The Hen's egg: Factors affecting the shearing strength of shell material     

T. C. Carter 《British poultry science》1970,11(4):433-449

Experiments are described from which it is concluded that

1. the force required to shear egg shell material can be measured with high precision by pressing a narrow, flat‐ended plunger on to the shell;

2. shearing force falls and the precision of its measurement rises as the radius of the plunger is reduced;

3. shearing force is related linearly to shell thickness ;

4. the regression line of shearing force on shell thickness does not pass through the origin but has a substantial positive intercept on the thickness axis, at about a third of the mean thickness ;

5. there are differences between hens and between strains of hen in the magnitude of the intercept, but not in the slope of the regression;

6. shearing force is affected also by the glossiness of the shell;

7. shearing force was not significantly affected by stripped membrane thickness, number of mammillae per unit area of shell, shell organic content (standardised for shell thickness), shell curvature, shell colour, mottling score, translucent patch score, speckling score, age of the egg or age of the hen that laid it;

8. measured with a plunger of radius 165 μm, the mean shearing strength of incremental shell was 57 kg wt/mm² (3–7 ton/in²).

The findings suggest that the shearing strength of egg shells might be increased by direct selection and by selection for shell glossiness.  相似文献   

The hen's egg: Shell cracking at oviposition in battery cages and its inheritance     

T. C. Carter 《British poultry science》1971,12(2):259-278

It is known that there is much variation between individual hens and between strains of hen in (a) the incidence of egg‐shell cracking and (b) the height through which the egg is dropped at oviposition. Pilot experiments are described from which it is concluded that:

1. most cracks that occur in a battery cage are produced when the egg drops on to the floor at oviposition;

2. they are located predominantly in the two polar thirds of the shell;

3. their incidence is determined mainly by the effective mass of the cage floor, the mean drop height and the mean attitude of the eggs at emergence from the cloaca (broad or narrowpole first) ;it is affected only slightly by the mean shell thickness and the overall mean shell curvature (egg size);

4. if a hen is kept on a floor with a high effective mass, an indirect estimate of her mean drop height can be obtained quickly, easily and with high precision from observations made on her eggs after they have been laid; the observations required are the incidence of eggs with poorly formed shells, the type, location and incidence of cracks in eggs with well‐formed shells and the mean weight of the eggs;

5. the incidence of cracking on a heavy cage floor can be used to predict the incidence on a normal floor;

6. the incidence of cracking is heritable and responds rapidly to downward selection.

It is suggested that breeders should test the technique described, with a view to adopting it as a method of selecting for low crack incidence.  相似文献   

Estimation of genetic parameters related to eggshell strength using random regression models     

J. Guo  M. Ma  L. Qu  M. Shen  T. Dou 《British poultry science》2015,56(6):645-650

1. This study examined the changes in eggshell strength and the genetic parameters related to this trait throughout a hen’s laying life using random regression.

2. The data were collected from a crossbred population between 2011 and 2014, where the eggshell strength was determined repeatedly for 2260 hens.

3. Using random regression models (RRMs), several Legendre polynomials were employed to estimate the fixed, direct genetic and permanent environment effects. The residual effects were treated as independently distributed with heterogeneous variance for each test week.

4. The direct genetic variance was included with second-order Legendre polynomials and the permanent environment with third-order Legendre polynomials.

5. The heritability of eggshell strength ranged from 0.26 to 0.43, the repeatability ranged between 0.47 and 0.69, and the estimated genetic correlations between test weeks was high at > 0.67.

6. The first eigenvalue of the genetic covariance matrix accounted for about 97% of the sum of all the eigenvalues.

7. The flexibility and statistical power of RRM suggest that this model could be an effective method to improve eggshell quality and to reduce losses due to cracked eggs in a breeding plan.

  相似文献   

Some factors affecting the incidence of cracks in hens’ egg shells     

G. B. Anderson  T. C. Carter  R. Morley Jones 《British poultry science》1970,11(1):103-116

Six blocks of data are analysed: British Egg Marketing Board (BEMB) data on second quality eggs‐in‐shell in packing station throughput; shell thickness and colour data on 1,440 eggs sampled in 4 packing stations; crack incidence data on 162,480 individually recorded eggs from a two‐strain experimental flock kept in battery cages; similar data on 34,611 eggs from another experimental flock; shell thickness, volume and shape data on 76 eggs from 19 pairs of hens, one of each pair with a high and one with a low shell‐crack record; and BEMB data on the prevalence of battery and deep‐litter husbandry. Conclusions reached are:

1. Over the last decade there has been a rise in the incidence of packing‐station egg downgrading in the United Kingdom; it is assumed to have been due largely to a rise in the incidence of cracked shells.

2. The rise in crack incidence was probably not due primarily to deterioration in shell strength associated with high production rates or white shell colour; such associations were looked for but not found.

3. It was probably due primarily to an increase in “ environmental insults “ to packing‐station eggs accompanying the spread of deep‐litter and battery husbandry; a close association was found between their incidence and that of downgrading.

Implications for cage designers, breeders, egg producers and research workers are discussed.  相似文献   

Effect of dietary supplementation of thymol,synbiotic and their combination on performance,egg quality and serum metabolic profile of Hy-Line Brown hens     

A.A.A. Abdel-Wareth 《British poultry science》2016,57(1):114-122

1. An experiment was conducted to determine the effects of dietary supplementation of thymol, synbiotic (Biomin, IMBO) and their combination in laying hen diets on laying performance, egg quality and serum metabolic profile from 24 to 36 weeks of age.

2. Treatment groups were fed on a control diet, the control diet supplemented with thymol (250 mg/kg), the control diet supplemented with synbiotic (250 mg/kg) or the control diet supplemented with a combination of thymol (250 mg/kg) and synbiotic (250 mg/kg).

3. Supplementation of thymol and synbiotic, separately as well as combined, improved egg weight, egg production, egg mass and feed conversion ratio from 24 to 36 weeks of age. The eggs obtained from thymol, synbiotic or their combination treatments displayed higher values of shell thickness, Haugh unit and shell percentage compared to the control.

4. Serum cholesterol significantly decreased in the single or combined form of thymol and synbiotic supplementation treatments.

  相似文献   

The hen's egg: Some factors affecting deformation in statically loaded shells     

T. C. Carter 《British poultry science》1970,11(1):15-38

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Effect of dietary inclusion of toasted guar (Cyamopsis tetragonoloba) meal as a source of protein on performance of White Leghorn layers     

S.V. Rama Rao  M.V.L.N. Raju  B. Prakash  E. Pradeep Kumar Reddy  A.K. Panda 《British poultry science》2015,56(6):733-739

1. Two experiments were conducted to study the effect of including toasted (120°C/35 min) guar meal (GM, Cyamopsis tetragonoloba) in the diet on performance and egg shell quality of White Leghorn (WL) layers.

2. Totals of 2376 and 2816 layer chickens (Babcock, BV 300) were randomly distributed into 27 and 32 replicates with 88 birds each in Experiments 1 and 2, respectively. Three diets in Experiment 1 (0, 50 and 100 g GM) and 4 diets in Experiment 2 (0, 50, 100 and 150 g GM/kg) were prepared having similar concentrations of energy and protein. Each diet was fed ad libitum to 9 and 8 replicates, respectively, in Experiments 1 (from 53 to 68 weeks) and 2 (35 to 46 weeks of age).

3. Compared to soya bean meal (SBM) GM contained similar concentrations of protein, but was deficient in all essential amino acids except arginine, which was 70% higher than in SBM. Total non-starch polysaccharide (NSP) content in GM (166 g/kg) was lower than that of SBM (179 g/kg). Amongst different NSP fractions, GM contained higher levels of arabans, xylans, mannans and glucans compared to SBM. The galactomannan gum content in GM was 46 g/kg.

4. Egg production (EP), body weight (BW), food intake (FI), food efficiency (FE) and egg quality (shell weight, shell per cent, shell thickness, Haugh unit score, egg density and egg breaking strength) parameters were not affected by incorporating GM up to 100 g/kg diet in Experiment 1. However, egg weight (EW) and egg mass (EM) were reduced significantly in groups fed on 100 g/kg diet.

5. In Experiment 2, EP and FE were not affected by incorporating GM up to 100 g/kg, but were reduced at 150 g/kg diet. FI, EW, BW and egg quality parameters were not affected by incorporating toasted GM up to 150 g/kg diet.

6. Based on the results of both experiments, it is concluded that toasted GM can be included in WL layer diets up to 100 g/kg without affecting EP, FE, EW, EM, Haugh unit score, BW and egg shell quality parameters.

  相似文献   

Studies on egg shell strength,shell stiffness,shell quantity,egg size and shape     

M. A. Tung  L. M. Staley  J. F. Richards 《British poultry science》1968,9(3):221-229

Physical properties which included shell stiffness, egg weight, width and length, shell weight and thickness, percentage shell, shell weight per unit area, shape index and roundness were studied in relation to maximum force and energy absorbed at failure in 2733 eggs produced by sixty SCWL pullets. Pooled‐egg, bird‐average and individual‐bird bases were used for correlation and regression analyses.

All physical properties in combination accounted for 61.9 and 88.2 per cent of the variation in force and 19.6 and 59.5 per cent of energy absorbed at failure in pooled‐egg and bird‐average analyses respectively. The non‐destructive measurements of shell stiffness, egg size and shape gave R ² values of 60.5 and 86.9 per cent with force and 16.2 and 55.0 per cent with energy in corresponding analyses.

Shell stiffness proved to be the most important predictor of force at failure. Analyses in which variation of shell stiffness was explained by other physical properties supported the conclusion based on theories of elasticity applied to shell structures that shell stiffness was largely an indirect measurement of egg shell quantity together with lesser effects of egg size and shape.

Bird‐to‐bird variation in relations between physical properties and shell strength was evident from individual bird analyses. Coefficients of determination from force at failure regressed on shell stiffness had a mean value of 0.455 with a standard deviation of 0.178 (n = 60).  相似文献   

The correlation between height of thick albumen,yolk diameter,shape index and the position of the yolk after storage     

W. F. Van Tijen 《British poultry science》1972,13(1):1-6

From about 100 White Leghorn hens the following characteristics were determined on samples of four eggs per hen:

1. The shift of the yolk during a storage period of 7 d at a temperature of 20 °G

2. The height of the thick albumen directly after lay, and at the end of the storage period

3. The diameter of the yolk

4. The shape index of the egg.

The correlation, on a hen basis, between the shift of the yolk and the other above‐mentioned traits was only of very minor importance. This means that one of the arguments on the basis of which the height of the thick albumen was used as a criterion for the internal quality of eggs—the influence of the thick white on the central position of the yolk—has lost much of its significance.

In addition the same measurements were made on eggs from 12 entries at the Random Sample Testing Station at Putten. Here samples of 20 eggs per entry were taken. Contrary to expectation the combination of a large amount of thick albumen and a large shift of the yolk proved to be the rule rather than the exception.  相似文献   

Post-mortem proteolysis and tenderisation are more rapid and extensive in female duck breast muscle     

C.-C. Liao  Y.-S. Chang  S.-Y. Yang 《British poultry science》2016,57(6):734-739

1. The post-mortem proteolysis and tenderisation between male and female duck breast muscles were compared.

2. The results showed that μ-calpain activity, desmin content and shear force decreased more quickly in female than in male samples stored at 5°C.

3. It is suggested that the post-mortem proteolysis and tenderisation are more rapid and extensive in female duck breast muscle.

  相似文献   

Changes in eggshell structure and predisposition of broilers to health problems: is there a common pathophysiology?     

A.A. Olkowski  S. Nain  B. Laarveld  C. Wojnarowicz 《British poultry science》2015,56(2):267-274

1. A study of broiler breeder eggs differing in eggshell matrix optical density was conducted to determine the association of eggshell structural quality and the risk of disease in broilers.

2. A total of 10 000 eggs from a broiler breeder flock were examined according to the pre-established criteria, and allocated to groups classified as having a high or low density shell matrix.

3. The eggs from respective groups were incubated and hatched in a commercial hatchery. Samples of unhatched eggs from each group were subjected to detailed examination to establish the cause of reproductive failure. First, quality chicks from each group were raised as separate flocks in a commercial broiler barn. Group performance, morbidity, and mortality were monitored throughout the growth period. All birds were processed in a commercial plant, and condemnation data were compiled.

4. There were significantly more unhatched eggs, and fewer quality chicks in the group classified as having a low density eggshell matrix, in comparison to the high-density group.

5. Embryo pathology accounted for a large proportion of the overall reproductive failure in both groups, with a large proportion of embryos showing anatomical anomalies. The eggs and embryos from the low-density eggshell matrix group were three times more likely to be infected.

6. Significantly higher production losses associated with mortality/morbidity, and condemnations of carcasses at processing were observed in broilers from the low-density eggshell group compared with the high-density eggshell group.

7. It is concluded that common metabolic/physiological changes in breeder hens associated with eggshell pathology may be also risk factors linked with predisposition of broiler chicks to some health problems.

  相似文献   

The hen's egg: Prediction and reduction of downgrading in large producer groups     

T. C. Carter 《British poultry science》1971,12(3):379-385

British Egg Marketing Board data on the incidence of downgrading in eggs received at packing stations during the second week in each month from April 1960 to March 1968 have been analysed in relation to:

1. the incidence of free‐range, deep‐litter and battery husbandry in flocks from which they came, as estimated by interpolation from annual census data;

2. season, as represented by fundamental and first‐harmonic sine and cosine terms;

3. age‐structure of the flocks, as indicated by the incidence of extra‐small eggs 10 months earlier;

4. time;

5. packing‐station throughput.

It is shown that 93–3 per cent of the variance of downgrading percentage is associated with variation in (i), (ii) and (iii). After these effects had been taken into account there was no significant long‐term time‐trend but there were small effects associated with certain years. There was no significant effect of (v). The regression equation was used to predict the incidence of downgrading in the second week of each month from April 1968 to January 1969; this it did accurately except in May and June 1968, when the downgrading percentage fluctuated to an unprecedented degree following a very cold and a very hot spell of weather.

It is suggested that large producer‐packer groups should systematically collect information on the incidence of downgrading and the percentages of birds of each strain and age‐group, of cages of each type, of nutritional regimes and of egg‐collection methods; and that these data should be analysed to yield (a) forecasts of downgrading incidence and (b) estimates of the effect of each strain, cage‐type, etc. on downgrading incidence, for use when deciding replacement policy.  相似文献   

Dietary supplementation with sodium bicarbonate improves calcium absorption and eggshell quality of laying hens during peak production     

M.J. Jiang  J.P. Zhao  H.C. Jiao  X.J. Wang  Q. Zhang 《British poultry science》2015,56(6):740-747

1. The advantage of supplemental sodium bicarbonate (NaHCO₃) on eggshell quality in laying hens changes with age. Besides increasing calcium (Ca) secretion in the eggshell gland, it may improve Ca absorption in the intestine or kidney.

2. Hy-Line Brown layers (n = 384), 25 weeks of age, were allocated to two treatment groups in two experiments, each of which included 4 replicates of 24 hens. Hens were fed a basal diet (control) or the basal diet containing 3 g NaHCO₃ g/kg for 50 or 20 weeks in Experiment 1 or 2, respectively. A 24-h continuous lighting regimen was used to allow hens to consume the dietary supplements during the period of active eggshell formation.

3. In Experiment 1, particularly from 25 to 50 weeks of age, and in Experiment 2, NaHCO₃ supplementation favoured hen-d egg production at the expense of lower egg weight. The increased eggshell thickness should have nothing to do with the additional eggshell formation, because of the unchanged egg mass and daily eggshell calcification.

4. At 35 weeks of age in both experiments, NaHCO₃ supplementation increased duodenal expression of calbindin-d28k (CaBP-D28k) protein, contributing to higher Ca retention and balance.

5. From 50 to 75 weeks of age in Experiment 1, the hens had little response to NaHCO₃ supplementation and showed a negative trend on eggshell thickness and strength.

6. It is concluded that dietary supplementation with 3 g NaHCO₃ g/kg improves Ca absorption and eggshell quality of laying hens during the peak but not late production period, with the introduction of continuous lighting.

  相似文献   

Crop milk protein is synthesised following activation of the IRS1/Akt/TOR signalling pathway in the domestic pigeon (Columba livia)     

X.-C. Hu  C.-Q Gao  X.-H. Wang  H.-C. Yan  Z.-S. Chen 《British poultry science》2016,57(6):855-862

1. The experiment was conducted to study whether insulin receptor substance 1 (IRS1) / Protein kinase B (Akt)/target of the rapamycin (TOR) signalling pathway activation stimulates crop milk protein synthesis in the domestic pigeon (Columba livia).

2. Crop milk was collected from ten 1-d-old squabs and analysed for nutrient content. During the non-breeding period and the first day of lactation, blood samples were collected from 5 pairs of breeding pigeons and the levels of prolactin and insulin were determined.

3. Crop samples were collected from 5 pairs of breeders at d 14 and 16 of the incubation period and d 1, 3 and 7 of the lactation period. Crop samples were evaluated for changes in crop weight and thickness and changes in the expression patterns of IRS1/Akt/TOR signalling pathway–related proteins.

4. The results demonstrated that prolactin induces a gradual increase in the relative weight and thickness of the crop, with crops reaching a maximum size at the third day of lactation.

5. Pigeon crop milk contains 64.1% crude protein and 29.7% crude fat based on dry weight.

6. Serum prolactin and insulin levels in the lactation period were significantly higher than those in the non-breeding period. Compared with non-breeding pigeons, the expression of the phosphorylated IRS1 phosphorylated Akt, phosphorylated TOR, phosphorylated ribosomal protein S6 kinase, phosphorylated S6, phosphorylated eukaryotic initiation factor 4E binding protein 1 and eukaryotic initiation factor 4E were significantly up-regulated in the crop of pigeons in the lactation period.

7. In conclusion, prolactin might induce changes in crop tissue and form the physiological structure for crop milk synthesis. Furthermore, the synthesis of crop milk protein is regulated by activation of the IRS1/Akt/TOR signalling pathway.

  相似文献   

The normalisation of CAPN gene expression in M. pectoralis superficialis in broiler lines differing in growth rate and their relationship to breast muscle tenderness     

K. Piórkowska  K. Połtowicz 《British poultry science》2015,56(4):452-458

1. The aim of this study was to assess mRNA abundance of calpain 1 (CAPN1) and calpain 3 (CAPN3) in breast muscle of 80 fast-growing (FG) and slow-growing broilers (SG) and relate gene expression in relation to growth and Warner Bratzler (WB) shear force of breast muscle.

2. The expression of CAPN1 and CAPN3 genes was higher in the FG compared to the SG line, but significant results were obtained only for CAPN1. The CAPN1 mRNA level was strongly dependent on line and gender interaction.

3. Lower values of shear force were observed in the FG line, where a higher level of calpain expression was shown.

4. A new panel of housekeeping genes (RPL4 and SDHA) for normalisation of gene expression in muscle tissues could be used in other studies of gene expression in chicken.

  相似文献   

Epidemiological aspects of lice (Menacanthus species) infections in laying hen flocks from the State of Minas Gerais,Brazil     

L. Do Carmo Rezende  N. R. Da Silva Martins  C. M. Teixeira  P. R. De Oliveira 《British poultry science》2016,57(1):44-50

1. The epidemiology of chicken lice species such as Menacanthus stramineus, M. cornutus and M. pallidulus were studied during an observational, analytical and sectional survey, to determine predisposing factors for their occurrence in laying hen farms in the State of Minas Gerais, Brazil. A total of 431 houses on 43 farms were visited in 2012.

2. M. cornutus, M. stramineus and M. pallidulus occurred in 20.9%, 11.6% and 11.6% of farms, respectively. The frequencies of occurrence of M. cornutus, M. stramineus and M.pallidulus in poultry houses were 10.4%, 8.8% and 3.7%, respectively.

3. The epidemiological determinants for the occurrence of these species were investigated using Poisson or logistic regression models.

4. The region of the farm, the recent use of acaricides and the presence of birds, such as saffron finch (Sicalis flaveola), feral pigeon (Columba livia) and Guira cuckoo (Guira guira) around the farms were related to the epidemiology of M. cornutus.

5. Infestation by M. stramineus was associated with age of birds, number of birds per cage and the presence of Guira cuckoo and Chopi blackbird (Gnorimopsar chopi) near the poultry houses.

6. The occurrence of M. pallidulus was influenced by the type of facilities, presence of cattle egret (Bubulcus ibis) and free-range domestic hens around the farm.

7. The use of wire mesh nets in the houses and of forced moulting did not influence lice infestation.

  相似文献   

Fluctuations in total calcium and magnesium in the plasma and uterine fluid of the domestic fowl     

S E Solomon 《British poultry science》1971,12(2):165-168

Fluctuations in calcium and magnesium were measured in the shell gland fluid and blood from the inferior oviducal vein of the domestic fowl throughout the laying cycle.

It was concluded that:

1. The variations in calcium concentration reflected both the known uptake of this ion by the albumen and medullary bone formation and destruction.

2. The variations in magnesium concentration did not parallel the changes in calcium concentration.

3. Magnesium was released into the blood during medullary bone formation.

  相似文献   

Nutritional characteristics and quality of eggs from laying hens fed on a diet supplemented with chestnut tannin extract (Castanea sativa Miller)     

S. Minieri  A. Buccioni  A. Serra  I. Galigani  A. Pezzati  S. Rapaccini 《British poultry science》2016,57(6):824-832

1. The trial was performed with 80 laying hens belonging to two Tuscan autochthonous breeds: 40 birds of the Mugellese (MU) breed and 40 of the White Leghorn (WL) breed.

2. The animals were allotted to 4 groups of individually caged 20 hens each: two groups were fed on a commercial diet and worked as the control groups (MUC and WLC); the other two groups received the same diet, integrated with 2 g of chestnut tannin (CT) extract per kg of diet (MUT and WLT).

3. A sample of 70 eggs were randomly collected and analysed for cholesterol content, fatty acid (FA) profile, weight, thickness of shell and colour of yolk.

4. Physical parameters, including yolk colour, and indices of egg quality were not affected by the treatments.

5. The concentration of unsaturated FAs increased, whereas cholesterol was significantly decreased: ?17% in WLT and ?9% in MUT. Dietary supplementation with CT extract resulted in a modification of lipid composition, towards a more healthy quality of eggs.

  相似文献   

The hen's egg: Shell fracture under quasi‐static and static loading     

T. C. Carter 《British poultry science》1978,19(2):249-259

1. An equation fundamental to a recent theory of egg shell strength is P_mR_a = kSt_u(T— ε) in which P_m is the maximum force that an egg shell can exert on a body pressing against it, R_a is the reciprocal of the average curvature of the shell at its point of contact with the other body, k is a constant of proportionality, St_u is the ultimate tensile strength of egg‐shell material in the plane of the shell, T is the overall thickness of the shell at the point of contact and ε is the thickness of its weak inner layer.

2. Experiments that tested the equation are reported.

3. Shells developed rigidity when they were between 88 and 128 μm thick; this was taken to be the physical basis of ε.

4. Measurement of equatorial shell curvatures and force at failure of 240 eggs with normal shells (10 from each of eight hens of each of three strains), loaded at the equator at a low and constant rate, showed that the relationship of P_mR_a to T was linear, that e varied somewhat from hen to hen but the slope of the line did not, and that P_mR_a was reduced slightly if the shell was ridged or glossy; regression accounted for 74% of the variance of P_mR_a.

5. The absence of curvilinearity and of variation from hen to hen in the slope imply that the material constituting the palisade layer of the shell was homogeneous in respect of strength, both within and between hens, under the conditions of the experiment : kSt_u was constant.

6. Seventy‐one additional eggs of the same hens were similarly loaded until the load reached a value close to the known hen‐mean fracture load; of the 31 that survived loading, 25 showed delayed fracture, so under these experimental conditions kSt_u was not constant but a function of time.

7. Delays observed ranged from 1 to 62 803 s and showed a loose negative correlation with the quotient W_app/W_exp, where W_app is the load applied to the egg and W_exp is the load at fracture which would have been expected if loading had continued at the same low and constant rate.  相似文献   

The relative importance of traits reported in the first three gosford random sample tests     

W. H. Foster 《British poultry science》1967,8(3):201-207

An analysis was performed on the published results of the first, second and third Gosford Random Sample Tests to determine which of the various biological traits reported had the greatest influence upon the overall ranking. Ten traits were considered. It was found that regression on survivors’ average egg production and laying house mortality removed 88.1 per cent of the variation in financial return. The addition of average egg weight and daily food consumption increased this figure to 93.3 per cent. The remaining traits, number of unsaleable birds at 500 days, body weight at 500 days, age at 50 per cent production, blood spots, meat spots and shell thickness, did not produce significant reductions except in so far as they were correlated with those previously mentioned.

The financial returns expected from improvements in the four important traits were:

• Per bird

• + 12 in survivors egg production 2S. 4¼d. ± 1¼d.

• —5 in percentage laying mortality is. 5d.± 1d.

• + 1 g. in average egg weight 10½d. + 1 ½d.

• —5 g. in food consumed per day 43/4d.± 1¼d.

Laying house mortality was found to be positively correlated among the entries with survivors’ average egg production and with average egg weight.  相似文献