Egg Production Period Research Articles

Life history of the ghost shrimp, Callianassa japonica Ortmann (Decapoda: Thalassinidea), on an intertidal sandflat in western Kyushu, Japan

Growth, density, survival, and reproduction were examined for the population of the ghost shrimp, Callianassa japonica Ortmann, inhabiting an intertidal sandflat in western Kyushu, Japan, based on samples collected from May, 1989 to April, 1991. During the breeding season (June–October) each year, there were two discrete periods of egg production by females. The post-larval settlement, with a time-lag of 1–1.5 months (brooding plus larval developmental periods), generated two major recruitment cohorts, occurring in July–August (1st cohort) and September–November (2nd cohort). The higher growth rate of individuals after recruitment in the 1st cohort enhanced the separation of the two cohorts. Between sexes, the subsequent life history patterns and population characteristics were, for the most part, similar. In females, the majority of individuals of each of the two cohorts matured after approximately one year, respectively, at around a 20-mm total body length, and a portion of these cohorts survived as a fused cohort until June of the second year, breeding again prior to dying off by the end of September. The pattern of growth was an indeterminate type. For each of the two cohorts, the growth rates changed at two transition points of their life history, at around the beginning of their two breeding seasons. The growth rate for the 1st cohort slowed down at the first transition point, while that for the 2nd cohort speeded up there. This led to the approach and fusion of the two cohorts near the second transition point, when growth stopped. During periods other than the breeding seasons, high survival rates were exhibited by the two cohorts. During the first breeding season, a significantly low survival rate was observed for the 1st cohort, but not for the 2nd cohort. The degree of participation in breeding activity may be responsible for the above differences between cohorts. In the two male cohorts, while the cost of reproduction did not reduce the growth rates during the first breeding season, it lowered their survival rates more severely compared to those of females. This may be responsible for the slightly female-biased sex ratio in the population (1.06:1). The density of the population as a whole was stable throughout the study period, with the mean ± SD being 901 ± 157/m 2 ( n = 27); the adult population declines during the breeding seasons were effectively replenished by recruitment each year.

Spawning of plaicePleuronectes platessaL. around the Isle of Man, Irish Sea

The locations and timing of plaice Pleuronectes platessa spawning around the Isle of Man were studied from distributions of recently spawned eggs recorded in plankton samples. The area of intense spawning activity south-east of the Isle of Man was found to be further north than indicated in the literature. A previously disregarded spawning ground oV the west coast of the Isle of Man was identified in 1991, 1992 and 1993, although egg densities were lower than oVthe east coast. Production of stage I eggs on the west coast spawning site was estimated at approximately 2% of the total plaice egg production in the Irish Sea. This would be suYcient to supply the local nursery grounds on the west coast of the Isle of Man with plaice larvae. Plaice spawned between early February and early April oV the west coast of the Isle of Man, with March as the main period of egg production. Plaice therefore spawn well before the spring plankton bloom in the Irish Sea. ? 1997 International Council for the Exploration of the Sea

Immunocytochemical evidence for the involvement of an FMRFamide-related peptide in egg production in the flatworm parasitePolystoma nearcticum

The monogenean flatworm Polystoma nearcticum exhibits reproductive synchrony with its treefrog host, Hyla versicolor, and becomes reproductively active only during the short period of host sexual activity at spawning. In this way, it provides a useful model system for exploring factors that may influence egg production in flatworm parasites. One such factor is the peptidergic innervation of the egg chamber or ootype. By using immunocytochemical techniques, the occurrence and distribution of GYIRFamide-like immunoreactivity, an authentic flatworm FMRFamide-related peptide (FaRP), have been monitored in the cells and fibres innervating the reproductive apparatus of worms collected at different stages of host sexual activity. Serotonin (5-HT) immunoreactivity in the worm was mapped for comparison. Extensive immunostaining for the FaRP and 5-HT was obtained throughout both the central and the peripheral nervous systems of worms, which were recovered from reproductively active frogs. In contrast, the innervation of the ootype of worms that were determined to be sexually inactive, including those recovered from frogs postspawning, showed little or no immunoreactivity for the FaRP; immunostaining for 5-HT in the ootype was unaffected by the reproductive state of the worm. These results indicate that FaRP expression in the neurons of the ootype innervation of P. nearcticum coincides with the parasite's brief period of egg production and, thus, provides evidence that regulatory peptides may be involved in the egg-assembly mechanism in flatworm parasites.

Simulation of the transmission of Salmonella enteritidis phage type 4 in a flock of laying hens.

Simulation of disease transmission in laying flocks infected with Salmonella enteritidis phage type 4 over a 48-week egg-production period indicated that the maximum weekly incidence risk could range from 0.05 to 0.28, and the maximum proportion of culture-positive birds could range from 0.20 to 0.77 of the flock, depending on the effective contact rate. If the egg contamination proportion were 0.08, contaminated egg production could vary from a weekly maximum of 0.42 per cent to 2.24 per cent depending on the effective contact rate, but the actual rate of contamination was more important in determining the numbers of infected eggs produced. The results from previous studies suggest that this proportion could range from 0.075 to 0.25. The model produced levels of infected and immune birds similar to those reported in the literature, suggesting effective contact rates of between 2 and 4.5. There is insufficient information on transmission cycles to validate the model, but it does provide a mechanism for consolidating research findings, reviewing areas for further research, and aiding more effective planning for disease control.

Evaluation of Early Feed Restriction on Egg Size and Hen Performance

Feed restriction was implemented in a factorial design (2 × 4) when pullets were at either 5 or 10% egg production. Periods of feed restriction were for 0, 3, 4, or 5 d. Two trials each using 672 Hy-Line® W-77 White Leghorn hens 19 wk of age were identified and randomly assigned to 16, 2 × 3 m pens at a density of 7 birds per square meter. Data recorded were days at sexual maturity, egg production, mortality, feed consumption, feed conversion, egg weight, body weight gain, and body weight uniformity.Hens placed on feed restriction reached sexual maturity 3 to 5 d later (P < 0.05) than the unrestricted birds. No significant main effects or interactions were found for egg production, feed consumption, feed conversion, mortality, egg weight, body weight gain, or body weight uniformity for the initial 15 wk or the entire egg production period. These results suggest that early egg size was not increased with the practice of early feed restriction nor did short- or long-term laying performance improve.

Population energetics of bacterial-feeding nematodes: Stage-specific development and fecundity rates

By grazing on bacteria, bacterial-feeding nematodes participate in decomposition food webs and N mineralization to an extent determined by metabolic and behavioral attributes and by life history. We determined the stage-specific development and fecundity rates for seven species on a physiological time scale to allow time and temperature-varying predictions of population progressions. Development from egg to adult of four species in the Rhabditidae ( Bursilla labiata, Caenorhabditis elegans, Cruznema tripartitum and Rhabditis cucumeris) was faster than that for three species in the Cephalobidae ( Acrobeloides bodenheimeri, A. buetschlii and Cephalobus persegnis) on a Julian time (calendar) basis at 20°C. Development in the Rhabditidae was generally faster on a physiological (degree-day) time scale as well, but those times are not directly comparable as the basal threshold for degree-day (DD) accumulation differed among the species. The fecundity period for females of the seven species varied between 55 and 75% of the total duration of the life course, during which they produced between 125 eggs ( B. labiata) and 567 eggs ( C. tripartitum). Simulated population growth under favorable temperature conditions, using parameter values determined in these studies, indicated rapid population growth in the large-bodied, highly-fecund rhabditid species ( R. cucumeris and C. tripartitum). Population growth was intermediate in the small-bodied, less-fecund rhabditids with short egg-production periods ( B. labiata), slower in the cephalobids ( A. bodenheimeri and A. buetschlii) and slowest in C. persegnis. R. cucumeris spent a greater proportion of its development time in the egg stage than did any of the other species.

Heritablity Estimates of Some Clutch Traits in the Laying Hen.

Oviposition time of 419 hens from a White Leghorn population of two lines divergently selected for high and low yolk-albumen ratio was observed at four stages of egg production period for a duration of about 30 days in each stage. A total of 1, 498 records were used in the analyses of this study. The clutch traits for heritability estimation include; intra-clutch mean lag of oviposition time (LAG), mean delay of pause day between clutches (DELAY), the rate of internal laying (IP), the number of clutches (CN), the average length of clutches (CL), and the average size of clutches (CS). LAG and DELAY were estimated by the multiphasic model (LUC et al., 1995). Heritabilities of these clutch traits were estimated by a sire-dam nested model and intra-sire regression of daughter on dam.Means of LAG were 1.04 hours and 1.32 hours for high and low lines, respectively. Corresponding heritability estimates were 0.41, 0.32, 0.62, and 0.55, 0.51, 0.62 for sire component and combined components of sire and dam, and intra-sire regression coefficient of daughter on dam, respectively. Heritability estimates of DELAY were not different from zero in both lines using the two methods. Medium and high heritability estimates of CN, CL and CS were found for both high and low lines in the two methods, except for regression estimates in the high line. Heritability estimates in the low line were higher than that in the high line for most traits, except for DELAY and IP.

Fecundity of the blood-feeding insectRhodnius prolixus increases in successive periods of egg production

The fecundity of the blood-feeding insect,Rhodnius prolixus, was observed to increase in successive periods of egg production, each period being triggered by a single large blood meal. As previously published, the fecundity of mated animals was significantly higher than that of unmated animals for the first period of egg production. For a second period of egg production, fecundity increased significantly in both mated and unmated animals. By the fourth period, fecundity had returned to first-feed values for mated animals, but remained high for unmated animals, and the fecundity of mated and unmated animals was not significantly different. Thus, during successive periods of egg production, the processes which maintain fecundity of unmated animals below that of mated animals are overcome.

Oxygen consumption and egg production in the blood feeding insectRhodnius prolixus

Summary Resting O2 consumption as measured by respirometry rises sharply immediately after feeding in females of Rhodnius prolixus and undergoes a slow decline after about the fourth day, returning to pre-feed levels by the tenth or twelfth day after feeding. The O2 consumption of mated females remains slightly higher than that of virgin females during the period of egg production. Thus, virgin females, earlier shown to produce fewer eggs from a blood meal of equivalent size without gaining weight, do not maintain their weight by an elevated resting metabolism. The O2 consumption of ovariectomized females, while not reaching the same level as normal females, exhibits the same sharp increase after feeding, but that increase is absent in allatectomized females. While these facts may indicate a role for juvenile hormone in controlling the level of oxidative metabolism, the effect of other hormones cannot be ruled out.

Light Intensity and Sex Ratio Effects on Egg Production, Egg Quality Characteristics, and Fertility in Breeder Pekin Ducks

A flock of 520, 11-wk-old breeder Pekin ducklings was raised in 20 floor pens in a curtain-sided poultry house under decreasing day lengths. At 22 wk of age, the ducklings were photostimulated (16 h of light/day) with a combination of natural daylight and artificial light. After dusk, half of the ducklings were exposed to 10 lx of incandescent (IN) light and the other half were maintained under 172 lx of high-pressure sodium (HPS) light. In addition, each light treatment consisted of an equal number of pens with two different sex ratios, 22 hens:4 drakes (15% males) and 21 hens:5 drakes (19% males).Egg production, egg quality characteristics, and fertility were monitored from 22 to 52 wk of age. Ducklings housed under 172 lx of HPS light exhibited significantly (P ≤ .05) greater egg production between 23 and 34 wk of age. Egg weight, shell weight, and shell thickness were not consistently affected by the different light treatments or sex ratios. The sex ratios did not affect percentage egg fertility, but fertility was significantly (P ≤.05) higher in the HPS light treatment during the last 15 wk of the study.It was concluded that HPS light of 172 lx can enhance egg production in breeder Pekin ducklings prior to peak production (37 wk), and HPS light can improve fertility following the peak egg production period. Furthermore, this study indicated that a breeder duckling flock with 15% males was adequate to achieve optimum fertility.

Effect of Light Intensity Level During Prelay Light Restriction on Subsequent Reproductive Performance of Turkey Breeder Hens

Two trials were conducted to determine whether light intensity levels during the prelay (light restriction) and the lay (egg production) periods influenced subsequent photoinduced reproductive performance of turkey breeder hens. The light intensity levels were 22 and 270 lx and each was provided during the prelay and lay periods in a factorial arrangement. Each of the lay period light intensity levels were applied to half of the hens from each prelay treatment group. Data were collected for BW, rate of reproductive development, egg production, fertility, hatchability, egg weight, and poult weight.There were no interactions between the prelay and lay period treatments, nor a consistent prelay light intensity effect on rate of initiation of lay or duration of time to achieve 50% production. In addition, prelay and lay light intensity levels had no consistent effects on rate of lay, percentage of fertility and hatchability, egg weight, and poult weight. It was concluded that there was no advantage to the use of high-intensity light during short-day light restriction of the prelay period on subsequent reproductive performance.

Egg Production Models for Molted Flocks

Three nonlinear models of poultry flock egg production (Adams-Bell, compartmental, and logistic-curvilinear or modified compartmental) were compared using weekly egg production data from 47 molted commercial flocks. Models were fitted to all data and to the first 20 wk of data using a nonlinear least squares procedure. Predictive ability of the models and of linear regression from the peak of production to the 20th wk was tested by extrapolating to the rest of the egg production period. Analysis of variance was used to compare goodness of fit of the nonlinear models and predictive performance of the nonlinear and linear models, with orthogonal contrasts to separate means. The mean R2 values of the Adams-Bell model for fits to all data and to 20 wk of data were higher (P<.001) than R2 values for the compartmental model, but were not higher than R2 values for the logistic-curvilinear model. Mean percentage error of prediction for the Adams-Bell model (.95%) was different (P<.01) from the compartmental (−4.11%), logistic-curvilinear (2.97%), and linear models (−1.04%). Errors for the Adams-Bell and linear models were approximately equally biased from zero, but in opposite directions. Means of absolute values of percentage errors were different (P<.001) between the Adams-Bell and compartmental models, but not between the Adams-Bell and either the logistic-curvilinear or the linear models. The Adams-Bell model is the best nonlinear egg production model for molted flocks, and it predicts future egg production as well as linear regression on data after peak production.

Modification of the Ethidium Bromide Exclusion Procedure for Evaluation of Turkey Semen

The objective of the present study was to modify the ethidium bromide exclusion procedure in order to detect dead and labile turkey spermatozoa after 24 h storage at 7 C. In Experiment 1, fresh and stored spermatozoa were suspended in phosphate-buffered saline (PBS) ranging in osmolality from 296 to 3 mOsm/kg H2 O, each solution containing the same concentration of the nuclear fluorochrome ethidium bromide. In the 3 mOsm/kg H2 O PBS, nearly all the fresh (98.3%) and stored (96.7%) spermatozoa were stained with ethidium bromide, indicating they were nonviable. Fresh spermatozoa revealed minor variation in the percentage of nonviable spermatozoa in the ethidium bromide exclusion procedure (ethidium bromide in PBS at 296 mOsm/kg H2 O) (20.9%) and the remaining hypotonic PBS solutions (range 20.4 to 18.9%). In the stored semen samples a previously undetected subpopulation of more labile spermatozoa became apparent in hypotonic solutions with osmolalities of 122 and 56 mOsm/kg H2 O. In Experiment 2, hen fertility was determined using fresh and stored semen. All hens were inseminated with 100 × 106 viable spermatozoa. Viability of stored semen was determined either by the original ethidium bromide exclusion procedure or using the sperm-stress test (ethidium bromide in PBS at 56 mOsm/kg H2 O). The observations showed mat adjusting the number of viable spermatozoa inseminated based on the percentage of viable sperm estimated from the sperm-stress test did not improve hen fertility over a 15-wk egg production period.

Protection of broilers against Newcastle disease by hyperimmunisation of the dams

A flock of broiler parents was hyperimmunised against Newcastle disease (ND) by subcutaneous injection of an experimental high-potency inactivated oil emulsion (IOE) vaccine in order to achieve high and long-lasting passive protection in broilers. During the egg production period mean log2 HI ND titre of the parents slowly decreased from 11.6 at 26 weeks of age to 10.0 at 53 weeks of age. Titres of day-old progeny paralleled those of their parents. Mean protection of broilers against mortality following challenge with Herts 33 virus at the ages of 1, 2, 3 and 4 weeks was 86%, 73%, 54% and 44%, respectively. As compared with the current Dutch situation, application of the high-potency IOE vaccine will significantly increase antibody titres in parent flocks and the level and duration of passive protection in broilers. It is concluded that passive ND protection of broilers by hyperimmunisation of the dams is realisable from an economic point of view and is suitable for low-risk areas.

Population dynamics of a thelastomatid nematode of cockroaches

SummaryBlatticola monandros Zervos lives in the hind gut of the endemic New Zealand cockroach Parellipsidion pachycercum Johns. A field survey showed that infection prevalence was high (54 %) in small nymphs and increased further with cockroach size to a maximum (92 %) in penultimate nymphs. Variance to mean ratios and the Chi-square test for goodness of fit of a Poisson distribution provide strong evidence that the distribution of the nematode was not clumped (over-dispersed) or Poisson (random) but under-dispersed in most host size classes. The modal infrapopulation type consisted of 1 adult male and 1 adult female. Other infrapopulations were transitional to this type. Monogamous infrapopulations increased in prevalence with increased host size. Juvenile males were uncommon and probably develop faster into adults than juvenile females. Infrapopulations with 2 juvenile males were very rare and no cockroach contained 2 adult males, although some contained 2 adult females. Seasonal variations in prevalence and infrapopulation structure were slight over a 3 year period, except during one unusually dry summer. During the drought, prevalence of monogamous infrapopulations and of transitional infrapopulations were lowest, while prevalence of single-worm and single-sex infrapopulations were greatest. It is evident that competition between females reduces fecundity. When only 1 adult female nematode is present in an adult cockroach, more eggs are produced than the total produced if 2 adult females are present. Eggs were produced cyclically with short periods of high egg production interspersed with several days of very low or no egg production. Most eggs produced on any one day were attached to the outer surface of only 1 of the up-to-6 faecal pellets produced by the host/day. Mechanisms which may regulate infrapopulations and control reproductive competition and cyclical egg production are discussed. It is suggested that B. monandros regulates its own infrapopulation.

Egg Production of Cage-Housed Turkey Hens from Three Lines Selected for Increased Number of Settable Eggs

Three base populations of turkeys were used to study the influence of selection for increased number of settable eggs produced by hens housed in individual cages on the number of settable eggs and the total number of eggs laid. The base populations were E, previously selected over 12 generations for increased egg production; L, selected over 10 generations for decreased plasma corticosterone in response to cold stress at 4 wk of age; and 1, selected for both increased egg production and increased 16-wk body weight by means of a selection index. In the 2nd to the 8th generations, the selected lines were grown in cages from hatching throughout the egg production period. Females of the selected lines were chosen on the basis of their dams’ performance, whereas males were selected at random within lines. Selected lines were compared with a randombred control population in the base generation and in Generations 5 through 8. Control hens were grown in floor pens in all generations.Selection increased the number of settable eggs, but the gains were small (3.2 to 5.6 eggs/hen per line over a 112-day production period in eight generations) due to low selection intensity (selection differentials averaged 3.4 to 3.7 settable eggs/hen per generation) and low realized heritability (. 10 to .21). Most of the gain in the numbers of settable eggs could be attributed to an increase in the total number of eggs laid.

Effects of Feeding Deoxynivalenol (DON, Vomitoxin)-Contaminated Wheat to Female White Leghorn Chickens from Day Old Through Egg Production

White Leghorn chickens one day of age were fed starter and grower diets containing either a control (noncontaminated) wheat diet or a naturally contaminated deoxynivalenol (DON) wheat diet (18 mg DON/kg) from 1 day of age to the onset of egg production. The hens were then placed on their respective layer diets of control wheat or DON-contaminated wheat (18 mg DON/kg) for six 28-day egg production periods. Feeding the DON-contaminated diet did not significantly influence body weights during the growing or the laying phases. Overall, hen-day egg production and egg weights were significantly higher for hens receiving the DON diet. Feeding DON contaminated wheat caused no significant changes in percent shell, albumen height, percent fertility, percent hatch of fertile eggs, percent hatch of eggs set, or weight of chicks at hatch. There were slight, although significant, changes in shell weight and shell thickness and in some serum chemistry values. There were no significant differences in the hematology parameters measured or in prothrombin times. None of the eggs collected from hens fed the control and the DON-contaminated wheat diet contained detectable quantities of DON. Microscopic examination of sections of the liver, kidney, and proventriculus of control and treated hens revealed no unusual histopathology. The results indicate that feeding DON at relatively high levels beginning at 1 day of age and continuing through six egg production periods had only slight effects on the parameters measured.

Selection for Increased Egg Production Based on Annual Record in Three Strains of White Leghorns.: 1. Comparison of Different Partial Records to Improve Annual Egg Production

Three strains (L3, L5 and L8) of White Leghorns reproduced by random mating in a closed population for over 20 yr were subjected to family selection for annual egg production. The annual egg production period was divided into various part period segments with their corresponding residual egg production records. Combined estimates of heritabilities and genetic correlations were calculated for each segment of the production curve. Relative efficiency of the genetic progress expected in the annual and residual records using part record vis-à-vis complete part record was estimated.For each part period segment heritabilities were the same – whether they were estimated from egg number or from percent production – and showed very high values when estimated from a segment that includes the 21st wk. Heritabilities of the residual records were low for the L3 and moderate for the L5 and L8 strains. Percent production or egg number of the complete part record showed a very high genetic correlation with annual egg production in all strains, a high genetic correlation with residual record in the L8 strain, and a low genetic correlation with residual record in the L3 and L5 strains. A very high annual relative selection efficiency could be obtained by using for selection the percent production of complete part record, but the persistency of layers could be increased by using for selection the percent production of other partial records.

Effect of environment on the intake of food and water, body weight, egg production and plasma concentrations of corticosterone and prolactin in turkey hens.

During the first 4 weeks of egg production, there were no differences in the plasma concentrations of prolactin and corticosterone, egg production, body weight and the consumption of food and water between turkey hens which were maintained in cages or in floor pens. The plasma concentration of prolactin increased to the same extent in both environments during the period of peak egg production. A further rise in concentration of prolactin occurred in association with the termination of oviposition in 15 of the 19 hens which stopped laying eggs. Prolactin appeared to be progonadal and then antigonadal, once a threshold concentration was exceeded. This threshold value was higher in caged turkey hens. After laying ended, high concentrations of prolactin in hens maintained in cages were not maintained in the absence of a stimulus or stimuli associated with the nests.

Bioenergetics of Egg Production by Female House Sparrows

Abstract To determine the daily and total energy expenditures of breeding female House Sparrows (Passer domesticus), we collected 276 females near London, Ontario between April 1981 and May 1983. Protein and fat content of developing follicles, eggs, and oviducts were determined and converted into their energy equivalents. Eight days were required to develop and lay a modal clutch of 4 eggs. Fat energy requirements were not estimable accurately because total body fat did not decline linearly over the egg production period; therefore, energy requirements were estimated as a range. Based on a 4-egg clutch, the maximum daily costs of reproduction, 16.5-17.6 kJ/day, equalled 44-47% of a female's standard metabolic rate. We estimate that daily costs very less than 10% for other clutch sizes (3 or 5). The total energy demand of reproduction was 66-71 kJ. Protein requirements comprised 59-63% of the total costs and were apportioned among oviduct (5-6%), yolk protein (17-19%), and albumen (36-39%). Fat requirements accounted for the remaining 37-41% of total costs. Based on our estimates of energy needed for reproduction, and on other evidence, we suspect that egg production by House Sparrows is not constrained by energy acquisition.