Effects of a blend of essential oils and overcrowding stress on the growth performance,meat quality and heat shock protein gene expression of broilers

Overcrowding stress is common in the poultry industry. Chickens exposed to long-term stressful situations are characterised by welfare impairment and immunosuppression.

1. The present study evaluated the effects of a blend of essential oils (EOB; cinnamaldehyde and thymol) and stocking density on the performance, gut microflora, meat quality and physiological stress markers of broilers.

2. One-day-old Ross 308 male broiler chickens (n = 360) were allocated to 4 experimental groups from d 22 to 42. Each treatment had 6 replicates of 15 chicks. Two groups were subjected to a high stocking density (HSD) of 20 birds/m² and the other two groups were kept at a low stocking density (LSD) of 10 birds/m².

3. The results of this study indicate that overcrowding stress decreased growth performance parameters, blood immunoglobulin (Ig)G and heterophil:lymphocyte (H:L) ratio but increased IgA and IgM levels. HSD reduced water-loss rate and pH decline at 45 min post mortem in the breast muscle.

4. Essential oils supplementation elevated H:L ratio but decreased breast meat redness and pH₂₄.

5. Significant interactions between EOB and stocking density were observed for corticosterone (CS) level and mRNA levels of heat shock protein 70 (HSP70) in brain and heart. Although HSD increased CS and HSP70 when compared to LSD, the effects of the former were inconsistent with EOB supplemented diets.

6. In conclusion, dietary EOB supplementation could improve some of the biomarkers associated with overcrowding stress in broiler chickens.     

Identification of duck HSP70 gene,polymorphism analysis and tissue expression under control and heat stress conditions

1. This study was designed to characterise the duck heat shock protein 70 gene (HSP70) and identify sequence variation.

2. Chicken HSP70 sequence (GenBank: AY143693) was used as a template to design a primer pair to amplify partial duck HSP70 gene. Primers were subsequently designed with the duck HSP70 gene as a template to amplify the complete duck HSP70 sequence.

3. Twelve commercial Sanshui White ducklings were subjected to a heat stress experiment. Tissue samples were collected for RNA extraction and real-time PCR to analyse the expression mechanism of duck HSP70.

4. A DNA pool was constructed from three different species for single nucleotide polymorphism (SNP) screening. The genotypes of the identified SNPs were detected in 145 Sanshui White ducklings.

5. Duck HSP70 gene was identified and characterised (GenBank: EU678246) and shown to contain no introns. Fifteen variations were identified within the open reading frame. Quantitative real-time PCR results showed that the expression of duck HSP70 gene was tissue specific and the highest expression level was seen in pectoral muscle.     

Diminished gene expression of cardiac heat shock proteins in pulmonary hypertensive chickens

1. The relative expression of heat shock protein (HSP) genes (HSP60, HSP70 and HSP90) was performed using quantitative real-time PCR on tissue from the heart ventricles to investigate the effect of 3,5,3′-l-triiodothyronine (T₃)-induced pulmonary hypertension in broiler chickens.

2. The ratio of the right ventricle to total ventricle (index of pulmonary hypertension) was increased in the treated groups at 12 and 42 d of age compared to controls but was significant only at 42 d.

3. The HSP genes were expressed in the right and left ventricles of control but T₃-treated broilers at 12 and 42 d of age. The relative amounts of HSP60 and HSP90 gene expression in the right ventricle of treated groups were significantly increased at 12 d and decreased at 42 d of age compared to controls.

4. Variations of HSP60 and HSP90 mRNAs in the left ventricle were not significant. The relative amount of HSP70 mRNA expression in the right and left ventricles of treated groups was significantly decreased at 42 d of age compared to controls. HSP70 mRNA expression did not differ between the right and left ventricles at 12 d of age.

5. It is concluded that gene expression of HSPs (i.e. HSP60 and HSP90) was upregulated in the heart of chickens developing pulmonary hypertension syndrome, probably to delay the pathological process of disease. The right ventricle from hearts of pulmonary hypertensive chickens showed considerable reductions of HSP60, HSP70 and HSP90, which is evidence of a loss of compensatory responsiveness in dilated heart.     

The effect of heat treatment and enzyme supplementation on the nutritive value of barley for broiler chicks

1. The effect of heat treatment and enzyme supplementation on the nutritive value of barley was studied.

2. In only one experiment was weight gain significantly improved when the barley was heated.

3. Autoclaving barley at 120 °C for 30 min reduced dietary dry matter digestibility and treating the barley with dilute acid before heating had no effect on its nutritive value.

4. Supplementing diets containing commercial barley with a‐amylase produced slightly conflicting results in that there was an improved weight gain, food conversion efficiency and digestibility value in two of three experiments.

5. The digestibility and metabolisable energy values of a North American six‐row spring barley (Glacier) were significantly improved by enzyme supplementation.

6. The effect of the enzyme on diets containing a high amylose barley (Glacier Pentlandfield) was positive but not significant.     

Effect of acute heat exposure on triglyceride transfer to the preovulatory follicles of the laying fowl (Gallus Domesticus)

1. The effect of acute heat exposure on triglyceride (TG) transfer to preovulatory follicles was studied in the laying fowl.

2. Heat exposure of laying fowl resulted in a 1.1°C rise in body temperature, a 10‐fold increase in respiration frequency and mild hypocapnia and hypoxaemia.

3. Plasma and follicular tissue TG concentrations were not significandy affected by heat exposure, but plasma TG specific radioactivity decreased significantly and was negatively correlated with body temperature.

4. The transfer rate of TG to the preovulatory follicles was not affected significantly by hyperthermia.

5. We conclude that nutrient supply to the developing follicles is not compromised in acutely heat‐exposed laying fowl.     

Gene expression profile of IGF1 and MSTN mRNA and their correlation with carcass traits in different breeds of geese at 70 d of age

1. The expression of insulin-like growth factor-1 (IGF1) and myostatin (MSTN) mRNA in breast and leg muscle was quantified in 70-d-old Taihu and Wanxi geese by using a Multiplex Competitive Fluorescent–PCR method and the correlations between mRNA levels and carcass traits were analysed.

2. IGF1 mRNA expression in breast muscle in Taihu geese was significantly higher than that in Wanxi geese and the MSTN mRNA level in leg muscle in Taihu geese was significantly higher than that in Wanxi geese.

3. There was no significant difference in breast muscle MSTN or leg muscle IGF1 mRNA expression between the two breeds.

4. Within the same breed, the IGF1 mRNA expression in leg muscle of male geese was significantly higher than that in female geese, and MSTN mRNA expression in leg muscle was significantly higher than that in breast muscle.

5. There was no difference in the IGF1 mRNA expression between tissues.

6. There was a positive correlation between IGF1 mRNA and MSTN mRNA and a negative correlation between IGF1 mRNA expression of breast muscle and leg muscle ratio.

7. In Wanxi geese, MSTN mRNA expression in leg muscle was negatively associated with body weight and leg muscle weight.     

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.     

The effect of heat stress on GHR,IGF-I,ANT, UCP and COXIII mRNA expression in the liver and muscle of high and low feed efficiency female quail

1. A study was conducted to test the hypothesis that feed efficiency (FE) correlated with the expression of genes from the somatotropic axis and mitochondrial genes involved in energy production, and that the environment to which the birds are exposed influenced the expression of such genes.

2. Quails were divided into High-FE and low-FE groups and maintained in a comfortable or heat stress (HS) (38°C for 24 h) environment to evaluate changes in insulin-like growth factor I (IGF-I), growth hormone receptor (GHR), adenine nucleotide translocator (ANT), uncoupling protein (UCP) and cytochrome oxidase subunit III (COX III) messenger ribonucleic acid (mRNA) expression in liver and muscle tissues.

3. High-FE quails (0.28 g/g) presented a higher final body weight, greater weight gain and a better feed conversion ratio than low-FE birds (0.18 g/g). High-FE birds showed greater IGF-I mRNA expression in the liver and muscle and greater GHR mRNA expression in the muscle.

4. Environmental effects only affected GHR expression in the liver, with quails under comfortable conditions exhibiting greater GHR expression than quails subjected to HS.

5. There was a significant interaction between FE and environmental temperature on ANT mRNA expression in the liver. The greatest ANT mRNA expression was observed for high FE-birds that remained under comfortable conditions.

6. In the liver, UCP mRNA expression did not differ among the quails and was not affected by environment or efficiency. However, comparisons of the low- and high-FE birds revealed higher levels of UCP mRNA in the muscle of low-FE birds.

7. COX III mRNA expression in the liver was dependent on environmental temperature and FE. Higher COX III mRNA expression was observed in animals that remained under comfortable conditions, and high-FE birds exhibited higher expression levels compared to low-FE birds.

8. These results suggest a correlation between IGF-I, GHR, ANT, UCP and COX III gene expression and FE and that environmental temperature could affect the expression of some of these genes.     

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.     

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.     

Battery cage shape: Its effect on diurnal feeding pattern,egg shell cracking and feather pecking

1. Battery cages 460 mm in depth (deep) were compared with 305 mm cages (shallow); the two shapes provided equal areas per bird.

2. More eggs were produced per hen housed from 30 to 70 weeks in the shallow cages; the difference approached significance.

3. The pattern of feeding activity over the day was significantly more U‐shaped in the shallow cages; this pattern accords more closely with physiological requirements.

4. Feather damage caused by pecking was slightly but significantly more severe in the deep cages at 70 weeks.

5. The proportion of cracked eggs (collected from 60 to 70 weeks) was significantly lower in the shallow cages.

6. The arrangement of the hens was such that within the shallow cages a higher proportion of birds was present in the front half.

7. It is suggested that some of the advantages conferred by the shallow cage may be related to the greater accessibility of the food trough.     

The use of rapeseed meals and a mustard seed meal as a protein source in diets for laying pullets

1. Three experiments with laying pullets were carried out in which rapeseed meals (B. napus and B. campestris) and a mustard seed meal (B. juncea) formed 12% of the diet.

2. Dietary rapeseed had no effect on the onset of lay when fed from 17 weeks of age but caused a delay when fed from 10 weeks of age: changing to a control soyabean diet for the laying period resulted in normal egg production.

3. Diets containing B. napus but not B. campestris consistently depressed egg production and reduced egg weight in one experiment. Mustard seed meal did not affect performance.

4. Significant number of eggs with a “fishy” taint were laid by brown‐egged birds fed on a diet containing rapeseed.

5. Thyroids of birds fed on rapeseed meal diets during the laying period were significantly heavier than those of birds fed on diets containing mustard seed or soyabean.

6. The enlargement of the thyroid gland is probably related to the oxazolidinethione content of the rapeseed.     

Protein and energy metabolism in two lines of chickens selected for growth on high or low protein diets

1. Genetic adaptation was investigated in broilers selected for seven generations on a normal (A) or a low (B) protein diet.

2. Protein and energy metabolism were studied in males from these selected lines fed on a diet of intermediate protein content.

3. All selected birds retained more nitrogen than those studied 10 years previously.

4. There was no difference in nitrogen retention between groups, although relative growth rate of group B birds was higher.

5. Heat productions relative to gross energy intake were 0.38 (group B) and 045 (group A). Energy retentions relative to gross energy intake were 0.39 (group B) and 0.35 (group A); the difference being primarily due to higher fat retention in group B.

6. Using a common maintenance requirement for metabolisable energy, group B utilised metabolisable energy for growth (0.78) better than did group A (0.71).

7. At 53 d of age plasma glucose (10%) and insulin (50%) were higher in group B than in group A.     

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.     

Effect of egg composition on hatchability and on growth and slaughter characteristics of meat-type chicks

1.?Using the so-called TOBEC (Total Body Electrical Conductivity) method, which allows the determination of egg composition in vivo, correlations between egg composition, hatchability and hatched chicks’ development were studied.

2.?A total of 1500 hen eggs (Ross-308) were measured by TOBEC, and eggs with extremely high (10%, n = 150), extremely low (10%, n = 150) and average (10%, n = 150) electrical conductivity values were chosen for further investigation.

3.?During the incubation period, it was observed that eggs with high electrical conductivity had a significantly higher mortality than eggs with low electrical conductivity.

4.?It was observed that both the increase in electrical conductivity at the same egg weight, and the increase in egg weight at the same electrical conductivity resulted in an increase in the hatching weight.

5.?It was found that the dry matter, protein and fat content of the chicks hatched from eggs with low electrical conductivity was higher at hatching than that of the chicks hatched from eggs with high electrical conductivity.

6.?At 42 d of age the liveweight of cocks and pullets hatched from eggs with low electrical conductivity was 3·2 and 8·2% higher than the liveweight of cocks and pullets hatched from eggs with high electrical conductivity.

7.?Because of the higher liveweight at slaughter, there was a significant superiority of the chicks hatched from eggs with low electrical conductivity in the case of the examined carcase traits at slaughter.

8.?Similar tendencies were found also in the ratios of carcase variables to liveweight, but the between group differences were not statistically significant in this case.

9.?Based on the results it was concluded that TOBEC seems to be a useful method for separating eggs with different composition.

10.?This could be a good starting point for further in vivo investigations in order to clarify the effect of egg composition on hatchability and further development.     

Ligation of caeca improves nitrogen utilisation and decreases urinary uric acid excretion in chickens fed on a low protein diet plus urea

1. The effect of the ligation of the caeca on nitrogen utilisation and nitrogen excretion was examined in conventional chickens fed a diet containing 50 g protein/kg plus urea.

2. Ligation of the caeca significantly improved nitrogen balance and utilisation by up to more than 2 times as much as those of controls (P< 0.05).

3. The treatment significantly decreased uric acid excretion by 77 mg nitrogen/day (P< 0.01) and also total nitrogen excretion (P<0.05): the former decrease almost explained the latter.

4. No effect of the ligation of caeca on urea and ammonia excretion was observed.

5. It is concluded that nitrogen metabolism in chickens is affected by possible changes in caecal fermentation by preventing entry into the caeca of substances from urine and digesta.     

Fat deposition and heat production as responses to surplus dietary energy in fowls given a wide range of metabolisable energy: Protein ratios

1. Female broiler fowl between 21 and 42 d of age were given diets with apparent metabolisable energy (AME) contents ranging from 8 to 15 MJ/kg at each of two crude protein (nitrogen x 6.25; CP) contents (130 and 210 g/kg).

2. Food intake was measured daily for 21 d. Body composition was determined at 42 d and gains in body mass, protein, fat and gross energy calculated by comparison with a group analysed at 21 d. Heat production was calculated by difference between AME intake and energy gain.

3. Decrease of food mass intake with increased dietary AME concentration limited the increase in AME intake to about 25%, despite the near 2‐fold range of AME concentrations.

4. There was no effect of CP concentration on food mass intake. CP intake was directly related to CP: AME ratio.

5. When body weight differences were taken into account, heat production was independent of dietary AME concentration, but increased by about 8% on the higher‐protein diets.

6. There were strong linear correlations between dietary CP:AME ratio and carcase protein: energy ratio, carcase fat content and carcase protein content.

7. It was concluded that the growing fowl responded to dietary nutrient: energy ratio, and the associated differences in nutrient and energy intakes, by varying the rate of energy deposition as fat, without regulatory variation of energy dissipation as heat.     

Inheritance of body weight and rate of gain in Japanese quail

1. The effects of hatch date, location and sex on the body weight and rate of gain in Coturnix coturnix japonica were examined.

2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.

3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.

4. Weight gain was greater if illumination intensity up to 35 d was less.

5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.

6. Variance components and genetic parameters were estimated.     

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.     

A note on the effects of heat stress on carcass composition and adipose tissue cellularity of ducklings

1. The effects of heat exposure (36 °C) from 14 or 18 to 28 d of age on ducklings were assessed by comparison with pair‐fed or ad libitum‐fed controls at 22 °C. From 28 d all groups were fed ad libitum at normal temperature until samples were killed at 41 or 54 d.

2. At 28 d performance was similar in heat‐exposed and respective pair‐fed controls, but poorer than in ad libitum‐fed controls. Food intake and gain were less for heat‐exposed than for pair‐fed birds at 41 and 54 d (data combined).

3. Proportional fat pad size, adipose cell volume and number were less for all groups than for ad libitum‐fed controls at 41 d, but these differences largely disappeared by 54 d. Carcass fat varied little between groups.

4. Carcass moisture was less in heat‐exposed than in pair‐fed birds at 54 d and carcass protein greater at 41 d.