Effects of different yeast cell wall supplements added to maize- or wheat-based diets for broiler chickens

1. Three experiments were carried out to study the effects of two experimental yeast cell wall (YCW) supplements, one from the yeast extract industry and the other from the brewery industry, added to maize or wheat based-diets, on performance and intestinal parameters of broiler chickens (Ross 308).

2. In the first and second experiments, a completely randomised block design with 4 experimental treatments was used: T-1) Negative control, no additives T-2) Positive control, avilamycin group (10 mg/kg feed), T-3) Yeast extract-YCW (500 mg/kg), and T-4) Brewery-YCW (500 mg/kg feed). There were 6 replicates of 20 (experiment 1) and 22 (experiment 2) chicks per treatment.

3. In experiment 1 (wheat based diets), yeast extract-YCW increased BW and daily feed intake (42 d). The effects were comparable to those of avilamycin. In experiment 2 (maize based diet), avilamycin, yeast extract-YCW and brewery-YCW treatments improved the feed conversion ratio with respect to the negative control group (0 to 14 d).

4. At 24 d, in both experiments, the ileal nutrient digestibility and ileal bacterial counts were not affected by any experimental treatment. In maize diets, lower intestinal viscosity was obtained with avilamycin, yeast extract-YCW and brewery-YCW than with the negative control. In wheat diets, yeast extract-YCW and brewery-YCW reduced intestinal viscosity.

5. A third experiment was conducted to study the effect of yeast extract-YCW on animal performance, intestinal mucosa morphology and intestinal viscosity. A 2 × 2 factorial arrangement of treatments was used; one factor was the dietary yeast extract-YCW supplementation (0 or 500 mg/kg feed) and the other the cereal in the diet (maize or wheat).

6. At 43 d, the heaviest BW was in chickens fed on yeast extract-YCW compared to those given the negative control. At 22 d, yeast extract-YCW increased villus height, mucus thickness and number of goblet cells with respect to negative control.

7. Results of these experiments suggest that supplementation of yeast extract-YCW to broiler chicken diets increased animal performance by favouring intestinal mucosal development.     

木聚糖酶在肉鸡小麦型日粮中的作用机理

小麦作为主要能量作物之一在粮食工业中已得到广泛应用,其在饲料工业上的应用也越来越受到人们重视,但其含有的抗营养因子在一定程度上限制了其在饲料工业中的应用。小麦中主要的抗营养因子是阿拉伯木聚糖,而向小麦型基础日粮中添加木聚糖酶是消除其抗营养特性的有效办法。文中介绍了小麦型基础日粮中木聚糖的抗营养特性及其对肉鸡生产性能的负面影响,木聚糖酶的作用机理及在肉鸡小麦型日粮中添加木聚糖酶的作用效果,以期为小麦合理地应用于肉鸡日粮提供参考。     

Comparison of the supplemental effects of Saccharomyces cerevisiae and antibiotics in low-protein and high-fibre diets fed to broiler chickens.

Two experiments were completed to compare the supplemental effects of yeast Saccharomyces cerevisiae and sub-therapeutic antibiotics in high-fibre and low-protein diets for broiler chicks. In experiment 1, yeast was added at 1.5, 3.0 and 6.0 g kg-1 while penicillin, tylosin or neoterramycin were added at 150 mg kg-1 into different batches of a high-fibre diet containing 250 g kg-1 palm kernel meal. Saccharomyces cerevisiae and antibiotics increased BW, BWG, FCR, feed intake, carcass and breast weights above the control. Small intestine weight was reduced by antibiotics, while yeast caused a lower deposition of abdominal fat. Liver weights of different treated broilers were similar. The performance indices were superior on penicillin and 3.0 g kg-1 yeast compared to other supplements evaluated. In the second experiment, 1.5 and 3.0 g kg-1 of yeast, and 0.75 mg kg-1 of procaine penicillin, zinc bacitracin and tylosin were separately added to a 180 g kg-1 crude protein diet. Performance of the chicks with additives was compared with unsupplemented negative and positive controls containing 180 and 210 g kg-1 crude protein respectively. Broilers fed with supplements had superior BW, BWG, FCR and feed intake compared to the negative control, but carcass data were similar. Dietary penicillin increased BW, BWG, feed intake more than other supplements, but yeast stimulated higher FCR. Data from both studies indicated that Saccharomyces cerevisiae comparatively increased growth and carcass weight and reduce abdominal fat, therefore, it can serve as a natural substitute for antibiotics in broiler diet.     

Analyses of degradation products from lipid and protein hydrolyses in the small intestine of broiler chickens fed on maize-based diets containing guar gum,or wheat-based diets

1. Three maize diets containing graded levels (0, 0.1, 0.3%) of guar gum and two wheat diets differing in their in vitro viscosities were fed to male broiler chickens (7 to 23 d) for measurements of growth performance and analyses of degradation products from lipid and protein hydrolyses in the small intestine of broiler chickens. Analyses of degradation products were conducted to define which step (hydrolysis or absorption) was most involved in the negative effects of the digesta viscosity on lipid and protein digestibilities. The experiment was also carried out to examine whether effects of wheats could be explained in terms of intestinal viscosity alone. 2. The intestinal viscosities with wheat diets were within the range of those observed with the three maize diets. The correlations between in vivo and in vitro viscosities were higher with real than with potential applied viscosity of diets, both in jejunum and ileum. 3. The mean gain:food ratio observed with wheat diets was lower (P<0.05) than with maize diets despite lower (P<0.05) mean intestinal viscosities in birds given the wheat than given the maize diets. This shows that factors different from intestinal viscosity were also involved in the negative effects of wheats. 4. Distributions of nitrogen compounds in digesta were characterised by low proportions of compounds with high molecular weight (>12,000). For all classes of nitrogen compounds, the contents measured in digesta dry matter did not differ between chickens fed with or without guar gum. 5. Distributions of lipid classes in both jejunum and ileum were characterised by a large proportion of free fatty acids (FFA) and very few triglycerides (TG). In the ileum, FFA and TG contents were both positively correlated with supernatant viscosity, but the slope for FFA content was 35 times higher than for TG. In these relationships, there was no difference between maize and wheat diets. 6. It is concluded that absorption was the main step involved in the lipid digestibility reduction due to intestinal viscosity. For proteins, the most important step (hydrolysis or absorption) involved in decreased digestibility due to intestinal viscosity was not clearly identified.     

Guar meal in diets for broiler chickens

1. In two experiments each involving 2 000 Ross 1 broiler chickens in floor pens from 0 to 56 d of age, the effects of including guar meal at 50, 100 or 150 g/kg of the diet were investigated.

2. During the 0 to 28‐d period diets containing 50 or 100 g guar meal/kg supported only 85 and 69%, respectively, of the growth supported by the control diet, whereas during 28 to 56 d, birds fed on diets containing 100 or 150 g guar meal/kg gained 90 and 86% of the weight gained by control birds.

3. Neither toasting the meal, steam pelleting diets containing the meal nor supplementing these diets with 5 g methionine/kg had any appreciable effect on performance.

4. Addition of either of two enzyme preparations, MKC hemicellulase or betaganase M, improved growth; birds receiving 100 or 150 g guar meal/kg gaining 96 and 89%, respectively, of the weight gained by control birds from 28 to 56 d of age.     

The effect of conditioning temperature and exogenous xylanase addition on the viscosity of wheat-based diets and the performance of broiler chickens

1. A total of 1920 Ross broiler chicks were used in a 6 treatment by 8 replicate growth study to investigate the effect of conditioning temperature and exogenous xylanase addition on diet characteristics and bird performance. 2. Increasing conditioning temperature from 80 to 90 degrees C increased the viscosity of the diets by approximately 6 mPa.s and reduced body weight gain of the broiler chickens by 7%. 3. Furthermore, there was a significant interaction between temperature and the addition of exogenous xylanase, with a proportionately greater positive response to added xylanase in the diets that were pelleted at higher temperatures. 4. Addition of exogenous xylanase also increased the proportion of soluble arabinoxylan in the feed and reduced dietary viscosity, which is likely to be related to the degree of polymerisation of the soluble carbohydrate. 5. These results suggest that conditioning temperature should be considered as a factor when attempting to predict the response of broilers to added xylanase, especially when high-viscosity or 'low-quality' wheat is being used. 6. It can be concluded that pelleting wheat-based diets above 80 degrees C can compromise bird performance and that, if higher temperatures are to be employed, the use of exogenous xylanase is critical to maintain productivity.     

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

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

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

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

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

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

Effects of a mono-component endo-xylanase supplementation on the nutritive value of wheat-based broiler diets

1. Two trials were conducted to evaluate the effects of a mono-component thermostable endo-1,4-β-xylanase derived from Thermomyces lanuginosus on the nutritive value of wheat-based broiler diets. In a 5-week growth trial, the efficacy of xylanase supplementation at 0, 100, 150, 200, 400 and 4000 FXU/kg diet was evaluated. A short-term balance trial was carried out according to a 4?×?2 factorial arrangement of treatments, involving 4 wheat cultivars and endo-xylanase at 0 or 200 FXU/kg.

2. In the growth trial, enzyme supplementation from 0 to 400 FXU/kg reduced feed intake and improved feed conversion linearly. Digesta viscosity was significantly reduced by all enzyme inclusion levels by 49·6–56·9%, in a quadratic manner.

3. In the balance trial, xylanase supplementation resulted in a significant improvement of protein, lipid and dry matter apparent digestibility coefficients of diets, accompanied by improved dietary AME _N values. There was a significant wheat?×?enzyme interaction on AME _N and lipid digestibility. There was a significant effect of wheat cultivar on dry matter digestibility.     

The effects of adding xylanase, vitamin C and copper sulphate to wheat-based diets on broiler performance

1. The study used a 3 x 3 factorial design to evaluate the effects of 3 additives (none; vitamin C [250 mg/kg]; copper sulphate [250 mg/kg]) and 3 enzyme additions (none; Avizyme 1300 [Finnfeeds Ltd, 1 g/kg in food]; Avizyme 1310 [liquid spray, post-pelleting, 0.5 g/kg]). All experimental diets were mixed, heat-conditioned (80 degrees C for 2 min) and pelleted. Copper sulphate (diets NCu; DCu; LCu) and Avizyme 1300 (diets DN; DC; DCu) were added during mixing. Vitamin C was sprayed at 10 ml per kg (diets NC; DC; LC) and the liquid enzyme was diluted 20-fold and sprayed at the same rate (diets LN; LC; LCu), post-pelleting. 2. Additive or enzyme addition did not significantly affect DM intake or liveweight gain (LWG). Enzyme addition improved gain:food (P=0.014), AME:GE (P<0.001), ileal apparent digestibility of DM (P=0.008) and starch (P<0.001), faecal apparent digestibility of starch, crude fat and NDF (P=0.008; <0.001; <0.001 respectively) and reduced in vivo viscosity (P<0.001). 3. Copper sulphate addition depressed gain:food (P=0.047), AME:GE (P=0.002), ileal apparent digestibility of starch (P<0.001) and faecal apparent digestibility of starch (P=0.003) and crude fat (P<0.001) due to a negative additive x enzyme interaction when copper sulphate and dry enzyme were included together. 4. Vitamin C decreased in vivo viscosity by 20% but failed to have any effect on performance. Both enzyme forms gave similar improvements in performance in the absence of copper sulphate.     

Grass meal as an ingredient in diets for broiler chickens

1. Six diets of equal energy and nitrogen contents containing between 0 (control) and 125 g grass meal/kg were each fed to 4 groups of 42 male and 4 groups of 42 female broiler chicks, in floor pens, from 0 to 56 d of age.

2. Increments of 25 g grass meal/kg and 7.3 g maize oil/kg replaced a mixture of soyabean, wheat and barley meals in the control diet.

3. Gain: food ratio (y) of the birds decreased linearly as dietary grass meal content (x) increased such that y = 0.4295 ? 0.0032x.

4. Carcass analyses indicated that the decrease in gain : food ratio was caused by less deposition of body fat.

5. Skin colour became significantly yellower as the dietary grass meal content increased.     

Caecal microbiota of chickens fed diets containing propolis

The present study aimed to evaluate the effect of different levels of ethanolic extract of propolis (EEP) and raw propolis (RP) on broiler performance and on selected bacterial groups in caecal microbiota using fluorescent in situ hybridization (FISH) measured by fluorescent activated cell sorting. Two experiments were conducted with 120 male chicks from 1 to 21 days of age for each, raised in cages and distributed in a completely randomized experimental design; there were five replicates with four birds per experimental unit and six treatments for each experiment (trial 1 – EEP – 0, 1000, 2000, 3000, 4000 and 5000 ppm and trial 2 – RP – 0, 100, 200, 300, 400 and 500 ppm). Fluorescent probes were used against the bacterial groups in caecal samples collected at 21 days of age. The data were subjected to one‐way anova followed by Tukey's and regression analyses were used to assess the relationship between dietary levels of EEP or RP on performance and intestinal microbiota (p < 0.05). In the trial 1, results showed that the EEP did not cause any significant (p > 0.05) modification in the performance and caecal microbiota. In the trial 2, RP inclusion did not affect the performance but changed the bacterial composition (p < 0.05). Clostridiaceae, Gammaproteobacteria excluding Enterobacteriaceae and Lactobacillus spp. showed a quadratic response (p < 0.05), with the lowest value predicted to occur at 240 ppm, 221 ppm and 213 ppm of RP respectively. The proportion of Bacteroidaceae and Gammaproteobacteria did not differ (p > 0.05) among the experimental groups. The inclusion of ethanolic extract of propolis did not affect the performance and intestinal microbiota, whereas the supplementation of raw propolis modulates the caecal microbiota composition without any effects on chicken performance.     

Effects of feeding growing broiler chickens with practical diets containing sweet lupin (Lupinus angustifolius) seed meal

1. Two experiments with growing broiler chickens were carried out to study the effects of the inclusion in their diets of whole or dehulled lupin (Lupinus angustifolius) seed meal on productive and physiological parameters. The effects of the addition of a commercial protease (1 g/kg, Bio-Feed Pro, Novo. Nordisk, Madrid) were also tested. 2. Diets were formulated to contain the same amounts of energy (12.55 kJ/g) and protein (210 g/kg). Raw whole (not heat treated) or dehulled sweet (low in alkaloids) lupin seed meal (400 and 320 g/kg, respectively) were used to formulate the lupin-based diets, and the protein content was completed with either defatted soybean or casein. 3. Final body weight and feed intake of chickens fed diets containing whole lupin seed meal (400 g/kg) were lower than controls, but gain:feed ratios were not different. The presence of soybean or casein in the diet did not affect productive parameters. Birds fed dehulled (320 g/kg) instead of whole lupin seed meal had similar body weight, feed intake and gain:feed values to controls. The addition of a commercial protease (1 g/kg, Bio-Feed Pro CT) to whole lupin/soy or whole lupin/casein diets tended to increase feed intake and final weight of the birds. 4. Plasma uric acid concentration was higher, and plasma cholesterol and triglycerides lower, in chicks fed whole lupin but not in those fed dehulled lupin seed meal. Plasma amino acid concentrations were not different from controls in birds fed lupin diets. 5. Apparent ileal digestibility of amino acids was not different from controls for the different lupin diets. The relative weight of the liver was higher than controls in lupin-fed birds, but not in those fed enzyme supplemented lupin-based diets. Liver concentrations of DNA tended to rise, while those of glycogen tended to decrease and liver RNA was lower in lupin-fed chicks.     

Evaluation of xylanase in low-energy broiler diets

The objective of the current study was to evaluate the effect of feeding a thermo-tolerant xylanase in low-energy broiler diets on performance and processing parameters. Evaluation criteria included average broiler BW, FCR, livability, carcass yield, and fat pad yields. The experimental design consisted of 3 nutrient profiles: positive control, negative control 1 (−66 kcal/kg), and negative control 2 (−132 kcal/kg). Two xylanase inclusion programs were included in the negative control 1 and 2 diets; 60 g/t was included in the starter and grower diets with either 60 or 100 g/t in the finisher and withdrawal diets, yielding a total of 7 treatment groups with 8 replicate pens per treatment each containing 42-d-old straight-run chicks per treatment (2,352 total broilers). Broilers were reared in floor pens through 45 d of age. The dietary program consisted of 5 dietary phases: starter (1–15 d), grower 1 (16–23 d), grower 2 (24–31 d), finisher (32–38 d), and withdrawal (39–45 d). Body weights and feed consumption were determined on days of dietary changes, including d 15, 23, 31, 38, and 45. On d 45, 4 male and 4 female broilers per replicate (448 total) were subjected to an 8-h feed withdrawal period and processed to obtain carcass and fat pad weights. Reducing the dietary energy level increased FCR and decreased the fat pad weight of broilers in the negative control 2 treatment compared with the positive control. Inclusion of xylanase during the starter phase increased d 15 BW and reduced FCR. The inclusion of xylanase continued to reduce FCR throughout the trial, as compared with diets without xylanase inclusion. Within this study, we have demonstrated the effectiveness of xylanase inclusion in reduced-energy diets (−66 and −132 kcal/kg) to improve FCR of broilers to that of broilers fed energy-adequate diets.     

Performance and physiological responses of broiler chickens to supplemental guanidinoacetic acid in arginine-deficient diets

1. The present experiment was designed to examine arginine (Arg)-sparing effects of guanidinoacetic acid (GAA) on production performance, intestinal morphology and certain blood parameters in broiler chickens.

2. A total of 300 male broiler chicks (Ross 308) were randomly allotted to 5 dietary treatments in a completely randomised design during 1–15 and 15–35 d rearing periods. Experimental treatments consisted of a basal diet with a reduction in Arg content (CON?; starter: 12.1 g/kg and grower: 11.3 g/kg Arg), a CON? diet supplemented with synthetic Arg equal to the required Arg level (CON+; starter: 13.80 g/kg; grower: 12.37 g/kg) and CON? diet supplemented with three levels of GAA (GAA0.6; GAA1.2; and GAA1.8; g/kg).

3. Supplemental GAA at 0.6 and 1.2 g/kg reduced the adverse effects of the CON? diet on weight gain and feed conversion ratio in the starter period, equal to the effect of CON+ diet. During the entire rearing period, such an effect was only seen for broilers fed CON? diet supplemented with 1.2 and 1.8 g/kg GAA (P < 0.05). Proportional weights of liver and abdominal fat were decreased in birds fed diets containing supplemental Arg and 1.8 g/kg GAA compared to the CON? broilers (P < 0.05). Jejunal villus height and villus height to crypt depth ratio were increased in broilers receiving the CON? diet (P < 0.05). Serum concentration of nitric oxide increased when the CON? diet was supplemented with either Arg or 1.8 g/kg GAA (P < 0.05).

4. Dietary inclusion of GAA had an Arg-sparing effect, whereby 1.2 and 1.8 g/kg of supplemental GAA resulted in greater growth performance during the starter and entire rearing periods, respectively. Supplementation with 1.8 g/kg GAA had significant effects on some carcass and physiological parameters.     

Fatty acid and energy metabolism in broiler chickens fed diets containing either beef tallow or an oil blend

The hypothesis tested was that the feeding of n‐6 polyunsaturated fatty acids (PUFA) results in more whole‐body fatty acid oxidation than the feeding of saturated fatty acids (SFA). It was reasoned that the increased fatty acid oxidation would be associated with enhanced whole‐body energy expenditure and stimulated de novo fatty acid synthesis. To put the hypothesis to the test, broiler chickens were fed diets containing either beef tallow as source of SFA or an oil blend as source of n‐6 PUFA. The broilers either had free access to their diet or were fed a restricted amount. Seven‐day‐old, male broiler chickens were used; they were kept individually in cages from 1 to 4 weeks of age. In the birds fed ad libitum, the n‐6 PUFA diet reduced average daily feed intake (ADFI), but did not significantly affect average daily weight gain (ADG) and the feed:conversion ratio (FCR). The lower ADFI on the n‐6 PUFA diet was associated with a higher apparent digestibility of total fatty acids. The ratio of deposition in the body to intake of digestible total PUFA, which reflected n‐6 PUFA, was significantly decreased by the n‐6 PUFA diet, pointing at preferentially increased n‐6 PUFA oxidation on the n‐6 PUFA diet. The ratio for n‐9 monounsaturated fatty acids (MUFA) was higher than 1.0, which agrees with net de novo synthesis, but the n‐6 PUFA diet induced a lower value than did the SFA diet. Feeding either the n‐6 PUFA or SFA diet did not influence energy expenditure expressed as percentage of energy intake. This study supports the idea that dietary n‐6 PUFA instead of SFA are preferentially oxidized, but no proof was obtained for enhanced energy expenditure and contrary to the hypothesis put forward, the n‐6 PUFA diet depressed de‐novo fatty acid synthesis.     

Comparison of performance and intestinal characteristics of broiler chickens fed on diets containing whole,rolled or ground barley

1. In two experiments, no consistent differences in weight gain or food intake appeared between broiler chickens given diets based on whole or rolled barley, but food: gain ratio and gizzard weight as a percentage of live weight were reduced (P<0.05) when barley was rolled. Grit addition did not affect performance or intestinal characteristics.

2. In a third experiment, whole barley diets gave significandy higher weight gain than ground barley diets; this was attributable to the significandy higher food consumption. Gizzard weight as a percentage of live weight increased (P< 0.05) when whole barley was fed, while foodrgain ratio was not significandy (P>0.05) affected by the form of barley.

3. The number of particles in the intestinal contents with sizes larger than 2.4 mm was not significantly (P<0.05) different between broiler chickens fed on whole barley and those fed ground barley, but the number of particles with sizes between 2.4 and 0.7 mm was lower (P< 0.05) when diets with whole barley were fed.

4. Enzyme addition increased (P< 0.05) weight gain and the DM of intestinal contents, and decreased (P<0.05) intestinal viscosity, food:gain ratio and pancreas weight as a percentage of live weight regardless of form of the barley.     

Evaluation of an intestinal Lactobacillus reuteri strain expressing rumen fungal xylanase as a probiotic for broiler chickens fed on a wheat-based diet

1. This study was conducted to evaluate the feasibility of using a transformed Lactobacillus reuteri Pg4 strain harbouring a rumen fungal xylanase gene as a probiotic supplement in a wheat-based poultry diet. 2. A total of 400 broiler chicks was allocated to two treatment groups with or without supplementation with 10(6) colony forming units (cfu)/g of transformed L. reuteri Pg4 in a wheat-based regimen to investigate the performance, intestinal microflora populations, digesta viscosity and excreta ammonia concentrations in these broiler chickens. 3. Supplementation of the wheat-based diet with transformed L. reuteri Pg4 decreased intestinal viscosity, caecal coliform population, and increased body weight gain and ileal villus height and crypt depth from 0 to 21 d of age. It also decreased excreta ammonia concentrations, and increased the caecal total volatile fatty acid (VFA) and lactic acid concentrations from 0 to 21 d and 22 to 37 d of age. 4. Further, it was demonstrated that 40% of the Lactobacillus cells randomly isolated from the digesta of the ileum and caecum of the supplemented group possessed xylanase secretion capability. 5. It appears reasonable to assume, therefore, that the derived benefit is a result of the organism surviving, and the associated performance of some function in the intestinal tract which benefits gut health.     

Feeding dihydroquercetin to broiler chickens

1. A total of 80 male Ross 308 broilers were used in a study to investigate the effect of dietary dihydroquercetin (DHQ) on growth performance variables, gastrointestinal tract (GIT) and immune organ development, glutathione peroxidase (GPx) and haemoglobin in blood, hepatic vitamin E content, dietary N-corrected metabolisable energy (AMEn) and nutrient retention coefficients when fed to broiler chickens from 7 to 35 d of age.

2. Two treatments were used in this study: control (C) and C + 0.5 g/kg extract of Siberian Larch (Larix sibirica) per kg feed, containing 85% DHQ. The diets were fed over 2 feeding phases, a grower phase from 7 to 28 d of age and a finisher phase from 28 to 35 d of age. The birds were reared under the breeder’s recommended conditions.

3. In general, there were no effects of DHQ on growth performance of broiler chickens. However, the results of this experiment showed that there can be changes in the redness colour of the breast meat when DQH is fed. No negative effects of feeding DHQ at 0.5 g/kg diet were observed in this study.

4. Supplementation of poultry diets with DHQ under standard industry-rearing conditions did not improve the performance or any of the studied variables, except an increase of redness index of the breast fillets. Feeding DHQ at different doses and/or under more challenging conditions, e.g. heat stress, may, however, bring positive responses.     

Rearing conditions influence nutrient availability of plant extracts supplemented diets when fed to broiler chickens

The effects of a standardised mixture of essential oils, including 5% carvacrol, 3% cinnamaldehyde and 2% capsicum (XT 6930; Pancosma S.A), on dietary apparent metabolisable energy corrected for nitrogen retention (AMEn), nutrient digestibility and mucin secretions, measured as sialic acid (SA) were investigated in broilers fed on the same diet but reared under different conditions, that is, cages and floor pens littered with wood shavings used in previous broiler study. The use of XT reduced (p < 0.05) nitrogen digestibility (0.585 vs. 0.544) and tended (p = 0.072) to reduce dry matter digestibility (0.733 vs. 0.717) of the diet when fed to birds reared in cages. However, XT supplementation improved (p < 0.05) fat digestibility (0.844 vs. 0.862) and tended (p = 0.093) to increase AMEn (14.01 vs. 14.25 MJ/kg DM) of the same diet when fed to broilers reared in floor pens. Essential oils supplementation tended (p = 0.059) to increase the secretion of SA, when fed to birds reared in cages (11.24 vs. 14.18 μg), but did not influence (p > 0.05) the SA secretion from birds reared in floor pens. The results obtained from the cage study tend to be the opposite of those obtained from the floor pen study. This suggests that the efficiency of dietary plant extracts may be influenced by the rearing/hygienic conditions of poultry. Based on the overall results, it can be concluded that information on rearing conditions should be taken into account for more complete interpretation of the experimental data emanating from experiments involving use of essential oils typified by those considered in this study.