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

Feed intake alters immune cell functions and ovarian infiltration in broiler hens: implications for reproductive performance

Leukocytes are known to participate in ovarian activities in several species, but there is a surprising lack of information for the common chicken. Broiler hens consuming feed ad libitum (AL) exhibit a number of ovarian irregularities, but leukocyte functions are unstudied. In contrast to feed-restricted (R) hens, AL feeding for 7 wk significantly reduced egg production and clutch length while increasing pause length and atretic follicle numbers (P < 0.05). Granulosa cells from F1 follicles of AL hens contained less progesterone, and follicle walls were thicker with loose fibrous morphology and had less collagenase-3-like gelatinolytic activity but more IL-1beta (P < 0.05) production, suggestive of slower maturation in ovulatory process and inflamed necrosis. Interestingly, while highly infiltrated with immune cells, particularly heterophils, IL-1beta, MMP-22-like, and gelatinase A activities were reduced in AL hen peripheral heterophils and monocytes (P < 0.05); however, AL monocytes showed an increase in phagocytosis rate (P < 0.05). Generation of reactive oxygen intermediates was also suppressed in AL heterophils but increased in AL monocytes (P < 0.05). In contrast to leukocyte-free control, both AL and R heterophils and monocytes suppressed progesterone production and increased cell death in a dose-dependent manner when coincubated with granulosa cells at different ratios (P < 0.05). AL monocytes suppressed progesterone production more, but AL heterophils were less proapoptotic when compared to their R counterparts (P < 0.05). Alterations of cellular ceramide content (P < 0.05) corresponded to the discrepancy between heterophil and monocyte functionality. In conclusion, leukocyte dysfunction contributes to impaired ovarian activities of overfed broiler hens.

Preconception zinc deficiency disrupts postimplantation fetal and placental development in mice

Zinc is an essential nutrient for optimal fertility, but the effects of preconception zinc deficiency on postimplantation development are not known. Female mice were fed a control or a zinc-deficient diet (ZDD) for 4-5 days before ovulation (preconception). Embryonic and/or placental development were evaluated on Days 3.5, 6.5, 10.5, 12.5, and 16.5 of pregnancy. The findings show a decrease in embryo length (31%, Day 10.5; 13%, Day 12.5; 10%, Day 16.5) and weight (23%, Day 16.5) in embryos from mothers fed a ZDD preconception. Zinc deficiency also caused a high incidence of pregnancy loss (46%, Day 10.5; 34%, Day 12.5; 51%, Day 16.5) compared to control (2%, Day 10.5; 7%, Day 12.5; 9%, Day 16.5). ZDD embryos transferred to normal recipients were 38% smaller and implantation rate was only 10% compared to 40% for controls. Trophoblast cell differentiation and implantation on Day 6.5 of pregnancy were compromised by preconception zinc deficiency. On Day 12.5 of pregnancy, placenta weight and area of fetal placenta were decreased 37% and 31%, respectively, by preconception zinc deficiency. Consistent with a smaller fetal placenta, expression of key placental transcripts, including Ar, Esx1, Syna, Tfeb, Dlx3, and Gcm1 mRNA, but not Ctsq mRNA, were decreased 30%-70% in the ZDD group. Preconception zinc deficiency caused 41%-57% of embryos to exhibit delayed or aberrant neural tube development, as examined by light microscopy and magnetic resonance imaging. Collectively, the findings provide evidence for the importance of preconception zinc in promoting optimal fertility and oocyte developmental potential.

Leptin receptor signaling inhibits ovarian follicle development and egg laying in chicken hens

BACKGROUND

Nutrition intake during growth strongly influences ovarian follicle development and egg laying in chicken hens, yet the underlying endocrine regulatory mechanism is still poorly understood. The relevant research progress is hindered by difficulties in detection of leptin gene and its expression in the chicken. However, a functional leptin receptor (LEPR) is present in the chicken which has been implicated to play a regulatory role in ovarian follicle development and egg laying. The present study targeted LEPR by immunizing against its extracellular domain (ECD), and examined the resultant ovarian follicle development and egg-laying rate in chicken hens.

METHODS

Hens that have been immunized four times with chicken LEPR ECD were assessed for their egg laying rate and feed intake, numbers of ovarian follicles, gene expression profiles, serum lipid parameters, as well as STAT3 signaling pathway.

RESULTS

Administrations of cLEPR ECD antigen resulted in marked reductions in laying rate that over time eventually recovered to the levels exhibited by the Control hens. Together with the decrease in egg laying rate, cLEPR-immunized hens also exhibited significant reductions in feed intake, plasma concentrations of glucose, triglyceride, high-density lipoprotein, and low-density lipoprotein. Parallelled by reductions in feed intake, mRNA gene expression levels of AgRP, orexin, and NPY were down regulated, but of POMC, MC4R and lepR up-regulated in Immunized hen hypothalamus. cLEPR-immunization also promoted expressions of apoptotic genes such as caspase3 in theca and fas in granulosa layer, but severely depressed IGF-I expression in both theca and granulosa layers.

CONCLUSIONS

Immunization against cLEPR ECD in egg-laying hens generated antibodies that mimic leptin bioactivity by enhancing leptin receptor transduction. This up-regulated apoptotic gene expression in ovarian follicles, negatively regulated the expression of genes that promote follicular development and hormone secretion, leading to follicle atresia and interruption of egg laying. The inhibition of progesterone secretion due to failure of follicle development also lowered feed intake. These results also demonstrate that immunization against cLEPR ECD may be utilized as a tool for studying bio-functions of cLEPR.

Influence of substituting dietary soybean for air-classified sunflower (Helianthus annuus L.) meal on egg production and steroid hormones in early-phase laying hens

Soybean meal (SBM) is the most widely and expensive protein source used in the formulation of poultry diets; however, when the price of SBM increases, poultry nutritionists seek alternative sources that are more economical in formulating least-cost rations. This research aimed to evaluate the effects of dietary air-classified sunflower meal (SFM) on some productive parameters and plasma steroid hormones in laying hens. In this trial, 20-week-old laying hens (ISA Brown strain) in the early phase of production were randomly assigned to two groups and fed wheat middlings-based diets containing soybean (135 g/kg; 48% CP) or air-classified SFM (160 g/kg; 41% CP) as the main protein source. Laying performance, egg size and feed conversion ratio were evaluated for 10 week. Plasma steroid hormones (progesterone and oestradiol) in the hens were quantified weekly. Substituting SBM with air-classified SFM did not change (p > 0.05) the hens' growth performance, whereas feed consumption and efficiency were positively influenced (p < 0.05) by SFM treatment. Egg production rate was improved in hens fed the SFM diet (p < 0.05), as well as the percentage of medium-size eggs that was higher for SFM treatment (p < 0.05). Steroid hormones levels were affected by dietary treatment (p < 0.01). From our findings, it could be effective to include air-classified SFM in early-phase laying hen diets as an alternative protein source substituting SBM, without negative influence on productive performance and egg traits, reducing also the production costs.

Changes in some blood parameters and production performance of old laying hens due to growth hormone and testosterone injection

The experiment was designed to study the changes in some blood parameters and production performance of old laying hens after injection of different doses of growth hormone (GH) and testosterone (Ts). A total of 160 old laying hens (HyLine W-36) at 73 weeks of age were weighed individually and randomly allocated to four treatments with four replicates and 10 birds in each replicate in a completely randomized design. Growth hormone and Ts hormones were injected subcutaneously. Treatment groups were as follows: treatment 1: injection of 100 μl distiled water (control group), treatment 2: injection of 500 μg Ts/kg live-weight + 50 μgGH/kg live-weight, treatment 3: injection of 500 μgTs/kg live-weight + 100 μgGH/kg live-weight and treatment 4: injection of 500 μgTs/kg live-weight + 150 μgGH/kg live-weight. Plasma levels of oestradiol, T4 , LDL, HDL and cholesterol significantly increased in treatment 3 in relation to the control group. All injected hens showed significantly higher levels of glucose in relation to control group. The results showed the positive effects of GH and Ts administration on production performance and blood parameters which are associated with egg production potentiality and in turn may improve reproductivity (egg production) in old laying hens. The positive results of the study may be useful in animal selection and breeding programmes.

Effect of estradiol-17β on follicle-stimulating hormone secretion and egg-laying performance of Japanese quail

The aim of this study was to measure the effect of estradiol-17β (E2) injection on follicle-stimulating hormone (FSH) secretion and egg-laying performance of Japanese quail. Female Japanese quail were housed in cages and fed ad libitum. After a 7-day adaptation period, the birds were randomly assigned to three groups, that is, one control group and two test groups. The birds were weighed, before every injection. The control group was subcutaneously injected with 0.2 ml sesame oil-ethanol mixture, whereas test groups were injected, twice in a week, with 0.2 ml sesame oil-ethanol mixture containing 0.1 or 0.2 mg E2 along the study. One day after the first injection, egg number, egg weight, eggshell strength and food conception were daily recorded. On the last day of the experiment, the birds were injected and 3 h later seven birds from each group were randomly selected for bleeding. Blood samples (2 ml/bird) were collected from the jugular vein for the measurements of serum concentrations of E2, FSH, calcium (Ca) and phosphorus (P). E2 injection did not cause any significant changes in serum FSH concentrations, daily egg laid/bird, food conception/bird, serum concentrations of the Ca and the P. Egg weight was significantly increased in the 0.1 mg E2-injected group as compared with the control and 0.2 mg E2-injected groups. Eggshell strength in the 0.2 mg E2-injected group was significantly high as compared with the control, whereas the difference between the 0.1 mg E2- and 0.2 mg E2-injected groups was not statistically important. These results show that serum FSH concentration was not increased even when slightly suppressed by subcutaneous injection of 0.1 or 0.2 mg E2. Different doses of E2 have different functions. The increase in BWs in the 0.1 mg E2-injected group was a result of the dose effect, which probably increased growth hormone secretion from the pituitary or IGF-1 synthesis from the liver or both. The dose, 0.2 mg E2, was ineffective in increasing the BW, but it significantly increased eggshell strength probably via the increase in Ca and P utilizations.

The GTPase activating Rap/RanGAP domain-like 1 gene is associated with chicken reproductive traits

Background

Abundant evidence indicates that chicken reproduction is strictly regulated by the hypothalamic-pituitary-gonad (HPG) axis, and the genes included in the HPG axis have been studied extensively. However, the question remains as to whether any other genes outside of the HPG system are involved in regulating chicken reproduction. The present study was aimed to identify, on a genome-wide level, novel genes associated with chicken reproductive traits.

Methodology/Principal Finding

Suppressive subtractive hybridization (SSH), genome-wide association study (GWAS), and gene-centric GWAS were used to identify novel genes underlying chicken reproduction. Single marker-trait association analysis with a large population and allelic frequency spectrum analysis were used to confirm the effects of candidate genes. Using two full-sib Ningdu Sanhuang (NDH) chickens, GARNL1 was identified as a candidate gene involved in chicken broodiness by SSH analysis. Its expression levels in the hypothalamus and pituitary were significantly higher in brooding chickens than in non-brooding chickens. GWAS analysis with a NDH two tail sample showed that 2802 SNPs were significantly associated with egg number at 300 d of age (EN300). Among the 2802 SNPs, 2 SNPs composed a block overlapping the GARNL1 gene. The gene-centric GWAS analysis with another two tail sample of NDH showed that GARNL1 was strongly associated with EN300 and age at first egg (AFE). Single marker-trait association analysis in 1301 female NDH chickens confirmed that variation in this gene was related to EN300 and AFE. The allelic frequency spectrum of the SNP rs15700989 among 5 different populations supported the above associations. Western blotting, RT-PCR, and qPCR were used to analyze alternative splicing of the GARNL1 gene. RT-PCR detected 5 transcripts and revealed that the transcript, which has a 141 bp insertion, was expressed in a tissue-specific manner.

Conclusions/Significance

Our findings demonstrate that the GARNL1 gene contributes to chicken reproductive traits.

Effect of probiotic Propionibacterium jensenii 702 supplementation on layer chicken performance

The effects of the probiotic, Propionibacterium jensenii 702 (PJ 702), supplementation on egg productivity, egg shell thickness, fatty acid profile of eggs, and body weight in early layer hens were investigated. Twenty eight twenty-week-old starter pullets were evenly divided into a treatment and a control group for an eight week experiment. Each bird in the treatment group received 107 cfu PJ 702 daily in a total volume of 1 ml by oral administration. No adverse effect was observed due to administration of PJ 702, and successful gastrointestinal transit in the bird was demonstrated by recovery of PJ 702 from faeces of the treatment group. Layer production was significantly improved by the supplementation of PJ 702. Total egg weight in the treatment group was significantly higher than the control (P<0.001). Average egg weight for the treatment group was 55.26 g, 4.2% higher than the control which averaged 53.02 g. Moreover, the fatty acid profile was significantly altered by the supplementation of PJ 702. Myristic acid (P<0.001), palmitoleic acid (P=0.001) and all-cis-11,14-eicosadienoic acid (P=0.02) were significantly lower in the treatment group compared to the control group. No difference in egg shell thickness was observed between the treatment and control group (P=0.23). In conclusion, the application of novel probiotic PJ 702 in the early layer hen is safe and effective to promote production and the quality of products in layer husbandry.

Genetic effects of polymorphisms in candidate genes and the QTL region on chicken age at first egg

Background

The age at first egg (AFE), an important indicator for sexual maturation in female chickens, is controlled by polygenes. Based on our knowledge of reproductive physiology, 6 genes including gonadotrophin releasing hormone-I (GnRH-I), neuropeptide Y (NPY), dopamine D2 receptor (DRD2), vasoactive intestinal polypeptide (VIP), VIP receptor-1 (VIPR-1), and prolactin (PRL), were selected as candidates for influencing AFE. Additionally, the region between ADL0201 and MCW0241 of chromosome Z was chosen as the candidate QTL region according to some QTL databases. The objective of the present study was to investigate the effects of mutations in candidate genes and the QTL region on chicken AFE.

Results

Marker-trait association analysis of 8 mutations in those 6 genes in a Chinese native population found a highly significant association (P < 0.01) between G840327C of the GnRH-I gene with AFE, and it remained significant even with Bonferroni correction. Based on the results of the 2-tailed χ² test, mutations T32742394C, T32742468C, G32742603A, and C33379782T in the candidate QTL region of chromosome Z were selected for marker-trait association analysis. The haplotypes of T32742394C and T32742468C were significantly associated (P < 0.05) with AFE. Bioinformatics analysis indicated that T32742394C and T32742468C were located in the intron region of the SH3-domain GRB2-like 2 (SH3GL2) gene, which appeared to be associated in the endocytosis and development of the oocyte.

Conclusion

This study found that G840327C of the GnRH-I gene and the haplotypes of T32742394C-T32742468C of the SH3GL2 gene were associated with the chicken AFE.

A twice-a-day feeding regimen optimizes performance in broiler breeder hens

To evaluate the effects of different methods of feed allocation on performance, plasma hormone concentration, and ovarian morphology, an experiment was conducted using 32 Cobb 500 broiler breeder hens. The experiment was started at 27 wk and lasted to 39 wk of age. Feeding regimens included: i) hens with an ad libitum feeding program, ii) hens that received their restricted feed once a day, iii) hens that received their restricted feed twice a day, and iv) hens that received their restricted feed 3 times a day. Each hen was assumed as an experimental unit and treatments were replicated 8 times. Daily egg production, BW, and egg and yolk weights were measured. Two blood samples were taken 3 and 6 h after the first feed allocation every 2 wk. Plasma samples were assayed for glucose, triacylglycerol (TAG), cholesterol, as well as leptin-like concentration, glucagon, triiodothyronine, thyroxine, progesterone, estradiol, and testosterone. Liver, abdominal fat pad, and ovary were collected at necropsy. Ovaries were weighed and follicles were characterized as large yellow follicles, small yellow follicles, and large white follicles. Results showed inferior egg production in ad libitum-fed birds along with high levels of plasma glucose, TAG, cholesterol, leptin-like concentration, and testosterone. Twice-a-day-fed birds produced more egg in the entire production period than once-a-day-fed birds. Better performance of twice-a-day-fed hens was associated with lower plasma glucose, TAG, and leptin-like concentration, whereas their estradiol and glucagon were higher than once-a-day-fed hens. Results obtained in our study suggest that allocation of restricted feed 2 times a day may alleviate or delay lipotoxicity development and improve reproductive performance in broiler breeder hens.

Intra-ovarian growth factors regulating ovarian function in avian species: a review

There is now overwhelming evidence that the avian ovary is a site of production and action of several growth factors that have also been implicated in the functioning of the mammalian ovary. Several members of the Insulin-like growth factor family (IGF), the Epidermal growth factor family (EGF), the Transforming growth factor-beta family (TGF-beta), Fibroblast growth factors (FGF), the Tumour necrosis factor-alpha (TNF-alpha), and others, have been identified either in the granulosa and/or theca compartments of ovarian follicles and in the embryonic and juvenile ovary. Some have been specifically localized to the germinal disc area containing the oocyte. The mRNAs and proteins of the growth factors, receptor proteins and binding proteins of some of the members of each group have been reported in the chicken, turkey, quail and duck. The intra-ovarian roles reported for the different growth factors include regulation of cell proliferation, steroidogenesis, follicle selection, modulation of gonadotrophin action, control of ovulation rate, cell differentiation, production of growth factors, etc. The aim of this paper is to provide a review of the current knowledge of avian ovarian growth factors and their biological activity in the ovary. The review covers the detection of the growth factor proteins, the receptor proteins, binding proteins, their spatial and temporal distribution in embryonic, juvenile and adult ovaries and their regulation. The paper also discusses their roles in each follicular compartment during follicular development. Greater emphasis is given to the major growth factors that have been studied to greater detail and others are discussed very briefly.

Changes in progesterone receptor isoforms content in the brain of immature, mature and aged male and female chickens

Progesterone participates in the regulation of several reproductive functions in birds through its interaction with intracellular progesterone receptors (PR) which exhibit two isoforms (PR-A and PR-B) with different function and regulation. We determined the content of PR isoforms in several brain regions of immature (1.5 months-old), mature (12 months-old) and aged (48 months-old) male and female chickens by Western blot analysis. PR isoforms protein content changed in tissue-and age-specific manner in the brain of both male and female chickens. In female animals PR-B content was higher in the hypothalamus of mature animals than in other ages while PR-A content increased in the cerebellum of aged animals. No significant changes were observed in PR isoforms content in the cortex and the tectum of female animals. In contrast, in male animals PR-B content was higher in the hypothalamus of aged animals. The cerebellum, tectum and cortex of male animals did not present significant changes in PR isoforms content. In all studied regions of female animals PR-B was the predominant isoform, whereas, in males a significant predominance of PR-B was only found in the hypothalamus of aged animals. These results demonstrate that PR isoforms content presents a sexual dimorphism in the brain of chickens that changes in tissue- and age-specific manner, and suggest that these variations contribute to the regulation of progesterone actions in brain throughout the lifespan of male and female chickens.