Pause Days Research Articles

Anti-prolactin Agent with Gonadotropin-releasing Hormone Synergistically Improve Egg Production in Indigenous Chicken via Regulating Broody Behavior

Despite the indigenous chicken's many natural advantages, broodiness continues to be a substantial barrier to minimizing egg production and economic losses. Prolactin is the primary regulator of broodiness. As a result, the goal of our research was to see if lower prolactin levels can limit broodiness, resulting in increased egg production and increased economic value. Sixty indigenous chickens aged 18-20 weeks were divided into three groups of 20 hens each. One was left untreated, two were given GnRH (0.50 ml/bird @ S/C) with Anti-prolactin (Bromocriptine 640 g/bird/day @ orally), and three were given GnRH, Anti-prolactin, and cold therapy (1 time/day) for three months. The chickens were first given GnRH injections once a week for three weeks. It was given on the 13th day of egg production and continued for 10 days. After utilizing GnRH plus anti-prolactin medications for 13 days, the cold application was given every day at the same time. Hormone analysis, egg production, broody time, pause time was noted. Prolactin levels fell in all treatment groups. The number of egg production per clutch was significantly (p<0.05) increased in both treated groups, and the highest was recorded in GnRH plus anti-prolactin group (33eggs / clutch). Surprisingly, pause day and broody time significantly (p<0.05) decreased in the same Group B (7d, 4d respectively). Postmortem ovary analysis substantially supports the treatment group's finding against the control group. Overall, combining an anti-prolactin drug with GnRH enhances egg production by synergistically modulating broody behavior.

Genetics and breeding of a black-bone and blue eggshell chicken line. 2. Laying patterns and egg production in two consecutive generations

The BG line was originated from the cross between 2 Chinese indigenous breeds, Dongxiang blue eggshell, and Jiangshan black-bone, and has been bred to combine dark heavy black-bone body and high production of blue-shell eggs, into single dual-purpose line. Full-pedigree hens from 2 generations, G4 (n = 441) and G5 (n = 464), were reared in the same single-cage laying facility in 2019–2020 and 2020–2021, respectively. Starting from the first egg of each hen, its daily egg production was recorded until 300 days-of-age. Up to 7 "no-egg" days were considered normal laying breaks between clutches, whereas laying cessation of 8 or more days was considered Pause, and the laying pattern of each hen was assigned either with Pause or No-Pause. The other traits included PsDays: number of Pause days; AFE: age at first egg; EN300: eggs laid until 300 d; %L300: total laying rate (EN300/[300-AFE]); %Lnet: net laying rate (EN300/[300-AFE-PsDays]); ClLng: average clutch length; EW200 and EW300: average egg weight around 200 d and 300 d. Estimates of heritability (h2) of each trait, and phenotypic and genetic correlation between traits, were calculated in each generation using the animal model. Heritability estimates were calculated also by regressing the means of full-sib G5 hens on their G4 parents' means. Mean overall laying rate of all G4 hens was low (%L300 = 57%) because 53% of them had Pause in their laying pattern. In G5, incidence of Pause was higher (75%) due to a 3-wk cold stress, with mean %L300 = 54%. However, significant estimates of heritability and genetic correlations suggest that selection for low PsDays will reduce the incidence of Pause in BG hens and elevate the line's mean laying rate towards %L300 = 70%, as the No-Pause hens in G5. PsDays-free laying rate (%Lnet) was found to be highly correlated with the significantly heritable (h2≈0.4) clutch length (ClLng). Selection index combining the genetically independent low PsDays and high ClLng is expected to maximize egg production improvement in the BG line, and in similar populations derived from indigenous breeds.

Impact of Nano-Bromocriptine on Egg Production Performance and Prolactin Expression in Layers.

Simple SummaryEgg production is one of the most vital axes in the poultry industry. During the late laying period, the egg production continuously decreases, and pauses among the sequence of egg laying increases; however, the feed costs remain constant. Several attempts were carried out to improve the reproductive performance of laying hens by decreasing the prolactin level in the blood; an increase in this hormone initiates the onset of incubation behavior in chickens. In this study, we investigated the potential use of nano-bromocriptine to the improve egg production performance in laying hens. The use of alginate-bromocriptine leads to a significant reduction in the prolactin expression in the pituitary gland, which in turn allows the elongation in sequences and reduction in pauses, as well as the feed per dozen egg in laying hens. Further studies are needed to assess the impacts of nano-bromocriptine on other performance parameters. Thus, the improvement of egg production persistency must also go hand in hand with sustainable egg quality and the maintenance of the birds’ health.The current study aimed to investigate the potential use of nano-bromocriptine in improving the laying performance of late laying hens by modulating the prolactin gene expression. A total of 150 NOVOgen brown laying hens aged 70 weeks were randomly allocated into three groups of 50 birds each. The first group was kept as a control, while the second and the third groups were treated with bromocriptine and nano-bromocriptine, respectively, at a dose of 100 µg/kg body weight per week. The pause days, egg production, feed per dozen egg, and Haugh unit were determined on a monthly basis. Also, the relative prolactin gene expression in the pituitary gland was quantified using qPCR and the number of the ovarian follicles was determined after slaughtering at the 84th week of age. It was found that nano-bromocriptine and bromocriptine improved egg laying performance with minimal pause days, reduced feed per dozen egg, and depressed the relative prolactin gene expression; however, nano-bromocriptine treatment was significantly effective compared to bromocriptine. In conclusion, nano-bromocriptine might be beneficial for elongating sequences and reducing pauses.

Genetic parameters for clutch and broodiness traits in turkeys (Meleagris Gallopavo) and their relationship with body weight and egg production

The objective of this study was to estimate phenotypic and genetic parameters for clutch and broodiness (BR) traits in turkeys and their relationship with body weight and egg production. Data on dam line hens was available and included: body weight at 18 wk of age (BW18), body weight at lighting (BWL, 29 to 33 wk), age at first egg (AFE), egg number (EN), rate of lay (RL), clutch length (CL), maximum clutch length (MCL), pause length (PL), maximum PL (MPL) and BR. BR was defined as the average number of consecutive pause days between clutches that was higher than the average PL per hen. Heritability estimates for BW18 and BWL were 0.50 and 0.53, respectively. The heritability for egg production, clutch, and pause traits varied from low (MPL = 0.15; BR = 0.15) to moderate (AFE = 0.22; EN = 0.28; RL = 0.29; CL = 0.21; MCL = 0.27; PL = 0.25). Genetic correlations were negative between body weight traits and EN (rg (BW18, EN) = −0.27; rg(BWL, EN) = −0.33) and CL (rg(BW18, CL) = −0.40; rg(BWL, CL) = −0.33). BR was negatively genetically correlated with EN (rg(BR, EN) = −0.85) and CL (rg(BR, CL) = −0.30), and positively genetically correlated with PL (rg(BR, PL) = 0.93) and AFE (rg(BR, AFE) = 0.21). EN had a positive (0.73) and a negative (−0.84) genetic correlation with CL and PL, respectively. Overall, the results of this study confirmed the negative (unfavorable) correlations between egg production and body weight. Despite unfavorable genetic and phenotypic correlations between egg production traits and those relating to BR, the inclusion of BR in a selection program through incorporation of clutch length traits and pause length traits is feasible. Integration of either clutch length traits or pause length traits in a selection index is likely to increase egg number while decreasing broodiness.

GnRH-1, GnIH mRNA and Luteinizing Hormone in Domestic hens (Gallus gallus domesticus) Exposed to Different Wavelengths of light

The objective of this study was to establish the effects of red spectrum of light (650nm, treated n=12) and normal spectrum of light (450nm control=12) on GnRH-I and GnIH mRNA expression, amplitude and frequency of luteinizing hormone (LH) and egg production from 42 to 52 weeks of age in white leghorn hens. Blood samples were collected at weekly interval from both the groups. At the 47th week of age blood samples from both the groups were collected at every 3 h for 36h to study the pulsatile secretion of LH surges. GnRH and GnIH mRNA expression pattern was studied between control and treated birds. Egg production and pause days were calculated between the two groups. LH concentration in the plasma was increased significantly (P<0.01) in hens exposed to red spectrum of light. Plasma LH concentration was higher (P<0.01) in treated birds with more number of LH surges. The amplitude and frequencies of LH were advanced in birds exposed to red spectrum of light during 36 h of sampling at 3h intervals. GnRH-I mRNA concentration was significantly (P<0.01) higher, whereas GnIH mRNA was significantly (P<0.01) lower in birds exposed to red spectrum of light compared to controls. It is hypothesized that exposure of birds to red spectrum of light enhanced (P<0.01) GnRH-I mRNA, along with LH required for ovulation and egg lay. During 77 days (42-52 weeks of age) of the experimental period, egg production was increased (p<0.01) with lower incidence of pause days in the treated group. It is concluded that low GnIH mRNA and higher levels of GnRH-I mRNA, LH, lower number of pause days enabled the birds to lay more eggs by stimulating GnRH through red spectrum of light.

Effect of serum from laying hen and antiprolactin drug on egg production of indigenous chicken in Bangladesh

The study was carried out to improve egg production by decreasing the inter sequence pause days in indigenous chicken through the use of antiprolactin agent (Bromocriptine) and serum from laying hen. Sixty indigenous (deshi) chickens of 20-22 weeks of age, were randomly assigned into four groups (A, B, C and D) and each group consisting of 15 hens. Group A designated as control, group B was treated with Bromocriptine orally at a dose of 640 μg/bird/day, group C was treated with serum of laying hen at a dose of 1 ml intramuscularly/bird/day and group D was treated with both serum and Bromocriptine at doses given to group B and C for the period of 15 March, 2015 to 16 June, 2015 and egg production, pause days, prolactin level, hematological parameter and egg qualities were observed. Egg production increased significantly (p<0.05) in all treated groups compared to the non- treated control group and the highest production was recorded in group D. Pause days and prolactin levels decreased significantly (p<0.05) in all treated groups and lowest were recorded in hens of group D. No significant (p>0.05) differences were observed in hematological values among the group of chicken. The present study reveals that combined treatment with Bromocriptine and serum from laying hen increases egg production without affecting the health of indigenous chickens.
 Asian Australas. J. Biosci. Biotechnol. 2017, 2 (1), 51-54

A case of peripartum cardiomyopathy occurred at 9 days after giving birth

The aim of this study was to investigate the basic physiological mechanism involved in taking pauses between the sequences of egg laying in domestic hen to improve egg production by extending the sequence length and decreasing the intersequence pause days by modulating the prolactin concentration in birds. Fifty healthy female white leghorn birds were administered anti-prolactin agent (2-bromo-α-ergocriptine, Sigma, USA) subcutaneously at 100μg/kg body weight at weekly intervals from 17th to 36th week of age. Another group of fifty birds was given placebo in place of the modulating agent. The level of prolactin remained lower in the treated birds than in the control birds throughout the production cycle up to 72 weeks of age. The level of prolactin in the control group was found to decrease during the peak production period. The average percentage of egg production from 19 to 72 week period was 87.67 in the treatment group as compared to 83.56 in the control group. Oestradiol-17β and progesterone concentrations in the treated birds were significantly (P<0.01) higher than those in control birds, during and after withdrawal of the treatment. Prolactin level was negatively correlated with egg production (r=−0.02; r=−0.12) and with oestradiol-17β (r=−0.75; r=−0.38) and progesterone (r=−0.20; r=−0.83), respectively, in control and treatment groups. The total number of pause days during the production period decreased significantly (P<0.01) in the treatment group, resulting in a 4.11% increase in egg production. It is concluded that there is a consistent relationship between plasma prolactin in the physiological range and laying performance in domestic hen.

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.

English

The study was conducted to analyze the laying characteristics of Nera black hens in a hot and humid environment and assess the physical characteristics of good, intermediate and poor layers. Seventy-five eight months old Nera black hens of mean body weight 1.35 &plusmn; 0.24 kg (range: 1.20 -1.65 kg) in their 12th week of lay and housed individually in battery cages were used for the study. Eggs were collected daily and recorded for each hen. The hens were subsequently divided into three classes based on their laying performance as follows: Good layers, intermediate layers and poor layers and their physical conditions appraised. Results showed that the peak of lay was between 06:00 to 08:00 h and egg production declined gradually throughout late afternoon hours until no egg was laid between 17:00 and 18:00 h. About 88.75 and 11.25% of the eggs were laid in the morning and afternoon hours, respectively.&nbsp; Eggs laid between 6:00 and 7:00 h had the heaviest (P&lt;0.05) mean egg weight (70.10 &plusmn; 0.92 g) and the first eggs in a clutch were the heaviest eggs (P&lt;0.05). Hens with the longest clutches and shortest number of pause days produced the greatest number of eggs. Good and intermediate layers had smooth, pinkish and full combs and wattles, moist and enlarged vents and flexible pubic bones with wide space in-between. Poor layers had dry combs and wattles, tight and hard abdomen and narrow space between pubic bones. It was concluded that Nera black hens could lay up to 229.68 eggs/annum and lay most eggs between 06:00 and 08:00 h of the day. Egg collection especially in floor managed flocks should be intensified within this time period to minimize losses from cracks and egg eating by the birds. &nbsp; Key words: clutch traits, egg production, Nera black, oviposition time, pause days.

Study of Oviposition Pattern and Clutch Traits in a White Leghorn (WL) Layer Population

Various layer traits were recorded on 1082 pullets at 29 th generation of selection to evaluate the variability for egg production. Oviposition time of each egg was recorded at hourly and half an hour intervals under 16L: 8D cycle, up to 40 weeks of age and for 15 days period respectively, to study the distribution pattern of oviposition time. Early (06-11h) and late (11-17 h) pattern of oviposition, with 90 % of ovipositions occurring before 13 h of the day was observed. Mean oviposition time (MOT) and mean oviposition interval (MOI) of the flock were 10.99 h and 24.34 h at hourly intervals, whereas, 10.70 h and 24.43 h at half an hour intervals of recording, respectively. Mean values of clutch length, clutch number, maximum clutch length, total pause days and interval between clutches were found to be 11.10 days, 12.69, 38.15 days, 23.67 days and 2.20 days respectively. Recorded data revealed variable degree of skewness and kurtosis for different traits. Clutch traits revealed more variation than MOT and MOI. The distribution of MOT and MOI showed narrow range and low percentage coefficient of variation than other traits.

GnRH-1 mRNA, LH surges, steroid hormones, egg production, and intersequence pause days alter in birds exposed to longer wavelength of light in the later stages of production in Gallus gallus domesticus

The objective of this was to establish the effects of red spectrum of light (650 nm, treated n = 12) and normal spectrum of light (450 nm control = 12) on GnRH-I mRNA expression, amplitude and frequency of luteinizing hormone (LH), and egg production from 72-82 weeks of age in white leghorn hens. Birds exposed to red spectrum of wavelength significantly improved (P < 0.01) steroid hormone, and egg production improved over old laying 72 to 82 weeks. Weekly interval profiles followed the same pattern. At 77th weeks of age blood, samples from both the groups were collected at every 3 h for 36 h to study the pulsatile secretion of LH surges. Plasma LH concentration was higher (P < 0.01) in treated birds with more number of frequencies and amplitude LH surges in plasma of treated birds. LH frequencies were more pronounced and advanced during 36 h of sampling at 3 h interval in treated birds. Weekly interval of plasma LH, E2β, and P(4) concentrations increased (P < 0.01) in treated birds from 72 to 82 weeks of age. GnRH-I mRNA concentration was significantly (P < 0.01) higher in birds exposed to red spectrum of light compared to controls. It is hypothesized that exposure of birds to red spectrum of light-enhanced (P < 0.01) GnRH-I mRNA with more number of yellow yolky follicles was found in birds exposed to red spectrum of light during 77 days (72-82 weeks of age) of experimental period. It is concluded that higher levels of GnRH-I mRNA, LH, E2β, and P(4) concentration with lower incidence of pause days enabled the birds to lay more eggs even later in the productive period by modulating the wavelengths of light under normal husbandry conditions.

The Physical and Laying Characteristics of Golden Sex-Linked Hens under the Humid Tropical Environment

A total of fifty-two Golden-sex link (brown) hens in their 65th week of lay were used in a study conducted to determine the oviposition time and interval, total egg production, clutch length and number of pause days of the birds under the humid tropical environment. The hens were also divided into four classes on the basis of their laying performances as follows: good layers, intermediate layers, poor layers and non layers and their physical conditions appraised. The birds were supplied water ad libitum and fed layers mash containing 16.5% crude protein and 9.62 MJ/kg ME for 5 weeks. Results showed that the peak of lay was between 7.30-8.30 am and declined gradually until only one egg was laid between 3.30-4.30 pm. About 66.36% and 33.64% of the eggs were laid in the morning hours and in the afternoon hours, respectively. The mean oviposition interval was 26.61 h, while the average laying intensity was 48.90%. About 98% of the clutch lengths were of 5 cycle lengths and below, with the highest frequency of occurrence being 1 cycle length. The total number of pause days over all birds was 558 days. Hens with the longest clutches and shortest number of pause days produced the greatest number of eggs. Observation made on the physical characteristics revealed that good layers had smooth and waxy comb and wattles. The vents were moist and enlarged with flexible pubic bone, soft abdomen and worn out feathers. Intermediate layers had similar features with the good layers except that eye rings, beaks and shanks were slightly bleached. Poor layers had dry combs and wattles; tight and hard abdomen and closed pubic bones. Non layers had scaly, dry and rough comb and wattles; dull eyes and rigid pubic bones which were relatively close together.

Immunization Against Vasoactive Intestinal Peptide and its Effects on Prolactin, Steroid, Luteinizing Hormone and Egg Production During Mid Laying Cycle in Punjab Brown (PB3 ) Birds

Objective of the study is examine the effects of active immunization against chicken Vasoactive Intestinal Peptide (chVIP) on plasma prolactin (PRL) concentration, concentration of luteinizing hormone (LH) profile its interval and duration, Progesterone (P ), Estradiol (E s), intersequence pause days and egg 4 2 production in birds during the later stages of egg production from 48-72 weeks of egg lay in PB3 birds. Twenty-four PB3 birds of same age group were divided into 2 groups of 12 in each. Birds in control group were administered s/c with placebo. Equal volume of chVIP immunogenic protein was administered to treated group from 17 week of age to 36 weeks of age at an interval of 4 weeks. Hormonal profiles of th immunized and control birds were quantified at weekly intervals from 48th to 72nd weeks of age in both the groups for prolactin, LH, estradiol, progesterone. Egg production and pause days were recorded in both the groups. At 59th weeks of age, blood samples from chVIP immunized and control birds were obtained every 4 h for 48 h to study the surges of LH. In immunized PB3 birds (against ch VIP) plasma PRL concentration was lower (p<0.01) with high concentrations of E s, P , LH and its 4 h LH surges in plasma. Significantly 2 4 (p<0.01) higher egg production (13.62%) and less pause days were observed in chVIP immunized birds. It is mainly attributed due to low PRL concentration, associated with high concentrations of LH (with regular interval and duration of LH surges), Es and P concentration required for egg formation and subsequent 2 4 ovulation. In conclusion, chVIP immunization advanced the LH surges, for release of matured oocyte, egg formation and egg lay enabled the birds to lay eggs at regular intervals due to active immunization against chVIP. Results indicate that control of chVIP may lead to more egg production with shorter duration of LH surges.

Prolactin, Luteinizing Hormone and Steroid Hormone Concentration in Punjab Brown (PB3) Birds Immunized Against Vasoactive Intestinal Peptide During the Early Stages of Egg Production

This study aims at the effects of active immunization against chicken Vasoactive Intestinal Peptide (chVIP) on plasma prolactin (PRL) concentration, concentration of Luteinizing Hormone (LH) profile its interval and duration, progesterone (P ), estradiol (E s), intersequence pause days and egg production in 4 2 birds during the initial stages of egg production from 20-36 weeks of egg lay in PB3 birds. Twenty-four PB3 birds of same age group were divided into two groups of twelve in each. Birds in control group were administered s/c with placebo. Equal volume of chVIP immunogenic protein was administered to treate d group from 17th week of age to 36 weeks of age at an interval of four weeks. Hormonal profiles of immunized and control birds were quantified at weekly intervals from 17th to 36th weeks of age in both the groups for prolactin, LH, estradiol, progesterone. Egg production and pause days were recorded in both the groups. At 31st weeks of age, blood samples from chVIP immunized and control birds were obtained every 4 h for 48 hours to study the surges of LH. In immunized PB3 birds (against ch VIP) plasma PRL concentration was lower (p<0.01) with high concentrations of E s, P , LH and, its 4h LH surges, in plasma (p<0.01). Significantly 2 4 higher egg production (9.71%), less pause days were observed in chVIP immunized birds. It is mainly attributed due to low PRL concentration, associated with high concentrations of LH (with regular interval and duration of LH surges), E s and P concentration required for egg formation and subsequent ovulation. In 2 4 conclusion, chVIP immunization advanced the LH surges, for release of matured oocyte, egg formation and egg lay enabled the birds to lay eggs at regular intervals due to active immunization against chVIP. Results indicate that control of chVIP may lead to more egg production with shorter duration of LH surges.

Chemical Control of Prolactin Secretion and It`s Effects on Pause Days, Egg Production and Steroid Hormone Concentration in Girirani Birds

The objective of this study was aimed to improve egg production by decreasing the intersequence pause days between the sequences of egg lay in girirani birds through chemical control of prolactin by using bromocriptine (an anti prolactin chemical) through feed. At 12 weeks of age, forty two girirani birds were randomly divided into control (n=21) and treated (n=21) groups. Birds in the treated group were fed bromocriptine through feed @ 350µg/bird/day from 17-36 weeks of age and controls were fed the same ration without bromocriptine. Birds fed with bromocriptine through feed significantly (P<0.01) reduced the prolactin concentration compared to control birds. Estradiol and progesterone were quantified in both the groups. Treated birds showed higher (P<0.01) concentration of estradiol and progesterone concentration from 19th to 72 weeks of age with intermittent fluctuations. Egg production, pause days, and hormonal parameters were correlated between the two groups. Prolactin is negatively correlated with egg production (r = -0.89), estradiol (r = -0.59) and progesterone (r = -0.37) hormones and positively correlated with inter sequence pause days with concomitant decrease in egg production. Birds fed bromocriptine through feed showed significantly (P<0.01) less pause days and more egg production. The results of this study showed that, controlling the prolactin secretion by chemical means resulted in 5.12% increase in egg production over control birds, further such an approach is more promising, practicable, economical without any traces of chemical in meat, egg and blood to improve egg production in backyard poultry farming. It is concluded that chemical control of prolactin plays a major role on pauses days , prolactin secretion and egg production in native breed of birds.

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.

Inter Sequence Pause Days, Egg Production, Steroid and Luteinizing Hormone in Domestic Hen (Gallous domesticus) Immunized Against cProlactin

Prolactin (PRL) is a versatile hormone synthesized and secreted by the specialized cells in vertebrate anterior pituitary and is one of the important hormone involved in regulating endocrine hormones and egg production in birds. The aim of this study was to lower the cPRL concentration in White leg horn birds (WLH) by active immunization against cPRL during the productive period (from 19-72 weeks of age), for studying and comparing the effects of low prolactin levels on the circulating concentrations of luteinizing hormone (LH), progesterone, estradiol, sequence length, intersequence pause days and egg production with the control birds of the same age group. WLH birds at 13 weeks of age were divided into two experimental groups consisting of 21 birds each in control and immunized birds. At 17 week of age, 21 th birds were immunized with cPRL (conjugated with keyhole limpet haemocyanin KLH-cPRL), followed by three booster doses at four weekly intervals with a total of four immunizations. Controls were given placebo in place of immunogen. Active immunization of the birds against cPRL significantly (P<0.01) decreased the circulating PRL concentration. cPRL antibody titers were checked at monthly intervals and found from 20 week of age to age to till 72 weeks of age in immunized birds. Estradiol, progesterone and LH concentrations were increased significantly (P<0.01) during and after the withdrawal of immunizations. Egg production was positively correlated with estradiol-17 s (r=0.42) progesterone (r=0.52) and LH (r=0.75), whereas cPRL level was negatively correlated with egg production (r=-0.14), estradiol-17 s (r= -0.25) progesterone (r=-0.32) and LH(r=-0.15). The total number of pause days during the production period decreased significantly (p<0.01) in the immunized group resulting in a 5.40% increase in egg production. It is concluded that there is a consistent relationship between plasma prolactin in the physiological range, intersequence pauses and laying performance in domestic hen.

Active Immunization Against cVIP and It`s Role on the Pattern of Sequence Length and Pause Days in Domestic Hen (Gallous domesticus)

Chicken vasoactive intestinal peptide (cVIP) is a hypothalamic PRL (PRL) releasing factor in birds and it plays an important role avian reproduction. Our objective was to determine whether active immunization against cVIP would increase the sequence length, decrease intersequence pause days, and there by improving egg production in White Leghorn (WLH) by decreasing the prolactin (PRL) concentration during the active period of productive cycle in birds. WLH birds at 13 weeks of age were divided into two experimental groups consisting of 21 birds in control and immunized birds. At 17 week of age, 21 birds th were immunized with synthetic chicken VIP (conjugated with keyhole limpet haemocyanin KLH-cVIP), followed by three booster doses at four weekly intervals with a total of four immunizations. Controls were given placebo in place of immunogen. cVIP antibody titers were consistent till the age of 72 weeks in immunized birds. Active immunization of the birds against cVIP significantly (P<0.01) decreased the circulating PRL during and after the withdrawal of immunizations and PRL levels were found to decrease up to the age of 72 weeks of age, resulting in significantly lower incidence of shorter sequences, with significantly (P<0.01) lower number of intersequence pause days, egg laying sequence lengths in bird s immunized against cVIP. Total number of pause days were significantly reduced in immunized birds compared to controls. Egg production increased by 7.00% in the immunized birds over the control birds with the available resources under normal husbandry practices. It is observed that the laying pauses are mainly due to fluctuations in the concentration of PRL above physiological levels in circulation and keeping the PRL hormone under check will influence egg production, pause days, sequence length, persistency in eg g production with almost an egg a day. It is conclude that the physiological pauses that occur during ovulatory sequences can be disrupted effectively using active immunization against cVIP, which modulates PRL levels, that may interfere with the follicular recruitment and subsequent oviposition thereby improving egg production in white leghorn hens.

The possible role of prolactin in laying performance and steroid hormone secretion in domestic hen ( Gallus domesticus)

The aim of this study was to investigate the basic physiological mechanism involved in taking pauses between the sequences of egg laying in domestic hen to improve egg production by extending the sequence length and decreasing the intersequence pause days by modulating the prolactin concentration in birds. Fifty healthy female white leghorn birds were administered anti-prolactin agent (2-bromo-α-ergocriptine, Sigma, USA) subcutaneously at 100 μg/kg body weight at weekly intervals from 17th to 36th week of age. Another group of fifty birds was given placebo in place of the modulating agent. The level of prolactin remained lower in the treated birds than in the control birds throughout the production cycle up to 72 weeks of age. The level of prolactin in the control group was found to decrease during the peak production period. The average percentage of egg production from 19 to 72 week period was 87.67 in the treatment group as compared to 83.56 in the control group. Oestradiol-17β and progesterone concentrations in the treated birds were significantly ( P<0.01) higher than those in control birds, during and after withdrawal of the treatment. Prolactin level was negatively correlated with egg production ( r=−0.02; r=−0.12) and with oestradiol-17β ( r=−0.75; r=−0.38) and progesterone ( r=−0.20; r=−0.83), respectively, in control and treatment groups. The total number of pause days during the production period decreased significantly ( P<0.01) in the treatment group, resulting in a 4.11% increase in egg production. It is concluded that there is a consistent relationship between plasma prolactin in the physiological range and laying performance in domestic hen.

Daily temporal organization of laying in Japanese quail: variability and heritability

In birds, many behavioral and physiological processes that occur during reproduction show daily rhythms in response to environmental temporal constraints. In this study, the individual daily organization of laying and its genetic determinant in Japanese quail (Coturnix coturnix japonica) were analyzed. For this purpose, the oviposition time of 102 randomly chosen females, maintained in long-day photoperiodic conditions (LD 14h:10h) for 1 mon was observed and extreme phenotypes selected. Laying is characterized by two parameters: oviposition interval and laying hour.The birds showed a specific time of laying during 24 h. All eggs were laid in the afternoon between 6.5 and 14 h after lights on (HALO). Two laying profiles were determined: 20% of females with an oviposition interval greater than 24 h (24.7±0.2 h) (the “delayed” profile) laid progressively later each day until a pause day. The remaining 80% of the females laid at the same time each day, with few pause days and an oviposition interval close to 24 h (24.0±0.2 h) (the “stable” profile). Among the females, showing this last profile, an intra-individual stability and an inter-individual variability of laying hour was established. Two extreme laying phenotypes were then determined: the “early” phenotype (E) for females laying on average between 7.5 and 9.5 HALO and the “late” phenotype (L) for females laying between 12.5 and 14 HALO.In order to study the genetic basis of the laying hour, three females of each extreme phenotype were selected and crossed with two different males. The E and L females produced 57 F1E and 42 F1L daughters, respectively. F1 females displayed both laying profiles. However, the proportion of females displaying a “delayed” profile was higher in the L line (50%) than in the E line (29.8%). For the “stable” daughters, artificial selection induced an advance in laying hour of 4.7% for the E line and a delay of 4.7% for the L line. Realized heritability was estimated at 0.5. Moreover, the laying hour of the daughters was correlated positively to that of the mothers (N=61;r=0.45). These results support the notion of heritability of oviposition time in Japanese quail.