Hatch Weight Research Articles

Characterization of Changes in Yolk Sac and Liver Lipids During Embryonic and Early Posthatch Development of Turkey Poults

In two studies, changes in lipids and fatty acids from the yolk sac and liver of turkeys were determined during incubation and early postnatal growth. In Experiment 1, embryos were collected from Day 13 through 6 d posthatch. Embryos weighed 4.25 g at Day 13, 52.8 g at hatch (Day 28), and 104 g at 6 d. Total yolk lipid (grams per yolk sac) decreased from 9.48 g at Day 13 to 2.52 g at hatch (Day 28). Almost half (47%) of the yolk lipid decreased during the last week of incubation. In Experiment 2, embryos were collected daily from Day 22 through 2 d posthatch. Embryonic weight increased from 32.5 g at Day 22 to 55.8 g at hatch (Day 28), 3 g more than in Experiment 1. On Days 22 and 25, total yolk lipid (grams per yolk sac) was slightly less in Experiment 2 than in Experiment 1, but at hatch (Day 28) there were considerable differences (Experiment 1, 2.52 g; Experiment 2, 0.63 g), concomitant with increased hatch weight in Experiment 2. Liver DM percentage and ether extractable lipid increased as incubation proceeded. Oleic acid comprised the largest proportion of total yolk fatty acids and of liver fatty acids. There was a small but significant increase in yolk sac oleic acid (percentage of total fatty acids) between Day 22 (40%) and hatch (Day 28; 45.4%) and a much larger increase in liver oleic acid (46.6% to 56.5%). The absolute amount of all yolk sac fatty acids declined greatly during the second half of incubation through 6 d posthatch.

Electrocardiographic Evaluation of Broilers During the Onset of Pulmonary Hypertension Initiated by Unilateral Pulmonary Artery Occlusion

Electrocardiography previously has been used as a noninvasive method for detecting cardiac hypertrophy associated with pulmonary hypertension syndrome (PHS, ascites). In the present study, 36 of 100 male broiler chicks were selected for inclusion in the experiment based on their hatch weight (≥ 40 g), Day 1 to 14 BW gain (upper 50% of population distribution), and the normalcy of their Day 14 electrocardiogram (ECG). On Day 16, 10 chicks were assigned to the unoperated control group (CONTROL), sham operations were performed on 10 chicks (SHAM), and pulmonary hypertension was initiated by clamping the left pulmonary artery in 16 chicks (PA-CLAMP). Electrocardiogram leads I, II, III, and aVF were recorded daily until Day 27, when 6 of the 12 birds surviving in the PA-CLAMP group had developed clinical ascites. The right: total ventricular weight ratio (RV:TV) was higher and BW was lower in the PA-CLAMP group than in the CONTROL and SHAM groups on Day 27. The RS, R, and S wave amplitudes in lead II for the CONTROL and SHAM groups did not change, whereas in lead II for the PA-CLAMP group the S wave attained a more negative amplitude by Day 21, the RS wave attained a more negative amplitude by Day 22, and the R wave declined to a less positive amplitude by Day 23 when compared with presurgery values. Similar differences were observed for the RS and S waves for leads III and aVF. The mean electrical axis (MEA) and mean resultant vector (MRV) of the CONTROL and SHAM groups did not change; however the PA-CLAMP group the MEA rotated significantly from +3° to −72° and then to −88° on Days 14, 22, and 27, respectively, and the MRV amplitude increased from 0.052 to 0.108 mV and then to 0.179 mV on Days 14, 22, and 27, respectively. When data from all treatment groups were combined, higher absolute and BW-normalized RV:TV ratios were inversely correlated (r = −0.859 to −0.880) with increasingly negative S wave amplitudes in leads II and aVF. Higher absolute and BW-normalized RV:TV ratios were directly correlated (r = 0.786 to 0.789) with increasing MRV amplitudes. These ECG characteristics constitute accurate, noninvasive predictive criteria suitable for detecting cardiac changes occurring early during the onset of primary pulmonary hypertension.

Artificial incubation, hand-rearing, behavior, and release of common 'Amakihi(Hemignathus virens virens): Surrogate research for restoration of endangered Hawaiian forest birds

In order to test the effectiveness of captive-rearing and release strategies for future restoration of birds in Hawai'i, this pilot study was conducted in forests where introduced avian disease and mammalian predators were present. Methodology used resulted in the first successful hatching of Drepanidinae eggs in an incubator and subsequent hand-rearing of chicks from hatch. Sixteen Common 'Amakihi (Hemignathus virens virens) (mean hatch weight = 1.4 g) were hand-reared. Two different reintroduction strategies were evaluated for small honeycreepers. Known mortality in the wild after release was due to mosquito-transmitted disease (avian malaria and pox). This pilot study shows that the techniques necessary to hatch, rear, and release endangered Hawaiian honeycreepers are available. However, restoration efforts will probably not succeed unless mosquito-free, predator-controlled reintroduction sites are available or strategies are developed to decrease mortality in naive honeycreepers exposed to disease after release. © 1996 Wiley-Liss, Inc.

Heterosis and Overdominance Following Long-Term Selection for Body Weight in Japanese Quail

Although nonadditive genetic variation is more important in crosses among laying stocks than among meat stocks, development of special sire and dam lines to control the release of primary lines results in broilers being the product of three- or four-way crosses. Therefore, nonadditive genetic effects are important in meat stocks because of opportunities to combine stocks that complement each other. Four experiments were conducted to investigate heterosis and overdominance arising from crossing Japanese quail lines originating from the same base population and selected long-term (> 85 generations) for high 4-wk BW under different selection environments. The different selection environments were established by feeding different levels of CP (28 and 20%) and different levels of thiouracil (0 and .2%).Estimates of heterosis were high for hatch of total eggs (>25%) and liveability (12 to 47%), and low for hatch weight (2 to 4%). Overdominance estimates followed similar patterns but were of lower magnitude. Percentage heterosis estimates for BW were high at 1 wk (20 to 30%) and declined linearly to 5 to 10% at 4 wk when quail were fed 28 and 24% CP diets. Contrariwise, when fed low-CP (20%) diets, heterosis values were low initially and remained stable or increased across age. Data obtained from measuring feed intake and feed efficiency indicated that heterosis for BW was closely related to changes in feed intake. Heterosis values for feed intake closely followed those for BW, including the decline across age. Conversely, heterosis appeared to be absent for feed efficiency, except at 1 wk. Similar to heterosis estimates, overdominance estimates were high initially and declined across age and were more clearly demonstrated under the 24 and 28% diets. It was concluded that considerable heterosis is present for BW in Japanese quail following the crossing of lines selected long-term for high BW, but that it is dependent on both environment (diet) and age.

In Ovo Administration of Salmonella enteritidis-Immune Lymphokines Confers Protection to Neonatal Chicks Against Salmonella enteritidis Organ Infectivity

We previously reported that the prophylactic, intraperitoneal administration of supernatants from concanavalin A-stimulated T cells derived from Salmonella enteritidis (SE)-immune White Leghorn hens (i.e., SE immune lymphokines or ILK), conferred protection to neonatal White Leghorn chicks against SE organ invasion. In the present study, we evaluated the effects of in ovo administration of ILK on hatchability, hatch weight, in vitro bactericidal activity of heterophils, and protection against SE organ invasion in neonatal White Leghorn chicks. On Day 18 of embryogenesis, injections were made into the amnion with either ILK or nonimmune ILK (NILK) or were not injected (untreated). On the day of hatch, whole blood was collected from 20 of the chicks per treatment group for heterophil isolation. All remaining chicks were orally challenged with 5 × 104 cfu SE. Twenty-four hours after SE challenge, organs (liver and spleen) from the chicks were cultured for SE. Hatchability of ILK- and NILK-treated chicks was not different from that of untreated chicks. Hatch weights of ILK-treated chicks were approximately 1 g less (P < .05) than that of NILK-treated or untreated chicks. In vitro bactericidal activity of peripheral blood heterophils derived from ILK-treated chicks was increased (P < .05) above activity from heterophils derived from NILK-treated or untreated chicks. Organ invasion with SE was markedly and significantly decreased in the ILK-treated chicks as compared with chicks treated with NILK or untreated chicks. These results suggest that in ovo administration of ILK confers protection to neonatal chicks against SE organ infectivity at hatch.

Ultrasonography as a Tool for Monitoring In Ovo Chicken Development. 2. Effects of Eggshell Alteration and Ultrasonography on Embryonic and Posthatch Development ,

The influence of creating and closing acoustic windows on embryonic and posthatch development for the purpose of chicken embryogenesis monitoring by real-time ultrasonography (US) was evaluated at 2, 6, 9, 14, and 17 days of incubation. Acoustic windows were closed using either a porous dialysis film and tape (FM) or an eggshell allograft attached with collodion (CP). Results from eggs closed in each manner with and without concurrent nonsterile US examination were compared with two control groups. Window creation reduced hatchability. The hatchability reduction was caused primarily by bacterial contamination. Contamination was more common in the FM eggs than in the CP eggs and was greater in eggs that also underwent US. Hatchability increased and contamination decreased when US was performed closer to hatch. Egg weight loss was increased after Day 6 of incubation in FM + US eggs treated on Day 2 and after Day 9 in all eggs with windows except CP eggs treated on Day 9 and CP + US eggs treated on Days 6 and 9. Hatch weight decreased in chicks from eggs that had windows, particularly in FM eggs.

Divergent Selection for Growth in Japanese Quail Under Split and Complete Nutritional Environments.: 7. Heterosis and Combining Ability Among Diallel Crosses Following Twenty-Seven Generations of Selection

Growth patterns of quail lines divergently selected for 4-wk BW under split and complete nutrition environments were investigated utilizing a diallel mating scheme. The design, involving 16 mating combinations, allowed investigation of heterotic effects, reciprocal cross effects, and combining ability. Progeny from Generation 27 breeders were evaluated in two hatches under both selection diets. Heterosis for hatch weight was essentially zero; however, percentage heterosis from High × High crosses and Low × Low crosses ranged from 5 to 18% after 1 wk of age. Quail progeny from Low × High crosses were consistently larger than quail from reciprocal High × Low crosses under both selection diets. Reciprocal differences were greatest immediately posthatch and declined with age. However, in crosses involving males from High and Low split diet lines mated to females from High and Low complete diet lines, large reciprocal differences in BW remained at 8 wk. Mean heterosis values for BW across ages from crossing High and Low lines both within and across selection environments were negative in six of eight comparisons. Mean values ranged from +3 to −11% and indicated that greater selection responses may have been made in divergent selection for low 4-wk BW than for high BW. General combining ability of lines was greater when transmitted via females as opposed to males, and was similar under the two diets (split and complete). There was evidence that high-BW lines exhibited greater general combining ability under both dietary environments than did low-BW lines.

Divergent Selection for Exponential Growth Rate at Fourteen or Forty-Two Days of Age.: 1. Early Responses

Athens-Canadian randombred chickens were divergently selected for exponential growth rate (EGR) to 14 or 42 days of age, resulting in four unique populations: 14L, 14H, 42L, and 42H. Exponential growth rate was calculated as: EGR = [ln b – ln a] ÷ t; where a = hatching weight; b = weight at age of selection; and t = age of selection. In the S4 generation, 14H chicks had significantly greater EGR than 42H chicks at 14 but not 42 days. Chicks from the 42H line had significantly greater EGR than 14H chicks from 14 to 42 days. This meant that 14H chicks were significantly heavier than 42H chicks at 14 but not 42 days. Indeed, 14H chicks were consistently 5 to 10% heavier than the 42H chicks in each generation. Selection for EGR at 14 days was at least as effective in altering 42-day body weight as selection for growth rate at that age during the early generations of selection.Evidence of asymmetry existed for selection for EGR at 14 but not 42 days. Realized heritability of fast EGR14 was .29 ± .08 (SE) whereas that of fast EGR42 was .15 ± .09. Genetic correlation between fast EGR14 and fast EGR42 was 1.45, whereas the converse genetic correlation was .67. This would suggest that all the genes that influence 14-day growth influence 42-day growth, but not vice versa.Growth curve analysis supported the general hypothesis of growth, in that instantaneous growth rate was fastest in the 14H line, as was the decay of growth. Indeed, 14H birds were smaller at and beyond sexual maturity than 42H chickens.

Phenotypic, Embryonic, and Neonatal Effects of a Gene for Sex-Linked Imperfect Albinism (Sal-s) in Chickens

Gross phenotypic observations, histology, and tissue culture showed that the gene for sex-linked imperfect albinism that occurred at the University of Saskatchewan (Sal-s) allows a small amount of melanin pigment to be deposited in eyes and feathers. Melanin pigment accumulates in retinal pigment epithelial and cultured neural crest cells, but neural crest cells pigmenting the feathers transfer their pigment as it is produced, and this is seen as a constant amount of color in successive generations of feathers. Despite differences from early reports, it would appear that the phenotype produced by Sal-s is essentially the same as that produced by other Sal mutations. Albinos have a high incidence of lesions in the regions of the navel, the hocks, and the nares, similar to those associated with other hypomelanic mutations in the chicken. Yolk contents appear to be used more slowly by albinos late in incubation. The increased size of the yolk sacs probably contributes directly to producing the navel lesions and indirectly to variation in hatch weight. Albinos have small bursae of Fabricius, reduced hatchability, and early growth.

Relationships between egg size, chick size at hatching, and chick survival in the Whimbrel Numenius phaeopus

The relationships between egg size, chick size at hatching and chick survival in Whimbrels Numenius phaeopus were studied over a three‐year period in the Shetland Isles. Three measurements of chick size at hatching were all positively correlated with egg volume, though the relationship was strongest with hatchling body‐weight. In two of the three years the proportion of chicks from a brood which survived to fledging increased significantly with the mean hatching weight of chicks in the brood. Within broods, a significant effect of hatching weight on survival was detectable only up to 7 days after hatching. Between years the egg volumes and hatchling weights of individual female Whimbrels showed relatively little variability, indicating that these attributes could be controlled to a large extent by inheritance.

Relationship between the weight of hatching eggs and subsequent early performance of broiler chicks

1. The effect of egg weight on the subsequent performance of individual growing chicks was studied. Eggs from commercial broiler breeder hens were collected at 52, 55 and 57 weeks of age and incubated. The chicks were reared for 18 d. 2. Egg weight and hatched chick weight were not affected by the age of the hens during the 52 to 57-week period, but there was a close correlation between egg weight and hatching weight, irrespective of the age of the hens (r = 0.89). Chick:egg weight ratio at hatching was about 0.71 and independent of hen age. One d after hatching, chick weights had decreased by about 1.5 g. 3. The initial high correlation between egg weight and chick weight decreased markedly during post-hatching growth, becoming insignificant 5 d after hatching. At 18 d of age, however, chicks from eggs of older hens tended to be heavier than those from younger birds. The greater 18-d weights appeared to be associated more with higher food intake during that period, than with greater egg weight. 4. It was concluded that, in individual broiler chicks, the advantage of the initially higher weight attributable to a larger egg diminishes rapidly after hatching, and the main factor affecting final body weight is food intake.

Comparison of Growth Curves of Weight Selected Populations of Turkeys, Quail, and Chickens

The pattern of growth from hatch to sexual maturity was measured in quail, chicken, and turkey females using the Gompertz equation. Quails and chickens were selected for high or low immature BW and turkeys were selected for high BW. Quail and turkey species also included their respective randombred control populations. The chicken species included an F2 of the selected lines. Thus, there were considerable differences in BW not only among species but between lines within species. Differences were evident at hatch as hatch weights relative to asymptotic BW were greater for quail than chickens and turkeys. Age and BW traits associated with point of inflection (POI) were variable. Species differences appeared to be influenced by the selection scheme applied to the populations. Slope at POI was greatest in quail and the same for turkeys and chickens. Age at 90% of the asymptotic BW was generally greatest for chickens, intermediate for turkeys and lowest for quails. Selection age in relation to age at POI may contribute to the timing and magnitude of growth response observed.

Pattern of Growth and Plasma Growth Hormone Secretion in Turkeys Selected for Increased Egg Production

Male and female turkeys of a slow-growing line selected for increased 180-day egg production (Line E) and its faster growing randombred control (RBC1) were sampled weekly for BW and plasma growth hormone (GH) content Hatching weights were higher for RBC1 than Line E poults, but no difference was observed between sexes. The pattern of growth of the two lines, as described by the Gompertz equation, was different in magnitude of growth [BW at point of inflection (POI) and asymptote] but not in form (slope and age at POI and age at asymptote). Males achieved higher weights at POI and asymptote but took longer to reach these weights. Slope at POI was greater for females than formales. Plasma GH was higher in Line E than in RBC1 at hatching but higher in RBC1 than in Line E from Weeks 7 to 28. Males had higher concentrations of circulating plasma GH than females at all ages. The GH pool size was maximal at 5 wk for females and 10 wk for males. Maximal concentrations of circulating GH preceded maximal GH pool size by several weeks.

Effect of Incubation Dry-Bulb and Wet-Bulb Temperatures on Time of Hatch and Chick Weight at Hatch

In two experiments, broiler hatching eggs were incubated under conditions that permitted comparison of dry-bulb (DB) and wet-bulb (WB) temperatures. The experiment covered both the setter (1 to 17 days) and hatcher (18 to 21.5 days) phases.In Experiment 1, DB temperatures of 37.2 and 37.5 C and WB temperatures of 28.3 and 30.0 C from 1 to 21.5 days were compared in a 2 by 2 factorial design that extended through both the setter and hatcher phases. Overall, chicks hatched earlier under the higher of the DB conditions and the lower of the WB conditions. There was a significant DB by WB interaction, attributed to the early hatching effect of a lower WB temperature being more pronounced at the higher DB temperature. Increased chick weight was recorded at the higher WB temperature.In Experiment 2, the DB temperature in the setter phase (D1) and the hatcher phase (D2) as well as the WB temperature in the setter phase (W1) and hatcher phase (W2) at the same levels as in Experiment 1 were compared in a 2 by 2 by 2 by 2 factorial design. Time of hatch was decreased by the high Dl temperature, but no other main effect was observed.Regression analysis showed interactions of Dl by D2, Dl by W1, Dl by W2, and W1 by D2 for the intercept as well as for the linear and quadratic components of the response. The W1 by W2 interaction was significant for the intercept and for the linear component. The D2 by W2 interaction was significant for the intercept only. These interactions were interpreted to be caused by the relative effects of DB temperature on rate of metabolic water production and the water-vapor pressure within the egg as well as by the effect of WB temperature on the moisture and concentration gradient between the egg and incubator.Chick weight at time of hatch was affected by the time of removal from the incubator. Chick weight was also directly related to time of hatch and to the holding time within the incubator.

Influence of incubation temperature on Oreochromis niloticus (L.) eggs and fry : II. Survival, growth and feeding of fry developing solely on their yolk reserves

The consequence of constant water temperature of 17, 20, 24, 28, 30 and 34.5°C on the survival, growth and first feeding capabilities of O. niloticus hatchlings developing solely on their yolk reserves were investigated. The survival times (ST 50) of fry were temperature-dependent and ranged from 2.5 days post-hatching at 34.5 to 18.5 days at 20°C. With the exception of 20 and 34.5°C, mass mortality of fry coincided with the onset of yolk exhaustion. The mean upper and lower median tolerance limits (with 95% confidence limits) from hatching to first feeding stage were 32.1°C (31.9–32.2°C) and 21.8°C (21.4–22.3°C), respectively. Optimal survival to first feeding (>90%) during this period occurred at 28–30°C. Incubation temperature influenced the weight of the body and yolk reserves of emergent fry; fry hatching with a lower mean dry body weight contained greater yolk reserves. Maximum mean body weight and minimum mean yolk weight of emergent fry occurred at 30°C. The growth rate (SGR, %/day) of fry was temperature-dependent. Maximum growth rate occurred between days 3 and 6 at 28 and 30°C and maximum body weights were attained by 18, 9 and 6 days at 24, 28 and 30°C, respectively. The gross yolk utilization efficiency between hatching and maximum dry body weight was temperature-dependent between 24 and 30°C and ranged between 55.4% and 61.7%. At higher rearing temperatures feeding commenced earlier. Onset of feeding and point-of-no-return occurred at 8, 5 and 4 days and 23, 20 and 18 days, respectively, at 24, 28 and 30°C.

Effect of Dry-Bulb Temperature, Relative Humidity, and Eggshell Conductance During the First Three Days of Incubation on Egg Weight Loss and Chick Weight

Broiler hatching eggs of similar weight were randomly divided into three groups. The first group of eggs served as the control, the second group was washed in sodium hypochlorite to disrupt the cuticle, the third group was dipped partially in a colloid solution to seal the pores in the pointed region of the eggshell. These treatments altered eggshell conductance, measured as milligrams of water loss per day per torr, from Day 2 to Day 3 of incubation. Eggs from all three groups were randomly placed in incubators operating at a dry-bulb (DB) temperature of 36.7, 37.2, or 37.8 C and at a relative humidity (RH) of 59% (Experiment 1), or at an RH of 51, 59, or 67% at a DB temperature of 37.2 C (Experiment 2) for the first 3 days of incubation. At the end of Day 3 of incubation, all eggs were transferred into an incubator operating at a DB temperature of 37.2 C and at 59% RH for the remainder of the incubation period. Individual egg weights were recorded on Days 1, 2, 3, and 18, and at external pipping. Chick weight at hatch and eggshell weight were also recorded.The incubating DB temperature had no effect on egg weight loss from Day 0 of incubation to external pipping. However, a DB temperature of 37.8 C produced significantly heavier chicks at hatch, when the chick weight at hatch was expressed as a percentage of initial egg weight. A relative humidity of 51% resulted in the greatest weight loss from Day 0 to Day 1 and from Day 2 to Day 3 of incubation, and the least weight loss from Day 1 to Day 2 of incubation. Eggs treated with colloid and chlorine lost significantly more weight from Day 0 to Day 1 of incubation; however, the colloid-treated eggs lost significantly less weight from Day 2 of incubation to external pipping. The colloid-treated eggs produced heavier chicks at hatch.

The Effects of Parent Age and Posthatch Treatment on Broiler Performance

The relationship between age of the parent and the quality of the day-old broiler chick were studied in two experiments by examining the loss in egg weight during incubation (percentage of egg weight loss, PEWL). Also, the efficacy of a water-soluble antibiotic and the practice of withholding feed at placement time were examined. Eggs were obtained from two sets of breeders (approximately 30 and 50 wk of age). The eggs were weighed individually and were incubated. Chicks of each parent age group were randomly assigned to one of four treatments: 1) water and feed at placement time; 2) water and Neo-Terramycin and feed at placement time; 3) water at placement time and feed 4 h later; and 4) water and Neo-Terramycin at placement time and feed 4 h later. The chicks were housed in cages for Experiment 1 and in floor pens for Experiment 2.In both experiments, breeder age significantly affected BW. Chicks from old flocks were heavier and exhibited a significantly higher growth rate than the chicks from young flocks. Significant correlations between chick hatch weight and egg weight were observed. Low correlations between PEWL and BW were noted. In Experiment 1, the chicks receiving the Neo-Terramycin were significantly heavier up to 4 days of age than the chicks in other treatments. Chicks allowed access to feed at placement time were significantly heavier at most weigh times, up to 5 wk of age. Male chicks from old flocks that received both Neo-Terramycin and feed at the time of placement had a significantly higher growth rate than did the males of any other treatment in Experiment 1. In Experiment 2, neither the administration of Neo-Terramycin nor the provision of water prior to feeding had a significant effect on BW gain. Male chicks from the young flocks provided with water prior to feed exhibited a significantly higher growth rate than did the males in any other treatment. These data suggest that parent age does influence chick weight. The use of water-soluble antibiotics and the provision of water prior to feed did not benefit chicks that are normally hydrated.

Recruitment and Summer Diapause in the Dynamics of a Population of Nebria brevicollis (Coleoptera: Carabidae)

We studied the population dynamics of the carabid Nebria brevicollis (F.) by conducting a capture-recapture experiment between 1968 and 1978. We used 30 pitfalls, emptied (almost) daily and marked individually 11521 beetles. A part of the experimental area was fenced in 1976 and 1977 (about 360 m2). We used key-factor analysis to analyze the life cycle of this beetle. Density fluctuated heavily in the population investigated. The species is almost completely semelparous; on average only 1.3% of the old beetles reproduced again in following years. The most important factors influencing variation in population size are the number of eggs laid and the survival of the preadult stages. It is not yet possible to decide which of these varies most in the field. There is an indication that a negative correlation exists between recruitment and number of parent females, but this could also be related to differential survival of larvae. Larval mortality is highly affected by the amount and quality of food as well as by predation and parasitism. Previous research suggests that in our area conditions during larval development are suboptimal. Larval mortality appears to vary within a much wider range than egg production. Therefore, we consider variation in survival of the preadult stages as more influential. Young beetles need to increase their hatching weight by 50-60% before entering summer diapause. Although on average one third of these beetles died before or during summer diapause, this could not be considered to be a key-factor. Young adults were more mobile than reproducing beetles, often leaving the hatching site. The pattern of catchability of marked beetles deviated from the expected Poisson distribution. Too many beetles were either caught only once or four or more times. This might explain why estimations of population sizes according to Jolly were lower than the number of beetles actually marked. Calculations based on models of Craig yielded a better fit. His second model rightly predicted population size when the area was fenced off. In our area N. brevicollis is widespread and often abundantly present. In our opinion the success of N. brevicollis is presumably based on high mobility of (young) adults, which favours reaching new suitable sites, together with plasticity in developmental mode of the larvae, which enables them to make the best of an ever changing food situation, and which influences both the quality and quantity of adults.

Genetic study of Dandarawy chickens: I. Heritabilities and genetic correlations of body weight and weight gain

Summary — Heritability values of body weight and weight gain at the ages of 1 d, and 4, 8, 12, and 16 wk were estimated from 57 half-sib families of a strain of the Egyptian breed Dandarawy representing 57 sires, 256 dams, and 1,605 offspring. Estimates were obtained for both of the sexes separately as well as for the two combined. The estimates of heritability ranged from 0.24 to 0.60 for males and females from sire components of variance, and 0.03 to 0.37 for males and females from dam components of variance. There were marked differences between heritability estimates from sire and dam components of variance and between males and females. The heritability estimates from sire components were generally higher than those from dam components, which indicated the importance of the additive genetic effect and possible sex-linked effects. It was also noticed that the environment had an effect on both body weight and weight gain which is reflected in heritability estimates from one age to another. The results showed that there were highly significant correlations between body weights from 4 to 16 wk of age. There were no correlations between hatch weight and weights at the other ages. This indicates that it is possible to consider the hatch weight as a trait completely separate from the other traits in males, females, and the sexes combined. The highly significant genetic and environmental correlations showed that both genetic and environmental factors had the same influences on body weight from 4 to 16 wk of age. There were absent estimates of the genetic correlations especially with the dam components of variance in males and females. The correlations between weight gains at different periods showed highly significant estimates up to 12 wk of age. These correlations reflect the importance of both genetic and environmental effects on weight gain at the different periods. Our results indicate that it is possible to select for body weight and weight gain at an early rather than a late (16 wk) age because of the high correlations between the different ages.

Relationships among egg size, energy reserves, growth rate, and fasting resistance of Canada Goose goslings from southern Ontario

Eggs of wild giant Canada Geese (Branta canadensis maxima) breeding in southern Ontario were collected and incubated artificially. Components of the total nutrient reserve of goslings were measured at hatch to test whether relationships existed between egg size, gosling weight, and weight of reserves in goslings. The growth rate of fed goslings of different weights at hatch was measured for 25 days. The nutrient reserves remaining in goslings of different hatch weights were measured after 2, 4, and 6 days of starvation. Egg size and gosling weight were not highly correlated in this population (r = 0.63). Larger goslings generally contained more reserves than small goslings (P &lt; 0.05), but much variability occurred in this relationship. Gain in weight over 25 days was not related to the weight at hatch. Starved goslings with higher body fat levels had significantly higher dry carcass weights than goslings with low body fat levels (P &lt; 0.01), suggesting a sparing action of fat on body tissues. The apparent survival of small goslings and goslings with small reserves, combined with the great variability in egg size, gosling weight, and extent of metabolic reserves, suggests relaxed selection in the southern Ontario environment where this population breeds.