Effects ofad libitumfeeding on performance of different strains of broiler breeders

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

Sexual maturity is a crucial factor in the formation and development of poultry reproductive capacity. The nutritional status has been confirmed to play an important role in the regulation of sexual maturity. To investigate the effect of dietary energy levels on sexual maturity in chicken, diets with 3 energy levels (group L: 2,573 kcal/kg, group C: 2,836 kcal/kg, group H: 3,122 kcal/kg) were implemented to feed Guangyuan Gray chickens. During this trial, body weight, body size, organ development, sexual maturity, reproductive performance and blood biochemical parameters were monitored. The earlier sexual maturity was observed in group H, as well as a heavier first egg weight, larger interpubic distance and higher total cholesterol (T-CHO) content at sexual maturity. The dietary energy levels had no significant effect on body weight at first egg and egg production at 300 d of age. Although dietary energy levels had a significant effect on body weight, comb length, tibia length and girth, abdominal fat weight, oviduct weight and length, T-CHO, triglyceride (TG) content and estradiol (E2) level during the rearing period. No significant difference of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) level among 3 groups was observed during the trial. The dietary energy levels had effects on mRNA expression of GnRH, estrogen receptor 1 (ESR1), estrogen receptor 2 (ESR2) in hypothalamus, gonadotropin inhibitory hormone receptor (GnIHR) in pituitary and luteinizing hormone receptor (LHR), ESR2 in ovary. The GnIHR/GnRHR ratio in pituitary was higher before sexual maturity and decreased at sexual maturity. The results of correlations analysis found that all the body size, carcass traits, serum biochemical parameters negatively correlated with age at first egg except for interpubic distance and serum blood glucose content. Collectively, dietary energy levels had effects on sexual maturity of chicken, which may be achieved by affecting body weight, gonad development, endocrine and the mRNA expression of genes related to hypothalamus-pituitary-gonad axis. These results further set our understanding of how dietary energy regulates sexual maturity.

Effect of restricted feeding on hen performance, egg quality and organ characteristics of individual laying hens

This study was to assess the impact of permanent or temporary restricted feeding on laying hen production traits, physiology, and egg quality. Two hundred and forty individually housed ISA Brown hens were monitored across 2 phases, assigned to 3 treatments: ad libitum feeding (ALF), temporary restricted feeding (TRF) and permanent restricted feeding (PRF), n = 80 hens per treatment. In Phase 1 (P1), 22 to 40 weeks, the TRF and PRF hens were offered 115 g of feed daily. In Phase 2 (P2), 41 to 46 weeks, the TRF hens were transitioned to ALF status while the ALF and PRF hens remained as in P1. From 35 to 40 weeks, eggs were collected once weekly from 15 hens per treatment and assessed for differences in albumen, yolk, and shell variables. At 45 weeks, 10 hens each from the ALF and PRF groups were euthanized and differences in organ characteristics were assessed. In P1, feed intake, feed to egg conversion ratio and body weight (BW) change were lower (P < 0.01), while albumen height and Haugh unit were higher (P < 0.01) in both PRF and TRF hen treatments compared to hens allocated the ALF treatment. In P2, TRF and ALF hens had a higher egg production and egg mass than PRF (P < 0.01) than ALF. Body weight change in P2 was higher in TRF and similar in both ALF and PRF, while feed intake and feed conversion ratio were higher in TRF followed by ALF and least in the PRF treatment group (P < 0.01). At 45 weeks ALF hens had a greater abdominal fat pad weight and fatty liver haemorrhagic syndrome lesion score compared to PRF. Restricting hens to 115 g of feed per day from point of lay restrained BW, improved feed conversion ratio and albumen quality and reduced abdominal fat pad deposition and clinical signs of fatty liver haemorrhagic syndrome in individually housed laying hens.

Heat Shock Protein Response to Stress in Poultry: A Review

Compared to other animal species, production has dramatically increased in the poultry sector. However, in intensive production systems, poultry are subjected to stress conditions that may compromise their well-being. Much like other living organisms, poultry respond to various stressors by synthesising a group of evolutionarily conserved polypeptides named heat shock proteins (HSPs) to maintain homeostasis. These proteins, as chaperones, play a pivotal role in protecting animals against stress by re-establishing normal protein conformation and, thus, cellular homeostasis. In the last few decades, many advances have been made in ascertaining the HSP response to thermal and non-thermal stressors in poultry. The present review focuses on what is currently known about the HSP response to thermal and non-thermal stressors in poultry and discusses the factors that modulate its induction and regulatory mechanisms. The development of practical strategies to alleviate the detrimental effects of environmental stresses on poultry will benefit from detailed studies that describe the mechanisms of stress resilience and enhance our understanding of the nature of heat shock signalling proteins and gene expression.

Changes in body composition and energetic efficiency in response to growth curve and dietary energy-to-protein ratio in broiler breeders

Body composition plays an important role in reproduction in broiler breeders. The aim of this study was to evaluate the dynamics in body composition and energetic efficiency in broiler breeders, using different dietary strategies. About 1,536-day-old pullets were randomly allotted to 24 pens in a 2 × 4 factorial design with 2 growth curves (standard or elevated (+15%)) and 4 diets, with a step-wise increment in energy (96, 100, 104, and 108% apparent metabolizable energy nitrogen corrected [AME_n]) fed on a pair-gain basis. Body composition was determined at 10 time points from 0 to 60 wk of age. Body protein mass was linearly related to body weight (BW) in growing breeders, which can be expressed as -6.4+0.184*BW (R² = 0.99; P < 0.001). Body fat mass was exponentially related to BW in growing breeders, which can be expressed as -42.2+50.8*1.0006^BW (R² = 0.98; P < 0.001). A higher energy-to-protein ratio resulted in higher body fat mass at the same BW (P < 0.001). Sexual maturation was related to body protein mass at 21 wk of age, where each 100 g of body protein mass extra advanced sexual maturation by 5.4 d (R² = 0.83). Estimates of energetic efficiency for growth (k_g) and egg production (k_e) appeared not constant, but varied with age in a quadratic manner between 0.27 and 0.54 for k_g and between 0.28 and 0.56 for k_e. The quadratic relationship could be expressed as k_g=0.408-0.0319*Age+0.00181*Age² (R² = 0.72; P < 0.001) and k_e=-0.211+0.034*Age-0.00042*Age² (R² = 0.46; P < 0.001). Body protein mass in broiler breeders is tightly regulated and mainly depended on BW and seems to be the main determinant for sexual maturation. Body fat mass is exponentially related to BW, where an increase in dietary energy-to-protein ratio results in a higher body fat mass. Treatments had minimal effects on estimated energetic efficiencies in breeders.

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.

In Pursuit of a Better Broiler: Welfare and Productivity of Slower-growing Broiler Breeders during Lay

Current commercial strains of broiler breeders display reproductive dysregulation when fed to satiety, but they can achieve optimal hatching egg production under feed restriction. However, chronic feed restriction in broiler breeders is a welfare concern due to physiological and behavioral signs of hunger, lack of satiety, and frustrated feeding motivation. The purpose of this study was to assess the welfare and productivity of slower-growing broiler breeders during lay. A total of 336 broiler breeders from 5 strains of slower-growing broiler breeders (3 female strains: 100 hens per strain, and 2 male strains: 12 and 24 roosters per strain) were kept in 12 identical pens throughout lay, 4 pens per combination of roosters and hens: A hens with Y roosters, B hens with Y roosters, and C hens with X roosters. According to guidelines, strain B and C hens and X roosters were slower growing strains and strain A hens and Y roosters were intermediate growing strains. Egg production was recorded daily, and settable eggs laid at 30, 40, and 50 wk of age were incubated to hatch. Growth rate, feed and water intake, and welfare indicators (feeding motivation, behavior, and physical assessment: feather coverage, foot and leg health, and keel bone status) were recorded during lay. Additionally, a subsample of 5 hens per pen was dissected for anatomical analyses. Laying rate started and peaked earlier in B hens than in A hens and remained above 70% in both strains, yielding high cumulative egg production (>165 eggs/hen) until 53 wk of age. Until 50 wk of age, fertility and hatched of fertile was high in slower growing broiler breeders, on average, above 95 and 80%, respectively. Compared to A hens, B and C hens had better feather coverage, lower feeding motivation, and lower daily water and feed intake. Results of this study suggest that slower growing broiler breeders show reduced signs of poor welfare and improved productivity during lay although susceptibility to obesity-related problems on laying rate may be strain-specific.

Feeding level is associated with altered liver transcriptome and follicle selection in the hen

Genetic selection for particular traits in domestic animals may have altered the optimal feedback regulation among systems regulating appetite, growth, and reproduction. Broiler breeder chickens have been selected for fast and efficient growth and, unless feed restricted, consume excessively resulting in poor reproductive efficiency. We examined the effect of dietary treatment in full fed (FF) and restricted fed (RF) broiler breeder hens on ovarian responses and on liver morphology and transcriptome associated with reproductive function. Although FF broiler breeder hens had lower egg production (p < 0.01), the total number of ovarian follicles >8 mm (p < 0.01), 6-8 mm (p < 0.03), and 3-5 mm (p < 0.04) were greater in FF hens compared to RF hens. There was a large amount of lipid accumulation in the liver of FF hens and differential gene analysis yielded 120 genes that were differentially expressed >2-fold in response to feeding level (p < 0.01; FDR < 0.05). Elevated T3 may indicate that general metabolism was affected by diet and GHR (p < 0.01) and IGF1 (p < 0.04) mRNA expression were both greater in the liver of FF hens as compared to RF hens. It is likely that selection for increased growth, associated with enhanced activity of the IGF1 system, has altered nutritional coupling of feed intake to follicle development.

Welfare and performance of slower growing broiler breeders during rearing

Current commercial strains of broiler breeders can only achieve an optimal reproductive performance under feed restriction. However, chronic feed restriction in broiler breeders is a welfare concern because of physiological and behavioral signs of hunger, lack of satiety, and frustrated feeding motivation. The objective of this research was to assess the welfare and performance of slower growing broiler breeders during rearing. A total of 360 broiler breeder chicks from 3 female strains (100 chicks per strain) and 2 male strains (20 and 40 chicks per strain) were raised in four identical pens per strain. Strain B and C pullets and X cockerels were slower growing strains, and strain A pullets and Y cockerels were intermediate growing strains. Birds were weighed and scored individually for footpad lesions, hock burns and feather coverage. Data were analyzed using generalized linear mixed models with pen nested in the models and age as a repeated measure. Compared to B and C pullets, strain A pullets grew faster, had poorer body weight uniformity, and started feed restriction 2 wk earlier to control growth rate. Strain A pullets also had higher feeding rate at 3 and 5 wk, higher water intake at 4 and 5 wk, and higher prevalence of footpad lesions at 6 wk than the other pullet strains. Fault bars in wing feathers (an indicator of chronic stress) were more numerous in A pullets than in B and C pullets. Our results indicate that pullets showed little feather coverage loss during early rearing and had good body weight uniformity and low cumulative feed intake at the end of rearing. Slower growing broiler breeders may still require some degree of feed restriction to control growth rate, and strains with lower feed restriction exhibited lower signs of feeding frustration and high body weight uniformity.

Body weight, organ development and jejunal histomorphology in broiler breeder pullets fed n-3 fatty acids enriched diets from hatch through to 22 weeks of age

Dietary long chain polyunsaturated n-3 fatty acids (n-3 FA) may be beneficial to broiler breeder (BB) development. Therefore, the effects of feeding sources of docosahexaenoic acid (DHA) and α-linolenic acid (ALA) from hatch through to 22 weeks of age (woa) on growth, organ weight, and jejunal histomorphology were investigated. A total of 588-day-old Ross × Ross 708 BB were reared on one of 3 diets: 1) control, corn-soybean meal diet, 2) Control + 1% microalgae (DMA, Aurantichytrium limacinum), as a source of DHA and 3) Control + 2.50% co-extruded full fat flaxseed and pulse mixture (FFF, 1:1 wt/wt), as a source of ALA. Diets DMA and FFF had similar total n-3 and n-6: n-3 ratio. Diets were allocated to floor pens (28 birds/pen) to give 9 or 6 replicates per diet for control or DMA and FFF, respectively and fed according to breeder curve in 3 phases: starter (0-4 woa), grower (5-19 woa), and pre-breeder (20-22 woa). Individual body weight (BW) was taken weekly and 6 birds/pen necropsied at 5 and 12 woa for gastrointestinal, spleen, bursa, and liver weight and samples for jejunal histomorphology. There was no (P > 0.05) diet effect on growth by 20 woa. With exception of 5 woa, pullets fed DMA showed (P < 0.001) lower BW coefficient of variation (C.V.) than pullets fed control between 2 and 7 woa. However, pullets fed DMA had higher BW CV at 20 woa than birds fed either control or FFF. At 5 woa, birds fed DMA had taller (P ≤ 0.01) villi and deeper crypt than birds fed either control or FFF but VH or CD were similar (P > 0.05) between CON and FFF pullets. At 12 woa, birds fed FFF had taller VH than birds fed control diet but similar (P > 0.05) to that of birds fed DMA. Therefore, different responses to sources of omega-3 FA may implicate other components, however, the BW uniformity and intestinal histomorphology responses suggested benefits of feeding omega-3 FA during rearing.

Effects of Nutritional Restriction during Laying Period of Fat and Lean Line Broiler Breeder Hens on Meat Quality Traits of Offspring

Simple Summary

The meat quality of livestock products is widely appreciated. Maternal nutrition can affect the deposition of nutrients in eggs, and then change the apparent metabolism, development process, and performance of offspring. Our research indicated that meat quality traits are also affected by maternal nutritional level and are related to the nutritional requirements of different genotypes. Some of the effects disappeared at the end of the growth stage. These situations remind poultry producers to consider the impact of feed restrictions on the quality of meat for future generations.

Abstract

The offspring meat quality of hens undergoing a 25% dietary restriction treatment during the laying period were evaluated in fat and lean line breeder. A total of 768 female birds (384/line) were randomly assigned to four groups (12 replicates/group, 16 birds/replicates). Maternal feed restriction (MFR) and normal started at 27 weeks of age. Offspring broilers were fed ad libitum. The offspring meat quality traits and muscle fiber morphology in different periods were measured. At birth, significant interactions were found on breast muscle fiber morphology (p < 0.05). At 28 days, MFR decreased breast water content and increased thigh crude fat content, and significant interactions were observed on breast crude fat and protein contents (p < 0.05). At 56 days, MFR affected morphology of peroneus longus muscle tissue, and significant interactions were found on thigh redness at 48 h and amino acid contents in breast and thigh muscle (p < 0.05). Overall, MRF may lead to offspring birth sarcopenia. Such offspring grow more easily to deposit fat in a nutritious environment, but they will self-regulate adverse symptoms during growth and development. The two lines respond differently to maternal nutritional disturbance due to different nutritional requirements and metabolic patterns.

Timing of growth affected broiler breeder feeding motivation and reproductive traits

The amount and timing of growth are important factors that affect age at first egg, body conformation, reproductive performance, and hunger in broiler breeders. To investigate the effect of growth pattern on feeding motivation and reproductive performance, 10 unique growth trajectories were designed with 2 levels of the amount of early growth and 5 levels of timing of growth around puberty. A 3-phase Gompertz model that described growth in phase 1 (prepubertal), phase 2 (pubertal), and phase 3 (postpubertal) was used to design the growth trajectories. Second growth phase inflection point (I₂) was advanced by 0, 5, 10, 15, or 20% of the coefficient estimated from the breeder-recommended target BW. The growth trajectories were designed with 2 discrete levels of total gain in the prepubertal phase (g₁); g₁ was either the prepubertal phase gain coefficient, estimated from the breeder-recommended BW (Standard g₁) target, or 10% higher (High g₁). Forty females were randomly assigned to the growth trajectories using a precision feeding (PF) system. Analysis of covariance was conducted on dependent variables in ten 4-wk periods with g₁ and periods as discrete fixed effects, I₂ as a continuous fixed effect, and age as a random effect. Differences were reported at P ≤ 0.05. For every week of earlier I₂, body weight at photostimulation (BWPS) increased by 126 g; BW at first egg (BWFE) increased by 94 g; 24 wk shank length increased by 0.038 and 1.495 mm in the Standard g₁ and High g₁ treatments; 24 wk body fat increased by 0.38%; pullets came to lay earlier by 0.49 d; egg weight (EW) increased by 0.27 g; egg production and egg mass (EM) increased by 0.33 egg/hen/d and 0.916 g/d in the High g₁ treatment but decreased by 0.27 egg/hen/d and 0.29 g/d in the Standard g₁ treatment, respectively. Increasing g₁ reduced feeding motivation index by 1.6 and 0.8 visits/meal during rearing and laying phase, respectively. Earlier pubertal growth showed prominent effects on the reproductive performance.

Effects of diet density and feeding frequency during the rearing period on broiler breeder performance

1. An experiment was conducted to study the effects of diet density and feeding frequency during the rearing period on broiler breeder performance between three and 40 weeks of age.2. A total of 960 female one-day-old chicks (Ross 308) were randomly allocated to 24 floor pens (12 pens in two rooms). On day 21 pullets were assigned to a 2 × 2 factorial arrangement including two diets (control (CON) or 16% diluted (DIL)) and two feeding strategies (fed once (FO) or twice (FT) a day). The FO pullets were fed at 0815 h (100%) and FT pullets at 0815 h (60%) and 1215 h (40%). Water was provided by nipple drinkers with drip cups during 7 and 8 h in the rearing and laying period, respectively.3. Body weight (BW) and water intake were measured weekly and BW uniformity at 10 and 20 weeks of age. Litter characteristics were measured at 10, 15, and 20 weeks of age. During the laying period, egg production and incubation characteristics were recorded.4. The DIL pullets received a higher feed allowance in combination with similar water intake which resulted in a lower water/feed ratio compared to the CON pullets resulting in a higher DM content of the litter and improved litter quality. The higher feed allowance resulted in a 20% higher total manure production at 20 weeks of age. The FT pullets showed a lower body weight (BW) CV at 10 weeks of age; however, no effect was found at 20 weeks of age. During the laying period, FT pullets tended to have earlier onset of lay, higher total egg production at 30 weeks of age and better fertility.5. It was concluded that alternative feeding strategies can positively influence production performance during both the rearing and laying period.

Impact of growth curve and dietary energy-to-protein ratio on productive performance of broiler breeders

The impact of growth curve (GC) and dietary energy-to-protein ratio on productive performance of broiler breeder females was investigated from 0 to 60 wk of age. One-day-old pullets (n = 1,536) were randomly allotted to 24 pens according to a 2 × 4 factorial arrangement, with 2 GC (standard growth curve = SGC or elevated growth curve = EGC, +15%) and 4 diets, differing in energy-to-protein ratio (96%, 100%, 104%, or 108% AME_n). Feed allocation per treatment was adapted weekly based on the desired GC, meaning that breeders fed the different diets within each GC were fed according to a paired-gain strategy. Linear and quadratic contrasts for energy-to-protein ratio for each GC were evaluated. Elevated growth curve breeders had an earlier sexual maturity (∆ = 4.1 d) than SGC breeders. Egg weight was higher for EGC breeders (∆ = 2.3 g) than for SGC breeders over the whole laying phase (22–60 wk). No differences between EGC and SGC breeders were observed on settable egg production. An increase in dietary energy-to-protein, at a similar BW, led to a linear increase in age at sexual maturity (β = 0.14 d/% AME_n). From 22 to 40 wk of age, an increase in dietary energy-to-protein ratio led to a linear decrease in egg weight (β = -0.06 g/% AME_n), regardless of GC. An interaction between GC and dietary energy-to-protein ratio was observed on settable egg production in this phase. An increase in dietary energy-to-protein ratio led to a linear decrease on settable egg production, which was more profound in EGC breeders (β = -0.70 eggs/% AME_n) than in SGC breeders (β = -0.19 eggs/% AME_n). From 41 to 60 wk of age, an interaction between GC and dietary energy-to-protein ratio was observed on egg weight. In the EGC, an increase in dietary energy-to-protein ratio led to a linear decrease in egg weight (β = -0.13 g/% AME_n), whereas in the SGC, a linear increase in egg weight was observed (β = 0.03 g/% AME_n). From 41 to 60 wk of age, no differences between diets were observed on settable egg production. It can be concluded that a higher GC of breeders has beneficial effects on egg weight, while maintaining settable egg production. Feeding breeders a lower dietary energy-to-protein ratio stimulated productive performance of broiler breeder hens, mainly during the first phase of lay. This effect was more profound when breeders were fed according to a higher GC.

Maternal dietary supplementation with grape seed extract in reproductive hens increases fertility in females but decreases semen quality in males of the F1 generation

Genetic selection in parental broiler breeders has increased their susceptibility to metabolic disorders and reproductive dysfunction. We have recently shown that maternal dietary grape seed extract (GSE) supplementation in hens improves fertility parameters, egg quality, oxidative stress in different tissues and the quality of F1 chicks. Here, we analysed the growth and fertility (both female and male) of the F1 generation animals and the quality of their offspring (F2 generation). Eggs issued from hens supplemented with GSE presented lower ROS production than control hens, suggesting a change in the embryonic environment. However, this did not affect the growth nor the body composition of male and female F1s from hatching to adulthood (37 weeks of age). At 37 weeks of age, the biochemistry analysis of the GSE-F1 muscle has revealed an increase in sensitivity to oxidative stress and a slight change in lipid composition. Both male and female F1-GSE groups presented a delay in puberty with a lower testis volume at 30 weeks of age and lower ovary development at 26 weeks of age. Adult GSE-F1 males did not present histological alterations of seminiferous tubules or semen production, but the semen quality was degraded due to higher oxidative stress and DNA-damaged spermatozoa compared with control F1 animals. In adult GSE-F1 females, despite the delay in puberty, the females laid more eggs of better quality (fewer broken eggs and a higher hatching rate). At hatching, the weight of the chicks from GSE-F1 females was reduced, and this effect was stronger in F2 male chicks (F2) compared with F2 control chicks (F2), because of the lower muscle volume. In conclusion, we can raise the hypothesis that maternal dietary GSE supplementation produces eggs with change in embryonic metabolism, which may affect in adulthood the fertility. The data obtained from the F1-GSE group pointed to a sex-specific modification with higher egg quality in females but semen sensitive to stress in males. Finally, male F2 chicks were leaner than control chicks. Thus, maternal dietary grape seed extract (GSE) supplementation in hens may impact on the fertility of the offspring in a sex-specific manner in subsequent generations.

Feeding, feed-seeking behavior, and reproductive performance of broiler breeders under conditions of relaxed feed restriction

Broiler breeders are feed restricted to optimize reproductive performance. A randomized controlled study was conducted to investigate the effect of increasing female broiler breeder BW on feeding, feed-seeking behavior, and reproductive performance. It was hypothesized that a greater BW would decrease feeding and feed-seeking behavior, and reduce reproductive performance. Ross 708 female broiler breeders (n = 36) were fed using a precision feeding system from 2 to 42 wk of age. Ten BW trajectories were created from a multiphasic Gompertz growth model that increased growth from 0 to 22.5% in the prepubertal and pubertal phases of growth, in 2.5% increments. Six unrestricted birds were not limited to a maximum BW. Body weight was evaluated as a 2-way ANOVA. Two linear regression analyses were conducted, one which included all birds and one which excluded the unrestricted birds. For the regression analyses, BW at photostimulation (22 wk of age) was used as the continuous independent variable to represent the degree of variation between trajectories. Differences were reported at P ≤ 0.05. Body weight increased as trajectory-specific BW targets increased from 6 to 28 wk of age. Differences of BW between BW trajectories decreased during the laying period, which was a result of individual bird variation within BW trajectories. Station visit frequency decreased per kilogram increase in BW for all birds during rearing and lay, and within feed-restricted birds during lay only. The number of meals and ADFI increased with age, which reflected nutrient intake to support maintenance, growth, and reproductive requirements. Mean egg weight (EW) of all birds increased by 0.72 g per kilogram increase in BW from 22 to 41 wk of age. From 22 to 29 wk of age, mean EW of feed-restricted birds increased by 2.78 g per kilogram increase in BW. For every kilogram increase in BW, age at first egg comparing all birds decreased by 10.83 d. Two unrestricted birds came into lay before photostimulation. In contrast with the hypotheses, BW increased up to 22.5% above the recommended target did not reduce feeding and feed seeking behavior, or negatively impact reproductive performance.

Microbiota Changes Due to Grape Seed Extract Diet Improved Intestinal Homeostasis and Decreased Fatness in Parental Broiler Hens

In poultry, the selection of broilers for growth performance has induced a deterioration in the health of the parental hens associated with poor reproductive efficiency. To improve these parameters, we administered to laying parental broiler hens a regular diet supplemented or not (Control) with a moderate (1%) or a high level (2%) of grape seed extract (GSE). The 1% GSE diet was administered from a young age (from 4 to 40 weeks of age) and the high level of 2% GSE was administered only during a 2-week period (from 38 to 40 weeks of age) in the laying period. The analysis of 40-week-old hens showed that 2% GSE displayed a reduction in the fat tissue and an improvement in fertility with heavier and more resistant eggs. Seven monomer phenolic metabolites of GSE were significantly measured in the plasma of the 2% GSE hens. GSE supplementation increased the relative abundance of the following bacteria populations: Bifidobacteriaceae, Lactobacilliaceae and Lachnospiraceae. In conclusion, a supplementation period of only 2 weeks with 2% GSE is sufficient to improve the metabolic and laying parameters of breeder hens through a modification in the microbiota.

Effect of Qualitative Feed Restriction in Broiler Breeder Pullets on Stress and Clinical Welfare Indicators

The feed restriction applied during rearing of broiler breeders inflicts chronic hunger, and frustration due to unfulfilled behavioural needs for feeding. To alleviate the welfare problems associated with feed restriction, qualitative feed restriction allows a larger amount of feed to be provided without increasing the energy intake. In the present study, the aim was to investigate the effect of scatter-fed qualitative feed restriction on a range of welfare indicators in broiler breeders at the end of the rearing period. In total, 1,200 female breeder chicks of the genotype Ross 308 were housed in 24 pens: six pens of initially 50 birds per dietary treatment. The treatments were: (1) standard feed (Control), (2) standard feed diluted with oat hulls (Insoluble), (3) standard feed diluted with oat hulls and sugar beet pulp (Mixed), and (4) standard feed plus maize silage (Roughage). At 15 weeks of age, a blood sample was taken from 40 birds (10/treatment) five times within 24 h. The plasma was analysed for corticosterone concentration. At 19 weeks of age, a clinical welfare assessment was performed on all birds before they were sacrificed. From each bird, three feathers were plucked and macroscopically examined for the presence of fault bars. Feather length and weight were also recorded. Mortality was registered on occurrence throughout the rearing period. Treatment affected the plumage condition, footpad dermatitis, plumage dirtiness, vent pasting, and number of severe fault bars (P ≤ 0.05) but not plasma corticosterone concentration, hock burns, hyperkeratosis and mortality (P ≥ 0.17). There was an effect of the interactions between treatment and feather type on the total number of fault bars per feather, average position of the fault bars relative to the base of the feather, and growth rates of feather mass and length (P < 0.0001). Overall, the results showed improved welfare of Roughage birds and reduced welfare of Mixed birds, whereas the welfare of Insoluble birds did not seem to differ noticeably from that of Control birds. We recommend to further develop a feeding strategy that includes daily allocation of roughage to broiler breeders during the rearing period.

The effect of reduced balanced protein diet on the behavior of female broiler breeders in 2 generations

The behavior of 2 generations of broiler breeders undergoing a 25% reduced balanced protein (RP) dietary treatment was investigated in the current study. There were 2 treatments for the F0 generation: control (C) breeders fed with standard C diets and RP breeders fed with RP diets. The female progeny of each treatment was again subjected to 2 dietary treatments, resulting in 4 treatments for F1 generation: C/C, C/RP, RP/C, and RP/RP (breeder feed in F0/F1 generation). To maintain the target body weights throughout the trial, breeders on RP diet received on average 10% more feed than C diet breeders. The behavior of the breeders at 8h30 (30 min before feeding at 9h00), 12h00, and 15h30 in weeks 23 and 37 of the F0 generation and in week 6, 11, and 22 of the F1 generation was observed. Litter scratching, feather pecking, and object pecking were occasionally increased by RP diet feeding which indicated feeding frustration. Drinking behavior decreased dramatically by the RP dietary feeding and resulting in a better litter condition which could benefit dust bathing behavior. In addition, feeding the breeders RP diet in the F0 generation decreased litter scratching (week 6) and feather pecking (week 22, 15h30) but increased sitting (week 11, 15h30) and drinking (a tendency in week 6 and a significant effect in week 11) behavior of offspring breeders (F1 generation). In general, breeders fed with reduced balanced protein diets, to some extent, spent less time drinking and their offspring could have an adaptation to the maternal RP diet. The mechanism of this adaptation still needs to be further investigated. In general, positive effects were found by reducing protein level of breeder diets. However, negative side effects such as feeding frustration were also observed, which merit further study.

The effect of alternative feeding strategies for broiler breeder pullets: 2. Welfare and performance during lay

Feeding broiler breeders to satiety has negative consequences on their health and reproduction. Alternative feeding strategies during rearing can improve welfare, although their implications during lay are not well understood. The objective was to examine the effect of rearing feeding treatments on the reproductive performance and feeding behavior of broiler breeders under simulated commercial conditions. At 3 wk of age, 1,680 Ross 308 pullets were allocated to 24 pens under 1 of 4 isocaloric treatments: 1) daily control diet; 2) daily alternative diet (40% soybean hulls and 1 to 5% calcium propionate); 3) 4/3 control diet (4 on-feed days, 3 non-consecutive off-feed days per week); and 4) graduated control diet. Feeding frequency of the graduated treatment varied with age and finished on a daily basis. At 23 wk of age, group sizes were adjusted to 40 hens, and 5 mature Yield Plus Males roosters were introduced to each pen. Pens were under the same daily feeding management and same diet during lay. The performance of broiler breeders (growth rate, body weight uniformity, and reproductive performance) was determined until 64 wk of age. At the end of lay, feeding motivation was examined with a feed intake test and a compensatory feeding test. Data were analyzed using linear mixed regression models, with pen nested in the models and age as a repeated measure. The laying rate of hens reared on the graduated treatment decreased slower compared to control hens, resulting in a higher cumulative egg production (178.2 ± 3.8 eggs/hen) than control hens (165.2 ± 3.8 eggs/hen, P < 0.01) by 64 wk of age. Hens reared on non-daily feeding treatments laid lighter eggs with relatively heavier yolks and had higher feed intake at the end of lay than hens fed daily during rearing (P = 0.02). In conclusion, rearing feeding treatments impacted the growth rate and body weight uniformity during lay, feeding motivation at the end of lay, and the laying rate and hatchability depending on hens' age.

Sex differences in basal hypothalamic anorectic and orexigenic gene expression and the effect of quantitative and qualitative food restriction

Background

Research into energy balance and growth has infrequently considered genetic sex, yet there is sexual dimorphism for growth across the animal kingdom. We test the hypothesis that in the chicken, there is a sex difference in arcuate nucleus neuropeptide gene expression, since previous research indicates hypothalamic AGRP expression is correlated with growth potential and that males grow faster than females. Because growth has been heavily selected in some chicken lines, food restriction is necessary to improve reproductive performance and welfare, but this increases hunger. Dietary dilution has been proposed to ameliorate this undesirable effect. We aimed to distinguish the effects of gut fullness from nutritional feedback on hypothalamic gene expression and its interaction with sex.

Methods

Twelve-week-old male and female fast-growing chickens were either released from restriction and fed ad libitum or a restricted diet plus 15% w/w ispaghula husk, a non-nutritive bulking agent, for 2 days. A control group remained on quantitative restriction. Hypothalamic arcuate nucleus neuropeptides were measured using real-time PCR. To confirm observed sex differences, the experiment was repeated using only ad libitum and restricted fed fast-growing chickens and in a genetically distinct breed of ad libitum fed male and female chickens. Linear mixed models (Genstat 18) were used for statistical analysis with transformation where appropriate.

Results

There were pronounced sex differences: expression of the orexigenic genes AGRP (P < 0.001) and NPY (P < 0.002) was higher in males of the fast-growing strain. In genetically distinct chickens, males had higher AGRP mRNA (P = 0.002) expression than females, suggesting sex difference was not restricted to a fast-growing strain. AGRP (P < 0.001) expression was significantly decreased in ad libitum fed birds but was high and indistinguishable between birds on a quantitative versus qualitative restricted diet. Inversely, gene expression of the anorectic genes POMC and CART was significantly higher in ad libitum fed birds but no consistent sex differences were observed.

Conclusion

Expression of orexigenic peptides in the avian hypothalamus are significantly different between sexes. This could be useful starting point of investigating further if AGRP is an indicator of growth potential. Results also demonstrate that gut fill alone does not reduce orexigenic gene expression.

Electronic supplementary material

The online version of this article (10.1186/s13293-018-0178-6) contains supplementary material, which is available to authorized users.

Growth curve and diet density affect eating motivation, behavior, and body composition of broiler breeders during rearing

The aim of this work has been to assess the effect of diet density [control (CON) or 15% diluted (DIL)] and growth curve [recommended by the genetic line (RBW) or 15% heavier (HBW)] and their interaction on BW uniformity, feeding motivation, behavior, and body composition of broiler breeder pullets. A total of 3,000 one-day-old female breeders Ross 308, distributed in 20 pens, was randomly assigned to each treatment. Feed allowance was weekly adjusted to reach the desired BW. Feed was provided as pelleted (zero to 3 wk) and crumble (4 to 19 wk). Time eating was measured at 7, 11, and 19 weeks. A feeding rate test was performed after 11 weeks. Behavior was observed at 9 and 15 wk, by visual scan. At 6, 13, and 19 wk of age, one bird/pen was slaughtered for weighing different organs and analyzing the composition of empty whole bodies. Treatments did not affect BW uniformity; relative weights of the ovary, oviduct, or gizzard; or protein content of empty BW. Time eating varied with the growth curve at 19 wk (P < 0.05), HBW pullets spent 19 more min eating than RBW pullets. DIL led to 4 and 8 more min eating at 19 wk for pullets of RBW and HBW (P < 0.05), respectively. Pullets fed DIL consumed 30% (P < 0.05) less during the feeding rate test when kept on a restricted regimen, and they had lower compensatory energy intake after ad libitum feeding than those fed CON, indicating lower feeding motivation. Behavior was affected by the age and by the time of the d measured, but it did not change with the treatments. Birds spent most time pecking objects (50%), feeding (28%), and drinking (17%). Pullets fed DIL had 8% lower breast yield at different ages and higher empty digestive tracts at 6 weeks. Body composition varied with age; fat content increased from 12.7 to 15.9 to 19.8% for 6, 13, and 19 wk, respectively. The lowest body fat was observed for RBW pullets fed DIL (P = 0.003) at 19 weeks. Feeding DIL diets to HBW pullets could be done to increase the time spent eating and reduce their feeling of hunger without negative effects on body composition. However, its influence on behavior and BW uniformity was not proved.

Food restriction but not fish oil increases fertility in hens: role of RARRES2?

Overfed hens selected for their rapid growth become fatter and develop reproductive disorders. Herein, we aimed to demonstrate that food restriction leading to a weight reduction and/or a supplementation with fish oil may be effective in preventing reproductive disorders through the regulation of adipokine expression in broiler hens. This study included four groups of food restricted (Rt) orad libitumhens (Ad, feeding at a rate 1.7 times greater than Rt hens) supplemented or unsupplemented with fish oil (1%). The Rt diet significantly increased plasma chemerin (RARRES2) levels during the laying period, delayed sexual maturity by one week and improved egg quality and fertility. These effects were associated with higher progesterone production in response to IGF1 (or LH) in cultured granulosa cells andin vivoegg yolk, as compared with Ad hens. Fish oil supplementation had similar effects to the Rt diet on progesterone (P < 0.05), but without any effect on fertility. Using RT-PCR, we found thatRARRES2levels were lower in theca cells of Rt hens andNAMPTlevels were increased by the fish oil supplementation. A significant positive correlation betweenRARRES2expression in granulosa cells and the weight of F1 preovulatory follicle was observed, as well as a negative correlation of plasma RARRES2 levels with hatchability. Thus, food restriction but not fish oil supplementation improved fertility, and this was associated with variations in RARRES2 plasma and ovarian expression in hens.

Effects of feeder space allocations during rearing, female strain, and feed increase rate from photostimulation to peak egg production on broiler breeder female performance

A study was conducted to determine if there were differences in female broiler breeder performance of 2 strains that had been subjected to 2 feeder space allocations during the growing period followed by 2 feeding to peak programs. Ross 308 and 708 pullets were reared with a single feeding program to 23 wk of age and with 2 circumferential feeder space allocations (5.3 cm/female or 7.0 cm/female) and then assigned to 2 feed increase programs (slow or fast) from photostimulation to peak egg production. The flock was moved to the laying house with 8.8 cm/female of female feeder space and photostimulated at 23 wk of age when Ross 344 males were added to create 16 pens with 60 females and 7 males each in a 2 × 2 × 2 design. The fast feed increase program significantly increased female BW at 31 wk of age, which could have contributed to an increased female mortality during the summer weather of early lay. The 708 females with 5.3 cm/female feeder space produced smaller eggs at 28 and 30 wk of age. The 708 females exhibited better fertile hatchability than 308 females due to fewer late dead embryos. There were no differences in egg production, fertility, or fertile hatchability due to the main effects of feeding to peak program or growing feeder space, but the slow feed increase from photostimulation to peak production reduced cumulative mortality.

The effect of increasing feeding frequency on performance, plasma hormones and metabolites, and hepatic lipid metabolism of broiler breeder hens

An experiment was conducted to study the effects of feeding regimens on reproductive performance, plasma hormone and metabolite levels, and hepatic lipid metabolism of Cobb 500 broiler breeder hens from 26 to 38 wk of age. Seventy-two birds were used in a completely randomized design with 3 treatments, each replicated 4 times. Treatments were as follows: 1) once a day feeding, in which birds were fed once a day at 0615 h (control), 2) twice a day feeding, in which daily allocated feed was fed in 2 equal meals at 0615 and 1215 h, and 3) thrice a day feeding in which daily allocated feed was offered in 3 equal meals at 0615, 1215, and 1815 h. Through 38 wk of age, total hen-day egg production in the hens fed twice and thrice a day was greater (67.1 and 67.2 vs. 62.2 eggs/hen, P < 0.01). Similarly, egg weight was higher (P < 0.01) in birds fed more than once a day. Multi-meal-fed birds had significantly lower plasma triiodothyronine and glucose at 32 wk and also lower glucose and cholesterol, and higher 17β-estradiol levels at 38 wk than those fed once a day (P ≤ 0.05). Hepatic expression of malic enzyme, fatty acid synthase, acetyl-CoA carboxylase, and ATP citrate lyase relative to β-actin decreased (P < 0.05) in birds fed twice and thrice a day compared with birds fed once a day at peak egg production (32 wk). In contrast, feeding regimens did not affect the hepatic gene expression of lipogenic enzymes after peak egg production at 38 wk. Stearoyl-CoA desaturase 1 (SCD1) gene expression was constant over dietary regimens. There was no difference in malic enzyme activity in multi-meal-fed birds at 38 wk. In summary, feeding broiler breeder hens 2 or 3 meals per day improved the reproductive performance during the early lay cycle. Implementing twice or thrice a day feeding regimens altered hepatic lipogenic gene expression in broiler breeder hens only at peak egg production, which indicated a short-term effect of increasing feeding frequency on hepatic lipid metabolism.

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.

High-fibre pelleted rations decrease water intake but do not improve physiological indexes of welfare in food-restricted female broiler breeders

1. A 3x2 factorial experiment was conducted with three diets and two lines of broiler breeder females to evaluate the contribution of low-energy rations for improving the welfare of feed-restricted birds during rearing. Experimental diets were fed from 6 to 16 weeks of age and were created by diluting a conventional grower (Control) ration containing 11.0 MJ ME/kg with 200 (8.8 MJ ME/kg) or 400 (6.6 MJ ME/kg) g oat hulls/kg using Optimoist to facilitate the pelleting process. Welfare was assessed by changes in behaviour and physiological variables at 8, 12 and 16 weeks of age. Birds were fed restricted quantities of feed to meet recommended body weight targets. 2. There was a decrease in the proportion of observations of drinking and an increase of preening in birds fed on the two experimental diets compared with the control. There was a linear decrease in litter moisture and the number of litter changes with increasing diet dilution, and water intake at 12 weeks was higher in the control than in the two experimental diets. There were no changes in physiological indexes of welfare (heterophil-lymphocyte ratio, plasma corticosterone and antibody responses) associated with the dietary treatments. 3. There were no important differences in the growth, behaviour or physiological responses to dietary treatment between the two lines of broiler breeders. Changes with age were similar to those reported in other experiments. 4. It was concluded that low-energy pelleted diets would improve litter conditions but not improve indexes of welfare in feed-restricted broiler breeders.

Effects of genotype and feed allowance on plasma luteinizing hormones, follicle-stimulating hormones, progesterone, estradiol levels, follicle differentiation, and egg production rates of broiler breeder hens

The aim of this study was to compare and relate plasma hormone levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4), estradiol (E2), and the in vitro P4 production capacity of the largest yellow (F1) follicle granulosa cells with the laying performance of 2 genotypes (a standard S line and a dwarf cross-experimental E line) maintained under ad libitum (SA, EA) or restricted (SR, ER) feeding regimens. Age-related hormone changes were determined from 4 to 50 wk, hormone changes during the ovulatory cycle were determined during lay, and changes in follicle granulosa cell P4-producing capacity in response to LH with or without growth factors were measured in vitro at different ages. The mean laying rate was similar for SR, EA, and ER but were lower for the SA. Plasma LH and FSH concentrations increased with age in all groups and peaked at puberty. Restricted feeding delayed puberty in both genotypes. Concentrations of E2 and P4 increased after puberty in all groups but delayed in restricted hens. Plasma levels of LH, FSH, P4, and E2 before and after puberty were not correlated with egg-laying performance, but peak E2 levels were. Luteinizing hormone and P4 concentrations during the ovulatory cycle showed differences that may be associated with the different laying performances of the 2 genotypes under ad libitum and restricted feeding. The increase in plasma LH concentration (from basal) during the preovulatory surge was higher in the SR than in the SA but was similar for EA, ER, and SA. The increase in P4 was also higher in SR than in the SA with no difference between EA and ER. In vitro P4 production by granulosa cells in response to LH with insulin-like growth factors, and bone morphogenetic protein-7 was different among the SA, SR, EA, and ER; the EA, SR, and ER had greater responses, and the SA had less response. The presence of insulin-like growth factors and bone morphogenetic protein-7 enhanced LH effects depending on the feeding regimen and age of hen. This finding suggests that differences in laying performances among genotypes fed at different nutritional levels may be partly due to differences in processes associated with follicular maturation modulated by gonadotropins and growth factors. It is concluded that the age at puberty is determined mainly by feed allowance, irrespective of genotype, and that differences in laying performance may be due to a combination of factors that include changes in the levels of gonadotropins or ovarian hormones and growth factors, BW, and the condition of the different genotypes under different feeding allowances.

Is There Peripheral or Ovarian Insulin Action Alteration in Broiler Breeder Hens Fed ad Libitum?

We investigated whether a change in peripheral glucose homeostasis, a local change in the insulin-related ovarian regulatory system, or both occurred in ad libitum-fed broiler breeder hens compared with feed-restricted counterparts. Feed-restricted (R, from 5 to 16 wk of age) and ad libitum-fed (A) hens from a standard commercial line (S) and an experimental dwarf genotype (E) were studied. Basal and stimulated plasma insulin and glucose concentrations were measured during the prebreeding and laying periods. In the basal state (after 16 h fasting) plasma glucose concentrations were significantly lower in SA chickens (-5% at 17 wk, -7.5% at 32 wk) compared with EA, SR, and ER chickens, with no difference in plasma insulin concentrations (n = 16). In 17-wk-old SA birds, 30 min after oral glucose loading, plasma glucose concentrations increased significantly compared with the basal state and were also significantly lower as compared with SR but did not differ significantly from EA and ER. Plasma insulin concentrations did not differ significantly between genotypes or regimens (n = 16). A potential modification of intracellular mediators involved in the regulation of cell growth and survival in small follicles that were overrecruited in SA compared with SR was also investigated in SA and SR hens at 32 wk. There was no effect of food restriction in phospho-Akt, Akt, phospho-ERK, and phospho-S6 in the small white ovarian follicles (n = 6) in the basal state and after 30 min of refeeding. In conclusion, the present study does not demonstrate any evidence of glucose intolerance during the prebreeding period, specific change in the ovarian small follicle insulin signalling pathway, or both, in laying broiler breeders fed ad libitum compared with feed-restricted hens.

Feed allowance-genotype interactions in broiler breeder hens

Ad libitum feeding reduces livability and reproductive fitness in broiler breeder hens. Two genotypes, a standard (S) and an experimental dwarf broiler breeder (E), were fed ad libitum (SA and EA, respectively), restricted at 55% of ad libitum feed intake (intermediate restriction) from 6 to 15 wk of age (SI and EI, respectively), or restricted (SR and ER, respectively) to match a standard growth curve with a diluted mash feed (2,400 kcal/kg). The experiment was repeated at 2 locations (experiment 1 = 672 hens in pens from 0 to 40 wk; experiment 2 = 420 hens in pens and cages from 0 to 53 wk). Feed restriction reduced adult BW by 20% compared with ad libitum feeding, delayed sexual maturity by 2 to 4 wk, and improved livability. Hens fed the intermediate diet immediately compensated after 15 wk of age to reach BW, sexual maturity, and livability close to those of ad libitum-fed hens. The E genotype exhibited better tolerance to ad libitum feeding than the S genotype in all measured aspects. Average laying rate during the first 24 wk of lay was 66.4, 77.4, 69.9, 47.2, 57.9, and 72.4% for EA, EI, ER, SA, SI, and SR respectively in experiment 2. Egg abnormalities (double yolk, shell problems) decreased after the peak of lay but remained consistently higher for S compared with E, and for ad libitum and intermediate diets compared with the restricted diet. Yolk deposition rate was measured by a double dye technique. Duration of yolk rapid growth was 8.8 d in E and 9.3 d in S hens (P < 0.001), but this difference did not explain the observed variations in laying rate. The potential to increase feed allowances even with a diluted diet in broiler breeder hens requires adapted genotypes.

Leptin receptor in the chicken ovary: potential involvement in ovarian dysfunction of ad libitum-fed broiler breeder hens

In hens, the ovarian follicles committed to ovulation are arranged in an ordered follicular hierarchy. In standard broiler breeders hens genetically selected for high growth rate the reproductive function is clearly dysfunctional. Feed restriction is needed during reproductive development to limit the formation of excessive numbers of ovarian yellow follicles arranged in multiple hierarchies. To determine whether leptin is involved in the nutritional and reproductive interactions controlling follicular hierarchy in hens, blood leptin levels and ovarian expression of the leptin receptor mRNA were determined during follicle maturation in three chicken lines; a slow growing broiler "Label" genotype without reproductive dysfunction, a fast growing "Standard" genotype fed ad libitum or restricted and a fast growing "Experimental" line with intermediate reproductive performance levels. Whereas expression of the leptin receptor mRNA did not change in the theca, it clearly decreased with follicular differentiation in the granulosa of slow growing hens. In fast growing standard hens fed ad libitum and presenting significant reproductive dysfunction, the decrease was disrupted and dramatic up-regulation of granulosa cell expression of the leptin receptor was observed. On the other hand, feed restriction decreased the overall level of expression of the leptin receptor mRNA and restored the decrease with follicular growth. The level of expression of the leptin receptor probably modulates the action of leptin on follicular differentiation. Since blood leptin and other metabolic factors were not affected by the genotype or by nutritional state, the factors involved in the regulation of leptin receptor gene expression remain to be determined. This study demonstrates the involvement of leptin in the nutritional control of reproduction in birds. Leptin action on the ovary probably controls follicular hierarchy through the regulation of steroidogenesis.