Studies on the incorporation of triticale in diets for growing chicks

1. The classical ME value of triticale varied from 12.305 to 13.778 kJ/g or 11.819 to 13.016 kJ/g corrected for N‐retention depending upon method of calculation.

2. Substituting triticale for maize, weight for weight, but not on a iso‐nitrogenous basis, in a groundnut oil cake (GNC) starter diet improved weight gain (P < 0.05) when the substitution exceeded 75% without affecting the protein efficiency ratio (PER).

3. A similar substitution in a soybean oil meal diet, improved weight gain (P < 0.05) at 50% or more but PER declined (P < 0.05).

4. The net protein utilisation and protein retention efficiency values of the diets in which maize protein was replaced by triticale protein were significantly reduced.

5. The maize‐GNC diet was equally limiting in methionine and lysine while the triticale‐GNC diet was not.

6. The growth and food efficiency obtained with a triticale‐GNC diet was higher (P < 0.01) than with the maize‐GNC diet but not with a maize‐GNC supplemented with fish meal and methionine.

7. It is concluded that triticale could quantitatively substitute maize in the starter diets.     

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.     

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.     

Evidence that the eumelanin restrictor genes (Co) and (Db) are present in the genome of the Buff Rock bantam

1. An investigation was conducted among the progeny from crosses between Buff Rock and Light Sussex bantams, and between Buff Rock and Gold‐Pencilled Hamburgh bantams in order to ascertain whether the eumelanin restrictor genes Columbian (Co) and Dark‐brown (Db) were present in the genome of the Buff Rock.

2. The Light Sussex and Gold‐Pencilled Hamburgh bantams used in this study were known to be Co/ Co db⁺ / db⁺ and co⁺ / co⁺ Db/ Db respectively.

3. In both F₂ generations the least eumelanin restricted segregants were as the parent mated with the Buff Rock, thus demonstrating the Buff Rock bantam tested to be Co/ Co Db/ Db, or possess similar alleles at these loci.

4. The Buff Rock bantam male was found to be heterozygous for a eumelanin inhibitor gene which appears to be dominant white (I).     

A mathematical representation of the Ovulatory cycle of the domestic hen

1. The ovulatory cycle of the domestic hen (Gallus domesticus) was postulated to be the result of the interaction of two independent systems.

2. A circadian system was postulated to control the restriction of ovulation to an 8‐h period of the day under conventional 14 h light: 10 h dark regimes.

3. The final phase of follicular maturation was postulated to commence after ovulation of the preceding ovum in the hierarchy.

4. Ovulation was postulated to occur when a mature follicle was present in the ovary during the appropriate phase of the circadian‐linked system.

5. The predicted times of oviposition were within the standard error of the observed times of oviposition under 21‐, 24‐ and 28‐h photoschedules.

6. It was concluded that this hypothesis for the control of the ovulatory cycle of the hen is consistent with current knowledge.     

A comparison of the energy and nitrogen metabolism of broilers selected for increased growth rate,food consumption and conversion of food to gain

1. Calorimetric measurements were made on 5‐week‐old male chickens sampled from the third generation of three lines selected for either increased live‐weight gain (W), food consumption (F), or food conversion efficiency (E). A control line (C) was also measured.

2. Food intake and food conversion ratio were greater (P<0.05) in the F line than in the E and C lines.

3. Metabolisability of the diet was 0.8% higher in the E line than in the other lines.

4. Metabolisable energy (ME) intake and heat production were greater (P<0.05) in the F line than in the E and C lines, and energy balance was greater (P<0.05) in the F than in the W and E lines.

5. During starvation, excreta energy and heat production were greater (P < 0.05) in the F than the other lines.

6. Availability of ME (net energy) was the same (85%) for all lines but calculated daily maintenance energy requirements (kJ ME/kgW) were W, 860; F, 937; E, 796 and C, 810.

7. By 9 weeks the F line contained more fat and less water than lines E and C.     

Effects of food intake regulation on the energy metabolism of laying hens

1. The effects of dietary energy restriction on the energy metabolism of post‐peak‐of‐lay hens of two hybrid layer strains were studied by indirect calorimetry.

2. Starving and resting rates of heat production (SHP and RHP) were measured, over 1‐d periods, at intervals during a 25‐week period in which the experimental birds were individually restricted to 80% of their previous energy intake ad libitum.

3. In both strains mean RHP per bird was about 7% lower in the restricted birds than in controls fed ad libitum, but when RHP was expressed in terms of metabolic body size (kg^0.75) the two groups did not differ.

4. Mean SHP per bird was about 18% lower in the restricted birds of both strains than in the corresponding controls; the decrease in SHP per kg^0.75 was 12%.

5. Heat increment of feeding and calculated maintenance energy were higher, and net availability of metabolisable energy for maintenance and production was lower, in the restricted than in the control groups.

6. Gross efficiencies of egg production, in terms of both mass and energy, increased in the restricted birds.

7. Live‐weight and total carcass energy after 25 weeks of restriction were respectively about 15% and 30% lower in the restricted groups of both strains than in the groups fed ad libitum.     

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.     

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.     

Chocolate: A sex‐linked recessive plumage colour mutant of the domestic fowl

1. A mating between Black Orpington bantams produced, in addition to blacks, a single female in which the black colouration was replaced by dark chocolate.

2. A mating of the chocolate‐coloured female with a black male, F₂ and backcross matings demonstrated that the chocolate phenotype is caused by a recessive sex‐linked gene to which I assign the symbol ?CHOC.

3. A mating of ‘chocolates’ inter se yielded all chocolate offspring.     

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.     

Defective egg production in a population of dwarf white leghorns 1

1. The incidence of defective eggs during the first 60 weeks of age increased with time due to significant increases in broken and membranous eggs in a population of dwarf White Leghorn hens.

2. The production of double‐yolked eggs/100 hen d, high during the initial weeks of lay, rapidly declined and disappeared by 30 weeks of age.

3. The frequencies of broken, membranous and soft‐shelled eggs were significantly correlated with each other and with the frequency of multiple daily ovulations indicating a common aetiology for these defective egg types.

4. Double‐yolked eggs were produced by the heavier, earlier‐maturing pullets in the population.

5. Normal egg production in dwarf White Leghorns may be enhanced by reducing the incidence of defective eggs.     

Welfare of broiler breeder and layer females subjected to food and water control during rearing: Quantifying the degree of restriction

1. A factorial experiment was conducted with females of two broiler breeder and one layer strains. The birds were fed ad libitum or restricted and were provided with free or limited access to water to simulate commercial rearing practices.

2. There was little difference between the broiler breeder strains except in body weight at 16 and 18 weeks of age.

3. Food intake relative to body weight was higher in the broiler breeders compared with the layer strain.

3. The degree of restriction was defined as the food intake of re‐stricted birds as a proportion of the estimated intake of birds of the same body weight fed ad libitum. The value declined from 0.60 to 0.45 during the rearing period.

5. In the ad libitum treatments broiler breeders drank more than layers, whereas when restricted, layers drank more than broiler breeders.

6. Water intake was 2.50 times higher in restricted compared with ad libitum‐fed layers and 1.25 times higher in restricted than ad libitum‐fed broiler breeders, with free access to water.     

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.     

The influence of sample size on the choice of method and interpretation of incubation experiments

1. An equation relating batch size to between‐treatment differences has been adapted for hatchability studies and its implications for research considered.

2. Very large egg batches are required to detect small improvements in the hatchability of good hatching strains.

3. Small‐scale laboratory studies on hatchability are best confined to strains and species of low hatchability in which larger between‐treatment differences may be expected.

4. The results of hatchability studies should always be subjected to tests of statistical significance.

5. There is a strong case for studying continuous variates in the laboratory before proceeding to large‐scale hatchability studies.     

Effects of changes in photoperiod and feeding opportunity on the performance of two breeds of laying hen

1. ISA Brown and Shaver 288 hens, fed ad libitum, were given a 5‐h increase or a 2, 5 or 10‐h decrease in photoperiod at 215 d of age. Hens of both breeds were also maintained on constant 10, 13 or 18 h photoperiods. Other groups had their photoperiod increased from 8 to 13 h, or were held on constant days but had their access to food limited to 8 h per day.

2. Both breeds on ad libitum feeding exhibited curvilinear rate of lay and egg output, and linear food intake, responses to photoperiod change. Shaver hens reduced their egg output and rate of lay to a greater extent than ISA Brown hens when photoperiod was decreased.

3. In both breeds the beneficial effect on egg production of the 5‐h increase in photoperiod was less than the adverse effect of the 5‐h decrease.

4. The influence of light change per se generally had a greater effect on performance than the influence of feeding opportunity, but significant effects of changing feeding opportunity were demonstrated.

5. The reduction in mean rate of lay and egg output following a reduction in photoperiod was partly caused by some birds ceasing lay, but all birds showed some decrease in both variates     

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.     

Hydrogenated oil decreases tissue concentrations of n‐6 polyunsaturated fatty acids and may contribute to dyschondroplasia in broilers

1. In a factorial design of dietary treatments, male Ross broilers were given diets containing soyabean oil, hydrogenated soya‐bean oil (as a source of trans‐fatty acids) or feed fat with either 0 or 300 μg of added D‐biotin/kg.

2. Growth to 28 d was not influenced by the dietary treatments.

3. Length of tibiotarsal bones was reduced (P<0.05) and severity of leg bone cartilage lesions, characteristic of dyschondroplasia, was highest (P<0.05) in broilers fed on diets containing hydrogenated soyabean oil.

4. Feeding hydrogenated soyabean oil lowered (P< 0.05) the concentrations of C₂₀:_4n6 and the ratios of C_20:4n6/C_18:2n6 in liver and growth plate cartilage.

5. Growth plate cartilage from birds affected with dyschondroplasia contained lower proportions of prostaglandin precursor fatty acids compared with normal growth plate.

6. It is speculated that an inhibition of prostaglandin biosynthesis brought about by the presence of trans‐fatty acids might contribute to the occurrence of lesions similar to dyschondroplasia.     

The effects of dietary intake and of dietary concentration of copper sulphate on the laying domestic fowl: Effects on laying performance and tissue mineral contents

1. Sixty white hybrid (Shaver 288) laying hens were subjected to three main dietary regimens for 5 d: ad libitum feeding of control and CuSO₄‐supplemented diets, force‐feeding these same diets to the same intake as that of the ad libitum control diet and pair‐feeding the control CuSO₄‐free diet to intakes equivalent to those of supplemented diets.

2. Final body weight of the force‐fed birds was significantly greater than of the other groups. Egg number and weight were significantly reduced as food intake decreased.

3. Liver weight per unit body weight was significantly increased and oviduct and ovary weights/kg body weight were significantly reduced by force‐feeding. As food intake decreased kidney and gizzard weights per unit body weight were significantly increased.

4. The concentrations and total contents of Cu and Zn in liver were significantly increased in the ad libitum and force‐fed groups.

5. Force‐feeding CuSO₄‐supplemented diets, which eliminated difference in food intake, confirmed that CuSO₄ per se affected tissue weights and mineral concentrations as distinct from effects due to the reduced food intake associated with increasing dietary CuSO₄.     

Effectiveness of dietary 25‐ and 1‐hydroxycholecalciferol in combating tibial dyschondroplasia in broiler chickens

1. Three experiments were carried out to determine the effects of feeding diets containing different concentrations of cholecalciferol, 1 a‐hydroxychole‐calciferol (1‐HCC), 25‐hydroxycholecalciferol (25‐HCC), 1,25‐dihydroxycholecalcif‐erol (1,25‐DHCC) and ascorbic acid on the incidences and severities of tibial dyschondroplasia (TD) at 3 weeks of age in male broiler chicks.

2. In experiment 1, replacing 75 μg cholecalciferol/kg with the same weight of 25‐HCC decreased significantly (P<0.01) the incidence of TD from 65 to 10%.

3. In experiment 2, the incidence of TD in the control group was lower, but feeding amounts of 25‐HCC up to 250 μg/kg had a linear effect on the incidence of TD that was significant at P=0.06. There was no effect or interactions with dietary addition of 250 mg ascorbic acid/kg. Dietary addition of 5 μg 1‐HCC/kg decreased TD incidence from 21 to 5%, though the effect was not significant (P>0.1).

4. TD incidence in experiment 3 was too low to determine an effect of 25‐HCC or 1,25‐DHCC on TD incidence, though in this, as in both other experiments, the severities of TD lesions were always lower with diets containing cholecalciferol metabolites.

5. Hypercalcaemia was not observed after feeding up to 250 μg 25‐HCC/kg in either experiments 2 or 3.

6. It is concluded that 25‐HCC may be an effective practical means of improving broiler leg health by alleviating the incidence and severity of TD.