Climate change and broiler production

Climate change has emerged as a significant occurrence that adversely affects broiler production, especially in tropical climates. Broiler chickens, bred for rapid growth and high meat production, rely heavily on optimal environmental conditions to achieve their genetic potential. However, climate change disrupts these conditions and poses numerous challenges for broiler production. One of the primary impacts of climate change on broiler production is the decreased ability of birds to attain their genetic potential for faster growth. Broilers are bred to possess specific genetic traits that enable them to grow rapidly and efficiently convert feed into meat. However, in tropical climates affected by climate change, the consequent rise in daily temperatures, increased humidity and altered precipitation patterns create an unfavourable environment for broilers. These conditions impede their growth and development, preventing them from reaching their maximum genetic influence, which is crucial for achieving desirable production outcomes. Furthermore, climate change exacerbates the existing challenges faced by broiler production systems. Higher feed costs impact the industry's economic viability and limit the availability of quality nutrition for the birds, further hampering their growth potential. In addition to feed scarcity, climate change also predisposes broiler chickens to thermal stress. This review collates existing information on climate change and its impact on broiler production, including nutrition, immune function, health and disease susceptibility. It also summarizes the challenges of broiler production under hot and humid climate conditions with different approaches to ameliorating the effects of harsh climatic conditions in poultry.

Photoperiod manipulation corrects the negative effect of low dietary crude protein levels during weeks 12 to 26 on bone quality and fertility of male Guinea fowl (Numida meleagris)

Improving the reproductive performance of guinea fowl (Numida meleagris) based on the management of environmental factors is important for developing meleagriculture. Thus, the present study was conducted to evaluate the effect of dietary crude protein levels and photoperiod during the 12th to 26th wk of age on growth performance, calcium and phosphorus mobilization, and fertility of local Pearl Gray male guinea fowl. In total, 120 twelve-week-old male guinea fowl were divided into 3 groups with 8 replicates each and 5 birds per replicate using a completely random design. The experimental groups included: a group fed a diet containing 15% crude protein and subjected to 16 h of light and 8 h of darkness (16LL), a group fed a diet containing 19% crude protein and subjected to 16 h of light and 8 h of darkness (16HL), and a group fed a diet containing 15% crude protein and subjected to 18 h of light and 6 h of darkness (18LL) during the 12th to 26th wk of age. The results showed that guinea fowl in the 16HL treatment had a significantly (P = 0.003) lower feed conversion ratio than those in the 16LL and 18LL groups. Calcium and phosphorus levels in the tibia and femur were significantly higher (P < 0.05) in guinea fowl of the 16HL and 18LL groups than in that of the 16LL group. Birds in the 16HL and 18LL treatments had significantly higher peripheral testosterone levels (P < 0.00001) than those in the 16LL treatment. The 16HL and 18LL treatments had significantly higher (P < 0.05) sperm volume, sperm concentration and motility, and fertility rate than the 16LL group. Therefore, a decrease in crude protein level from 19 to 15% in the diet of male guinea fowl between the 12th and 26th wk of age negatively affects the growth performance and fertility of these birds, but this is corrected by an increase in the photoperiod before sexual maturity.

Effect of crossbreeding on egg quality, incubation, and hatching activities of the pure and reciprocal cross between the Sasso and Wassache chickens

Understanding the effect of crossbreeding on egg quality and incubation is essential for the selection of superior genetic combinations in breeding programs. This study evaluated the effect of crossbreeding on egg quality and incubation activities of the Sasso and Wassache chickens in a pure (Sasso X Sasso [SS]; Wassache X Wassache [WW]) and reciprocal cross (Wassache X Sasso [WS]; Sasso X Wassache [SW]) design. A total of 1431 eggs were incubated while 400 eggs were selected for egg quality. Fertility, hatchability, and hatching activities were expressed in percentage, while egg quality traits were determined. The crosses with Sasso hens laid similar (P > 0.05) but heavier (P < 0.05) eggs with higher (P < 0.05) egg components compared to the crosses with Wassache hens. The SS, SW, and WW genotypes recorded similar (P > 0.05) early embryonic mortality (EEM) and were lower (P < 0.05) compared to the WS genotype. Late embryonic mortality (LEM) between the reciprocal crosses and SS was similar (P > 0.05) and lower (P < 0.05) compared to the WW. The hatchability and hatchability of fertile eggs between the purebreds and the SW cross were comparable (P > 0.05), while those of the WS genotype was lower compared to the SS cross. Hatch duration in the crossbreds was shorter (P < 0.05) compared to the pure Sasso. Mortality between the SW and WW was similar (P > 0.05) while the WS cross recorded a higher (P < 0.05) mortality compared to the purebreds. Crossbreeding improved egg quality, reduced LEM, and accelerated crossbred hatching events. The SW cross is recommended for better performance.

Phenotypic and morphometric characterization of domestic geese raised in northern Benin

Documentation on the domestic geese (Anser anser) in Benin is scarce, making it objectively difficult to exploit. Its production depends on small flocks raised by livestock farmers in different areas. The aim of the study was to describe the phenotypic and morphometric characteristics of geese encountered in northern Benin. To this end, a total of 576 adult geese (353 males and 223 females) from 102 farms in 4 agro-ecological zones of northern Benin were evaluated for 11 quantitative and 5 qualitative body traits. There are 6 plumage colors with white (42.01%), white-brown magpie (24.65%) and white-grey magpie (17.19%) as dominant colors. The proportions of white-grey (75%) and multicolored (51.85%) in Far northern zone of Benin (FNZB) were higher (P < 0.05) than those in the cotton zone of northern Benin (CZNB), Food-producing zone of southern Borgou (FZSB) and West-Atacora Zone (WAZ). The red coloring of the tarsi was more dominant in the FZSB (63.09%) and the FZSB (61.79%) (P < 0.05). Orange (57.47%) and yellow (28.82%) colored beaks were dominant but did not vary (P > 0.05) from one agro-ecological zone to another. Quantitative traits such as body length, tarsus length, wing span and thoracic circumference of geese varied (P < 0.05) between 71.34 to73.22 cm, 10.08 to 10.6 cm, 131.95 to 135.42 cm and between 42.07 to 43.86 cm respectively. Males differed significantly from females (P < 0.05) for all morphometric traits. The live weight of geese in the FNZB showed higher values than those of other agro-ecological zones (P ˂ 0.05). In addition, white phenotype geese (3.76 kg) were heavier (P ˂ 0.05) than other phenotypes. All correlations between weight and body measurements of domestic geese were positive, but the correlations between live weight and wing span (r = 0.68) were the strongest. These correlations could be used to assess the live weight of the geese population studied and for selection based on live weight. This study provides a reference for morpho-biometric traits and will be complemented by molecular characterization.

Prebiotic effects of Talinum triangulare and Mangifera indica on slow growing broiler chickens (SASSO)

1

The study aim was to evaluate the prebiotic effects of Talinum triangulare and Mangifera indica used on slow growing broiler chickens.

2

Three hundred and sixty (360) slow-growing chicks of four weeks of age and similar weight were selected and divided into four (04) treatments (Positive Control, Negative Control, 2 % T. triangulare and 2 % M. indica) of 6 replicates with, fifteen (15) chicks per replicate, which made ninety (90) chicks per treatment.

3

At 12 week age, blood sample and cecal content were taken from 6 chickens per treatment to determine heamatological profile and fermentation parameters (Short Chain Fatty Acid). The data obtained were submitted to one-way analysis of variance (ANOVA) using the software R version 3.6.2 (R Core Team, 2019).

4

Results showed that growth performance, haematological parameters, acetic, butyric, valeric and caproic acids were similar between broilers fed with the leave powders and the positive control treatment. However, broilers fed with Talinum triangulare and Mangifera indica powders showed a lower mortality rate, compared to the negative and positive control treatments. Moreover, broilers fed with the leave powders showed significantly higher (p < 0.05) formic acid concentration than the other treatments.

5

Talinum triangulare and Mangifera indica leaves could have prebiotic properties because they stimulated the production of short-chain fatty acids that keep animals healthy.

Dietary protein levels during 12 to 26 wk improve the growth performance, bone quality, and testosterone in Pearl Gray male guinea fowl (Numida meleagris)

Guinea fowl (Numida meleagris), although native to Africa and despite its many potentials, does not represent the dominant species on the continent because of its seasonal reproductive nature and high keets mortality. This study was conducted to assess the effect of crude protein levels on growth performance, bone characteristics and reproductive activity of Pearl Gray male breeder guinea fowl from 12 to 26 wk of age. A total of 120 twelve-wk-old guinea fowls were randomly allotted to 3 dietary treatments with 8 replicates each and 5 birds per replicate using a completely randomized design. The dietary treatments comprised low level (LL), normal level (NL), and high level (HL) with diets respectively containing 15, 17, and 19% crude protein (CP). The results showed that guinea fowl in the HL treatment had a significantly lower feed conversion ratio (P = 0.008) than those in the other treatments. The birds fed the HL diet had significantly higher concentrations of testosterone (P < 0.05) than in the other treatments. High levels of calcium and phosphorus were observed in the femur of the HL group relative to the LL group. The birds in the LL treatment had a significantly higher (P = 0.007) femur robusticity index than those in the HL treatment. In conclusion, feeding 19% crude protein to Pearl Gray male guinea fowl from 12 to 26 wk of age improves growth performance, the density and strength of the femur and tibia and the reproductive tract. The CP level for the best performance of male guinea fowl from 12 to 26 wk of age is 19%.

Naked neck gene and intermittent thermal manipulations during embryogenesis improve posthatch performance and thermotolerance in slow-growing chickens under tropical climates

Many studies have shown that thermal manipulations during the incubation (TMI) and naked neck gene (Na) positively affect heat-stressed broilers' thermotolerance, hatching process, and posthatch performance. Their combination could increase the beneficial effect on broilers reared under natural tropical climatic conditions. The aim of this study was to investigate the effects of the Na gene and TMI on hatching and posthatch performance of slow-growing broilers under tropical climates. The study included 1,200 hatching eggs from 2 different crosses: 1) females and males, both with a normal or fully feathered neck (na na group), and 2) females (with a normal neck) and males (bare neck) (Na na group), incubated in similar conditions until d 7. Thereafter, they were assigned to 3 subgroups for each cross: the control group (C) was incubated at standard incubation conditions (37.8°C, 60% RH). The TMI-1 group was subjected to TMI-1 (T = 38.5°C, RH = 65%, E10-18, 6 h/d) and TMI-2 group to TMI-2 (T = 39.5°C, RH = 65%, E7-16, 12 h/d). Between 450 and 504 h of incubation, eggs were checked for hatching events. During the posthatch phase, chicks from each incubation subgroups (Na na-C, Na na-TMI-1, Na na-TMI-2, na na-C, na na-TMI-1, na na-TMI-2) were raised for 12 wk at a tropical natural ambient temperature. Hatchability, hatching time, chick's temperature, final body weight (FBW), and feed conversion ratio (FCR) were determined. The results revealed that the Na gene reduced (P ˂ 0.05) hatchability. The control group had the highest mortality rate compared to TMI-1 and TMI-2 groups. There was an interaction between genotype and TMI on incubation duration, hatching weight, chick quality, FBW, and FCR (P ˂ 0.05). In conclusion, the Na gene influenced the effects of thermal manipulation. TMI-1 combined with Na gene improved the productive performances of broilers in a tropical climate.

Alleviating heat stress effects in poultry: updates on methods and mechanisms of actions

Heat stress is a threat that can lead to significant financial losses in the production of poultry in the world's tropical and arid regions. The degree of heat stress (mild, moderate, severe) experienced by poultry depends mainly on thermal radiation, humidity, the animal's thermoregulatory ability, metabolic rate, age, intensity, and duration of the heat stress. Contemporary commercial broiler chickens have a rapid metabolism, which makes them produce higher heat and be prone to heat stress. The negative effect of heat stress on poultry birds' physiology, health, production, welfare, and behaviors are reviewed in detail in this work. The appropriate mitigation strategies for heat stress in poultry are equally explored in this review. Interestingly, each of these strategies finds its applicability at different stages of a poultry's lifecycle. For instance, gene mapping prior to breeding and genetic selection during breeding are promising tools for developing heat-resistant breeds. Thermal conditioning during embryonic development or early life enhances the ability of birds to tolerate heat during their adult life. Nutritional management such as dietary manipulations, nighttime feeding, and wet feeding often, applied with timely and effective correction of environmental conditions have been proven to ameliorate the effect of heat stress in chicks and adult birds. As long as the climatic crises persist, heat stress may continue to require considerable attention; thus, it is imperative to explore the current happenings and pay attention to the future trajectory of heat stress effects on poultry production.

Influence of age at slaughter and sex on carcass characteristics and technological and sensory quality of Goliath chicken meat

Background and Aim

The Goliath chicken is a slow-growing chicken with a high slaughter weight but whose carcass characteristics and meat quality have not yet been documented. This study aimed to evaluate the effect of age at slaughter and sex on the carcass characteristics and technological and sensory meat quality of Goliath chickens raised in southern Benin.

Materials and Methods

Data on the carcass characteristics and technological and sensory quality of meat were collected from 80 chickens raised in confinement and divided into two groups. The first group was reared for 12 weeks of age and the second group was for 20 weeks of age. The animals were individually weighed using an electronic balance (Terraillon 5000g) and then slaughtered. The different parts of the chicken carcass was weighed using the same method.

Results

The live, hot carcass, cold carcass, wing, thigh, and tail weights of males were significantly greater than those of females (p < 0.01). The wishbone muscle and thigh and tail assembly pH was lower in the 20-week-old chickens than in the 12-week-old chickens. The brightness and red index of the wishbone of the 20-week-old chickens were significantly higher than those of the 12-week-old chickens (p < 0.001). The red index of the wishbone and the yellow index of the thigh and tail assembly of females were lower than those of males.

Conclusion

The meat of 20-week-old Goliath chickens was juicier than that of 12-week-old chickens. Thus, the carcass composition of Goliath chickens is better at 20 weeks of age, especially in males.

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.

Effects of pre-incubation storage duration and nonventilation incubation procedure on embryonic physiology and post-hatch chick performance

This study investigated the effects and possible interactions of storage and nonventilation during incubation for eggs from Sasso broiler breeder flock on pre- and post-hatch incubation results.

A total of 1,260 Sasso eggs from a 58-wk-old broiler breeder flock were individually numbered, weighed and stored for 7 d or for 18 d in a climate-controlled room (16°C, 75% RH). After storage, eggs were weighed, and randomly assigned equally into 2 incubators. One of the incubators was ventilated (V) for the entire incubation and the second was nonventilated (NV) for the first 12 d. At d 18, the eggs were weighed, candled, and fertile eggs were transferred from the turning trays to hatching baskets. During the last 3 d of incubation, hatching eggs were checked individually every 3 h for hatching events and hatchability of fertile eggs. After pull out at d 21.5, post-hatch performances was determined until 1 wk of age.

Results showed that, embryo weights from eggs in NV incubator was significantly higher (P < 0.05) in both stored eggs compared to those from eggs in ventilated incubator, but embryos from eggs stored for 18 d were smaller (P < 0.05) than those from eggs stored for 7 d. Hatchability was higher (P < 0.0001) in NV incubator compared to V incubator in both 7 d and 18 d stored eggs and an interaction was found between incubation ventilation and storage duration on both hatchability and embryonic mortality (P < 0.0001). Chick weights from NV incubator at 7 d post-hatch was greater (P = 0.0009) than those from V incubator. Serum Tri-iodothyronine (T₃) and Thyroxin (T₄) concentrations were significantly higher (P < 0.05) in NV compare to V group.

It was concluded that the effect of long-term pre-incubation storage on embryonic physiology and post-hatch growth interacted significantly with incubation ventilation and that nonventilation can compensate for the negative effects of storage on some hatching and post-hatch performances.

Genetic diversity of indigenous guinea fowl (Numida meleagris) using microsatellite markers in northern Togo

Indigenous guinea fowl is an important animal resource for improving rural household income. In order to provide molecular data for a sustainable management of this poultry resource, an assessment of the genetic diversity and phylogenic relationships was undertaken on seven guinea fowl phenotypes from two agroecological zones (Dry Savannah and Atakora) of Togo. Genotyping was carried out using 18 microsatellite markers on 94 individuals from Dry Savannah (59) and Atakora (35) zones. The results obtained showed a high genetic diversity, with six as an average alleles per locus and an observed heterozygosity of 0.512. However, the F_IS values varied from 0.047 (Lavender) to 0.257 (Albino), reflecting a deficit of heterozygotes, which suggests low to moderate inbreeding levels. The genetic distances between phenotypes are low, ranging from 0.0068 (Bonaparte-Pearl grey) to 0.1559 (Lavender-Albino), unlike the strong genetic identities that reflect a strong genetic similarity between the seven phenotypes of indigenous guinea fowl studied. These results indicate the existence of a single indigenous guinea fowl population, derived from three probable parental populations, with a high within population genetic diversity (phenotypic or agroecological zone). These results could be of use to conservation and improvement programs aiming at the maintenance and sustainable exploitation of this important socio-cultural and economic resource in Togo.

Effects of egg storage duration on egg quality, metabolic rate, hematological parameters during embryonic and post-hatch development of guinea fowl broilers

Considering the value of guinea fowl keets, successful incubation of eggs is particularly desirable in this poultry species. This study evaluated the effect of egg storage duration on egg quality, heat production, hematological parameters during embryonic development and post hatch performance of guinea fowl broilers. A total of 800 hatching eggs of guinea fowl were used for this study. Before incubation, 12 eggs per treatment were used to analyse egg quality. Then, eggs were numbered, weighed, and assigned to 2 treatment groups of 400 eggs each according to storage duration of 5, and 10 d at a temperature of 18°C. The eggs were set for incubation at 37.7°C and 55% relative humidity for 28 d in a forced-draft incubator. To determine heat production as a measure of metabolism, 60 eggs in each replicate were transferred to respiratory cages post hatch two 12 wk old guinea fowl were also used to determine heat production. CO₂ and O₂ were recorded to calculate heat production at internal pipping, hatch and at 12 wk of age. The hatched keets were reared for 12 wk and data were collected on feed intake, body weight and feed conversion ratio. Blood samples were collected at hatch and at 12 wk of age from 24 guinea fowls per treatment to analyze haematological parameters. The results showed that embryos and guinea fowls at 12 wks of age from eggs stored for 5 d had higher (P ˂ 0.05) heat production and body weights. However, a significant higher (P ˂ 0.05) level of basophile, eosinophils, and lymphocytes was observed in guinea fowls from 10 d storage egg. It was concluded that extended duration of egg storage negatively influenced the metabolic rate of embryos. It also impacted hematological parameters which may suggest influence on immune response during embryonic and post-hatch growth.

Broiler production challenges in the tropics: A review

Under tropical climate, broiler production is encumbered by several constraints which make it difficult for them to attain their genetic potential. The scarcity and high price of poultry feed and veterinary services and the harsh environmental conditions with respect to thermal stress are some of the challenges that hinder optimal growth of the birds. Limited availability of feedstuffs, including crucial feed ingredients like maize and oil seedcakes, is an important challenge to the sector, since feed still represents a major cost of producing broiler chickens. Additionally, the problem of climate change, which has become a global concern, is the main problem in broiler production under hot and humid climate. Under high ambient temperature, feed intake decreases, carbohydrates metabolism and protein synthesis efficiency are disturbed. Lipid utilization is lower and glucose or insulin homeostasis is altered while fat deposition and oxidative stress increases. Several strategies are used to ameliorate the effect of heat stress in poultry. The objective of this review was to summarize the challenge in broiler production under hot and humid climate and different approaches to fight heat stress in poultry.

Supplementation with liquid whey and ACIDAL® ML in drinking water affect gut pH and microflora and productive performance in laying hens

1. As the use of antibiotics as growth promoters has been banned in many regions, there has been an on-going search for possible alternative compounds, such as prebiotics and organic acids. 2. This study was conducted to investigate the influence of liquid whey (LW) and organic acid (ACIDAL® ML) supplementation on performance, eggs characteristics, gut pH and health status in laying hens. 3. Seven hundred and fifty, Isa Brown chicks were randomly assigned to five treatments groups (n = 150) and each treatment had five replicates of 30 birds each. The birds were reared for 48 weeks. The treatments were administered in the drinking water at doses of: 250 ml/l of LW (Lacto25), 500 ml/l of LW (Lacto50) or 1 ml/l of ACIDAL® ML (Aci). A positive control group (T+) was treated with 500 mg/l of Tetracolivit (an antibiotic). The negative control group (T-) did not receive any treatment in the drinking water. 4. Administration of LW or ACIDAL® ML in the drinking water reduced (P < 0.05) the pH in the crop, proventriculus, ileum and caeca, as well as total coliform bacteria and E. coli, but increased Lactobacillus spp. in the ileum and caecum, compared to the negative control. 5. Oviposition was earlier in the birds in both the Lacto50 and Aci groups. The weight of birds at first lay and point of lay in the four treated groups was higher than those in negative control group. Furthermore, egg production was increased by 10.44% in birds receiving Lacto25, but the weight and quality traits were unaffected, while the egg shell ratio was higher in the Aci group compared to the other treatments. 6. The data indicated that addition of LW or ACIDAL® ML improved hens' performance by modifying gut pH and microflora.

Use of Moringa oleifera leaves in broiler production chain. 1 - Effect on Sasso breeder hens performances, internal quality of hatching eggs and serum lipids

An experiment was conducted to determine the effect of Moringa oleifera leaves (MOL) on breeder hen performance, hatching egg quality and blood parameters. A total of 180 Sasso broiler breeder hens were used for the study. They were allotted to two groups each containing 3 replicates of 30 hens of 18 weeks of age. Dietary treatments were a control diet (basal diet without moringa leaves) and a diet containing 10g of moringa leaves in 1kg of control diet (1% w/w). The experiment lasted 40 weeks. The following production parameters; feed intake, egg weight, laying rate and feed conversion ratio were measured for the whole experimental period while egg quality and blood parameters were assessed at different ages. Results showed that laying rate and hatching egg weight were improved by moringa meal diet for the whole experimental period. Feed intake and feed conversation ratio were decreased (p < .05) by incorporation of moringa leaves. Differences (p < .01) were observed in albumen and yolk ratio at 55th week of age. Yolk colour was (p < .001) improved by moringa meal at 31st, 43rd and 55th week of age. At the end of the experiment, serum concentrations of triglycerides, total cholesterol, low‐density lipoprotein cholesterol and atherogenic index were decreased (p < .05) while high‐density lipoprotein cholesterol was unaffected (p > .05) by incorporation of moringa in the diet. It was concluded that the use of moringa leaves as feed additive in Sasso breeders diet improved productivity and quality of hatching eggs.

Use of Moringa oleifera leaves as feed additive improve broiler breeders’ performances, number and weight of hatching eggs; and yolk colour. Except HDL cholesterol, serum lipids and atherogenic index are reduced by this phytobiotic.

Effect of guinea fowl egg storage duration on embryonic and physiological parameters, and keet juvenile growth

This study investigated the effects of guinea fowl hatching eggs storage time on embryo parameters and post-hatch juvenile growth. A total 1,800 eggs of guinea fowl were used. They were numbered, weighed, and divided into four groups of 450 eggs each according to storage time of 3, 7, 11, and 15 D before storage at a temperature of 18°C. Then, they were incubated at 37.7°C and 55% relative humidity for 28 D in a forced-draft incubator. Egg weight loss, albumen pH and weight, embryo weight, hatching events, and keet growth up to 7 D post-hatch were recorded. In addition, thyroid hormone and corticosterone levels were determined. The results indicate that during storage, relative egg weight loss increased with storage duration. However, albumen pH increased with storage time up to 11 D of storage and remained unchanged between 11 and 15 D. In addition, from 19 to 22 D of incubation, albumen weight was higher for eggs stored for 15 D compared to that of eggs stored for 3 to 11 D. But, from 16 D of incubation, embryos from eggs stored for 3 D grew faster than those from eggs stored for 7 to 15 D. Incubation durations up to internal pipping (IP), external pipping (EP), and hatching events increased with egg storage duration. At IP, corticosterone and triiodothyronine (T3) concentrations of eggs stored for 15 D had the lowest (P < 0.05) compared to those of eggs stored for 3 to 11 D. Moreover, the levels of thyroxine (T4) decreased with storage duration (P < 0.05). At hatch, corticosterone levels increased while T4 levels decreased with storage duration (P < 0.05). Also, hatchability decreased with egg storage duration. In addition, 7-day-old keets from eggs stored for 3 and 7 D had comparable weight and were heavier than those from eggs stored for 11 D. It was concluded that storage of guinea fowl hatching eggs more than 7 D negatively affects egg quality and subsequently depresses embryo and post-hatch growth.

High- and low-temperature manipulation during late incubation: effects on embryonic development, the hatching process, and metabolism in broilers

Temperatures continuously higher and lower than the standard incubation temperature by 3°C from embryonic d 16 until embryonic d 18.5 result in differential effects on embryonic development, the hatching process, and embryonic metabolism. Embryos in the high-temperature group were forced into a state of malnutrition by the temperature treatment, as reflected by reduced embryo growth and yolk consumption, resulting in a significantly lower chick weight at hatch. In addition, altered air cell and blood gases as well as a retarded hatching process further indicated reduced growth of embryos exposed to higher incubation temperatures during the latter part of incubation. In addition, hatchability was significantly reduced by the high-temperature treatment due to higher embryonic mortality during the treatment period and the hatching process. Levels of blood glucose, lactate, liver glycogen, plasma triglycerides, and nonesterified fatty acids indicated an altered carbohydrate and lipid metabolism for the high-temperature group. Although the hatching process of embryos exposed to lower incubation temperatures was also significantly retarded, their embryonic development and growth were strikingly similar to those of the control group.

Comparison of Cobb and Ross strains in embryo physiology and chick juvenile growth

Broiler performance is known to be related to embryonic developmental parameters. However, strain or genotype differences with regard to embryo physiological parameters and juvenile growth have received little attention. A total of 1,200 hatching eggs produced by Cobb and Ross broiler breeders of the same age were studied. At setting for incubation and between 66 and 130 h of incubation, egg resonant frequency (RF) was measured as an indicator of embryonic development. Also, eggs were weighed before setting and at d 18. From d 10 to 18 of incubation, remaining albumen was weighed. During the last days of incubation, hatching events such as internal pipping (IP), external pipping, and hatch were monitored every 2 h. Hatched chicks were recorded and weighed. At IP stage, gas partial pressures in the egg air chamber were measured. Hatched chicks were reared for 7 d and weighed. Results indicate that RF of Ross eggs were lower than those of Cobb eggs (P < 0.01) and starting time point of RF decrease occurred earlier in Cobb eggs than in Ross eggs. Relative egg weight loss up to 18 d of incubation was lower in Cobb than in Ross (P < 0.05). At IP, partial pressure of CO(2) was higher in Cobb than in Ross (P < 0.05) with shorter incubation duration in Cobb. Between 6 and 60 h posthatch, heat production was higher in Cobb than in Ross (P < 0.05). At 7 d posthatch, Cobb chicks were heavier than Ross chicks (P < 0.05). It is concluded that Cobb and Ross embryos-chicks have different growth trajectories leading in different patterns of growth resulting from differences in physiological parameters.

Effects ofad libitumfeeding on performance of different strains of broiler breeders

(1) Tolerance to ad libitum feeding was compared in three genotypes of broiler breeder hens: a standard broiler breeder fed ad libitum (SA) or restricted (SR), a slow growing 'label' broiler breeder (L) and an experimental dwarf heavy broiler breeder (E). Two similar experiments were conducted in two distinct research centres. (2) Feed intake and body weight were measured every 3 weeks from hatch to 40 to 49 weeks of age. Egg production and egg abnormalities were recorded. The number of yellow follicles in ovaries was counted at the age of 32 weeks. (3) Body weight was stabilised at 2.2, 3.7 and 5.4 kg after 24 weeks of age in L, E and SA hens, respectively. Growth of the SR hens was similar to that of L up to 20 weeks and stabilised at a similar level to that of E hens after 30 weeks of age. (4) Sexual maturity was delayed by 6 weeks in restricted breeders compared to ad libitum fed hens that started to lay at 20 weeks. SA hens had low egg production and a high proportion of defective eggs, which was largely compensated for by feed restriction. However, productivity of SR hens remained lower than that of L breeders. (5) Compared to the low viability and reproductive fitness observed with SA hens, the E dwarf broiler breeder tolerated ad libitum feeding and had better egg production, fewer egg abnormalities and yellow follicles per ovary and a higher egg production. However, laying rate was still lower than that of the SR and L groups. Energy conversion (kJ/g egg) from 32 to 40 weeks of age was much higher in the SA group than in the other three groups. 6. The feasibility of feeding a dwarf broiler breeder ad libitum calls for further research on implications of specific IGF and GH-receptor expression at the level of the ovary in dw chickens.

Effect of delayed feed access on production and blood parameters of layer-type chicks

A total of 684 Hisex Brown day-old chicks were studied. The chicks were randomly assigned into three groups as follows: (1) chicks with immediate feed access; (2) chicks with 48 h delay in feed access, and (3) chicks with 72 h delay in feed access. For each group, chicks were assigned into 4 replications of 57 birds each. Prior to feed access, the chicks were weighed. Samples of chicks were used to weigh yolk sac at 1, 3 and 7 days and to collect blood at 1, 3, 7, 14 and 56 days. Also, reared chicks were weighed weekly. The results indicated that chick weights decreased during the holding period. Yolk sac utilisation was similar between groups, while morbidity and mortality increased linearly with the duration of delay in feed access. At 56 days, chicks having delayed access to feed were lighter than those without delay in feed access. Serum concentration of glucose up to 14 days and of total protein and triglycerides until 56 days decreased with the increasing duration of delay in feed access. It can be concluded that delayed feed access is detrimental to the juvenile performance of layer-type chicks and has a negative age-related effect on the serum concentrations of glucose, triglycerides and total protein.

Effect of macronutrient ratio of the pre-starter diet on broiler performance and intermediary metabolism

The aim of this study was to investigate the influence of isoenergetic substitution between the three energy delivering macronutrients in pre-starter diets on performance and intermediary nutrient metabolism in broiler chickens. From hatch until 5 days of age, 600 chicks, collected during peak of hatch, were fed one of the three experimental pre-starter diets with isoenergetic (13 MJ metabolisable energy/kg) substitutions between fat (43 vs. 108 g/kg), protein (126 vs. 240 g/kg) and carbohydrates (391 vs. 510 g/kg). After 5 days, commercial grower and finisher diets were provided. Pre-starter composition influenced body weight until slaughter age, although not statistically verifiable. Broilers fed the low protein (LP) pre-starter had the lowest body weight in relation to chickens on the low carbohydrate or low fat pre-starter diet. After hatch, chicks on the LP pre-starter diet were able to use the residual yolk sac more rapidly to fulfil their protein requirement, which is reflected in small intestine and liver development. Also, plasma metabolite levels were influenced mostly by the LP pre-starter, indicating that the main focus for the requirements of newly hatched chicks should be on proteins. Furthermore, optimal nutrition during the first day's post-hatch should take into account the contribution of the yolk.

Empleo potencial de Stevia rebaudiana en alimentación animal

Se estudió el perfil nutricional de hojas y tallos de Stevia rebaudiana y su potencial empleo en un modelo animal. Las hojas y tallos de Stevia rebaudiana tienen 16% y 6,7% de proteína bruta y bajo contenido de grasa (2,6 y 1,1%) respectivamente. La grasa extraída mostró un predominio de ácidos grasos insaturados (65,8% y 71,4% para hojas y tallos respectivamente). El ácido graso más abundante en la hoja fue el linolénico (36%) y en el tallo, el linoleico (38%). La fibra bruta sobre materia seca desgrasada supuso el 6,8% para hojas y 45,4% para tallo. El contenido de K de hojas y tallos fue similar, la concentración de Ca, Mg, Fe, Cu, Zn, Mn fue mayor en las hojas y al contrario para Na. Las pruebas con broilers establecieron que los valores de energía aparente, corregida para N y metabolizable verdadera, fueron 2113, 2098 y 2223 kcal/kg en hojas, y 1573, 1554 y 1675 kcal/kg en tallos respectivamente. La retención de proteína foliar y de los tallos por los broilers fue 63 y 65,7% respectivamente. El contenido de esteviósido de las hojas fue 6,5% y el de rebaudiósido A de 2,3%. Los valores correspondientes para los tallos fueron 0,69% y 0,3%. Las hojas de Stevia rebaudiana contienen otros atributos nutricionales además de la alta concentración de componentes endulzantes (esteviósido y rebaudiósido A).

Non-ventilation during early incubation in combination with dexamethasone administration during late incubation: 1. Effects on physiological hormone levels, incubation duration and hatching events

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation and its combination with dexamethasone administration at day 16 or 18 of incubation on hatching parameters and embryo and post-hatch chick juvenile physiology. A total of 2400 hatching eggs produced by Cobb broiler breeders were used for the study. Blood samples were collected at day 18 of incubation, at internal pipping stage (IP), at the end of hatch (day-old chick) and at 7-day-post-hatch for T(3), T(4) and corticosterone levels determination. From 448 to 506 h of incubation, the eggs were checked individually in the hatcher every 2h for pipping and hatching. The results indicate that non-ventilation during the first 10-day shortened incubation duration up to IP, external pipping (EP) and hatch, had no effect on hatchability and led to higher T(3) levels at IP but lower corticosterone levels at 7-day-post-hatch. The injection of dexamethasone at days 16 and 18 of incubation affected hatching and blood parameters in both the ventilated and non-ventilated embryos differentially and the effect was dependent on the age of the embryo. Dexamethasone increased T(3) levels and T(3)/T(4) ratios but the effect was greater with early non-ventilation of eggs. Dexamethasone decreased hatchability but the effect was greater when injected at day 16 and especially in ventilated embryos. The effects of incubation protocols and dexamethasone treatments during incubation were still apparent in the hatched chicks until 7 days of age. The changes in T(3), T(4) and corticosterone levels observed in response to the early incubation conditions and late dexamethasone treatments in this study suggest that incubator ventilation or non-ventilation may influence the hypothalamic-pituitary-adrenal axis (HPA) regulation of stress levels (in terms of plasma corticosterone levels) and thyroid function in the embryo with impact on incubation duration, hatching events and early post-hatch life of the chick. Our results also suggest that some stages of development are more sensitive to dexamethasone administration as effects can be influenced by early incubation protocols.

Effects of thermal manipulation during early and late embryogenesis on thermotolerance and breast muscle characteristics in broiler chickens

Genetic selection has significantly improved the muscle development of fast-growing broiler chickens in the last 50 yr. However, improvement in muscle growth has coincided with relatively poor development of visceral systems, resulting in impaired ability to cope with high environmental temperatures. The aim of this study was to elucidate the effects of thermal manipulation (TM) during different periods of embryogenesis on chick hatchability, BW and thermoregulation upon hatching, on their ability to cope with thermal challenge at 42 d of age, and on carcass and breast meat traits. Control embryos were incubated at 37.8 degrees C. The TM embryos were incubated at 37.8 degrees C and treated for 3 h at 39.5 degrees C on the following days of embryogenesis: E8 to E10 [early (EA)], E16 to E18 [late (LA)], and both E8 to E10 and E16 to E18 (EA-LA). Body weight and body temperature (T(b)) were measured at hatching and throughout the growth period as well as during exposure of 42-d-old chickens to a thermal challenge at 35 degrees C for 6 h. The LA and EA chicks exhibited significantly lower T(b) than control chicks (37.9 vs. 38.2 degrees C) at hatching, but during the growth period, differences in T(b) between treated and control chicks decreased with age. Significant hyperthermia (over 44 degrees C) was monitored in all groups during the thermal challenge, but mortality was higher in treated than in control chickens. No effect of treatments on BW was found during the entire growth period. However, breast yield was higher in LA chickens than in controls at slaughter. The EA and EA-LA treatments slightly decreased the ultimate pH of breast meat, whereas the LA treatment had no effect. In conclusion, none of the TM conditions tested in the present study were able to improve long-term thermotolerance in chickens. Late treatment favored breast muscle growth without affecting ultimate pH and drip loss of breast meat.

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.

Comparison of three lines of broiler breeders differing in ascites susceptibility or growth rate. 1. Relationship between acoustic resonance data and embryonic or hatching parameters

Ascites is a prevalent cardiovascular disease among modern broilers with negative impacts on production and animal welfare. The peak of mortality due to ascites occurs at the end of the growing period, but the etiology of this problem may start during embryonic development. A few recent reports have demonstrated that the signs of ascites susceptibility are manifested during the late stages of incubation. In the current study, we used a nondestructive method based on egg acoustic resonance parameters [resonant frequency (RF) and damping] to establish a relationship between embryo physiological events during early development in broiler eggs and susceptibility to ascites. The hatching eggs of 3 broiler lines differing in ascites susceptibility were used for this study: ascites-resistant dam line (DAR), ascites-sensitive dam line (DAS), and ascites-sensitive sire line (SASL). These lines were selected on the basis of fast growth, high breast meat yield, and ascites induction at low temperatures such that the order of ascites susceptibility in terms of mortality was SASL >> DAS > DAR. Eggs were incubated under standard conditions in forced-draft incubators. We measured egg weights at setting, albumen pH, Haugh units (HU) at setting, and embryo weights at d 11 and 18, at internal pipping (IP), and at hatch. The durations of IP, external pipping (EP), and hatching were also determined. At 2 hourly periods during incubation, egg RF and damping were also measured. There were differences in egg weights between DAR and SASL vs. DAS, but albumen HU, albumen pH, and the ratio of yolk weight to egg weight were similar. There were differences in RF, damping, embryonic growth rates, and hatching events. Changes in resonant frequency and damping, which certainly suggest eggshell differences among lines, were not totally related to variations in physiological events during early and late embryonic development. A comparison between DAR and DAS, between DAS and SASL, or DAR and SASL indicates that sensitivity to ascites and selection for rapid growth rate in ascites-sensitive lines have different effects on embryonic parameters. We concluded that the sensitivity of broiler breeders to ascites does not influence egg internal quality, but the occurrence of ascites sensitivity in broilers could not be reliably predicted by early in ovo acoustic resonance parameters and hatching events.

Comparison of three lines of broilers differing in ascites susceptibility or growth rate. 2. Egg weight loss, gas pressures, embryonic heat production, and physiological hormone levels

Ascites is a metabolic disorder that accounts for over 25% of overall mortality in the broiler industry. This disorder is manifested between wk 5 and 6 posthatch, but there are previous indications that predisposition may be identified during embryonic development. In this current study, we determined embryonic physiological and metabolic parameters that may be associated with ascites predisposition. For this purpose, we used broiler eggs from 3 lines that differed in ascites sensitivity. These included an ascites-sensitive dam line (DAS), an ascites-resistant dam line (DAR), and an ascites-sensitive sire line (SASL). Eggs were incubated for 21 d under standard conditions. The following parameters were measured during incubation: egg weights at setting, egg weight losses at 18 d, embryo body weights and embryo heart weights throughout development, air cell partial gas pressures (pCO2 and pO2) levels at d 18 and at internal pipping (IP); plasma triiodothyronine, thyroxine, and corticosterone levels at d 18, IP, and hatch; heat production from d 17 until hatch, hematocrit values at hatch, and posthatch growth rate to 7 d along with hematocrit values. The data obtained revealed that selection for ascites sensitivity or rapid growth rate had no consistent influence on some of these parameters such that they could be wholly associated with ascites sensitivity for predictive purposes. Whereas differences in embryonic developmental patterns were apparent throughout embryonic development, these differences in physiological and metabolic parameters may be due partly to genetic differences unrelated to ascites sensitivity.

The effects of the spread of hatch and interaction with delayed feed access after hatch on broiler performance until seven days of age

Delay in access to feed for 1-d-old chicks impairs posthatch growth. It is a standard practice that 1-d-old chicks are deprived of feed for about 48 h before they are placed on farms. During incubation, there is a spread of 24 to 48 h for late versus early hatching. As spread of hatch increases, number of chicks that are feed-deprived for a longer time before free access (IA) to feed and water increases. In this current study, we investigated the effects of time delay in feed access on chick juvenile relative growth (RG: a measure of speed of growth) up to d 7, taking into consideration the duration of egg storage and spread of hatch. Our results confirmed that delay in feed access caused weight loss during holding time and depressed growth rate after access to feed. The magnitude of the effect depended on the hatching period within the hatching window. It also depended on whether the biological age (BA) or the chronological age (CA) of the chick was considered. Immediate access to feed produced significantly different results depending on CA or BA. Both ways, the method seemed to benefit the late hatchers. This finding contrasts with the effect of delayed feeding in which early hatchers benefited more. Long duration of egg storage depressed RG not only of chicks with immediate access to feed but also in those denied access after hatch. Delay in feed access significantly aggravated the effects of long egg storage duration on RG. Triiodothyronine levels were lower in feed-deprived chicks, and the effect was greater in late hatchers. It is concluded that the beginning of delay in feed access should be determined from the time of hatch not at the end of hatch. It is suggested that the adverse effects of delay in feed access can be reduced by providing a source of energy in hatching baskets or during transportation.

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.

Effects of turning duration during incubation on embryo growth, utilization of albumen, and stress regulation

Eggs from Cobb broiler breeders were incubated for 18 d. Eggs were not turned (T0) or were turned until 9 (T9), 12 (T12), 15 (T15), or 18 (T18) d. First, the effects of turning on embryo and albumen weights were studied. Samples of eggs were opened at d 9, 12, 15, and 18 for embryo and albumen weighing. The results show that embryos from unturned eggs had lower weights and higher remaining albumen weights than those from turned eggs. At d 18, albumen utilization was completed in the T12, T15, and T18 groups only. Also, further turning until d 15 and 18 increased embryo weights. The responsiveness of the embryo after adrenocorticotropic hormone (ACTH) injection was studied to test stress control in embryos. Blood samples were collected from embryos at 60 and 150 min after injection at d 12, 15, and 18 and were analyzed for corticosterone concentrations. The results showed that basal corticosterone levels increased with embryo age. At 60 min after ACTH injection, corticosterone levels were lower at d 12 than at d 15 and 18. At 150 min after ACTH injection, corticosterone levels followed different trends according to incubation stage and turning duration. The highest basal corticosterone levels were obtained with the T15 group at d 15 and 18. Also at d 18, corticosterone levels in the T15 group were the highest at 150 min after ACTH injection. We concluded that egg turning was required during incubation until d 12, at least, and should not be stopped until after d 15.

Changing Albumen-Membrane Adhesive Forces During Early Embryonic Development

Using acoustic resonance analysis, it is possible to detect embryonic development. In fertile eggs, the resonant frequency suddenly decreases after about 100 h of incubation. Previous research has shown that this decrease coincides with changing mechanical properties of the albumen near the shell, caused by the formation of subembryonic fluid (SEF). In the present experiment, the adhesive forces between the shell, the membranes, and the albumen were measured before and after the decrease in the resonant frequency. The adhesive forces between shell and outer membrane and between the 2 membranes remained constant, whereas the adhesive force between the inner membrane and the albumen, indirectly measured by a Kjeldahl analysis, increased significantly. Whether the decrease in resonant frequency is caused by the increase of adhesive force between albumen and inner membrane or by the changed properties of the membranes (both of which are altered by dehydration of the albumen) is still open for discussion.

Comparison of Embryo Physiological Parameters During Incubation, Chick Quality, and Growth Performance of Three Lines of Broiler Breeders Differing in Genetic Composition and Growth Rate

In broiler breeder management, stringent feed restriction is practiced to reduce body size in order to improve egg production and meet broiler production demand, but this practice has raised welfare issues. The potential for the dwarfing (dw) gene to reduce feed intake and body size of breeders under ad libitum feeding or less stringent restriction while maintaining improved egg production has been reported. In this study, we compared embryo physiology, quality of chicks, and performance of broilers from eggs of dwarf breeders with those from a standard broiler breeder. Hatching eggs from 3 commercial lines of broiler breeders were compared for incubation parameters, 1-d-old chick weight, chick quality, and broiler growth to 41 d of age. The lines included a standard heavy (S) line, an experimental (E) line, and a label-type (L) line. The E and L line breeders carry the sex-linked dw gene and are being used to assess the potential for dw to reduce feed intake or lower feed restriction and improve reproductive performance in heavy female broiler parent stock. Two separate experiments were conducted. All female parent stocks were mated to Cornish males, and fertile eggs were collected. In the first experiment, eggs were incubated for 21 d under standard conditions to determine, during final stages of incubation, corticosterone and thyroid hormone levels (triiodothyronine, T3; thyroxine, T4) in embryos and hatchlings, CO2 partial pressure (pCO2), and O2 partial pressure (pO2) in air cells, heat production by eggs and 1-d-old weights. In the second experiment, eggs were incubated for 21 d to compare chick quality, chick weights at 1 d of age, and broiler growth to 7 and 41 d. Average egg weights were higher for the S and L lines than the E line, but weight loss during incubation was lowest for the E line. Plasma T3 and T3/T4 ratio was similar between lines at IP, but corticosterone was higher in the S line. At hatch, T3/T4 ratio was higher in the S line compared with the E and L lines, but corticosterone was higher in the S and E lines than in the L line. Heat production by embryos was different among lines (S > E > L). The pCO2 was also higher in the S line than the E and L lines. These incubation parameters suggest different metabolic rates among lines (S > E > L). Incubation duration was shortest for the S line. Chick weights at 1 d old were not different between lines. Chick quality scores were also not different when expressed as a percentage of high-quality chicks or as an overall average score of each line. However, broiler BW at 7 and 41 d were different among lines (S > E > L). Chicks of higher quality (score of 100) in all lines had higher BW than those of lower quality (score of < 100). For corresponding quality groups between lines, the S line had higher BW, and those of the L had the lowest. These data suggest a link between the levels of embryo metabolism and growth potentials of the lines. We concluded that the dw gene has potential for reducing feed intake in heavy broiler parent stock (as in the E line), improving reproductive performance (as in the L and E lines), and maintaining progeny broiler chick weights at 1 d of age and quality but with lower weight at slaughter.