Low Apparent Metabolisable Energy Research Articles

Dynamic responses of blood metabolites to nutrient depletion and repletion in broiler chicken nutrition

A total of 720 male Cobb 500 broiler chicks were used in a 5 treatment and 8 replicate experiment to explore dynamic changes in blood metabolites in response to short-term nutrient depletion and repletion. Day old chicks were offered a corn and soybean meal-based common starter diet from d1 to 14 that was formulated to meet all nutrient requirements of the birds. From d15 to 17, the experimental diets were offered, before returning all groups to a common diet from d18 to 20, at which point the experiment was terminated. A total of 5 experimental diets were designed. A standard grower diet served as a control and was offered to 1 of the 5 groups of chicks. The additional 4 experimental groups comprised diets that were low in digestible phosphorus (P), total calcium (Ca), crude protein and digestible amino acids (AA) or apparent metabolizable energy (AME). The common grower diet that was offered from d18-20 was designed to be nutritionally complete and was intended to explore dynamic response to nutrient repletion. Blood was drawn from 8 chicks per treatment at time 0 (immediately prior to introduction of the experimental diets) and then again 3, 6, 12, 24, and 48h after introduction of the nutrient depleted diets. Additionally, blood was drawn 3, 6, 12, 24, and 48h after the introduction of the nutritionally complete common grower diet. Chicks were not sampled more than once. Feed intake, body weight and feed conversion ratio (FCR) were assessed on d14, 17, and 20. Blood metabolites were analyzed using the iSTAT Alinity V handheld blood analyzer, the Vetscan VS2 Chemistry Analyzer and the iCheck Carotene Photometer. Live performance metrics were not affected by the short-term nutrient depletion and all chicks grew normally throughout the experiment. The diet with low digestible P generated a rapid temporary decrease in plasma P and an increase in plasma Ca, that were returned to baseline following the re-introduction of the common grower feed. Introduction of the diet with low total Ca resulted in a significant increase in plasma P, effects which were also mitigated during the nutrient repletion phase. Total plasma protein, albumin and uric acid (UA) were decreased, and plasma glucose increased, in the chicks that received the diet with low crude protein and digestible AA. There was a delayed increase in aspartate amino transaminase (AST) associated with the diets with low digestible P and low AME. These results demonstrate the capacity of blood biochemistry to adapt to quantitative and qualitative changes in nutrient intake. Point-of-care analysis of blood biomarkers offers nutritionists a valuable opportunity to calibrate nutritional matrices for common dietary ingredients, zootechnical feed additives and to optimize diet phase changes. It can be concluded that many blood biomarkers are plastic to changes in diet nutrient density and offer an objective index for optimization of nutritional programs for commercial broiler production.

Non-Starch Polysaccharide-Degrading Enzymes Increase the Performance of Broiler Chickens Fed Wheat of Low Apparent Metabolizable Energy

The effect of a commercial glycanase product (Avizyme TX) on the performance of 4-wk-old broiler chickens fed wheats with low and normal apparent metabolizable energy values was studied. Controls were fed a corn-based diet. Supplementation with the enzyme product significantly (P < 0.01) increased the apparent metabolizable energy of the low metabolizable energy wheat from 12.02 to 14.94 MJ/kg dry matter. The apparent metabolizable energy value of the normal wheat was increased from 14.52 to 14.83 MJ/kg dry matter; this was, however, not significant. Birds fed the low metabolizable energy wheat diet had significantly (P < 0.01) higher digesta viscosity and lower small intestinal starch and protein digestibilities than birds fed the normal wheat diet. Chickens fed the low metabolizable energy wheat tended to grow less than those fed the normal wheat diet. When the low metabolizable energy wheat + enzyme diet was fed, digesta viscosity was significantly (P < 0.01) lower (20.28 vs. 10.36 mPa·s), and small intestinal digestibility coefficient of starch was significantly (P < 0.01) greater (0.584 vs. 0.861) relative to values in birds fed the low metabolizable energy wheat diet alone. Although the protein digestibility coefficient also increased from 0.689 to 0.745, the difference was not significant. Weight gain and feed efficiency of birds fed the low metabolizable energy wheat + enzyme equaled those of controls. The enzyme product significantly (P < 0.01) increased the solubilization of non-starch polysaccharides within the gastrointestinal tract of birds fed both types of wheat diets. This experiment demonstrated that non-starch polysaccharide-degrading enzymes markedly increase the nutritive value of low metabolizable energy wheat broiler chicken diets, suggesting that increased level of viscous non-starch polysaccharides may cause the low apparent metabolizable energy contents of some wheats.

Apparent metabolizable energy requirement of feed-restricted White Pekin duck breeder pullets

A dose–response experiment with 5 dietary apparent metabolizable energy (AME) levels (10.00, 10.62, 11.24, 11.87, and 12.49 MJ AME/kg) was conducted to estimate the AME requirement of White Pekin duck breeder pullets from 8 to 24 weeks of age. A total of 240 8-week-old female White Pekin duck breeder pullets were assigned to 5 experimental treatments, and each treatment was replicated 6 times with 8 birds per replicate. The ducks were reared in raised wire-floor pens from 8 to 24 weeks of age. All duck pullets were restricted-fed by limiting feed intake, and the feed intake increased gradually as age increased. At 24 weeks of age, the body weight, weight gain and feed/gain of each treatment were measured, and the relative weight of abdominal fat, skin and fat, and ovary of pullets and the contents of luteinizing hormone, follicle-stimulating hormone, and estradiol in plasma were also determined. As the dietary energy level increased from 10.00 to 12.49MJ AME/kg, the 24-week-old body weight and weight gain increased linearly or quadratically (P < 0.05) and the feed/gain decreased linearly or quadratically (P < 0.05). The absolute or relative weight of abdominal fat and skin and fat of the duck pullets also showed a linear increasing response to increasing dietary energy (P < 0.05). The duck pullets fed with high dietary energy levels had a higher absolute or relative weight of ovary than the birds fed with low dietary energy (P < 0.05) and this was accompanied by linearly or quadratically increasing plasma follicle-stimulating hormone and estradiol as dietary energy increased (P < 0.05). According to broken-line regression, the AME requirements for feed/gain and relative weight of skin and fat were 12.40, and 11.92 MJ/kg, respectively, and low AME requirements should be considered to control body weight and fat before laying age.

Broilers divergently selected for digestibility differ for their digestive microbial ecosystems.

Improving the digestive efficiency of broiler chickens (Gallus gallus) could reduce organic waste, increase the use of alternative feed not used for human consumption and reduce the impact of feed in production costs. By selecting chicken lines divergently for their digestive efficiency, we showed previously that digestive efficiency is under genetic control and that the two resulting divergent lines, D+ (high digestive efficiency or “digestibility +”) and D- (low digestive efficiency or “digestibility -”), also differ for the abundance of specific bacteria in their caeca. Here we perform a more extensive census of the bacteria present in the digestive microbiota of 60 chickens selected for their low apparent metabolizable energy corrected for nitrogen balance (AMEn-) or high (AMEn+) digestive efficiency in a [D+ x D-] F8 progeny of 200 individuals. We sequenced the 16S rRNA genes of the ileal, jejunal and caecal microbiotas, and compared the compositions and predicted functions of microbiotas from the different intestinal segments for 20 AMEn+ and 19 AMEn- birds. The intestinal segment of origin was the main factor structuring the samples. The caecal microbiota was the most impacted by the differences in digestive efficiency, with 41 bacterial species with abundances differing between highly and poorly efficient birds. Furthermore, we predicted that the caecal microbiota of efficient birds might be enriched in genes contributing to the degradation of short chain fatty acids (SCFA) from non-starch polysaccharides. These results confirm the impact of the genetic selection led on digestibility on the caecal microbiota taxonomic composition. They open the way toward the identification of specific, causal genes of the host controlling variations in the abundances of bacterial taxons.

Identification of chicken intestinal microbiota correlated with the efficiency of energy extraction from feed

The microbiota of the gastrointestinal tract is a complex community of many different species of microorganisms, dominated by bacteria. This diverse population provides the host with an extensive array of enzymes and substrates which, together with the host's metabolic capabilities, provides an extensive metabolome available for nutrient and energy collection. We investigated broiler chickens to determine whether the abundance of certain members of the microbiota was correlated with the relative ability to extract energy from a typical wheat soybean diet. A number of mostly uncultured phylotypes were identified that significantly differed in abundance between birds with high apparent metabolizable energy (AME), measured as the difference between energy consumed and energy excreted, and those with low AME. Among the phylotypes that were more prevalent in birds with high energy efficiency, most were closely associated with isolates of bacterial groups that are commonly recognized as producing enzymes that degrade cellulose and/or resistant starch. Phylotypes that were negatively correlated with performance were all unknown and uncultured, a significant number belonging to an unknown class of Firmicutes. The identification of bacterial phylotypes correlated with the efficiency of energy use opens up the possibility of harnessing these bacteria for the manipulation of the host's ability to utilize energy. Increasing the ability to convert food to body weight is of interest to the agricultural industries, while the opposite is applicable in weight management and obesity control in humans.

Apparent ileal digestibility of amino acids and metabolisable energy value in grains for broilers

Using ileal digestible amino acids in feed optimising will intensify feed protein utilizing and decrease nitrogen excretion to the environment. The study determined the apparent ileal digestibility (AID) coefficients of amino acids in barley, wheat, oats, triticale, maize, and dehulled oats in the diets of 180 Ross broiler chickens (aged 24–35 days). The birds were fed semi-purified diets that contained grain as the sole protein source and chromium-mordanted straw as an indigestible marker. The AID coefficients of the nutrients were assessed using the slaughter technique, and the apparent metabolisable energy (AME) was determined using total excreta collection. The ileal digestibility of the dry matter and organic matter were the highest in maize. The AME of maize was higher than that of other cereals. The ileal digestibility of crude protein was higher in wheat than that in barley, oats and dehulled oats. The AME of wheat was similar to that of barley and oats but lower than that of triticale and dehulled oats. The amino acid AID was highest in wheat (0.86) and triticale (0.85) and lowest in oats (0.79) and barley 0.77). The average amino acid AID was 0.81 in dehulled oats. The threonine AID was the same in all tested ingredients. The lysine, methionine, and cystine AID coefficients were 0.81, 0.79, and 0.71 respectively for barley; 0.86, 0.84, and 0.38 respectively for oats; 0.87, 0.86, and 0.53 respectively for dehulled oats; 0.84, 0.90, and 0.66 respectively for maize; 0.89, 0.88, and 0.77 respectively for triticale; and 0.87, 0.85, and 0.71 respectively for wheat. Results indicated that AME –values of domestic grains (barley, oats and wheat) are in the same level. Especially, low AME value of wheat needs further investigation.;

Variations in starch digestibility in non-ruminants

Starch is the major energy-yielding ingredient in diets for both pigs and poultry, and its effective digestion will have a major impact on their energy balance; a common presumption is that it is completely digested but, whilst this may well be the case over the entire digestive tract (through excreta and faecal analyses), this is rarely found within the small intestine. Starch disappearance from the large intestine is through microbial fermentation whose products, volatile fatty acids, are not used with the same efficiency of metabolic utilisation in energy-yielding pathways as is glucose (the product of amylolysis in the small intestine). Other consequences of incomplete starch digestion in the small intestine may include excessive large intestinal fermentation leading to diarrhoea and dehydration. Variations in small versus large intestinal digestibility for starch have not received attention but it should be in future assessments. Starch from peas is digested less well in the small intestine than from cereals. Separation of starch into different categories (rapidly digested, slowly digested and resistant to digestion) could be a useful development. There is some debate as to whether there is amylase adequacy in the newly hatched chick/post-weaned piglet. However although the activity of α-amylase may well increase beyond these ages, it is still generally believed that poor digestibility values of starch in young broilers cannot be attributed to inadequate levels of α-amylase and is more likely to be attributable to extrinsic and/or intrinsic factors. With respect to piglets, there appears to be a link between feed intake and enzyme activity; thus reduced intake (common in the immediate post-weaning period) may be responsible for limited amylase secretion rather than a capacity for amylase synthesis. There have been numerous studies evaluating the digestibility of starch from wheat in poultry; isolated wheat starch was readily digested in vitro by chick pancreatic α-amylase, even that from wheat with relatively low apparent metabolizable energy (AME) values. Variations in starch digestibility have, nevertheless, been recorded. Thus, it is not starch per se that is poorly utilised in some samples but other factors within wheat may be reducing starch digestibility. The starch/protein interface in the endosperm of wheat (responsible for the ‘hard’ and ‘soft’ endosperm texture) might be responsible for problems with starch utilisation, but no firm evidence exists for this. A key recent development has been the emergence of near-isogenic lines which are very similar except for key characteristics. Thus, lines near-isogenic except for hardness have been used to establish that hard wheats are less well digested in poultry than soft ones. Similarly, wheats containing the IBIR rye translocation are less well digested. Such developments have been crucial as the independent effects of hardness and IBIR cannot be established conclusively if there are other unknown factors present. Thus, random variety trials are of no value in investigations of what influences starch digestion. It is possible that the negative effects of the IBIR translocation may be offset by the positive effects of soft endosperm although it is crucial to point out that endosperm texture is a continuum between very hard and very soft, not simply hard and soft. There have been many attempts to assess starch digestibility in vitro as a means of screening samples. Certainly there has been success in terms of linking in vivo digestibility to rate of in vitro digestibility. However it has been suggested that slowly digested starch will lead to better performance than rapidly digested starch.

Effects of xylanase supplementation on between-bird variation in energy metabolism and the number of Clostridium perfringens in broilers fed a wheat-based diet

Three experiments were conducted to examine: (a) the apparent metabolisable energy (AME) contents, the level of non-starch polysaccharides (NSP), and the extract viscosity value of 9 wheat samples; (b) the efficacy of a xylanase in reducing between-bird variation for AME; and (c) the effect of a xylanase on the number of Clostridium perfringens in broilers fed a low AME wheat diet. Experiment 1 revealed that the AME value of wheat varied from 11.5 to 13.6 MJ/kg dry matter (DM), which negatively correlated with the total NSP level (r = –0.97). Experiment 2 involved a 48-cage individual bird trial, where xylanase increased (P &lt; 0.05) the AME from 12.51 to 13.09 MJ/kg DM and reduced (P &lt; 0.05) its standard deviation from 1.13 to 0.52. The standard deviation for feed conversion ratio, ileal viscosity, and faecal viscosity was also reduced. In this experiment, there was a strong correlation between AME and excreta viscosity (r = –0.81) and the caecal xylanase activity of birds fed the control diet was positively correlated with AME (r = 0.72). In Expt 3, xylanase reduced the number of Clostridium perfringens, the causative agent for necrotic enteritis, to a non-detectable level in the ileum and caeca of broilers fed a low-ME wheat diet.

White and Wholemeal Flours from Wheats of Low and Higher Apparent Metabolizable Energy Differ in Their Nutritional Effects in Rats ,

Wheats used for feeding poultry differ considerably in the ratio of soluble to insoluble non-starch polysaccharides (NSP) and apparent metabolizable energy (AME). We have examined effects of whole and white flour from a wheat of low (12.02 MJ/kg of dry matter) and high (14.52 MJ/kg of dry matter) AME in rats fed a cholesterol-free diet. NSP concentrations were higher in whole flour from the low AME wheat but similar in both white flours. In contrast to chickens, food intake and body weight gain of rats were unaffected by diet. Plasma cholesterol concentrations were lower in rats fed whole wheat and low AME wheat. Cecal bile acids and neutral sterol pools were larger in rats fed whole wheat but were unaffected by wheat type. Negative correlations were found between digesta steroid pools and plasma cholesterol, consistent with greater fecal steroid excretion. Cecal digesta was greater in rats fed whole wheat and low AME wheat. Digesta pH was lower in rats fed whole wheat, but there was a significant interaction between wheat and flour type with lower pH in rats fed low AME white flour. Total volatile fatty acids (VFA) and acetate and butyrate pools were larger in rats fed whole wheat than in those fed white flour. Total and individual VFA pools were larger in rats fed low AME flours than in those fed high AME flours, apparently due to greater cecal starch fermentation in the former. Factors affecting wheat AME in chickens affect important metabolic variables in rats and may have similar actions in other species including humans.

Environmentally-Induced Variation in Starch and Non-starch Polysaccharide Content in Wheat

Grain samples from cv. Batten wheat were obtained from experiments conducted in a mobile rainshelter in two seasons, and they were analysed for their contents of starch, arabinoxylan and β-glucan. Grain β-glucan content was less than 0·5% in all samples. However, there was a negative relationship between arabinoxylan content and starch content. This was not due simply to starch dilution because the variation in arabinoxylan content was only 15% of that in starch content. There was also a negative relationship between grain weight and drought, and a positive relationship between amount of arabinoxylan accumulated and drought. These results offer a possible explanation for the observed relationship in wheat between high arabinoxylan and low Apparent Metabolisable Energy for poultry, but contrast with the relationship between drought and β-glucan in barley. Varying levels of nitrogen fertiliser did not affect the relationship between the proportions of arabinoxylan and starch, but, by maintaining photosynthesis longer, late-applied nitrogen in combination with plentiful water supply caused an increase in arabinoxylan weight/grain not seen in other drought-free treatments. We conclude that good irrigation management, especially from anthesis, is crucial for good feed wheat quality.

Sudies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing

1. A significant proportion of wheat cultivars grown in New South Wales had low apparent metabolisable energy (AME) values (< 13.0 MJ/kg dry matter) for growing broilers when determined by the conventional total collection technique. 2. The low AME was due to a reduced starch digestibility and was not improved by grinding the wheat finely or by steam pelleting the diet. 3. Higher AME values were obtained when determinations were made with adult cockerels than with growing broilers when the conventional technique was used. 4. AME values determined using a rapid bioassay technique (Farrell, 1978) with growing broilers or adult cockerels were considerably higher than values determined using the conventional procedure with growing broilers. 5. Inter‐laboratory studies showed that the true metabolisable energy (TME) assay gave reproducible values for individual and blended wheat samples, but that these values were higher than AME values determined by the conventional procedure. Similar TME values were found wi...