Photoperiods for broiler breeder females during the laying period

Effect of light sources with and without UVA on selected behavior and health indicators in commercial broiler breeder flocks

As new light sources are being developed for poultry houses, systematic investigations on how these influence behavior and health in commercial broiler breeders are needed. Therefore, the aim of this study was to investigate the effects of 2 light sources (Evolys with UVA (LED) and Biolux 965 (CFL)) on the behavior and health of 2 broiler breeder hybrids during the production period. Eight commercial breeder flocks (Ross 308 n = 4, Hubbard JA757 n = 4) with Evolys (Ross n = 2, Hubbard n = 2) or Biolux (Ross n = 2, Hubbard n = 2) were visited at 25 and 50 wk of age to record behavior and health. Behaviors included resting, locomotion, exploration, comfort, feather pecking, aggression, and mating, while health was recorded by a transect walk, scoring the number of birds observed with: feather loss (FL) on head, back/wings, breast, and tail, wounds on head, back/wings, and tail, dirty plumage, lameness, sickness, and dead birds. The most common behaviors were resting, locomotion, comfort, and exploration, and these were influenced by a 3-way interaction between light source, hybrid, and age. Light source did not affect behavior in Hubbard birds at any age. In contrast, Ross birds housed in Evolys rested less at 50 wk compared to Biolux (P = 0.04) and showed more locomotion at 25 wk in Biolux compared to Evolys (P < 0.0001). Ross birds at 25 wk explored more in Biolux compared to Evolys (P = 0.0007). More comfort behavior was performed in Evolys in 25-wk-old Ross (P = 0.002), but not at 50 wk. These inconsistencies might be due to low sample size, which is a limitation in the study. The most common health indicators were FL on back/wings (mean 3.9%), wounds on back/wings (mean 0.22%), and FL head (mean 0.18%), with no effect of light source, hybrid, or age on FL back/wings, breast, or tail, but with increased FL on the head with increased age (P = 0.0008). In conclusion, the behavior of Ross birds seemed to be affected by light source, while the Hubbard birds were not. Light source had minor effects on the selected health indicators in the 2 hybrids.

Nest preference and laying duration traits to select against floor eggs in laying hens

BACKGROUND

Floor eggs, which are defined as eggs that hens lay off-nest, are a major issue in cage-free layer poultry systems. They create additional work for farmers because they must be collected by hand. They are also usually soiled or broken, which results in economic losses. Nonetheless, knowledge about the genetics of nesting behavior is limited. The aim of this study was to estimate genetic parameters for traits related to nest preference for laying and to time spent in the nests used for laying (laying duration).

METHODS

Two pure lines of laying hens were studied: 927 Rhode Island Red and 980 White Leghorn. Electronic nests were used to record the nesting behavior of these hens in floor pens from 24 to 64 weeks of age. Nest preference was studied based on the mean distance between nests used for laying and the percentage of nests used for laying. Laying duration was studied based on mean laying duration, mean duration in the nest before laying, and mean duration in the nest after laying. Genetic parameters were estimated for each line using a restricted maximum-likelihood method applied to a pedigree-based multi-trait animal model.

RESULTS

Estimates of genetic parameters were similar for the two lines. Estimates of heritability ranged from 0.18 to 0.37 for nest preference traits and from 0.54 to 0.70 for laying duration traits. Estimates of genetic correlations of these traits with clutch number or mean oviposition time were favorable. Positive genetic correlations were estimated between nest preference and laying rate in the nests or nest acceptance for laying (+ 0.06 to + 0.37).

CONCLUSIONS

These results show that genetics influences traits related to nest preference and laying duration. Selecting hens that have no preference for particular nests and spend little time laying in the nests could help optimize nest use, reduce their occupation rate, and thus decrease the incidence of floor eggs in cage-free systems. Genetic correlations of these traits with other traits of interest related to hen welfare and egg quality have yet to be estimated.

Nest acceptance, clutch, and oviposition traits are promising selection criteria to improve egg production in cage-free system

In cage-free systems, laying hens must lay their eggs in the nests. Selecting layers based on nesting behavior would be a good strategy for improving egg production in these breeding systems. However, little is known about the genetic determinism of nest-related traits. Laying rate in the nests (LRN), clutch number (CN), oviposition traits (OT), and nest acceptance for laying (NAL) of 1,430 Rhode Island Red (RIR) hens and 1,008 White Leghorn (WL) hens were recorded in floor pens provided with individual electronic nests. Heritability and genetic and phenotypic correlations of all traits were estimated over two recording periods-the peak (24-43 weeks of age) and the middle (44-64 weeks of age) of production-by applying the restricted maximum likelihood method to an animal model. The mean oviposition time (MOT) ranged from 2 h 5 min to 3 h and from 3 h 35 min to 3 h 44 min after turning on the lights for RIR and WL hens, respectively. The mean oviposition interval ranged from 24 h 3 min to 24 h 16 min. All heritability and correlation estimates were similar for RIR and WL. Low to moderate heritability coefficients were estimated for LRN (0.04-0.25) and moderate to high heritability coefficients for CN and OT (0.27-0.68). CN and OT were negatively genetically correlated with LRN (-0.92 to -0.39) except during peak production for RIR (-0.30 to +0.43). NAL was weakly to moderately heritable (0.13-0.26). Genetic correlations between NAL and other traits were low to moderate (-0.41 to +0.44). In conclusion, CN and OT are promising selection criteria to improve egg production in cage-free systems. NAL can be also used to reduce the number of eggs laid off-nest in these breeding systems. However, variability in MOT must be maintained to limit competition for the nests.

Intermittent lighting regime as a tool to enhance egg production and eggshell thickness in Rhode Island Red laying hens

Influences of intermittent light regime as a tool to enhance egg production, egg quality, and blood parameters of laying hens were investigated. A total of 270 hens of Rhode Island Red (during 20 to 36 wk of age) were used to investigate the effects of intermittent light regime in completely randomized design. The birds were divided into 3 equal groups (6 replicates of 15 birds each) and housed in floor pens. The first group was served as non-treated control (C) and was exposed to continuous and constant light for 16 h light/day throughout the experimental period. Whereas, birds of the other groups were exposed to intermittent lights for 20 min/h + 40 min of constant light (T1; FLASH20) and 40 min/h + 20 min of constant light (T2; FLASH40) during the 16 h of light period. Hens of T1 group showed significantly (P ≤ 0.05) the highest concentration of total antioxidant capacity and the lowest one of malondialdehyde in comparison with the other groups. Hens of T1 group had significantly (P ≤ 0.05) the greatest egg laying rate and egg mass in comparison with the other counterparts. Feed consumption was similar in the groups under study. Hens exposed to FLASH20 had the lowest (P ≤ 0.05) FCR when compared with the other treatments. Eggs produced from hens exposed to FLASH20 had the highest value of shell thickness followed by the control and then that of those exposed to FLASH40. There were insignificant differences among the treatments in body weight of hens and all of other egg quality and egg problem traits. In conclusion, intermittent light regime of 20 min/h was the most efficient in comparison with the other ones. Finally, intermittent light regime of 20 min/h during laying period (during 20 to 36 wk of age) is highly recommended.

Analyses of mathematical models for Yangzhou geese egg-laying curves

Mathematical models of the egg-laying curves for Yangzhou geese exposed to both natural and artificial photoperiods were established to optimise the parameters for maximising geese reproductive performance and for the development of precision feeding methods. With the natural photoperiod, egg-laying starts in autumn when daily photoperiod decreases, but accelerates after the winter solstice, and reaches the peak in spring when photoperiod increases. An accumulating model was constructed based on the hypothesis that the egg-laying capacity of geese was determined by two components of the photoperiod: photo-stimulation and photo-inhibition. In addition, a second segmented model was constructed based on the hypothesis that the photo-stimulation only occurred with lengthening photoperiods after the winter solstice, and the lesser laying rate in autumn could be attributed to the non-photo-dependent animal-husbandry technologies. This model consists of a logistic model before the winter solstice, and an accumulating model after this solstice. The use of the logistic and accumulating resulted in more precise predictions that occurred with use of Model 1 with a greater R² and lesser RMSE, AIC and BIC. Likewise, the egg-laying curves when there was consideration of artificial photoperiods could also be constructed with consideration of stimulatory and inhibitory photoperiodic effects. The model consists of an initial logistic and subsequently a quadratic polynomial model. With use of this model, there is consideration of changes in egg-laying patterns when there is a fixed photoperiod, with the model parameters reflecting the effects by photoperiod control-programs and age of the geese. In conclusion, new mathematical models have been developed to best fit egg-laying curves when there are both natural and artificial photoperiods. These models can contribute to development of precision-feeding technologies for breeding geese in future.

Characterization of the relations between morphology and physiological status of the pineal gland in connection with the somatic development level in turkeys reared in Romania

This research started from the premises of the existence of some possible relationships between indole and pineal peptide hormones and the somatic development, with participation of hypothalamic-pituitary complex. Experimental factors, which were the subject of the present paper, influenced the dynamics of corporal mass and fodder consumption, leading to the occurrence of some important structural modifications at the level of pineal gland. The exposure of the individuals to continuous light (photic pinealectomy) produces increases in corporal mass, showing the involvement of the pineal gland in neuro-endocrine-metabolic reactions, which contributes to the maintenance of homeostatic balance, including somatic ones. Biological material was represented by a number of 50 individuals belonging to B.U.T. Big 6 hybrid, reared on soil, on a permanent litter, which could assure the expanding of knowledge area regarding the relation between rearing technology, modulation of some microclimate parameters and growing performances. Were also realised cytometric and hystometric muscular determinations.

Detection of long-term influence of prenatal temperature stimulation on hypothalamic type-II iodothyronine deiodinase in juvenile female broiler chickens using a novel immunohistochemical amplification protocol

It has been clearly shown that early environmental stimulation may have long-lasting influence on body functions. Because of the strong relationship between thermoregulation and other homeostatic linked physiological parameters, perinatal thermal manipulation will also have an impact on other body functions like reproduction. As a maturation stimulant for later reproductive performance, hypothalamic type-2 iodothyronine deiodinase (Dio2) expression was investigated in 35day old immature female broilers with and without embryonic temperature stimulation. For the first time, human-specific Dio2 primary antibodies combined with additional amplification enabled the immunohistochemical detection of hypothalamic Dio2 protein in birds. The novel protocol includes an additional amplification step involving swine-anti-rabbit/mouse/goat antibodies against both goat anti-Dio2 primary and rabbit anti-goat biotinylated secondary commercial antibodies in the standard diaminobenzidine protocol. However, significant Dio2 expression was exclusively found in perinatally short-term temperature stimulated hens. Caudal but not rostral hypothalamic slices revealed that elevating incubation temperature by 1°C for 2h daily, from day 18 of embryonic development until hatching, induced a statistical significant expression of Dio2 within the subcommisural organ and the median eminence. This ample expression of Dio2 protein within caudal but not rostral hypothalamic slices of embryonic temperature stimulated chickens, leads to the assumption of a novel physiological prospective for embryonic thermal manipulation involving the suppression of thyroid hormone and the boosting of hypothalamic Dio2-induced FSH secretion to considerably advance the age of photoinduced egg production. It could be also of practicable relevance for broiler breeder females, and needs further investigations.

A model for an economically optimal replacement of a breeder flock

A deterministic model is developed to support the tactical and operational replacement decisions at broiler breeder farms. The marginal net revenue approach is applied to determine the optimal replacement age of a flock. The objective function of the model maximizes the annual gross margin over the flock's production cycle. To calculate the gross margin, future egg production, fertility, or hatchability of the eggs, revenues and variable costs of a flock were estimated. For tactical decisions, the optimal laying length is the age at which the average gross margin of an average flock is maximal. For operational decisions, a flock should be replaced when the marginal gross margin of a replaceable flock is less than the average gross margin of an average flock. To demonstrate the model, a broiler breeder flock from a Dutch breeder farm was used. A sensitivity analysis showed that the optimal replacement decision, for both tactical and operational management, is sensitive to the decrease in the weekly egg production after the peak and the prices of feed and hatching eggs. The effect of the decrease in weekly fertility after the peak on the replacement decision is related to the payment system for hatching eggs.

A genome-wide SNP scan reveals novel loci for egg production and quality traits in white leghorn and brown-egg dwarf layers

Availability of the complete genome sequence as well as high-density SNP genotyping platforms allows genome-wide association studies (GWAS) in chickens. A high-density SNP array containing 57,636 markers was employed herein to identify associated variants underlying egg production and quality traits within two lines of chickens, i.e., White Leghorn and brown-egg dwarf layers. For each individual, age at first egg (AFE), first egg weight (FEW), and number of eggs (EN) from 21 to 56 weeks of age were recorded, and egg quality traits including egg weight (EW), eggshell weight (ESW), yolk weight (YW), eggshell thickness (EST), eggshell strength (ESS), albumen height(AH) and Haugh unit(HU) were measured at 40 and 60 weeks of age. A total of 385 White Leghorn females and 361 brown-egg dwarf dams were selected to be genotyped. The genome-wide scan revealed 8 SNPs showing genome-wise significant (P<1.51E-06, Bonferroni correction) association with egg production and quality traits under the Fisher's combined probability method. Some significant SNPs are located in known genes including GRB14 and GALNT1 that can impact development and function of ovary, but more are located in genes with unclear functions in layers, and need to be studied further. Many chromosome-wise significant SNPs were also detected in this study and some of them are located in previously reported QTL regions. Most of loci detected in this study are novel and the follow-up replication studies may be needed to further confirm the functional significance for these newly identified SNPs.