Effects of medium-chain fatty acids on performance,carcass characteristics,blood biochemical parameters and immune response in Japanese quail

1. This study had the aim of evaluating the effects of medium-chain fatty acids (MCFA) on performance, carcass characteristics, some blood parameters and antibody titre against sheep red blood cells (SRBC) in quail.

2. A total of 240 quail chicks were allotted to 4 treatments consisting of respectively 0, 1, 2 and 4 g/kg dietary MCFA.

3. There were no significant differences in body weight, feed intake and feed conversion ratio among treatments at different stages of the experiment.

4. MCFAs had no significant effect on breast, thigh, liver, spleen and bursa of Fabricius weight ratios. However, the relative weight of abdominal fat significantly decreased in quail receiving 0.2 and 0.4 MCFA as compared to other treatments.

5. Concentrations of low-density lipoprotein-cholesterol (LDL), triglycerides and total cholesterol were decreased and high-density lipoprotein (HDL)-cholesterol was increased in quail chicks receiving MCFA compared with control quail chicks. The concentrations of SRBC antibody were not statistically different among treatments.

6. It is concluded that MCFA significantly decreased LDL, triglycerides, cholesterol and abdominal fat and increased HDL in quail chicks.

     

Effects of trehalose supplementation on the growth performance and intestinal innate immunity of juvenile chicks

1. Trehalose is composed of two molecules of D-glucose joined by an α,α-1,1 glucosidic linkage and has antioxidative and anti-inflammatory effects. The present study investigated the effect of feeding a trehalose-supplemented diet on the growth performance, as well as the oxidative status and the intestinal innate immunity of juvenile chicks.

2. A total of 16 d-old male broiler chicks were used in this study: two groups of 8 birds were fed on a 0% (control) or 0.5% trehalose-supplemented diet for 18 d.

3. The mean body weight of the trehalose group was significantly greater than that of the control group, but feed efficiency was not altered by feeding the trehalose-supplemented diet. No differences in the levels of lipid peroxidation in skeletal muscle, liver and plasma were observed between the control and trehalose-supplemented groups. The mRNA levels of interferon-γ, tumour necrosis factor-like ligand 1A, interleukin-10, NADPH oxidase 4 and inducible NO synthase were significantly reduced by the trehalose supplementation.

4. Our results suggest that dietary supplementation with trehalose after hatching may have beneficial effects on the growth performance of juvenile chicks, probably by improving their intestinal innate immunity.

     

Efficacy of adsorbents (bentonite and diatomaceous earth) and turmeric (Curcuma longa) in alleviating the toxic effects of aflatoxin in chicks

1. A study was conducted to determine the efficacy of bentonite clay (BC), diatomaceous earth (DE) and turmeric powder (TUM) in alleviating the toxic effects of aflatoxin B₁ (AFB₁).

2. A total of 250 Ross-308 d-old male broiler chicks were assigned to 10 dietary treatments (5 replicates of 5 chicks) from hatch to d 21. Dietary treatments were: basal diet; basal diet plus AFB₁ (2 mg) or BC (0.75%), or DE (0.75%), or TUM (200 mg/kg curcuminoids) and different combinations of AFB_1, BC, DE and TUM.

3. Feed intake (FI), body weight gain (BWG) and feed gain (FG) of the birds fed on BC or DE separately were not different from control birds. Birds fed on TUM only had similar FI and FG but lower BWG than control chicks.

4. Aflatoxin B₁ reduced FI, BWG and serum concentrations of glucose, albumin, total protein calcium, but increased FG and relative liver and kidney weights. Chicks fed on the combination of AFB₁ and BC had similar FI and FG to control chicks. Chicks fed on the combination of DE and AFB₁ had lower FI (23.1%) and BWG (28.6%) compared with control chicks.

5. Chicks fed on the combination of TUM and AFB₁ also had decreased FI (26.2 %) and BWG (31%) compared with control chicks. Chicks fed on the combination of AFB₁, BC and TUM consumed significantly higher amounts of feed compared with chicks fed on only AF, but gained less when compared with control diet chicks.

6. Chicks fed on the combination of AFB₁, DE and TUM diet had poorer growth performance than those fed on AFB₁ alone. None of the combination diets reduced the severity of liver lesions.

     

Gender-related amino acid intake of adult wild Red-legged Partridge (Alectoris rufa)

1. The Red-legged Partridge (Alectoris rufa) is under an enormous hunting pressure. It is bred intensively in game farms. The hunting season is during the non-reproductive resting period when partridges are at maintenance conditions.

2. There is a lack of information about the amino acid (AA) composition of the natural diet of the adult birds in their habitat or differences in dietary AA composition related to gender. The objective of this work was to establish a first approach to the AA composition of the natural diet of adult wild Red-legged Partridge.

3. Food content in crops and gizzards of female and male birds hunted in the same hunting season and area was analysed for AA composition.

4. Females food had higher concentrations of individual essential AA (EAA) and non-essential AA (NEAA) than males.

5. There are important differences in the concentration of AA in the natural diet of wild females and males. It may be advisable to use diets differing in the proportion of individual AA in the game farms during the non-reproductive resting period.

     

Effect of Lonicera japonica extract on Mycoplasma gallisepticum in naturally infected broiler flocks

1. In this study, the effect of chlorogenic acid extract from Lonicera japonica Thunb. on Mycoplasma gallisepticum infections and the performance of broiler flocks was investigated.

2. A total of 360 Ross-308 broiler chicks taken from M. gallisepticum seropositive flocks were divided equally into three groups designated as control (nothing administered), antibiotic (Tylosin tartrate given for the first 3 d and d 20–22) and test group (chlorogenic acid extract given twice a day on d 16 and 22).

3. Broiler performance analysis, serological tests (slide agglutination), molecular identification (polymerase chain reaction) and histopathological examination were performed to detect M. gallisepticum.

4. The results show that chlorogenic acid not only increases live body weight but is also an alternative treatment option in M. gallisepticum–infected broiler flocks.

     

Changes in eggshell structure and predisposition of broilers to health problems: is there a common pathophysiology?

1. A study of broiler breeder eggs differing in eggshell matrix optical density was conducted to determine the association of eggshell structural quality and the risk of disease in broilers.

2. A total of 10 000 eggs from a broiler breeder flock were examined according to the pre-established criteria, and allocated to groups classified as having a high or low density shell matrix.

3. The eggs from respective groups were incubated and hatched in a commercial hatchery. Samples of unhatched eggs from each group were subjected to detailed examination to establish the cause of reproductive failure. First, quality chicks from each group were raised as separate flocks in a commercial broiler barn. Group performance, morbidity, and mortality were monitored throughout the growth period. All birds were processed in a commercial plant, and condemnation data were compiled.

4. There were significantly more unhatched eggs, and fewer quality chicks in the group classified as having a low density eggshell matrix, in comparison to the high-density group.

5. Embryo pathology accounted for a large proportion of the overall reproductive failure in both groups, with a large proportion of embryos showing anatomical anomalies. The eggs and embryos from the low-density eggshell matrix group were three times more likely to be infected.

6. Significantly higher production losses associated with mortality/morbidity, and condemnations of carcasses at processing were observed in broilers from the low-density eggshell group compared with the high-density eggshell group.

7. It is concluded that common metabolic/physiological changes in breeder hens associated with eggshell pathology may be also risk factors linked with predisposition of broiler chicks to some health problems.

     

Dietary but not in ovo feeding of Silybum marianum extract resulted in an improvement in performance,immunity and carcass characteristics and decreased the adverse effects of high temperatures in broilers

1. A total of 360 fertile eggs from a broiler breeder strain (Ross 308) were used for in ovo feeding (IOF) of 0, 100 and 200 mg/kg Silybum marianum water extract at 17.5 d of incubation.

2. After hatching, 240 chicks were transferred to the experimental cages. The diets consisted of two types; one of them without extract and the other one containing 100 mg/kg of Silybum marianum extract. Then chicks were exposed to elevated temperatures 4°C above optimum from 7 to 28 d of age for 4 h per d and after 28 d they were kept at optimum temperature. The chicks were divided into 6 treatments with 4 replicates as a completely randomised 2 × 3 factorial design.

3. There was no effect of IOF of Silybum marianum extract on hatchability, body weight (BW) of hatched chicks or hatched chick BW/initial egg weight ratio. Chickens fed on the diet containing the extract had the highest feed intake, daily weight gains (DWGs), final BW and lowest feed conversion ratio.

4. At 28 d, the weights of heart, spleen and bursa of birds in the treatment groups given extract were higher, but abdominal fat weights were lower. At 42 d in those fed extract in the diet, the weights of spleen and bursa were higher and abdominal fat weights were lower than the other groups.

5. No differences were observed between groups in body temperature before application of the higher temperature but at 21 d and 28 d the body temperature of chicks given the Silybum marianum extract was lower than the other treatments during the elevated temperatures.

6. In birds fed on the extract in the diet, HDL and cholesterol concentrations were lowest at 28 d, whereas blood glucose levels were higher in the other treatments. At 42 d the cholesterol concentration was significantly lower in birds given extract in their diet.

7. These results indicated that dietary feeding of Silybum marianum extract resulted in an improvement in performance, immunity and carcass characteristics and decreased the adverse effects of the higher temperatures, specifically in reducing blood fat reduction, but IOF of the extract did not have an effect.

     

The reproductive response of female ostriches to dietary protein

1. A study was conducted with breeding ostriches over two consecutive breeding seasons to determine their response to different concentrations of a well-balanced dietary protein.

2. Five concentrations of protein were fed to both females and males at an intake of 2.5 kg/bird d. The respective diets contained 75, 91, 108, 123 and 140 g protein/kg feed with energy held constant at 9.2 MJ metabolisable energy/kg feed.

3. Egg production (mean ± SE, 39.1 ± 3.6 eggs/female/season) was unaffected by dietary protein concentration. Similarly, no significant trends were found for the number of unfertilised eggs (9.1 ± 1.8), dead-in-shell chicks (8.2 ± 1.3), the number of chicks hatched (19.5 ± 2.5) and change in the mass of females (?16.3 ± 10.2 kg). Egg weight decreased linearly as dietary protein content increased.

4. Age of the ostrich female had a highly significant effect on the number of eggs laid, the number of chicks hatched, the number of dead-in-shell and infertile eggs produced per hen, as well as the mass change of female breeding birds, but did not affect the response of any of these variables to dietary protein content.

5. It was concluded that ostriches do not benefit from dietary protein contents greater than about 75 g/kg when this is fed at a daily total feed intake rate of 2.5 kg/bird during the breeding season.

     

Effect of cottonseed oilcake as a protein source on production of breeding ostriches

1. South Africa currently produces 70% of the world’s ostrich products. The profit margin of South African producers from the sale of ostrich meat, leather and feathers currently stands at 20%, 65% and 15%, respectively.

2. Local producers want to increase the production of ostrich products but keep production costs as low as possible. Maintaining optimal nutrition of breeding stock is necessary to increase the production of ostrich chicks, thereby decreasing the fixed costs per chick.

3. This research examined the impact on ostrich reproduction of replacing soya oilcake (SOC) as a protein supplement with cheaper cottonseed oilcake (CSOC). Although there are no data available on the impact of CSOC feed on ostrich reproduction, it is well known that gossypol, a naturally occurring toxin in cotton plants, negatively affects male reproduction in other monogastric species and that it may also reduce appetite.

4. Ninety-six breeding ostrich pairs were divided into two groups to compare the effects of diet (CSOC and SOC) during the breeding season on ostrich-breeding parameters. The replacement of SOC with CSOC had no significant effect on the number of total eggs produced (47.8 ± 5.3 versus 48.3 ± 5.1 per breeding pair, respectively) or infertile eggs (31.5 ± 3.9 versus 38.0 ± 5.2, respectively). Also, the number of dead-in-shell chicks did not differ significantly between groups (20.2 ± 3.3 versus 26.8 ± 3.8, respectively).

5. Even though none of these breeding parameters differed, the replacement of SOC with CSOC in the diets of breeding birds led to significantly more chicks hatching per hen from breeding birds fed on the SOC (36.1 ± 4.8) than the CSOC diet (17.2 ± 3.8).

6. Although it would thus seem that feeding breeding ostriches CSOC instead of SOC as a protein supplement will have a detrimental effect on chick production, more data are required to deliver a definitive answer.

     

Assessment of the effectiveness of head only and back-of-the-head electrical stunning of chickens

1. The study assesses the effectiveness of reversible head-only and back-of-the-head electrical stunning of chickens using 130–950 mA per bird at 50 Hz AC.

2. Three trials were conducted to compare both stunning systems: (a) behavioural assessment of return of consciousness, (b) insensibility to thermal pain, and (c) assessment of return of brain activity with visually evoked potentials (VEPs).

3. Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers.

4. Stunning across the back-of-the-head delayed the time to return of brainstem function compared to stunning with standard head-only electrodes. Additionally, back-of-the-head stunning produced a more prolonged period of electroanalgesia compared to head-only.

5. Based on examination of return of brain function with VEPs in hens, back-of-the-head stunning produced a shorter-lasting stun than standard head-only. However, even for standard head-only, the stun was notably shorter than previously reported. In some birds, brain function had returned within 9 s after the end of stunning.

6. The results suggest that some birds may recover consciousness prior to or during the neck cut. Based on these findings, back-of-the-head stunning and standard head-only stunning of hens should not be recommended without further development.

     

Influence of graded inclusion of white lupin (Lupinus albus) meal on performance,nutrient digestibility and intestinal morphology of broiler chickens

1. The aim of this study was to investigate the effect of white lupin (Lupinus albus) meal (WLM) addition on the intestinal viscosity, bird performance, nutrient utilisation and villi morphology of growing broiler chicks.

2. The experiment was conducted with 480 broiler chicks divided into 6 dietary treatments, including a maize-soybean meal control diet (CON) and 5 experimental diets containing 100, 150, 200, 250 and 300 g/kg WLM.

3. During the period from d 0 to 35, birds fed on 200 or higher WLM/kg were characterised by lower body weight gain and feed intake than CON. The use of 150 g of WLM/kg increased feed conversion ratio (FCR) compared to CON treatment. Apparent metabolisable energy corrected to zero N balance (AME_N) and apparent ileal digestibility of dry matter, ether extract, crude protein and starch, linearly decreased as WLM increased from 0 to 300 g/kg.

4. There was a quadratic effect of WLM dose on sialic acid excretion. A strong negative linear correlation was found between the excretion of sialic acid and AME_N. The viscosity of ileal digesta was linearly increased as WLM increased. The effect of WLM dose on ileum villus height (VH) was linear, while that on ileum villus area (VA) was quadratic. Both parameters decreased as WLM increased from 0 to 300 g/kg.

5. In conclusion, the use of over 150 g/kg of WLM in broiler diets depressed performance results. However, depression of nutrient utilisation was only observed when 250 or 300 g/kg of WLM was used.

     

Effect of extracted galactoglucomannan oligosaccharides from pine wood (Pinus brutia) on Salmonella typhimurium colonisation,growth performance and intestinal morphology in broiler chicks

1. An in vitro and in vivo study was conducted to evaluate the fermentability of isolated galactoglucomannan oligosaccharides (GGMs) and the influence of their feeding on shedding and colonisation of Salmonella typhimurium, growth performance and intestinal morphology in broiler chicks.

2. The in vitro data demonstrated that three probiotic lactic acid bacteria namely Lactobacillus casei, L. plantarum and Enterococcus faecium were able to ferment the extracted oligosaccharides and other tested sugars on a basal de Man Rogosa Sharpe media free from carbohydrate.

3. For the in vivo experiment, 144 one-d-old male Ross 308 broiler chicks were divided into 6 experimental treatments (with 4 replicates) including two positive and negative controls which received a basal maize-soybean diet without any additives, supplementation of three levels of isolated GGMs (0.1%, 0.2% and 0.3%) and a commercial mannanoligosaccharide (MOS) at 0.2% to the basal diet. All birds except those in the negative control group were challenged orally with 1 × 10⁸ cfu of S. typhimurium at 3-d post-hatch.

4. The results revealed that challenge with S. typhimurium resulted in a significant reduction in body weight gain, feed intake, villus height, villus height to crypt depth ratio and villus surface area in all of infected chicks. Birds that were given GGMs or MOS showed better growth performance, increased villus height and villus surface area and decreased S. typhimurium colonisation than the positive control birds. GGM at 0.2% level was more effective than the other treatments in improving growth rate as well as gut health of broiler chicks.

     

Effects of lipid sources,lysophospholipids and organic acids in maize-based broiler diets on nutrient balance,liver concentration of fat-soluble vitamins,jejunal microbiota and performance

1. Three experiments with a 2 × 2 × 2 factorial arrangement were conducted to evaluate maize-based diets for broilers containing different lipid sources [soybean oil (S) or beef tallow (T)] supplemented with or without lysophospholipids and organic acids on nutrient balance (Experiment I, evaluation period of 10–14 d), on liver concentration of fat-soluble vitamins, on jejunal microbiota (Experiment II, sampling at d 14) and on performance (Experiment III, accumulated periods of 1–14, 1–21 and 1–42 d).

2. A total of 1344 male chicks were used. In each experiment, the birds were allotted in a completely randomised design with 8 replications. The lysophospholipids were mainly composed of lysolecithins and the organic acids blend was constituted by lactic (40%), acetic (7%) and butyric acids (1%).

3. An interaction between lipid sources and lysophospholipids was observed on faecal apparent digestibility of lipid (ADL), which improved with lysophospholipids addition in T diets. Broilers fed on S had higher ADL and faecal apparent digestibility of nitrogen-corrected gross energy (ADGE_N).

4. It was not possible to demonstrate a significant treatment effect on the liver concentration of vitamins A and E, even with the differences in fatty acid profile between S and T.

5. Enterobacteria values were below the detection threshold. Lysophospholipid supplementation reduced gram-positive cocci in T-fed birds. S diets promoted lower total anaerobe counts compared with T diets, independent of additives.

6. S diets increased BW gain and feed:gain ratio in all evaluation periods. Lysophospholipids and organic acids improved feed:gain ratio at 1–21 d in T diets. Furthermore, main effects were observed for lysophospholipids and organic acids at 1–42 d, which increased BW gain and improved feed:gain ratio, respectively.

7. No positive interactions between additives were found.

     

An evaluation of in vitro intestinal absorption of iron,calcium and potassium in chickens receiving gold nanoparticles

1. This study evaluated the effect of oral administration of colloidal gold nanoparticles on accumulation of gold in the small intestine and intestinal absorption of iron, calcium and potassium under in vitro conditions.

2. The gold nanoparticles are non-ionic, nanocrystalline, chemically pure particles 5 nm in size, produced in a physical process.

3. In total, 126 one day-old Ross 308 chicks were assigned to 7 experimental groups of 18 birds each (3 replications of 6 individuals each).

4. The control group (G-C) did not receive gold nanoparticles. Groups: Au-5(7), Au-10(7) and Au-15(7) received gold nanoparticles in their drinking water in the amounts of 5 mg l^?1 for group Au-5(7), 10 mg l^?1 for group Au-10(7) and 15 mg l^?1 for group Au-15(7) in 8–14, 22–28 and 36–42 d of life. The birds in groups Au-5(3), Au-10(3) and Au-15(3) received gold nanoparticles in the same amounts, but only in 8–10, 22–24 and 36–38 d of life.

5. The study revealed that nanogold supplied via ingestion leads to dose- and time-dependent accumulation of gold in the intestinal walls.

6. Nanogold present in the jejunum has a negative impact on the absorption of calcium, iron and potassium under in vitro conditions.

     

The spring-rise phenomenon: Seasonal changes in the worm burdens of breeding ewes and in the availability of pasture infection

Extract

A Mastitis control programme is essentially a biological regulatory system involving the three essential components of any control mechanism:

• A signal from a detector indicating departure from normality

• The interpretation of the signal (diagnosis)

• A feed-back signal to the origin of the detection signal indicating corrective action.

     

Effects of different formulations of α-tocopherol acetate (vitamin E) on growth performance,meat quality and antioxidant capacity in broiler chickens

1. The objective of this study was to investigate and compare the effects of α-tocopherol acetate (vitamin E (VE)) and microencapsulated VE (MVE) on growth performance, meat quality and antioxidant capacity in broiler chickens.

2. A total of 360 d-old broiler chicks were procured and randomly allocated into three groups with 6 replicates. Each replicate had 20 chickens. Chickens were fed with basal diets (CON group) or experimental diets supplemented with 20 mg/kg VE (VE group) or 20 mg/kg MVE (MVE group) for 42 d.

3. The results showed that the MVE group had higher body weight gain (BWG) than the CON and VE groups, and higher gain/feed ratio (G/F ratio) than the CON group during the period of 22–42 d. During the whole experiment, a higher increase in BWG was found in the MVE group than the CON group.

4. Chickens fed on diets supplemented with the VE or MVE had lower abdominal fat percentage, higher pH and antioxidant enzyme activity than the CON group in the breast meat.

5. There was an increased tendency in the hepatic glutathione peroxidase (GSH-Px) enzyme activity of the VE and MVE groups than the CON group. The hepatic mitochondrial total antioxidant capacity and GSH-Px enzyme activity in the MVE group were higher than the CON group. Hepatic 2,2-dipheny-?-picrylhydrazyl scavenging activity of the MVE group was higher than the CON group.

6. These results suggested that the dietary addition of VE or MVE could improve breast meat quality in broilers. MVE supplementation may improve growth performance, hepatic mitochondrial antioxidant capacity and free radical scavenging capacity in chickens. In addition, dietary supplementation of MVE gave better broiler growth performance than VE.

     

Behavioural assessment of pain in commercial turkeys (Meleagris gallopavo) with foot pad dermatitis

1. Two experiments were conducted to investigate the differences in susceptibility to foot pad dermatitis (FPD) of two medium-heavy lines of turkeys, and whether FPD is painful, by detailed analysis of behaviour in birds with and without analgesic treatment (betamethasone).

2. Turkeys housed on dry litter in the first experiment generally had more frequent bouts of different behaviours that were of shorter duration than birds on wet litter. T-patterns (behavioural sequences) were more frequent, varied and complex on dry than on wet litter. Betamethasone-injected birds of line B, but not breed A, had shorter resting and longer standing durations on wet litter than saline-injected birds.

3. In the second experiment, turkeys on wet litter given saline stood less and rested more than all other treatment groups, suggesting that they experienced pain that was alleviated in birds receiving betamethasone. Turkeys on dry litter had more frequent, varied and complex patterns of behaviour than turkeys on wet litter and birds kept on intermediate litter wetness. Betamethasone provision increased pattern variety regardless of litter treatment.

4. Turkeys with low FPD scores transferred to wet litter and given saline injections had a longer total duration of resting and shorter duration of standing compared to betamethasone-treated birds. Low FPD birds transferred to wet litter had a similar number of patterns and total pattern occurrence as high FPD birds transferred to dry litter. Betamethasone increased pattern variety and frequency compared to saline injections whereas overall pattern complexity was similar.

5. It was concluded that wet litter affects the behaviour of turkey poults independently of FPD and that betamethasone may also change the behaviour of turkeys. There was some evidence from analgesic treatment and T-pattern analyses that FPD was painful. However, there was no evidence of differences in susceptibility to FPD of the two commercial hybrids.

     

Influence of an organic acid blend and essential oil blend,individually or in combination,on growth performance,carcass parameters,apparent digestibility,intestinal microflora and intestinal morphology of broilers

1. This study aimed to evaluate the influence of an organic acid (OA) and essential oil (EO) blends, individually or in combination, on growth performance, carcass parameters, apparent digestibility, intestinal microflora and intestinal morphology of broilers.

2. A total of 480 one-d-old male Ross 308 chicks were randomly assigned to 4 treatments consisting of 4 replicates each (n = 30 birds in each replicate). Dietary treatments consisted of a basal diet (control), and basal diet supplemented with 2 g/kg OA blend (OAB), 300 mg/kg EO blend (EOB), or with 2 g/kg OA and 300 mg/kg EO blend (OAB–EOB) for 42 d.

3. The dietary supplementation with EO blend or in combination with OA blend increased body weight gain and improved feed efficiency as compared to control. Dietary treatments had no significant effects on feed consumption or relative organ weights of broilers.

4. The OAB diet increased carcass yield compared to the control diet but the lowest carcass yield occurred with the OAB–EOB combination. Birds fed on EOB and OAB–EOB diets had lower ileum Escherichia coli counts than birds fed on the control diet.

5. There was no significant effect of treatments on apparent digestibility at 16–21 d but the EOB and OAB–EOB diets increased apparent digestibility of dry matter and crude protein during the finisher period (d 37–42) compared to the control diet.

6. Birds fed on the EOB and OAB–EOB diets had greater villus height in the ileum at 21 and 42 d of age and had lower crypt depth in the ileum at 42 d of age than birds given the control diet.

7. In conclusion, beneficial effects of the use of EO blend individually or in combination with the OA blend were observed but the OA blend alone was ineffective. Furthermore, the use of the combination of OA and EO was more effective, in some respects, than their individual use.

     

Estimation of genetic parameters related to eggshell strength using random regression models

1. This study examined the changes in eggshell strength and the genetic parameters related to this trait throughout a hen’s laying life using random regression.

2. The data were collected from a crossbred population between 2011 and 2014, where the eggshell strength was determined repeatedly for 2260 hens.

3. Using random regression models (RRMs), several Legendre polynomials were employed to estimate the fixed, direct genetic and permanent environment effects. The residual effects were treated as independently distributed with heterogeneous variance for each test week.

4. The direct genetic variance was included with second-order Legendre polynomials and the permanent environment with third-order Legendre polynomials.

5. The heritability of eggshell strength ranged from 0.26 to 0.43, the repeatability ranged between 0.47 and 0.69, and the estimated genetic correlations between test weeks was high at > 0.67.

6. The first eigenvalue of the genetic covariance matrix accounted for about 97% of the sum of all the eigenvalues.

7. The flexibility and statistical power of RRM suggest that this model could be an effective method to improve eggshell quality and to reduce losses due to cracked eggs in a breeding plan.

     

Effects of different rearing systems on muscle and meat quality traits of slow- and medium-growing male chickens

1. This experiment was conducted to evaluate the effect of production system on the meat quality of slow- and medium-growing chickens. A total of 1075 1-d-old male chicks were equally divided into 6 experimental groups, represented by three strains (SG: TETRA-H, MG1: TETRA HB Color, MG2: Shaver Farm) and were reared in a poultry house in floor pens (12 males/m²).

2. On d 49, 150 healthy birds (50/genotype) were placed in a free-range family farm while the rest of the birds remained indoors. All birds were fed ad libitum and consumed the same diet. On d 70, 20 birds of each experimental group were slaughtered and muscle samples were taken from the left breast and thigh muscles.

3. Thigh muscle of SG males kept on free range was darker (L* = 75.12 vs. 78.33) with lower frying loss (45.9% vs. 55.9%) compared with the indoor group. Similar results were obtained from the MG1 group. Free-range MG2 males had lighter thigh meat (L* = 50.7 vs. 57.8) and lower frying loss compared to the indoor group.

4. In general, the indoor treatment had a lower impact on breast meat than the outdoor system. Regardless of the rearing system, genotypic differences were more pronounced in thigh than in breast muscle.