O. Adeola

BOARD-INVITED REVIEW: opportunities and challenges in using exogenous enzymes to improve nonruminant animal production.

Diets fed to nonruminant animals are composed mainly of feed ingredients of plant origin. A variety of antinutritional factors such as phytin, nonstarch polysaccharides, and protease inhibitors may be present in these feed ingredients, which could limit nutrients that may be utilized by animals fed such diets. The primary nutrient utilization-limiting effect of phytin arises from the binding of 6 phosphate groups, thus making the P unavailable to the animal. The negative charges allow for formation of insoluble phytin-metal complexes with many divalent cations. Furthermore, phytin and protein can form binary complexes through electrostatic links of its charged phosphate groups with either the free amino group on AA on proteins or via formation of ternary complexes of phytin, Ca(2+), and protein. The form and extent of de novo formation of binary and ternary complexes of phytin and protein are likely to be important variables that influence the effectiveness of nutrient hydrolysis in plant-based diets. Nonstarch polysacharides reduce effective energy and nutrient utilization by nonruminant animals because of a lack of the enzymes needed for breaking down the complex cell wall structure that encapsulate other nutrients. Enzymes are used in nonruminant animal production to promote growth and efficiency of nutrient utilization and reduce nutrient excretion. The enzymes used include those that target phytin and nonstarch polysaccharides. Phytase improves growth and enhances P utilization, but positive effects on other nutrients are not always observed. Nonstarch polysaccharide-hydrolyzing enzymes are less consistent in their effects on growth and nutrient utilization, although they show promise and it is imperative to closely match both types and amounts of nonstarch polysaccharides with appropriate enzyme for beneficial effects. When used together with phytase, nonstarch polysaccharide-hydrolyzing enzymes may increase the accessibility of phytase to phytin encapsulated in cell walls. The future of enzymes in nonruminant animal production is promising and will likely include an understanding of the role of enzyme supplementation in promoting health as well as how enzymes may modulate gene functions. This review is an attempt to summarize current thinking in this area, provide some clarity in nomenclature and mechanisms, and suggest opportunities for expanded exploitation of this unique biotechnology.

Standardized Ileal Amino Acid Digestibility of Plant Feedstuffs in Broiler Chickens and Turkey Poults Using a Nitrogen-Free or Casein Diet

The standardized ileal amino acid digestibility (SIAAD) of 5 plant-based ingredients was determined in 5- and 21-d-old broiler chicks and turkey poults. Two diets (N-free diet, NFD, and a highly digestible protein diet 10% casein, HDP) were fed to determine ileal endogenous amino acid flow, and each was used for endogenous amino acid correction for the plant-based ingredients. The plant-based ingredients evaluated were 2 samples of corn distillers dried grains with solubles (light and dark DDGS), canola meal, corn, and soybean meal. Each diet was fed for 5 d to 6 replicate cages containing 30 or 8 birds, which were sampled on d 5 or 21, respectively. For chicks, apparent ileal amino acid digestibility increased with age for all the feed ingredients. After standardization, SIAAD increased with age when chicks were fed DDGS and corn, but not soybean meal or canola meal. For all the feed ingredients evaluated, SIAAD values for both methods of standardization were not different at d 5. However, the HDP method resulted in greater SIAAD values for most of the amino acids in light DDGS, canola meal, and corn (d 21). In poults, the apparent ileal amino acid digestibility values increased with age for all the feed ingredients except the dark DDGS and canola meal. After standardization, there was no effect of age on amino acid digestibility in all the feed ingredients evaluated, with the exception of corn. Within a particular age (d 5 or 21), both methods of standardization resulted in similar amino acid digestibility values except for corn, for which the SIAAD values were greater (NFD method) in 11 amino acids. Results from this study showed that age-appropriate endogenous amino acid standardization is necessary and, in some cases, results in no age-associated differences in amino acid digestibility. With the exception of corn, standardization of amino acid digestibility with ileal endogenous amino acid flow from birds fed an NFD or HDP did not differ for most plant feedstuffs.

Intestinal mucin dynamics: Response of broiler chicks and White Pekin ducklings to dietary threonine

Mucin dynamics may be particularly sensitive to a Thr deficiency due to the high concentration and structural importance of Thr in the mucin protein backbone. Intestinal mucin secretion, expression of mucin gene (MUC2), and histological characteristics were investigated in male broilers and White Pekin ducklings offered diets containing 3.3, 5.8, or 8.2 g of Thr/kg in 4 studies. Seventy-two birds of each species were fed a standard broiler starter diet from 1 to 14 d of age followed by assignment to 3 dietary treatments in a randomized complete block design for a 7-d feeding trial in experiment 1 (broilers) and experiment 2 (ducklings). The dietary treatments consisted of an isonitrogenous corn-soybean meal-based diet with the addition of crystalline amino acids and graded levels of Thr. Dietary treatments contained 3.3, 5.8, or 8.2 g of Thr/kg. Dietary formulation and experimental design for experiments 3 (broilers) and 4 (ducklings) were similar to experiments 1 and 2 except that birds were fed 3.3 or 8.2 g of Thr/kg for durations of 7 or 14 d. For chicks, increased dietary Thr resulted in higher levels of intestinal crude mucin excretion in experiment 1 (P=0.04) but not in experiment 3, whereas intestinal sialic acid excretion increased in experiment 3 (P=0.02) but not in experiment 1. Furthermore, there was no effect of Thr on intestinal goblet cell density or MUC2 mRNA abundance for broilers. For ducklings, there was an increase in intestinal crude mucin excretion in both experiments (P<0.05) as dietary Thr increased, although there was no effect of Thr on intestinal sialic acid excretion. There was a tendency for an increase in intestinal goblet cell density (cells/microm of villus length; P=0.09) as dietary Thr increased in experiment 2. For experiment 4, intestinal MUC2 mRNA abundance increased (P=0.03) as dietary Thr increased for the 14-d feeding trial but not for the 7-d feeding trial. The data establish a link between dietary Thr and intestinal crude mucin dynamics in chicks for experiment 1 and ducklings for both experiments.

Evaluation of Amino Acid and Energy Utilization in Feedstuff for Swine and Poultry Diets

An accurate feed formulation is essential for optimizing feed efficiency and minimizing feed cost for swine and poultry production. Because energy and amino acid (AA) account for the major cost of swine and poultry diets, a precise determination of the availability of energy and AA in feedstuffs is essential for accurate diet formulations. Therefore, the methodology for determining the availability of energy and AA should be carefully selected. The total collection and index methods are 2 major procedures for estimating the availability of energy and AA in feedstuffs for swine and poultry diets. The total collection method is based on the laborious production of quantitative records of feed intake and output, whereas the index method can avoid the laborious work, but greatly relies on accurate chemical analysis of index compound. The direct method, in which the test feedstuff in a diet is the sole source of the component of interest, is widely used to determine the digestibility of nutritional components in feedstuffs. In some cases, however, it may be necessary to formulate a basal diet and a test diet in which a portion of the basal diet is replaced by the feed ingredient to be tested because of poor palatability and low level of the interested component in the test ingredients. For the digestibility of AA, due to the confounding effect on AA composition of protein in feces by microorganisms in the hind gut, ileal digestibility rather than fecal digestibility has been preferred as the reliable method for estimating AA digestibility. Depending on the contribution of ileal endogenous AA losses in the ileal digestibility calculation, ileal digestibility estimates can be expressed as apparent, standardized, and true ileal digestibility, and are usually determined using the ileal cannulation method for pigs and the slaughter method for poultry. Among these digestibility estimates, the standardized ileal AA digestibility that corrects apparent ileal digestibility for basal endogenous AA losses, provides appropriate information for the formulation of swine and poultry diets. The total quantity of energy in feedstuffs can be partitioned into different components including gross energy (GE), digestible energy (DE), metabolizable energy (ME), and net energy based on the consideration of sequential energy losses during digestion and metabolism from GE in feeds. For swine, the total collection method is suggested for determining DE and ME in feedstuffs whereas for poultry the classical ME assay and the precision-fed method are applicable. Further investigation for the utilization of ME may be conducted by measuring either heat production or energy retention using indirect calorimetry or comparative slaughter method, respectively. This review provides information on the methodology used to determine accurate estimates of AA and energy availability for formulating swine and poultry diets.

True digestibility of phosphorus in canola and soybean meals for growing pigs: Influence of microbial phytase

Two studies with growing pigs were conducted using the regression analysis technique to estimate the true digestibility of P (TPD) in canola (CM) and soybean (SBM) meals, and quantify the effect of microbial phytase on TPD of CM and SBM. In each study, 48 (Exp. 1) or 36 (Exp. 2) 17-kg barrows were assigned to 6 dietary treatments arranged in a 3 x 2 factorial of 3 graded levels of CM (Exp. 1) or SBM (Exp. 2) at 132, 264, or 396 g/kg, and 2 levels of phytase at 0 or 1,000 units/kg. The total collection method was used to calculate P digestibilities. In Exp. 1, phytase supplementation increased (P < 0.01) the apparent total tract digestibility of P in CM with values ranging from 26 to 33% without phytase and from 57 to 62% with supplemental phytase. Regression of digested P against dietary P intake resulted in a decreased (P < 0.05) TPD estimate of 34.3% for the diet without phytase than the 61.4% TPD estimate for diet with added phytase. In Exp. 2, phytase supplementation improved (P < 0.05) apparent total tract P digestibility for SBM with values ranging from 34.3 to 38.6% without phytase and from 68 to 71.2% with supplemental phytase. True P digestibility estimate for SBM without phytase at 40.9% was different (P < 0.05) from that with added phytase at 70.8%. These results indicate a TPD of 34 or 41% in growing pigs fed CM or SBM and demonstrate that the addition of microbial phytase at 1,000 units/kg improves true digestibility of P in CM and SBM by 78 and 73%, respectively.

Comparison of two diet types in the determination of metabolizable energy content of corn distillers dried grains with solubles for broiler chickens by the regression method

The objective of this study was to compare 2 diet types, practical and semi-purified, in the determination of ME and ME(n) contents of corn distillers dried grains with solubles (CDDGS) for broiler chickens by the regression method. Two hundred eighty-eight 14-d-old Ross 308 broiler chickens were assigned to 6 diets consisting of 2 factors in a 2 x 3 factorial arrangement: diet type (practical corn-soybean meal or semi-purified nitrogen-free diet) and CDDGS (0, 300, or 600 g/kg). The birds were fed for 7 d, and there were 6 birds per cage and 8 replicate cages per diet in a randomized complete block design. The CDDGS sample used in the present experiment contained (by analysis) 895 g/kg of DM, 4.811 kcal/g of gross energy, 265.7 g/ kg of CP, 107.6 g/kg of crude fat, 61.3 g/kg of crude fiber, and 41.8 g/kg of ash. There was the expected interaction (P < 0.001) between diet type and CDDGS level in nitrogen retention response of the birds with a decrease as CDDGS level in the practical diet increased but an increase in the semi-purified diet. There were interactions (P < 0.001) between diet type and CD-DGS level in energy retention response, ME, and ME(n). Energy retention linearly decreased (P < 0.0001) from 78.6 to 58.6% as CDDGS increased from 0 to 600 g/kg in the practical diets, whereas the decrease was from 86.8 to 75.4% in the semi-purified diet. The ME and ME(n) (kcal/g) contents of the diets linearly decreased (P < 0.0001) from 3.615 and 3.414 to 2.753 and 2.642, respectively, as CDDGS increased from 0 to 600 g/kg in the practical diets. Corresponding linear decrease (P < 0.0001) values for semi-purified diets were 3.210 and 3.227 to 2.732 and 2.697, respectively. Regression of CDDGS-associated ME intake in kilocalories against grams of CDDGS intake generated the following equations for practical and semi-purified diets respectively: Y = 2.904X + 52, r(2) = 0.987 and Y = 3.013X + 67, r(2) = 0.983. The regression equations for CDDGS-associated ME(n) intake in kilocalories against grams of CD-DGS intake were Y = 2.787X + 46, r(2) = 0.989 and Y = 2.963X + 66, r(2) = 0.983 for practical and semi-purified diets, respectively. Comparison using ANOVA procedures indicated the slope for semi-purified diet type was greater (P < 0.05) than that for the practical diet type. These data indicate that the respective ME and ME(n) values (kcal/g) of the CDDGS sample evaluated were 3.013 and 2.963 when semi-purified nitrogen-free diet was used as the basal diet; and 2.904 and 2.787 when practical corn-soybean meal diet was used as the basal diet. These differences imply that broiler chicken nutritionists should exercise due caution regarding the source of data for ME values of CDDGS when formulating diets containing CDDGS.

Concentration of dietary calcium supplied by calcium carbonate does not affect the apparent total tract digestibility of calcium, but decreases digestibility of phosphorus by growing pigs

A regional experiment was conducted to test the hypothesis that the concentration of dietary Ca does not affect the digestibility of Ca or P in diets fed to growing pigs. Six diets based on corn, potato protein isolate, cornstarch, and soybean oil were formulated. All diets also contained monosodium phosphate, crystalline AA, salt, and a vitamin-micromineral premix. The only difference among the diets was that varying concentrations of calcium carbonate were used to create diets containing 0.33, 0.46, 0.51, 0.67, 0.92, and 1.04% Ca. All diets contained between 0.40 and 0.43% P. Six universities participated in the experiment and each university contributed 2 replicates to the experiment for a total of 12 replicates (initial BW: 23.1 ± 4.4 kg). Pigs were placed in metabolism cages that allowed total, but separate, collection of feces and urine from the pigs. Pigs within each replicate were randomly allotted to the 6 diets and fed experimental diets for 14 d with urine and feces being collected over a 5-d period. Diets, feces, and urine samples were analyzed for Ca and P, and the daily balance, the apparent total tract digestibility (ATTD), and the retention of Ca and P were calculated. Results indicated that intake, fecal excretion, and urinary excretion of Ca increased (linear, P<0.05) as dietary Ca concentration increased. The daily intake of P was not affected by the dietary concentration of Ca, but fecal excretion of P increased (linear, P<0.05) as dietary Ca concentrations increased. In contrast, urinary P output was decreased (linear, P<0.05) as dietary Ca increased. The retention of Ca increased (linear, P<0.05) from 1.73 to 4.60 g/d, whereas the retention of P decreased (linear, P<0.05) from 1.98 to 1.77 g/d as dietary Ca concentrations increased. However, if calculated as a percentage of intake, both Ca and P retention were decreased (linear, P<0.05) as dietary Ca concentration increased (from 55.4 to 46.1% and from 48.4 to 43.5%, respectively). The ATTD of Ca was not affected by the dietary concentration of Ca, but the ATTD of P was decreased (linear, P<0.05) from 56.9 to 46.2% as dietary Ca concentration increased. It is concluded that the dietary concentration of Ca does not affect the ATTD of Ca in calcium carbonate, but increased concentrations of dietary Ca may decrease the ATTD of P in diets based on corn, potato protein isolate, and monosodium phosphate.

Energy utilization and growth performance of broilers receiving diets supplemented with enzymes containing carbohydrase or phytase activity individually or in combination

Energy utilization in broilers as influenced by supplementation of enzymes containing phytase or carbohydrase activities was investigated. Day-old male broilers (480) were allocated to four slaughter groups, thirty broilers in the initial slaughter group and 150 broilers in each of the final slaughter groups on days 7, 14 and 21. Broilers in each of the final slaughter groups were allocated to five treatments in a randomized complete block design, each treatment had six replicate cages of five broilers per replicate cage. The diets were maize-soyabean based with wheat as a source of NSP. The treatments were: (1) positive control that met nutrient requirements of the day-old broiler chick; (2) negative control (NC) deficient in metabolizable energy and P; (3) NC plus phytase added at 1000 FTU/kg; (4) NC plus cocktail of xylanase, amylase and protease (XAP); and (5) NC plus phytase and XAP. Gain and gain:food were depressed (P < 0.05) in the NC diet. Phytase improved (P < 0.05) gain at all ages and gain:food at days 0-14 and days 0-21. There was improvement (P < 0.01) in net energy for production, energy retained as fat and protein from days 0 to 14 and from days 0 to 21 in phytase-supplemented diet compared with the NC diet. Net energy for production was more highly correlated with performance criteria than metabolizable energy and may be a more sensitive energy utilization response criterion to use in evaluating broiler response to enzyme supplementation.

Dietary Fat Content and Fiber Type Modulate Hind Gut Microbial Community and Metabolic Markers in the Pig

Obesity leads to changes in the gut microbial community which contribute to the metabolic dysregulation in obesity. Dietary fat and fiber affect the caloric density of foods. The impact of dietary fat content and fiber type on the microbial community in the hind gut is unknown. Effect of dietary fat level and fiber type on hindgut microbiota and volatile fatty acid (VFA) profiles was investigated. Expression of metabolic marker genes in the gut, adipose tissue and liver was determined. A 2×2 experiment was conducted in pigs fed at two dietary fat levels (5% or 17.5% swine grease) and two fiber types (4% inulin, fermentable fructo-oligosaccharide or 4% solka floc, non-fermentable cellulose). High fat diets (HFD) resulted in a higher (P<0.05) total body weight gain, feed efficiency and back fat accumulation than the low fat diet. Feeding of inulin, but not solka floc, attenuated (P<0.05) the HFD-induced higher body weight gain and fat mass accumulation. Inulin feeding tended to lead to higher total VFA production in the cecum and resulted in a higher (P<0.05) expression of acyl coA oxidase (ACO), a marker of peroxisomal β-oxidation. Inulin feeding also resulted in lower expression of sterol regulatory element binding protein 1c (SREBP-1c), a marker of lipid anabolism. Bacteria community structure characterized by DGGE analysis of PCR amplified 16S rRNA gene fragments showed that inulin feeding resulted in greater bacterial population richness than solka floc feeding. Cluster analysis of pairwise Dice similarity comparisons of the DGGE profiles showed grouping by fiber type but not the level of dietary fat. Canonical correspondence analysis (CCA) of PCR- DGGE profiles showed that inulin feeding negatively correlated with back fat thickness. This study suggests a strong interplay between dietary fat level and fiber type in determining susceptibility to obesity.

Corn distillers dried grains with solubles in diets for growing-finishing pigs: a cooperative study.

An experiment involving 560 crossbred pigs (28 replications of 4 to 6 pigs per pen) was conducted at 9 research stations to assess the effects of dietary concentrations of corn distillers dried grains with solubles (DDGS) on pig performance and belly firmness. Fortified corn-soybean meal diets containing 0, 15, 30, or 45% DDGS were fed in 3 phases from 33 to 121 kg of BW. A common source of DDGS containing 90.1% DM, 26.3% CP, 0.96% Lys, 0.18% Trp, 9.4% crude fat, 34.6% NDF, 0.03% Ca, and 0.86% P was used at each station. Diets were formulated to contain 0.83, 0.70, and 0.58% standardized ileal digestible (SID) Lys during the 3 phases with diets changed at 60 and 91 kg of BW, respectively. The DDGS replaced corn and soybean meal, and up to 0.172% Lys and 0.041% Trp were added to maintain constant SID concentrations of Lys and Trp in each phase. At each station, 2 pigs from each pen in 2 replications were killed and a midline backfat core was obtained for fatty acid analysis and iodine value. In most instances, there were differences among stations (P < 0.01), but the station × treatment interactions were few. Body weight gain was linearly reduced in pigs fed the greater amounts of DDGS (0 to 45%) during phase I (950, 964, 921, and 920 g/d; P < 0.01) and over the entire experimental period (944, 953, 924, and 915 g/d; P = 0.03), but ADFI (2.73, 2.76, 2.68, and 2.70 kg) and G:F (347, 347, 345, and 341 g/kg) were not affected (P = 0.15 and P = 0.33, respectively) during the entire test. Backfat depth was reduced (linear, P < 0.02) by increasing amounts of DDGS (22.5, 22.7, 21.4, and 21.6 mm), but LM area (47.4, 47.4, 46.1, and 45.4 cm(2)) was not affected (P = 0.16) by treatments. Estimated carcass fat-free lean was 51.9, 52.2, 52.4, and 52.1% for 0 to 45% DDGS, respectively (linear, P = 0.06). Flex measures obtained at 6 stations indicated less firm bellies as dietary DDGS increased (lateral flex: 11.9, 8.6, 8.4, and 6.6 cm; linear, P < 0.001; vertical flex: 26.1, 27.4, 28.2, and 28.7 cm; linear, P < 0.003). Saturated and monounsaturated fatty acid concentrations in subcutaneous fat decreased linearly (P < 0.001) and PUFA concentrations increased linearly (P < 0.001) with increasing DDGS in the diet. Iodine values in inner (61.1, 68.2, 74.7, and 82.2) and outer (67.9, 73.6, 79.6, and 85.8) backfat increased linearly (P < 0.001) as DDGS in the diet increased. In this study, feeding diets with 30 or 45% DDGS did not have major effects on growth performance, but resulted in softer bellies. Regression analysis indicated that iodine values increased 4.3 units for every 10 percentage unit inclusion of DDGS in the diet.