Dietary rapeseed meal and the incidence of tainted eggs

1. Incorporating 0, 3, 6 or 9% rapeseed meal in the diet of brown‐egg laying birds for 28 d resulted in the production of 0, 1.2, 19.3 and 20.9% tainted eggs respectively, the first tainted eggs being laid on the fifth day.

2. During the second and third weeks the incidence of tainted eggs exceeded 20% but fell to 11.4% during the final week.

3. Omission of the rapeseed meal from the diets halted the production of tainted eggs.

4. Neither egg production nor the health of the birds was adversely affected by the treatments.

5. The taint was described as “ fishy ” or “ crabby ” and was distinctive, but the source was not identified.     

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.     

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 feeding regimen and lighting pattern on the performance of broiler chickens in the hot,humid tropics

1. A food restriction study in conjunction with light control was conducted with commercial broiler chicks in a tropical environment.

2. Chicks on treatments 1 and 2 were fed continuously while those on treatments 3 and 4 were fed during the day (from 06.00 h to 18.00 h) and night (from 18.00 h to 06.00 h) respectively. Chicks on treatment 1 received only natural light during the day, while those on treatments 2, 3 and 4 received supplementary lighting during the night in addition to natural light during the day.

3. Food consumption by birds on treatment 2 was significantly higher at 56 days of age, followed by birds on treatments 1, 4 and 3.

4. The pattern of body weight gains was similar to the order of food consumption.

5. Efficiency of food utilisation was poorest for birds on treatment 2.

6. Mortality rates were not influenced significantly by the feeding regimen and lighting pattern.

7. Dressing percentage and proportion of abdominal fat were greatest for birds on treatment 2.     

Voluntary food restriction by laying hens mediated through dietary self‐selection

1. Individually caged Single Comb White Leghorn hens simultaneously received two diets which allowed selection of certain nutrients: these “ split‐diets “, essentially provided concentrated sources of either protein and energy (191 g crude protein, 12.82 MJ ME and 4.7 g Ca/kg diet), or calcium (107 g CP, 7.28 MJ ME and 131 g Ca/kg).

2. During four, 28‐d periods of lay, birds offered these split‐diets consumed some 7% less food in total than did control birds receiving a conventional diet ad libitum.

3. Calculation of nutrient intakes showed that birds on the split‐diets consumed significantly less protein, energy and calcium than the control birds.

4. Giving split‐diets also resulted in superior shell quality; treatment differences were also noted in the timing of oviposition.

5. It is suggested that the voluntary reduction in food intake noted for birds offered split‐diets is associated with an appetite for calcium.     

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.     

Effects of plastic anti‐pecking devices on food intake and behaviour of laying hens fed on pellets or mash

1. This study investigated effects of plastic anti‐pecking devices on food intake and behaviour to assess their applicability in commercial layer flocks.

2. In experiment 1, 72 individually caged ISA Brown pullets were fitted at 16 weeks of age (point of lay) with either ‘ring’ or ‘bumper’ beak devices or no device (control), half being fed on pellets and half on mash. The devices were held in place by lugs inserted in the nares.

3. There was evidence of discomfort immediately after fitting the devices, but not thereafter. In the first week, the devices reduced food intake, and were removed from 7 (15%) birds that lost weight consistently. Between 16 and 21 weeks, however, there were no significant effects of beak treatment or food form on either total food intake or egg production with the 65 remaining birds.

4. Beak treatment did not affect feeding efficiency (food intake per minute of feeding). The only behaviour affected was pecking at birds in adjacent cages, which was reduced with the ring device.

5. At 21 weeks, the birds were placed together in groups of 4 to 6 in 12 pens, each group consisting of birds from one of the 6 original treatments, and their behaviour was observed in experiment 2 between 21 and 23 weeks.

6. The only effects of beak treatment on behaviour were that pecking at pen walls was increased with the ring device, while pulling and eating feathers from group mates was seen mainly with control birds fed on pellets. Two birds were cannibalised in a control group on pellets.

7. Devices came off 3 (7%) birds in experiment 1 and were replaced, and rings slipped over lower mandibles of 2 (5%) birds in experiment 2 and were corrected.

8. At 23 weeks, beak lengths were increased with ring and bumper treatments, and pecking damage scores were low with all treatments.

9. It is concluded that these devices are not applicable commercially, but further trials would be justified with new improved designs.     

Effects of cage shape,colony size,floor area and cannibalism preventatives on laying performance

1. Wire cages of variable width and depth, with a floor slope of 1 : 12, were used in two experiments to study the effects of cage depth, feeding space (= cage width), floor area, colony size and two methods of controlling cannibalism in White Leghorn x Australorp laying hens.

2. The least floor area (0.035 m²/bird) depressed production in two‐bird cages. Floor area had little effect on the performance of larger colonies.

3. Birds in colonies of three, four or six laid and survived equally well when feeding space/bird and floor area/bird were constant.

4. Production per hen d and food intake were higher, but return on estimated capital outlay was lower, with 102 mm than with 76 mm feeding space/bird when colony size and floor area/bird were constant.

5. Production and food intake of birds which were not treated to prevent cannibalism declined, and mortality increased, as cage depth increased from 385 to 915 mm concomitantly with increasing colony size from 2 to 7 birds and decreasing feeding space from 152 to 43 mm/bird.

6. Increasing cage depth did not increase the proportion of cracked eggs.

7. Mortality was higher among birds fitted with plastic spectacles than among debeaked birds.     

Dietary selection of protein and energy by pullets and broilers

1. White Leghorn pullets and sexed broilers were allowed a free choice of two “ split‐diets “ which were concentrated sources of either crude protein (463 g/kg diet) or energy (13.32 to 14.00 MJ/kg diet).

2. Pullets receiving these two diets displayed a slower, but more uniform growth rate than did birds offered a single conventional diet. Up to 11 weeks of age, control birds consumed significantly more protein while the converse was true from 11 to 20 weeks. These differences are discussed in relation to the stage of sexual maturity.

3. Broilers offered the split‐diets grew more slowly and had an inferior food conversion ratio compared with control birds fed on a two‐stage rearing programme.

4. Among the broilers offered split‐diets, the usual sex differences were not observed for weight gain or carcass fat content.     

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.     

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.     

Welfare assessment of broiler breeder and layer females subjected to food restriction and limited access to water during rearing

1. A factorial experiment was conducted to assess the welfare at different ages of two strains of broiler breeder and one layer strain during rearing using a range of indicators. The birds were fed ad libitum or restricted and provided with free or limited access to water.

2. Food‐restricted birds spent a large proportion of time scratching and pecking the litter compared with birds fed ad libitum.

3. The heterophil/lymphocyte ratio and the proportion of basophils were raised at 8, 12 and 16 weeks, and the plasma concentrations of corticos‐terone were higher at 8 and 12 weeks of age in restricted birds compared with those fed ad libitum.

4. Creatine kinase activity was higher in broiler breeders fed ad libitum compared with layers and restricted broiler breeders. The activity of aspartate transaminase was higher in restricted layers compared with birds fed ad libitum and was similar in broiler breeders.

5. Plasma viscosity was lower in food‐restricted compared with ad libitum‐fed birds.

6. Limiting access to water had little or no effect on the welfare indicators although food‐restricted birds with free access to water spent more time drinking than birds fed ad libitum.

7. There were no important differences between the two broiler strains. Layers spent less time resting than broiler breeders and had higher plasma corticosterone concentrations at 3 and 16 weeks of age.

8. It was concluded that there was evidence for physiological stress associated with restricted feeding at least between 8 and 16 weeks of age. It was suggested that the altered behaviour of broiler breeders kept on litter may indicate that they can cope with food restrictions and that this may be acceptable in relation to the long‐term benefits of limiting body weight during rearing. The same may not be true for layers.     

Intermittent lighting and feeding schedules for broilers incorporating long periods of darkness

1. Intermittent lighting and feeding schedules incorporating long periods of darkness and periods without access to food were applied to growing broilers.

2. Birds exposed to a 2 h light(L): 10 h dark(D) lighting schedule with feeding restricted to the light periods ate significantly less food and grew more slowly than conventionally‐reared birds. Satisfactory growth and efficiency of food utilisation were obtained by allowing these birds access to food during the dark periods.

3. Altering the lighting schedule to 2L:6D resulted in birds with food intakes and growth rates similar to those reared conventionally, even when feeding was restricted to the light periods.

4. Releasing birds from the light and food restriction for the 2 weeks preceding slaughter resulted in greater food consumption which was not characterised by significantly better growth or food utilisation.

5. Feeding a diet of high energy or pelleting a diet of low energy during the period of restriction increased food intake and improved growth rate.

6. The response of broilers to intermittent lighting and feeding was not significantly influenced by ambient temperature within the range 16 to 35 °C or by the energy concentration of the diet fed before the introduction of the intermittent schedule.     

Response of three class‐IV major histocompatability complex haplotypes to Eimeria acervulina in meat‐type chickens

1. The importance of MHC genes and background genes in controlling disease resistance, including resistance to avian coccidiosis, has not been clarified in meat‐type chickens.

2. The role of class IV MHC genes in resistance to Eimeria acervulina was assessed in F2 progeny of a cross between 2 meat‐type lines, selected divergently for immune response to Escherichia coli.

3. Disease susceptibility was assessed by lesion score, body weight, packed cell volume and carotene absorption.

4. Chickens with the “K” class IV MHC haplotype had lower lesion scores than chickens with “F” and “A” haplotypes.

5. Plasma carotene concentrations were higher in chickens with “K” haplotype and lower in chickens with “F” and “A” haplotypes whereas body weight and packed cell volume were less sensitive measures of Eimeria infection.

6. Eimeria acervulina resistance appears to be associated with MHC class IV genes; information about MHC haplotypes may be useful in selecting for increased resistance of meat‐type chickens to coccidiosis.     

The effects of restricted feeding on adrenal cortical activity in the immature domestic fowl

1. The effect of reducing food intake to 75% of the ad libitum intake was determined from hatching to 8 weeks in young Light Sussex chickens.

2. Restricted birds were lighter throughout the experiment.

3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.

4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.

5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.

6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found.     

Behavioural and growth responses of broiler chickens to dietary water content and climatic variables

1. The behavioural responses and growth of broiler chickens were investigated over three seasons using two wet mashes with food:water ratios of 2:1 (HW) and 3:1 (MW).

2. Wet mashes fed in the hot dry season caused significantly lower rates of panting, a major thermoregulatory behaviour. This may be an indication of increased comfort in hot dry conditions for birds fed wet mashes.

3. Feeding activities of birds fed dry and wet rations respectively increased and decreased with decrease in seasonal temperature. The peaks of both feeding activity and consumption in the cool‐dry season were attained by birds fed dry diets and in the hot dry season by those fed wet mashes.

4. Diurnal distributions of food and water intakes were more even in the hot dry season for those fed wet mashes. This may again suggest a higher degree of comfort on the hot dry season when birds are fed wet mashes.

5. In the hot dry season, 60% of birds preferred wet mashes, whereas 80% of birds preferred dry meal in the cool dry season. This may be attributable to the lower temperature of wet mashes.

6. Similar patterns in feeding activity, food consumption and daily weight gain occurred in response to dietary presentation and season.

7. Feeding of dry meal under cool dry conditions and wet mashes in the hot season may be advantageous. Irrespective of season, water temperature may have to be raised to about 30°C before addition to meals for chicks under brooding. This may be necessary as preliminary investigations in this laboratory indicate that food temperatures below 22°C may at the brooding stage discourage food intake and activities.     

Feeding and pecking behaviour in ostrich (Struthio camelus) chicks in captivity

1. Three sets of experiments were performed on two batches of ostrich chicks to investigate the factors affecting the pecking and feeding behaviour of grouped individuals.

2. Chicks showed no significant alteration of their feeding behaviour in response to raising pen walls in the rearing facility from 30 to 60 cm.

3. Further analysis on a different set of birds revealed consistent short term individual differences in the frequency of feeding and non‐feeding pecks.

4. There were significant pen effects on behaviour suggesting the possible development of a pen ‘culture’ of pecking behaviour.

5. Pecking behaviours in 26 to 33 d‐old chicks, with the exception of drinking, were generally negatively correlated, so any non‐food pecking by a chick was generally associated with fewer pecks targeted at food.

6. By the age of two months chicks were pecking at food on the floor to a far greater extent than at any food presented in food trays.     

The effects of partial defeathering on energy metabolism in the laying fowl

1. The effects of a complete removal of feathers from the neck and/or breast on the energy metabolism of laying hens were measured by indirect calorimetry.

2. The daily heat production of fed birds was significantly increased if feathers were removed from the entire neck plus breast region but not if the neck only or breast only were denuded.

3. Removal of feathers from the neck plus breast led to a 10% increase in food consumption.

4. The partially‐defeathered birds laid more eggs.     

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.     

Use of four types of litter for rearing broilers

1. One hundred and forty four Shaver broiler chicks (Starbro 15) were reared from 4 d to 56 d of age on 4 types of litter: sawdust, paddy straw, sand and rice husk each spread to a depth of 75 mm.

2. Birds reared on rice husk litter showed the greatest food consumption, greatest weight gain, best food conversion efficiency and scored highest in production number.

3. Survivability was also highest with rice husk group (94.4%) but differences in this variable were not thought to be attributable to types of litter.

4. Breast blisters were found only in birds reared on sand (8.3%).

5. It was concluded that rice husk is a suitable litter for rearing broilers on the floor, particularly in paddy‐growing countries.