Three open issues on Avian Influenza – H5, H7, H9 against all odds

1. Scientific knowledge and certainties on Avian Influenza infections have been completely shaken following the emergence and spread of three “odd” subtypes, namely H5, H7 and H9.

2. These subtypes, particularly H5N1, also have public health implications in addition to causing animal disease.

3. Control of infection in animals and in-depth analysis of virus antigenic and genetic properties largely rely on the veterinary community which requires better weapons that will be efficacious only if revised tactics are developed and vigorously applied.     

Respiratory phagocytes are implicated in enhanced colibacillosis in chickens co-infected with influenza virus H9N2 and Escherichia coli

1. The aim of this study was to determine the most likely time interval after infection with influenza virus H9N2 for co-infection with Escherichia coli to cause colibacillosis, the importance of lung load of E. coli and the involvement of respiratory phagocytes.

2. Specific pathogen free chickens were inoculated intranasally with 10⁶EID₅₀ of influenza virus or uninfected. After specified time intervals, 10⁷ CFU E. coli or phosphate-buffered saline was inoculated. The presence of lesions, the number of respiratory phagocytes in the respiratory lavage fluid and the E. coli load in the lung were determined after different time intervals.

3. Compared with the number of lesions in chickens receiving only E. coli inoculation, the number lesions in co-infected chickens were increased at 0- and 3-d time intervals, but reduced in the groups at 6- and 9-d intervals between co-infection.

4. At 1–3 d after E. coli inoculation, the number of lesions chickens was correlated with the number of respiratory phagocytes harvested and related to the E. coli load in the lungs at 5 d.

5. These results suggest that the lesions caused by E. coli in chickens were increased within a 0–3 d interval following H9N2 virus inoculation and that this effect is related to the number of respiratory phagocytes.     

Effect of nephropathogenic infectious bronchitis viruses on renal function in young male broiler chickens

1. The acute effects of challenge with Australian T‐strain infectious bronchitis virus (IBV) on renal function were evaluated, following primary vaccination in 1‐d‐old male broilers.

2. Challenge with T‐strain IBV decreased body weight and induced kidney hypertrophy and kidney asymmetry.

3. Haematocrit was reduced in birds challenged with the Australian T‐strain IBV and plasma uric acid was elevated in unvaccinated birds exposed to the IBV challenge.

4. Challenge with T‐strain IBV caused significant increases in urinary water losses, accompanied by decreased urine osmolality and increased fractional excretion of sodium, calcium and potassium.

5. Vaccination at 1‐d‐old with Vic S‐strain IBV provided a limited degree of protection against an heterologous challenge with T‐strain IBV at 15 d of age.     

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.     

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.     

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.     

Immune-modulatory effects of dietary Saccharomyces cerevisiae cell wall in broiler chickens inoculated with Escherichia coli lipopolysaccharide

1. An experiment was conducted to study the effect of yeast (Saccharomyces cerevisiae) cell wall (YCW) supplemented in diets of broiler chickens challenged with Escherichia coli lipopolysaccharide (LPS).

2. One-day-old broiler chicks were randomly distributed into 24 cages (6 replicate cages; 8 birds/cage) and were inoculated with 0 or 1 mg/kg body weight E. coli-LPS (d 4 and 9) and 0 or 500 mg YCW/kg feed, resulting in a 2 × 2 factorial arrangement of treatments. Experimental diets did not include coccidiostats, in-feed antibiotics or enzymes.

3. On d 21, the inoculation of E. coli-LPS reduced weight gain and feed intake and increased feed conversion ratio (FCR) of birds, an effect maintained until 28 d. In contrast, chickens given diets with YCW improved the FCR at both 21 and 28 d of age.

4. E. coli-LPS challenge reduced the relative weight of bursa of Fabricius, except when chickens were given YCW, which resulted in an interaction. Supplementation of broiler diets with YCW exacerbated the cellular immune response as measured by the delayed cutaneous hypersensitivity response test.

5. The results of this study suggested a benefit on feed efficiency when YCW was added to diets fed to broiler chickens challenged with E. coli-LPS. Part of the mode of action of YCW might be related to better maintenance of immune status in response to microbial challenge.     

Protection of sheep by vaccination against experimental challenge with Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona

AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and L. interrogans serovar Pomona.

METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney-cross lambs, aged 9–11 weeks, were randomly allocated to a vaccinated group and a control group. Vaccinated lambs each received two 1.5-mL S/C doses of a multivalent leptospiral and clostridial vaccine, 4 weeks apart, and animals in the control groups received the same dose of saline. Groups of 12 vaccinated and 12 control lambs were randomly selected in each study for challenge with serovars Hardjo or Pomona. Challenge was initiated 16 weeks following the second vaccination with three daily doses of live leptospires by intranasal and conjunctival routes. Following challenge, urine samples were collected weekly for 6 weeks, for dark field microscopy and leptospiral culture; 6 weeks after challenge the lambs were slaughtered and kidneys collected for leptospiral culture.

RESULTS: In lambs challenged with serovar Hardjo, 8/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive for leptospires following culture, compared with 0/12 lambs in the vaccinated group (p=0.001). In lambs challenged with serovar Pomona, 9/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive following culture, compared with 0/12 lambs in the vaccinated group (p<0.001). Prevention of renal colonisation and urinary shedding, expressed as the prevented fraction, was 100 (95% CI=61.7–100)% and 100 (95% CI=68.3–100)% against challenge with serovars Hardjo and Pomona, respectively, at 4 months after vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE: Use of a multivalent leptospiral and clostridial vaccine demonstrated protection against challenge from New Zealand strains of serovars of Hardjo and Pomona 4 months after vaccination in lambs first vaccinated at 9–11 weeks of age. Further studies are required to assess the duration of immunity against challenge in sheep.     

Depletion of florfenicol and florfenicol amine residues in chicken eggs

1. The aim of this study was to develop a suitable method for the analysis of florfenicol (FF) and its metabolite florfenicol amine (FFA) in chicken eggs and to determine FF and FFA residue depletion in eggs of laying hens.

2. The analytes were extracted from yolk, albumen and whole egg by phosphate buffer and ethyl acetate. Following purification, samples were analysed by high-performance liquid chromatography.

3. Fifty laying hens were divided into 5 groups, and each hen received doses of 20 mg/kg FF: Group 1 (received a single oral dose by gavage); Group 2 (a single intramuscular dose); Group 3 (a single subcutaneous dose); Group 4 (multiple oral doses for 3 d) and Group 5 (multiple oral doses for 5 d).

4. Limits of detection and of quantitation values were 1.94 and 6.45 g/10⁹ g (ppb) for FF, respectively, and 0.48 and 1.58 ppb for FFA, respectively. Relative standard deviation values of intra-day and inter-day variation below 11% also confirmed the usefulness of the method for analysing FF and FFA in eggs.

5. From the first day of both oral and parenteral administration, FF and FFA were detected at 0.1% and 0.08% of dosage, respectively, and 57% of the drugs were eliminated from the egg yolk. Elimination time of FF was 8 d in Groups 1, 2 and 3; 9 d in Group 4 and 10 d in Group 5.     

Protective effect of ubiquinone (coenzyme Q9) on ascites in broiler chickens

1. The effect of ubiquinone (C0Q9) on ascites in broiler chickens was investigated.

2. The commercial broilers were divided into 2 groups of 100 birds each; CoQ9‐treated group and non‐treated group.

3. The chickens were grown in a positive‐pressured house with double high efficiency particulate air filtered intakes and exhaust, and thus were strictly isolated from infectious agents.

4. The chickens (15 to 21 d old) were exposed to cold stress in order to induce ascites.

5. The number of birds with ascites in the C0Q3‐treated group was significantly lower than in the non‐treated group.

6. Survival and production rates were better in the CoQ^‐treated group than in the non‐treated group.     

Immunoresponsiveness of fast‐growing chickens as influenced by feeding regimen

1. Immunoresponsiveness and disease resistance were measured in broiler males maintained on ad libitum feeding throughout or on alternate‐day feeding. Alternate‐day restrictions were started 1 and 2 d after hatch so that on any one day there were chicks fed and fasted.

2. Severity of response to E. coli challenge as measured by lesion scores, and mortality was greater for chicks fed ad libitum than those fed on alternate days. For chicks fed on alternate days, lesion scores were lower for those without access to feed for the 24‐h period immediately after challenge.

3. Spleen weights, the indicator of response to marble spleen disease virus challenge, were higher for chicks fed ad libitum than those fed on alternate days.

4. Antibody response to sheep red blood cell antigen was not affected by feeding regimen.

5. Ratios of heterophils to lymphocytes were higher for chicks given access to feed for the previous 24‐h period than for those fasted during the previous 24‐h or those that had been fed ad libitum.

6. Results of this experiment suggest that for alternate‐day feeding programs, vaccination be administered on the day that chicks are not fed.     

Calorimetric measurements of the energy and nitrogen metabolism of Japanese quail

1. Respiration calorimetry measurements were made over 4 d on normally‐fed groups of 10 male or 10 female quail during three periods commencing at 12, 19 and 26 d of age. Carcass compositions were determined on groups of birds of each sex at 2 and 5 weeks of age.

2. Expressed per unit body weight, food and metabolisable energy (ME) intake and weight gain decreased between 2 and 3 weeks of age, but remained constant thereafter.

3. No differences were observed between sexes for any variable measured. Efficiency of utilisation of ME for energy retention was only 0.33. This was mainly because the majority of energy was retained as protein tissue.

4. Nitrogen (N) retention (g/d) increased with increasing dietary N intake but when expressed as a proportion of N intake, declined from 0.46 at 2 weeks to 0.33 at 4 weeks. Fat retention increased substantially during week 4.

5. Carcass analyses showed that fat, protein and ash were higher for quail at 5 weeks than at 2 weeks of age. At 5 weeks carcass fat was only 60 g/kg.     

Effect of two microbial phytases on mineral availability and retention and bone mineral density in low-phosphorus diets for broilers

1. The efficacy of supplementation of a low-phosphorus (low-P) maize–soyabean meal diet for broiler chickens with two different microbial (fungal and bacterial) phytases was examined.

2. Broiler chickens received a low-P maize–soyabean meal diet containing either no phytase or one of the two phytases included at one and two times the manufacturer's recommended inclusion level for 21 d.

3. Titanium dioxide was included in the diets as an indigestible marker. Excreta were collected quantitatively from d 18 to 21, and at the end of the study the birds were killed and ileal digesta and leg bone samples collected.

4. No differences were observed for body weight gain and feed intake or apparent metabolisable energy (AME) among all dietary treatment groups.

5. Dietary phytase supplementation improved the apparent retention of Ca, Na and Cu and ileal phytate P absorption from 32% to 44% across inclusion levels.

6. Bone mineral density (BMD) was improved for both phytases across inclusion levels by, on average, 9% for the tibia and 13% for the femur.

7. Dietary phytase supplementation of the low-P diet improved apparent ileal digestibility of serine, glycine, valine, isoleucine, tyrosine, histidine, lysine and arginine.

8. When the results from the present study were combined with the results from other similar published studies and analysed statistically, factors such as dietary P and Ca concentration, as well as bird breed and age, rather than the type or activity of microbial phytase, had the greatest impact on the extent to which dietary supplementation improved P and Ca retention.

9. More work is required to explain the interrelationships between the multiple factors influencing the efficacy of phytase on the availability of dietary minerals.     

Effects of direct-fed microbial supplementation on broiler performance,intestinal nutrient transport and integrity under experimental conditions with increased microbial challenge

1. The effects of Aspergillus oryzae- and Bacillus subtilis-based direct-fed microbials (DFM) were investigated on the performance, ileal nutrient transport and intestinal integrity of broiler chickens, raised under experimental conditions, with increased intestinal microbial challenge.

2. The first study was a 3 × 2 factorial experiment, with 3 dietary treatments (control (CON), CON + DFM and CON + antibiotic growth promoter) with and without challenge. Chicks were fed experimental diets from 1 to 28 d, while the challenge was provided by vaccinating with 10 times the normal dose of commercial coccidial vaccine on d 9. In a second experiment, two groups of 1 d-old broilers, housed on built-up litter (uncleaned from two previous flocks), were fed the same CON and CON + DFM diets from 1 to 21 d.

3. The challenge in the first experiment reduced performance, but no differences were observed among dietary treatments from 8 to 28 d. The challenge reduced the ileal epithelial flux for D-glucose, L-lysine, DL-methionine and phosphorus on d 21. Epithelial flux for D-glucose, L-lysine and DL-methionine were increased by DFM. Ileal trans-epithelial electrical resistance (TER) was increased in challenged broilers fed DFM, although this was not observed in unchallenged birds as indicated by a significant interaction.

4. Ileal mucin mRNA expression and colon TER were increased, and colon endotoxin permeability was reduced by DFM on d 21 in the second experiment.

5. It was concluded that the addition of DFM in the diet improved the intestinal integrity of broiler chickens raised under experimental conditions designed to provide increased intestinal microbial challenge.     

A comparison of the energy and nitrogen metabolism of starved ducklings and chickens

1. Respiration chambers were used to measure, over 24 h, the heat production of groups of starved ducklings from two batches and of starved broiler chickens from one batch up to 28 and 39 d of age, respectively. Duration of starvation prior to measurements and ambient temperature were adjusted according to the age of the birds.

2. Respiratory quotient of 0.705 for chickens was significantly lower than that of 0.713 for ducklings.

3. Starvation heat production (kJ/d) of ducklings was 804 kgW^0.70 compared with 675 kgW⁰‘⁷⁴ for chickens. There were differences in heat production between the two batches of ducklings used when expressed per kg body weight (W).

4. Ducklings lost more body weight, body fat and protein than chickens during starvation. Gaseous ammonia‐N was on average 9% of N excreted by ducklings and 4% of N excreted by chickens.     

Heterophil/lymphocyte ratio as a selection criterion for heat resistance in domestic fowls

1. Two experiments were conducted to examine the Heterophil/Lymphocyte ratio (H/L) as criterion for selection for resistance to heat stress and some aspects of general resistance in domestic fowls.

2. The first experiment on a small sample (n = 64) of light breed Iraqi local fowls showed that this ratio could be used as an indicator of heat stress resistance.

3. The second experiment on a large sample (n= 1160) of heavy parent stock confirmed the results. It showed that there was a different H/L ratio for the two strains and that there was much individual variability in the H/L ratio within‐strain that could be utilised for individual selection for heat resistance.

4. The H/L ratio was highly heritable; Resistant and Sensitive groups, defining all individuals with an H/L ratio over the upper 95% confidence limit as ‘Sensitive’ and those below as ‘Resistant’, produced progeny with significantly different H/L ratios.

5. There were indications of differences in mortality between the progeny of the Resistant and the Sensitive groups.

6. The H/L indicator could be used as a criterion to select for heat stress resistance.     

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.     

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.     

Assessing the effect of administering probiotics in water or as a feed supplement on broiler performance and immune response

1.?Two routes of probiotic administration in broiler farms, in water and in feed, were compared using 360 one-day-old male broiler chickens. Controls received no probiotics or antimicrobials. The water group received a probiotic preparation at a rate of 0·5 g/l, and the feed group received it at an inclusion rate of 1 g/kg.

2.?Performance of broilers in terms body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) improved when probiotic was provided via drinking water, compared to the control and feed groups. Probiotic administration reduced plasma cholesterol and triglyceride concentrations.

3.?Spleen (28 and 42 d) and bursa (42 d) relative weights were influenced by method of probiotic administration, which also improved T-cell dependent skin thickness response to phytohaemagglutinin (PHA) injection. The effect of challenge by dinitrochlorobenzene (DNCB) depended on the method of probiotic administration.

4.?The method of probiotic administration can influence the performance and immune competence of birds, and administration via drinking water appears to be superior to the more conventional in-feed supplementation method.     

Evaluation of bone strength,keel bone status,plumage condition and egg quality of two layer lines kept in small group housing systems

1. The aim of the present study was to determine the influence of large (54 or 60) and small (36 or 40) group sizes and tiers of the small group housing system “Eurovent German” on tibia and humerus bone breaking strength, keel bone status, plumage condition and egg quality for two commercial layer lines, Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB), at the same stocking density (890 or 830 cm²/bird).

2. In 4 consecutive trials, 4752 hens were recorded for keel bone status. Evaluation of plumage condition was made for 1440 hens and bone breaking strength was recorded for 1200 hens. A total of 4962 eggs were analysed for internal and external egg quality traits. Analyses involved 30 small group compartments per trial.

3. The layer line had a much more pronounced influence on humerus breaking strength than on tibia breaking strength.

4. Plumage condition, particularly on the neck, was positively correlated with humerus breaking strength in both layer lines.

5. An average of 34% of LB and 23% of LSL hens showed keel bone deformities, with higher proportions of slight deformities.

6. Slight keel bone deformities, rather than moderate to severe, increased significantly during the laying period.

7. Stocking density had no influence on bone breaking strength, keel bone status and egg quality traits.

8. LB layers had a 1.4-fold higher humerus, but only a 1.06-fold higher tibia breaking strength compared to LSL layers.

9. Tibia breaking strength was significantly affected by the interaction of group size and layer line. LSL layers in small groups had lower tibia breaking strengths than those of the large groups.