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A total of 960 male Cobb 500 broilers were used in a growth performance study to explore the effect of coccidial vaccination and/or coccidial challenge on blood biochemistry and veterinary postmortem metrics. Day-old chicks were randomly divided into one of the 4 experimental treatments. Treatments were arranged in a 2 × 2 factorial arrangement, with the factors being without or with vaccination (administered on day 1) or coccidial challenge (oral gavage on day 7). Growth performance was monitored on a weekly basis. Blood sample collection, as well as full veterinary necropsies, were carried out on days 6, 8, 13, 20, 27, and 34. Birds that did not receive the vaccination but were challenged with coccidiosis had higher feed conversion ratio, lower body weights, and higher mortality than the other experimental groups, and this effect was particularly evident from day 13 to day 20. Birds challenged with coccidiosis had lower plasma sodium and total carotenoid concentrations and higher potassium and globulin concentrations than nonchallenged birds. Significant interactions between age and experimental treatment for these blood parameters were observed, particularly on day 13. The necropsy results confirmed the effectiveness of the challenge and vaccination treatments, wherein birds that were challenged had higher coccidiosis scores on day 13 and day 27 than birds that were not challenged. These results demonstrate the potential for plasma sodium, potassium, total protein, total carbon dioxide, globulin, and carotenoid analysis for early diagnosis of coccidiosis in growing broiler chickens. Further work is necessary to establish whether the changes in blood biochemistry observed in the present study are transferable to alternative flocks of chicken and whether early diagnosis and intervention may mitigate performance losses associated with this disease.

The primary objective of the current study was to evaluate the impact of trypsin inhibitor (TI) and exogenous protease supplementation on endogenous loss of amino acids (AA) in broiler chickens. A total of 384 Cobb-500 broiler chicks were allocated to 4 nitrogen-free diets, each with 8 replicate cages and 12 birds per replicate. The diets were arranged as a 2 × 2 factorial with factors being dietary TI (0 or 8,000 TIU/g) and exogenous protease (0 or 15,000 PROT/kg). Desired dietary TI concentration was achieved by addition of commercially available, purified soybean TI. There was no effect of TI or exogenous protease or their interaction on growth performance of birds. However, the endogenous loss of nitrogen (N) and all AA increased (P < 0.05) due to dietary TI concentration except for Cys. The increase in endogenous AA due to TI ranged from 17% for Thr to 52.2% for Trp. Exogenous protease had no effect on endogenous loss of N and all AA. There was no effect of TI or exogenous protease or their interaction on the AID of P, however AID of Ca, Fe, Mg, Mn, and Cu was reduced (P < 0.05) due to dietary TI. The AID of Cu (P < 0.01) and K (P < 0.05) improved with exogenous protease supplementation. Significant interactions (P < 0.05) between exogenous protease and TI existed for Zn, Mg, Cu, and Na. The concentration (g/kg DM intake) of crude mucin and sialic acid increased (P < 0.05) with increased dietary TI. Decreased trypsin (P < 0.001) and increased chymotrypsin (P < 0.001) activity in the pancreas were observed as a result of exogenous protease supplementation. In conclusion, the current study showed that TI increases the endogenous loss of AA and reduced the digestibility of minerals in broiler chickens. Furthermore, exogenous protease did not affect endogenous AA flow, irrespective of added purified dietary TI.

Phytase is of importance to the poultry industry because of its ability to hydrolyze phytate and release phosphorus (P) for use by poultry. However, the effect of age on phytase efficacy is not fully understood. A total of 864 day-old broiler chicks were used to investigate the effect of age and feeding length on phytase efficacy using growth performance, mineral utilization, and tibia ash as response criteria of evaluation. The experiment was arranged as a 3 × 2 × 2 factorial in a randomized complete block design with 3 diets including; a positive control (PC; 0.4% non-phytate P (nPP)), a negative control (NC; 0.2% nPP) and a NC diet supplemented with phytase at 2,000 FYT/kg; 2 ages (i.e., days 14 and 22); and 2 feeding lengths (i.e., 2 and 5 D) with 8 replicates each. Birds fed the NC had decreased (P

A study was conducted to evaluate the effects of a supplemental α-amylase on energy and nutrient utilization of broiler chickens fed diets with variable amounts of corn. A total of 480 slow feathering Cobb × Cobb 500 male broilers were randomly distributed into 10 treatments with 8 replicates of 6 birds each. Birds were fed a common starter to 14 D post-hatch. The experimental diets were provided subsequently until 25 D, which were a conventional corn-soy basal diet (CS) and a corn-soy diet displaced with 40% of corn (CN). These were fed as-is or supplemented with 40, 80, 120, or 160 kilo-Novo α-amylase units (KNU)/kg. Dietary treatments were distributed factorially as a 2 × 5 arrangement (diet type vs. amylase). Samples of feed, excreta, and ileal digesta were analyzed for determination of ileal digestible energy (IDE), ME, total tract retention, and digestibility of dry matter, protein, and fat. No interactions between diet type and amylase were observed. The CN diet had lower (P < 0.05) energy utilization and nutrient digestibility when compared to the CS diet. AMEn and IDE increased (P < 0.05) by 110 and 207 kcal/kg, respectively, when CS and CN diets were supplemented with 80 KNU/kg. The amylase added to the CS diet led to quadratic increases (P < 0.05) on growth performance, IDE, AME, and AMEn, as well as in dry matter, protein, and fat digestibility. Energy utilization and crude protein digestibility were linearly increased (P < 0.05) when amylase was added to the CN diet or the extrapolated 100% of corn. In conclusion, energy utilization, digestibility of crude protein, fat, and dry matter increased with amylase supplementation in corn-soy-based diets. When amylase was tested in a complete diet having 53.6% corn, 100 and 105 KNU/kg maximized AMEn and IDE, respectively; however, the maximum energy response in the CN diet or 100% of corn was not achieved until 160 KNU/kg, suggesting an association between amylase dose optimization and dietary starch concentration.

SUMMARY Increasing global population and disposable income is resulting in a dramatic rise in demand for animal-sourced food products. To meet this demand, the animal protein industry is constantly evolving to enhance efficiency and sustainability. Nutritionally, a major contributing technology to this objective is the exogenous feed enzymes. These enzymes can be included in the diet of livestock to improve digestibility, reduce nitrogen and phosphorus pollution, reduce diet cost, and improve uniformity of animal growth. However, the number of feed enzyme products on the market today is considerable and there is a lack of clarity as to how these divergent enzymes may interact in a diet. The study reported herein noted that the addition of a novel exogenous protease to a broiler chicken diet improved weight gain (+7.3%) and reduced feed conversion ratio (−4%) even though the diet already contained 2 other feed enzymes (phytase and xylanase). The results reported herein confirm the usefulness of exogenous protease and the value of such a part of a wider enzyme admixture to improve the sustainability of the broiler chicken industry.

Interaction between the host and the enteric microbiome is highly complex. Microbial involvement in certain pathologies is moderately well established, but the contribution of the microbiome to animal welfare, behavior, sustainability, immune development, nutritional status, physiology, and maturation is less clear. A valuable experimental model to enable scientists to explore the role of the microbiome in various domains is to compare various phenotypes of a conventionally reared (CV) cohort with those in a germ-free (GF) state. A GF animal is one that is devoid of any detectable microbial life including bacteria, viruses, protozoa and parasites. The GF state is different from gnotobiotic animals where the microbiome is fully described, or 'specific pathogen free' (SPF) animals where a moderately normal microbiome is present but devoid of pathogenic microorganisms. Pioneering GF research in poultry in the late 1940s and 1950s has its origin in a need understand the mode of action of antibiotics. Early researchers quickly established that GF chicks responded differently to antibiotics than CV counterparts. The GF experimental model has since been exploited in many divergent fields including pathology, immunology, metabolism, anatomy, physiology, and others. The absence of a microbiome presents the host with a range of advantages and disadvantages. For example, GF chicks often grow more quickly and have lower feed conversion ratio (FCR) than their CV counterparts but may be less resilient to external stress and have a compromised immunological maturation rate. This review will summarize the literature on GF animal research with a special emphasis on poultry. The objective of the review is to establish a frame of reference to understand the extent of the role of the microbiome in animal health, welfare, nutrition, and growth, to provide opportunities for targeted modulation of the microbiome to achieve desired phenotypic responses whilst simultaneously minimizing unintended collateral effects.

Cassava (Manihot esculenta), a crop grown in the tropics, is increasingly becoming a vital feed resource for human beings and livestock. Traditionally, cassava has been used primarily as a source of food for humans. However, it is becoming an increasingly important ingredient in livestock feed. The use of cassava leaves and roots in poultry diets is limited because of nutrient imbalances and toxins (hydrogen cyanide (HCN)) found in them. High HCN is reduced to innocuous levels by processing the ingredient using a simple sun drying method. Plant fibre content can be reduced and made available for use by poultry through the use of exogenous enzymes. More recent innovative interventions in biotechnology have brought about various exogenous enzymes that can help improve the digestibility of fibrous diets. These include, among others, carbohydrases, proteases and phytases. The extent to which the animals utilise nutrients is influenced by the type of enzyme and the physicochemical properties of the feed ingredient. This review aims to collate information on the current state of knowledge on the use of exogenous microbial enzymes in diets containing cassava and how the enzymes that target carbohydrates might be useful in making nutrient available for poultry.

The objective of this study was to measure apparent total tract digestibility (ATTD) of Ca and P as well as reproductive performance in late-gestation and lactating sows supplemented with a novel phytase and to compare the response to phytase supplementation between late-gestation and lactating sows. Forty-five late-gestation sows and 45 lactating sows were used in experiments 1 and 2, respectively, in a completely randomized design. The sows were provided with a control diet or the control diet supplemented with 187.5 or 375 FYT phytase/kg feed for 10 days. The diets were prepared according to the formulas in use for production but without any inorganic P supplement. Titanium dioxide was included at 3 g/kg feed as an indigestible marker. Each dietary treatment was replicated with 15 sows individually-housed in farrowing stalls. The sows were allowed to adapt to the experimental diets for 5 days before a 5-d fecal collection by grab sampling, and the performance of the sows and their litters were measured until weaning. The results showed that the ATTD of Ca increased linearly (P < 0.001) while the ATTD of P increased both linearly and quadratically (P < 0.01) with increasing supplementation of phytase in both late-gestation and lactating sows. There was no significant effect of phytase on the ATTD of dry matter, crude protein, and gross energy, and the performance of the sows and their progenies. The phytase added at 187.5 and 375 FYT/kg feed released 0.07% and 0.10% digested P, respectively, in late-gestation sows, which compared with 0.09% and 0.12% digested P in lactating sows. In conclusion, a novel phytase at 187.5 to 375 FYT/kg feed could release 0.07 to 0.12% digestible P for sows. It appeared that using the P digestibility values of feed ingredients listed by NRC (2012) to formulate a diet for sows might overestimate dietary P supply and a greater response to phytase supplementation could be expected in lactating sows than in late-gestation sows.

Modern feed quality sorghum grain has been bred to reduce anti-nutrients, most conspicuously condensed tannins, but its inclusion in the diets of monogastric animals can still result in variable performance that is only partially understood. Sorghum grain contains several negative intrinsic factors, including non-tannin phenolics and polyphenols, phytate, and kafirin protein, which may be responsible for these muted feed performances. To better understand the non-tannin phenolic and polyphenolic metabolites that may have negative effects on nutritional parameters, the chemical composition of sorghum grain polyphenol extracts from three commercial varieties (MR-Buster, Cracka, and Liberty) was determined through the use of an under-studied, alternative analytical approach involving Fourier-transform infrared (FT-IR) spectroscopy and direct ionization mass spectrometry. Supervised analyses and interrogation of the data contributing to variation resulted in the identification of a variety of metabolites, including established polyphenols, lignin-like anti-nutrients, and complex sugars, as well as high levels of fatty acids which could contribute to nutritional variation and underperformance in monogastrics. FT-IR and mass spectrometry could both discriminate among the different sorghum varieties indicating that FT-IR, rather than more sophisticated chromatographic and mass spectrometric methods, could be incorporated into quality control applications.

A total of 640 broilers were used to determine the effects of strain, sex, and age on hematology and blood chemistry using rapid detection devices. Day old chicks from two genetic lines of common fast-growing and high-yield broiler strains were sexed and allocated to 40 pens (16 birds per pen) containing either male or female and Ross or Cobb strains (n = 10). Venous blood was analyzed weekly using 2 broilers from each pen (n = 20) using the i-STAT® Alinity Handheld Clinical Analyzer, Zoetis Vetscan VS2, and iCheck™ Carotene devices at 14, 21, 28, 35, and 42 d, as well as growth performance. Post-mortem health tracking metrics were also recorded on 42 d. Broilers were deemed healthy based on posting data results and performed in accordance with industry standards with males presenting greater BW and reduced FCR than female broilers. Ross broilers displayed greater BW to 14 d with similar FCR compared with Cobb birds. Day of age had a highly significant impact on blood calcium, phosphorus, potassium, sodium, chloride, carotene, aspartate aminotransferase, creatine kinase, bile acids, uric acid, total protein, albumin, globulin, total carbon dioxide, hematocrit, and malondialdehyde. Male broilers had reduced blood sodium, chloride, carotene, uric acid, albumin, and increased total protein, glucose, and total carbon dioxide. Ross broilers had greater blood potassium, and sodium, as well as reduced uric acid, total protein, globulin, and malondialdehyde, compared with Cobb birds. These results demonstrated the effectiveness of point-of-care devices in measuring blood chemistry and hematology in modern broilers. These data can be utilized to determine normal healthy blood ranges in these types of broilers when accounting for strain, sex, and age., Broiler, Biomarkers, Blood physiology, Rapid point-of-care detection, Animal breeding, Animal product, Biochemistry, Animal physiology, Veterinary science.

Growth performance, nutrient digestibility, intestinal health, and endogenous enzyme secretion responses to dietary α-amylase supplementation during 4 growth phases of broiler chickens fed corn–soybean meal–based diets were evaluated in the present study. A total of 1,136 male broiler chicks were assigned at day 0 after hatching to 8 treatments in a 2 × 4 factorial arrangement. There were 2 dietary levels of α-amylase supplementation of 0 or 80 kilo-Novo alpha amylase units per kg diet and 4 posthatching growth phases of day 0 to 11, day 11 to 21, day 21 to 42, or day 42 to 56 in a randomized complete block design. Each treatment comprised 8 replicate pens, with either 25 (day 0–11), 20 (day 11–21), 16 (day 21–42), or 10 (day 42–56) birds per pen. Body weight gain and feed efficiency of birds improved (P

Dietary starch is the major energy source for broiler chickens; therefore, relevant information on its intestinal utilization is important. The present study was designed to evaluate intestinal starch and energy digestibility of broiler chickens fed diets supplemented with α-amylase. A total of 240 day-0 male broiler chicks were randomly assigned to 3 nutritionally adequate corn-soybean-based experimental diets comprising 3 levels of α-amylase supplementation (0, 80, or 160 KNU/kg diet). Each treatment comprised 8 replicate cages of 10 birds each. At day 21 after hatching, digesta was collected from 4 intestinal sites: the anterior jejunum (AJ), posterior jejunum (PJ), anterior ileum (AI), and posterior ileum. Increasing α-amylase supplementation linearly improved (P < 0.01) overall BW gain and feed efficiency of the birds. There were linear and quadratic (P < 0.01) responses of increasing α-amylase supplementation on starch and energy digestibility at the PJ and AI. The total tract digestibility of starch increased (P < 0.05) with increasing α-amylase supplementation. Starch disappearance and digestible energy (kcal/kg) linearly increased (P < 0.01) with digesta flow from the AJ to PJ as dietary α-amylase supplementation increased. There were linear (P < 0.01) and quadratic (P < 0.05) effects of increasing α-amylase supplementation on the villus height in the jejunum. The viscosity of the jejunal digesta decreased (P < 0.05) with increasing dietary α-amylase supplementation. The results from this study showed the efficacy of exogenous amylase in improving growth performance and starch and energy digestibility in broiler chickens. Furthermore, the digestibility of starch and energy and the impact of the exogenous amylase were higher at the PJ than other intestinal sites.

Effective functionality of the gastrointestinal tract (GIT) and its health, are important factors in determining animal performance. Several, complex mechanisms are involved in the regulation of GIT functionality and health, therefore it is crucial to deepen our knowledge of these interactions so that strategies for the modulation of GIT functionality and health, in context of improved animal performance, can be developed. The concept of “gut health” has started to attract significant interest within the animal science community, however a clear definition of gastrointestinal health and functionality and how it can be measured is lacking. Therefore, this review will present a new definition of gastrointestinal functionality and will address how optimal gastrointestinal functionality can promote animal performances and welfare. The key components of gastrointestinal functionality reviewed in this article are: diet, effective structure and function of the gastrointestinal barrier, host interaction with the gastrointestinal microbiota, effective digestion and absorption of feed and effective immune status. While the relationships between these areas is extremely complex, a multidisciplinary approach is needed to develop nutritional strategies that would allow farm animals to become more resilient to the environmental and physiological challenges that they will have to endure during their productive career. As the demand of animal products from the rapidly growing world human population is ever-growing, the aim of this review is to present animal and veterinary scientists and nutritionists, a new definition of gastrointestinal functionality that can be used to establish a multidisciplinary approach to increase animal health, welfare and performance.

Data on the effect of microbial phytase on apparent ileal amino acid digestibility coefficients in pigs were transcribed from a total of 28 peer-reviewed papers in order to determine response patterns and overall effects. Transcribing the digestibility responses from the various papers resulted in a database with 925 observations from diets that were principally based on corn, soybean meal, canola meal and various co-products such as ricebran, wheatbran and distillers dried grains and solubles (DDGS). The majority of experiments utilized grower pigs of approximately 30 kg live-weight fitted with ileal cannulas but pigs from 6 to 71 kg in weight were represented as well as studies using post-mortem digesta collection techniques. Most papers were published between 2005 and 2016 but several were published prior to these dates. Phytase doses represented ranged from 250 FYT/kg to 20,000 FYT/kg feed though most observations ranged between 500 and 1000 FYT/kg. The overall effect of microbial phytase inclusion on apparent ileal amino acid digestibility coefficients was +2.8% and this ranged from +0.9% for Met to +4.1% for Pro. Above average responses were noted for Pro > Thr > Gly > Trp > Glu > Ala > Asp and Phe with particularly modest responses for Met, Arg and Cys. Phytase effects on apparent ileal amino acid digestibility coefficients were greater in diets with lower inherent amino acid digestibility. Increasing phytase dose from 250 to 2000 FYT/kg had no significant influence on phytase effect on amino acid digestibility although extending this dose range to 20,000 FYT/kg resulted in a moderate increase in mean response. Pig weight at time of digesta collection had no significant effect on overall phytase efficacy. There was a significant but weak correlation between ileal phosphorus and amino acid digestibility responses to phytase. It may be concluded from the meta-analysis presented herein that phytase can significantly increase apparent ileal amino acid digestibility in pigs at various weights (at least from 6 to 70 kg). The pattern of response by amino acid is different from broilers and therefore a common amino acid matrix for both chickens and pigs is inappropriate. Furthermore, it may be that phytate, while remaining a poorly available source of P (and a potential source of myo-inositol), may not represent as potent an antinutrient (on the protein/amino acid axis) in swine as it does in broilers. Thus, the beneficial effects of phytase on amino acid digestibility in swine may originate more from increased dietary protein digestibility and less from meaningful changes in endogenous amino acid flow, an observation that has implications for the additivity of amino acid matrix values of different enzymes in both species. The present review suggests that different phytases with equivalent effects on phosphorus digestibility should have equivalent amino acid release values assigned and that species-dependent values are not only justified but of critical importance to optimal use of phytase in animal production.

A study was conducted to evaluate the effects of dietary α-amylase and β-xylanase, in single or combined supplementation, on growth performance of broiler chickens fed maize-soy diets. A total of 1800 slow feathering, Cobb × Cobb 500 male broilers were randomly distributed to 8 treatments with 9 replicates of 25 birds each. Broilers were fed starter and finisher diets respectively from 1 to 21 and 22 to 40 d Broilers were fed starter and finisher diets respectively from 1 to 21 and 22 to 40 d. A negative control (NC) diet was formulated to contain 12.35 MJ/kg and 12.85 MJ/kg in the starter and finisher phases, respectively. A further four control diets were formulated with orthogonal energy density increases in increments of 0.21 MJ/kg to a maximum of 13.17 MJ/kg (starter) and 13.67 MJ/kg (finisher). All control diets were formulated to be equivalent in amino acids and minerals. The NC diet was supplemented with α-amylase (80 kilo-Novo α-amylase units/kg), β-xylanase (100 fungal β-xylanase units/kg), or both enzymes combined at the same supplementation levels. Increasing AMEn resulted in a linear increase (P

A total of 24 independent peer-reviewed papers on the effect of phytase on the coefficient of apparent ileal amino acid digestibility in broilers were used in a meta-analysis to explore response patterns. Transcription of the digestibility responses from all papers resulted in a database with 745 observations from diets based on various cereals (mainly corn), protein meals (mainly soybean meal) and by-products (ricebran, wheatbran etc). Most of the papers were published between 1996 and 2006 though several were published more recently (up to and including 2015) and included doses of phytase from 500 to 2000 FYT/kg. The mean coefficient of apparent ileal amino acid digestibility in the control was 0.80 and this was increased by the inclusion of phytase to 0.84 (+4.1%). The coefficients of apparent Lys, Met, Cys and Thr digestibility were increased by 3.4%, 1.3%, 7.2% and 6.0% respectively. A significant negative correlation was observed between the digestibility of the amino acids in the control diet and the magnitude of response to exogenous phytase, where phytase effect (on a relative and absolute basis) was lower in diets with a higher inherent amino acid digestibility. Elevation of phytase dose from 500 to 1000 FYT/kg resulted in an increase in amino acid digestibility coefficients from around 2% to around 4% but further increases to 2000 FYT/kg had no further positive effect. A significant relationship was noted between the proportion of dietary phytate destroyed by exogenous phytase and the effect of phytase on ileal amino acid digestibility coefficients where phytase effects ranged from 2 to 3% to 9–10% as phytate destruction increased from

Broiler live performance may be influenced by postharvest corn drying temperature, and results could depend on particle size after grinding. The supplementation with an exogenous amylase may improve performance parameters, but responses to enzymes are also affected by particle size. Two parallel experiments were conducted to evaluate the effects of hard-kernel corn dried at 2 temperatures (35°C and 120°C), ground at 2 particle sizes (coarse or fine), and 3 supplementation levels (0, 133, and 266 g ton-1) of an exogenous amylase on live performance, gastrointestinal organ development, energy utilization, and nutrient digestibility. Twelve dietary treatments resulting from a 2 × 2 × 3 factorial arrangement of drying temperature, particle size, and amylase supplementation were evaluated in both experiments. A total of 1,920 day-old male chicks were randomly allocated to 96 floor pens, while 480 chicks were distributed among 4 battery brooder units. Ileal and fecal samples were collected to determine energy utilization and nutrient digestibility using titanium dioxide as inert marker. At 42 D, organs were collected, and relative weight or length was determined. Data were analyzed using a three-way ANOVA in a randomized complete block design. Feeding fine corn-based diets showed improvements on live performance for both studies. At 40 D, supplementing 266 g ton-1 of amylase improved feed conversion ratio (P < 0.05) by 1 point compared to chickens that consumed nonsupplemented diets and feed with amylase at 133 g ton-1. Broilers fed coarse corn-based diets had heavier gizzard (P < 0.001) and liver (P < 0.05) than chickens that consumed fine corn-based diets. In addition, starch digestibility was improved by amylase (P < 0.05) at 133 g ton-1 and by feeding coarse corn-based diets (P = 0.06). For chicks raised in cages (16 D), AMEn was increased (P < 0.01) by amylase supplementation regardless of its inclusion level. In conclusion, drying temperature and particle size interactions influenced broiler live performance, gastrointestinal organ development, nutrient digestibility, and energy utilization, and these parameters were improved by supplementing amylase.

Starch is the main energy source in broiler diets. However, endogenous amylase secretion in young broilers is suboptimal to completely digest dietary starch, so exogenous α-amylase supplementation may help increase starch digestibility. The objective of this study was to assess the supplementation of increasing doses of an exogenous α-amylase (0, 40, 80, 120, and 160 kilo-novo α-amylase units (KNU)/kg) on corn and on a complete corn–soybean meal diet for 25-day-old broilers. Jejunal and ileal apparent digestibility coefficients of available starch, resistant starch, total starch, and DM, DM total tract retention, as well as dietary AME levels were evaluated. Interactions (P

The influence of calcium (Ca) source and particle size on true ileal digestibility coefficient (TIDC) of Ca and apparent total tract retention coefficient (ATTRC) of Ca in broilers was assessed. Four experimental diets containing limestone and oyster shell, each as fine ( 0.05) for the TIDC and ATTRC of Ca. Both TIDC and ATTRC of Ca were influenced (P

The statement ‘phytic acid is ubiquitously present in non-ruminant animal diets’ is often made in scientific manuscripts oriented toward phytase, mineral and amino acid nutrition, monogastric animal performance and skeletal development. However, it is increasingly the case that this statement is at best misleading and at worst entirely incorrect. Phytase bioefficacy is at an unprecedented high in the life cycle of this technology and product cost is at an all-time low, two factors which have contributed to a climb in inclusion concentration and an axiomatic decrease in dietary phytic acid concentration. Though complete dephytinisation of monogastric animal diets may be unrealistic due to the presence of variable concentrations of recalcitrant phytic acid in localized regions of cereals, oilseed meals and grain legumes, the vast majority of reactive phytic acid is rapidly degraded to innocuous lower esters in the proximal GI tract. Thus, the nutritional paradigm has shifted from formulating diets to accommodate the presence of phytase to formulating diets to accommodate the absence of phytic acid. These are not trivial distinctions but may have considerable implications for animal performance and the optimal balance of nutrients in the diet. It is the purpose of the present article to consider the breadth of effect of the ingestion of phytic acid and the likely consequence of an ostensibly dephytinized diet on nutrition and animal performance. The concept of ‘phytate-free nutrition’ is posited and nutritional strategies to maximise the likelihood of observing measurable benefits from the lack of this nutritional obstacle are discussed around three conceptual pillars: phosphorus, extra-phosphoric effects and myo-inositol.

Exogenous protease has formed part of several commercial enzyme admixtures for the past 15–20 years but has become available as a mono-component enzyme only in the last 5–10 years (Cowieson and Adeola, 2005; Fru-Nji et al., 2011). As part of an enzyme admixture (often also containing various carbohydrases and/or phytase) it is difficult to separate the contributions of the component parts and the efficacy of each has implicit rather than explicit value. However, the effectiveness of mono-component enzymes can be readily assessed under different production and nutritional circumstances and their complementarity with alternative enzymes is readily rendered transparent. The motivation for the use of exogenous protease in non-ruminant nutrition is typically the reduction of feed cost at constant animal performance. This objective is usually achieved via displacement of expensive protein/amino acid sources in the diet through the assignment of a nutrient matrix on the enzyme in least cost formulation. Recently attention has moved from this classical approach to protease application to so-called ‘extra-proteinaceous’ effects including environmental benefits, litter management, enteric resilience, uniformity and microbial stability. Whilst these ‘secondary’ effects may not be the principal motivator for the use of proteases in animal production they are increasingly visible and require explanation. Furthermore, these responses, if understood, allow positive translation to production metrics such as reduced FCR and improved weight gain. It is the purpose of this review to briefly summarise the current state of the art in mono-component exogenous protease use in non-ruminants and to suggest mechanisms whereby the ‘extra-proteinaceous’ effects may be explained. Finally, key diet/animal factors that may promote beneficial effects of exogenous protease on live performance will be discussed.

Phytases are important commercial enzymes that catalyze the dephosphorylation of myo-inositol hexakisphosphate (phytate) to its lower inositol phosphate (IP) esters, IP6 to IP1. Digestion of phytate by Citrobacter braakii 6-phytase deviates significantly from monophasic Michaelis-Menten kinetics. Analysis of phytate digestion using isothermal titration calorimetry (ITC) using the single injection method produced a thermogram with two peaks consistent with two periods of high enzyme activity. Continuous-flow electrospray ionization time-of-flight mass spectroscopy (ESI-ToF-MS) provided real-time analysis of phytase catalysis. It was able to show that the first two cleavage steps were rapid and concurrent but the third cleavage step from IP4 to IP3 was slow. The third (IP4 to IP3), fourth (IP3 to IP2) and fifth (IP2 to IP1) cleavages were effectively sequential due to the preferred association of the more phosphorylated species with the phytase catalytic site. This created a bottleneck during the cleavage of IP4 to IP3 until the point at which IP4 was exhausted and was followed by the rapid cleavage of IP3 to IP2, which was observed as the second peak in the ITC thermogram. This work illustrates the importance of an orthogonal approach when studying non-specific or complex enzyme catalyzed reactions.

This study evaluated the relationship between salt-soluble protein (SSP) of maize and the apparent ileal digestibility (AID) of complete diets in response to exogenous α-amylase supplementation in broiler chickens. Samples of 12 maize batches originating from the mid-north and northeast of China were analyzed for SSP. Six of the 12 sources of maize with a wide variation of SSP (from 21.1 % to >50 %) were selected. Six maize-soybean meal basal diets were formulated, including each source of maize with or without the addition of α-amylase (Ronozyme® HiStarch; DSM Nutritional Products). A total of 960 day-old male Arbor Acres Plus broiler chickens were randomly allocated to 12 treatments with 8 replicates per treatment in wired cages and fed experimental diets in 2 phases (d 1−14; d 15−28). At d 28, 4 birds selected from each cage were euthanized for evaluation of apparent ileal digestibility (AID) of starch and energy. The addition of α-amylase reduced the feed conversion ratio (FCR) of chickens from 1 to 28 d (1.407 vs. 1.426) compared to the basal diets across maize batches, particularly from 1 to 7 d (1.049 vs. 1.078). An interaction between maize batch and α-amylase supplementation on FCR was detected only at 7 d, when the batch with the lowest SSP exhibited the greatest response to α-amylase. Neither a main effect of α-amylase nor an interaction with maize batch on AID of starch were detected (P > 0.05). Nonetheless, α-amylase supplementation increased ileal digestible energy (IDE) from 12.21 to 12.50 MJ/kg dry matter across maize batches. These increments were mainly driven by the maize batch with the lowest SSP. α-amylase supplementation reduced the variability of IDE from a coefficient variance (CV)=5.2 % to a CV=0.7 % across maize batches. Interestingly, there was a strong negative correlation (r

A study was conducted to compare maize, wheat and sorghum as the main feed grain in standard phytase and xylanase supplemented diets for broiler chickens. Six diets with different grain varieties (two wheat, two sorghum and two maize) were formulated in accordance with Ross 308 recommendations for starter, grower and finisher diets and were offered from 1 to 10, 11–26 and 27–35 days post-hatch, respectively. The six treatments were offered to 672 male Ross 308 chicks, with eight replicate cages per treatment and 14 birds per cage from 1 to 10 days post-hatch and 6 birds per cage from 11 to 35 days post-hatch. Over the 1–35 day experimental period, birds offered diets based on maize B generated the most efficient feed conversion ratio (FCR, 1.380), whereas birds offered red sorghum-based diets generated the poorest FCR (1.478). Likewise, in the finisher phase, birds offered both maize and wheat generated significantly greater apparent metabolisable energy (AME, MJ/kg DM), AME to gross energy ratio (AME:GE, MJ/MJ) and nitrogen corrected AME (AMEn, MJ/kg DM) than birds offered sorghum-based diets. Birds offered diets containing wheat A generated the greatest starch digestibility coefficient in the jejunum and ileum in both starter and finisher diets and red sorghum outperformed white sorghum in terms of AME and starch digestibility. In the ileum, broiler chickens offered finisher diets based on wheat B had the highest protein digestibility. In conclusion, birds offered maize-based diets achieved the best growth performance and energy utilisation followed by birds offered wheat- and sorghum-based diets.

Simple Summary The liver is a multi-purpose organ, with involvement in bile secretion, and lipid, carbohydrate and protein metabolism, as well as a number of other metabolic functions. This organ can adapt easily to changes in feed and the environment. Being at the centre of a number of digestive, metabolic and productive activities, it is essential to have a better understanding of this organ and the factors affecting liver functionality. Abstract Despite having huge responsibilities in avian species, published reports on the influence of dietary factors and other possible constraints on the size, development and function of liver are limited. Consideration of the factors that could influence and alter liver function is therefore of critical relevance. In the current review, aspects of liver structure and function, and the influence of feed restriction, anti-nutritional factors, structural components and feed additives on liver are discussed. Effects of feed technology techniques such as thermal treatment and pelleting, feed particle size and whole grain feeding on the liver are also reviewed. A discussion of lipogenesis and lipid storage in poultry is presented to provide a better understanding and to differentiate the normal pathways of lipid metabolism from abnormal (i.e., disordered) pathways. The liver is the main site of fat synthesis in poultry, but under certain conditions, excessive fat can accumulate in the liver and cause problems. Factors contributing to the fatty liver syndrome are also examined.

A total of 1,408 male broiler chickens were used to evaluate the impact of age and duration of feeding low-phosphorus (P) diet on the efficacy of phytase using growth performance, nutrient utilization, tibia ash, and plasma indices. Diets were formulated with 2 non-phytate P (nPP) concentrations (i.e., 0.20 and 0.40%) and 2 phytase concentrations (i.e., 1,000 and 2,000 FTU/kg) added to the 0.20% nPP diet. Four dietary treatments with 8 replicate cages each were fed to broiler chicks at different ages and for different duration. Specifically, these were days 6 to 8 (12 birds per replicate), 12 to 14, 9 to 14, 20 to 22, or 6 to 22 (8 birds per replicate). Parameters were measured on the last day of each period. Duration of feeding effect was examined by comparing responses of birds fed for 2 or 5 D at day 14 and for 2 or 16 D at day 22; age effect was determined by comparing responses of birds fed for 2 D at age 8, 14 and 22 D post-hatching. Body weight gain and gain-to-feed ratio were increased (P < 0.01) in birds fed diets supplemented with phytase; however, an increase in duration of feeding improved (P < 0.01) feed efficiency with birds fed for 16 D performing better than birds fed for 2 D at day 22. In addition, phytase supplementation improved (P < 0.01) apparent P and calcium digestibility and retention, but the age effect on phytase efficacy was more apparent at day 14 and the duration of feeding effect was evident in birds fed for 2 D due to the increased levels of mineral utilization at that age/duration of feeding as compared with the other groups. The results of this study show that phytase efficacy was at optimum in birds fed low-P diet for 2 D at day 14. This period can be recommended for further bioefficacy studies of phytase.

The effect of phytase on phosphorus retention, broiler (Gallus gallus) performance and bone mineralization in diets with reduced inorganic phosphate concentration is well documented. Furthermore, so-called 'extra-phosphoric' effects of phytase have been described in the literature that may be associated with changes in mineral and amino acid partitioning and requirements per se. In particular, the role of myo-inositol in phytase responses is implied but not well elucidated. It was the purpose of the experiment reported herein to explore the effect of phytase on broiler growth, nutrient digestibility, blood biochemistry and gene expression. A 5-week broiler floor pen trial was conducted to evaluate the effect of supplementation of a moderately phosphorus-deficient diet with 1000 U/kg of a 6-microbial phytase. Parameters measured were growth performance, phosphorus (P), calcium (Ca) and myo-inositol plasma concentrations, apparent ileal P digestibility, bone mineralization, breast meat weight and Pectoralis major muscle transcriptome. Supplementation of the diet with phytase improved weight gain during the starter period (18%) and the whole period (24%) compared with animals that received the control diet (p

A study was conducted to evaluate the effects of dietary α-amylase and β-xylanase supplementation of corn-soy diets, formulated with or without supplemental phytase, on growth performance, energy utilization, and starch digestibility in broiler chickens. A total of 336 slow-feathering, Cobb × Cobb 500 male broilers were randomly distributed to 6 treatments having 8 replicates of 7 birds each. Birds were fed a common starter diet to d 14 post-hatch (3,050 kcal/kg AMEn, 21.7% CP, 1.05% Ca, and 0.53% nPP). The experimental diets were provided afterwards until d 25. A 2 × 3 factorial arrangement of 2 control diets (basal = corn-soy diet without added phytase or PHY = corn-soy diet formulated with 1,000 phytase units/kg) and 3 carbohydrase supplementations (0, 80 kilo-Novo α-amylase units/kg, or 80 kilo-Novo α-amylase units/kg + 100 fungal β-xylanase units/kg) was used from d 14 to 25. Excreta were collected from 21 to 24 d and all birds were euthanized at 25 d for jejunum and ileum content collection. Samples of feed, excreta, and jejunal and ileal digesta were analyzed for determination of total tract retention and ileal apparent digestibility. No interactions between diet and carbohydrase were observed. Broilers fed diets formulated with phytase or supplemented with amylase + xylanase had higher BW gain (BWG) and lower FCR (P < 0.05) when compared with birds fed diets without carbohydrases. Relative to the basal diet, AMEn was increased (P < 0.01) by 70 kcal/kg and 99 kcal/kg when birds were fed the diet supplemented with amylase and amylase + xylanase, respectively. Starch digestibility in the jejunum and ileum was increased (P < 0.05) by 3.5% and 2.4%, respectively, when birds were fed the diet supplemented with amylase + xylanase. Results from this experiment show that corn-soy diets having phytase and supplemented with amylase and xylanase led to increased growth performance, AMEn, and starch digestibility in broilers. Furthermore, the efficacy of exogenous amylase and xylanase was independent of the presence of microbial phytase.

Anthropogenic environments can offer rich sources of energy to urban wildlife, but little is known about how they impact on nutritional balance and food selection. Common mynas (Sturnus tristis) provide a powerful model system for testing the nutritional constraints and priorities of an invasive species that has successfully adapted to urban environments. Here, we use behavioral observations, field-based feeding trials, videography, and the right-angled mixture triangle model (RMT) to examine the macronutrient preferences of these invasive birds. Our behavioral observations showed that mynas consumed insects (40.6%), worms (33.2%), human discards (17.6%), and plants (8.6%). Our feeding trials using nutritionally defined foods showed that mynas had a clear preference for food dishes containing only high-protein (HP) pellets over high-lipid (HL) or high-carbohydrate (HC) pellets. In addition, mixed feeders were also presented in 2 combinations: 1) contained equal proportions of HP and HC pellets and 2) equal proportions of HP and HL pellets. HP pellets were selectively consumed from both mixed feeders, this involving an increase in feeding time. Overall, the RMT showed that mynas consumed a higher proportion of protein from the feeders than in their natural diet. Furthermore, the majority of our observations of birds feeding at the dishes containing HP foods ended in intraspecific aggression, suggesting that protein is a contestable resource. These results suggest that mynas at our urban study site are deficient in protein relative to fats and carbohydrates.

An experiment was conducted to determine the true ileal P digestibility of maize and soybean meal for broiler chickens using two methodologies based on the regression method. The two methods differed in dietary protein content and dietary Ca:P ratios in the assay diets used. In Method 1, the test ingredient was used as the sole dietary source of protein and P and a dietary Ca:non-phytate P ratio of around 2:1 was maintained by the addition of limestone. In Method 2, dried egg albumen was used as the additional protein supplement and a dietary Ca:total P ratio of 1.3:1 was maintained by the addition of limestone. For the maize-based diets, disodium phosphate was used as an additional P supplement. Two sets of sequential semi-purified diets containing 200, 460 and 720 g/kg of maize or 400, 510 and 620 g/kg of soybean meal were formulated. Each set was evaluated as a 2 × 3 factorial arrangement of treatments, which included two methods and three inclusion levels. The experiment was conducted as a randomised complete block design and a total of 288 of 21-day old male broilers (Ross 308) were assigned to four blocks based on body weights. Each block had 12 cages (six birds per cage) and the 12 test diets were assigned to a cage within each block. Apparent ileal digestibility coefficient of P was determined by the indicator method and linear regression was used to determine true ileal P digestibility. In both methods, ileal P output and ileal digestible P increased linearly with increasing inclusion levels of maize (P

An experiment was conducted to estimate the true ileal digestibility of P in wheat, sorghum, soybean meal, and corn distiller's dried grains with solubles (DDGS) in broiler chickens. Four semipurified diets were formulated from each ingredient (wheat and sorghum: 236.5, 473, 709.5, and 946 g/kg; soybean meal and corn DDGS: 135, 270, 405, and 540 g/kg) to contain graded concentrations of nonphytate P. The experiment was conducted as a randomized complete block design with 4 weight blocks of 16 cages each (5 birds per cage). A total of 320 21-d-old broilers (Ross 308) were assigned to the 16 test diets with 4 replicates per diet. Apparent ileal digestibility coefficients of P were determined by the indicator method and the linear regression method was used to determine the true P digestibility coefficients. The results showed that the apparent ileal P digestibility coefficients of wheat-based diets were not influenced (P>0.05) by increasing dietary P concentrations, whereas those of diets based on sorghum, soybean meal, and corn DDGS differed (P

The science of nutrition is complex and multifactorial. To render accessible this multidimensional discipline, one-factor-at-a-time experimental approaches are useful. For example, when Met requirements for broilers are investigated, it is common for a Met-deficient diet to be offered to broilers of a specific age, and phenotypic responses to supplemental Met measured. Though these experimental approaches are clearly useful, they are usually focused in scope and do not allow panoptic interpretation across environmental-, bird-, and diet-related factors. An alternative experimental approach has been recently described and is called geometric framework. This framework uses Euclidean geometric vocabulary to describe nutrients, ingredients, animals, and environmental conditions as coordinates in multidimensional space. The current review briefly describes the foundational premises of the geometric framework and how it may be applied to explore the complex and multifactorial interactions that exist in broiler nutrition to derive nutritional tautology.

The effects of sorghum grain variety and conditioning temperature at which broiler diets were steam-pelleted on small intestinal digestion dynamics of starch and nitrogen were assessed. A 2×3 factorial array of treatments comprised two sorghum varieties, with white (Liberty) and red (Venture) pericarps and three conditioning temperatures (70, 80, 90°C). Both sorghums were finely-ground through a 2.0 mm hammer-mill screen prior to incorporation into the diets. Each of the dietary treatments was offered to six replicate cages (6 birds per cage) from 7 to 28 days post-hatch. Digesta samples were collected at day 28 for determination of starch and nitrogen digestibilities and mean retention time in the proximal jejunum, distal jejunum, proximal ileum and distal ileum. The digestion dynamics of starch and nitrogen were determined using an exponential mathematical model to relate digestion coefficients with mean retention times in each small intestinal segment. Increasing conditioning temperatures generated a 'concav e response' in starch digestion rates in white sorghum diets; whereas, there was a 'convex response' in red sorghum diets. Thus, at the intermediate 80°C conditioning temperature, starch digestion rates were at a minimum value for white, but at a maximum value for red sorghum-based diets, which is consistent with the significant sorghum type×temperature interaction (p

The use of carbohydrases and proteases in poultry production occasionally results in inconsistent physiological responses that are difficult to explain. However, it has previously been demonstrated that a substantial portion of the variation in enzyme efficacy is associated with the inherent ileal digestibility of starch, protein and lipid, and so an appreciation for the concentration of the undigested fractions of these nutrients in a diet may help to determine the magnitude and consistency of feed enzyme responses. Considering that the expense of in vivo physiological assays for the assessment of enzyme functional pattern is high, it is crucial to develop suitable in vitro methods to predict the magnitude of enzyme response. The purpose of the current paper is to describe inherent characteristics of poultry diets and feed ingredients in response to carbohydrases and proteases in order to aid the development of in vitro assays to predict feed enzyme functional patterns.

BACKGROUND Vitamin D is an essential component of vertebrate nutrition, and epidemiological surveys confirm a chronic vitamin D insufficiency in the human population. Eggs are one of the few natural sources rich in vitamin D, containing both vitamin D3 (D3) and 25-hydroxyvitamin D3 (25(OH)D3). 25-Hydroxyvitamin D3 is especially useful because it provides five times the relative biological activity of vitamin D. In order to establish the potential for enrichment of eggs with D3 and 25(OH)D3, a total of 162 hens were fed three levels of D3 in combination with three levels of 25(OH)D3. Egg yolks were analysed for their D3 and 25(OH)D3 contents, and egg production, egg weights and feed efficiencies were recorded. RESULTS The contents of D3 and 25(OH)D3 in egg yolk increased significantly with increasing dietary concentrations. There were no significant differences in egg mass, egg weight or feed efficiency. Depending on the dietary concentrations used, it was possible to produce eggs with between 100 and 500 IU vitamin D, providing scope to meet the recommended daily requirement of vitamin D for children or adults. CONCLUSION The addition of higher levels of D3 and 25(OH)D3 produced eggs with sufficient vitamin D to meet the recommended daily requirements of adults and children without any detrimental effect on production parameters. © 2013 Society of Chemical Industry

Two experiments were conducted to examine the influence of sorghum variety and the hydrothermal component of steam-pelleting diets on apparent amino acid digestibility coefficients and digestion kinetics of amino acids, nitrogen and starch in broiler chickens. In experiment one, 84 male Ross 308 chicks were offered steam-pelleted diets based on white (Liberty) and red (Buster) sorghum from 7 to 28 days post-hatch. In experiment two, the same red sorghum-based diets were offered to chicks from 7 to 28 days post-hatch as either unprocessed raw mash or reground mash following steam-pelleting at 95 °C. In both experiments, digesta samples from proximal jejunum, distal jejunum, proximal ileum and distal ileum were collected in their entirety at day 28. The samples were then freeze-dried and weighed for determination of mean retention time in each small intestinal segment. The digestion kinetics of amino acids, nitrogen and starch were determined using an exponential mathematical model to relate apparent digestibility coefficients with mean retention times in each small intestinal segment. In experiment one, white sorghum-based diets had significantly higher average amino acid digestibility coefficients than red sorghum in the proximal ileum and distal ileum (P r = −0.840, P

Early posthatch satellite cell (SC) mitotic activity is a critical component of muscle development and growth. Satellite cells are stem cells that can be induced by nutrition to follow other cellular developmental pathways. The objective of the current study was to determine the effect of restricting protein synthesis on the proliferation and differentiation of SC, using variable concentrations of Met and Cys to modulate protein synthesis. Broiler pectoralis major SC were cultured and treated with 1 of 6 different Met/Cys concentrations: 60/192, 30/96 (control), 7.5/24, 3/9.6, 1/3.2, or 0/0 mg/L. The effect of Met/Cys concentration on SC proliferation and differentiation was measured, and myonuclear accretion was measured by counting the number of nuclei per myotube during differentiation. The 30/96 mg/L Met/Cys treatment resulted in the highest rate of proliferation compared with all other treatments by 72 h of proliferation (P < 0.05). Differentiation was measured with Met/Cys treatments only during proliferation and the cultures receiving normal differentiation medium (R/N), normal proliferation medium and differentiation medium with variable Met/Cys (N/R), or both proliferation and differentiation receiving variable Met/Cys treatments (R/R). Differentiation responded in a dose-dependent manner to Met/Cys concentration under all 3 of these treatment regimens, with a degree of recovery in the R/N regimen cells following reinstatement of the control medium. Reductions in both proliferation and differentiation were more pronounced as Met/Cys concentrations were further reduced, whereas increased differentiation was observed under the increased Met/Cys concentration treatment when applied during differentiation in the N/R and R/R regimens. The number of nuclei per myotube was significantly decreased in the severely Met/Cys restricted treatments (P < 0.05). These data demonstrate the sensitivity of pectoralis major SC to nutritional availability and the importance of optimal nutrition during both proliferation and differentiation for maximizing SC activity, which will affect subsequent muscle mass accretion.

a b s t r a c t Apparent amino acid digestibility coefficients in the proximal jejunum, distal jejunum, proximal ileum and distal ileum of broilers fed sorghum-based diets without or with exoge- nous protease were determined at 28 days post-hatch. The digestion kinetics of amino acids were determined using an exponential mathematical model to relate digestion coefficients at four intestinal sites with mean retention times in each small intestinal segment. Pro- tease increased average digestibility coefficients in the distal jejunum by 12.6% (0.681 vs. 0.605; P

SUMMARY The effect of conditioning temperature on phytase efficacy for growth performance and bone mineralization was evaluated using 432 male Ross broilers. Birds were fed a wheat-soy-based diet that was formulated to be adequate in all nutrients with the exception of available P. Diets were conditioned at 75, 80, 85, or 90°C and fed with (1,000 phytase units/kg) or without 1 of 2 microbial phytases in a 3 × 4 factorial design. Phytase A was found to have greater thermostability than phytase B (78.3 vs. 57.5%) as an average across all conditioning temperatures. Phytase increased (P < 0.05) BW gain from d 0 to 21 and birds fed diets containing phytase A were significantly heavier than birds offered diets with phytase B. Increasing conditioning temperature decreased (P < 0.01) BW gain. Supplementing diets with phytase improved (P < 0.05) FE and birds fed diets containing phytase A were more efficient (P < 0.05) than broilers fed diets containing phytase B. Tibia ash concentrations were improved (P < 0.05) by approximately 10% with phytase A and B compared with birds fed diets without phytase. Birds fed phytase A diets had higher (P < 0.05) bone ash concentrations than birds that received the diet containing phytase B. In conclusion, the inclusion of an intrinsically thermostable exogenous phytase before pelleting would be of benefit to bird performance and bone mineralization in broilers.

Grain sorghum is grown for consumption by both human and animals; sorghum-based diets are offered to ruminants, pigs and poultry. Sorghum is included in animal diets primarily as an energy source, being largely derived from starch. However, the efficiency of utilisation of energy from sorghum is variable and this may be problematic for animal production. Starch granules are surrounded by kafirin protein bodies and both are embedded in the glutelin protein matrix in the sorghum endosperm. Protein–starch interactions in the sorghum endosperm may limit starch hydrolysis and its availability. The digestibility of protein/amino acids in sorghum is usually inferior to the other cereal grains. Kafirin, which is the dominant protein fraction in sorghum, is poorly digested and deficient in basic amino acids, especially lysine. Sorghum contains more phenolic compounds and phytate than the other cereal grains and both phenolics and phytate may impede digestion by directly or indirectly binding with protein and starch. As considered in this review, various feed processing technologies have been evaluated to improve sorghum utilisation in pigs and poultry. Sorghum varieties with a hard endosperm tend to be more popular in breeding programmes due to their insect resistance and high yield. The texture of sorghum grains varies with the proportions of corneous and floury endosperm. The extent of particle size reduction and its uniformity following grinding is critical to growth performance in pigs and poultry. Sorghum is especially vulnerable to hydrothermal processes which markedly reduce the in vitro pepsin digestibility of sorghum proteins. Thus steam-pelleting, steam-flaking and wet-extrusion, which involve heat and moisture, may lead to undesirable physico-chemical changes in sorghum including disulphide linkage formation in kafirin protein bodies. Dry-extrusion where heat is generated by friction may enhance starch digestibility by gelatinising starch and disrupting sorghum structures without the addition of moisture. Combining reducing agents with hydrothermal processes may enhance the solubility and digestibility of sorghum protein by either cleaving disulphide linkages or preventing their formation. The inclusion of exogenous enzymes in pig and poultry diets is an established practice to improve performance of monogastric species and phytate-degrading enzymes are of particular relevance due to the relatively high phytate contents in sorghum. Additional strategies including irradiation may also have potential to enhance nutrient utilisation in sorghum. Pigs and poultry may respond differently to any strategy due to fundamental differences in gastrointestinal structure and physiology, which is particularly true of grain particle size.

The use of enzymes has increased dramatically in the last 20 years, and yet the fact that perhaps one of their most important actions is in mediating the size and composition of microbial populations is still largely unrecognized. As the public press for increasingly antibiotic (and by extension coccidiostat) free diets, it is clear that this under-investigated facet of enzyme action warrants far greater scrutiny. Until quite recently it was assumed that the intestinal microbiota were simply reactive to the nutrients left behind after digestion had completed. However it now seems that intestinal microbial population size and composition clearly plays a very large role in determining the extent of digestion accomplished by the host and by extension, growth rate and efficiency. This is becoming increasingly becoming apparent with the advent of new molecular techniques coupled with statistical methods which are beginning to identify desirable and undesirable clusters of organisms as far as good performance is concerned, although the variability in techniques utilised is hampering progress. The fact that exogenous enzymes not only influence the partitioning of nutrients to the host but also, through their action, produce nutrients for specific populations of bacteria, means that they are multifactorial in their effect. As a result their effects are influenced by many other factors such as presence of antibiotics, health status/disease challenge of the animals and quality of ingredients fed. Understanding of such interactions will lead to a more predictable and profitable outcome for the end user.

Calcium is the most prevalent mineral in the body and is important for many physiological processes. However, the amount of calcium in modern diets has both economic and nutritional consequences for producers. Dietary calcium has been shown to reduce the efficacy of both endogenous and exogenous phytases resulting in decreased phytate-phosphorus availability, increased phosphorus excretion as well as facilitating the formation of mineral-phytate complexes. Reducing the concentration of dietary calcium has been reported to improve phytase efficacy and phytate-phosphorus availability, however, this is often at the expense of optimal skeletal integrity. Choice feeding employs the principle that poultry have the ability to select a nutritionally balanced diet from multiple sources and previous studies have shown that poultry have a calcium specific appetite. However, the evaluation of choice feeding systems for broilers has predominantly focussed on the effects of providing separate sources of protein and energy concentrates. Though literature is available for laying hens, scant information is available pertaining to choice feeding of a separate calcium source for broilers. This paper reviews the available information on choice feeding systems in poultry with focus on the application of this in broiler production systems.

Phytases have been used commercially since the early 1990s and have been the focus of considerable and sustained research for many decades. Despite this heroic effort there are still areas of persi...

An experiment was conducted to evaluate the effects of dietary enzymes on performance, tibia ash, and intestinal goblet cells of broilers administered a live coccidia oocyst vaccine (Coccivac B, Schering Plough, Kenilworth, NJ). Cobb 500 straight-run broilers were obtained and one-half of the chicks were sprayed with the live coccidia oocyst vaccine. Chicks were weighed and placed in battery brooders with respect to nonvaccinated or vaccinated group according to dietary treatment. The 8 dietary treatments were a positive control (0.90% Ca and 0.45% available P), a negative control (NC; 0.80% Ca and 0.35% available P), NC + phytase (PHY), NC + protease (PRO), NC + xylanase (XYL), NC + PHY+ PRO, NC + PHY + XYL, and NC + PHY + PRO + XYL. A diet x vaccination interaction (P > 0.05) was not observed for feed intake or BW gain. Feed conversion ratio was improved (P [less-than or equal to] 0.05) in birds fed NC + PHY + XYL compared with NC. Vaccination reduced (P [less-than or equal to] 0.05) feed intake and BW gain from d 0 to 18. Tibia ash was reduced (P [less-than or equal to] 0.05) in the NC and PRO or XYL diets. Vaccination increased goblet cell numbers in the duodenum of birds fed XYL, whereas no differences were found in goblet cell numbers between nonvaccinated and vaccinated birds in other dietary treatments, which resulted in a diet x vaccination interaction (P [less-than or equal to] 0.05). Protease decreased and NC + PHY+ PRO increased goblet cells in the jejunum at d 7, which resulted in a diet x vaccination interaction (P [less-than or equal to] 0.05). At d 18, NC + PHY + XYL was the only diet in which vaccination decreased goblet cells in the jejunum, resulting in a diet x vaccination interaction (P [less-than or equal to] 0.05). The data indicate that NC + PHY + XYL improved the feed conversion ratio in broilers fed corn-soybean meal diets. The vaccination x dietary enzyme interaction altered the number of goblet cells in the small intestine. Dietary enzyme supplementation did not alleviate reductions in growth performance associated with the use of a live coccidia oocyst vaccine.

1. This experiment investigated growth performance and nutrient utilisation responses of broilers to partial replacement of maize and soyabean meal in broiler diets with 100 g kg(-1) maize Distillers' Dried Grain with Solubles (mDDGS) as well as responses to supplementation of an admixture of carbohydrases and protease (XAP) or phytase individually or in combination in the diets. 2. A total of 288 one-day-old broilers were allocated to 8 treatments in a randomised complete block design and a 2 x 2 x 2 factorial arrangement of treatments. The three factors were two levels each of mDDGS (0 or 100 g kg(-1)), phytase (0 or 1000 FTU kg(-1)), and XAP (0 or 500 mg kg(-1)). 3. Each treatment had 6 replicate cages with 6 birds per replicate cage. The control diets were formulated to meet all nutrient requirements of broilers according to National Research Council recommendations of 1994, but were marginally deficient in non-phytate P and ME. 4. Weight gain and gain:food were higher in broilers receiving diets containing mDDGS. The coefficient of apparent ileal N digestibility was lower in diets with mDDGS. Phytase increased the coefficient of apparent ileal DM digestibility in all diets. 5. Phytase improved the coefficient of the apparent total tract DM retention independently of mDDGS and tended to improve the coefficient of apparent P retention in the diets without mDDGS. The enzymes were additive in their effects in the diets with mDDGS. Overall, the results showed that adding 100 g kg(-1) mDDGS to a maize-soyabean meal diet had no negative effect on growth when energy and nutrient concentrations were similar to the maize-soyabean meal diet, and that phytase or an admixture of carbohydrases and protease individually or in combination modestly improved nutrient utilisation independently of mDDGS addition. Combination of the enzymes did not produce greater benefit than the use of phytase alone.

1. The effect of various doses of xylanase and glucanase on the performance and ileal nutrient digestibility of broiler chickens fed on maize/soy-based diets was evaluated. 2. A total of 960 male broilers were used in separate growth and digestibility trials with each involving 10 treatments and 6 replicates. The 10 treatments included a positive control reference diet, a negative control diet with a lower energy density and 8 further diets where xylanase and glucanase were added to the negative control, individually and in combination. 3. Birds which received the negative control diet returned poorer (6 points; P < 0.05) feed conversion ratios compared with those fed on the positive control, confirming the lower energy density of the negative control diet. Ileal digestibility of energy determined at 21 and 42 d was also significantly lower for the negative control compared with the positive control. At d 21 birds that received the negative control diet returned lower ileal amino acid digestibility (for most amino acids) compared with their counterparts fed on the positive control whereas at d 42 this effect was not apparent. 4. Supplementation of the negative control with both glucanase and xylanase improved feed conversion ratio (FCR) and ileal nutrient digestibility. When both enzymes were added simultaneously a sub-additive effect (i.e. simultaneous use resulted in benefits greater than either enzyme independently but less than the sum of the individual effects) was observed, with the best performance achieved with the combination of xylanase (16 000 BXU/kg) and glucanase (30 000 BU/kg). 5. It can be concluded that the removal of oil to accommodate the anticipated energy digestibility improvement with enzymes can have deleterious effects on FCR and ileal amino acid digestibility in young broilers which enzymes may not adequately mitigate. Thus, in order to maximise the response to non-starch polysaccharide degrading enzymes in maize/soy-based broiler diets, it may be beneficial to consider a combination of xylanase and glucanase and to apply moderation when removing added fat in the starter diets.

The usefulness of carbohydrases in corn/soy-based diets for poultry is still unclear and all the more so when phytase is present in the feed. Though there are many interacting factors involved in dictating the measured response to an exogenous enzyme the most influential is the nutritional value of the diet to which it is added. The inherent ileal digestibility of starch, protein and lipid in a corn/soy-based diet varies from around 70% to over 95% and this variance explains up to 90% of the variance in enzyme response. An appreciation for the concentration of undigested starch, protein and lipid in any given diet is an important starting point for the prediction of the effect of the enzyme on digestible energy and amino acids. Instructively, around 15-25% of this undigested fraction can be rendered digestible with the addition of xylanase and so the magnitude of the response is largely explained by the quantity of this undigested portion. As phytase improves the digestibility of the diet, effectively reducing the concentration of undigested amino acids and energy it can be predicted that xylanase will deliver less value in a diet which has already been improved with phytase. It is the purpose of the current paper to describe these effects and the implications for the strategic selection of enzymes for corn/soy-based poultry diets.

Despite increasing practical experience and cascades of scientific reports on exogenous microbial phytases, several issues associated with their use remain unresolved because of the ambiguous and, at times, conflicting data that has been generated. One possible cause of these inconsistent outcomes is dietary calcium (Ca) levels, which are mainly derived from limestone. Thus the purpose of this review is to examine Ca interactions with dietary phytate and phytases, particularly exogenous, microbial phytases, and their consequences for poultry and pigs. The polyanionic phytate molecule has a tremendous capacity to chelate cations and form insoluble Ca–phytate complexes, which are refractory to phytase activity. Thus Ca–phytate complex formation along the gastrointestinal tract, where one phytate (IP6) molecule binds up to five Ca atoms, assumes importance and approximately one third of dietary Ca may be bound to phytate in digesta. Consequently, phytate limits the availability of both P and Ca as a result of insoluble Ca–phytate complex formation, the extent of which is driven by gut pH and molar ratios of the two components. It is accepted that Ca–phytate complexes are mainly formed in the small intestine where they have a substantial negative influence on the efficacy of mucosal phytase. However, exogenous phytases are mainly active in more proximal segments of the gut and lower pH levels, so their efficacy should not be influenced by Ca–phytate complexes in the small intestine. There is, however, data to indicate that Ca and phytate interactions occur under acidic conditions with the formation of soluble and insoluble Ca–phytate species, which could negatively impact on exogenous phytase efficacy. Also, Ca will tend to elevate gut pH because of limestone's very high acid binding capacity, which will favour Ca–phytate interactions and may influence the activity of exogenous phytases depending on their pH activity spectrum. The de novo formation of binary protein–phytate complexes that are refractory to pepsin hydrolysis may be fundamental to the negative impact of phytate on the digestibility of protein/amino acids. However, high dietary Ca levels may disrupt protein–phytate complex formation by interacting with both phytate and protein even at acidic pH levels, thereby influencing the outcomes of phytase amino acid digestibility assays. Finally, it is increasingly necessary to define the Ca and nonphytate-P requirements of pigs and poultry offered phytase-supplemented diets.