Influence of antimicrobial feed additives on broiler commensal posthatch gut microbiota development and performance

The effects of avilamycin, zinc bacitracin, and flavophospholipol on broiler gut microbial community colonization and bird performance in the first 17 days posthatch were investigated. Significant differences in gut microbiota associated with gut section, dietary treatment, and age were identified by terminal restriction fragment length polymorphism (T-RFLP), although no performance-related differences between dietary treatments were detected. Similar age-related shifts in the gut microbiota were identified regardless of diet but varied between the ilea and ceca. Interbird variabilities in ileal bacterial communities were reduced (3 to 7 days posthatch) in chicks fed with feed containing antimicrobial agents. Avilamycin and flavophospholipol had the most consistent effect on gut microbial communities. Operational taxonomic units (OTU) linked to changes in gut microbiota in birds on antimicrobial-supplemented diets were characterized and identified. Some OTUs could be identified to the species level; however, the majority could be only tentatively classified to the genus, family, order, or domain level. OTUs 140 to 146 (Lachnospiraceae), OTU 186/188 (Lactobacillus johnsonii), OTU 220 (Lachnospiraceae), OTUs 284 to 288 (unclassified bacterial spp. or Ruminococcaceae), OTU 296/298 (unclassified bacterium or Clostridiales), and OTU 480/482 (Oxalobacteraceae) were less prevalent in the guts of chicks fed antimicrobial-supplemented diets. OTU 178/180 (Lactobacillus crispatus), OTU 152 (Lactobacillus reuteri or unclassified Clostridiales), OTU 198/200 (Subdoligranulum spp.), and OTU 490/492 (unclassified bacterium or Enterobacteriaceae) were less prevalent in the gut of chicks raised on the antimicrobial-free diet. The identification of key bacterial species influenced by antimicrobial-supplemented feed immediately posthatch may assist in the formulation of diets that facilitate beneficial gut microbial colonization and, hence, the development of alternatives to current antimicrobial agents in feed for sustainable poultry production.     

Effects of Clostridium butyricum and Enterococcus faecium on growth performance, lipid metabolism, and cecal microbiota of broiler chickens

To investigate the effects of Clostridium butyricum and Enterococcus faecium on the growth performance, lipid metabolism, and cecal microbiota of broilers, 264 one-day-old male Ross 308 broiler chicks were randomly allocated into four treatments with six replicates in a 2?×?2 factorial arrangement and fed four diets with two levels of C. butyricum (0 or 1?×?10⁹ cfu/kg) and two levels of E. faecium (0 or 2?×?10⁹ cfu/kg) for 42 days. There was no significant interaction between C. butyricum and E. faecium on the growth performance, lipid metabolism, and cecal microbiota of broilers. However, broilers supplemented with E. faecium had lower (P?=?0.022) serum leptin level at day 21 and higher (P?<?0.001) fatty acid synthase (FAS), malic enzyme (ME), and acetyl–CoA carboxylase (ACC) mRNA levels in the liver at day 42. Supplementation of C. butyricum improved (P?<?0.05) the average daily feed intake and average daily gain, increased (P?=?0.016) the serum insulin level at 21 days of age, enhanced (P?<?0.05) the content of intramuscular fat, activities of FAS in the liver and lipoprotein lipase (LPL) in the breast muscle, mRNA expression of FAS, ME, and ACC in the liver and LPL in the breast muscle at 42 days of age, but reduced (P?=?0.030) cecal Bacteroidetes relative abundance at 21 days of age. The results of this study indicate that the increased intramuscular fat content of broilers fed C. butyricum as observed may be the result of enhanced lipogenesis.     

Influence of early qualitative feed restriction and environmental temperature on long bone development of broiler chickens

This investigation was carried out to study the influence of early qualitative feed restriction and environmental rearing temperature on long bone development in broiler. Energy and protein restriction reduced femur width and humerus weight, but did not affect tibia parameters. Broilers kept at cold environmental temperature showed reduced femur, tibia and humerus length and tibia weight, but the calculated density was not affected by rearing temperature. These findings suggest that qualitative feed restriction and environmental temperature influenced the normal long bone growth; however, bone weight/bone length index (calculated density) was not affected by rearing temperature.     

Effects of Enterococcus faecium and dried whey on broiler performance,gut histomorphology and intestinal microbiota

Abstract

The experiment was conducted to study the effects of supplementing a broiler starter diet with the probiotic Enterococcus faecium NCIMB 10415 and dried whey (80% lactose) on chick performance, gut histomorphology and intestinal microbiota. One-day-old male Ross 308 strain broiler chickens were fed diets containing: (i) control feed, (ii) control + 3.5% dried whey, (iii) control + 0.2%E. faecium, and (iv) control + 3.5% dried whey + 0.2%E. faecium. Birds were maintained in battery brooders confined in an environmentally controlled experimental room. The experiment lasted for 21 days. Birds fed E. faecium or E. faecium + dried whey exhibited significantly improved weight gain and feed conversion rate (FCR). Weight gain and FCR of treatment groups 1 – 4 were 628.7, 657.8, 690.9, 689.3 and 1.218, 1.193, 1.107, 1.116, respectively. Lactic acid bacteria counts in both the ileal content and excreta were significantly affected by dietary treatment. Supplementation of the E. faecium and dried whey separately and in combination increased lactic acid bacteria colonization in the ileal content from 4.2 to 5.0, 7.8 and to 5.1 log cfu/g, respectively (treatments 1 – 4). Similarly, supplementation of dried whey and E. faecium separately and in combination increased lactic acid bacteria in the excreta from 5.3 to 5.5, 8.0 and to 7.2 log cfu/g, respectively. Addition of the probiotic E. faecium increased villus height in the ileum (p < 0.05). Thus, supplementation of E. faecium enhanced broiler chick performance with respect to weight gain and FCR. No additive effect of E. faecium and dried whey was detected. Further studies are needed to investigate the relationship between E. faecium and dried whey with respect to gut histomorphology.     

Understanding the mechanisms of zinc bacitracin and avilamycin on animal production: linking gut microbiota and growth performance in chickens

Unravelling the mechanisms of how antibiotics influence growth performance through changes in gut microbiota can lead to the identification of highly productive microbiota in animal production. Here we investigated the effect of zinc bacitracin and avilamycin on growth performance and caecal microbiota in chickens and analysed associations between individual bacteria and growth performance. Two trials were undertaken; each used 96 individually caged 15-day-old Cobb broilers. Trial 1 had a control group (n = 48) and a zinc bacitracin (50 ppm) treatment group (n = 48). Trial 2 had a control group (n = 48) and an avilamycin (15 ppm) treatment group (n = 48). Chicken growth performance was evaluated over a 10-day period, and caecal microbiota was characterised by sequencing of bacterial 16S rRNA gene amplicons. Avilamycin produced no effect on growth performance and exhibited little significant disturbance of the microbiota structure. However, zinc bacitracin reduced the feed conversion ratio (FCR) in treated birds, changed the composition and increased the diversity of their caecal microbiota by reducing dominant species. Avilamycin only produced minor reductions in the abundance of two microbial taxa, whereas zinc bacitracin produced relatively large shifts in a number of taxa, primarily Lactobacillus species. Also, a number of phylotypes closely related to lactobacilli species were positively or negatively correlated with FCR values, suggesting contrasting effects of Lactobacillus spp. on chicken growth performance. By harnessing such bacteria, it may be possible to develop high-productivity strategies in poultry that rely on the use of probiotics and less on in-feed antibiotics.     

Comparative effects of n-hexane and methanol extracts of elecampane (Inula helenium L.) rhizome on growth performance,carcass traits,feed digestibility,intestinal antioxidant status and ileal microbiota in broiler chickens

In this study, the effects of dietary methanol and n-hexane extracts of elecampane rhizome (MEER and HEER, respectively) on growth performance, apparent ileal nutrient digestibility (AID), ileal microbiota, intestinal morphology and antioxidant status of the intestinal mucosa were compared in broiler chickens. In total, 450 1-d-old male chicks were allotted into five groups in six replicates of 15 chicks each. Dietary treatments included: a control, control plus 500 or 1000 mg MEER per kg diet (MEER₅₀₀ and MEER₁₀₀₀) and control plus 500 or 1000 mg HEER per kg diet (HEER₅₀₀ and HEER₁₀₀₀). Broiler performance was not affected by dietary treatments during the starter and grower periods. However, in the finisher (25–42 d) and entire (1–42 d) periods, an increase in body weight gain and a corresponding decrease in feed conversion ratio was noticed when birds received Diets MEER₁₀₀₀ or HEER₁₀₀₀. Also, considering the entire trial, the growth-promoting action of MEER was found to be greater than HEER. When compared with the control, AID of dry matter, organic matter, ether extract (EE) and gross energy (GE) were increased by all treatments, while the AID of EE and GE were also improved by increased extract level. Additionally, HEER groups had significantly increased AID of crude protein. The counts of Escherichia coli and Clostridium spp. were suppressed while the number of Lactobacillus spp. increased in response to an elevated extract level. Meanwhile, the ileum of MEER groups contained lower numbers of Clostridium spp. and greater numbers of Lactobacillus spp. when compared with HEER groups. The duodenal and jejunal structures were not associated with dietary treatments. However, a decreased ileal crypt depth and an increased villus to crypt ratio were observed with addition of extracts, which was more intense with MEER. A lower malondialdehyde content and a higher activity of superoxide dismutase, catalase and glutathione peroxidase were detected in duodenal and jejunal mucosa with increased extract level, and in jejunum, the antioxidant capability of MEER was found to be stronger than HEER. The antioxidant properties of the ileal mucosa were also improved in response to MEER, which was not observed after HEER inclusion. Overall, MEER seems to be a better choice of treatment owing to its more effective benefits on broiler performance, ileal microbiota, gut morphology and antioxidant ability of the intestinal mucosa.     

Influence of probiotic supplementation on blood parameters and growth performance in broiler chickens

Effects of commercial probiotic (Bactocell®) on growth performance and blood parameters were evaluated. A total of 800 one day-old Ross broiler chicks were raised over 42 days. Chicks were wing-banded, weighed individually and randomly allocated into four equally major groups each having two replicates. Chicks of group 1 (control group) were fed the starter and finisher diets that did not supplemented with probiotic. The chicks of groups 2, 3, and 4 were fed the control starter and finisher diets supplemented with 1.6 g, 1 g and 0.8 g of probiotic per kg feed, respectively. Weekly body weight, feed consumption and feed conversion were measured. Blood parameters at 1, 4 and 6 weeks of age including packed cell volume (PCV), haemoglobin (Hb), total protein, albumin, total lipid and cholesterol were determined. All birds were kept under similar environmental, managerial and hygienic conditions. The results of the current study revealed that there was no significant change for Hb and PCV concentrations among different groups at all studied times. Also, total protein, lipids and albumin concentrations were not affected by probiotic supplementation. Chicken fed a diet containing various levels of probiotic showed a significant decrease (p ⩽ 0.05) in cholesterol concentration compared to control group. Probiotic supplementation significantly increased the body weight and daily weight gain of broiler chicks at late ages (3–6 weeks). Also, the birds fed on probiotic levels 1 and 0.8 g/kg diet exhibited higher body weight among chicken groups at 6 weeks of age. Improved feed conversion was noticed in birds fed a diet supplemented with probiotic. There was no significant difference in mortality rate among groups. We concluded that use of selected commercial probiotic resulted in improved performance parameters and reduced serum cholesterol in broiler chickens. Moreover, supplementation of the probiotic to broilers in the levels of 1 and 0.8 g/kg diet was found to be better than control and 1.6 g/kg level indicating that increasing dietary probiotic level does not has the best performance.     

Effects of zinc bacitracin, bird age and access to range on bacterial microbiota in the ileum and caeca of broiler chickens

Aims: Determining the effects of zinc bacitracin, bird age and access to range on bacterial microbiota in the ileum and caeca of broilers. Methods and Results: 16S rRNA gene-based polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR–DGGE) profiling, DNA sequencing and real-time quantitative PCR techniques were used. The richness of both ileal and caecal microbiota increased with chicken age. The microbiota from those birds of the same age demonstrated relatively similar PCR–DGGE profiles and tended to form closely related clusters in the relatedness analyses. Dietary treatment with bacitracin (50 mg kg⁻¹) and access to range did not change the richness but altered the composition of the microbiota. The impact of bacitracin was particularly obvious in 3-day-old chicks. Lactobacilli were abundant in the caecal microbiota of 3-day-old chicks regardless of the dietary treatment with bacitracin. The access to range enriched Bifidobacterium in both the ileum and caeca. Conclusions: Bacitracin, bird age and access to range all influenced bacterial microbiota in the ileum and caeca of broilers, with bird age having the greatest apparent effect. Significance and Impact of the Study: Providing useful information for the development of antibiotic replacement therapy for poultry production.     

Effects of Lactobacillus casei and Enterococcus faecalis on growth performance,immune function and gut microbiota of suckling piglets

This study was carried out to investigate the effects of orally administrated Lactobacillus casei and Enterococcus faecalis on performance, immune function and gut microbiota of suckling piglets. Neonatal piglets (n = 120) were randomly assigned to 4 groups, with 30 suckling piglets in each group. The piglets were from 15 litters, one male and one female piglet were selected for each group in each litter. The Control group was administrated with normal saline, the other groups with L. casei or E. faecalis or a combination of L. casei and E. faecalis at a ratio of 3:1. Each piglet was orally administrated with 1, 2, 3 and 4 ml probiotics or normal saline at the age of 1, 7, 14 and 21 d, respectively. The piglets were weaned at the age of 21 d. The results showed that compared with the Control group, the average daily gain of piglets administrated with probiotics was significantly increased, and the diarrhoea rate and mortality were significantly decreased (p < 0.05). After supplementation of the combined probiotics, the protease activity in stomach, duodenum and colon was increased and in all supplemented groups, the immunoglobulin A concentration in plasma was significantly higher (p < 0.05). The combined probiotics significantly increased villus length and the expression level of transforming growth factor-β in the jejunum (p < 0.05) but decreased the expression level of the jejunal tumour necrosis factor-α (p < 0.05). In addition, probiotics could regulate gut microbiota and increase microbial similarity coefficients for keeping piglet gut microbiota stable.     

Influence of method of whole-wheat feeding on the performance,digestive tract development and carcass traits of broiler chickens

The present study was conducted to investigate the effects of feeding whole wheat either through a mixed feeding (MF) or free choice feeding (FCF) system on the performance, digestive tract development and carcass traits of broiler chickens. The following three treatments, based on wheat and soybean meal, were employed: GW, ground-wheat diet with 600–690 g wheat kg⁻¹; MF, GW diet with 490–500 g wheat kg⁻¹ and 100–200 g whole wheat kg⁻¹; and FCF, whole wheat and a protein concentrate offered in separate feeders. Each diet was fed to six pens of 36 birds each from day 7 to 35 post-hatch. Over the 7–35-day trial period, no differences (P>0.05) were observed between the weight gain, feed intake and feed per gain of broilers receiving the GW and MF treatments. Birds receiving the FCF treatment had the lowest (P<0.05) weight gain and feed intake, and the highest (P<0.05) feed per gain. During week 1 of the trial, the protein concentrate was consumed more than the whole wheat (0.69 vs. 0.31) in the FCF treatment, resulting in the amount of concentrate offered being restricted during subsequent weeks. Over the trial period, the average consumption of protein concentrate remained high (0.56 of the total intake). Both whole-wheat treatments increased (P<0.05) the relative gizzard weights. Factors that affect diet selection such as learning and previous experience, visual differences between the foods, texture and flavour of the food, and palatability may explain the lower whole-wheat intake in the FCF treatment. In this study, whole wheat was introduced only on day 7 and it is possible that the birds may have to be trained to experience choice feeding from the first week of life. However, the present results suggest that FCF may not be an appropriate feeding system for fast growing modern broilers.     

Effects of feeding intact,ground and/or pelleted rapeseed on nutrient digestibility and growth performance of broiler chickens

ABSTRACT

In this study, the effect of grinding or pelleting of rapeseed on the digestibility, apparent metabolisable energy (AME_N), growth performance and gizzard weight of broiler chickens was evaluated. In Exp. 1, four treatments were tested (240 broiler chickens, 20 replications, 3 birds per cage). Birds received either a basal diet or were fed with rapeseed of different sized particles (fine, medium and coarse ground, respectively). In Exp. 2, 10 treatments were assessed (360 chickens, 12 replications, 3 birds per cage), where five different diets (a basal diet and four diets with intact rapeseed, fine ground, medium ground or coarse ground rapeseed, respectively) were fed non-pelleted or pelleted. In Exp. 3, two treatments were compared (224 broiler chickens, 14 replications, 8 birds per floor pen): fine ground rapeseed (FG) and intact rapeseed (IS). Compared with medium and coarse ground rapeseed, fine grinding increased in Exp. 1 the AME_N of rapeseed and the precaecal digestibility (PD) of dry matter and ether extract (EE) (p < 0.05). In Exp. 2, the content of AME_N and the PD of EE and crude protein (CP) increased as the degree of grinding increased when diets were not pelleted (p < 0.01). In contrast, the significantly highest values for these parameters were measured after pelleting without effect of grinding, resulting in a significant interaction between pelleting and grinding (p < 0.001). In Exp. 3, performance of chickens was not affected by dietary treatments, but gizzard weight and the PD of CP were higher when IS were included in the diet (p < 0.05). The results suggested that fine grinding may be used to increase the feeding value of full-fat rapeseed for broiler chickens. Nevertheless, pelleting of diets with rapeseed seemed to be much more effective in the reduction of particle size than grinding.     

Settlement, early growth and survival of Haliotis rubra in response to different algal species

Five diatom species were isolated from settlementplates at Southern Ocean Mariculture, Victoria,Australia (Navicula sp., Naviculajeffreyi, Cylindrotheca closterium, Cocconeis sp., Amphora sp.) and tested insettlement experiments with Haliotis rubralarvae. Settlement was very low on single speciesdiatom films and varied between 1%–6%. Depending onthe species combination larvae preferred to settle onfilms with mixed diatom species than single speciesfilms. The highest settlement was achieved with amixed film of Navicula sp. and Amphora sp.Five and ten-day-old germlings of Sporolithondurum induced settlement of the abalone Haliotisrubra. However, the settlement rate was significantlylower on germlings than on the whole thallus of thealga. Germlings inoculated with the diatom Navicula sp. induced higher settlement than films ofthe diatom species alone. High settlement of up to52% was also achieved with germlings of the greenalga Ulvella lens. Settlement was reduced onU. lens squares inoculated with the diatom Navicula sp. but higher than on films of the diatomalone. The settlement rate was higher if plates withU. lens were previously grazed by juvenileabalone.Post-larval growth rates were higher on monospecificdiatom films than on U. lens or on S.durum. The best growth rate was obtained with Navicula sp. U. lens and S. durum areboth good settlement inducers, but are notsufficient to support rapid growth of young H.rubra post-larvae. Survival was low on U. lensand on the diatom C. closterium. We suggest thatcommercial nursery plates seeded with U. lenswill result in high and consistent settlement, whilean inoculum with Navicula sp. will ensuresufficient food for rapid growth of the post-larvae.     

Effects of conjugated linoleic acids on growth performance, serum lysozyme activity, lymphocyte proliferation, and antibody production in broiler chicks

This study was conducted to investigate the effect of dietary conjugated linoleic acids (CLA) on growth performance and immune responses in broiler chicks. A total of 240 day-old Arbor Acre male broiler chicks were randomly allotted into four dietary treatments with different inclusion levels of CLA (0, 2.5, 5.0 or 10.0 g/kg) for six weeks. Growth performance, peripheral blood lymphocyte (PBL) proliferation, lysozyme activity, phagocytic activity (carbon clearance) and serum antibody titers against Newcastle disease virus (NDV) vaccine were examined. There were no significant differences in growth performance among treatments (p > 0.05). Chicks fed CLA diets produced more lysozyme activity in serum than the control group at 2 and 6 weeks of age (p < 0.05). Dietary CLA enhanced the PBL proliferation in response to concanavalin A (ConA) at the age of 42 d (p < 0.05). Phagocytic ability was also affected by dietary CLA and chicks fed CLA diets had faster carbon clearance rate (p < 0.05), but antibody titers to NDV was not influenced by dietary CLA. The results of the study suggested that dietary CLA could enhance innate and cellular immune response in broiler chicks, and not affect the growth performance.     

Impact of feed supplementation with antimicrobial agents on growth performance of broiler chickens, Clostridium perfringens and enterococcus counts, and antibiotic resistance phenotypes and distribution of antimicrobial resistance determinants in Escherichia coli isolates

The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7- to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), bla(TEM), sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for bla(CMY-2). The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.     

Effects of conjugated linoleic acids on growth performance,serum lysozyme activity,lymphocyte proliferation,and antibody production in broiler chicks

Abstract

This study was conducted to investigate the effect of dietary conjugated linoleic acids (CLA) on growth performance and immune responses in broiler chicks. A total of 240 day-old Arbor Acre male broiler chicks were randomly allotted into four dietary treatments with different inclusion levels of CLA (0, 2.5, 5.0 or 10.0 g/kg) for six weeks. Growth performance, peripheral blood lymphocyte (PBL) proliferation, lysozyme activity, phagocytic activity (carbon clearance) and serum antibody titers against Newcastle disease virus (NDV) vaccine were examined. There were no significant differences in growth performance among treatments (p > 0.05). Chicks fed CLA diets produced more lysozyme activity in serum than the control group at 2 and 6 weeks of age (p < 0.05). Dietary CLA enhanced the PBL proliferation in response to concanavalin A (ConA) at the age of 42 d (p < 0.05). Phagocytic ability was also affected by dietary CLA and chicks fed CLA diets had faster carbon clearance rate (p < 0.05), but antibody titers to NDV was not influenced by dietary CLA. The results of the study suggested that dietary CLA could enhance innate and cellular immune response in broiler chicks, and not affect the growth performance.     

Effects of dietary inclusion of triticale,rye and wheat and xylanase supplementation on growth performance of broiler chickens and fermentation in the gastrointestinal tract

An experiment was performed over a period of 5 weeks with 576 one-day-old cockerels (Cobb 500), which were randomly divided into 6 experimental groups (12 replicate cages with 8 birds/cage). The objective of the experiment was to estimate whether different grain types (wheat, rye or triticale) and exogenous xylanase inclusion influence the performance and the gastrointestinal ecosystems of broiler chickens as regards intestinal viscosity, pH as well as the concentration of short-chain fatty acids (SCFA) and lactic acid (LA). The rye-based diets resulted in the poorest production results followed by wheat and triticale-based diets. Ileal viscosity decreased in the range: rye (140 cps), triticale (6.1 cps) and wheat (2.5 cps). Xylanase supplementation reduced ileal viscosity significantly only in birds fed with rye. The cereal type influenced the fermentation process in the broiler gastrointestinal tract more than the xylanase supplementation. The total concentration of organic acids was highest in the caeca, followed by the crop, ileum and gizzard. Lactic acid concentrations were highest in the content of the crop followed by ileum, gizzard and caeca. Propionate was only detected in caecal contents, whereas butyrate was also found in small amounts in the contents of the crop of birds from all treatments. The concentrations of acetate, butyrate and total organic acid concentration in caecal contents of chickens receiving the rye-based diets were lower than in birds fed the other cereals (P<0.001). Enzyme supplementation reduced the relative weight of the caeca in rye-fed birds (P=0.001).     

Periodic usage of low-protein methionine-fortified diets in broiler chickens under high ambient temperature conditions: effects on performance,slaughter traits,leukocyte profiles and antibody response

This study was performed to evaluate the effects of adding methionine supplements to low-protein diets and subsequent re-feeding with a normal diet on the productive performance, slaughter parameters, leukocyte profiles and antibody response in broiler chickens reared under heat stress conditions. During the whole experimental period (6–49 days), the birds were raised in battery cages located in high ambient temperature in an open-sided housing system. A total of 360 6-day-old male chickens were divided into six treatments in six replicates with ten chicks each. Six isoenergetic diets, with similar total sulfur amino acids levels, were formulated to provide 100 and 100 (control), 85 and 100 (85S), 70 and 100 (70S), 85 and 85 (85SG), 70 and 85 (70S85G), and 70 and 70 % (70SG) of National Research Council recommended levels for crude protein during the starter (6–21 day) and grower (22–42 day) periods, respectively. Subsequently, all groups received a diet containing the same nutrients during the finisher period (43–49 day). The results showed that, under heat stress conditions, average daily gain and feed conversion ratio and performance index from day 6 to 49, breast and thigh yields and antibody titer against Newcastle disease in the birds fed diets 85S, 70S and 85SG were similar to those of birds fed control diet, whereas feeding diets 70S85G and 70SG significantly decreased the values of above-mentioned parameters. Additionally, diets 85S, 70S and 85SG significantly decreased mortality rate and heterophil:lymphocyte ratio compared with the control diet. In conclusion, the results indicate that supplementation of methionine to diets 85S, 70S and 85SG, and then re-feeding with a conventional diet is an effective tool to maintain productive performance and to improve health indices and heat resistance in broilers under high ambient temperature conditions.     

Effects of dietary supplementation of keratinase on growth performance, nitrogen retention and intestinal morphology of broiler chickens fed diets with soybean and cottonseed meals

A preparation of keratinase (KE, 400,000 enzyme units/g) was evaluated as a feed additive for its effects on growth performance, nutrient digestibility and intestinal development in broiler chickens. Four experimental diets were arranged as a 2 × 2 factorial with two sources of protein, either soybean meal (SBM) alone or a combination of SBM and cottonseed meal (1:1 on crude protein basis) and with or without 1.0 g KE/kg diet. Dietary supplementation of KE increased body weight gain from 1 to 21 days of age and improved feed conversion ratio from 1 to 42 days of age. Also, KE supplementation enhanced nitrogen retention (P<0.001) and starch digestibility (P<0.001), reflecting the high level of KE and some amylase activities in the enzyme preparation. Microscopic examination of the small intestine on day 21 indicated that KE increased the ratio of villus height to crypt depth (P<0.05). The results suggest that KE has positive effects on growth performance, dietary component digestibility and intestinal development of broilers.     

Effect of graded levels of rapeseed oil in isonitrogenous diets on the development of the gastrointestinal tract,and utilisation of protein,fat and energy in broiler chickens

The effect of feeding 0, 4, 8 and 16% rapeseed oil from 12–42 days of age was studied in broiler chickens on performance, digestibility of nutrients, and development of gastrointestinal tract, protein and energy metabolism. Thirty six female chickens (Ross 208) with initial body weight average 246 g were allocated to the four groups and kept pair-wise in metabolism cages. The chickens were fed similar amounts of metabolisable energy (ME) per day and similar amounts of essential amino acids relative to ME by adjusting with crystalline amino acids. The chickens were subjected to four balance periods each of five days with two 24 h measurements of gas exchange in two open-air-circuit respiration chambers inserted on the second and third day of each period. The addition of rapeseed oil increased the amount of gutfill indicating a reduced rate of passage and causing a hypertrophy of the gastrointestinal tract. There was a positive effect on feed utilisation as well as on digestibility especially of dietary fat together with higher utilisation of protein with addition of rapeseed oil. The partial fat digestibility of rapeseed oil estimated by regression was 91.1% and the partial metabolisability (ME/GE) of the rapeseed oil was estimated to 85% yielding an apparent metabolisable energy value of 34.30 MJ/kg.