Age-Related Variations in the Apparent Metabolizable Energy of Meat and Bone Meal for Broilers.

The influence of broiler age on the apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) of meat and bone meal (MBM) was investigated. A corn-soy basal diet and an experimental diet wherein 300 g/kg of the basal diet was replaced (w/w) with MBM were developed. The diets, in pellet form, were fed to six replicate cages across six age groups, namely d 1 to 7, 8 to 14, 15 to 21, 22 to 28, 29 to 35 or 36 to 42 d post-hatch. Birds were fed either a starter diet from d 1-21 or a finisher diet from d 22-35. Basal and experimental diets were introduced on d 1, 8, 15, 22, 29 and 36 with 10 (d 1-7), 8 (d 8-14) and 6 (d 15-42) birds per replicate. Total collection of excreta was carried out during the last 4 d of each age period. A linear decrease (p < 0.001) in the retention of dry matter and nitrogen was observed with advancing age. The AMEn of MBM showed a linear increase (p < 0.05), rising from 12.56 MJ/kg during d 1-7 to 13.90 MJ/kg during d 29-35, followed by a decline to 13.41 MJ/kg during d 36-42. The current findings showed that the energy utilization of MBM increased with the advancing age of broilers. Age-dependent AMEn values of MBM may need to be considered when MBM is included in feed formulations.

Feeding Value of Lupins, Field Peas, Faba Beans and Chickpeas for Poultry: An Overview.

Grain legumes are fair sources of protein, amino acids and energy, and can be used as a replacement for soybean meal in poultry feed formulations as the soybean meal becomes short in supply and costly. However, a concern associated with the use of grain legumes in poultry feeding is the presence of antinutritional factors. The effective processing and utilisation of these grain legumes in poultry feeding are well documented. The current review focuses on four selected grain legumes (lupins [Lupinus albus and Lupinus angustifolius], field peas [Phaseolus vulgaris], faba beans [Vicia faba] and chickpeas [Cicer arietinum]) and their nutrient content, the presence of antinutritional factors, processing methods and feeding value, including updated data based on recent research findings.

Effect of age on the standardized ileal amino acid digestibility of soybean meal and canola meal in broilers.

Standardized ileal digestibility coefficients (SIDC) of nitrogen (N) and amino acids (AA) in two protein sources (soybean meal [SBM] and canola meal [CM]) were investigated at six broiler ages (d 7, 14, 21, 28, 35, and 42). Two assay diets were formulated to contain either SBM (413 g/kg) or CM (553 g/kg) as the sole dietary AA source. Titanium dioxide (5 g/kg) was added as an indigestible marker. A total of 696 male broilers at 1 d old were allotted to 12 replicate cages per age group. Each assay diet was offered to birds for 4 d prior to the ileal digesta collection on d 7 (14 birds/cage), 14 (12 birds/cage), 21 (10 birds/cage), 28 (8 birds/cage), 35 (8 birds/cage) and 42 (6 birds/cage), respectively. The apparent digestibility coefficients were standardized using age-specific basal endogenous AA flows. In the SBM group, though the SIDC of N tended to be influenced (quadratic; P = 0.075) by age, no linear or quadratic response of age effect was observed on the average SIDC of indispensable (IAA) and total AA (TAA). An age effect (quadratic; P < 0.05) was observed on the average SIDC of dispensable AA (DAA) in SBM with the highest value recorded at d 7, followed by a decrease from d 14 to 28, which increased beyond d 35. The SIDC of some individual AA (Arg, Thr, Trp, Cys, Pro) were affected (P < 0.05 or P < 0.001) in a quadratic manner by age. In the CM, the SIDC of N, average SIDC of IAA, DAA and TAA were influenced (quadratic; P < 0.05 or P < 0.001) by age. The SIDC of N and average SIDC of DAA and TAA were higher from d 7 to 14, declined at d 21, and then increased beyond d 28. The average SIDC of IAA was low between d 7 and 28 and increased thereafter. The SIDC of individual AA were affected (linear or quadratic; P < 0.05 or P < 0.001) by different magnitudes by age. The age influence on the SIDC AA was variable, depending on the protein source and AA. The results demonstrate that age-specific SIDC AA data might need consideration in broiler feed formulations.

Calcium Nutrition of Broilers: Current Perspectives and Challenges.

Calcium (Ca) plays an essential role in poultry nutrition as 99% of Ca is located in birds' skeletal system. However, oversupply of Ca rather than deficiency of Ca is the current concern in commercial broiler diets. Calcium is an inexpensive dietary nutrient due to the cheap and abundant availability of limestone, the major Ca source; therefore, little attention was given to the oversupply of Ca in the past. The recent shift in the use of digestible P in broiler feed formulations has necessitated a closer look at digestible Ca, as Ca and P are interrelated in their absorption and postabsorptive utilisation. In this context, data on ileal digestibility of Ca and P in ingredients has been determined. Preliminary data on the digestible Ca and digestible P requirements for the different growth stages of broilers have also recently become available. The present review focusses on these recent advances in Ca nutrition. In addition, aspects of homeostatic control mechanisms, different Ca sources and factors influencing Ca digestibility in poultry are covered.

Broiler Age Influences the Apparent Metabolizable Energy of Soybean Meal and Canola Meal.

The effects of broiler age on the apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) of soybean meal (SBM) and canola meal (CM) were examined. A corn-SBM basal diet was developed, and two test diets were formulated by substituting (w/w) 300 g/kg of the basal diet with SBM or CM. Six groups of broiler chickens, aged 1−7, 8−14, 15−21, 22−28, 29−35 or 36−42 d post-hatch, were utilized. Each diet, in pellet form, was randomly allocated to six replicate cages in each age group. Except for the 1−7 d age group, the birds were fed a starter (d 1−21) and/or a finisher (d 22−35) diet prior to the introduction of the experimental diets. The number of birds per cage was 10 (d 1−7), 8 (d 8−14) and 6 (d 15−42). The AME and AMEn of SBM and CM were determined by total excreta collection. The data for each protein source were subjected to orthogonal polynomial contrasts using the General Linear Models procedure. Bird age decreased the retention of dry matter quadratically (p < 0.001) for both SBM and CM. The retention of nitrogen decreased linearly (p < 0.001) with the advancing age of broilers for SBM and CM. The AMEn of SBM and CM decreased quadratically (p < 0.001) as the birds grew older. The highest AMEn was observed during week 1 for both SBM and CM, then declined until week 3, followed by increases thereafter. The current results showed that the age of broiler chickens influenced the AMEn of SBM and CM and supported the use of age-dependent AMEn of feed ingredients in diet formulations.

Barley, an Undervalued Cereal for Poultry Diets: Limitations and Opportunities.

The supply of conventional cereal grains, especially of maize, will be a significant constraint to the future growth of the poultry industry. Various alternative feed ingredients are being tested to replace maize in poultry diets. Barley (Hordeum vulgare L.) is one such feed ingredient, the use of which remains limited in poultry diets due to its low metabolisable energy, presence of anti-nutritive, soluble non-starch polysaccharides and consequent inter-cultivar variability. Differences in research methodologies used in published studies have also contributed to the inconsistent findings, preventing a good understanding of the nutritional value of barley for poultry. The importance of using accurate nutrient profiles, specifically metabolisable energy and digestible amino acids, for specific barley cultivars to formulate barley-based diets is emphasised. Nutritionists should also pay close attention to feed processing conditions tailored to the specific barley cultivars to increase the barley inclusion in poultry diets.

Influence of Conditioning and Expansion Characteristics on the Apparent Metabolizable Energy and Standardized Ileal Amino Acid Digestibility of Full-Fat Soybeans for Broilers.

This study investigated the influence of short-term and long-term conditioning and expansion on the nitrogen-corrected apparent metabolizable energy (AMEn) and standardized ileal digestibility (SID) of amino acids (AA) in full-fat soybeans (FFSB) for broilers. A batch of raw soybeans was used to manufacture 10 FFSB products (T0 to T9) by applying various combinations of conditioning and expansion. The AMEn and SID AA of FFSB were determined by difference and direct methods, respectively. All heat treatments increased (p < 0.001) the AMEn compared to raw FFSB. The sample subjected to long-term conditioning at 100 °C for 6 min and expansion at 18 kWh/t (T5) supported 3.88 MJ/kg higher AMEn than the raw FFSB. Raw FFSB had the poorest (p < 0.05) AA digestibility. Among the heat-treated samples, the highest (p < 0.05) SID AA was recorded for T5. The results demonstrated that the long-term conditioning of FFSB at 100 °C for 6 min prior to expansion with 18 kWh/t specific energy input enhanced metabolizable energy and SID AA. Further increases in conditioning time from 6 to 9 min or expansion of specific energy input from 18 to 28 kWh/t did not yield additional benefits to energy utilization and AA digestibility of FFSB.

Influence of Broiler Age on the Apparent Metabolizable Energy of Cereal Grains Determined Using the Substitution Method.

The present study investigated the influence of broiler age on the AMEn of wheat, sorghum, barley, and corn using the substitution method at six different ages (days 7, 14, 21, 28, 35, and 42). A corn-soybean meal basal diet was formulated and, the test diets were developed by replacing (w/w) 300 g/kg of the basal diet with wheat, sorghum, barley, or corn. Bird age influenced (p < 0.001) the AMEn of wheat and sorghum but had no effect (p > 0.05) on those of barley and corn. The AMEn of wheat increased with age (p < 0.001) from 12.53 MJ/kg DM in week 1 to 14.55 MJ/kg DM in week 2, then declined subsequently, but no linear or quadratic responses were observed. The AMEn of sorghum demonstrated a quadratic response (p < 0.05), increasing from 12.84 MJ/kg DM in week 1 to 13.95 MJ/kg DM in week 2, and then plateauing to week 6. Overall, the present results suggest that the effect of broiler age on the AMEn varies depending on the grain type. The current data suggest that the application of age-dependent AME or AMEn of wheat and sorghum will lead to more precise feed formulations.

Influence of Age on the Standardized Ileal Amino Acid Digestibility of Corn and Barley in Broilers.

The aim of this study was to determine the standardized ileal digestibility coefficients (SIDCs) of nitrogen (N) and amino acids (AAs) in corn and barley at six different ages (days 7, 14, 21, 28, 35 and 42) of broilers using the direct method. The apparent AA digestibility coefficients were corrected using age-appropriate basal endogenous AA losses. No age effect (p > 0.05) was noted for the SIDC of N in corn. The average SIDC of indispensable AAs (IAAs) and total AAs (TAAs) was influenced in a quadratic manner (p < 0.05) with the values being higher at day 7 that decreased at day 14, increased and plateaued between days 21 and 35 and dropped again at day 42. The average SIDC of dispensable AAs (DAAs) was influenced linearly (p < 0.05). In barley, the SIDC of N and average IAAs, DAAs and TAAs was affected (quadratic; p < 0.001) by age. The digestibility increased from day 7 to 21 and then plateaued up to day 42. The present findings confirm that the SIDC of AA in corn and barley are influenced by broiler age and that the age effect on AA digestibility may need to be considered for precise feed formulation.

Nutrition and Digestive Physiology of the Broiler Chick: State of the Art and Outlook.

Because the intestine is the primary nutrient supply organ, early development of digestive function in newly hatched chick will enable it to better utilize nutrients, grow efficiently, and achieve the genetic potential of contemporary broilers. Published data on the growth and digestive function of the gastrointestinal tract in neonatal poultry were reviewed. Several potential strategies to improve digestive tract growth and function in newly hatched chick are available and the options include breeder nutrition, in ovo feeding, early access to feed and water, special pre-starter diets, judicious use of feed additives, and early programming.

Application of Apparent Metabolizable Energy versus Nitrogen-Corrected Apparent Metabolizable Energy in Poultry Feed Formulations: A Continuing Conundrum.

In the present investigation, N retention, AME, and AMEn data from six energy evaluation assays, involving four protein sources (soybean meal, full-fat soybean, rapeseed meal and maize distiller's dried grains with solubles [DDGS]), are reported. The correction for zero N retention, reduced the AME value of soybean meal samples from different origins from 9.9 to 17.8% with increasing N retention. The magnitude of AME penalization in full-fat soybean samples, imposed by zero N correction, increased from 1.90 to 9.64% with increasing N retention. The Δ AME (AME minus AMEn) in rapeseed meal samples increased from 0.70 to 1.09 MJ/kg as N-retention increased. In maize DDGS samples, the correction for zero N retention increased the magnitude of AME penalization from 5.44 to 8.21% with increasing N retention. For all protein sources, positive correlations (p < 0.001; r = 0.831 to 0.991) were observed between the N retention and Δ AME. The present data confirms that correcting AME values to zero N retention for modern broilers penalizes the energy value of protein sources and is of higher magnitude for ingredients with higher protein quality. Feed formulation based on uncorrected AME values could benefit least cost broiler feed formulations and merits further investigation.

Trends in feed evaluation for poultry with emphasis on in vitro techniques.

Accurate knowledge of the actual nutritional value of individual feed ingredients and complete diets is critical for efficient and sustainable animal production. For this reason, feed evaluation has always been in the forefront of nutritional research. Feed evaluation for poultry involves several approaches that include chemical analysis, table values, prediction equations, near-infrared reflectance spectroscopy, in vivo data and in vitro digestion techniques. Among these, the use of animals (in vivo) is the most valuable to gain information on nutrient utilization and is more predictive of bird performance. However, in vivo methods are expensive, laborious and time-consuming. It is therefore important to establish in vitro methods that are reliable, rapid and practical to assess the nutritional quality of feed ingredients or complete diets. Accuracy of the technique is crucial, as poor prediction will have a negative impact on bird performance and, increase feed cost and environmental issues. In this review, the relevance and importance of feed evaluation in poultry nutrition will be highlighted and the various approaches to evaluate the feed value of feed ingredients or complete diets will be discussed. Trends in and practical limitations encountered in feed evaluation science, with emphasis on in vitro digestion techniques, will be discussed.

Mathematical prediction of ileal energy and protein digestibility in broilers using multivariate data analysis.

A proportional mixture design was used to systematically create a total of 56 diets using ten feed ingredients. Diets differed widely with regards to chemical characteristics and ingredient inclusion levels. Apparent ileal digestibility of energy and protein of the diets were determined in broiler growers fed ad libitum from 21 to 24 d post-hatch. The chemical composition and the in vivo digestibility values were used to establish prediction equations for energy and protein digestibility, using multivariate data analysis. Root mean square error as percentage of the observed means (RMSE%) and residual error were used to evaluate the strength and accuracy of the predictions and to compare predictions based on chemical characteristics with estimates based on table values. The estimates of ileal digestibility of energy from table values were relatively accurate (RMSE% = 5.15) and was comparable to those predicted based on the chemical composition of diets. Estimates of ileal digestibility of protein based on table values were less accurate (RMSE% = 8.21); however, the prediction was improved by multivariate regression (RMSE% = 5.46) based on chemical composition of diets. The best predictors for ileal energy digestibility were starch, crude fiber and phytate contents (P < 0.01) and the best predictors for crude protein digestibility were starch, CF and fat contents (P < 0.05). In conclusion, the ileal digestibility of energy can be accurately predicted using table values; however, the accuracy of prediction of the ileal digestibility of protein can be improved when chemical characteristics of the diet are considered.

Measurement of Endogenous Phosphorus Losses in Broiler Chickens.

The experiment reported herein was conducted to estimate the ileal and excreta endogenous phosphorus (P) losses in broiler chickens. Three purified diets, namely a P-free diet, a gelatin-based diet containing negligible amounts of P, and a casein-based diet with 100% available P, were formulated. Test diets were offered ad libitum from day 25 to 28 post hatch and ileal digesta were collected. Excreta samples were also collected to estimate total tract endogenous P losses. Ileal endogenous P losses in birds fed the casein-based diet were higher (P<0.05) than those in birds fed P-free and gelatin-based diets. The ileal endogenous losses of P in birds fed P-free, gelatin-based, and casein-based diets were 25, 104 and 438 mg/kg dry matter intake, respectively. The endogenous P loss values estimated at the excreta level were 830, 560 and 372 mg/kg dry matter intake, respectively. Ileal and excreta endogenous losses of P in birds fed a casein-based diet were similar (P>0.05), but ileal losses were lower (P<0.05) than the excreta values in birds fed P-free and gelatin-based diets, resulting in a significant (P<0.001) assay diet by site of measurement interaction. The present data demonstrate that values determined for endogenous P losses in broiler chickens vary widely depending on the assay diet used.

Avian Liver: The Forgotten Organ.

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.

Wheat particle size, insoluble fibre sources and whole wheat feeding influence gizzard musculature and nutrient utilisation to different extents in broiler chickens.

A 21-day experiment was conducted to investigate the effects of wheat particle size, insoluble fibre source and whole wheat (WW) inclusion on the gizzard musculature, intestinal architecture and nutrient utilisation of broiler chickens. The following seven treatments, all in mash form, were tested: control diet using finely ground wheat (Fine); control diet using medium-ground wheat (Medium); control diet using coarsely ground wheat (Coarse); fine diet diluted with 10 g/kg lignocellulose (LC); fine diet diluted with 30 g/kg oat hulls (OH); fine diet diluted with 30 g/kg wood shavings (WS); and ground wheat in the fine diet replaced with 50 and 100 g/kg WW during the second (day 8-14) and third (day 15-21) weeks of the study respectively. Except for the LC diet, all treatments increased (p < 0.05) the thickness of the caudodorsal thick muscle of gizzard compared to the fine diet. The highest (p < 0.05) caudoventral thin and cranioventral thick muscle diameters in the gizzard walls were achieved with the OH and WS diets. Feeding OH, WS and WW diets improved (p < 0.05) starch digestibility compared with the fine diet, while medium, coarse and LC diets had no effect (p > 0.05). All diets containing fibre sources (LC, OH and WS) reduced (p < 0.05) the energy digestibility compared to the fine diet. Birds fed OH and WS diets gained the lowest (p < 0.05) weights. Feeding LC, OH, WS and WW diets increased (p < 0.05) the feed per gain compared with the fine diet. The current results suggest that there is a potential for coarse particles, insoluble fibre sources and WW feeding to improve the gizzard musculature and digestibility of some nutrients, with the effect being more pronounced with the inclusion of structural fibre sources.

Feed enzyme technology: present status and future developments.

Exogenous enzymes are now well accepted as a class of feed additives in diet formulations for poultry and pigs to overcome the negative effects of anti-nutritional factors, and to improve digestion of dietary components and animal performance. An overview of the current status of feed enzyme technology, including the different type of enzymes and modes of action, is provided. Variable response to enzyme supplementation is an important reason limiting the widespread acceptance of feed enzymes. The major reasons contributing to these variable responses are discussed. Main features of the next generation of feed enzymes and the various trends that will drive the future use of enzymes are highlighted. The use of feed enzymes in poultry and pig feed formulations is expected to increase in the future and this will be driven by on-going changes in the world animal production. Aquaculture and ruminant industries are emerging markets for exogenous feed enzymes. The article presents some promising patents on feed enzyme technology.

Influence of dehulling on the apparent metabolisable energy and ileal amino acid digestibility of grain legumes for broilers.

BACKGROUND: Removal of hulls may be an effective means of reducing the level of some antinutritional factors and improving the feeding value of grain legumes. Published data on the effects of dehulling on the energy utilisation and amino acid digestibility of grain legumes are limited. This study was designed to investigate the influence of dehulling on the nitrogen-corrected apparent metabolisable energy (AMEn) and apparent ileal amino acid digestibility of faba beans, Australian sweet lupins and peas for broilers. RESULTS: The non-starch polysaccharide contents of all three legume species were decreased by the removal of hulls. Dehulling increased (P < 0.05) the content and ileal digestibility of starch in faba beans but had no effect (P > 0.05) on those in peas. Dehulling increased (P < 0.05) the AMEn of faba beans and lupins but had no effect (P > 0.05) on that of peas. Removal of hulls increased the amino acid concentrations in all three legume species, but the apparent ileal digestibility coefficients of most amino acids were unaffected (P > 0.05). CONCLUSION: Dehulling of grain legumes is nutritionally beneficial in view of the improved amino acid concentrations and metabolisable energy values.

Spatiotemporal mapping of the motility of the isolated chicken caecum.

We studied the caecal contractile activity of the chicken (Gallus gallus) using single caeca that had been cannulated at their proximal and distal ends, and in paired caeca, maintained in situ on excised segments of gut that were cannulated at the colonic and small intestinal ends. Longitudinal and circular contractile patterns were characterised using high-definition spatiotemporal mapping. Low amplitude longitudinal contraction waves of frequency 14.1 cycles/min occurred in the absence of major contractile events. These were termed fast phasic and appeared to be mediated by slow waves. The nature of major spontaneous contractions occurring in the single caecum varied with the level of caecal distension. Type A contractions occurred when the caecum was not distended, originated from variable sites and propagated in both directions. Type B or C contractile events occurred when the caecum was moderately or fully distended, originated from a predominantly distal site and propagated proximally. On diameter maps, each type B event comprised a succession of contractions which had similar propagation speeds, frequency and direction to fast phasic contractions. Type C events were comprised of a succession of higher amplitude contractions with no appreciable propagation. Perfusion of saline via the colon resulted in fluid entering both caeca and the onset of aborad contractions in their proximal canals. Saline was also seen to flow between caeca during contractile events however no saline was seen to enter the small intestine as has been postulated by other workers.

Endogenous flow of amino acids in the avian ileum as influenced by increasing dietary peptide concentrations.

The aim of the present study was to establish whether feeding broiler chickens with diets containing increasing dietary peptide concentrations would cause increases in ileal endogenous amino acid flow. The flow of N and most amino acids increased quadratically (P < 0.05 to 0.001) with increasing dietary concentrations of peptides. The exceptions were the flow of threonine, serine, glycine, tyrosine and cystine, which increased linearly (P < 0.001) with dietary peptide levels. Another notable exception to the general trend was the flow of proline, which was significantly higher (P < 0.01) in birds fed the protein-free diet. The amino acid profile of endogenous protein, expressed as proportion of crude protein, indicated that the ratios of threonine, glutamic acid, proline, glycine, leucine, histidine, arginine and cystine were influenced (P < 0.05) with increasing dietary peptide concentrations. In general, compared with the protein-free diet, the ratios of threonine and arginine in endogenous protein were lower (P < 0.05) and those of glutamic acid, glycine and histidine were greater (P < 0.05) in diets with high concentrations of peptides. The ratio of proline was found to decrease (P < 0.05) with increasing dietary peptide concentrations. These changes in the amino acid profile of endogenous protein are probably reflective of changes in the output of one or more of the components of endogenous protein. Overall, the present results demonstrated that increasing dietary peptide concentrations increased the flow of endogenous amino acid flow at the terminal ileum of broiler chickens in a dose-dependent manner and also caused changes in the composition of endogenous protein. The observed changes in endogenous amino flow will influence the maintenance requirements for amino acids and also have implications for the calculation of true digestibility coefficient of feedstuffs.