Egg Production In Birds Research Articles

The hypothalamic transcriptome reveals the importance of visual perception on the egg production of Wanxi white geese.

Egg performance significantly impacts the development of the local goose industry. The hypothalamus plays an essential role in the egg production of birds. However, few potential candidate genes and biological functions related to egg production in geese have been identified in hypothalamus tissue. In this study, 115 geese were raised and observed for 5 months during the laying period. To understand the regulation mechanism of egg production, the hypothalamus transcriptome profiles of these geese were sequenced using RNA-seq. The hypothalamus samples of four high egg production (HEP) and four low egg production (LEP) geese were selected and collected, respectively. A total of 14,679 genes were identified in the samples. After multiple bioinformatics analyses, Gene Ontology (GO) annotations indicated that genes related to egg production were mainly enriched in biological processes of "response to light stimulus," "sensory system development," and "visual perception." Six potential candidate genes (PDE6C, RHO, MFRP, F2, APOB, and IL6) based on their corresponding GO terms and interaction networks were identified. These identified candidate genes can be used as selection markers to improve the egg production of Wanxi white geese. Our study highlights how visual perception may affect the regulation of geese egg production.

Large-brained birds lay smaller but heavier clutches

The brain is among the most energetically costly organs in vertebrates, and thus trade-offs have been hypothesized to exert constraints on brain size evolution. The energy trade-off hypothesis (ETH) predicts that reducing the energy consumption of reproduction or other costly tissues should compensate for the cost of a large brain. Egg production in birds requires a large proportion of the total energy budget, and a clutch mass in some bird species can outweigh the body mass of the female. To date, this hypothesis has mainly been tested in mammals and ectothermic animals such as anurans and fishes. We collated data on adult brain size, body mass and egg-production traits such as clutch size, egg mass and annual broods from published studies, and conducted a phylogenetic comparative test of the interplay between egg-production investment and brain size evolution across bird species. After controlling for phylogenetic relationships and body size, we find a negative correlation between brain size and clutch size across 1395 species, which favored ETH. However, when egg mass was integrated in models, positive associations were detected between brain size and mass of eggs (via egg mass, clutch mass and annual total egg mass). Our results suggest that brain size trades off against egg-production only via certain aspects (e.g., clutch size). By contrast, a positive relationship between brain size and total egg reproduction (e.g., clutch mass and annual total egg mass) implied increased total energy budget outweighing energy allocation across bird species. Our study shows that there is no general energy trade-off between brain size and egg-reproduction investment, and suggests that brain size evolution follows mixed strategies across bird species.

A Possible Mechanism for Double-Yolked Eggs in the Early Stage of Egg-Laying in Zhedong White Goose-Function of IGF1 and LHR Signaling.

The cause of double-yolk (DY) egg production in birds is unclear, but it is related to body weight and adiposity. We explored the causes of the high proportion (up to 26%) of DY eggs in the first clutch of Zhedong white geese. We recorded the egg production of Zhedong white geese during the first egg-laying cycle and counted the proportion of DY eggs. We found that 30% of geese had 3 sets of double or triple follicles of the same diameter in the abdomen, which was close to the DY egg rate. In addition, the mRNA expression levels of the steroidogenic acute regulatory protein (StAR) and luteinizing hormone receptor (LHR) genes in granulosa cells were similar within the same set of follicles. Furthermore, the IGF1 concentration in geese that had at least 3 sets of follicles of the same diameter was significantly higher than that in birds with 0-1 set of follicles of the same diameter. Thus, we proposed that, in the first egg-laying stage of geese, high plasma concentrations of IGF1 stimulate the development of pre-hierarchal follicles and cause more than one follicle to be selected at the same time, mature at the same rate under the same gonadotrophin milieu, and ovulate at the same time to produce DY eggs.

Location of Chickens Within Rearing Floors of Laying Hens Closed Halls and Its Effect of Productive, Physiological and Qualitative Eggs Characteristics

This study was conducted in (Samarra Poultry Commercial Project), located in Samarra, 130 km north Baghdad, in a closed hall of Turkish origin, containing 53,000 Lumen Brown laying hens, 34 weeks of age, raised in cages, each of which accommodates 10 birds and distributed into five lines, each is mixed with five floors. Very symmetrical, including ten. In order to know the effect of the location of chickens within floors. Breeding in closed halls lines on productive performance, quality traits of eggs and some traits blood physiology: The results showed the following. Significantly decreased egg production in birds bred within the first (ground) floor, and this was accompanied by a significant decrease in egg production. Deterioration in the efficiency of feed conversion.. The location of the chickens within the breeding floors had no significant effect on most of the qualitative characteristics of eggs. The chickens raised on the third floor showed the best parameters of red blood cells, with a stabilization of the case. There were no significant differences in the numbers of white blood cells.

Hypothalamic and ovarian transcriptome profiling reveals potential candidate genes in low and high egg production of white Muscovy ducks (Cairina moschata)

In China, the low egg production rate is a major challenge to Muscovy duck farmers. Hypothalamus and ovary play essential role in egg production of birds. However, there are little or no reports from these tissues to identify potential candidate genes responsible for egg production in White Muscovy ducks. A total of 1,537 laying ducks were raised; the egg production traits which include age at first egg (days), number of eggs at 300 d, and number of eggs at 59 wk were recorded. Moreover, 4 lowest (LP) and 4 highest producing (HP) were selected at 59 wk of age, respectively. To understand the mechanism of egg laying regulation, we sequenced the hypothalamus and ovary transcriptome profiles in LP and HP using RNA-Seq. The results showed that the number of eggs at 300 d and number of eggs at 59 wk in the HP were significantly more (P < 0.001) than the LP ducks. In total, 106.98G clean bases were generated from 16 libraries with an average of 6.68G clean bases for each library. Further analysis showed 569 and 2,259 differentially expressed genes (DEGs) were identified in the hypothalamus and ovary between LP and HP, respectively. The KEGG pathway enrichment analysis revealed 114 and 139 pathways in the hypothalamus and ovary, respectively which includes Calcium signaling pathway, ECM-receptor interaction, Focal adhesion, MAPK signaling pathway, Apoptosis and Apelin signaling pathways that are involved in egg production. Based on the GO terms and KEGG pathways results, 10 potential candidate genes (P2RX1, LPAR2, ADORA1, FN1, AKT3, ADCY5, ADCY8, MAP3K8, PXN, and PTTG1) were identified to be responsible for egg production. Further, protein-protein interaction was analyzed to show the relationship between these candidate genes. Therefore, this study provides useful information on transcriptome of hypothalamus and ovary of LP and HP Muscovy ducks.

Применение кормовой добавки «Абиотоник» в птицеводстве

This paper presents a study of the effect of the feed additive «Abiotonic» on the indicators of egg and meat productivity when applied to laying hens. It was found that with the additional introduction of this additive into the standard diet of poultry, the content of nonessential amino acids in their meat is 10% higher compared to the same parameters in the meat of chickens of the control group, the content of partially nonessential amino acids is by 8,5%, and of irreplaceable amino acids is by 6,7%. In addition, in the meat of laying hens, which used the feed additive «Abiotonic», the content of selenium (Se) is 29,4% higher than in the meat of birds of the control group, and iron (Fe) – by 20%. The average daily gain in live weight of the birds in the experimental group was 3,6 g more than in the control hens. Microbiological research made it possible to establish that poultry meat, regardless of the introduction of the feed additive «Abiotonik», meets the established requirements and is safe for human consumption. «Abiotonic», in addition, significantly improves the egg production of birds. It was found that the weight of eggs with the introduction of this feed additive in the diet in addition to the compound feed increased by an average of 1,2 g, and the egg production increased by 23 eggs in 7 days.

Heat stress and poultry production: impact and amelioration.

Globally, the poultry industry is gaining significant importance among the agricultural and its allied sectors. However, heat stress was found to negatively affect the poultry production particularly in the tropical regions. This review is therefore an attempt to generate information pertaining to the impacts of heat stress on poultry production and its amelioration. Heat stress reduces the growth, reproductive performance, and egg production in poultry birds. The reduction in productive potential of poultry birds on exposure to heat stress may be attributed to the deviation of energy resources from production to adaptation pathway. There are different approaches pertaining to relieving the adverse impacts of heat stress on poultry production. These approaches can be broadly categorized under genetic, management, and nutritional strategies. These approaches may reduce the negative effects of heat stress and enhance the productive performance of poultry birds. The management strategies include appropriate shelter design, providing shade, using sprinklers, implementing cooling devices, and using fans and ventilation systems. The recommended floor space for mature birds weighing 1.7 kg is 0.06 m2/bird while it is 0.13 m2/bird for the birds weighing 3.5 kg with 27.8 kg/m2 bird density in either case. The nutritional interventions comprise ration balancing and providing essential micronutrients to improve the productive and reproductive performance in poultry birds. Fat, antioxidants, yeast, and electrolyte supplementations are some of the most commonly used nutritional strategies to ensure optimum production in the poultry industry. Furthermore, providing adequate water supply and disease surveillance measures may help to ensure optimum meat and egg production in the birds. The advanced biotechnological tools may aid to identify suitable genetic markers in poultry birds which might help in developing new strains of higher thermo-tolerance by designing suitable breeding program involving marker-assisted selection. These strategies may help to optimize and sustain poultry production in the changing climate scenario.

Methionine supplementation improves reproductive performance, antioxidant status, immunity and maternal antibody transmission in breeder Japanese quail under heat stress conditions.

This study was conducted to determine the effects of methionine (Met) supplementation on productive and reproductive performance, immune response and antioxidant status in breeder quails reared under heat stress (HS). A total of 125 breeder quails were divided into five groups. One group was kept in an environmentally controlled room at 22 C and considered as thermoneutral, and four groups were kept at 34 C and fed a basal diet (heat stressed) or a basal diet with Met concentrations 1.15, 1.30 and 1.45 times the quail requirements per NRC (1994) recommendations. HS decreased egg production in birds fed the basal diet (). Higher feed intake (), egg production (), improved feed efficiency () and Haugh unit and hatchability variables () occurred in Met supplemented groups. Birds receiving Met under HS had higher maternal serum IgG, egg yolk IgY and offspring serum IgG (mg mL). Quails receiving the Met supplementation diets exhibited higher () plasma levels and liver activity of superoxide dismutase, catalase and glutathione peroxidase as well as lower () plasma and liver levels of malondialdehyde compared to the HS group fed the basal diet. All breeder quails receiving the Met supplement had lower () heterophil and ratios as well as higher () lymphocytes than quails fed the basal diet under the same stress conditions. Our results suggest that dietary supplementation with Met could improve the performance, immunity and antioxidant status of quails by reducing the negative effects of HS.

Economics of egg production in birds fed on diets containing different energy and protein levels with and without fish meal

Economics of egg production in birds fed on diets containing different energy and protein levels with and without fish meal

Effects of mannan-oligosaccharides-supplemented diets on production performance of four close-bred flocks of Japanese quail breeders

The present study was conducted to find out the dietary effects of mannan-oligosaccharides (MOS) supplemented diets on the production performance of four close-bred flocks (CBFs) of Japanese quail ( Coturnix coturnix japonica ) breeders. A total of 960 twelve-week-old birds of four CBFs were randomly divided into four groups (n = 240) with 12 replicates (n = 20). Birds were fed a corn-based basal diet or the same diet supplemented with 0.25%, 0.50%, and 1.0% MOS for 15 weeks. The authors analysed the data by two-way ANOVA techniques using SAS (Statistical Analysis System). Birds fed MOS-supplemented diets had significantly higher body and egg weight, egg mass, and egg number than the control group. Similarly, the feed conversion ratio (FCR)/dozen eggs, FCR/kg egg mass, and mortality were significantly lower in MOS supplemented groups. However, no significant effect of MOS supplementation was recorded on feed intake and egg production of birds. None of the parameters differed significantly among CBFs. The results showed that feeding MOS as a replacement for antibiotic growth factor may positively influence the production performance and health of Japanese quail breeders. Keywords: Body weight, egg weight, egg mass, feed conversion ratio, mortality

Different wavelengths of light on GnRH mRNA, LH, steroid hormones and egg lay in the ageing hens (Gallus gallus domesticus).

The aim of this study was to investigate the effects of red spectrum of light (650nm, treated n=12) and normal spectrum of light (450nm control=12) on circulating concentrations of luteinizing hormone (LH), progesterone (P4), estradiol (E2β), GnRH mRNA, pause days and egg production in birds later in the reproductive period from 92-102weeks of age. Twenty-four White Leghorn birds of same age group were divided into two groups of 12 in each as control and treated. Birds in the control group were exposed to normal spectrum of light (450nm of length) and birds in the treated group were exposed to red spectrum of light (650nm, treated n=12). Egg production and inter sequence pauses were recorded daily from both the groups. Plasma LH, E2β and P4 concentrations were estimated in blood samples collected at weekly intervals. At 97th weeks of age, blood samples from treated and control birds were obtained every 3 h for 36 h to study the surges of LH. It was found that plasma GnRH was higher (p &lt; 0. 01) in treated birds with high concentrations of LH, its 3 h LH surges, E2β and P4 in plasma. Higher egg production, less pause days in treated birds may be the result of high GnRH associated with positively correlated responses of high concentrations of LH (with regular interval and duration of LH surges), E2β and P4 concentration required for completion of egg formation and oviposition. In conclusion, red spectrum of light enhanced GnRH mRNA (p &lt; 0. 01), increased (p &lt; 0. 01) steroid hormones and LH surges, for egg formation and oviposition and enabled the birds to lay more eggs even later in the productive period with the available resources under normal husbandry practices.

In-feed supplementation of trans-cinnamaldehyde reduces layer-chicken egg-borne transmission of Salmonella enterica serovar enteritidis.

Salmonella enterica serovar Enteritidis is a major foodborne pathogen in the United States, causing gastroenteritis in humans, primarily through consumption of contaminated eggs. Chickens are the reservoir host of S. Enteritidis. In layer hens, S. Enteritidis colonizes the intestine and migrates to various organs, including the oviduct, leading to egg contamination. This study investigated the efficacy of in-feed supplementation with trans-cinnamaldehyde (TC), a generally recognized as safe (GRAS) plant compound obtained from cinnamon, in reducing S. Enteritidis cecal colonization and systemic spread in layers. Additionally, the effect of TC on S. Enteritidis virulence factors critical for macrophage survival and oviduct colonization was investigated in vitro. The consumer acceptability of eggs was also determined by a triangle test. Supplementation of TC in feed for 66 days at 1 or 1.5% (vol/wt) for 40- or 25-week-old layer chickens decreased the amounts of S. Enteritidis on eggshell and in yolk (P<0.001). Additionally, S. Enteritidis persistence in the cecum, liver, and oviduct in TC-supplemented birds was decreased compared to that in controls (P<0.001). No significant differences in feed intake, body weight, or egg production in birds or in consumer acceptability of eggs were observed (P>0.05). In vitro cell culture assays revealed that TC reduced S. Enteritidis adhesion to and invasion of primary chicken oviduct epithelial cells and reduced S. Enteritidis survival in chicken macrophages (P<0.001). Follow-up gene expression analysis using real-time quantitative PCR (qPCR) showed that TC downregulated the expression of S. Enteritidis virulence genes critical for chicken oviduct colonization (P<0.001). The results suggest that TC may potentially be used as a feed additive to reduce egg-borne transmission of S. Enteritidis.

Single nucleotide polymorphism of prolactin gene exon two in ducks of Pekin, Mojosari and Pekin Mojosari crossbred

Prolactin gene plays crucial role in the reproduction and egg production of birds. The objectives of this study were to characterize single nucleotide polymorphism in partial intron and coding region of duck prolactin gene. Blood samples were collected from 168 ducks consisted of 19 Pekin, 36 Mojosari, and 113 of their crossbreds collected from Indonesian Research Institute for Animal Production (IRIAP). Primer pairs for the coding regions in prolactin gene were self designed based on the duck genomic sequence database (GeneBank: AB158611.1). PCR products based on DNA of prolactin gene exon two was amplified approximately 400 bp. There is one base insertion of Adenin at the position of 2001 bp intron two region of duck prolactin. Homology test based on BLAST method indicated 99% identity with duck refference (Code Access GeneBank: AB158611.1). Adenin composition in all of duck samples was higher than refference. Triplet hydrogen bonds between Guanine and Cytosin pairs was higher than those at duplet hydrogen bonds between Adenine and Thymine. All duck samples were homozigous and monomorphyc.

Zinc Oxide as an Effective Mineral for Induced Moulting: Effects on Post Moult Performance of Laying Hens in the Humid Tropics

The aim of this study was to evaluate the ability of using zinc oxide salts to induce moulting, and their effects on post moult performance and organ characteristics of laying hens. Two hundred (75 weeks of age) Isa Brown hens were randomly assigned to five Treatments (T) groups of 40 hens, each namely; T 0-non-moulted hens and T1, T2, T3, T 4 , representing moulted hens fed, respectively, 0.5%, 1.0%, 1.5% and 2.0% Zinc Oxide (ZnO) supplementation per kg diet for 14 days. Organ evaluations of the hens were carried out 7 days post moult. Body weight loss and decline in feed intake of the birds were higher (P<0.01) for moulted hens. Cessation of egg production occurred earlier (P<0.05) in the same groups of birds. During post moult, the moulted hens exhibited greater (P<0.01) percentage body weight gain, when compared with the non-moulted hens. Feed intake and hen-day egg production of birds on 1.0%, 1.5% and 2.0% ZnO supplementation was higher (P<0.01), than those of other treatments. Feed conversion ratio was better (P<0.05) for the same groups of birds. Moulting with ZnO treatment influence highly (P<0.01) the number of days to resumption of egg production, with hens on 2.0% ZnO resuming egg production much later than hens on 0.5%, 1.0%, and 1.5% ZnO treatments. The ovary, liver and kidney of the hens were affected (P<0.05) by the dietary ZnO contents. A greenish coloration of the liver was observed in hens fed 1.5% and 2% ZnO supplementation. These results demonstrate that in order to achieve good post moult performance of laying hens in the humid tropics, farmers should practice the use of 1% ZnO inclusion per kg diet, as an effective method to achieve induced moulting.

Effects of Lipid Extraction on Stable Isotope Ratios in Avian Egg Yolk: Is Arithmetic Correction a Reliable Alternative?

ABSTRACT. Many studies of nutrient allocation to egg production in birds use stable isotope ratios of egg yolk to identify the origin of nutrients. Dry egg yolk contains >50% lipids, which are known to be depleted in 13C. Currently, researchers remove lipids from egg yolk using a chemical lipid-extraction procedure before analyzing the isotopic composition of protein in egg yolk. We examined the effects of chemical lipid extraction on δ13C, δ15N, and δ34S of avian egg yolk and explored the utility of an arithmetic lipid correction model to adjust whole yolk δ13C for lipid content. We analyzed the dried yolk of 15 captive Spectacled Eider (Somateria fischeri) and 20 wild King Eider (S. spectabilis) eggs, both as whole yolk and after lipid extraction with a 2:1 chloroform:methanol solution. We found that chemical lipid extraction leads to an increase of (mean ± SD) 3.3 ± 1.1‰ in δ13C, 1.1 ± 0.5‰ in δ15N, and 2.3 ± 1.1‰ in δ34S. Arithmetic lipid correction provided accurate values for lipid-extracted δ13C in...

Female Zebra Finches (Taeniopygia guttata) Are Chronically but Not Cumulatively “Anemic” during Repeated Egg Laying in Response to Experimental Nest Predation

Recently it has been recognized that reproduction itself, or the regulatory processes controlling reproduction, might contribute to physiological costs of reproduction. Reproductive anemia, a decrease in hematocrit and hemoglobin concentration, might provide one such mechanism underlying the costs of egg production in birds. In this study, we investigated the effect of repeated cycles of egg production in response to experimental nest predation (egg removal) on hematological traits in female zebra finches (Taeniopygia guttata). We predicted that if the negative effect of egg production on hematocrit and hemoglobin concentration was cumulative, with anemia being proportional to reproductive effort, then females laying more clutches, or laying successive clutches without recovery during incubation, would show greater reproductive anemia. In contrast, if females maintain hematocrit and hemoglobin concentration at some minimum functional level independent of reproductive effort, then there should be no difference in hematological traits among females laying two or more successive clutches. Our results supported the second of these hypotheses: egg-laying females had reduced hematocrit (-7.5%) and hemoglobin concentrations (-10%), but the extent of reproductive anemia did not differ among females laying either two or three successive clutches, with or without recovery during incubation, or in females laying 7-21 eggs. Females maintained low hematocrit and hemoglobin for 20-35 d, and we suggest that prolonged periods of anemia might be common and functionally important in free-living birds, for example, where females produce multiple successive clutches in response to high levels of nest predation or where they initiate a second clutch while still rearing first brood chicks.

Chicken lines divergently selected for antibody responses to sheep red blood cells show line-specific differences in sensitivity to immunomodulation by diet. Part I: Humoral parameters

Individual differences in nutrient sensitivity have been suggested to be related with differences in stress sensitivity. Here we used layer hens divergently selected for high and low specific antibody responses to SRBC (i.e., low line hens and high line hens), reflecting a genetically based differential immune competence. The parental line of these hens was randomly bred as the control line and was used as well. Recently, we showed that these selection lines differ in their stress reactivity; the low line birds show a higher hypothalamic-pituitary-adrenal (HPA) axis reactivity. To examine maternal effects and neonatal nutritional exposure on nutrient sensitivity, we studied 2 subsequent generations. This also created the opportunity to examine egg production in these birds. The 3 lines were fed 2 different nutritionally complete layer feeds for a period of 22 wk in the first generation. The second generation was fed from hatch with the experimental diets. At several time intervals, parameters reflecting humoral immunity were determined such as specific antibody to Newcastle disease and infectious bursal disease vaccines; levels of natural antibodies binding lipopolysaccharide, lipoteichoic acid, and keyhole limpet hemocyanin; and classical and alternative complement activity. The most pronounced dietary-induced effects were found in the low line birds of the first generation: specific antibody titers to Newcastle disease vaccine were significantly elevated by 1 of the 2 diets. In the second generation, significant differences were found in lipoteichoic acid natural antibodies of the control and low line hens. At the end of the observation period of egg parameters, a significant difference in egg weight was found in birds of the high line. Our results suggest that nutritional differences have immunomodulatory effects on innate and adaptive humoral immune parameters in birds with high HPA axis reactivity and affect egg production in birds with low HPA axis reactivity.

Hematological changes associated with egg production: estrogen dependence and repeatability

The 'cost of reproduction' (i.e. the trade-off between current reproduction and future fecundity and/or survival) is a central concept in life history theory, yet we still know very little about the physiological mechanisms underlying such costs. Recently it has been recognized that reproduction itself or the regulatory (hormonal) mechanisms underlying reproduction might result in 'costs' (cf. resource-allocation based mechanisms). As one example, it has been suggested that the decrease in hematocrit observed during egg production in birds might be due to antagonistic pleiotropic effects of estrogens. This could generate costs of reproduction by reducing oxygen-carrying capacity during subsequent aerobically demanding stages such as chick-provisioning. Here we show that the reduction in hematocrit during egg-laying is dependent on receptor-mediated actions of endogenous estrogens: blocking estrogen receptors using the anti-estrogen tamoxifen reduces the decrease in hematocrit during egg production in female zebra finches (Taeniopygia guttata) such that hematocrit at the 1-egg stage is not significantly different than pre-breeding, baseline values. We also show that both pre-breeding hematocrit and the decrease in hematocrit associated with egg production are repeatable, and that females with the highest pre-breeding hematocrit values tend to show the largest decreases in hematocrit during egg production. We suggest that hematological changes during egg production are a good candidate mechanism for a regulatory-network based trade-off involving antagonistic pleiotropic effects of estrogens, which otherwise have essential reproductive functions.

Lifespan is unrelated to investment in reproduction in populations of mammals and birds in captivity

We examined the relationship between number of offspring produced to a certain age and subsequent longevity in captive zoo populations of 18 species of mammal and 12 species of bird. The age cut-offs in each analysis were set to include 50%, 75% and 90% of the offspring produced in each of the population samples. Only one of 68 regressions was significant, and its slope was positive. In addition, we examined the relationship between age at first reproduction up to a certain age and longevity after that age, generally 5 years (3-8), among 17 species of mammal and 12 species of bird. Only one of these regressions had a significantly positive slope, indicating that early reproduction rarely reduces lifespan. Overall, we found no evidence that producing offspring in a zoo environment influences the age at death. Thus, although trade-offs might apply in natural populations under resource limitation, neither pregnancy, growth of the foetus and lactation in mammals, nor egg production in birds, reduces lifespan in the absence of such stress. If genetically based or other intrinsic antagonistic pleiotropy underlies the evolution of senescence, it was not evident in our analyses.

Effect of suppression of plasma prolactin on luteinizing hormone concentration, intersequence pause days and egg production in domestic hen

The aim of this study was to investigate the effects of suppression of plasma prolactin (PRL) concentration on circulating concentrations of luteinizing hormone (LH), progesterone (P 4), estradiol (E 2β), pause days and egg production in birds later in the reproductive period. Twenty-four White Leghorn birds of same age group were divided into two groups of 12 in each. Birds of each group were administered s/c either with placebo (control group) or equal volumes of anti PRL agent (2-bromo-α-ergocriptine) solution containing at 100 μg/kg body weight/hen/week (treated group) from 72 to 82 weeks of age. Egg production and inter sequence pauses were recorded daily from both the groups. Plasma PRL, LH, E 2β and P 4 concentrations were estimated in blood samples collected at weekly intervals. At 77th weeks of age, blood samples from treated and control birds were obtained every 3 h for 36 h to study the surges of LH. It was found that plasma PRL concentration was lower ( p < 0.01) in bromocriptine treated birds with high concentrations of LH, its 3 h LH surges, E 2β and P 4 in plasma. Higher egg production, less pause days in treated birds may be the result of low PRL concentration, associated with positively correlated responses of high concentrations of LH (with regular interval and duration of LH surges), E 2β and P 4 concentration required for completion of egg formation and oviposition. In conclusion, bromocriptine administration decreased ( p < 0.01) PRL concentration increased ( p < 0.01) steroid hormones and LH surges, for egg formation and oviposition and enabled the birds to lay more eggs even later in the productive period with the available resources under normal husbandry practices.