Relationship of decreased caecal urease activity by dietary penicillin to nitrogen utilisation in chickens fed on a low protein diet plus urea

1. The relationship of the decreased caecal urease activity by dietary penicillin to nitrogen utilisation was assessed in chickens fed a low protein diet plus urea.

2. Dietary penicillin at 20 and 100 mg/kg decreased anaerobic bacteria counts, urease activity and ammonia concentration in caecal contents (P< 0.05, except for ammonia in the case of the 100 mg/kg penicillin diet).

3. The 20 mg/kg penicillin diets significantly increased the excretion of urea and total nitrogen (P < 0.05) and decreased ammonia excretion, and significantly reduced nitrogen retention (P < 0.05). The 100 mg/kg penicillin diet also resulted in similar but not significant changes, which tended to be less than those by the 20 mg/kg penicillin diet.

4. Ammonia, urea, glutamine and uric acid concentrations in blood, liver and kidney were unchanged by dietary penicillin.

5. It is concluded that caecal ammonia production from urea was closely correlated with nitrogen utilisation in chickens fed a low protein diet plus urea.     

Effects of short intermittent lighting on food consumption and performance of dwarf broiler breeders and progeny

1. Two hundred and sixty four dwarf broiler breeder hens were subjected to ad libitum or restricted feeding and to four lighting patterns: 15L (bright light):9D (dark), 15L:9d (dim light), 2L:10d: 1L:11d, (0.5L:3.5d) × 6.

2. Breeder hens fed ad libitum and subjected to either conventional or intermittent lighting ingested respectively, 25 g and 14 to 17 g more than hens restricted to 115 g/d.

3. Body weight was greater in hens fed ad libitum irrespective of the lighting pattern and of the amount of food intake.

4. Persistency of egg production was impaired by intermittent lighting.

5. Ad libitum feeding reduced egg fertility. The decrease was larger in breeder hens on intermittent lighting.

6. Hatchability was increased in hens submitted to the symmetrical lighting pattern (0.5L:3.5d).

7. Egg and chick weights were higher in hens fed ad libitum.

8. Shell index and shell breaking strength increased in restricted hens on the intermittent lighting pattern (0.5L:3.5d) × 6.

9. The best performance was obtained in restricted hens on the conventional lighting pattern.     

Inheritance of body weight and rate of gain in Japanese quail

1. The effects of hatch date, location and sex on the body weight and rate of gain in Coturnix coturnix japonica were examined.

2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.

3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.

4. Weight gain was greater if illumination intensity up to 35 d was less.

5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.

6. Variance components and genetic parameters were estimated.     

Behaviour of egg shell under compression in relation to deformation measurements1

1. The egg does not completely obey Hook's law when compressed between flat surfaces.

2. Deformation was not completely reversible due to crumbling at the points of contact with the force.

3. There are three components of non‐destructive deformation: (a) local deformation at the points of contact, (b) local surface crumbling and (c) deformation of the over‐all shell structure.

4. The latter two are uncontrolled, contributing to errors in the prediction of fracture force and depending on the non‐destructive force applied.

5. These effects should be considered in test selection and interpretation.

6. The optimum non‐destructive force was found to be 1 kg.     

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.     

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.     

Haematology and blood composition at two ambient temperatures in genetically fat and lean adult broiler breeder females fed ad libitum or restricted throughout life

1. Genetically fat and lean adult broiler breeder females were fed ad libitum or restricted throughout life. At one year of age, comparisons of blood viscosity and haematology and changes in blood chemistry after exposure to thermal stress were conducted.

2. Whole blood viscosity was more than twice as high, and plasma triglyc‐eride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes.

3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females.

4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil‐lymphocyte ratio.

5. Fat line birds had a higher blood pCO₂ and lower pH than lean line birds.

6. Thermal stress was associated in ad libitum‐fed birds with a rise in blood pH and a decrease in pCO₂, and in restricted birds with a decline in blood pH and an increase in pCO₂.

7. Blood creatine kinase activity increased in all groups under thermal stress.     

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.     

Metabolic and anatomical adaptations of light‐bodied chicks to intermittent feeding

1. Chicks of a light‐bodied strain were deprived of food on alternate days from 15 to 46 d of age.

2. Hyperphagia, amounting to twice the intake of control birds early in the experiment, occurred on the repletion day.

3. Final body weight attained 80% of that of the controls.

4. Body fat concentration decreased at first but returned to that of controls after 3 weeks.

5. A consistent hyperlipaemia was observed after food deprivation or restoration.

6. There was a marked increase in the digestive enzymes found in the small intestine, but not in the pancreas during the repletion day.

7. These responses may be considered as mechanisms to reduce the physiological manifestations of starvation.     

Effect of egg composition on hatchability and on growth and slaughter characteristics of meat-type chicks

1.?Using the so-called TOBEC (Total Body Electrical Conductivity) method, which allows the determination of egg composition in vivo, correlations between egg composition, hatchability and hatched chicks’ development were studied.

2.?A total of 1500 hen eggs (Ross-308) were measured by TOBEC, and eggs with extremely high (10%, n = 150), extremely low (10%, n = 150) and average (10%, n = 150) electrical conductivity values were chosen for further investigation.

3.?During the incubation period, it was observed that eggs with high electrical conductivity had a significantly higher mortality than eggs with low electrical conductivity.

4.?It was observed that both the increase in electrical conductivity at the same egg weight, and the increase in egg weight at the same electrical conductivity resulted in an increase in the hatching weight.

5.?It was found that the dry matter, protein and fat content of the chicks hatched from eggs with low electrical conductivity was higher at hatching than that of the chicks hatched from eggs with high electrical conductivity.

6.?At 42 d of age the liveweight of cocks and pullets hatched from eggs with low electrical conductivity was 3·2 and 8·2% higher than the liveweight of cocks and pullets hatched from eggs with high electrical conductivity.

7.?Because of the higher liveweight at slaughter, there was a significant superiority of the chicks hatched from eggs with low electrical conductivity in the case of the examined carcase traits at slaughter.

8.?Similar tendencies were found also in the ratios of carcase variables to liveweight, but the between group differences were not statistically significant in this case.

9.?Based on the results it was concluded that TOBEC seems to be a useful method for separating eggs with different composition.

10.?This could be a good starting point for further in vivo investigations in order to clarify the effect of egg composition on hatchability and further development.     

Explanted embryo culture: In vitro and in ovo techniques for domestic fowl

1. Embryos of the domestic fowl (72 h old) have been explanted into shell‐less cultures or ‘surrogate’ eggshells, in order to investigate the possibility of rearing these embryos to hatching.

2. Rocking embryo cultures during the first half of incubation enhanced embryo growth.

3. Embryos explanted into ‘surrogate’ eggshells of either other individuals or other species have been successfully ‘hatched’.

4. A normal chorioallantois is formed in these surrogate eggshells. This enables a functional albumen sac to form and eggshell resorption to be achieved.

5. Embryos grown in ‘surrogate’ eggshells are slightly smaller than controls but otherwise normal.

6. The technique provides opportunities for genetic engineering experiments.     

The bacterial flora of unhatched eggs

1. The methods of bacteriological examination of hatchery waste eggs were compared.

2. Using one of these methods a survey was conducted on eggs which had failed to hatch from commercial hatcheries.

3. An assessment of the level of contamination in the eggs examined indicated an average level of contamination of 12.7%.

4. The contaminating flora was composed mainly of Micrococcus sp. and Enterobacteriaceae, with Streptococcus sp., Staphylococcus sp., Bacillus sp. and Pseudomonas sp. present at lower levels.

5. Various interrelationships between contamination and hatchability are discussed.     

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.     

Effect of pyridoxine on the distribution of chloramphenicol and its residues in the chicken

1. Chickens were given either a single dose of chloramphenicol (50 mg/kg body weight per os) or a dose of chloramphenicol together with pyridoxine (25 mg/kg per os) given 1 h before or 4 h afterwards.

2. Concentrations of chloramphenicol were determined in samples of serum and the rates of distribution and elimination extrapolated. Concentrations of chloramphenicol in muscle, liver and kidney were also determined.

3. Serum concentrations of chloramphenicol were lower in chickens given both pyridoxine and chloramphenicol compared with those given only chloramphenicol.

4. Differences were most pronounced during the post‐absorptive phase. The rates of disappearance of chloramphenicol residues from tissues were enhanced by pyridoxine.

5. The biological half life of chloramphenicol and area under the concentration‐time curve were both reduced by the concurrent administration of pyridoxine.

6. Availability of pyridoxine may be a rate limiting factor in the biotransformation of xenobiotics, though its indiscriminate use could cause failure of antibiotic therapy.     

Digestibility studies in broiler chickens: Influence of genotype,age, sex and method of determination

1. The influences of genotype, age and sex on droppings digestibility coefficients of a compound food were studied using male and female broiler chickens of three different genotypes at 2, 4 and 6 weeks of age.

2. Because the traditional method of determination of droppings digestibility coefficients of nitrogen may lead to systematic errors in estimating the feeding value of foodstuffs, a method is proposed to determine the ileal digestibility coefficients. The ileal method is compared with the droppings method for a mixed food and for two foodstuffs: wheat and solvent‐extracted soyabean meal.

3. Birds selected for efficient food conversion showed distinctly higher digestibility coefficients for all nutrients than birds selected for high growth potential or birds from a commercial strain.

4. The influence of age on digestibility coefficients was not consistent.

5. Female birds showed digestibility coefficients which were, in general, 3% higher than those of male chickens.

6. Interactions between genotype and sex and between genotype and age for energy metabolisability were the only interactions observed for digestibility measurements.

7. The method of determination influenced the amino acid digestibility coefficients of the mixed food and the relative feeding values of wheat and soyabean meal.

8. It is important to use well defined animals (genotype, sex, age) in evaluating foodstuffs.

9. The preferred method for determination of digestibility coefficients of nitrogen and amino acids is based on ileal sampling, although the differences in amino acid digestibility coefficients were small between methods.     

Diurnal patterns of feeding and activity in laying hens in relation to dietary restriction and cage shape

1. The diurnal feeding pattern and motor activity of medium‐weight hybrid hens housed in groups of four were observed. Cages of two shapes were compared: conventional deep cages (406 × 457 mm) and shallow cages (610 × 305 mm).

2. Birds in conventional deep cages were more active than those in shallow cages in each of four different periods of day. Activity reached a peak between 11.00 and 13.00 h irrespective of cage shape.

3. Mean feeding activity was greater in the shallow (45.6%) than in the conventional deep cages (39.9%).

4. Mean feeding activity was greater in birds fed ad libitum (43.3%) than in those fed on a restricted diet (40.4%).

5. Although restricted birds in shallow cages showed more feeding activity than those in conventional deep cages they consumed less food (56% against 67%) in the 7 h between supply of their daily ration and the onset of the dark period.

6. Feather damage was greater in the conventional deep cages than in the shallow cages.

7. The more efficient utilisation of food by hens in shallow cages is probably due largely to three factors: reduced levels of motor activity and general disturbance, a more leisurely eating pattern and better feather cover.     

Growth and laying performance of light‐hybrid pullets subjected to quantitative food restriction

1. Three degrees of quantitative food restriction producing body weights 88, 76 or 64% of controls at 20 weeks and three times of starting restriction 3, 6 or 9 weeks of age were compared with ad libitum‐fed pullets in a factorial experiment with 1800 light‐hybrid hens. Restrictions were applied such that the target weights were produced irrespective of time of starting.

2. Food intake was least when restrictions were started at 3 weeks.

3. Sexual maturity was delayed in proportion to the severity of restriction and resulted in lower percentages of small eggs.

4. Egg numbers decreased as restriction increased.

5. Mortality in restricted groups during rearing and laying was higher.

6. Optimal restriction was apparently intermediate between treatments producing 88 or 76% of ad libitum‐fed body weight. Body weight was so excessively affected by the most severe restriction that total production was adversely affected.

7. Restriction from 3 weeks was more profitable than restriction from 6 or 9 weeks, resulting in lower food cost during rearing and higher total egg production.     

Short‐term stressor effects of propranolol

1. The effects of propranolol (10 mg/kg) on plasma cholesterol, glucose, corticosterone and free fatty acids, on adrenal mass and cholesterol content and on body temperature were determined over a 24‐h period in 3‐week‐old Light Sussex chicks.

2. Changes in plasma cholesterol were equivocal, though there was perhaps a trend towards hypercholesteraemia.

3. Birds became hypoglycaemic within an hour but were hyper‐glycaemic between 2 and 4 h. At 24 h they were normoglycaemic.

4. Plasma corticosterone was increased markedly at 1 h but was decreased compared with the control at 2 h (P<0.01). Thereafter the concentration was in the normal range.

5. There was an enhanced hyperlipacidaemia in the treated birds after 1 h.

6. Adrenal cholesterol stores were decreased by 10% at 4 h but were unaffected at all other times.

7. Colonic temperature decreased by 1–6 °C after 2 h but was normal by4h.

8. It is concluded that propranolol has mild stressor activity which is lost within 24 h.     

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.     

The use of rapeseed meals and a mustard seed meal as a protein source in diets for laying pullets

1. Three experiments with laying pullets were carried out in which rapeseed meals (B. napus and B. campestris) and a mustard seed meal (B. juncea) formed 12% of the diet.

2. Dietary rapeseed had no effect on the onset of lay when fed from 17 weeks of age but caused a delay when fed from 10 weeks of age: changing to a control soyabean diet for the laying period resulted in normal egg production.

3. Diets containing B. napus but not B. campestris consistently depressed egg production and reduced egg weight in one experiment. Mustard seed meal did not affect performance.

4. Significant number of eggs with a “fishy” taint were laid by brown‐egged birds fed on a diet containing rapeseed.

5. Thyroids of birds fed on rapeseed meal diets during the laying period were significantly heavier than those of birds fed on diets containing mustard seed or soyabean.

6. The enlargement of the thyroid gland is probably related to the oxazolidinethione content of the rapeseed.