Transcriptomics analysis unveils key potential genes associated with brain development and feeding behavior in the hypothalamus of L-citrulline-fed broiler chickens

High ambient temperature is a major environmental stressor affecting poultry production, especially in the tropical and subtropical regions of the world. Nutritional interventions have been adopted to combat thermal stress in poultry, including the use of amino acids. L-citrulline is a nonessential amino acid that is involved in nitric oxide generation and thermoregulation, however, the molecular mechanisms behind L-citrulline's regulation of body temperature are still unascertained. This study investigated the global gene expression in the hypothalamus of chickens fed either basal diet or L-citrulline-supplemented diets under different housing temperatures. Ross 308 broilers were fed with basal diet (CON) or 1% L-citrulline diet (LCT) from day-old, and later subjected to 2 environmental temperatures in a 2 by 2 factorial arrangement as follows; basal diet-fed chickens housed at 24°C (CON-TN); L-citrulline diet-fed chickens housed at 24°C (LCT-TN); basal diet-fed chickens housed at 35°C (CON-HS), and L-citrulline diet-fed chickens housed at 35°C (LCT-HS) from 22 to 42 d of age. At 42-days old, hypothalamic tissues were collected for mRNA analyses and RNA sequencing. A total of 1,019 million raw reads were generated and about 82.59 to 82.96% were uniquely mapped to genes. The gene ontology (GO) term between the CON-TN and LCT-TN groups revealed significant enrichments of pathways such as central nervous system development, and Wnt signaling pathway. On the other hand, GO terms between the CON-HS and LCT-HS groups revealed enrichments in the regulation of corticosteroid release, regulation of feeding behavior, and regulation of inflammatory response. Several potential candidate genes were identified to be responsible for central nervous system development (EMX2, WFIKKN2, SLC6A4 Wnt10a, and PHOX2B), and regulation of feed intake (NPY, AgRP, GAL, POMC, and NMU) in chickens. Therefore, this study unveils that L-citrulline can influence transcripts associated with brain development, feeding behavior, energy metabolism, and thermoregulation in chickens raised under different ambient temperatures.

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.

Growth performance and physiological responses of broilers fed Stylosanthes hamata leaf meal in a hot tropical environment

BACKGROUND

Forage plants are considered an essential source of vitamins, protein and energy and could decrease the intake of the conventional diets by up to 10% if young quality forage plants are offered and about 7% of a broiler's daily protein needs and 3% of their daily calorie needs can be met by pasture. However, there is a paucity of data on the quantification of the herbage intake in broiler chickens.

OBJECTIVES

This trial was designed to determine the performance and physiological response of broilers fed diets containing Stylosanthes hamata leaf meal (SHLM) at 0%, 1%, 5%, 10%, 15% and 20% inclusion (weight for weight) in a basal diet of poultry.

METHODS

Two hundred and forty-day-old Arbor Acres broiler chicks were used for this trial. They were allocated at random to each of the 6 dietary treatment groups with 4 replicates of 10 chickens each. The study lasted for 35 days, during which data were collected weekly.

RESULTS

Results indicated no difference (p > 0.05) in body weight gain, feed consumption and feed conversion ratio of broiler chickens across all ages. Although the plasma triiodothyronine (T3 ) concentration of the birds was influenced at the sixth week of age, there was no consistency in the trend. At the eighth week of age, chickens on 15% SHLM had significantly (p < 0.05) higher cortisol (3.22 ng/mL) concentrations compared to 10% (3.13 ng/mL) and 20% (3.16 ng/mL) SHLM treatment groups. Treatment groups, regardless of the age of the chickens, had similar (p > 0.05) mean plasma creatinine values.

CONCLUSIONS

The study concluded that SHLM could be incorporated into broiler feed up to 20% without a deleterious impact on physiology and performance indices.

Global trends and research frontiers on heat stress in poultry from 2000 to 2021: A bibliometric analysis

Background: Heat stress remains a major environmental factor affecting poultry production. With growing concerns surrounding climate change and its antecedent of global warming, research on heat stress in poultry has gradually gained increased attention. Therefore, this study aimed to examine the current status, identify the research frontiers, and highlight the research trends on heat stress in poultry research using bibliometric analysis. Methods: The literature search was performed on the Web of Science Core Collection database for documents published from 2000 to 2021. The documents retrieved were analyzed for their publication counts, countries, institutions, keywords, sources, funding, and citation records using the bibliometric app on R software. Network analysis for co-authorship, co-occurrence, citation, co-citation, and bibliographic coupling was visualized using the VOSviewer software. Results: A total of 468 publications were retrieved, and over the past two decades, there was a gradual increase in the annual number of publications (average growth rate: 4.56%). China had the highest contribution with respect to the number of publications, top contributing authors, collaborations, funding agencies, and institutions. Nanjing Agricultural University, China was the most prolific institution. Kazim Sahin from Firat University, Turkey contributed the highest number of publications and citations to heat stress in poultry research, and Poultry Science was the most productive and the most cited journal. The top 10 globally cited documents mainly focused on the effects of heat stress, alleviation of heat stress, and the association between heat stress and oxidative stress in poultry. All keywords were grouped into six clusters which included studies on "growth performance", "intestinal morphology", "heat stress", "immune response", "meat quality", and "oxidative stress" as current research hotspots. In addition, topics such as; "antioxidants", "microflora", "intestinal barrier", "rna-seq", "animal welfare", "gene expression", "probiotics", "feed restriction", and "inflammatory pathways" were identified for future research attention. Conclusion: This bibliometric study provides a detailed and comprehensive analysis of the global research trends on heat stress in poultry over the last two decades, and it is expected to serve as a useful reference for potential research that will help address the impacts of heat stress on poultry production globally.

Effects of arginine replacement with L-citrulline on the arginine/nitric oxide metabolism in chickens: An animal model without urea cycle

BACKGROUND

This study examined the efficacy of L-citrulline supplementation on the arginine/nitric oxide metabolism, and intestinal functions of broilers during arginine deficiency. A total of 288 day-old Arbor Acre broilers were randomly assigned to either an arginine deficient basal diet (NC diet), NC diet + 0.50% L-arginine (PC diet), or NC diet + 0.50% L-citrulline (NCL diet). Production performance was recorded, and at 21 days old, chickens were euthanized for tissue collection.

RESULTS

The dietary treatments did not affect the growth performance of broilers (P > 0.05), although NC diet increased the plasma alanine aminotransferase, urate, and several amino acids, except arginine (P < 0.05). In contrast, NCL diet elevated the arginine and ornithine concentration higher than NC diet, and it increased the plasma citrulline greater than the PC diet (P < 0.05). The nitric oxide concentration in the kidney and liver tissues, along with the plasma and liver eNOS activities were promoted by NCL diet higher than PC diet (P < 0.05). In the liver, the activities of arginase 1, ASS, and ASL, as well as, the gene expression of iNOS and OTC were induced by PC diet greater than NC diet (P < 0.05). In the kidney, the arginase 1, ASS and ASL enzymes were also increased by PC diet significantly higher than the NC and NCL diets. Comparatively, the kidney had higher abundance of nNOS, ASS, ARG2, and OTC genes than the liver tissue (P < 0.05). In addition, NCL diet upregulated (P < 0.05) the mRNA expression of intestinal nutrient transporters (EAAT3 and PEPT1), tight junction proteins (Claudin 1 and Occludin), and intestinal mucosal defense (MUC2 and pIgR). The intestinal morphology revealed that both PC and NCL diets improved (P < 0.05) the ileal VH/CD ratio and the jejunal VH and VH/CD ratio compared to the NC fed broilers.

CONCLUSION

This study revealed that NCL diet supported arginine metabolism, nitric oxide synthesis, and promoted the intestinal function of broilers. Thus, L-citrulline may serve as a partial arginine replacement in broiler's diet without detrimental impacts on the performance, arginine metabolism and gut health of chickens.

Dietary L-citrulline modulates the growth performance, amino acid profile, and the growth hormone/insulin-like growth factor axis in broilers exposed to high temperature

Heat stress adversely affects the growth performance, muscle development, and protein metabolism in poultry. l-Citrulline (L-Cit), is a non-essential amino acid that is known to stimulate muscle protein synthesis under stress conditions. This study investigated whether L-Cit could influence the growth performance, amino acid profile, and protein metabolism in broilers exposed to high ambient temperature. In a 2 × 2 factorial arrangement, Arbor acre broilers (288 chickens) were fed with basal diet (CON) or 1% L-Cit supplemented diet and later subjected to either thermoneutral (TNZ: 24°C, 24 h/d) or heat stress (HS: 35°C for 8 h/d) environment for 21 days. The results showed that L-Cit diet promoted the body weight and body weight gain of broilers higher than the CON diet, and it further alleviated HS suppression of body weight and feed intake at certain periods (p &lt; 0.05). Plasma urea, uric acid, glucose, and total cholesterol were elevated during HS, whereas, the triglyceride content was decreased (p &lt; 0.05). Serum amino acids including citrulline, alanine, aspartate, and taurine were decreased by HS. L-Cit supplementation restored the citrulline level and alleviated HS induction of 3-methylhistidine (p &lt; 0.05). L-Cit supplementation increased the plasma growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentration, as well as the GH concentration in the breast muscle (p &lt; 0.05). The mRNA expression showed that HS elicited tissue-specific responses by upregulating some growth factors in the breast muscle, but downregulated the GH receptor, GH binding protein, and IGF-1 expression in the hypothalamus. L-Cit supplementation upregulated the GHRH and IGFBP2 expression in the hypothalamus. L-Cit also upregulated the expression of IGF-1R and IGFBP2 in the breast muscle of HS broilers. The total mTOR protein level in the breast muscle of HS broilers was also increased by L-Cit diet (p &lt; 0.05). Therefore, this study demonstrated that HS negatively affected the growth performance of broilers and dysregulated the expression of growth factors related to protein metabolism. Contrarily, L-Cit promoted the growth responses of broilers via its stimulation of circulating GH/IGF-1 concentration. To certain extents, L-Cit supplementation elicited protective effects on the growth performance of HS broilers by diminishing protein catabolism.

Functional roles of taurine, L-theanine, L-citrulline, and betaine during heat stress in poultry

Heat stress (HS) is an important environmental stress factor affecting poultry production on a global scale. With the rise in ambient temperature and increasing effects of global warming, it becomes pertinent to understand the effects of HS on poultry production and the strategies that can be adopted to mitigate its detrimental impacts on the performance, health, welfare, immunity, and survival of birds. Amino acids (AAs) have been increasingly adopted as nutritional modifiers in animals to ameliorate the adverse effects of HS. They are essential for protein synthesis, growth, maintenance, reproduction, immunity, stress response, and whole-body homeostasis. However, HS tends to adversely affect the availability, transport, absorption, and utilization of these AAs. Studies have investigated the provision of these AAs to poultry during HS conditions, and variable findings have been reported. Taurine, L-theanine, and L-citrulline are non-essential amino acids that are increasingly gaining attention as nutritional supplements in HS animals. Similarly, betaine is an amino acid derivative that possesses favorable biological properties which contributes to its role as a functional additive during HS. Of particular note, taurine is negligible in plants, while betaine, L-theanine, and L-citrulline can be found in selected plants. These nutrients are barely found in feed ingredients, but their supply has been shown to elicit important physiological roles including anti-stress effects, anti-oxidative, anti-inflammatory, gut promoting, and immunomodulatory functions. The present review provides information on the use of these nutritionally and physiologically beneficial nutrients as functional additives to poultry diets during HS conditions. Presently, although several studies have reported on the positive effects of these additives in human and murine studies, however, there is limited information regarding their utilization during heat stress in poultry nutrition. Therefore, this review aims to expound on the functional properties of these nutrients, their potentials for HS alleviation, and to stimulate further researches on their biological roles in poultry nutrition.

Research Note: Effects of dietary L-arginine on the production performance and gene expression of reproductive hormones in laying hens fed low crude protein diets

The present study was designed to investigate whether L-arginine (Arg) supplementation would influence the production performance and reproductive traits of laying hens fed low crude protein (LCP) diets. Hy-Line brown laying hens were randomly assigned to dietary treatments of control, LCP, and LCP supplemented with 0.05, 0.10, 0.15, or 0.20% Arg for 7 wk. The results showed no significant variations on the production performance, and relative organ indexes of hens. However, significant transcriptional and structural changes were evident along the HPG axis of hens. Arg supplementation linearly upregulated (P < 0.05) the gonadotropin-releasing hormone 1 (GnRH1), and gonadotropin inhibitory hormone in the hypothalamus. The pituitary growth hormone, GnRH receptor, and follicle-stimulating hormone (FSHβ) were also increased (P < 0.05). In the ovary, GnRH1, and estrogen receptor β were linearly increased by Arg, and the ovarian morphology revealed that LCP induced structural alterations which were minimally recovered by Arg supplementation. Serum insulin-like growth factor 1 (IGF-1) and nitric oxide (NO) were increased (P < 0.05) at higher levels of Arg supplementation. Therefore, supplementing high Arg (0.20%) to LCP hens influenced the ovarian morphology and modulated the gene expression of reproductive hormones in the hypothalamic-pituitary-gonadal axis of laying hens via actions that may be related to NO and IGF-1 activity.

Dietary L-citrulline influences body temperature and inflammatory responses during nitric oxide synthase inhibition and endotoxin challenge in chickens

Recent studies have revealed the role of L-citrulline (L-CIT) in thermoregulation, but very little is known about the mechanisms involved. In this study, nitric oxide synthase inhibition and endotoxin-induced fever were used to investigate the effects of L-CIT on body temperature and inflammatory responses. In experiment 1, NW-nitro-L-arginine methyl ester (L-NAME, 150 mg/kg BW), was i. p. injected into chicks fed with basal (CON) or L-CIT diets for 14 days. In experiment 2, Lipopolysaccharide (LPS, 2 mg/kg BW) was i. p. injected following 21d feeding with CON or L-CIT diets. In experiment 3, chickens were injected with either L-NAME, LPS, or L-NAME + LPS following 26 days feeding with CON or L-CIT diets. The rectal (RT), ear (ET), and core body temperature (CBT) of chickens were examined. Results showed that L-NAME effectively decreased the RT, ET, CBT, and plasma NO concentration. In contrast, LPS increased NO levels and initiated hyperthermia by increasing RT, ET, CBT, and PGE2 levels. L-CIT diet reduced the mean CBT in experiment 1 and diminished the NO level, PGE2 level, and mean RT in experiment 3. Co-administration of L-CIT + LPS upregulated IL-6 expression, whereas, LPS injection alone induced IL-10, IL-1β, and TLR4 gene expressions. Therefore, this study reveals that L-CIT-induced hypothermia was related to NO inhibition and a decrease in PGE2 concentration. Conversely, LPS induced hyperthermia was associated with an increase in both NO and PGE2 concentrations.

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.

Environmental stress and livestock productivity in hot-humid tropics: Alleviation and future perspectives

Tropical environments are characterized by persistently high temperature and relative humidity and the harsh environmental conditions pose a serious limitation on the optimal performance of the animals raised in this region. Heat stress causes deleterious effects on welfare, immunology and physiology of farm animals with a resultant impact on their productivity as the use of body resources is re-organized and the metabolic priorities of animals shift away from production, growth, health and reproduction. It is imperative to understand the mechanisms involved in the thermoregulation of animals under tropical conditions in order to develop appropriate strategies for their improvement. This review focuses on the available data on the increasing global temperature and the adverse impact of tropical conditions on animals' adaptive mechanism affected during thermal stress on production performance, intestinal and ileal microbiome, physiological responses, antioxidant system, metabolic responses, cellular and molecular response, adaptive mechanism strategies to heat stress and also strategies to palliate environmental stress on livestock under humid tropical conditions including environmental manipulation, genetic opportunity, epigenetic and feeding modification. Overall, the present review has identified the disturbance in the physiological indices of tropical livestock and the need for concerted efforts in ameliorating the adverse impacts of high ambient temperature aggravated by high humidity on livestock in tropical environments. Further research is needed on genotype-by-environment interaction on the thermotolerance of different livestock species in the tropics.

L-Citrulline Influences the Body Temperature, Heat Shock Response and Nitric Oxide Regeneration of Broilers Under Thermoneutral and Heat Stress Condition

Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Evaluation of access to different legume pastures on performance and welfare of broiler chickens during dry season under tropical environment

There have been a plethora of studies on the effects of access to runs on chickens’ welfare and behavioural repertoire with a paucity of information on the comparative advantage of various legume pasture and deep litter system. A total of 200‐day‐old unsexed Marshall Broiler chicks were weighed and assigned randomly into five experimental groups, viz. deep litter without access to run (DL), deep litter with access to Stylosanthes hamata (SH), Stylosanthes guanensis (SG), Mucuna pruriens (MP) and free run (FR) during dry season. Each treatment had 4 replicates of 10 birds. Data were collected on growth performance, behaviour, tonic immobility (TI), gait score and blood parameters. The data obtained were subjected to One‐Way Analysis of Variance in a Completely Randomized Design. Results showed that the final body weight of birds in SH was significantly higher (p ˂ .05) than those of SH, MP, FR and DL which were comparable. The feed intake of the birds of DL, SH and FR was higher than those of the other treatment groups. The feed conversion ratio (FCR) of the birds on legume pastures was lower than those without access to pasture. The birds of SH, SG and MP spent higher (p ˂ .05) time drinking, preening, dust‐bathing, spot pecking and walking standing behaviours while those in DL and FR spent more (p ˂ .05) time feeding. Generally, the gait score of the birds on the different legume pastures was similar but better than those without access to pasture. Tonic immobility of the DL birds was longer than that of FR whose duration was longer than those of the birds on the pastures. The study concluded that access to different legume pastures, particularly Stylosanthes hamata, improved the welfare of broiler chickens without adverse effect on the performance of the birds.

There is a scarcity of information on the comparative advantage of various legume pasture. Stylosanthes hamata improved the welfare of broiler chickens without adverse effect on the performance of the birds.

Blastodermal development, hatchability and chick quality of Marshall® broiler breeders of different flock ages during egg storage

The blastoderm, which represents the fertilized germinal disc, undergoes cellular events of division, differentiation and organization to achieve embryonic development in chickens. In this study, blastodermal cell counts and hatching performance of Marshall^® broiler breeders as influenced by flock age and egg storage were investigated. A total of 1,520 eggs from the flock ages, 43 weeks (younger) and 65 weeks (older), under similar management and nutritional regime were incubated after storage at 16°C with 75% relative humidity for duration of 0 (fresh eggs), 4, 7 and 10 days. Results show that total blastodermal cell counts (BCC) for both ages declined with increasing storage duration, with a sharp regression at 4d storage from younger breeders. Higher percentages of fertility and hatchability were recorded for younger breeders compared to older breeders. Percentage hatchability was statistically similar (p > .05) for both 43 weeks and 65 weeks old broiler breeders under 0, 4 and 7d storage except at 10d storage which was lower for older breeders. Chick lengths were longer with younger breeders whereas older breeders had heavier chick weights. Also, significant associations were found between BCC and fertility, hatchability of fertile eggs and chick weights, respectively, under different conditions. These results indicate that fresh eggs (0d) and short-term stored eggs (4- and 7 d) from 43 weeks old breeders had higher total blastodermal cell counts, fertility, hatchability and increased chick lengths compared to 65 week old breeders which produced heavier chicks. Therefore, egg storage longer than 7 days especially from older breeders resulted in modifications to the blastoderm which subsequently affected fertility, hatchability, embryo liveability and hatched chick quality. Also, detection of BCC in fertile eggs can serve as a predictive tool in fertility and hatchability evaluations.

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.

Early age thermal manipulation on the performance and physiological response of broiler chickens under hot humid tropical climate

Initial brooding temperature is critical for post-hatch growth of broiler chickens. A study was conducted to investigate the early age thermal manipulation (EATM) on the performance and physiological responses broiler chickens under hot humid tropical climate. A total of 260 unsexed day-old Arbor-acre broiler chicks were assigned to five thermal treatments of brooding temperature regimens having 4 replicates of thirteen birds each. The heat treatments were: initial brooding temperature of 35 °C for the first 2 days, and then decreased subsequently, gradually to 22 °C at 21 d of age (CT), initial temperature of 35 °C, sustained for the first 4 days and then decreased gradually (conventionally) (FD), initial temperature of 35 °C for the first 7 days (SD), the birds in CT, but the brooding temperature was raised to 35 °C again for another 3 days from day 7 (SD3), initial brooding temperature of 35 °C for the first 10 days (TD). Data were collected on daily feed intake and weekly body weights. Blood samples were collected from 8 birds per treatment weekly for the determination of plasma uric acid, triglycerides, triiodothyronine (T₃) and creatinine kinase. Data obtained were laid out in a Completely Randomized Design (CRD). Results showed that the final weights of the birds in FD were higher (P < 0.05) than those of the other treatments at the finisher phase. Feed intake of the birds in FD was higher than those of SD3 and TD. FCR of broiler chickens in CT, SD, SD3 and TD was higher than that of FD. The rectal temperature, plasma MDA and blood glucose of the thermally challenged birds in FD was generally better (P < 0.05) than those of the other treatments. It was concluded that EATM can be used to improve performance and also protect broiler chickens from acute heat stress at market age.

Reproductive performance of layer chickens reared on deep litter system with or without access to grass or legume pasture

Despite several studies carried out to investigate the effects of access to pasture on poultry performance, there is a dearth of information on the comparative benefit of grass and legumes. This study investigated the effects of rearing systems [deep litter system (DL), deep litter with access to legumes (LP) or grass (GP) pastures] on the performance of ISA Brown layers. Two hundred and forty 12-week-old pullets were housed for this study. They were reared until 60 weeks of age. Eighty birds were assigned to each treatment; each treatment had four replicates of 20 birds each. Two birds per replicate were slaughtered at weeks 20, 35 and 58 for determination of the weights of liver, ovary, oviduct and the number of follicles. Daily egg production records were kept from the day of first egg to 42 weeks in lay. Body weights were recorded weekly. Results indicated that at 20 weeks of age, the hens kept in the LP had higher (p < 0.05) ovary weight (g) (34.98 ± 1.4), oviduct weight (52.55 ± 2.28) and oviduct length (cm) (49.73 ± 11.34), and higher number of large yellow follicles (3.75 ± 1.31) and small yellow follicles (12.75 ± 5.17) than those in the GP (0.83 ± 0.02, 1.68 ± 0.19, 16.38 ± 1.14, 0.00 and 0.00), and DL (1.03 ± 0.11, 1.48 ± 0.48, 14.43 ± 0.58, 0.00 and 0.00) respectively. The age (days) at first oviposition was earlier (p < 0.05) in the LP (139.25 ± 0.85) than that in the GP (146.75 ± 0.48) and DL (146.75 ± 0.48). The hen-day egg production was lower (p < 0.05) in GP (74.19 ± 1.25) than that in the DL (78.82 ± 0.78) and LP (79.93 ± 1.13) at mid-laying phase. Concentrate feed intake was lower (p < 0.05) in LP and GP than DL suggesting economic benefit. It was concluded that access to LP enhanced the performance of layers than DL and GP as indicated by the parameters measured.

An analysis of the ruminal bacterial microbiota in West African Dwarf sheep fed grass- and tree-based diets

AIMS

To measure the impact of supplementing a forage diet with tree-based browse on the ruminal bacterial communities of Nigerian West African Dwarf (WAD) sheep.

METHODS AND RESULTS

Fifteen WAD sheep were fed a control diet of forage (Panicum maximum), with 12 animals shifted in groups of three to one of four browse-supplemented diets (Albizia saman, Bridelia micrantha, Ficus sur, or Gmelina arborea). These browse plants were shown in a concurrent but separate study to be reasonably nutritious (based on chemical composition and fibre constituents) and nontoxic (based on tannin, phytate, saponin, alkaloid and oxalate levels). Rumen liquids and solids for DNA extraction were collected via intubation from two animals in each group before and after dietary shift. Bacterial 16S rRNA gene regions V6-V8 were sequenced by 454 pyrosequencing. All communities were highly diverse and dominated by the phyla Firmicutes, Bacteroidetes, Tenericutes, Actinobacteria and Proteobacteria. All communities shared members of the genera Butryivibrio, Prevotella and Ruminococcus. Our analysis defined a core sets of bacteria shared by all animals, forage-fed animals and browse-fed animals. Community structure shifted dramatically in animals fed A. saman or G. arborea.

CONCLUSIONS

The impact of tree-based browse on the ruminal bacterial community of Nigerian WAD sheep varies by browse species, likely due to differences in browse composition.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study describes the first neotropical small ruminant bacterial microbiome and supports diet supplementation with specific tree-based browse for WAD sheep.

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.

Acid–base balance in chicken embryos (Gallus domesticus) incubated under high CO2 concentrations during the first 10 days of incubation

Recent studies show the importance of differential CO2 levels during the first half of incubation of chicken eggs on embryonic and postnatal growth. However, it is not known how external higher CO2 levels affect embryonic acid-base balance. In this study, the effect of an early rise in CO2, between 25th and 96th hour of incubation to 1.5% and maintained at that level until 240 h of incubation, was investigated on air cell gases, blood gas parameters from ED10 onwards and on embryonic growth and hatching parameters. Higher external CO2 concentrations resulted in a faster acidification of albumen resulting in a faster decrease of albumen pH with development, illustrating the capacity of albumen to cope with higher environmental CO2. Moreover, PCO2 in blood was higher in CO2 incubated embryos at embryonic day 10 and 11 but without a change in blood pH. The additional increase in plasma HCO3- concentration at day 10 and 11 was responsible for buffering the higher PCO2 in CO2 incubated embryos in order to stabilize pH. However, effects of hypercapnia on blood acid-base parameters extinguished 2 days after termination of high CO2 incubation. Embryonic growth was modestly accelerated which was reflected in higher embryonic weights at day 6 and 10 and a significant earlier hatching; hatchling weights were not different between treatment groups.

The chicken pituitary-specific transcription factor PIT-1 is involved in the hypothalamic regulation of pituitary hormones

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and trans-activates promoters of growth hormone- (GH), prolactin- (PRL) and thyroid stimulating hormone-beta- (TSHbeta) encoding genes. Thyrotropin-releasing hormone (TRH) is located in the hypothalamus and stimulates TSH, GH and PRL release from the pituitary gland. In the present study, we successfully used the cell aggregate culture system for chicken pituitary cells to study the effect of TRH administration on the ggPit-l* (chicken Pit-1), GH and TSHbeta mRNA expression in vitro. In pituitary cell aggregates of 11-day-old male broiler chicks the ggPit-l * mRNA expression was significantly increased following TRH administration, indicating that the stimulatory effects of TRH on several pituitary hormones are mediated via its effect on the ggPit-l* gene expression. Therefore, a semiquantitative RT-PCR method was used to detect possible changes in GH and TSHbeta mRNA levels. TRH affected both the GH and TSHbeta mRNA levels. The results of this in vitro study reveal that ggPit-1 * has a role in mediating the stimulatory effects of TRH on pituitary hormones like GH and TSHbeta in the chicken pituitary.

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.

Regulation of growth hormone expression by thyrotropin-releasing hormone through the pituitary-specific transcription factor Pit-1 in chicken pituitary

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and trans-activates promoters of growth hormone- (GH), prolactin- (PRL) and thyroid stimulating hormone beta- (TSHbeta) encoding genes. Pit-1 has been identified in several mammalian and avian species. Thyrotropin-releasing hormone (TRH) is located in the hypothalamus and it stimulates TSH, GH and PRL release from the pituitary gland. In the present study, we successfully developed a competitive RT-PCR for the detection of Pit-1 expression in the chicken pituitary, that was sensitive enough to detect picogram levels of Pit-1 mRNA. Applying this method, the effect of TRH injections on Pit-1 mRNA expression was determined in the pituitary of chick embryos and growing chicks. In both 18-day-old embryos and 10-day-old male chicks the Pit-1 mRNA expression was significantly increased following TRH injection, thereby indicating that the stimulatory effects of TRH on several pituitary hormones is mediated via its effect on Pit-1 expression. Therefore, a semi-quantitative RT-PCR method was used to detect possible changes in GH levels. TRH affected the GH mRNA levels at both developmental stages. These results, combined with the data on Pit-1 mRNA expression, indicate that Pit-1 has a role in mediating the stimulatory effects of TRH on pituitary hormones like GH.

Protein and energy requirements of pre-weaned West African dwarf goats fed soyabean diet as a replacement for milk in a tropical environment

Twenty-one early-weaned West African dwarf goats weighing between 1.0 and 1.5 kg at birth were used to assess the protein and energy requirement of pre-weaned West African Dwarf (WAD) goats fed soyabean diet. Three isonitrogenous diets (24%) were prepared such that dried whole-milk protein was replaced by corn starch and soyabean concentrate protein at 0.0%, 25.0% and 50.0% levels such that a 14.5% total solid solution was obtained for each diet. Results indicated that a daily digestible energy (expressed as kcal/day/W0.75 kg) intake of 58.2, 63.7, 98.5 and 114.6 kcal was required for maintenance, while a corresponding value of 7.37, 4.50, 2.18 and 1.91 kcal was required per day per gram live weight gain by the kids at 4, 6, 9 and 13weeks old, respectively. Similarly, a digestible crude protein (DCP) intake of 3.59 g/day/W0.75 kg) appeared to be adequate for maintenance of the kids between 0 and 13 weeks, while 0.34 g/day/W0.75 kg of DCP intake was required per day per gram live weight.

Co-expression of messenger ribonucleic acids encoding IGF-I, IGF-II, type I and II IGF receptors and IGF-binding proteins (IGFBP-1 to -6) during follicular development in the ovary of seasonally anoestrous ewes

In recent years, it has become apparent that components of the insulin-like growth factor (IGF) system are involved in the regulation of ovarian follicular development in sheep. The majority of previous studies have concentrated on investigating only a select few components and not the whole system. The aim of the present study was to use five seasonally anoestrous ewes to investigate the expression of mRNA encoding all 10 components of the sheep IGF system among various-sized follicles within the ovary, using sheep-specific ribonucleotide probes and in situ hybridisation. IGF-I mRNA expression was low and did not vary with follicle size. IGF-II mRNA expression was significantly higher (P < 0.05) in small follicles compared to large follicles. Both IGF receptors had significantly higher (P < 0.05) levels of mRNA expression in small follicles, with the type I receptor being expressed to a slightly greater extent than the type II receptor. IGFBP-2, -3, -4 and -5 gene expression followed a similar pattern to IGF-II and the IGF receptors, whereby expression decreased with increasing follicle size. Similar to IGF-I, IGFBP-6 mRNA expression showed little variation with follicle size. IGFBP-1 mRNA expression was observed at low and constant levels, albeit in small and medium-sized follicles only. These data demonstrate that all of the components of the IGF system are produced in the ovine follicle, and for some of the components, their gene expression varied with stage of follicle development. This study further emphasises the importance of IGF-II as the major IGF in the autocrine and paracrine regulation of follicle development in sheep.

Developmental changes in inhibin α and inhibin/activin βA and βB mRNA levels in the gonads during post-hatch prepubertal development of male and female chickens

Dimeric inhibins and activins are barely detectable in the plasma during prepubertal development of male and female chickens. This may be misconstrued to indicate that the proteins are not produced in the gonads and have no functional significance during this period. Very few studies have actually determined the mRNA expression profile of the inhibin and activin subunits in the gonads prior to puberty in order to establish their secretion at the local level and postulate potential roles for the inhibin and activins at this developmental stage. In this study, the expression of the mRNA for the alpha-, betaA-, and betaB-subunits was determined in the ovary and testis of chickens during prepubertal development. Gene expression was determined at 3, 5, 6, 8, 10, 12, 16, and 18 weeks of age by RT-PCR. Messenger RNA level was quantified by competitive RT-PCR at 3, 6, 12, and 18 weeks of age in order to detect any changes with development, suggest potential relationship to the profile of dimeric inhibins and activins reported previously and to suggest potential paracrine and endocrine roles for them. The results show that all the inhibin/activin subunit mRNAs are expressed in the testis of the chicken throughout the period of prepubertal development up to 18 weeks of age. However, in the ovary, only the betaA- and betaB-subunits were detected at all ages whereas the alpha-subunit mRNA could only be detected just before puberty. Quantification of the mRNA levels showed variation of each subunit with age. These temporal changes suggest relationship with paracrine functional role in the ovary or the testis. Quantitative changes in expression levels also suggests that there may be some relationship between mRNA levels and the type and amount of dimeric inhibins and activins produced at any developmental stage. There are major differences between the male and female gonads in the timing of the expression of different subunits. In conclusion, the expression of the mRNA subunits in the testis and ovary suggests that inhibins and activins are being produced but may be principally involved in autocrine/paracrine function within the gonads.

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.

BMPs and BMPRs in chicken ovary and effects of BMP-4 and -7 on granulosa cell proliferation and progesterone production in vitro

Bone morphogenetic proteins (BMPs) and their receptors (BMPRs) are now known to have important roles in mammalian ovarian folliculogenesis. This study determined the expression of the mRNA encoding for BMPs and their receptors in the chicken ovary and explored possible roles for them. The expression of the mRNA for BMP-2, -4, -6, -7, and BMPR-IA, -IB, and -II was determined and quantified by a semiquantitative RT-PCR. The mRNAs for all the BMPs and receptors determined were present in both the granulosa (G) and theca (T) cells of the F1, F2, and F3 follicles. All BMP mRNAs increased in G cells with follicular development, whereas only BMP-7 mRNA had this trend in the T cells. BMP-2, -4, and -6 mRNAs in T were similar between follicles. BMPR-IA mRNA was similar in F2G and F3G but lower in F1G. BMPR-IB mRNA was similar in G of all follicles, and BMPR-II mRNA increased with development. In the T, each receptor subtype showed equal distribution between follicles. mRNA levels for BMPR-IB and -II were higher in G than in T, suggesting that the G is a major target for BMPs. BMP-4 and -7 stimulated basal, IGF-I-, and gonadotropin-stimulated progesterone production by cultured G cells, with differential responses between cells from the F1 and F3/4. This suggests involvement in follicular differentiation. BMP-4 and -7 reversed the inhibitory effects of transforming growth factor (TGF)-alpha on basal and gonadotropin-stimulated G cell progesterone production, with greater effect in the F1 than in the F3/4. This effect suggests an important role for BMPs interacting with TGF-alpha in modulating the effects of gonadotropins and IGF-I on follicular differentiation. Finally, BMP-7 stimulated G cell proliferation, but BMP-4 inhibited TGF-alpha+ IGF-I- and/or FSH-stimulated G cell proliferation, suggesting a role in the control of follicular growth during development. These effects of BMP-4 and -7 on the G cell function showed relationships with the expression levels of the BMPs and the BMPR-II.

mRNA expression of components of the IGF system and of GH and insulin receptors in ovaries of broiler breeder hens fed ad libitum or restricted from 4 to 16 weeks of age

An evaluation of the insulin-like growth factors (IGF) system in the ovaries of heavy breeder hens during the growing phase was performed to measure the effect of feed restriction. The transcripts of IGF-I, IGF-II, IGF receptor (IGF-R), two IGF binding proteins (IGFBP-2 and IGFBP-5), GH receptor (GH-R) and insulin receptor (I-R) were measured by RT-PCR at 4, 8, 12 and 16 weeks of age in the ovaries of ad libitum fed and feed restricted hens. The transcripts of all genes screened were detected in all feed regime groups and at all ages sampled. However, no significant overall effects of feed restriction on these transcripts were found despite the marked difference in body growth (200% at 16 weeks of age). Similarly there were no significant age effects except for the expression of GH-R-that showed a decrease after 8 weeks of age (P<0.01). Although feed restriction seems to have a relatively limited effect on the expression of these components of the ovarian IGF system in juveniles, a more detailed determination is necessary to determine possible changes nearer to sexual maturity (16 weeks of age onwards). It is concluded that components of the IGF system, GH or insulin may not be involved in the mechanisms that, through restricted feeding, alter ovarian development and function during growth to enable better reproductive performance during lay.

Regulation of inhibin alpha- and beta(A)-subunit messenger ribonucleic acid levels by gonadotropins and IGF-I in cultured chicken granulosa cells

A quantitative competitive reverse transcription polymerase chain reaction assay (QC RT-PCR) for quantifying the absolute levels of the expression of inhibin alpha- and beta(A)-subunits in chicken granulosa cells showed that these subunits are expressed in different amounts depending on follicular maturation. The present study determined the regulation of the expression of these subunits. The individual effect of different doses of IGF-I, LH or FSH (1-100 ng/ml) or the combination of IGF-I with either LH or FSH at different concentrations, on the expression of inhibin alpha- and beta(A)-subunit was determined on cultured granulosa cells of F(1) and the combined F(4)+F(5) follicle. Cells were cultured for 48 h in 6-well plates with or without added hormones. Culture medium was discarded, cells were washed and total RNA was extracted from the cells. Five hundred nanograms of total RNA was reverse transcribed using specific primers and coamplified with an internal standard, as described previously, to determine expression level in the cells. IGF-I, LH, and FSH enhanced the inhibin alpha-subunit mRNA levels in a dose dependent manner in both F(1) and the combined F(4)+F(5) whereas inhibin beta(A)-subunit was not affected. The effects of FSH, LH were more expressed in F(1) follicles compared to F(4)+F(5) on the alpha-subunit. The addition of IGF-I and either LH or FSH during the culture period significantly increased the stimulatory effects of both LH and FSH on the expression of inhibin alpha-subunit in F(1) follicles but had no significant effect on the inhibin beta(A)-subunit. The results suggest that the changing expression levels of inhibin alpha-subunit during follicular development are the result of the regulatory effect of the interaction between IGF-I and the gonadotropins and that the regulation of this subunit may be the main factor for the regulation of the protein inhibin levels. Other factors may be also implicated in the changing expression levels of the beta(A)-subunit.

Developmental expression of activin/inhibin alpha- and beta(A)-subunit genes in the gonads of male and female chick embryos

The expression of inhibin alpha- and beta(A)-subunits was investigated in gonads of male and female chick embryos during the last week of their 21-day incubation period. Fertilized Hisex brown laying hen eggs were incubated at 37.8 +/- 0.2 degrees and 60% relative humidity in an automatic forced-draft incubator with constant lighting. Embryos were killed after 14, 18, and 21 days of incubation, sexed by macroscopical inspection of the gonadal phenotype, and further dissected to obtain the gonads. Total RNA was isolated using the ultraspec RNA method. The expression of alpha- and beta(A)-subunits was evaluated by competitive RT-PCR. Significant differences were found within and between sexes in the expression of the alpha- and beta(A)-subunits. The level of the alpha-subunit in the testis was about 23-fold higher than that in the ovary at all ages. Testicular content of inhibin alpha mRNA levels was similar at days 14 and 18 but declined significantly at day 21 of incubation, whereas no significant differences were observed between the three age groups in the ovary. Testicular and ovarian inhibin beta(A)-subunit increased significantly from day 14 to day 18 followed by a significant decline before hatch. However, inhibin beta(A) level at day 14 was significantly higher in the ovary than in the testis. At days 18 and 21, there were no differences in the levels of the inhibin beta(A) in the sexes. The expression of inhibin beta(A)-subunit in the ovary was significantly higher than that of the alpha-subunit at all ages. In the testis, however, the expression of the beta(A)-subunit was higher at days 18 and 21 than at day 14. The sex difference in gonadal inhibin subunits expression suggests differential roles of inhibin/activin in the development of the chicken gonads. The changing level of expression during incubation also suggests changing biological roles within sexes.

Quantification of growth hormone receptor extra- and intracellular domain gene expression in chicken liver by quantitative competitive RT-PCR

The very sensitive competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to investigate the expression of the extracellular (GHRe) and intracellular (GHRi) parts of the growth hormone receptor (GHR) in the liver tissue of chickens. Two competitors (internal standards), pGHRi MUT and pGHRe MUT, specific to the GHRi and GHRe genes, respectively, were constructed by site-specific mutagenesis. The internal standards defined PCR products of 394 bp for the pGHRi MUT and 330 bp for the GHRe MUT. These were used as competitors to the wild-type GHRi or GHRe which defined PCR products of 382 and 328 bp, respectively. Coamplification, under standardized conditions, of the native RNA in competition with serial dilutions of the mutant RNA in the same PCR reaction followed by enzymatic digestion produced the expected sizes of internal standard cDNA and predicted target cDNA. Expression levels of GHRe and GHRi were determined from standard curves generated. The method was sensitive enough to detect expressions down to picogram levels. Applying this method, the effect of GH and T(3) injection on GHRe and GHRi mRNA expression was determined in the liver of adult female Hisex birds and 1-day-old normal and dwarf chickens. Intravenous GH injection (25 microg/kg body weight) increased plasma levels of GH in Hisex birds after 10 min but rapidly decreased at 60 min followed by an increase in T(3). GH injection significantly increased the expression of the GHRe 60 min after injection but not at 10 min, when the GH level in plasma was high. In the liver of saline-treated dwarf (dw) and nondwarf (Dw) chicks, the level of expression of GHRe was similar in both strains despite disparate levels of basal GH and T(3). However, the level of GHRi was higher in Dw than in dw chicks. Although GH levels increased in both strains after intravenous GH injection (250 microg/kg body wt), the expression of GHRe in both strains was unaffected. However, the mRNA for the GHRi was significantly depressed by injection in the Dw but unaffected in dw chicks. Intravenous injection of T(3) (0.5 and 5 microg/kg body wt) increased plasma levels in both strains but caused depression of GHRi in Dw but not in dw chicks. T(3) injections had no effect on GHRe in either Dw or dw chicks. It is concluded that the expression of the GHRe in adult chickens is GH regulated either directly or indirectly. In contrast, in 1-day-old chicks, GH or T(3) had no effects on the GHRe but regulated the expression of GHRi in Dw chicks, whereas in dwarf chicks both had no effect on GHRe or GHRi expression. It is postulated that GHRe and GHRi gene expression may be regulated by different agonists/antagonists in different strains and depending on the age of the chicken.

Complementary DNA cloning and ontogenic expression of pituitary-specific transcription factor of chickens (Gallus domesticus) from the pituitary gland

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and transactivates promoters of growth hormone (GH)-, prolactin (PRL)-, and thyroid-stimulating hormone-beta (TSHbeta)-encoding genes. Pit-1 has been identified in several mammalian species. In birds, it has been identified only in the turkey and chicken pituitary. Several (gg) Pit-1 cDNA sequences have been identified in the anterior pituitary of the chicken (Gallus domesticus). As in turkey, three different transcripts (ggPit-1*, ggPit-1beta*, and ggPit-1W*) of the Pit-1 gene were identified. This suggests that the chicken pituitary expresses more variants than reported earlier. Previous studies have concentrated on expressions during posthatch life of the turkey and chicken. The present study has determined the ontogeny of Pit-1 during the embryonic life of the chicken (day 1-day 21 of incubation). The mRNA for Pit-1 was first detected in the pituitary on day 5 of embryonic life. The expression of the mRNA was maintained until hatch. The presence of Pit-1 at this stage of embryonic development suggests that Pit-1 may be physiologically important during embryonic development of birds, as it precedes the gene expression and secretion of GH, PRL, and TSHbeta. A similar sequence for the expression of Pit-1 relative to GH and PRL during embryonic/fetal development has been reported for rodents.

Effect of TNF-alpha on LH and IGF-I modulated chicken granulosa cell proliferation and progesterone production during follicular development

This study demonstrates the effects of recombinant human tumour necrosis factor a (rhTNF-alpha) and conditioned medium of the HD11-transformed chicken macrophage cell line on cultured chicken granulosa cells. Effects were studied on basal, IGF-I- and LH-stimulated progesterone production and cell proliferation. Recombinant human TNF-alpha stimulated basal progesterone production in a dose-dependent manner in the granulosa cells of the largest follicle but had no effect on cells from the third largest follicle. TNF-alpha stimulated and sometimes inhibited progesterone production stimulated by IGF-I and LH alone or in combination depending on the size of the follicle and the concentration of LH or IGF-I applied. However, the inhibitory effect of TNF-alpha was significantly more pronounced in cells from the third largest follicle when high concentrations of IGF-I, LH or a combination of both were applied. TNF-alpha had no effect on basal cell proliferation in both the largest and the third largest follicles, but regulated responses to IGF-I and a combination IGF-I and LH in the cells of the third largest follicle but not those of the largest follicle. The data indicate that the normal hierarchy of follicles is maintained in the chicken ovary through the regulation of the activity of IGF-I and its interaction with LH. Conditioned medium of LPS-activated HD11 macrophages mimicked the effects of TNF-alpha and its interaction with IGF-I and LH on progesterone production and cell proliferation. The observation that the HD11-conditioned medium contained TNF-alpha indicates that TNF-alpha produced by macrophages found in chicken follicles modulates granulosa cell growth and differentiation.

Effect of TNF-alpha on LH and IGF-I modulated chicken granulosa cell proliferation and progesterone production during follicular development

This study demonstrates the effects of recombinant human tumour necrosis factor a (rhTNF-alpha) and conditioned medium of the HD11-transformed chicken macrophage cell line on cultured chicken granulosa cells. Effects were studied on basal, IGF-I- and LH-stimulated progesterone production and cell proliferation. Recombinant human TNF-alpha stimulated basal progesterone production in a dose-dependent manner in the granulosa cells of the largest follicle but had no effect on cells from the third largest follicle. TNF-alpha stimulated and sometimes inhibited progesterone production stimulated by IGF-I and LH alone or in combination depending on the size of the follicle and the concentration of LH or IGF-I applied. However, the inhibitory effect of TNF-alpha was significantly more pronounced in cells from the third largest follicle when high concentrations of IGF-I, LH or a combination of both were applied. TNF-alpha had no effect on basal cell proliferation in both the largest and the third largest follicles, but regulated responses to IGF-I and a combination IGF-I and LH in the cells of the third largest follicle but not those of the largest follicle. The data indicate that the normal hierarchy of follicles is maintained in the chicken ovary through the regulation of the activity of IGF-I and its interaction with LH. Conditioned medium of LPS-activated HD11 macrophages mimicked the effects of TNF-alpha and its interaction with IGF-I and LH on progesterone production and cell proliferation. The observation that the HD11-conditioned medium contained TNF-alpha indicates that TNF-alpha produced by macrophages found in chicken follicles modulates granulosa cell growth and differentiation.

Insulin-like growth factors in the regulation of avian ovarian functions

In the past three decades, overwhelming evidence has accumulated to show that insulin-like growth factor (IGF)-I and -II, their receptors and binding proteins (IGFBP) (the IGF system), have major roles to play in the regulation of ovarian function in mammals. Although studies in birds did not start until 5-6 years ago, the limited information thus far available suggests that the IGFs act as autocrine/paracrine regulators of follicular growth and differentiation, just as observed in mammals. The genes for IGF-I and -II, type-I IGF receptor, IGFBP-2, and IGFBP-5 are expressed in both granulosa and theca cells of the chicken ovary. The mechanisms by which the IGF system controls ovarian function in the avian species are complex and involve interactions with the gonadotrophins (LH and FSH), growth hormone, and even other growth factors. Effects are different between strains and nutritional status.

Differential effects of amount of feeding on cell proliferation and progesterone production in response to gonadotrophins and insulin-like growth factor I by ovarian granulosa cells of broiler breeder chickens selected for fatness or leanness

Strain differences in reproductive performance were demonstrated between broiler breeder female chickens selected for growth (GL line) or for food conversion efficiency (FC line) and the improvement in reproductive performance due to feed restriction also differed significantly. Feed allowance effects on the maturation of ovarian follicles, the incidence of atresia and egg production differed between the two lines exposed to similar feeding protocols. Feed restriction reduced body weights significantly and to a similar extent in both GL and FC lines. The number of normal and atretic yellow follicles was significantly higher under ad libitum feeding and in GL line than it was in the FC line. In both lines, feed restriction decreased multiple ovulation and increased egg production. In culture, granulosa cells from the three largest follicles (F1, F2 and F3) increased progesterone production in response to LH, FSH and insulin-like growth factor I but responses were different between the GL and FC lines fed either ad libitum or restricted diets. Granulosa cells from the two or three largest follicles in GL and FC (ad libitum) lines produced similar amounts of progesterone in response to LH, FSH and insulin-like growth factor I whereas, in restricted birds, the progesterone production was of the rank order F1 > F2 > F3 in both lines. The responsiveness of the GL line fed ad libitum was higher for LH than for either FSH or insulin-like growth factor I but in the GL line fed a restricted diet, it was high for all the hormones. In the FC line, responses to LH, FSH or insulin-like growth factor I were high in ad libitum-fed birds, but low in birds fed a restricted diet for all hormones. Insulin-like growth factor I combined with LH or FSH significantly increased the progesterone production of granulosa cells from birds fed restricted diets of both lines and this effect increased with increasing follicular size. There was a lack of interaction between insulin-like growth factor I and LH or FSH in the regulation of progesterone production by birds of both lines fed ad libitum. Insulin-like growth factor alone or in combination with LH or FSH increased granulosa cell proliferation in birds fed ad libitum more than it did in birds fed restricted diets. The greater proliferation rate of granulosa cells of chickens fed ad libitum, in response to insulin-like growth factor I alone or in combination with gonadotrophins, leading to the simultaneous differentiation of two or three large follicles with high progesterone production in response to LH or insulin-like growth factor I, accelerates the rate of maturation of follicles. This may also be the major cause of erratic and multiple ovulations in broiler breeder female chickens fed ad libitum. In conclusion, insulin-like growth factor I, alone or in combination with LH or FSH, is an important component in the control mechanisms for follicular development in broiler breeder hens. It is this component that is targeted by feed allowance and inadvertently altered by selection for growth.

Quantification of inhibin/activin alpha and betaA subunit messenger ribonucleic acid by competitive reverse transcription-polymerase chain reaction in chicken granulosa cells during follicular development

The very sensitive quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to investigate the expression of inhibin/activin subunits in the granulosa cells of developing ovarian follicles of the hen. Two competitors specific to inhibin alpha and betaA subunits were constructed. In one study, the expression of inhibin alpha and betaA genes was determined in the granulosa cells of the five largest yellow follicles (F1, F2, F3, F4/5), the small yellow follicles (SYF), and the large white follicles (LWF) of a layer strain of chickens. Competitive RT-PCR for inhibin alpha subunit revealed 10.35 +/- 2.15 pg/ microg total RNA in the LWF. The expression increased 40-fold in the SYF and remained at that level in the F4/5 but decreased markedly thereafter up to the F1 stage. Inhibin/activin betaA subunit was also detected in the LWF in low amounts and showed no significant increase until the F2 stage. The highest level was found in the F1. The pattern of the mRNA for alpha and betaA subunits in the five largest follicles (F1, F2, F3, F4/5) of a broiler breeder strain of chicken was compared with that in the layer strain. Expression of the alpha subunit was significantly higher in the three largest follicles (F1, F2, F3) of the broiler breeder hens, but only in the F2 for the betaA. The results suggest that inhibin alpha may play an important role in the recruitment and differentiation of follicles and that differences between broiler breeders and layers may have consequences at both the pituitary and ovarian levels.

The expression of transforming growth factor alpha receptor protein and its activation in chicken ovarian granulosa cells of maturing follicles

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) are structurally related growth factors that exert their biological actions by binding to the same cell-surface receptor, EGF receptor. However, in chicken cells, human EGF binds with approximately 100-fold lower affinity than human TGF-alpha. In a previous study, we localized EGF/TGF-alpha receptor immunohistochemically in the granulosa and theca of the developing follicles of laying hens. We have also shown that TGF-alpha binds to cell-surface receptors of the granulosa cells. The present study characterizes the nature of the EGF/TGF-alpha receptor. Immunoprecipitation of receptor proteins from cultured granulosa cells with an anti-EGF receptor antibody (12E) shows the expression of a 170-kDa receptor protein. The expression of the receptor protein decreases with follicular enlargement between the F3 and F1. Incubation of the cells with [125I]TGF-alpha followed by cross-linking with bis(sulphosuccinimidyl)suberate showed that TGF-alpha binds a similar (170 kDa) receptor protein immunoprecipitated with the 12E anti-EGF receptor antibody. The binding of TGF-alpha to granulosa cells caused receptor protein oligomerization, yielding the monomeric (170 kDa) and dimeric (340 kDa) protein forms. Oligomerization seemed to favour the formation of the dimeric rather than the monomeric form. Culturing granulosa cells with luteinizing hormone or follicle-stimulating hormone increased the expression of both monomer and dimer forms of the receptor proteins compared with the control. Western blotting analysis with anti-phosphotyrosine antibody revealed that the lysates of TGF-alpha-stimulated cells express phosphotyrosine-containing receptor proteins of 170 kDa and 340 kDa. The results show that chicken granulosa cells express the 170-kDa EGF/TGF-alpha receptor protein, which dimerizes on binding to TGF-alpha, suggesting that the receptor protein may be involved in the signal transduction of TGF-alpha actions in the chicken granulosa cells.

Characterization of transforming growth factor-alpha receptors in the avian ovary: alterations in ligand binding to granulosa cells during follicular maturation

The presence of epidermal growth factor receptors (EGF-R) and the ligands epidermal growth factor/transforming growth factor-alpha (EGF/TGF alpha) have been reported in mammalian ovaries where they are implicated in folliculogenesis and steroidogenesis. Evidence is presented to show that authentic EGF/TGF alpha receptors are expressed by the avian granulosa cells. The TGF alpha receptors (TGF alpha-R) from chicken granulosa cells were characterized by specific binding of 125I-human TGF alpha. In this study, competition with human EGF, human TGF alpha, human IGF-I, human basic fibroblast growth factor (bFGF) and insulin for 125I-human TGF alpha binding demonstrated that the avian granulosa cell TGF alpha-R binds human EGF with 300-fold lower affinity than human TGF alpha. IGF-I, bFGF and insulin did not displace bound 125I-TGF alpha. Scatchard analysis showed that a single class of high-affinity binding sites is present on the granulosa cells (Kd 0.23 +/- 0.009 nM). However, the number of binding sites altered during follicular maturation with a significant decline in the most mature follicle. These results go some way to explaining the basis for the changing sensitivity of avian granulosa cells to EGF/TGF alpha stimulation as they mature. In addition, the gonadotrophins, LH and FSH, increased the number of receptors in cultured granulosa cells and may therefore partially influence folliculogenesis and steroidogenesis through this route.

Effects of insulin-like growth factor I and interactions with transforming growth factor alpha and LH on proliferation of chicken granulosa cells and production of progesterone in culture

The effects of insulin-like growth factor I (IGF-I), alone, and in combination with LH or transforming growth factor alpha (TGF-alpha), on replication and progesterone production by cultured avian granulosa cells obtained from the three largest (F1-F3) follicles were studied. IGF-I and TGF-alpha stimulated proliferation of granulosa cells in a dose-dependent manner, and responsiveness decreased as the cells matured. IGF-I stimulated progesterone production from granulosa cells of all the follicles with no change in ED50 value during follicular maturation; however, the maximum response was from cells derived from F1 follicles. IGF-I plus LH had an additive effect on progesterone production by cells from all follicles. In contrast, TGF-alpha inhibited basal and LH- and IGF-I-stimulated progesterone production. These data show that IGF-I and TGF-alpha may interact with each other during granulosa cell maturation, such that efficacy of IGF-I increases, while that of TGF-alpha decreases before ovulation. Furthermore, both growth factors interact with LH, either to enhance or inhibit progesterone production by granulosa cells. However, LH, IGF-I and TGF-alpha combine to stimulate proliferation of granulosa cells.

Immunohistochemical localization of epidermal growth factor receptors, epidermal-growth-factor-like and transforming-growth-factor-alpha-like peptides in chicken ovarian follicles

The purpose of this study was to determine the presence of epidermal growth factor receptor and its potential ligands epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) in the tissues of the maturing follicles in the ovary of laying ISA-Brown hens using peptide-specific immunohistochemical methods. Cryostat sections, 6-8 microns thick, were made from fresh-frozen tissues of F1-F4 (largest to fourth largest) and large white follicles and they were immunostained for epidermal growth factor receptor, epidermal growth factor or transforming growth factor alpha using specific polyclonal antibodies. The EGF receptor and both ligands were detected in the granulosa, theca interna and theca externa layers of the follicles. The EGF receptor was localized both in the plasma membrane and cytoplasm of all cell types. EGF was predominantly cytosolic, whereas TGF-alpha was found in the plasma membranes and perinuclear areas of all cell types. The concentration of the receptor and both ligands decreased with follicular maturation. This observation is consistent with our previous observation that the response to EGF and TGF-alpha decreases as follicles mature, and thus provides further evidence that the receptor or the ligands may have a regulatory role in avian ovarian function.

Chicken granulosa cell proliferation and progesterone production in culture: effects of EGF and theca secretions

Paracrine/autocrine factors like epidermal growth factor (EGF) and transforming growth factor (TGF alpha) produced in the mammalian ovary modulate ovarian functions such as cell proliferation, differentiation, and steroidogenesis. To study similar activities in the avian ovary, we have developed a culture system for chicken granulosa cells using either serum containing or serum-free media. In the defined medium, granulosa cells for the F1, F2, and F3 follicles of the chicken ovary proliferated as indicated by enhanced levels of DNA, synthesised progesterone in similar amounts to those observed in acute experiments, and responded to luteinizing hormone (LH) during and after the culture period. The morphology of the cells and profile of growth in both media (although better in serum than in serum-free medium) are similar to those reported for mammalian cells. EGF stimulated granulosa cell proliferation over 72 hr in culture while inhibiting basal and LH-stimulated progesterone production; these effects were greatest in the less mature cells taken from the F3 follicles. Theca-conditioned medium (TCM) from chicken ovarian theca cell cultures mimicked the effects of EGF when cultured with granulosa cells. Taken together, these results suggest that EGF/TGF alpha-like peptides have a role in avian ovarian function. Moreover, the effects observed for TCM suggest that these peptides may be present in the theca layer with a paracrine function in the adjacent granulosa.

Regulation of cell proliferation and estrogen synthesis by ovine LH, IGF-I, and EGF in theca interstitial cells of the domestic hen cultured in defined media

There is relatively little information on the factors which regulate the proliferation and alterations in the steroidogenic capacity of avian theca cells during follicular maturation. The development of culture conditions for these cells to determine the effects of gonadotrophin (LH) and the growth factors epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on DNA synthesis and estrogen production is reported. Cultures were established in serum-supplemented (with fetal calf serum or chicken serum) or ITS+ (insulin, transferrin, and selenium plus additives) supplemented serum-free media. Cell replication occurred throughout the 72-hr culture period as indicated by a linear increase in the DNA content of the culture dishes. Aromatase activity of the cells as defined by conversion of androstenedione to estrogen was best maintained in serum-free medium while sera inhibited this activity. Ovine LH enhanced the aromatase activity of cultured cells from medium and small-sized follicles, while IGF-I and EGF inhibited both basal and LH-stimulated aromatase activity. LH, IGF-I, and EGF all stimulated cell proliferation as reflected by increased DNA. The responses of cells to these peptides varied with the size of the follicle, with the greatest effects on cells from F4/5.

Calcium-dependent stimulation of estrogen secretion by FSH from theca cells of the domestic hen (Gallus domesticus)

There is little information about the stimulation of estrogen secretion from theca cells of the domestic hen by follicle-stimulating hormone (FSH), and the mechanism of action of FSH through calcium has not been considered previously. The theca interna and externa cells from the third (F3) and fourth (F4) largest ovarian follicles of hens were separated, dispersed, and incubated in M199 with FSH (0.5 micrograms ml-1) or A23187 (0.1 or 1 microgram ml-1) with or without ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA) (2 mM) in calcium-replete or in calcium-free M199. Alternatively, androstenedione (10(-6) M) was added to the cells as aromatizable substrate, with or without FSH and/or EGTA. Estradiol and estrone secreted into the media during a 4-hr incubation period were measured by RIA. FSH stimulated estradiol and estrone secretion from all the cell preparations. The effect of FSH was abolished by the addition of EGTA or in calcium-free medium. A23187 stimulated estradiol and estrone secretion by the same extent as FSH, but did not do so in calcium-free medium. Androstenedione enhanced estradiol and estrone secretion, but estrogen secretion was further raised by the simultaneous addition of FSH. This action of FSH on aromatization was also abolished by EGTA. This evidence supports the hypothesis that calcium, possibly of extracellular origin, is an important mediator in the stimulation of aromatase systems in thecal cells of chickens.

Steroid secretion by ovarian cells of the Japanese quail (Coturnix coturnix japonica)

Mixed cell preparations (theca plus granulosa) prepared from the hierarchy of follicles of quails ovaries were incubated under defined conditions with or without the addition of ovine luteinizing hormone (oLH), ovine follicle stimulating hormone (oFSH), theophylline, cycloheximide, or dibutyryl cyclic adenine monophosphate (db cAMP); or in the presence of androstenedione or testosterone as aromatizable substrate. Steroids secreted into the medium during the 4-hr incubation period were assayed by radioimmunoassay. Cells from the largest follicles (F1) secreted predominantly progesterone, were stimulated by LH and db cAMP, and the response was potentiated by theophylline, but FSH had no stimulatory effect. The F1 cells showed increasing basal and LH-stimulated responses between 18 and 12 hr before the next expected oviposition. Cells from the smaller follicles (F3 and F4) secreted predominantly estrogens, and were stimulated by FSH but not by db cAMP and only to a small extent by theophylline. Addition of androstenedione (10(-7) M) or testosterone (10(-7) M) enhanced estrogen secretion, which was further raised by the simultaneous addition of FSH. These results confirm previous reports on the sites of steroid secretion within quail follicles and suggest that while the action of LH on the cells from F1 follicles may be mediated in part through the adenylate cyclase system, the action of FSH on the smaller follicles may be substantially independent of cAMP.