Replacement of groundnut cake by dried poultry manure in the diets of laying hens

1. The effect on food consumption by pullets when dried poultry manure (DPM) replaced part of dietary groundnut cake depended on the strain of the birds: in two of the three hybrids food consumption was not affected when up to 100 g DPM/kg was fed.

2. Increases in food consumption were accompanied by increases in egg production.

3. The food required per dozen eggs was improved by up to 100 g dietary DPM/kg and variation in the sizes of eggs laid depended on the hybrid.

4. Concentrations of DPM up to 100 g/kg did not affect the water‐soluble nitrogen content of the egg but the crude albumen nitrogen content was depressed at concentrations of 80 g/kg or above.

5. Feeding DPM to laying pullets depressed body weight.     

Influence of dietary calcium and phosphorus on metabolism and production in laying hens

1. The effects of different dietary concentrations of calcium (24 to 56.9 g/kg) and phosphorus (4.5 to 14.2 g/kg) on production and some aspects of metabolism were studied in laying hens.

2. Treatments did not affect egg numbers, food consumption, conversion efficiency of food to egg, bodyweight gain or mortality.

3. Increasing dietary calcium (Ca) significantly increased plasma Ca and inorganic phosphorus (P), breaking strength at the radius and egg specific gravity and significantly decreased plasma alkaline phosphatase and egg weight.

4. Increasing dietary phosphorus increased plasma P and decreased egg specific gravity significantly.

5. Plasma Ca, P and alkaline phosphatase and radius breaking strength were suitable indices of the Ca status of the hens.     

Genetic and phenotypic parameters for oviposition pattern traits in three selection lines of laying hens

1. Oviposition pattern and egg production traits were recorded in 471 hens from three selection lines. The lines, named according to their selection criteria, were egg number (EN), egg mass (EM) and egg mass, food consumption (EMFC).

2. Mean oviposition intervals within sequences were 24.9, 26.0 and 25.3 h, respectively in the EN, EM and EMFC lines. Corresponding heritability estimates were 0.52, 0.55 and 0.42.

3. The mean oviposition interval within sequences showed a positive genetic correlation with mean oviposition time.

4. Egg weight decreased significantly as the serial number within sequences increased, but only for sequences containing less than 18 eggs.     

Effect of dietary inclusion of ascorbic acid and palm oil on the performance of laying hens in a hot tropical environment

1. Two experiments were conducted to evaluate the effects of including ascorbic acid (AA), palm oil or a combination of both in the diets of laying hens during the hot months in a tropical environment.

2. The inclusion of AA improved egg production, food intake and efficiency of utilisation, and decreased the cost of food per kg egg. The addition of 400 mg AA/kg diet gave the most efficient performance.

3. Palm oil inclusion reduced the effect of heat stress and increased egg production, egg weight, food intake and efficiency of utilisation.

4. When 200 mg AA and 50 g palm oil/kg were used, additive responses were obtained with further improvements in egg production, food cost and efficiency.

5. Ascorbic acid and palm oil when fed alone or in combination reduced the incidence of cracked eggs.

6. Thus, 400 mg ascorbic acid/kg of diet, 50 g palm oil or 200 mg AA plus 50 g palm oil/kg diet ameliorated the effects of heat stress in laying hens.     

Response from selection for income minus food cost in laying hens,estimated via the animal model

1. Selection for income minus food cost between 21 and 40 weeks of age was carried out in two replicate lines of brown egg layers for 5 generations in a population derived from a commercial cross between Rhode Island Red males and White Plymouth Rock females. Each replicate and an unselected control line consisted of 20 male and 80 female breeders.

2. Egg production, egg weight and food consumption were recorded on 1200 hens in every generation. Parent females were selected on individual performance. Males were not recorded and selected at random within half sib families to minimise rate of inbreeding.

3. A linear selection response of 0.46 and 0.43 monetary units per generation was observed, which resulted in a total response of 19.8% and 18.2% of the phenotypic mean of the base population over the 5 generations. A large increase in egg weight was the most important reason for the selection response in income minus food cost.

4. Further changes in associated traits were: an increase in egg number and egg mass, and a decrease in age at first egg, body weight and food: egg mass ratio.

5. The direct and correlated selection responses were similar in both lines. The realised response was somewhat less than expected in both lines.

6. A summary of phenotypic and genetic parameters, estimated from the data, is given. All genetic correlations between income minus food cost and the associated traits analysed, were in a favourable direction.     

Selection for efficiency of food utilisation in laying hens: Direct response in residual food consumption and correlated responses in weight gain,egg production and body weight

1. Two‐way selection was performed in a White Leghorn population for percentage residual food consumption, defined as the percentage deviation of the observed from the expected food consumption. Expected food consumption was estimated using a multiple regression equation including weight gain, egg production and metabolic body size as independent variables.

2. Three selection lines were established from a common population, two low lines and one high line. In addition, one control line was kept. The generation interval was one year and the experiment lasted for 4 generations.

3. The direct selection response was considerable and the realised heritability was close to 0.5. Food intake and food conversion (FCR) were lower in the low lines than in the high line.

4. The correlated selection responses showed no phenotypic or genetic correlations between percentage residual food consumption and egg production, but one of the low lines had a heavier adult body weight than the high line. No undesirable correlated responses were observed.     

Comparison of nutritive values of groundnut oil cake and Niger oil cake for laying pullets

1. The nutritive value of Niger oil cake (Guizotia abyssinica, Cass.) as a protein supplement for layers’ diets has been assessed.

2. Replacing groundnut oil cake (GNC) by Niger oil cake (NC) on an isonitrogenous basis, did not affect egg production, egg weight or the amount of food required per dozen eggs.

3. The percentage retention of nitrogen from diets containing 30% GNC or 30% NC was similar.

4. The ME value of NC used was 3025 kcal/kg.

5. It is concluded that NC can replace GNC in layers’ diets.     

Long‐term selection for increased egg production 1

1. Results are presented of a closed White Leghorn flock selected for increased egg production over a period of 17 years.

2. During the last 7 years a random breeding sample of the production flock served as a genetic control.

3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g).

4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19.

5. The realised heritability of egg production up to 275 d old was estimated to be 0.14.

6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48.

7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation.     

The relationship between hatching egg weight and subsequent performance of broiler chickens

Small eggs constitute a high proportion of the eggs laid by pullets. The literature shows that chick hatching weight is strongly correlated with egg weight, but evidence on the influence of egg weight on hatchability and subsequent performance of chicks is less certain.

The aim of this experiment was to determine the profit returned at 12 weeks by broiler chickens hatched from eggs ranging in weight from 44 g. to 58 g. at one gram intervals and to determine how competitive and separate rearing might modify the relationship.

A total of 6000 eggs were collected during 10 days from a 28‐week‐old, broiler breeding flock and graded into the above mentioned egg weight classes. From these, a total of 3480 day‐old broilers were housed. Each egg weight class was equally represented and balanced for sex.

Hatchability and fertility showed no consistent trend with egg weight for eggs above 46 g., but below the 47 g. level there was a trend of declining fertility and hatchability.

A strong positive relationship was found between the weight of the chick at 1 day of age and egg weight for both males and females with no significant difference overall in body weight between the two sexes.

Body weight to 12 weeks was found to be strongly related to egg weight, in a linear fashion, though this influence declined with age.

There was a greater influence of egg weight on body weight at all ages in the separate rearing treatment compared with competitive rearing but this was not significant after 10 weeks.

Egg weight had an important bearing on body weight and profit at 12 weeks, but no effect on food conversion or mortality.

The increased profit over food costs per 100 day‐old chicks was found to be 52.75 cents for the separately reared birds respectively for each 3 g. increase in egg weight.     

Comparison of food intake,rate of consumption,pecking activity and behaviour in layer and broiler breeder males

1. The food intake, rate of food consumption (g/min) and behavioural time budgets of individually caged broiler and layer (white egg) males were compared in the early morning (1.5 to 3.5 h after onset of photoperiod) and afternoon (5.5 to 7.5 h after photostimulation) on 4 different days at 11 to 12 weeks of age. Correlations among rate of consumption, the proportions of time on different activities and previously estimated scores for fearfulness were calculated.

2. Food intake and rate of consumption were two‐fold greater in broilers than in layers. The proportion of time spent feeding in the morning was lower in layers compared with broilers and was similar in the afternoon. Rate of consumption was higher in the morning than in the afternoon in both lines.

3. Overall, a similar proportion of time was spent feeding, standing and sitting in bodi lines. The birds were more likely to be sleeping (eyes closed) in the afternoon than in the morning.

4. The proportions of time spent on preening, pecking and stereotypic pacing were greater in layers than in broiler breeders. The proportion of time spent drinking tended to be higher in broiler breeders than layers.

5. Two measures of fearfulness, aversion to a looming human and a novel rod were respectively positively and negatively correlated to time drinking and stereotypic pacing.

6. The time spent in stereotypic pacing was negatively related to rate of consumption and time spent preening.

7. The results suggest that low food intake is associated with increased arousal, fear and frequent feeding and drinking. There was no evidence that beak related activity was related to fearfulness.     

Influence of stocking density and layer age on production traits and egg quality in Japanese quail

1. Japanese quail hens were housed from 6 to 26 weeks of age in cages providing areas of 150, 180, 210 and 240 cm²/bird.

2. Body weight gain, age at 50% egg production, mortality, hen‐day egg production and food conversion values showed significant improvement with proportionate increase in cage space per layer.

3. Egg weight gradually increased with age but shell thickness was influenced neither by age of the hen nor by stocking density.

4. Yolk index and colour were superior in the lowest stocking density (more cage space) group; other egg quality traits and egg weight were not influenced by stocking density.

5. The albumen index, internal quality unit, yolk index and yolk colour values increased with age.     

Effects of body weight at sexual maturity and the degree and age of restriction during rearing on the ovarian follicular hierarchy of broiler breeder females

1. Groups of 18 birds were reared to 10 different body weight targets in a randomised block experiment to assess the effect of body weight and the degree and age of restriction on ovarian function at first egg.

2. There was no effect of age at restriction (15 to 18 compared with 19 to 22 weeks) on the number of yellow follicles.

3. The treatment with the larger body weight of two groups given the same degree of restriction (maintenance) had more follicles than the treatment which had a smaller body weight.

4. There was a positive linear relationship between the number of yellow follicles and body weight and food intake. Addition of the weight of fat or age at first egg to the model increased the residual mean squares.

5. The proportion of atresia among yellow follicles and the incidence of internal ovulation increased with body weight at first egg.

6. It was concluded that the physiological processes occurring during rearing which underlie ovarian function are reflected solely in the body weight and food intake of broiler breeders at first egg.     

Whitening of brown shelled eggs: Individual variation and relationships with age,fearfulness, oviposition interval and stress

1. Fearfulness, shell colour, incidence and degree of shell whitening and the interval between ovipositions were studied in two populations of 30 brown egg laying hens with family histories of a low or a high incidence of egg shell whitening.

2. Hens of the population with the high incidence of whitening appeared to be more fearful than hens of the population with the low incidence of whitening.

3. Brown colouration of the egg shell and the incidence and degree of shell whitening declined as the hens aged.

4. Brown colouration and egg shell whitening were most pronounced on the blunt ends of the eggs.

5. A large part of the variation in egg shell whitening was attributable to the individual (hen) component of variance.

6. Differences in egg shell whitening, between the two populations, were detectable throughout the 26 weeks of the experiment.

7. Oviposition intervals were similar for normal and coated eggs when birds were not exposed to disturbance.

8. Disturbance of hens increased oviposition intervals and the incidence and degree of shell whitening, to a similar extent, in both populations.

9. It is concluded that stress‐related egg retention is not the sole factor responsible for abnormal egg shell whitening. Shell whitening may occur as a consequence of the premature termination of shell pigmentation as well as a consequence of the retardation of oviposition which occurs when hens are disturbed.     

Genotypic differences in speed and magnitude of response to ahemeral lighting

1. The paper compares between three genetically different lines in their egg weight and shell thickness response to a 28‐h cycle.

2. The response in shell thickness to ahemeral lighting was more rapid (2.2 d) than for egg weight (4.2 d).

3. Differences between genotypes were evident in both the speed and magnitude of response.

4. Overall, egg weight and shell thickness on the 28‐h cycle were 7% and 8% greater than on 24 h.

5. The allometric increase indicates that the increase in shell weight was on average 14% more than the increase in egg weight.     

Performance of lines selected for fast‐and slow‐hatching times and crosses among them 1

1. Males of a control line and two lines selected for fast‐ and slow‐hatching were mated to females of the same three pure lines and three crosses between them. Hatchability, egg weight and hatching time were measured.

2. No significant differences were found between genetic groups in hatchability.

3. Groups containing the fast‐hatching line genotypes were significantly smaller in egg weight than those not containing this line.

4. Significant differences in hatching time existed between male lines and between female lines within pure and cross‐line parent types while no differences were observed between the female parent types and no interactions of male by female lines occurred.

5. It was concluded that inbreeding in the pure lines (10%) did not affect any of the variables measured.

6. The results on hatching time support the conclusion that little genetic variance other than additive variance is involved for this trait.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

Genetics of changes in economic traits during the laying year

Body weights, egg weights and egg numbers were measured at different ages in two distinct, fully pedigreed, random bred strains of White Leghorns over a period of 3 years. The heritabilities of the separate measurements and the genetic correlations between them were obtained by an analysis of variance and covariance. The principal findings were:

(i) The heritability of weight gain declined sharply with age over consecutive periods after 12 weeks. The genetic correlation of body weight at 12 weeks with gain in subsequent periods was low. There appeared to be sufficient genetic variance in growth rate in these later periods to alter the growth curve substantially by selection. For example, it should be possible to breed strains with a rapid early growth and low mature body size.

(ii) There was evidence of genetic variation in the change of egg weight with time. The genetic variation was, however, so low that in any selection programme to improve 28‐week egg weight without changing 44‐week egg weight the progress would be very slow.

(iii) Body weight at 12 weeks was genetically negatively correlated with sexual maturity. Its correlation with production in the first 44 weeks was positive in both strains, but not significantly different from zero.

(iv) Body weights after 28 weeks were apparently uncorrelated with egg production or sexual maturity.

(v) Egg weight and production traits show considerable heterogeneity of variance between years, probably partly due to their distribution not being normal.

(vi) The pattern of genetic variation appeared to differ significantly between the two strains so that correlated responses would not necessarily be the same.

(vii) There was a suggestion of maternal effects acting upon body weight but the evidence was somewhat contradictory and inconclusive due to the high standard error of the estimates.

(viii) None of the 15 traits measured regressed over the 3 year period of relaxation of selection.     

Effects of insoluble grit on the productive performance of ten white leghorn strains 1

1. White Leghorn chicks of 10 strains were reared, on wire, to 140 d with or without insoluble grit and then were housed in laying cages where grit and no grit treatments were superimposed on the rearing treatments.

2. During rearing the feeding of grit had no effect on the body weight or food conversion ratio but there were small treatment effects on mortality between three commercial strains.

3. During laying the grit treatments had no direct effects on food consumption, mortality, final body weights, age at first egg, egg production, Haugh units or total blood spots.

4. Egg weight and specific gravity at 450 d were affected by grit treatment but the differences were small.     

Effect of cuticle removal on the water vapour conductance of egg shells of several species of domestic bird

1. The effect of egg shell cuticle removal, using a 14.7 mM solution of sodium hypochlorite, on the water vapour conductance of egg shells was studied in 5 species of domestic bird.

2. The water vapour conductance of fowl and Muscovy duck egg shells was not affected by the treatment.

3. Cuticle removal increased the conductance of turkey and goose shells, particularly those already relatively porous to water vapour.

4. Removal of cuticles from domestic duck egg shells increased water vapour conductance. In this case the effect was most marked for eggs with lower initial conductances.

5. The differing patterns of resistance to water vapour loss associated with egg shell cuticle are related to the ultrastructure of the cuticle itself, especially the number and size of cuticular fissures.

6. The results suggest that egg shell cuticle is a component in a series of resistances associated with the egg shell and that the use of Fick's Law is insufficient to explain water vapour diffusion across the shell.

7. Embryo survival may be improved by cuticle removal, though this may be limited to those species in which the cuticle restricts water vapour loss in initially low conductance egg shells.     

Traits influencing the hatching performance of Japanese quail eggs

1. Japanese quail eggs from moderately heavier sires showed superior fertility; while fertile eggs from moderately heavier dams hatched slightly better than the eggs from lighter dams.

2. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.

3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.

4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.

5. Fertility and hatchability were directly proportional to the egg weight.

6. Quail egg shell colour, tints and blotches were found to influence hatching performance.

7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.

8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.

9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h.