light, those published results do not provide a solid scientific basis for quantifying the response of broiler chickens. This study used a meta-analysis to establish light spectral models of broiler chickens. The results indicated that 455 to 495 nm blue LED light produced the greatest positive response in body weight by 10.66% (BW; P < 0.001) and 515 to 560 nm green LED light increased BW by 6.27% (P < 0.001) when compared with white light. Regression showed that the wavelength (455 to 660 nm) was negatively related to BW change of birds, with a decrease of about 4.9% BW for each 100 nm increase in wavelength (P = 0.002). Further analysis suggested that a combination of the two beneficial light sources caused a synergistic effect. BW was further increased in birds transferred either from green LED light to blue LED light (17.23%; P < 0.001) or from blue LED light to green LED light (17.52%; P < 0.001). Moreover, birds raised with a mixture of green and blue LED light showed a greater BW promotion (10.66%; P < 0.001) than those raised with green LED light (6.27%). A subgroup analysis indicated that BW response to monochromatic LED light was significant regardless of the genetic strain, sex, control light sources, light intensity and regime of LED light, environmental temperature, and dietary ME and CP (P > 0.05). However, there was an interaction between the FCR response to monochromatic LED light with those covariant factors (P < 0.05). Additionally, green and yellow LED light played a role in affecting the meat color, quality, and nutrition of broiler chickens. The results indicate that the optimal ratio of green × blue of mixed LED light or shift to green-blue of combined LED light may produce the optimized production performance, whereas the optimal ratio of green/yellow of mixed or combined LED light may result in the optimized meat quality.

Effect of fluorescent vs. poultry-specific light-emitting diode lights on production performance and egg quality of W-36 laying hens

More energy-efficient, durable, affordable, and dimmable light-emitting diode (LED) lights are finding applications in poultry production. However, data are lacking on controlled comparative studies concerning the impact of such lights during the pullet rearing and subsequent laying phase. This study evaluated two types of poultry-specific LED light (PS-LED) vs. fluorescent light (FL) with regards to their effects on hen laying performance. A total of 432 Hy-Line W-36 laying hens were tested in two batches using four environmental chambers (nine cages per chamber and 6 birds per cage) from 17 to 41 weeks of age (WOA). Dim-to-red PS-LED and warm-white FL were used in the laying phase. The hens had been reared under a dim-to-blue PS-LED or a warm-white FL from 1 to 16 WOA. The measured performance variables included 1) timing of sexual maturity, 2) egg production performance, 3) egg quality, and 4) egg yolk cholesterol. Results showed that the two types of light used during the laying phase had comparable performance responses for all response parameters (P > 0.05) with a few exceptions. Specifically, eggs laid from hens in the PS-LED treatment had lower shell thickness (P = 0.01) and strength (P = 0.03) than those in the FL treatment at 41 WOA. The two types of light used during the rearing phase did not influence the 17 to 41 WOA laying performance, except that hens reared under the PS-LED laid eggs with lower shell thickness (P = 0.02) at 32 WOA as compared to hens reared under the FL. This study demonstrates that the emerging poultry-specific LED lights yield comparable production performance and egg quality of W-36 laying hens to the traditional fluorescent lights.