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.     

Effect of choice feeding on the performance of broilers

1. Male broilers from 21 to 56 d of age were fed their diet either mixed as pellets or mash, or as separate ingredients presented on a free‐choice basis, to determine whether feeding method affected growth, carcase composition or profitability to 56 d of age.

2. The 12 treatments were: 2 completely balanced diets fed as mash or pellets, 8 choice fed diets containing maize or sorghum as the energy source (whole or mash) and protein concentrate (pellets or mash) and 2 unbalanced mixed mash diets containing 50% grain (maize or sorghum) plus 50% protein concentrate.

3. For the choice treatments, one food, grain (maize or sorghum) or protein concentrate (mash or pellets), was placed in each feeder. Broilers fed the complete pelleted or mash diet received the diet in both feeders. Food consumption was recorded weekly. Broilers were weighed at 42 and 56 d of age.

4. There were no significant differences between treatments and the pelleted control diet with regard to body weight, food consumed, food efficiency, carcase ash, dressing percentage and mortality.

5. Choice fed broilers receiving the energy source as whole grains had larger gizzards while the higher protein diets (50/50) resulted in a higher carcase moisture and protein but lower carcase fat than the broilers fed the pelleted control diet.

6. The main advantage of choice feeding appears to be the economical savings of feeding whole grains as the energy source.     

The performance of cross‐bred hens given free choice feeding of whole grains and a concentrate mixture and the influence of source of xanthophylls on yolk colour

1. Cross‐bred hens were offered, from 25 to 73 weeks of age, diets based on either wheat or barley in the form of either a mash or as whole grains plus a concentrate mixture; four sources of xanthophylls were also compared.

2. Wheat reduced food intake by 8%, increased efficiency of food conversion and live‐weight gain while barley increased litter moisture content, and, during the first half of the laying year decreased egg production by 3.3% and yolk colour by 4%.

3. Hens offered whole grains ate 11% less food, converted food into eggs more efficiently, were heavier and laid larger eggs than those given the mash diets.

4. With whole grains yolk colour was less than with mash diets during the first 24 weeks of lay but this was reversed during the last 24 weeks of lay.

5. Either canthaxanthin or citranaxanthin or β‐apo‐8'‐carotenoic acid ethyl ester plus canthaxanthin in diets containing lucerne meal produced eggs with acceptable yolk colours.     

Studies on effects of nutritional factors on bone structure and osteoporosis in laying hens

1. A modern hybrid strain of laying hen (Hisex) was fed from point of lay to 68 weeks on a control diet and diets containing oystershell, fluoride, 1,25‐dihydroxycholecalciferol, ascorbic acid, a lower concentration of phosphorus and a combination of a lower concentration of crude protein and higher concentration of vitamin K. Hens from a much older strain (Brown Leghorn J‐line) were fed on the control diet.

2. Plasma variables were measured during lay. End‐of‐lay trabecular and medullary bone volumes in the proximal tarsometatarsus and free thoracic vertebra were measured by histomorphometry.

3. The majority of Hisex hens were considered to be osteoporotic by the end of lay. In contrast, none of the J‐line were osteoporotic.

4. None of the nutritional treatments affected trabecular bone volumes. Medullary bone volumes were increased significantly by feeding oystershell or fluoride.

5. There was no phenotypic correlation between egg production and trabecular bone volume in the Hisex hens.

6. The experiment provided evidence that osteoporosis in laying hens, as assessed by trabecular bone volumes, is not caused by calcium deficiency and could not be prevented by any of the nutritional treatments studied.     

The necessity of supplementing laying hen diets with linoleic acid

Results from four experiments with laying hens have been re‐examined using the means of individual 28‐d periods during egg production to investigate the influence of the developing ovary and linoleate storage during growth on the linoleic acid requirement of the laying hen.

Apart from a possible beneficial effect during the first few weeks of production, little increase in egg weight occurs when birds are fed on conventional rearing diets and then fed on laying diets containing linoleic acid in excess of requirement.

After depletion of linoleate reserves, dietary supplementation with linoleic acid significantly increases egg weight at any age.

The necessity of supplementing diets for laying hens with linoleic acid is discussed.     

The effect of delaying the onset of laying in pullets with a low‐calcium diet on subsequent egg production

1. A low‐calcium diet (0.5 g calcium/kg) was used to prevent the onset of laying in young pullets.

2. It was fed at 16 weeks of age to five separate groups (groups 2 to 6) each of 50 to 60 birds.

3. Group 2 was fed on a normal layers’ diet at 23 weeks of age, group 3 at 27 weeks, group 4 at 31 weeks, group 5 at 35 weeks and group 6 at 55 weeks while the control group (group 1) of similar size to groups 2 to 6 was subjected to a normal commercial treatment for laying stock.

4. In all the experimental groups the onset of sexual maturity occurred normally, but only one or two eggs were laid before laying ceased under the influence of the treatment.

5. Laying re‐started when the hens were fed on a normal diet and production rapidly rose to a high level.

6. Groups 1, 2 and 3 differed little in the total number of eggs produced up to 72 weeks of age.

7. In all experimental groups there were fewer very small, small and medium eggs than in the control group.

8. It is suggested that the use of a low‐calcium diet before the onset of lay may have advantages which could be exploited on a commercial scale.     

Automatic weighing of individual laying hens in aviary housing systems

1. This study investigated when and where body weight and flock‐uniformity should be determined in an aviary system by using automatic weighing systems.

2. An Individual Poultry Weighing System (IPWS) was developed to record time, duration, location and body weight of visits of individual hens to 4 weighing scales.

3. The number of hens that visited the weighing scales per 3 h period varied from less than 10 during the dark‐period to more than 60 during the light‐period.

4. The average number of visits per individual hen was 1–4 and the average number of successful weighings per hen was 0–6 during the light‐period.

5. Body weight showed a diurnal rhythm: the difference between the maximum body weight at night and the minimum body weight in the morning was 63 g.

6. The location of the scales influenced number of visits, number of weighings, mean body weight, flock‐uniformity and duration of visits.

7. Body weight per 3 h period did not differ between hens which were individually recognised and those which were not.

8. Flock‐uniformity was 2–6% higher during the light‐period if it was based on weighings of identified hen visits.

9. The average duration of the visits to the scales in the middle of the feeding tier during the light‐period was 63 s.

10. Of all the hens that visited the scales during a 24 h period, 54% visited them only once.

11. Automatic weighing systems without individual hen recognition can deliver reliable management information on mean body weight and flock‐uniformity in aviary systems if the weighing scales are located on the feeding tier in the middle of the house and if they are used during the light‐period.     

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.     

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.     

Effect of increasing cellulose in diets fed as crumbles or mash on the food intake and weight gains of broiler and Leghorn chicks

1. Two‐week‐old broiler and Leghorn cockerels were fed on diets containing 0, 100, 200, 300, 400, 500 or 600 g cellulose/kg in either crumble or mash form for 4 weeks.

2. Intake of the mash form of the cellulose‐diluted diets and associated body weights were less than those associated with the equivalent crumble diets which may have been due to decreased palatability of the former.

3. Broilers were unable to compensate for dietary dilution with cellulose by increasing food intake sufficiently to maintain nutrient intake with either mash or crumbled diets at any dilution.

4. At 100 g cellulose/kg for the mash diets and 100 and 200 g/kg for crumbled diets, Leghorns increased volume ingested by as much as 40% and maintained body‐weight gain and nutrient intake.

5. The results could be of value in designing feeding programmes for egg‐and meat‐type pullets.     

Ovarian morphology and rates of ovarian follicular development in laying broiler breeders and commercial egg‐producing hens

1. Ovaries from a light‐bodied egg laying strain and a broiler breeder strain were compared at 26 and 82 weeks of age.

2. The rate of lay in both strains was lower in the older hens. The 82‐week‐old hens were subdivided into good and poor layers: the poor layers produced eggs at about half the rate of the good layers.

3. The yellow‐yolky ovarian follicles in both strains were smaller, more numerous and more closely ranked in hierarchies in 26‐week‐old hens than in 82‐week‐old hens.

4. No marked differences were seen between the strains at 26 or 82 weeks of age in the sizes, numbers or hierarchical arrangements of yellow‐yolky ovarian follicles.

5. The ovaries from 82‐week‐old good and poor layers from both strains contained similar numbers of yellow‐yolky follicles.

6. After feeding a fat‐soluble dye, the number of days over which eggs containing dye were laid did not differ between 26‐, 52‐ and 113‐week‐old hens from an egg laying strain. However, fewer eggs with dyed yolks were laid by the older hens.

7. These observations suggest that the decrease in egg production with age is due initially to a reduction in the rate of recruitment of yellow‐yolky follicles. Towards the end of the laying year it may also be due to an increased incidence of follicular atresia, internal ovulation and the production of membraneous or soft shelled eggs.     

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.     

Effects of relocation on production in caged layers

1. Two experiments were conducted to determine the effects on laying performance of relocating caged hens at 30, 42 and 54 weeks of age.

2. In experiment 1 with hens caged individually, treatment groups comprised relocated hens given 5 new neighbours and hens not relocated but given 0, 2 or 4 new neighbours.

3. In experiment 2 with hens housed two per cage, treatment groups comprised relocation with or without that hen which shared the cage before the move.

4. In both experiments relocated hens laid fewer eggs in the week following social reorganisation.

5. Relocated hens in experiment 1 ate less food in the week following the shift at 42 weeks of age than did hens not moved. In experiment 2 in which all hens were moved, food consumption was not affected.     

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,carcase composition and profitability of meat chickens given pellets,mash or free‐choice diet

1. Equal numbers of 21‐d‐old male and female meat chickens were given their dietary ingredients either mixed and presented as pellets or mash, or as separate ingredients presented on a free‐choice basis, to determine whether presentation method caused any differences in growth, carcase composition or profitability to 42 d of age.

2. The proportions of ingredients eaten by the chickens given a free choice varied widely during the first 56 h of the trial. Thereafter, the proportions did not vary widely and birds given the free choice ate approximately ½ of their intake as whole wheat, ? of their intake as concentrate (high protein meals plus vitamin and mineral premixes), and 1/7 of their intake as whole sorghum each week for the three‐week trial period.

3. The nutrient composition of the free‐choice diet selected by the birds over the trial period averaged 12.09 MJ ME/kg feed, 210 g/kg crude protein, 14 g/kg calcium and 7 g/kg phosphorus.

4. At the end of the trial the average live body weights of the birds differed significantly according to method of feeding, in the descending order of pellets > mash > free choice.

5. The empty gizzard weight of birds differed significantly according to the method of feeding, in the descending order of free choice > mash > pellets.

6. The plucked empty bodies of birds given the free choice had a significantly lower concentration of crude protein than the plucked empty bodies of birds fed on mash or pellets. There were no significant differences between the treatments in the plucked empty body concentrations of fat, calcium or phosphorus.

7. Financial analysis indicated that free‐choice feeding was more profitable than feeding mash or pelleted diets to broiler chickens by 3.6% and 33.4% respectively.     

Effects of nutrient concentration and dietary presentation on performance of dwarf hens

1. Diets containing 170 or 190 g protein/kg and 10.9 or 11.7 MJ ME/kg in all combinations were offered to dwarf hens in two dietary presentations: a complete mash or a form in which part of the protein and calcium contents were presented as soyabean meal pellets and limestone grit respectively.

2. Egg production and egg mass output were higher with the 190 g protein/kg diets.

3. Lower‐energy diets gave better egg production, while higher‐energy diets containing 190 g protein/kg improved food conversion efficiency.

4. Separation of protein and calcium constituents tended to give better egg production, food conversion efficiency, shell thickness and egg mass output.     

Bone structure and breaking strength in laying hens housed in different husbandry systems

1. Bone structure and breaking strength were measured in hens that had been housed throughout a laying year in battery cages or in Perchery, Naturel or Litter and Wire husbandry systems.

2. Battery caged hens had the poorest bones, as assessed by measurements of cancellous bone volume, radiographic density, cortical thickness and three‐point breaking strength.

3. Humeri from birds in the Litter and Wire system were less dense radiographically and weaker than those from Perchery or Naturel birds but leg bone characteristics were similar with these three systems.

4. There were no differences in bone characteristics between birds in Perchery and Naturel systems.

5. There were strong correlations between radiographic densities and strengths of contralateral humeri and tibiae over all husbandry systems. Humerus structural and strength characteristics may be the best criteria of osteoporosis in hens.

6. It is concluded that the extent of movement allowed by different husbandry systems affects structural bone loss and bone strength in laying hens.

7. It is further concluded that the breaking strength of a hen's bone is closely related to morphometric measures and radiographic density of its structural components.     

Thermoregulation at high ambient temperature in genetically fat and lean broiler hens fed ad libitum or on a controlled‐feeding regime

1. Hens of lines divergently selected for fatness and leanness, fed either ad libitum or on a controlled regimen, were compared for susceptibility to heat stress.

2. The rate of increase in deep‐body (rectal) temperature during exposure to 32°C was used as the index of thermoregulatory ability. Comb and foot surface temperatures were measured as indicators of peripheral vasomotor tone.

3. Because body temperature control depends on the balance between heat production and heat loss, heat production was measured to determine whether fat line hens had a higher heat production, which they would then have to dissipate.

4. During the first hour of heat exposure, rectal temperature in the ad libitum‐fed birds increased twice as rapidly as in the corresponding lean line sample and 6 times more rapidly than in the control‐fed fat‐line group.

5. Surface temperatures of comb and foot increased from 27°C to 37°C within the first hour at 32°C, with no effect of either genotype or feeding regimen on rate of increase.

6. Heat production was unrelated to genotype but was reduced by 23% by controlled feeding, largely because of the reduction in body weight.

7. The results demonstrated that ad libitum‐fed fat‐line birds are susceptible to heat stress and that this is related not to increased heat production, but to a decreased ability to lose heat. Elevation of blood viscosity by plasma triglycerides is suggested as a causal factor.     

Effect of body weight loss and feeding regimen on the performance of moulted breeder layers

1. The effects of body weight loss (0.20, 0.25 or 0–30) during the period of food withdrawal and the subsequent feeding of cracked grain for 3 weeks, pullet grower ration for 3 weeks or layer ration immediately after the period of food withdrawal and their interactions on the second cycle performance of breeder layers were investigated.

2. Hens losing 0.30 of their initial body weight (BWL) produced more hatching eggs and chicks than those which lost 0.20 BW.

3. Hens fed on cracked grain produced fewest non‐hatching eggs, most chicks and the most efficient food utilisation.

4. The interactions showed that hens which lost 0.20 BW and were fed on layers ration produced most eggs. When number of chicks hatching was the criterion then hens losing 0.25 to 0.30 BW which were fed on cracked grain for 3 weeks gave the best performance.     

Egg discolouration effects of including screw‐press cottonseed meal in laying hen diets and their prevention

The egg discolouration effects of including a screw‐press cottonseed meal (CSM), containing 68.2 g residual lipid/kg, 290 mg cyclopropenoid fatty acids (CPFA)/kg and 1226 mg free gossypol/kg, in laying hen diets at 300 g/kg were examined.

2. Discolouration prevention methods included treating the meal with ferrous sulphate heptahydrate (FSH), in solution or as crystals, at a 4:1 weight ratio of iron to free gossypol (experiment 1), and reducing its residual lipid (CSL) content to 4.2 g/kg by hexane extraction (experiment 2).

3. In freshly laid eggs, no discolouration was observed when hens were fed a CSM‐based diet containing 250 mg free gossypol/kg and 87 mg CPFA/kg in experiment 1, but slightly brown yolks were produced in experiment 2.

4. Storage of the eggs at 22°C led to yolk mottling, an effect believed to be the initial stages of the brown yolk discolouration.

5. Storage of the eggs at 5°C resulted in enhancement of the brown yolk discolouration, apricot discolouration on surfaces of most yolks and pink albumen discolouration. These effects were prevented when the CSM was extracted with hexane. Apricot yolk and pink albumen discolourations were also produced when hens were fed a non‐CSM diet containing crude CSL at 20.5 g/kg.

6. Dietary CSL increased egg fat saturation, altering the ratios of stearic to oleic, palmitic to palmitoleic and heptadecanoic to hepta‐decenoic fatty acids.

7. Treatment of CSM with FSH reduced the slight brown yolk discolouration in fresh eggs (experiment 2) and the yolk mottling in warm‐stored eggs. Both in solution and as crystals, FSH prevented the enhancement of brown yolk discolouration in cold‐stored eggs, leaving most eggs with apricot yolk and pink albumen discolourations.

8. Treatment of CSM and CSL with FSH reduced the CPFA‐related effects on yolk fat saturation, and the colour and pH changes in cold‐stored eggs.

9. Exposure of yolks to ammonia vapour provided a useful test to predict the development of the gossypol‐related brown discolouration in stored eggs.