An optimal dietary non-phytate phosphorus level of broilers fed a conventional corn–soybean meal diet from 4 to 6 weeks of age

It is imperative to evaluate precise nutrient requirements of animals in order to optimize productivity and minimize feed cost and nutrient excretions. The current non-phytate phosphorus (NPP) recommendation for broilers is based on the papers published 30 years ago. However, today’s commercial birds are quite different from those before 30 years. Therefore, the present experiment was conducted with growing male broiler chickens to evaluate an optimal dietary NPP level of broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age. The 1-day-old chicks were fed corn–soybean meal diet containing 0.39% NPP from 1 to 3 weeks of age. At 22 days of age, 360 birds were selected and randomly allotted by BW to one of 10 dietary treatments with six replicate cages of six birds per cage for each treatment. Birds were fed the P-unsupplemented corn–soybean meal basal diet and the basal diet supplemented with inorganic P as CaHPO₄·H₂O ranging from 0.00% to 0.45% with 0.05% increment from 4 to 6 weeks of age. The dietary NPP levels were 0.09%, 0.14%, 0.20%, 0.24%, 0.30%, 0.34%, 0.38%, 0.45%, 0.49% and 0.54%, respectively, and the dietary Ca level was fixed at 0.90% for all treatments. The results showed that average daily gain, serum inorganic P concentration, tibia bone strength, tibia ash percentage and P percentage, tibia bone mineral content (BMC) and density (BMD), middle toe ash percentage and P percentage, middle toe BMC, total body BMC and BMD were affected (P<0.0001) by dietary NPP level, and increased linearly (P<0.0001) and quadratically (P<0.003) as dietary NPP levels increased. Optimal dietary NPP levels estimated based on fitted broken-line models (P<0.0001) of the above indices are 0.21%, 0.29%, 0.29%, 0.29%, 0.29%, 0.31%, 0.29%, 0.30%, 0.27%, 0.29% and 0.28%, respectively. It is suggested that the total body BMC and BMD, and middle toe ash P and BMC might be new, sensitive and non-invasive criteria to evaluate the dietary NPP requirements of broilers. The optimal dietary NPP level would be 0.31% for broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age.     

Modelling and optimizing of calcium and non-phytate phosphorus requirements of male broiler chickens from 1 to 21 days of age using response surface methodology

The skeleton is the main site of P and Ca deposition; therefore, accurate estimation of Ca and P requirements is necessary to maintaining health and optimum performance of broiler chickens. A response surface methodology (RSM) using a central composite design (CCD) was used for evaluating and optimizing of Ca and non-phytate P (NPP) requirements of broiler chickens for optimal performance, ileal nutrient digestibility and bone mineralization from 1 to 21 days of age. A total of 750 one-day-old male broiler chickens (Ross 308) were randomly distributed into 50 cages including 9 treatments, each replicated 5 times (except central treatment with 10 replicates) and 15 birds in each cage by CCD. The dietary Ca levels of 4.3, 5.6, 8.6, 11.7 and 13.0 g/kg and NPP of 2.5, 2.9, 4.0, 5.0 and 5.4 g/kg were used for nine treatments of CCD. The results indicated that the linear and quadratic effects of NPP, quadratic effects of Ca and Ca × NPP were significant for average weight gain (AWG, P < 0.05), average feed intake (AFI, P < 0.05), feed conversion ratio (FCR, P < 0.05) and Ca and P apparent ileal digestibility (AID, P < 0.05); however, the linear effect of Ca was significant only for FCR (P < 0.05). On the other hand, tibia and toe ash were affected by NPP (linear and quadratic, P < 0.01) and Ca (quadratic, P < 0.01). The second-order polynomial regression model was significant for AWG (R² = 0.93, P < 0.001), AFI (R² = 0.88, P < 0.001), FCR (R² = 0.78, P < 0.001), AID of Ca (R² = 0.78, P < 0.001) and P (R² = 0.88, P < 0.001), tibia ash (R² = 0.86, P < 0.001) and toe ash (R² = 0.85, P < 0.001). The multi-objective optimization indicated that broiler chickens from 1 to 21 days of age need 7.03 and 4.47 g/kg of Ca and NPP, respectively, to achieve optimal AWG, FCR, tibia and toe ash. However, the dietary Ca and NPP levels can be reduced to 6.57 and 3.95 g/kg with a slight negative impact on performance and bone mineralization, respectively. In conclusion, the findings indicate that using multi-objective optimization model such as RSM provides more information regarding optimum Ca and NPP requirements of broiler chickens, considering the complex interaction between these two minerals. While the NPP levels are in line with current recommended requirements, Ca levels are considerably lower and suggest that current recommended Ca requirements may be in excess of the needs of the broiler.     

Weeping forsythia extract alleviates dexamethasone-induced oxidative injury of breast muscles in broilers

Antioxidants have been always used to improve post-slaughter meat quality in broilers subjected to stress. Forsythia suspensa extract (FSE), a traditional Chinese herbal medicine, is generally regarded as a natural source of antioxidants. Therefore, the objective of this study was to test the hypothesis that FSE could protect post-slaughter breast muscles against oxidative injury induced by dexamethasone (DEX) mimicking chronic physiological stress in poultry production. Average daily gain and feed efficiency of poultry were suppressed by DEX and improved by FSE (P < 0.05). Dexamethasone caused the decrease in the redness value and the increase in the lightness and yellowness values and drip loss of the breast muscles (P < 0.05), and FSE had the converse effects (P < 0.05). Dietary FSE supplementation decreased monounsaturated fatty acid (FA) and increased polyunsaturated FA in breast muscles of broilers (P < 0.05). In addition, FSE decreased malondialdehyde and carbonyl content in the breast muscles of DEX-treated broilers (P < 0.05). The inhibition of 1,1-diphenyl-2-picryl-hydrazyl in the breast muscles was decreased by DEX and increased by FSE (P < 0.05). Total-antioxidant capacity and glutathione peroxidase activity in the breast muscles were decreased in birds subjected to DEX and increased in birds supplemented with FSE (P < 0.05). Totally, DEX suppressed growth performance and induced breast muscle oxidative injury in broilers, and FSE supplementation improved antioxidant capacity to attenuate these adverse effects. Therefore, FSE could be a potential natural antioxidant to alleviate oxidative injury of the breast muscles in broilers and to improve the meat quality for human consumption.     

Meta-analysis of phosphorus utilization by growing pigs: effect of dietary phosphorus,calcium and exogenous phytase

Optimizing phosphorus (P) utilization in pigs requires improving our capacity to predict the amount of P absorbed and retained, with the main modulating factors taken into account, as well as precisely determining the P requirements of the animals. Given the large amount of published data on P utilization in pigs, a meta-analysis was performed to quantify the impact of the different dietary P forms, calcium (Ca) and exogenous phytases on the digestive and metabolic utilization criteria for dietary P in growing pigs. Accordingly, the amount of phytate P (PP) leading to digestible P (g/kg) was estimated to be 21%, compared with 73% for non-phytate P (NPP) from plant ingredients and 80% for NPP from mineral and animal ingredients (P < 0.001). The increase in total digestible dietary P following the addition of microbial phytase (PhytM) from Aspergillus niger (P < 0.001) was curvilinear and about two times higher than the increase following the addition of plant phytase, which leads to a linear response (P < 0.001). The response of digestible P to PhytM also depends on the amount of substrate, PP (PhytM² × PP, P < 0.001). The digestibility of dietary P decreased with dietary Ca concentration (P < 0.01) independently of phytase but increased with body weight (BW, P < 0.05). Although total digestible dietary P increased linearly with total NPP concentration (P < 0.001), retained P (g/kg), average daily gain (ADG, g/day) and average daily feed intake (ADFI, g/day) increased curvilinearly (P < 0.001). Interestingly, whereas dietary Ca negatively affected P digestibility, the effect of dietary Ca on retained P, ADG and ADFI depended on total dietary NPP (NPP × Ca, P < 0.01, P < 0.05 and P < 0.01, respectively). Increasing dietary Ca reduced retained P, ADG and ADFI at low NPP levels, but at higher NPP concentrations it had no effect on ADG and ADFI despite a positive effect on retained P. Although the curvilinear effect of PhytM on digestible P increased with PP (P < 0.001), this effect was lessened by total NPP for ADG and ADFI (PhytM × NPP and PhytM² × NPP, P < 0.05) and depended on both total NPP and Ca for retained P (PhytM² × NPP × Ca, P < 0.01). This meta-analysis improves our understanding of P utilization, with major modulating factors taken into account. The information generated will be useful for the development of robust models to formulate environmentally friendly diets for growing pigs.     

Effect of raw and fermented grape seed on growth performance,antioxidant capacity,and cecal microflora in broiler chickens

Grape seed (GS) is a by-product of the fruit juice and wine industry with the potential to be an alternative to synthetic antioxidants due to its antioxidant activity. Agro-industrial residues can be converted to more effective products by solid-state fermentation. The objective of the study was to investigate the effects of GS and fermented grape seed (FGS) on the growth performance, antioxidant capacity, and cecal microflora in broiler chickens. A total of 128 female broilers were randomly allocated into four treatment groups, each consisting of four replicates of eight birds. Throughout the 42-day feeding period, the birds were fed with soybean-corn based diet (CON), 0.15 g/kg synthetic antioxidant (butylated hydroxyanisole) supplemented diet (AO), 5 g/kg GS supplemented diet (GS), and 5 g/kg FGS supplemented diet (FGS). Dietary GS, FGS, and AO supplementation increased the BW (P < 0.05) and average daily weight gain (ADG, P < 0.05) compared with the CON group in the overall period of 42 days. Dietary FGS also increased the ADG (P < 0.05) in the period of 22–42 days compared with the control group. The pH of the breast meat of the chickens fed GS was higher (P < 0.01) than CON and FGS groups. Dietary FGS and AO decreased the b* value (P < 0.01) of breast meat compared with the CON group. Grape seed had the highest serum glutathione peroxidase (P < 0.05) and catalase (CAT, P < 0.01) levels among the treatment groups. The FGS also increased serum CAT level (P < 0.01) compared with the AO group. Moreover, dietary FGS supplementation increased Lactobacillus spp. (P < 0.05) in the cecum compared with the other treatment groups and decreased Staphylococcus aureus (P < 0.05) compared with the CON and AO groups. The present findings indicate that GS and FGS can be used in broiler diets as alternatives to synthetic antioxidants.     

Effects of feed form and energy levels on growth performance,carcass yield and nutrient digestibility in broilers

Feed form is well recognized to improve broiler performance, specially by increasing feed intake (FI). However, when different diet energy levels are used, the results differ in the literature. Therefore, this experiment was conducted to evaluate the influence of feed form and dietary metabolizable energy (ME) levels on broiler performance, carcass yield and on the digestibility of DM, CP, starch and gross energy. In total, 1152 male Cobb 500 broilers were evaluated between 35 and 47 days. The birds were distributed according to a completely randomized design in a 2 × 4 factorial arrangement, consisting of two feed forms (mash or pellet) and four ME levels (12.73, 13.06, 13.40 or 13.73 MJ/kg), totaling eight treatments with eight replicates of 18 birds. Broilers fed the lowest ME level presented the lowest weight gain (WG) and worst feed per unit gain (P < 0.01). Metabolizable energy intake increased (P < 0.01) with progressive increments of ME, which, however, did not affect caloric conversion (CC, P > 0.05). Pelleted diets promoted higher FI, WG, ME intake (P < 0.01) and better feed per unit gain and CC (P < 0.05) compared with mash. In mash diets, increasing dietary ME levels promoted a linear increase in WG (P < 0.01) and reduced feed per unit gain (P ≤ 0.05), but did not affect FI (P > 0.05). In pelleted diets, on the other hand, increasing ME levels linearly reduced FI (P < 0.05) and feed per unit gain (P < 0.01). Broilers fed pelleted diets presented higher abdominal fat deposition than those fed mash (P < 0.05). Increasing ME levels reduced the coefficients of ileal apparent digestibility of DM (P < 0.01) and total starch (P < 0.05) but did not affect the digestibility of other evaluated nutrients. The digestibility of all nutrients was lower when pelleted diets were fed compared with mash. Increasing inert material inclusion in the diets at the expense of soybean oil to reduce dietary ME levels promoted higher pellet durability index values (P < 0.05) and the percentage of fines (P < 0.01). Overall, the results suggest that pelleted diets promote better broiler performance because they increase FI, since the digestibility of dietary fractions is reduced. Chickens consuming low-energy pelleted diets may increase FI to compensate for energy deficit. In contrast, broilers fed mash diets may have reached their maximum intake capacity and did not regulate FI by changing feed energy density. When feeding pelleted diets, dietary energy reduction should be considered to reduce feed costs and to improve the carcass quality of broilers.     

Effects of 5-aminolevulinic acid on the inflammatory responses and antioxidative capacity in broiler chickens challenged with lipopolysaccharide

5-Aminolevulinic acid (5-ALA) is an intermediate in haem biosynthesis and has anti-apoptotic, anti-inflammatory, antioxidant, and other pharmacological effects. This study aimed to investigate the effect of dietary supplementation with 5-ALA on growth performance, antioxidant capacity, and inflammatory response of the lipopolysaccharide (LPS)-challenged broiler chickens. The experiment was designed as a 2 × 2 factorial arrangement with dietary 5-ALA (0 or 60 mg/kg) and LPS (injection of saline or 0.5 mg/kg BW) levels as treatments. A total of 240 one-day-old Arbor Acres broilers were distributed into four treatments consisting of six replicates of 10 birds. All the experimental broilers were intraperitoneally injected with LPS or sterile saline at 16, 18, and 20 days of age. Our results showed that dietary 5-ALA supplementation reduced (P < 0.05) the feed to gain before broilers were stimulated with LPS (days 1–15). LPS challenge decreased (P < 0.05) the catalase (CAT), total superoxide dismutase activities and increased the content of malondialdehyde (MDA) in the serum of broiler chickens. However, 5-ALA supplementation had a tendency to increase (P = 0.08) the activity of CAT and decreased (P < 0.05) the content of MDA. LPS challenge showed higher (P < 0.05) interleukin (IL)-1β, IL-6, and IL-10 concentrations in the serum, whereas dietary 5-ALA supplementation decreased (P < 0.05) the levels of IL-1β and IL-6. Additionally, dietary 5-ALA supplementation significantly attenuated (P < 0.05) the upregulation of mRNA expression levels of hepatic toll-like receptor 4 (TLR4), IL-1β, and IL-2 induced by LPS challenge. Moreover, dietary 5-ALA supplementation also enhanced the mRNA expression of 5-aminolevulinate dehydratase, ferrochelatase, and haem oxygenase-1 (HO-1) as compared to the unsupplemented groups. In conclusion, our results suggested that supplementation of 60 mg/kg 5-ALA exhibited LPS-induced anti-inflammatory and antioxidant properties by enhancing the HO-1 expression and inhibiting the TLR4/NF-κB signalling pathway.     

Effects of dietary selenium and vitamin E on immune response and biological blood parameters of broilers reared under thermoneutral or heat stress conditions

A study was conducted using 360 broiler chickens to evaluate the effects of dietary vitamin E (0, 125 and 250 mg/kg), selenium (Se, 0, 0.5 and 1 mg/kg), or their different combinations on immune response and blood biological parameters of broilers raised under either thermoneutral (TN, 23.9 °C constant) or heat stress (HS, 23.9 to 37 °C cycling) conditions. Humoral immunity was assessed by intravenous injection of 7 % sheep red blood cell (SRBC) followed by evaluation of serum for antibody titers in primary and secondary responses. Heterophil to lymphocyte (H/L) ratio also determined as an indicator of stress. Furthermore, at the end of the experiment, birds were bled for determination of some biological parameters. There was a significant reduction in body weight and feed intake, but the feed conversion ratio increased when the birds were exposed to HS (P?<?0.05). Body weight and feed intake were not influenced significantly by dietary vitamin E and Se (P?>?0.05), whereas feed conversion was improved significantly by 125 mg/kg vitamin E (P?<?0.05). The liver and lymphoid organ weights as well as IgM and IgG, antibody titers for primary and secondary antibody responses to SRBC were reduced significantly under HS (P?<?0.05). Heat stress also resulted in a significant increase in H/L ratio (P?<?0.05). Dietary vitamin E resulted in improvement of primary and secondary antibody responses both in TN and HS broilers (P?<?0.05). The HS birds also showed an improved antibody titer in secondary response with high concentration of Se (P?<?0.05). Vitamin E and Se had interactive effects on anti-SRBC titers; however, no consistent differences were found between dietary levels during the study. The H/L ratio decreased by feeding vitamin E at both levels either under HS or TN conditions (P?<?0.05). The serum concentrations of glucose, triglycerides, total cholesterol, and LDL-cholesterol were increased but serum HDL-cholesterol decreased in HS broilers (P?<?0.05).     

Effects of free and dipeptide forms of methionine supplementation on oxidative metabolism of broilers under high temperature

Our previous studies have shown that methionine supplementation could help to attenuate the effects of heat stress on the metabolism of broiler chickens. Here we investigated for the first time the effects of methionine supplementation in the form of DL-methionyl-DL-methionine on broilers subjected to heat stress during the growth phase. Broilers were divided into two groups; one group was reared under thermoneutral conditions and the other under continuous heat stress (30 ± 1 °C, 60% relative humidity). Both groups were subdivided into three dietary treatments: a methionine-deficient (MD) diet, a diet supplemented with free methionine (DL-M), and a diet supplemented with methionine dipeptide (DL-MM). Broilers raised under chronic heat stress had lower feed intake and weight gain than broilers raised under thermoneutral conditions (P < 0.05). There were no differences in animal performance between methionine-supplemented diets (DL-M and DL-MM). Heat-stressed birds had significantly higher heterophil/lymphocyte (H/L) ratio than thermoneutral birds. Under heat stress, broilers fed DL-M and DL-MM diets had lower H/L ratio than birds fed the MD diet. Higher concentrations of carbonylated proteins and lower concentration of reduced glutathione were observed in broilers raised under heat stress. In comparing heat-stressed broilers, we found that birds fed the DL-M diet had lower concentrations of thiobarbituric acid-reactive substances and carbonylated proteins than those fed the MD diet (P < 0.05). Higher expression of glutathione peroxidase (GPX) and glutathione synthetase (GSS) genes was observed in heat-stressed broilers (P < 0.05). Under heat stress, the MD diet increased GPX expression compared with other diets. Under thermoneutral conditions, the DL-M diet resulted in the highest GSS expression. There was a negative correlation between DNA methylation and GPX and GSS expression. Our results showed that supplementation of broiler diets with free methionine or methionine dipeptide may help attenuate the effects of heat stress through enhanced activation of genes related to the glutathione antioxidant system. Methionine effects were found for gene regulation, gene expression, and post-translational processing.     

Use of available crop by-products as alternative bedding materials to wheat straw for rearing broilers

The provision of suitable bedding for rearing broilers is an ongoing challenge for poultry producers. The aim of the present study was to evaluate the effect of using different types of crop residues as alternative bedding materials to wheat straw on growth performance, carcass traits, health, and welfare of broilers; moreover, the effects on the bedding and air quality were analyzed. We randomly assigned 180 1-day-old chickens (Cobb 500) across six bedding groups (three replicates of 10 birds each). Chickens in all groups were reared under similar housing conditions. Chickens of one group were reared on a wheat straw bedding (control), whereas those of the remaining five groups were reared on clover straw, cornstalk chips (CS), sugarcane top chips, chopped palm spines (CPS), and corn ear husks. Cornstalk chip and chopped palm spines were associated with the lowest (P < 0.05) ammonia concentrations compared with the remaining beddings. The mean values of bedding moisture percentage (P < 0.05), caking score, and ammonia concentrations (P < 0.05) were decreased with 6-week-old broilers reared on cornstalk chips. At 6 weeks, wheat straw, clover straw, sugarcane top chips and corn ear husks resulted in higher (P < 0.0001) BW and average daily gain compared with CS and CPS. Broilers reared on clover straw bedding showed the best FCR during 4–6 weeks of age (P < 0.01), and those kept on clover straw and sugarcane top chips exhibited the best (P < 0.01) feed conversion ratio (1.61 and 1.64, respectively) during 0–6 weeks of age. The carcass dressing yield, airborne dust concentration, bedding pH, and bacterial counts did not differ among the different bedding materials. The proportions of the drumsticks, gizzards, and abdominal fat of 6-week-old broilers were affected by bedding type (P < 0.05); but the differences among the bedding treatments were small. The mean incidence of footpad dermatitis and breast blisters was significantly less using clover straw. Broilers reared on chopped palm spine had the highest (P < 0.05) heterophil/lymphocyte ratio when compared with their counterparts. Conclusively, using clover straw or cornstalks as an alternative bedding material may be a beneficial strategy and should be highly recommended for rearing broilers.     

Effects of gingerols-rich extract of ginger on growth performance,serum metabolites,meat quality and antioxidant activity of heat-stressed broilers

In order to investigate the effects of dietary ginger extract (GE) enriched in gingerols on broilers under heat stress (HS) from 21 to 42 days of age, a total of 144 Ross 308 male broilers were randomly allocated to three groups with six replicates of eight broilers per replicate. Broilers in the control group were raised at 22 °C and fed a basal diet, and broilers in the other two groups were raised under cyclic HS (34 °C from 9:00 to 17:00 and at 22 °C for the rest of the time) and fed the basal diet with or without 1000 mg/kg GE. Supplementation of GE improved (P < 0.05) final body weight, average daily gain and feed conversion ratio of broilers under HS, and tended (P < 0.1) to increase breast muscle yield. The alterations of serum total protein, albumin, total cholesterol levels and aspartate aminotransferase activity under HS were reversed (P < 0.05) by GE, which also decreased (P < 0.05) serum triglyceride level and alanine aminotransferase activity. The decreased redness (a* value) and increased drip loss of breast muscle induced by HS were restored (P < 0.05) by GE. Moreover, GE supplementation increased (P < 0.05) total antioxidant capacity and decreased (P < 0.05) malondialdehyde content in liver and breast muscle, and increased (P < 0.05) glutathione peroxidase activity in serum and breast muscle. In conclusion, dietary GE supplementation restored growth performance, serum metabolites and meat quality of broilers under HS possibly by improving antioxidant activity.     

Effects of dietary calcium and phosphorus deficiency and subsequent recovery on broiler chicken growth performance and bone characteristics

The ability of birds to modify dietary phosphorus utilisation when fed with low-phosphorus and calcium (Ca) diets was studied using different sequences of dietary phosphorus and Ca restriction (depletion) and recovery (repletion) during the grower and the finisher phases. A total of 3600 Ross 708 broilers were randomly divided into 10 replicate pens per treatment (60 per pen, six pens per block). Chicks were fed a common starter diet from days 0 to 10, then a grower control diet (C: 0.90% Ca, 0.39% non-phytate phosphorus, nPP), mid-level diet (M: 0.71% Ca, 0.35% nPP) or low Ca and nPP diet (L: 0.60% Ca, 0.30% nPP) from days 11 to 21, followed by a finisher diet C, M or L containing, respectively, 0.85%, 0.57% or 0.48% Ca and 0.35%, 0.29% or 0.24% nPP from days 22 to 37. Six treatment sequences were tested: CC, MM, LL, ML, LC and LM. Bone mineral content by dual-energy X-ray, tibia ash, toe ash weight and tibia breaking strength were measured on days 21 and 37. No significant effect was observed on growth performance throughout the experiment. Diet L reduced bone mineral content, breaking strength, tibia and toe ash by 9%, 13%, 11% and 10%, respectively, on day 21 (compared with diet C, for linear effect, P<0.05). On day 37, bone mineral content, breaking strength, tibia and toe ash remained lower compared with control values (CC v. MM v. LL, P<0.05 for linear and quadratic effects). Mineral depletion duration (ML v. LL) did not affect bone mineral status. Replenishing with the C diet during the finisher phase (LC) restored bone mineral content, tibia ash and toe ash weight better than the M diet did, but not to control levels (CC v. LC v. LM, for linear effect, P<0.05). These results confirm that dietary Ca and nPP may be reduced in the grower phase without affecting final growth performance or breaking strength as long as the finisher diet contains sufficient Ca and nPP. The practical applications of this strategy require further study in order to optimise the depletion and repletion steps.     

The effect of stocking rate and supplementary selenium on the fatty acid composition and subsequent peroxidisability of poultry muscle tissues

Selenium (Se) plays a crucial role in protecting biological materials from oxidative damage through the action of the selenoprotein glutathione peroxidase (GSH-Px), and the effectiveness of this protection is often dependent upon Se supply. Recent evidence has indicated that GSH-Px mRNA expression can be upregulated in response to potential oxidative damage risk, and that this upregulation is independent of Se supply. The current study aimed to determine the effect of Se supplementation, stocking rate and tissue fatty acid profile on GSH-Px activity in breast and thigh tissue of commercial broilers. A total of 168 Ross 308 broiler chicks were enrolled onto the study. Prior to enrolment, birds were brooded as a single group and received a starter diet containing no additional Se. The study was a 2 × 2 factorial design comprising of two levels of dietary Se (high Se, 0.5 mg/kg total Se, low Se background Se only), and two stocking rates (high, 30 kg/m², and low, 15 kg/m²). At 15 days of age, birds were blocked by live weight and randomly allocated to one of the four treatments, with six pen replicates per treatment. At 42 days of age, one bird was randomly selected from each pen replicate, euthanased and breast and thigh tissue harvested. GSH-Px activity, thiobarbituric acid reactive substances (TBARS), and fatty acid (FA) content of these tissues were determined. There was no effect (P > 0.05) of stocking rate on GSH-Px activity or TBARS. GSH-Px activity did not differ between tissue types but was greater in high Se birds (P < 0.001) compared to low Se. TBARS concentrations were greater in thigh tissue (P < 0.001), and these thigh concentrations were greater in high Se birds (P < 0.05). There were marked differences between breast and thigh tissue in most FAs (P < 0.001), with breast generally containing greater proportions of polyunsaturated FA, so that breast tissue had a higher (P < 0.001) peroxidisability index (PI) than thigh. A positive correlation between GSH-Px activity and PI in the thigh tissue of high Se birds (Pearson Correlation 0.668; P = 0.025) may indicate that increasing susceptibility to peroxidisation in lipid-rich tissues may also upregulate GSH-Px activity in Se-replete birds. This study suggests that ensuring adequate dietary selenium could be a useful tool to mitigate adverse effects on meat quality caused by oxidation, particularly in lipid-rich meat.     

Dietary essential oils improve feed efficiency and hepatic antioxidant content of broiler chickens

The aim of this study was to test the hypothesis of an improved growth, dietary nutrient availability and overall health of broiler chickens reared on recycled litter when fed a standardised combination of essential oils (EO; carvacrol, cinnamaldehyde and capsicum oleoresin). To assess the effect of dietary treatments, feed intake, weight gain, feed efficiency, availability of dietary nutrients and energy, villus morphometry, excreta sialic acid concentration, hepatic antioxidants and serum amyloid A (SAA) when fed to broiler chickens were evaluated. Counts of Eimeria spp. oocysts were also determined in excreta samples. Four experimental diets were offered, including two basal control diets based on either wheat or maize that contained 215 g CP/kg and 12.13 MJ/kg metabolisable energy and another two diets using the basal control diets supplemented with the EO combination at 100 mg/kg diet. Each diet was fed to eight floor pens, containing two birds each, following randomisation. Birds fed the EO-supplemented diets had an improved (P<0.05) feed conversion ratio (FCR). Birds fed maize-based diet had an improved daily weight gain and FCR (P<0.05) compared with wheat-fed birds. Wheat-based diet tended (P=0.056) to have greater N-corrected apparent metabolisable energy and had greater fat retention coefficient (P<0.05) compared with maize-based diets. No differences (P>0.05) were observed in villus morphometry, sialic acid secretion, number of oocysts and SAA. Feeding the EO improved (P<0.05) the retention of dietary Ca and Na. Compared with maize, feeding wheat-based diets improved the retention coefficients for Ca, P and Na (P<0.05). Feeding dietary EO improved (P<0.05) the concentrations of the hepatic antioxidants, including carotene, coenzyme Q₁₀ and total vitamin E. The hepatic concentration of carotene of the maize-fed birds was 55.6% greater (P<0.05) compared with the wheat-fed birds. These results demonstrated that the addition of a standardised combination of EO in wheat- and maize-based diets provided benefits in terms of feed efficiency, mineral retention and antioxidant status of the birds when reared on recycled litter.     

Investigating the heat tolerance and production performance in local chicken breed having normal and dwarf size

Heat stress significantly impairs the growth performance of broilers, which causes serious losses to the poultry industry every year. Thus, understanding the performance of indigenous chicken breeds under such environment is crucial to address heat stress problem. The purpose of this study was to investigate the effects of heat stress (HS) on production performance, tissue histology, heat shock response (HSP70, HSP90), and muscle growth-related genes (GHR, IGF-1, and IGF-1R) of Normal yellow chicken (NYC) and Dwarf yellow chicken (DYC). Seventy-two female birds from each strain were raised under normal environmental conditions up to 84 days, with birds from each strain being divided into two groups (HS and control). In the HS group, birds were subjected to high temperature at 35 ± 1 °C for 8 h daily and lasted for a week, while in the control group, birds were raised at 28 ± 1 °C. At 91 days old, bird's liver, hypothalamus, and breast muscle tissues were collected to evaluate the gene expression, histological changes, and the production performance. The Feed intake, weight gain ratio, total protein intake and protein efficiency ratio showed a significant reduction in the treatments (P < 0.01) and treatment × strain interaction (P < 0.05) with breast muscle rate significantly reducing among the treatments (P < 0.01) after 7 days of HS. Correspondingly, total abdominal fat showed significant change among treatment and strain (P < 0.01, P < 0.05), respectively. Besides, HS markedly upregulated the mRNA expression of HSP70 and HSP90 in the pectoralis major of both chicken strains, but no significant increase (P < 0.05) was found in mRNA expression of HSP90 in liver and hypothalamus tissues of both chicken strains. Moreover, HS significantly upregulated (P < 0.05) the expression of lipogenic genes (FASN, ACC) in liver tissues of NYC, while mRNA expression of these genes showed no variation in DYC. Similarly, HS downregulated the mRNA expression of muscle growth-related genes (GHR, IGF-1, and IGF-1R). Consequently, the histopathological analysis showed that histological changes were accompanied by inflammatory cell infiltration in liver tissues of both chicken strains; however, histopathological changes were more severe in NYC than dwarf chicken strain. Conclusively, this study depicted that the production performance and growth rate varied significantly between treatment and control group of NYC. However, heat treatment in DYC has not shown significant damaging consequences as compared to the control group that signifies the vital role of the dwarf trait in thermal tolerance.     

Effects of dietary chromium propionate on laying performance,egg quality,serum biochemical parameters and antioxidant status of laying ducks under heat stress

Recent studies have shown that chromium (Cr) could alleviate the negative effects of heat stress on livestock and poultry, but there is little information available to laying ducks. This study aimed to investigate the effects of dietary addition of chromium propionate on laying performance, egg quality, serum biochemical parameters and antioxidant status of laying ducks under hot (average 32 °C) and humid (average 75% relative humidity) summer conditions. A total of 900 66-week-old weight- and laying-matched Shanma laying ducks were randomly divided into five treatments, each with 6 replicates of 30 individually caged birds. The birds were fed either a basal diet or the basal diet supplemented with either 200, 400, 600, or 800 μg/kg Cr as chromium propionate. All laying ducks were given feed and water ad libitum for 5 weeks. The results showed that dietary supplementation with chromium propionate significantly increased the laying rate and yolk colour score (P < 0.05). Treatment with 400 μg/kg Cr as chromium propionate significantly decreased the feed/egg ratio by 5.4% (P < 0.05). Increased supplemental Cr from 0 to 800 μg/kg resulted in an increase in albumen height and the Haugh unit linearly (P < 0.05). Increased supplemental Cr decreased serum cortisol (P < 0.001, linear; P = 0.008, quadratic), heat shock protein-70 (P < 0.001, linear; P = 0.007, quadratic) and glucose (P = 0.007, linear), whereas it increased serum insulin (P = 0.011, Linear), total protein (P = 0.006, linear; P = 0.048, quadratic) and albumin (P = 0.035, linear; P = 0.088, quadratic). Dietary Cr levels increased the activities of superoxide dismutase and glutathione peroxidase, the total antioxidant capacity linearly and quadratically (P < 0.05). A linear and quadratic (P < 0.05) decrease of the malondialdehyde concentrations in response to dietary Cr level was observed. These results indicated that dietary supplementation of Cr as chromium propionate, particularly at 800 μg/kg could beneficially affect the laying rate, egg quality and antioxidant function, as well as modulate the blood biochemical parameters of laying ducks under heat stress conditions.     

Lack of Effect of Dietary Chromium Supplementation on Growth Performance and Serum Insulin, Glucose, and Lipoprotein Levels in Broilers Reared Under Heat Stress Condition

This study evaluated the effects of supplemental dietary chromium (Cr) on the performance, carcass traits, and some serum parameters of broilers under a heat stress (23.9 to 37 °C cycling) condition. A total of 150 1-day-old broiler chicks (Cobb 500) according to a completely randomized design were assigned into five treatment groups. Each treatment consisted of three replicates and each replicate contained ten chicks. Treatments were supplemented with 0 (control), 600, and 1,200 μg kg^?1 Cr in the form of Cr chloride (CrCl₃) and Cr L-methionine from 1 to 49 days of age. Blood samples were collected from two birds in each replicate to determine serum parameters at 35 and 49 days of age. The body mass, feed intake, and conversion ratio were not influenced by dietary Cr (P?>?0.05). Dietary supplementation of Cr from either CrCl₃ or Cr L-methionine caused increased serum concentrations of Cr (P?<?0.05), but had no effect on serum insulin and glucose concentrations at both sampling times (P?>?0.05). Serum triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were also not significantly affected (P?>?0.05) by dietary treatments, whereas total cholesterol concentration decreased in chicks fed Cr L-methionine compared to the control (P?<?0.05).