Wheat-based Broiler Diets Research Articles

Dietary crude protein reductions in wheat-based diets with two energy densities compromised performance of broiler chickens from 15 to 36 days post-hatch

This study was designed to investigate the impacts of 2 energy densities (13.0 and 12.5 MJ/kg ME) in wheat-based diets with 3 tiers of CP concentrations (210, 190, and 170 g/kg) on the performance of broiler chickens. The parameters assessed included growth performance (15-36 d posthatch), carcass traits, nutrient utilization, starch-protein digestive dynamics, apparent ileal amino acid digestibility coefficients, and the free amino acid and ammonia (NH3) concentrations in systemic plasma. Also, the feasibility of substituting soybean meal with canola meal in 190 g/kg CP diets was investigated. The dietary CP reduction from 210 to 170 g/kg significantly compromised weight gain by 12.4% (1,890 vs. 2158 g/bird) and FCR by 5.33% (1.501 vs. 1.425). The 0.5 MJ energy density reduction compromised FCR by 3.25% (1.525 vs. 1.477; P=0.013) in birds offered 170 g/kg CP diets. Reducing dietary CP and energy densities interactively influenced (P=0.027) apparent metabolizable energy (AME) and nitrogen corrected metabolizable energy (AMEn) (P=0.022) such that reducing dietary CP increased these parameters but reducing dietary energy densities decreased AME and AMEn. The 150 g/kg canola meal inclusion with the elimination of soybean meal displayed some promise. Dietary CP reductions (and increased nonbound amino acid inclusions) linearly associated with increased plasma ammonia (NH3) concentrations (r=-0.607; P=0.010) and plasma NH3 was linearly related to depressed weight gains (r=-0.565; P=0.018). The association of dietary non-protein-bound amino acid (NPBAA) inclusions and elevated plasma NH3 concentrations have profound implications for the successful development of reduced-CP, wheat-based broiler diets.

The challenge to reduce crude protein contents of wheat-based broiler diets

The challenge to reduce crude protein (CP) contents of wheat-based broiler diets is both justified and formidable because the performance of broiler chickens offered reduced-CP, wheat-based diets is usually compromised. Moreover, broiler chickens offered wheat-based diets do not accommodate CP reductions as well as do those offered maize-based diets; this appears to stem from the higher protein concentrations and more rapid starch digestion rates of wheat. The higher protein concentrations of wheat than maize result in elevated inclusion levels of non-bound (synthetic, crystalline) amino acids (NBAA). This may be an impediment, because non-bound and protein-bound amino acids are not bioequivalent and intestinal uptakes of NBAA are more rapid than their protein-bound counterparts. This leads to post-enteral amino acid imbalances and the deamination of surplus amino acids, which generates ammonia (NH3). Because NH3 is inherently detrimental, it must be detoxified and eliminated as uric acid, which attracts metabolic costs. Moreover, inadequate NH3 detoxification may seriously compromise broiler growth performance. Also, consideration is given to some intrinsic wheat factors, including soluble non-starch polysaccharides, amylase–trypsin inhibitors and gluten, that may hold relevance. Several strategies are proposed that may enhance the performance of birds offered reduced-CP, wheat-based diets, including capping dietary starch:protein ratios, blending wheat with sorghum, whole-grain feeding in association with phytase, dietary inclusions of L-carnitine and the use of protected or slow-release amino acids. In future research, it should prove instructive to compare different wheats with a wide range of protein contents that, importantly, have been fully characterised for relevant parameters, to ascertain the most appropriate properties. The successful development and adoption of reduced-CP, wheat-based diets would be an enormous advantage for the Australian chicken-meat industry as it would diminish the huge dependence on imported, expensive soybean meal.

Identifying the shortfalls of crude protein-reduced, wheat-based broiler diets.

The objective of this review is to identify the shortfalls of wheat-based, crude protein (CP)-reduced diets for broiler chickens as wheat is inferior to maize in this context but to inconsistent extents. Inherent factors in wheat may be compromising gut integrity; these include soluble non-starch polysaccharides (NSP), amylase trypsin inhibitors (ATI) and gluten. Soluble NSP in wheat induce increased gut viscosities, which can lead to compromised gut integrity, which is not entirely ameliorated by NSP-degrading feed enzymes. Wheat ATI probably compromise gut integrity and may also have the capacity to increase endogenous amino acid flows and decrease apparent starch and protein digestibilities. Gluten inclusions of 20 g/kg in a maize-soy diet depressed weight gain and feed intake and higher gluten inclusions have been shown to activate inflammatory cytokine-related genes in broiler chickens. Further research is required, perhaps particularly in relation to wheat ATI. The protein content of wheat is typically higher than maize; importantly, this results in higher inclusions of non-bound amino acids in CP-reduced broiler diets. These higher inclusions could trigger post-enteral amino acid imbalances, leading to the deamination of surplus amino acids and the generation of ammonia (NH3) which, if not adequately detoxified, results in compromised growth performance from NH3 overload. Thus, alternatives to non-bound amino acids to meet amino acid requirements in birds offered CP-reduced, wheat-based diets merit evaluation. The digestion of wheat starch is more rapid than that of maize starch which may be a disadvantage as the provision of some slowly digestible starch in broiler diets may enhance performance. Alternatively, slowly digestible starch may result in more de novo lipogenesis. Therefore, it may prove instructive to evaluate CP-reduced diets based on maize-wheat and/or sorghum–wheat blends rather than entirely wheat. This would reduce non-bound amino acid inclusions by lowering dietary CP derived from feed grains and may enhance starch digestive dynamics by retarding starch digestion rates. Also, the use of biomarkers to monitor gut integrity in broiler chickens is examined where calprotectin, ovotransferrin and possibly citrulline appear to hold promise, but their validation requires further research.

Exogenous xylanase improves broiler production efficiency by increasing proximal small intestine digestion of crude protein and starch in wheat-based diets of various viscosities

Changes in small intestine digestion kinetics and early enzymatic hydrolysis in the crop attributable to xylanase supplementation has not previously been thoroughly studied in relation to animal performance. The current paper reports the effects on broiler performance of a commercial mono-component GH11 xylanase added to normal and high viscous wheat-based broiler diets with emphasis on the site of early enzymatic hydrolysis as indicated by nutrient digestibility kinetics, and visual cereal cell wall degradation.The study was conducted using 2850 1-day old male Ross 308 broilers, allocated to 5 dietary treatments: (1) positive control, an optimized diet based on wheat, soy and corn; (2) negative control; (3) negative control of high viscosity; (4) negative control supplemented with xylanase; (5) negative control of high viscosity supplemented with xylanase. Both negative control and negative control high viscosity diets were reduced in apparent metabolizable energy (starter 3.3 %, grower 7.0 % and finisher 8.5 %) as well as digestible amino acids compared to the positive control, achieved by substituting corn for rye and wheat-coproducts. The xylanase was supplemented at 150 FXU/kg to treatment 4 and 5. Each treatment was fed ad lib to 19 replicated pens of 30 birds. The BW, feed intake (FI) and FCR were measured from d0−35 and intestinal viscosity and nutrient digestibility on d28. Statistical comparisons were performed using a mixed model. All negative controls had higher FI than the positive control regardless of xylanase supplementation. The negative control with high viscosity supplemented with xylanase had an increased BW at d35 compared to all other treatments. The xylanase improved d35 FCR compared to the unsupplemented diets resulting in a European efficiency factor similar to the positive control. Microscopy of digesta samples helped visualize that the exogenous enzymatic degradation of the cereal cell wall components commenced already in the crop and increased throughout the intestinal tract. This was accompanied by reduced jejunal and ileal digesta viscosity for the xylanase supplemented treatments. Depending on diet, the xylanase improved jejunal, but not ileal, digestibility of several nutrients including starch and protein. In conclusion, it is suggested that improved growth performance is caused by an array of multifactorial effects such as viscosity reduction, cell wall degradation and changes in the intestinal site of digestion. The current results display the potential of using xylanase in diets containing what is generally considered as lower quality arabinoxylan rich feedstuffs.

Arabinoxylan-oligosaccharides kick-start arabinoxylan digestion in the aging broiler

While arabinoxylans (AX), an important dietary fiber fraction of wheat-based broiler diets, are known for exerting antinutritional effects in the gastrointestinal (GI) tract of broilers, the prebiotic potential of arabinoxylan-oligosaccharides (AXOS) is also well-documented. However, inconsistent performance responses as well as the effectiveness of low amounts of AXOS used in diets of previously conducted experiments put into question the classical prebiotic route being the sole mode of action of AXOS. The objective of this study was to investigate the effects of dietary AXOS addition on the rate of AX digestion in the gastrointestinal tract of broilers as a function of broiler age to gain more insight into the mode of action of these oligosaccharides. A feeding trial was performed on 480 one-day-old chicks (Ross 308) receiving a wheat-based diet supplemented with or without 0.50% AXOS, containing no endoxylanases. Digesta samples from ileum and caeca and fecal samples were analyzed for AX content, AX digestibility, intestinal viscosity, and microbial AX-degrading enzyme activities at 6 different ages (day 5, 10, 15, 21, 28, 35). Chicks fed from hatching with 0.50% AXOS demonstrated a higher ileal viscosity (P < 0.05). Also higher levels of AX solubilization and fermentation compared to control birds at 10 D were observed. This was noted by the higher total tract AX digestibility of water-extractable AX (WE-AX) and total AX (TOT-AX) at this age (P < 0.05). Although no significant difference in AX-degrading enzyme activities was observed among the dietary treatments, AXOS supplementation in young broilers was shown to stimulate or “kick-start” dietary AX digestion, thereby speeding up the development of a fiber-fermenting microbiome in the young broiler. This stimulation effect of AXOS could enable greater functional value to be extracted from dietary fiber in broiler feeds.

Xylanase and xylo- oligosaccharide prebiotic improve the growth performance and concentration of potentially prebiotic oligosaccharides in the ileum of broiler chickens

ABSTRACT1. The objective of this study was to investigate the effect of supplementing broiler diets with xylanase or xylo- oligosaccharide (XOS) on growth performance, the concentration of non-starch polysaccharide (NSP) hydrolysis products in the ileum and concentration of short chain fatty acids (SCFA) in the caeca of broiler chickens.2. In total, 500 male Ross 308 broilers were used in this 29-day (d) study. The treatments were organised into a 2 × 2 plus 1 factorial arrangement consisting of two additives (xylanase or XOS) at two levels (low or high) plus a control treatment with no additives. This gave five treatments with 100 birds in each treatment group. The diets were slightly deficient in protein by 20 g/kg and energy by 1 MJ/kg.3. On d 14 and 28, two birds per pen were euthanised, the caeca content collected and analysed for short chain fatty acid (SCFA) concentration. On d 29, six birds per pen were euthanised and ileal digesta were collected and analysed for the concentration of NSP fractions.4. On d 14, caecal acetic acid, iso-butyric acid, iso-valeric acid, n-valeric acid and total SCFA concentrations were significantly greater (P ≤ 0.05) when diets were supplemented with XOS compared with xylanase.5. Ileal concentration of arabinose, galactose and glucuronic acid (GlucA2) were significantly greater (P ≤ 0.05) in the insoluble NSP fraction when diets were supplemented with a high level of xylanase, compared with the control treatment. Ileal concentration of fructose was significantly greater (P ≤ 0.05) in the water soluble NSP when a high level of xylanase or low level of XOS were included in the diet compared with the control.6. It was concluded that xylanase and XOS had similar effects on NSP concentration and SCFA in the caeca, although there was little effect on performance. This observation demonstrated further benefits of xylanase supplementation in wheat-based broiler diets beyond digesta viscosity reduction and the release of extra nutrients.

Non-starch Polysaccharide Degrading Enzymes in Corn and Wheat-Based Broiler Diets: Dual Activity for Major Substrates

Non-starch Polysaccharide Degrading Enzymes in Corn and Wheat-Based Broiler Diets: Dual Activity for Major Substrates

Phytase supplementation of maize-, sorghum- and wheat-based broiler diets with identified starch pasting properties influences phytate (IP6) and sodium jejunal and ileal digestibility

The effects of phytase supplementation on growth performance, nutrient utilisation, starch and protein digestive dynamics in broiler chickens offered maize-, sorghum- and wheat-based diets were determined in a previous study (Liu et al., 2014). Responses to phytase were most pronounced in maize-based diets, which suggest that more phytate was degraded in these diets. Relevant retained samples of grain, diets and digesta from four small intestinal segments were retrospectively analysed for concentrations of phytate, sodium and starch pasting properties to investigate the hypothesis that phytate in maize-based diets was more completely degraded by exogenous phytase. Exogenous phytase significantly (P<0.001) degraded dietary phytate in the proximal jejunum, distal jejunum, proximal ileum and distal ileum and increased distal ileal phytate digestibility coefficients from 0.238 to 0.631. There were significant differences (P<0.001) between diets based on maize (0.515), wheat (0.449) and sorghum (0.340) for distal ileal phytate digestibility coefficients. Phytase accelerated phytate disappearance rates from all four segments and increased distal ileal phytate disappearance rates from 201 to 535mg/bird/day. This was significantly more pronounced in maize (459mg/bird/day) than in diets based on sorghum (301mg/bird/day) and wheat (343mg/bird/day). Sodium digestibility coefficients were significantly improved (P<0.01) by exogenous phytase in proximal jejunum, distal jejunum and proximal ileum. Exogenous phytase significantly influenced starch properties of experimental diets determined by rapid visco-analysis (RVA). There were significant negative correlations between RVA setback viscosity of starch in experimental diets and starch digestibility coefficients at the distal jejunum (r=−0.438; P<0.01) and proximal ileum (r=−0.591; P<0.001) determined in the Liu et al. (2014) study. Distal ileal phytate digestibility coefficients appeared to be higher in non-supplemented, maize-based diets (0.349) than in diets based sorghum (0.128) and wheat (0.239) thus the likelihood is that phytate in maize-based diets was more readily degraded by endogenous, mucosal phytase in the small intestine. Consideration is given to the possibilities that location of phytate within grains influences phytate degradation and that the relatively low sodium concentrations in maize-based diets may have contributed to the more robust responses to exogenous phytase observed.

Contribution of protein, starch, and fat to the apparent ileal digestible energy of corn- and wheat-based broiler diets in response to exogenous xylanase and amylase without or with protease

The ileal energy contribution of protein, starch, and fat in response to 2 exogenous enzyme combinations was studied in 2 digestibility assays with 21- (experiment 1; 432 birds) and 42-d-old (experiment 2; 288 birds) Ross 308 broiler chickens. A 2 × 2 × 3 factorial arrangement of treatments with 2 base grains (corn or wheat), without or with high fiber ingredients (corn distillers dried grains with solubles and canola meal), and 3 enzyme treatments was implemented. Enzyme treatments, fed from 12 to 21 d or 32 to 42 d, were 1) without enzymes, 2) with xylanase from Trichoderma ressei (2,000 U/kg) and amylase from Bacillus licheniformis (200 U/kg; XA), or 3) with XA plus protease from Bacillus subtilis (4,000 U/kg; XAP). All diets contained Escherichia coli phytase (500 FTU/kg). Apparent ileal digestibility (AID) of protein, starch, and fat, as well as the apparent ileal digestible energy, were determined using titanium dioxide as inert marker. A generalized mixed model was used to test main effects and 2-way interactions at P < 0.05. An enzyme × grain interaction was detected for AID of starch at 21 and 42 d, and AID of fat at 21 d, with greater effects of enzymes in wheat-based compared with corn-based diets, but significant increments due to enzymes compared with controls in both diet types. Apparent ileal digestibility of fat at 42 d increased with enzyme supplementation compared with the control treatments. The XA and XAP treatments gradually (P < 0.05) increased AID of protein at 21 d, but only XAP increased AID of protein compared with the control at 42 d. Compared with the controls, XA increased AID energy by 52 or 87 kcal, and XAP by 104 or 152 kcal/kg of DM at 21 or 42 d, respectively. The caloric contribution of starch, fat, and protein were affected differentially by base grain and the presence of fibrous ingredients at 21 and 42 d of age.

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.

Evaluation of wet-feeding wheat-based diets containing Saccharomyces cerevisiae to broiler chickens

1. This experiment investigated the effects of water and Saccharomyces cerevisiae added to wheat-based diets on gastrointestinal, blood and performance parameters of broiler chickens. 2. A total of 160 one-d-old male broiler chicks were given air-dry or wet diets, with or without S. cerevisiae supplementation (0 and 20 g/kg air-dry feed) ad libitum to 42 d. 3. Feeding broilers with a diet mixed with water in a ratio of 1·2 : 1·0 increased body weight, feed intake, abdominal fat, carcase weight, feed transit time and blood HDL (high density lipoprotein) (without yeast). Supplementation with S. cerevisiae increased DM digestibility but reduced ileal pH, ileal coliform population and abdominal fat content. 4. There was a significant interaction between S. cerevisiae and wet feeding, with S. cerevisiae supplementation inducing a significant increase in body weight and feed intake but a reduction of relative abdominal fat and ileal pH of broilers fed on wet diets. 5. It is concluded that wet feeding improved growth performance by increasing feed intake and that the addition of a culture of S. cerevisiae had a growth stimulating effect, as the inclusion of yeast in wet wheat-based broiler diets generated greater responses than yeast in dry-based diets.

Comparative feeding value of extruded and nonextruded wheat and corn distillers dried grains with solubles for broilers

The feeding value of extruded and nonextruded wheat and corn distillers dried grains with solubles (DDGS) for broilers was evaluated in 2 experiments. In experiment 1, male broilers (n=360) housed in battery cages were fed assay diets that included either 15 or 30% wheat or corn DDGS (extruded or not) in relation to a basal diet from d 21 to 28. Birds were killed on d 28 and ileal digesta was collected to establish the apparent ileal digestibility (AID) coefficients of energy and nutrients for test ingredients using the difference method based on 5 cages of 8 birds per diet. In experiment 2, a 42-d study compared the growth performance of broilers fed phase diets including 0, 5, or 10% wheat or corn DDGS, based on 4 pens of 55 birds per diet×sex combination. Diets within phase were formulated to have a similar content of AME, CP, and digestible lysine. Breast meat weight and yield were determined on d 37 by sampling 5 birds per pen. In experiment 1, at 15% inclusion, AID coefficients of most amino acids were higher for corn DDGS than for wheat DDGS (P<0.05). At 30% inclusion, however, there were fewer differences in AID between corn and wheat DDGS. Twin-screw extrusion increased the AID of AA in both corn and wheat DDGS by 10 to 34% (P<0.05). In experiment 2, there was no adverse effect of including corn or wheat DDGS at up to 10% of the diet on pen average daily weight gain, feed disappearance, feed efficiency, breast meat weight, or yield. In conclusion, extrusion increased the feeding value of DDGS. The AID coefficients for amino acids were similar between corn and wheat DDGS. We also confirmed that either corn or wheat DDGS can be included at up to 10% of wheat-based broiler diets without affecting growth performance or breast meat yield.

Impact of Exogenous Enzymes in Sorghum- or Wheat-Based Broiler Diets on Nutrient Utilization and Growth Performance

The impact of two enzyme preparations in either sorghumor wheat-based broiler diets on nutrient utilization and growth performance was determined. One preparation (Enzyme A) combined protease, xylanase and s-glucanase activities and the second (Enzyme P) contained xylanase activity. Sorghumor wheat-based starter (1-14 days), grower (15-28) and finisher (29-42) diets without or with either Enzyme A or Enzyme P were offered to broilers from 1-42 days post-hatch. Each of the six dietary treatments was offered to six replicates of six birds per cage. Total excreta collections were completed in the grower and finisher phases to determine the effects of dietary treatments on nutrient utilization as assessed by Apparent Metabolizable Energy (AME), Nitrogen (N) retention and N-corrected AME (AMEn). Both preparations contained similar levels of xylanase activity and enhanced nutrient utilization in wheat-based broiler diets with more pronounced responses in the finisher phase. In this phase, Enzyme A significantly increased AME by 0.98 MJ, N retention by 4.80 percentage units and AMEn by 0.95 MJ/kg. Similarly, Enzyme P increased AME by 1.21 MJ, N retention by 4.25 percentage units and AMEn by 1.24 MJ/kg. In contrast, enzyme inclusions in sorghum-based grower and finisher diets did not influence nutrient utilization and this is reflected in significant treatment interactions (p<0.001) for AME and AMEn in the finisher phase. In broilers offered wheatbased diets, both enzymes similarly improved growth performance; Enzyme A and Enzyme P significantly improved feed efficiency by 7.0% and 7.1%, respectively, from 1-42 days post-hatch. In sorghum-based diets, Enzyme P numerically depressed feed efficiency; whereas Enzyme A marginally enhanced feed efficiency and increased weight gain by 6.7%, which closely approached significance (p<0.06). Kafirin is the dominant protein fraction in sorghum and the possibility that the protease component in Enzyme A, subtilisin, has the capacity to degrade kafirin is considered.

Beneficial effects of xylanase and/or phytase inclusions on ileal amino acid digestibility, energy utilisation, mineral retention and growth performance in wheat-based broiler diets

The effects of individual and combined inclusions of xylanase and phytase in broiler diets based on a characterised wheat were evaluated. The positive control diet was formulated to be adequate for phosphorus (P) with 3.8 g kg −1 nonphytate P and the low-P, negative control diet contained 2.6 g kg −1 nonphytate P. The negative control diet was supplemented with xylanase (2000 XU kg −1), or phytase (500 FTU kg −1), or xylanase plus phytase (2000 XU kg −1 and 500 FTU kg −1). Treatment effects on ileal digestibility of amino acids, energy and nitrogen utilisation, ileal digestibility and total tract retention of minerals, toe ash content and the growth performance were determined. In combination, xylanase plus phytase increased mean apparent ileal digestibility (AID) coefficients of 17 amino acids by 8.6%, which exceeded the increases of 4.8% and 5.5% generated by xylanase and phytase, respectively. Increases in AID were significant ( P<0.05) for the majority of amino acids in response to enzyme inclusions with indications of synergistic responses for five amino acids. Xylanase plus phytase increased ( P<0.05) nitrogen-corrected AME by 0.63 MJ kg −1, ileal energy digestibility by 0.89 MJ kg −1 and energy AID coefficient by 6.7% relative to the negative control diet. The enzyme combination increased ( P<0.05) coefficients of ileal nitrogen digestibility by 9.1% and 8.0% relative to positive and negative control diets, respectively. Phytase increased ( P<0.05) ileal calcium digestibility by 32.2% and ileal P digestibility by 28.0% relative to the negative control. Also, phytase increased ( P<0.05) the AID coefficient of sodium to −0.038 from −0.516 in the negative control diet and the combination increased the same coefficient to 0.043. P reduction in the control diet lowered ( P<0.05) bone mineralisation, but toe ash contents were restored by phytase and xylanase plus phytase. P status of the control diets had no effect ( P>0.05) on the efficiency of feed conversion, but xylanase (6.2%), phytase (2.5%) and xylanase plus phytase (3.9%) enhanced ( P<0.05) feed efficiency relative to the negative control. The low-P diet depressed ( P<0.05) weight gain and feed intake but phytase and xylanase plus phytase restored both weight gain and feed intake. Overall, the present data indicate that the simultaneous inclusion of xylanase plus phytase in wheat-based broiler diets was beneficial in terms of nutrient utilisation and growth performance.

Use of an antibiotic growth promoter and two herbal natural feed additives with and without exogenous enzymes in wheat based broiler diets

A study was conducted to compare the effects of an antibiotic growth promoter (flavomycin) and two herbal natural feed additives (garlic and thyme) with and without a xylanase-based enzyme complex in wheat-based diets on growth performance, carcass parameters, total plasma cholesterol concentration, intestinal traits and the dry matter content of excreta of broiler chickens. A total of 112 day-old male broiler chicks was randomly assigned to eight groups containing 14 chicks each and raised from 1 to 42 days of age. The control group received the wheat-soyabean meal basal diet. In the treatment groups the basal diet was supplemented with one of the following: an antibiotic, thyme, garlic, an enzyme, the antibiotic plus the enzyme, thyme plus the enzyme or garlic plus the enzyme. During the 42-d growth period there were no significant differences in body weight gain, feed intake and feed conversion ratio of the broilers between dietary treatments. Feeding the diet supplemented with the antibiotic plus the enzyme significantly increased hot and cold carcass yields compared to the diets supplemented with thyme, garlic, enzyme and garlic plus enzyme. Total plasma cholesterol concentration, the dry matter content of excreta and the relative weights of the heart, pancreas, liver, gizzard and spleen were not significantly influenced by dietary treatments. The relative weight of the small intestines of the broilers receiving the diets supplemented with the antibiotic, antibiotic plus enzyme, thyme plus enzyme and garlic plus enzyme were significantly less than those of the broilers fed the basal diet and the diets supplemented with thyme, garlic and enzyme. The basal diet and garlic supplemented diet significantly increased the length of the small intestine compared to the other dietary treatments. Broilers receiving the diet supplemented with antibiotic had significantly lower total aerobic bacterial counts in the small intestines compared to those on the other dietary treatments. The combined supplementation of the antibiotic and enzyme resulted in a significantly lower E. coli concentration in the small intestines compared to the basal diet and the other dietary treatments.

Phytase Supplementation of Wheat-Based Broiler Diets Reduces Dependence on Meat-and-Bone Meal

It is permissible to include meat-and-bone meal (MBM) in broiler diets in many countries outside the European Union, including Australia, where MBM is usually advantaged by being a relatively inexpensive source of phosphorus and protein. However, some producers may prefer to reduce their dependence on MBM as this feed ingredient has several disadvantages and may be a barrier to exports of chicken-meat. Therefore, the purpose of this experiment was to investigate the extent to which phytase supplementation can reduce MBM inclusion levels in wheat-based broiler diets. Standard and modified starter, grower and finisher diets were formulated so that modified diets contained lower MBM inclusions and reduced nutrient specifications. The standard and modified diets, the latter supplemented with 0, 500 or 750FTU/kg phytase (Phyzyme® XP), were offered to a total of 840 broilers in 24 floor pens from 1-42 days of age and the effects of dietary treatments on growth performance were determined. For the grower phase (15-28 days), five broilers from each floor pen were transferred to cages to permit total excreta collection to determine apparent metabolisable energy (AME) and nitrogen (N) retention. Acid insoluble ash was included in the caged birds’ diets and ileal digesta collected at 28 days to determine the effect of dietary treatments on apparent ileal digestibility (AID) of amino acids. Lowering nutrient specifications reduced growth performance and increased mortality rates over 42 days but this decline in performance was overcome by the addition of 750FTU/kg phytase to modified diets. Feed ingredient costs per unit of live weight gain were also reduced by phytase addition. Reducing dietary levels of MBM increased amino acid digestibilities in the modified grower diet. Moreover, phytase supplementation of modified diets linearly increased AID coefficients of alanine, aspartic acid, glycine, isoleucine, leucine, serine, threonine and tyrosine to a significant extent. Also, phytase (750FTU/kg) supplementation of the modified diet significantly increased AME by 0.27MJ/kg on a dry matter (DM) basis. Overall consumption of MBM was reduced from 233g to 14g per bird from 1-42 days of age following dietary modifications. It is noteworthy that reduced inclusions of MBM, coupled with phytase supplementation, enhanced ileal digestibility of total amino acids by 5.3% (0.834 versus 0.792). This study demonstrates that it is feasible to reduce MBM contents and nutrient specifications in wheat-based broiler diets in association with phytase supplementation without the addition of inorganic phosphorus sources.

Implications of b-glucanase and pentosanase enzymes in low-energy low-protein barley and wheat based broiler diets

This study was conducted to test the effects of a commercial enzyme (with beta-glucanase and pentosanase activities) supplemented into low-protein low-energy barley and wheat based broiler diets on broiler performance. The enzyme was added at 500 g/ton into broiler grower and finisher diets consisting of mainly wheat at 76%, 85% or barley 67%, 75%, respectively. Four dietary treatments were wheat, wheat + enzyme, barley, barley + enzyme. Each treatment had six replications. This experiment was planned according to a completely randomised design by placing ten 14-day-old mixed male and female chicks into one experimental cage unit with wire floor. Cobb broiler chicks were used in this study. Experimental grower and finisher diets were fed to chicks between 14&amp;ndash;28 and 28&amp;ndash;42 days of age, respectively. One-day-old chicks were fed a standard starter diet (23% protein; 12.77 MJ ME/kg) according to NRC (1994) recommendations. Grower diet and finisher diets were formulated to be 10% lower than NRC (1994) with respect to the protein and metabolisable energy content. Body weight, average weight gain (14&amp;ndash;42 days period), feed intake and feed efficiency ratio were measured at 42 days of age. The results of this study demonstrated that the enzyme with beta-glucanase and pentosanase activities supplemented into barley-based broiler diets significantly (P &amp;lt; 0.05) improved body weight by 10%, from 1 779 to 1 958 g, and gain by 12%, from 1 485 to 1 657&amp;nbsp;g, respectively. However, when the same enzyme was supplemented into wheat-based diets, no improvement (P &amp;lt; 0.05) was obtained in body weight and feed efficiency, being 1 723 and 1 677 g and 1 973 and 1 957, respectively for wheat and wheat + enzyme groups. The feed efficiency ratio was also significantly (P &amp;lt; 0.05) improved in barley-based diet from 1.898 to 1.845 by enzyme addition during the 14&amp;ndash;42 days experimental period. &amp;nbsp;

Effects of oat hulls and wood shavings on digestion in broilers and layers fed diets based on whole or ground wheat

1. An experiment was conducted to study the effects of inclusion of oat hulls in diets based on whole or ground wheat for broilers. Effects of wood shavings on layers were investigated in a further experiment. 2. Inclusion of oat hulls in wheat-based broiler diets did not affect weight gain. Feed conversion efficiency (FCE), corrected for insoluble fibre contents, was improved by oat hull inclusion. 3. Gizzard size increased with inclusion of oat hulls, whole wheat, wood shavings and grit. 4. Starch digestibility was significantly increased by inclusion of oat hulls for broilers, and by wood shavings for layers. 5. Wood shavings and whole wheat did not affect bile acid concentration of gizzard contents. However, the total amount of bile acids in gizzard increased with access to wood shavings due to an increase in the weight of gizzard contents, indicating an increased gastroduodenal reflux. 6. Fibre concentration was considerably higher in the gizzard contents than in the feed. 7. Duodenal particle size decreased with access to grit. No effect of hulls or whole wheat inclusion was found, indicating that all particles are ground to a certain critical size before leaving the gizzard.

Effects of Nutrient Specifications and Xylanase Plus Phytase Supplementation of Wheat-based Diets on Growth Performance and Carcass Traits of Broiler Chicks

The simultaneous addition of xylanase (5,600 EXU/kg) and phytase (500 FTU/kg) feed enzymes to wheat-based broiler diets was investigated. Starter, grower and finisher diets, with three tiers of nutrient specifications, were fed to 1,440 broiler chicks kept on deep litter from 1-42 days post-hatch, without and with xylanase plus phytase, to determine the effects of diet type and enzyme supplementation on growth performance. The nutrient specifications of type A diets were standard; energy density and protein/amino acid levels were reduced on a least-cost basis to formulate type B diets and further reduced to type C diets. Phosphorus (P) and calcium (Ca) levels were adjusted in supplemented diets. From 1-42 days post-hatch, diet type significantly influenced growth performance. Birds on type C diets had lower growth rates (2,429 vs. 2,631 g/bird; p<0.001), higher feed intakes (4,753 vs. 4,534 g/bird; p<0.005) and less efficient feed conversion (1.96 vs. 1.72; p<0.001) than birds offered type A diets. Enzyme supplementation increased growth rates by 3.2% (2,580 vs. 2,501 g/bird; p<0.005) and improved feed efficiency by 2.7% (1.80 vs. 1.85; p<0.05) over the entire feeding period. There were no interactions between diet type and enzyme supplementation. At 21 days, 5 out of 30 birds per pen were transferred to cages to ascertain treatment effect on apparent metabolisable energy (AME) and nitrogen (N) retention. Xylanase plus phytase enhanced AME (13.48 to 13.91 MJ/kg DM; p<0.001) and N retention (56.3 to 59.7%; p<0.005). Carcass and breast weights of the caged birds were determined following commercial processing. Diet type significantly influenced breast weight, carcass weight and yield. Birds offered Type A diets, in comparison to Type C diets, supported heavier breast (467 vs. 424 g; p<0.001) and carcass weights (1,868 vs. 1,699 g; p<0.001) with superior carcass yields (71.8 vs. 70.6%; p<0.005). Enzyme addition increased carcass weight by 3.9% (1,752 vs. 1,821 g; p<0.005) and breast weight by 5.8% (431 vs. 456 g; p<0.01) without influencing yields. Feed ingredient costs per kg live weight gain and per kg carcass weight indicated that enzyme addition was economically feasible, where supplementation of Type A diets generated the most effective results. Importantly, soluble and total non-starch polysaccharide and phytate contents of the wheat used were typical by local standards. This study confirms the potential of supplementing wheat-based broiler diets with xylanase plus phytase but further investigations are required to define the most appropriate inclusion rates and dietary nutrient specifications in this context. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 10 : 1501-1509)

Influence of Phytase and Xylanase Supplementation on Growth Performance and Nutrient Utilisation of Broilers Offered Wheat-based Diets

Individual and combined supplementation of phosphorus-adequate, wheat-based broiler diets with exogenous phytase and xylanase was evaluated in three experiments. The effects of the enzyme combination in lysine-deficient diets containing wheat and sorghum were more pronounced than those of the individual feed enzymes. The inclusion of phytase plus xylanase improved (p<0.05) weight gains (7.3%) and feed efficiency (7.0%) of broilers (7-28 days post-hatch) and apparent metabolisable energy (AME) by 0.76 MJ/kg DM. Phytase plus xylanase increased (p<0.05) the overall, apparent ileal digestibility of amino acids by 4.5% (0.781 to 0.816); this was greater than the responses to either phytase (3.6%; 0.781 to 0.809) or xylanase (0.7%; 0.781 to 0.784). Absolute increases in amino acid digestibility with the combination exceeded the sum of the individual increases generated by phytase and xylanase for alanine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, phenylalanine, threonine, tyrosine and valine. These synergistic responses may have resulted from phytase and xylanase having complementary modes of action for enhancing amino acid digestibilities and/or facilitating substrate access. The two remaining experiments were almost identical except wheat used in Experiment 2 had a higher phytate concentration and a lower estimated AME content than wheat used in Experiment 3. Individually, phytase and xylanase were generally more effective in Experiment 2, which probably reflects the higher dietary substrate levels present. Phytase plus xylanase increased (p<0.05) gains (15.4%) and feed efficiency (7.0%) of broiler chicks from 4-24 days post-hatch in Experiment 2; whereas, in Experiment 3, the combination increased (p<0.05) growth to a lesser extent (5.6%) and had no effect on feed efficiency. This difference in performance responses appeared to be 'protein driven' as the combination increased (p<0.05) nitrogen retention in Experiment 2 but not in Experiment 3; whereas phytase plus xylanase significantly increased AME in both experiments. In Experiments 2 and 3 the combined inclusion levels of phytase and xylanase were lower that the individual additions, which demonstrates the benefits of simultaneously including phytase and xylanase in wheat-based poultry diets.