Thermoneutral zone and resting metabolic rate of growing white leghorn‐type chickens

1. Metabolic rate was determined once a week in pullets from commercial flocks of the local White Leghorn strain from the age of 1 d to 13 weeks.

2. The equations relating minimal resting metabolic rate and body weight were: for body weights of 40 to 163 g Y ‐ 1–83 W ^0.986, and for 163 to 1 200 g Y = 11.64 W ^0.623, where Y = O₂ consumption (ml/bird h) and W = body weight (g).

3. The relationship between lower critical temperature (T_d) and age may be described by two equations: for pullets of 1 to 21 d of age Y = 35 ‐ 0.286 X, and for 21 to 70 d of age Y = 63.3 X^{‐ 0.254}, where Y = T _d(°C) and X = age (d).

4. T_d related to body weight is also described by two equations: for body weights of 40 to 163 g Y = ’42 ‐ 1.18 W^0.480 , and for 163 to 800 g r = 42 ‐ 3.60 W^0.260

5. These equations could be used to calculate the T_d on a day‐to‐day basis related to age or body weight.     

Variation among individual white‐leghorn hens in the concentration of minerals in the albumen and yolk content of their eggs

1. The mineral composition of the albumen and yolk was determined in several eggs from each of a number of individual hens from the same White‐Leghorn strain. X‐ray fluorescent spectrometry was used to undertake two independent series of analyses. A total of 8 minerals (calcium, chlorine, iron, magnesium, phosphorus, potassium, sodium, sulphur) were included in the analyses of the yolk and the same minerals, but excluding iron (which is present in only small amounts), in the albumen.

2. There was considerable variation between individuals in the mineral concentration in their eggs (coefficients of variation ranged between 3.8% for sodium to 19.9% for calcium in the albumen, and between 4.3% for phosphorus to 11.8% for iron in the yolk).

3. At the same time, the moderately high repeatability of mineral concentration (t = 0.4?0.6) in successive eggs from the the same hen for several of the minerals analysed is indicative of some positive control by the hen of the mineral composition of her eggs.

4. There was a highly significant correlation (P≤ 0.001) between the mean concentration of potassium in the albumen and the hatchability of the eggs, supporting the claim that a deficiency of potassium in the egg could be the basis of some failures in hatchability.

5. The study also revealed variation among individual birds in the concentration of iron in the yolk which was negatively correlated (P≤0.01) with hatchability. No clear basis could be suggested for this variation among individual birds.     

The incidence of breast‐blister down‐grading in broiler chickens

1. A survey was conducted into down‐grading due to breast blisters at a large processing plant.

2. The relationships between incidence of down‐grading and age, body weight, sex, size of rearing site and its distance from the processing plant, and various weather conditions during the rearing period of each flock were examined using regression analysis.

3. Age and body weight and rearing site size were the only factors significantly correlated with amount of blistering.     

Effects of feeding deoxynivalenol‐contaminated oats on reproduction performance in white leghorn hens

1. The effect of feeding trichothecene‐contaminated diets with graded concentrations of deoxynivalenol ranging from 120 to 4900 μg/kg to groups of laying hens was investigated.

2. Food intake, weight gain and egg production were not affected by mycotoxin administration. No significant differences were found between groups.

3. The overall results from the hatching tests did not reveal any significant differences in fertility, hatchability or perinatal mortality, which could be explained by the mycotoxin content in the diets.

4. Body weight at hatching and viability of the chicks were not affected by the mycotoxin concentrations in the diets.

5. The incidence of chick developmental anomalies was increased in the mycotoxin‐administered groups compared to controls. Minor malformations were the dominating anomalies and included unwithdrawn yolk sac and delayed ossification. The most frequent major malformations were cloacal atresia and cardiac anomalies.     

An energy response curve for a commercial white leghorn laying‐strain cross

1. Individually‐caged White Leghorn hens, 235‐d‐old, were given daily metabolisable energy (ME) intakes ranging from 707 to 1321 kj for 8 two‐week periods. Energy was the first limiting nutrient, in those cases where the differences in egg output between treatments were sufficiently large.

2. Body weight, egg number and egg weight all responded (P < 0–001) to energy intake, and as judged by regression analyses, these responses had stabilised by the fifth period.

3. For a near‐maximum egg output of 48 g/bird d, the difference between the ME requirement of the average bird and of the flock, estimated from linear and curvilinear models respectively, was 20–5%.

4. The ME requirement (Y, kj/bird d) of the average bird for egg production (E, g/bird d) and maintenance of metabolic body size (kg W°. ⁷⁵ ) corrected to an ambient temperature of 22 °C is given by the equation, Y = 440W ^0.75 + 8.96 E     

Cardiovascular effects of angiotensin‐II in chickens

1. Mature WL cockerels with permanent cannulae in brachial artery and vein were restrained in an isolated sling. Blood pressure (BP) and heart rate (HR) were continuously recorded. When the chickens were habituated to the sling, injections began. In each experiment the cockerels were injected intravenously 6 times at 6 min intervals.

2. In the first experiment 6 injections of 0.5 nmol[Aspl,Val5]ANG‐II/kg body weight were given.

3. In the second experiment oxytocin (OT) antagonist ([d(GH2)5‐O‐Me‐Tyr2,Thr4,Tyr9,Orn8]VT) at a dose of 2 nmol/kg, was injected for the first 3 and 0.5 nmol ANG‐II/kg for the last 3 injections. Such OT‐antagonist pretreatment completely abolishes the vasodepressor (VDP) response to neurohypophysial pep‐tides in chickens.

4. Injections of ANG‐II resulted in a biphasic effect on BP, an initial brief fall followed by a prolonged rise. During the hypotensive phase, tachycardia developed which turned into bradycardia as the hypertensive phase appeared. No tachyphy‐laxis of the VDP effect of ANG‐II was evident with repeated injections.

5. OT‐antagonist pretreatment had no effect on the VDP response to ANG‐II.

6. These results suggest that, unlike relaxation of chicken aortic ring in in vitro preparations, there is no tachyphylaxis of the VDP response to ANG‐II, in vivo. Furthermore, the neurohypophysial peptides are not involved in the VDP effect of ANG‐II because pretreatment with an OT‐antagonist had no effect on it. The baroreflex buffers the effects of ANG‐II on vascular tone by affecting HR.

7. As ANG‐II is secreted during hypovolaemia, the biphasic haemodynamic response peptides may have a compensatory role following volume contraction.     

A selection experiment on a white leghorn strain under Ahemeral light‐dark Cycles

1. Selection was carried out for increased ovulation frequency in two flocks; under ahemeral (9 generations of selection) or normal (8 generations) light‐dark cycles.

2. By the use of an ahemeral regime, the barrier to progress imposed by the limit of one ovulation in each light‐dark cycle was evaded.

3. Both flocks achieved a considerable increase in oviposition frequency but so far there has been little evidence of any advantage in this respect due to the ahemeral regime.

4. There was a marked correlated decrease in egg weight in both flocks.     

Selection for food conversion in broilers: Body composition of birds selected for increased body‐weight gain,food consumption and food conversion ratio

1. Body composition was determined in 9‐week‐old chickens sampled from four lines selected either for increased body‐weight gain (line W), for increased food consumption (line F), for decreased food conversion ratio (line E), or at random (line C), after three, four and five generations of selection.

2. After five generations of selection the proportions of carcass water (678 g/kg) and protein (187 g/kg) were highest in line E and lowest (636, 180 g/kg respectively) in line F. The proportion of fat was lowest (83 g/kg) in line E and highest (134 g/kg) in line F.

3. Lines W and C were similar and intermediate to lines E and F for all the carcass constituents.

4. There was more fat in females (115 vs 98 g/kg) and less protein (177 vs 190 g/kg) and water (652 vs 665 g/kg) than in males.

5. Line differences in carcass composition were not appreciably altered if birds were killed at equal weight rather than equal age.     

The development of a sex‐linked slow‐feathering white leghorn strain by gene transfer from an Indian indigenous breed

1. Breeding techniques were used to transfer an economically important physiological character dependent on a single pair of alleles from an indigenous breed (Kadakanath) to the White Leghorn.

2. The mating procedure used to develop a sex‐linked, slow‐feathering strain of White Leghorn by these means is described and it is shown that using the simplest genetic and breeding techniques productivity can quickly be improved.     

Increased small intestinal fermentation is partly responsible for the anti‐nutritive activity of non‐starch polysaccharides in chickens

1. The mechanism of the anti‐nutritive activities of soluble non‐starch polysaccharides (NSPs) in broiler diets was investigated with emphasis on the inter‐relationship between viscosity and fermentation along the gut. Isolated soluble NSP were added to a control diet to effect high gut viscosity, and in vivo depolymerisation of the NSP was achieved using a commercial glycanase.

2. Addition of soluble NSPs significantly (P<0.01) increased gut viscosity, reduced the AME of the diet and depressed the growth and FCE of the birds. Enzyme supplementation of the NSP‐enriched diet reversed the adverse effects, increasing (P< 0.01) weight gain, FCE and AME. Comparisons of the viscosities (mPa) in birds fed on the NSP‐enriched diet and the same diet supplemented with enzyme were respectively: 11–9 v. 2–3 in the duodenum; 78–3 v. 4–4 in the jejunum and 409–3 v. 10–8 in the ileum.

3. Caecal volatile fatty acid concentration was markedly (P<0.01) elevated by enzyme supplementation, whereas ileal fermentation was inhibited.

4. Microscopic examination revealed that, among birds fed on the NSP‐enriched diet, there had been extensive small intestinal fermentation, which was eliminated by the enzyme supplementation.

5. Addition of a synthetic antibiotic (Amoxil) had no beneficial effects.

6. The current study demonstrated that increased fermentation occurs in the small intestine when a large amount of viscous NSPs is present in the diet and this is detrimental to the performance and well‐being of poultry.     

Time‐budgeting in meat chickens grown commercially

1. Observations were made for 1‐h periods on 19 birds aged from 27 to 50 d in a commercial meat chicken flock. Data were collected on the frequency, the total proportion of time spent in different behaviour patterns, and sequencing of behaviour.

2. Sixty‐four percent of time was spent lying. Individuals engaged in up to 41 separate lying bouts, which suggests that the birds were restless rather than resting.

3. Interrupted rest was sometimes caused by birds standing on each other; on other occasion it may have served to increase heat loss.

4. The frequency and duration of eating and drinking amongst individuals was variable. Neither dust‐bathing nor agonistic behaviour were observed and their absence may reflect the lack of importance of these behaviour patterns in meat chickens.     

Differences in egg‐shell quality among the Sinai Bedouin fowl,the commercial white leghorn and their crossbreds

1. A comparison of egg‐shell characteristics was made among the Sinai breed (a desert inhabiting strain), the commercial White Leghorn and their reciprocal crossbreds.

2. The Sinai egg was smaller and its shell thicker and stronger than the Leghorn egg. All the differences were statistically significant.

3. Shell thickness and strength of Leghorn eggs were in accordance with values predicted on the basis of egg mass, while those of the Sinai and the two crosses were considerably higher than predicted.

4. The apparent differences in mean egg mass between Sinai and Leghorn breeds did not explain the differences in egg‐shell quality, neither did the shape index which was very similar among all breeds.

5. The findings suggest that the differences in egg‐shell properties are of a genetic origin.

6. The thick, strong and less permeable egg‐shell of the Sinai breed may reflect adaptations to its arid environmental origin and to incubation in the open.

7. These genetically‐determined egg‐shell characteristics might serve in a future selection for improved egg‐shell quality in poultry.     

The contribution of anorexia to reduced growth in zinc‐deficient chickens

1. It was shown, using a paired‐feeding technique, that the growth depression in zinc‐deficient chicks was largely caused by the greatly reduced consumption of the deficient diet.

2. Chicks receiving a zinc sulphate solution directly into the crop ate an amount of zinc‐deficient diet similar to that of the zinc‐sufficient diet eaten by the control chicks; palatability was thus ruled out as the cause of the anorexia.

3. Only chicks receiving the zinc‐deficient diet displayed signs of zinc deficiency.     

Susceptibility of two commercial single comb white leghorn strains to calcium‐induced urolithiasis: Efficacy of dietary supplementation with dl‐methionine and ammonium sulphate

1. Susceptibility to calcium‐induced urolithiasis was assessed in pullets of two commercial SCWL strains (A and B) reared together from 5 to 18 weeks of age on diets containing 10 g/kg calcium (normal calcium: NC) or 35 g/kg calcium (high calcium: HC).

2. Kidney damage was not observed in pullets reared on NC diets. For pullets fed on HC diets, strain A developed significantly greater kidney asymmetry, a higher incidence of gross kidney damage and a higher incidence of uroliths than strain B.

3. Supplementing the HC diet with 6 g/kg DL‐methionine significantly reduced the incidence of calcium‐induced gross kidney damage and urolith formation in both strains. Ammonium sulphate (5.3 g/kg) was significantly more effective than dl‐methionine in reducing calcium‐induced kidney damage.

4. Neither dl‐methionine nor ammonium sulphate caused a measurable metabolic acidosis. Neither supplement consistently affected water consumption or manure moisture.     

Dexamethasone‐induced alterations in glucose tolerance and,insulin, glucagon and adrenaline responses during the first month in white leghorn chicks

1. Alterations in glucose tolerance and, insulin, glucagon and adrenaline responses in dexamethasone (DXM)‐treated (induced hypocorticalism) chicks have been evaluated chronologically during the first month of development of White Leghorn chicks.

2. Alterations in glucose tolerance and, insulin resistance and glucagon and adrenalin responses in dexamethasonised chicks were recorded. Control chicks too displayed differential glucose tolerance and, insulin, glucagon and adrenaline responses on a chronological basis.

3. The observations suggest increased insulin and adrenaline sensitivity in the first fortnight and gradually increasing glucagon response in the second fortnight in neonatal chicks.

4. Furthermore, increased insulin sensitivity and attenuated glucagon responsiveness was also associated with DXM‐induced hypocorticalism.     

Prevalence and incidence of Newcastle disease and prevalence of Avian Influenza infection of scavenging village chickens in Timor-Lesté

A longitudinal study to monitor prevalence and incidence of antibodies against Newcastle disease (ND) virus and prevalence of antibodies against Avian Influenza (AI) virus in scavenging village chickens was conducted in 20 villages within 4 districts of Timor-Lesté. A total of 3600 blood samples was collected from 1674 individual birds in 300 household chicken flocks during three sampling periods (December 2008-February 2009, March-May 2009, and June-August 2009). The mean interval between household visits was 101.6±1.9 days. None of the birds enrolled in the study was vaccinated against ND or AI. A haemagglutination inhibition (HI) test was used to determine antibody titres against ND virus and a competitive ELISA and HI tests were used to detect antibody against AI virus. The bird-level ND seroprevalence pooled across all samplings (adjusted for clustering by households) was 4.4% (95% CI 3.5-5.2). The bird-level ND seroprevalence in each of the three sampling periods (adjusted for clustering by household) was 3.0% (95% CI 2.0-4.0), 6.6% (95% CI 5.1-8.0) and 3.6 (95% CI 2.5-4.6), respectively. A total of 12.6% individual birds tested ND seropositive at least once over the total study period (95% CI 10.5-14.7). The flock-level ND seroprevalence (at least one bird tested had antibodies against ND virus) pooled across all samplings was 15.9% (95% CI 13.5-18.3). A total of 35.3% flocks had a minimum of one bird being ND seropositive at least once over the study period. The bird-level incidence rate for the period between the first and the second sampling and between the second and the third sampling was 5.6 (95% CI 4.1-7.5) and 0.5 (95% CI 0.5-3.8) per 10,000 bird-years-at-risk, respectively. A total of 1134 serum samples from the last sampling period between June and August 2009 was tested for antibodies against AI virus. Only 4 samples tested Influenza A positive, indicating a bird-level seroprevalence level for Influenza A of 0.4% (CI 0.0-0.7%). These Influenza A positive samples were further tested for HI antibodies against AI virus subtypes of H5N1, H5N3, H7N3 and H9N2, but all tested negative, suggesting that the influenza antibodies in those four birds resulted from exposure to low pathogenic AI viruses of different H subtypes. Our results indicate that village chickens in Timor-Lesté are exposed to ND virus; there was a higher risk of infection during the early months of 2009 than either immediately prior or subsequent to this. No evidence of infection of village chickens with H5, H7 or H9 AI viruses was detected in this study.     

Effect of temperature of wet extrusion on the nutritional value of full‐fat soyabeans for broiler chickens

1. An experiment was conducted to determine the temperature for wet extrusion of full‐fat soyabeans (FFS) needed to produce maximum chicken performance.

2. FFS were either unprocessed or extruded at 5 different temperatures (118°, 120°, 122°, 126° and 140°C) in a wet extruder. Diets were prepared with the different FFS, and a diet prepared with soyabean meal (SBM) was included as a control. The 7 experimental diets were fed to individual groups of 40 chickens each, for a period of 35 d. Trypsin inhibitor activity (TIA), urease activity (UA), and protein solubility in potassium hydroxide (PS) were measured in all FFS and in the SBM.

3. Diets prepared with raw FFS and FFS extruded at 118° and 120°G resulted in significandy lower body weights and in pancreatic hypertrophy; maximum growth rate was obtained with FFS extruded at 122° and 126°G, while minimum pancreas weight was seen in chickens fed FFS extruded at 140°C.

4. Although TIA, UA, and PS all decreased with increasing temperature of extrusion, TIA provided the best prediction of the feeding value of soyabeans for chickens.     

Time course of oxidative phosphorylation in liver mitochondria of chickens fed on high‐protein diet

1. Progressive alterations in oxidative phosphorylation of liver mitochondria were followed for 14 d in growing chickens fed on either semi‐purified low (7%) or high (61%) protein‐energy diet. Hepatic mitochondrial oxidative phosphorylation rates were assessed polarographically with pyruvate + malate as substrates.

2. The ADP:O values were reduced significantly 4 d after the feeding of a high‐protein‐energy diet, when compared with those in chickens fed on a low‐protein‐energy diet, whereas the state 3 oxidation rates in chickens fed on a high‐protein‐energy diet from day 6 to 14 were significantly lower than those in low‐protein‐fed chickens.

3. No changes in sensitivity of mitochondrial ATPase activity to oligomycin, expressed as % of total ATPase activity, were observed among chickens fed for 21 d on diets with various protein concentrations though the FoF₁‐ATPase activity, expressed per mg protein, tended to decrease in chickens fed on high‐protein‐energy diet.

4. These results suggest that the reduced ADP:O values for liver mitochondria in the high‐protein‐fed chickens may not be involved in the degrees of integrity of the FoF₁‐ATPase.