Ileal phosphorus digestibility of soybean meal for broiler chickens remains consistent across institutions in a collaborative study regardless of non-phytate phosphorus concentration in the pre-experimental starter diet.

The same experimental protocol was used in 4 institutions to evaluate the impact of non-phytate phosphorus (nPP) concentration in the starter diet on regression method-derived ileal P digestibility of soybean meal (SBM) during the subsequent grower phase. A total of 1,536 Ross 308 male broiler chickens on d 0 post hatching were allotted to 2 pre-experimental starter diets that contained 3.5 or 4.5 g nPP/kg (96 replicate cages per diet, 8 birds per cage) for 18 d. Subsequently, 576 birds from each starter diet were selected and allocated to 3 experimental semi-purified grower diets containing 400, 510, or 620 g SBM/kg (32 replicate cages per diet, 6 birds per cage) for 3 d until collection of ileal digesta. Statistical analysis was conducted as a randomized complete block design with the starter period as whole plot and the grower period as split-plot. The only significant 2-way interaction was between grower diet and experimental institution (P < 0.05) on BW gain and gain to feed ratio. The main effect of institution and grower diet impacted (P < 0.05) feed intake, the digestibility of DM, P, and calcium, and disappearance of inositol hexakisphosphate (InsP6) in the grower diets. Birds fed the 3.5 g nPP/kg starter diet had lower (P < 0.05) BW gain and feed intake during the grower period, but presented higher (P < 0.05) digestibility of P and disappearance of InsP6 compared with the birds that were fed the 4.5 g nPP/kg starter diet. Regression method-derived ileal P digestibility of SBM was determined to be 46 or 42% for the respective 3.5 or 4.5 g nPP/kg pre-experimental starter diet and was not affected by the nPP concentration or by the institution. In conclusion, the experimental protocol used in the current study resulted in similar estimates across multiple institutions and is thus endorsed for future application in studies that aim to expand the database of digestible P content in plant source feed ingredients.

Effect of sodium sources and exogenous phytase supplementation on growth performance, nutrient digestibility, and digesta pH of 21-day-old broilers.

The effect of sodium chloride (NaCl) and NaCl+sodium hydrogen carbonate (NaHCO3) and supplemental phytase (0, 500, 1,000, and 2,000 FTU/kg) on performance, nutrient digestibility and utilization, and digesta pH of male broiler chickens were investigated in a 2 × 4+1 factorial arrangement of treatments in a completely randomized design with 6 replicate cages of 8 birds per replicate. Data were analyzed as a 2 × 4 factorial with contrast between the positive control and the diets containing 0 FTU phytase. Phytase supplementation linearly improved (P < 0.05) average body weigh gain (BWG) and feed intake (d 0-14 and 0-21). Apparent jejunal dry matter (DM) digestibility and digestible energy in birds fed diets containing only NaCl increased (linear and quadratic; P < 0.05) with phytase supplementation whereas quadratic (P < 0.05) effect was observed in birds fed diets containing a combination of NaCl and NaHCO3. Phytase supplementation improved (linear and quadratic; P < 0.05) apparent ileal nitrogen and P digestibility. Apparent utilization of DM, nitrogen, energy, and metabolizable energy increased (linear; P < 0.05) with increasing level of phytase supplementation. Apparent P utilization increased (linear and quadratic; P < 0.05) for both sodium sources but calcium utilization only increased (linear; P < 0.05) with the combination of NaCl and NaHCO3. Bone breaking strength (linear and quadratic) and bone ash (linear) increased (P < 0.05) with phytase supplementation. The combination of NaCl and NaHCO3 resulted in lower (P < 0.05) pH of digesta in the proximal ileum whereas the pH of the digesta in the distal ileum (linear) and the average pH of ileal contents (linear and quadratic) increased (P < 0.05) with phytase supplementation. Results from this study showed that birds' performance and utilization of nutrients and energy by broilers in the presence of phytase was, in general, not influenced by the source of sodium in the diet. Data from this study showed that NaHCO3 can replace a portion of NaCl in the diet of broilers supplemented with phytase without any significant negative effect on performance and that the 2,000 FTU phytase level resulted in better BWG and feed intake as well nutrient and energy utilization.

Response of broiler chickens in the starter and finisher phases to 3 sources of microbial phytase.

A broiler chicken study was conducted for 42 D to evaluate their responses to 3 commercially available microbial phytases. Growth performance, nutrient digestibility, and bone mineralization at days 21 and 42 posthatching were used as parameters of evaluation. The study was a randomized complete block design with 12 treatments, 8 replicate pens, and 25 birds per pen. Treatments included a positive control (PC), a negative control (NC) with crude protein (CP), nonphytate phosphorus (P), and calcium (Ca) reduced by 18, 1.5, and 1.8 g/kg, respectively; the NC + 4 levels of phytase A (250, 500, 750, 1,000 FTU/kg), 3 levels of phytase B (250, 500, 750 FTU/kg), and 3 levels of phytase C (500, 750, 1,000 FTU/kg). Broilers fed the NC diet had reduced (P < 0.05) performance and digestibility measures at days 21 and 42 relative to the PC. All phytase enzymes improved (P < 0.05) BW, gain, feed efficiency, and tibia ash weight and percent. Inclusion of phytase at the highest levels improved (P < 0.05) tibia ash weight by an average of 18.5 and 22% at days 21 and 42, respectively, over the NC. Phytase A linearly improved (P < 0.05) the apparent ileal digestibility (AID) of DM, Ca, P, copper, and sodium at day 21, and the AID of energy, nitrogen, and all amino acid (AA) digestibility at day 42 posthatching. Phytase B linearly (P < 0.05) improved BW gain and feed efficiency of birds at day 21 and quadratically improved (P < 0.05) the AID of nitrogen and all AA in birds at day 42. Supplementation of birds fed the NC with phytase C linearly improved (P < 0.05) the BW gain, feed intake, feed efficiency, and AID of DM, energy, nitrogen, all AA, and all minerals except manganese at day 42. In conclusion, all 3 phytase products improved the growth performance, nutrient and mineral digestibility, and bone mineralization of birds fed diets deficient in nitrogen, Ca, and P similar to or more than birds fed diet adequate in P and CP.

Prevalence of Tinea Capitis among Children in Osogbo, Nigeria, and the Associated Risk Factors.

Tinea capitis is a fungi infection of the scalp that disproportionately affects children in rural and underserved communities in Nigeria. A case-control study was conducted to identify the causative agents and factors that predispose school pupils to tinea capitis in two selected government-owned public primary schools in Osogbo, Southwestern Nigeria. A total of 230 participants were included in the study: 115 cases and 115 controls. Head scrapings were collected from pupils with suspected T. capitis lesions, viewed under Potassium Hydroxide smear microscopy and cultured in Sabouraud's Dextrose Agar (SDA) for characteristic fungal elements. A total of 105 (91%) samples were successfully cultured, of which 56% (59/105) were from male pupils. Tricophyton rubrum (34%), Tricophyton mentagrophyte (31%) and Microsporum canis (18%) were the most prevalent organisms. Other dermatophytes obtained include Microsporum nanuum (3%), Epidermophyton floccusum (6%), Tricophyton verucosum (1%), and Microsporum gypseum (8%). Pupils between the ages of 4 and 7 years had the highest distribution (67%) followed by those between the ages of 8 and 11 years (39%). Playing with animals, the sharing of combs and not bathing with soap were significantly associated with tinea capitis infection (P < 0.05) in each case. This study showed a high prevalence of tinea capitis caused by the identified dermatophytes in the area.

The effect of drying method temperature, collection method, and marker type on apparent ileal amino acid digestibility in 21-day-old broilers fed corn-soybean meal-barley based diet.

For accurate estimation of nutrient digestibility, an ideal drying and sampling method is required to preserve the quality of the digesta. A standard corn-soybean meal (corn-SBM) broiler starter diet was fed from d 0 to 10 before birds were placed on the experimental diets until d 21. One hundred and sixty-eight male Cobb 500 broiler chicks were used to evaluate the effect of two drying methods (freeze-dryer vs. forced air-oven) and two drying temperatures (40 vs. 55°C) (Exp 1), while ninety-six chicks were used to evaluate the effect of flushing and squeezing as well as marker types (titanium vs. chromium) on apparent ileal DM, N, Ca, P, and AA digestibility (Exp 2). There were seven (Exp 1) or eight (Exp 2) replicate cages per treatment with 6 birds/cage. Digesta from the distal two thirds of the ileum was obtained from birds following euthanasia on d 21 by squeezing (Exp 1) and squeezing or flushing (Exp 2). Samples collected were stored in the freezer at -20°C until they were either freeze-dried (FD) or oven-dried (OD) at 40 or 55°C. There were no interactions between the drying methods and drying temperatures (Exp 1) on apparent ileal DM, N, and AA digestibility. Met had the highest (92.3%) while Cys had the lowest (73.8%) digestibility value. In Exp 2, no interaction between sampling methods and marker types was observed. The effect of sampling methods was not significant except for Arg and Met where squeezing resulted in higher (P < 0.05) digestibility values. Furthermore, apparent ileal His, Ile, Cys, Ser, and Tyr digestibility tended to be higher (P < 0.1) in squeezed digesta compared to the flushed digesta. Results from these studies showed that OD ileal digesta at 40 or 55°C had no negative effect on apparent ileal AA digestibility. Likewise, marker type did not influence apparent ileal AA digestibility values.

Investigating the effect of dietary calcium levels on ileal endogenous amino acid losses and standardized ileal amino acid digestibility in broilers and laying hens.

Two studies were conducted to evaluate the effect of dietary Ca levels (low, 1% and high, 3%) on ileal endogenous amino acid losses (IEAAL) and standardized ileal amino acid digestibility (SIAAD) in broilers (BR) and laying hens (LH) fed nitrogen-free diets (NFD) and distiller's dried grain with solubles (DDGS)-based diets. A total of 384 male Cobb 500 BR and 288 LH were used in a completely randomized design (CRD) with 16 (BR) or 12 (LH) replicate cages with 6 birds/replicate. IEAAL and apparent ileal digestibility (AID) of AA were analyzed using the GLM procedure of SAS appropriate for a CRD while SIAAD values were analyzed using the GLM procedure of SAS appropriate for a 2 × 2 factorial arrangement of treatments. For BR, IEAAL and N losses (mg/kg of dry matter intake, DMI) were higher (P < 0.05) when NFD with high Ca level was fed (total AA was 39%, N was 35% higher). For most of the AA, AID was higher (P < 0.05) in BR fed DDGS-based diet with high Ca level. High dietary Ca resulted in higher (P < 0.05) SIAAD for all the AA except for Arg, Lys, Met, Cys, and Tyr. For LH, AID of AA was higher (P < 0.05) for the DDGS diet with high Ca level in 13 of the 18 AA evaluated. There was interaction (P < 0.05) between diet Ca level and correction method on LH SIAAD values for Thr, Asp, Gly, and Ser. The SIAAD values for 8 AA were higher (P < 0.05) in birds on high Ca DDGS diet. Correction with low Ca NFD resulted in higher (P < 0.05) SIAAD values for all the AA. Result from this study showed that high Ca increased total IEAAL in BR by 39% but decreased same by 27% in LH. Finally, SIAAD values were increased in BR fed high Ca DDGS-based diet while SIAAD value in LH was lower when correction was done using values from high Ca-NFD fed birds.

Examining the effect of dietary electrolyte balance, energy source, and length of feeding of nitrogen-free diets on ileal endogenous amino acid losses in broilers.

The effect of dietary electrolyte balance (DEB), energy source (ES), and length of feeding of nitrogen-free diet (NFD) on ileal endogenous amino acid (EAA) loss in mg/kg dry matter intake (DMI) was evaluated in broiler chickens. In Experiment 1, 720 chickens consisting of 15 replicate cages with 6 chickens/replicate were used. Treatments were arranged in a 2 × 2 × 2 factorial and consisted of 4 NFD with 2 levels (low or high) of DEB and 2 ES [corn starch (CS) or dextrose (DX)], and 2 sampling time-points (diets were fed for either 72 h (d 16 to 19) or 120 h (d 16 to 21). Experiment 2 used 360 chickens in a 2 × 2 factorial arrangement of treatments with 2 levels (low or high) of DEB and 2 ES (CS or DX). Diets were fed for 72 h (d 18 to 21). All birds had access to feed and water on an ad libitum basis. Data were analyzed using the GLM procedure of SAS appropriate for a completely randomized design for a factorial arrangement of treatments. For Experiment 1, there were interactions (P < 0.05) between the 3 main factors for nitrogen and all the AA except Trp. Broilers that were fed DX-based NFD with high DEB for 72 h had the highest (P < 0.05) EAA losses. In Experiment 2, there was no interaction between DEB and ES except for His and Lys. When ileal EAA losses from birds fed the low DEB, CS-based NFD were used to standardize apparent ileal digestibility values from a previous study, there was no effect of length of feeding on standardized ileal AA digestibility values. In conclusion, DX-based NFD with high DEB increased endogenous AA loses. Despite differences in ileal EAA losses from CS-based NFD, standardized ileal AA digestibility values were not influenced by the length of feeding of NFD. Based on the results from these studies, NFD could be fed for 72 h without influencing SIAAD values.

Investigation of the effect of coccidial vaccine challenge on apparent and standardized ileal amino acid digestibility in grower and finisher broilers and its evaluation in 21-day-old broilers.

The effect of coccidial vaccine challenge (CVC, Coccivac(®)B; challenged, CHA; or unchallenged, NCH) on ileal endogenous amino acid (IEAA) losses and standardized ileal AA digestibility (SIAAD) in 21- and 42-day-old broilers fed a corn-soybean meal-dried distillers' grains with solubles-poultry by-product meal-based diet (Expt. 1) and the effect of supplemental AA in ameliorating the effect of CVC (Expt. 2) were evaluated. Expt. 1 was designed as a 2 (d 21 or 42) x 2 (NCH or CHA) factorial arrangement of treatments with 8 replicates in a complete randomized design. The CVC birds were gavaged with 12 x coccidial vaccine on d 15 and 36 and were sampled on 6 d post challenge. SIAAD was determined by correcting apparent ileal AA digestibility for IEAA losses. Feed intake (FI) and BW gain were higher (P ≤ 0.05) in 21-day-old NCH birds compared to the 21-day-old CHA birds while 42-day-old birds had higher FI and BW gain than 21-day-old NCH and CHA birds. Ileal endogenous nitrogen loss was higher (P ≤ 0.05) in 42-day-old CHA birds compared to 42-day-old NCH birds. Apparent ileal AA digestibility in 21-day-old CHA birds was lower (P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. SIAAD in 21-day-old CHA birds was lower (indispensable AA = 15.2 and dispensable AA = 17.8%-unit; P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. Apparent ileal digestibility and total tract utilization of DM, N, and energy were not different between d 21 NCH and d 42 NCH and CHA birds but higher (P ≤ 0.05) than for d 21 CHA birds. Supplemental AA restored feed efficiency, but not BW gain, to that of the positive control (0.715 vs. 0.737). Results from Expt.1 showed that CVC significantly influenced ileal AA digestibility in 21- but not in 42-day-old birds. Expt. 2 showed that consideration of SIAAD in feed formulation may benefit feed efficiency.

Standardized Ileal Amino Acid Digestibility of Corn, Corn Distillers' Dried Grains with Solubles, Wheat Middlings, and Bakery By-Products in Broilers and Laying Hens.

Standardized ileal amino acid digestibility (SIAAD) of 5 samples of corn distillers dried grain with solubles (DDGS), 5 samples of bakery by-products (BBP), 3 samples of corn, and 1 sample of wheat middlings (WM) were evaluated in broilers and laying hens. Diets containing each of the 14 feed ingredients were evaluated in 21 day-old broiler chickens. The DDGS and BBP containing diets were fed to 30-week-old laying hens, while corn and wheat middling were evaluated in 50-week-old laying hens. All the diets were semi-purified with each feed ingredient being the only source of amino acid (AA). To obtain SIAAD values, apparent ileal AA digestibility was corrected for basal ileal endogenous AA losses using values generated from broilers and laying hens fed a nitrogen-free diet. Ileal crude protein digestibility for the 5 DDGS samples was higher (P < 0.05) in broilers than in laying hens. Broilers had higher SIAAD for DDGS 2, 3, 4, and 5 while there was no difference for DDGS 1 except for 4 AA where broilers had higher (P < 0.05) SIAAD values. Standardized ileal AA digestibility values for broilers were higher (P < 0.05) for BBP 1 and 4. Ileal CP digestibility for corn 1 was higher (P < 0.05) for broilers compared to laying hens, and SIAAD values for the 16 AA (9 indispensable and 7 dispensable) evaluated in this study were higher (P < 0.05) in broilers. Broilers had higher (P < 0.05) SIAAD values for 4 (histidine, leucine, phenylalanine, and valine) and 6 (histidine, leucine, methionine, phenylalanine, threonine, and valine) indispensable and 3 (cysteine, glutamic acid, and proline) and 4 (cysteine, glutamic acid, proline, and serine) dispensable AA for corn 2 and corn 3, respectively. No difference in SIAAD between broilers and laying hens was observed for WM. Results from this study confirm that high variability in digestibility exists between different samples of DDGS. Differences in SIAAD between broilers and laying hens were observed in some samples of DDGS and BBP.

The efficacy of a new 6-phytase obtained from Buttiauxella spp. expressed in Trichoderma reesei on digestibility of amino acids, energy, and nutrients in pigs fed a diet based on corn, soybean meal, wheat middlings, and corn distillers' dried grains with solubles.

Sixteen cannulated pigs were used to evaluate the effect of a new 6-phytase derived from Buttiauxella spp. and expressed in Trichoderma reesei on apparent ileal digestibility (AID) of AA and apparent total tract digestibility (ATTD) of DM, N, Ca, P, Na, Mg, K, Cl, and energy. Pigs were fed 4 diets for 2 periods in a crossover design. Within each period, there were 4 blocks of 4 pigs per block with each diet represented within each block. The average initial BW in periods 1 and 2 were 22 and 30 kg, respectively. Each period lasted 9 d with fecal collection on d 5 and 6 and a 12-h ileal digesta collection on d 7, 8, and 9. Pigs received a daily feed allowance of approximately 4.5% of their BW. The experimental diets were based on corn, soybean meal, wheat middlings, and corn distillers dried grain with solubles. Phytase was added at 0; 500; 1,000; or 2,000 phytase units/kg of diet to a basal diet that contained 205, 15, 5.4, and 10 g of CP, Lys, total P (1.6 g of nonphytate P), and Ca/kg diet, respectively. The addition of phytase improved (P < 0.05) AID of DM, N, Ca, and P. Increasing phytase supplementation linearly and quadratically increased (P < 0.05) AID of P and Ca, respectively, with AID of Ca showing a tendency for a linear increase (P = 0.053). Phytase supplementation of the basal diet improved (P < 0.05) AID of P from 46 to 62%. Phytase supplementation increased (P < 0.05) ATTD of DM, N, Ca, P, Mg, K, and energy. Contrasts showed that phytase supplementation of the basal diet increased (P < 0.05) AID for 8 indispensable AA (Arg, His, Ile, Leu, Lys, Phe, Thr, and Val), 6 dispensable AA (Ala, Asp, Cys, Glu, Ser, and Tyr), as well as for total AA. Furthermore, phytase supplementation to the basal diet showed a tendency (P < 0.10) to increase ileal digestibility of Gly. Ileal digestibility of Met, Trp, and Pro were not affected by phytase supplementation. Increasing the level of phytase supplementation resulted in linear increases (P < 0.05) in AID of 6 indispensable AA (Arg, Ile, Leu, Lys, Phe, and Val) and 1 dispensable AA (Asp) with 4 AA (His, Cys, Glu, and Tyr) showing a tendency for linear increase (P < 0.10) in AID of AA. The results from this study showed that in addition to increasing P and Ca utilization, the new Buttiauxella 6-phytase expressed in Trichoderma reesei enhanced ileal digestibility of N and several AA in growing pigs in a dose-dependent manner.

Dietary electrolyte balance influences ileal endogenous amino acid losses in broiler chickens.

The objective of the current study was to determine the effect of nitrogen-free diets formulated with 2 ratios of corn starch and dextrose and 2 levels of dietary electrolyte balance (DEB; calculated as Na + K - Cl(-), in mEq/kg of diet) on ileal endogenous amino acid (EAA) losses in 48-d-old broiler chickens. On d 43, 240 broiler chickens were allotted to 4 dietary treatments with 6 replicate cages per diet in a completely randomized design. Each experimental diet was fed for 5 d (d 43-48). All diets were free of nitrogen with 2 ratios of corn starch-to-dextrose (0.31 and 1.04) and 2 levels of DEB (108 and 219 mEq/kg of diet). Final BW and BW loss between birds fed the 2 corn starch-to-dextrose ratios and between birds fed 2 levels of DEB were not different (P > 0.05). Birds fed the diet containing a high level of DEB consumed less (P < 0.05) feed than birds on the low-DEB diet. Birds on the high-corn starch-to-dextrose (1.04) diet showed a tendency for higher (P = 0.08) feed intake. High dietary dextrose level (corn starch-to-dextrose ratio of 0.31) resulted in higher (P < 0.05) ileal DM and energy digestibility. A high level of DEB resulted in higher (P < 0.05) ileal endogenous nitrogen loss. Arginine, Ile, Leu, Phe, Val, Ala, Glu, Gly, Pro, and Tyr secretion into the gut increased (P ≤ 0.05) with an increasing level of DEB. Endogenous His, Lys, Thr, Asp, Cys, and Ser showed a tendency for increased (P ≤ 0.1) losses with a high level of DEB. Mean ileal EAA losses for the indispensable and dispensable amino acids for the low-DEB diet were 81 and 82%, respectively, that of the birds fed the high-DEB diet. The 4 amino acids with the lowest endogenous flow were Met, His, Tyr, and Cys, whereas the highest endogenous flow was found in Glu, Asp, Val, and Leu. Data from the current study showed that EAA losses in the ileum of broiler chickens are significantly affected by DEB, but not by the ratio of corn starch to dextrose.

Standardized ileal amino acid digestibility of meat and bone meal and soybean meal in laying hens and broilers.

The objective of this study was to determine the standardized ileal amino acid digestibility (SIAAD) of 7 meat and bone meal (MBM) and 3 soybean meal (SBM) samples in broilers (Ross 708) and laying hens (Hy-line W36). All 10 feed ingredients were evaluated in 21-d-old broiler chickens and 30- or 50-wk-old laying hens. Standardization was accomplished by correcting for basal ileal endogenous amino acid losses using a nitrogen-free diet. Broilers were reared in cages from d 0 to 16 on a standard broiler starter diet adequate in all nutrients and energy; thereafter, they were allotted to treatments using a randomized complete design with 6 replicate cages of 8 birds each. For the laying hens, 6 replicate cages of 6 birds each (542 cm(2)/bird) were used. Each treatment diet, which was fed for 5 d, was semipurified, with MBM or SBM being the sole source of amino acids in each diet. Ileal endogenous amino acid losses were not different between broilers and the 2 groups of laying hens. Meat and bone meal from different locations varied widely in digestibility. Broilers had higher (P < 0.05) SIAAD in 4 of the 7 MBM samples. In 2 of the 3 SBM samples, broilers had higher (P < 0.05) SIAAD for most of the nonessential amino acids. Generally, hens had 6.4 and 7.7% units less Met and Lys digestibility of all MBM samples after standardization. Dry matter digestibility values of the SBM samples were higher (P < 0.05) in broilers. Likewise, broilers had 4.1 and 1.5% units more Met and Lys digestibility of all the SBM samples evaluated compared with those from laying hens. The results of these experiments suggest that differences exist in the digestive capabilities of laying hens and broilers, which indicates that species-specific nutrient digestibility values or adjustments may be needed.

Ileal endogenous amino acid losses: response of broiler chickens to fiber and mild coccidial vaccine challenge.

The effects of mild coccidial vaccine (5× dose) challenge and fiber levels on ileal endogenous amino acid (EAA) losses was determined in 26-d-old broiler chickens using the regression method. Birds were fed semipurified diets containing 3 levels of casein (40, 80, or 120 g/kg of diet) as the only source of dietary protein at 2 levels of fiber (purified cellulose at 25 or 75 g/kg of diet). One half of the experimental birds were gavaged with coccidial vaccine on d 20. The 3 levels of casein were used to determine EAA losses for each replicate cage of birds. The design of the study was a randomized complete block employing a factorial arrangement of treatments with 2 levels of coccidial challenge (control or unchallenged, and challenged) and 2 levels of fiber, with 6 replicate cages per treatment and 8 birds per cage. Birds were killed on d 26 and contents from the entire ileum were flushed with distilled water and stored at -20°C until processed. Ileal EAA losses were determined from the ordinate intercept, at zero amino acid (AA) intake, of the regression of ileal digesta AA concentration in milligrams per kilogram of DM intake against dietary AA intake in milligrams per kilogram of DM. The effect of fiber level on EAA losses, expressed in milligrams per kilogram of DM intake, were higher (P < 0.05) for most of the AA in birds fed 25 g of fiber/kg of diet. Coccidial vaccine challenge decreased (P < 0.05) EAA losses for 8 of the 18 AA. A significant interaction between fiber level and coccidial vaccine challenge was obtained for all AA except His and Lys. Coccidial vaccine challenge resulted in increased (P < 0.05) NaPi-IIb expression. The results suggest that ileal EAA loss is higher in challenged birds fed the diet containing 25 g of fiber/kg of diet. Changes in EAA losses as a result of dietary fiber level and coccidial infection are important in amino acid nutrition of the broiler chicken.

Factors affecting endogenous amino acid flow in chickens and the need for consistency in methodology.

Accurate estimation of ileal endogenous amino acid (EAA) losses is important when formulating diets on a standardized ileal digestible amino acid basis. In addition to the undigested and unabsorbed amino acids of dietary origin, amino acids of endogenous origin, which can be basal or diet specific, are found in digesta. The improvement in the techniques used in amino acid analysis as well as a shift from sampling excreta to ileal digesta has resulted in more accurate amino acid digestibility coefficients. Despite this, however, it is important to determine the amino acids in the digesta that are of endogenous origin. Although the need for standardization and its associated advantages is still subject to debate, it is important to evaluate how values from various methodologies compare. Several methods have been used to estimate ileal EAA flow. The classical methods, including the regression method, the use of nitrogen-free diet (NFD), and the fasted cecectomized rooster method, are the most widely used. The criticisms with the last 2 methods are that birds are not in a normal physiological state and the ileal EAA flow is, therefore, underestimated. Different methods have resulted in different endogenous flow estimates, with the NFD method having the lowest values when compared with flows from the regression and highly digestible protein methods. In addition to the influence of methods on ileal EAA flows, the influence of the age of the birds on flow is important. Data on EAA losses are copious in the literature; however, variation in data across and within laboratories calls for investigation of factors contributing to the variation. This review compares results from different methods and examines the issue of repeatability and consistency of EAA losses data from different laboratories. Finally, composition of an NFD for estimating EAA losses is proposed.

Comparison of amino acid digestibility of feed ingredients in broilers, laying hens and caecectomised roosters.

1. This study determined the effect of bird type (broilers, laying hens, or caecectomised roosters) on amino acid digestibility of feedstuffs from 5 plant sources and one animal source. 2. The standardised amino acid digestibility (SAAD) were obtained by correcting apparent ileal amino acid digestibility (AIAAD) values for basal ileal endogenous amino acid (EAA) flow obtained by feeding a N-free diet (NFD) to broilers and laying hens or from fasted EAA flow from caecectomised roosters. 3. The apparent total amino acid (TAA) digestibilities did not differ between broilers and roosters for three of the 6 feed ingredients. 4. Broilers had higher apparent total amino acid (TAA) digestibility than laying hens and roosters when fed on the maize diet (canola meal, maize, and soybean meal). 5. The apparent TAA digestibilities were similar across bird types for the dark distillers' dried grain with solubles, but the apparent lysine digestibility was much lower in the caecectomised roosters (15%) than the broilers (49%) and laying hens (43%). 6. The standardised TAA digestibility values in roosters were higher than in broilers for three of the 6 feed ingredients (canola meal, soybean meal, or meat and bone meal). 7. There were no differences between broilers and roosters, however, in the standardised TAA digestibility values for maize, dark and light DDGS. 8. The standardised TAA digestibility values for laying hens were lower for maize, higher for meat and bone meal, but no different for the remaining ingredients when compared with broilers. 9. The results from this study showed that both the apparent and standardised amino acid digestibility values in caecectomised roosters, laying hens, and broilers ingredients are similar for some, but not all, feed ingredients. 10. Nutritionists should, therefore, be cautious about using digestibility coefficients obtained by different methodologies as values may differ.

Comparison of endogenous amino acid flow in broilers, laying hens and caecectomised roosters.

1. This study was conducted to determine and compare endogenous amino acid (EAA) flow in broilers, laying hens, and caecectomised roosters fed on either a nitrogen-free diet (NFD) or a highly digestible protein diet (HDP). 2. Also, the EAA flows using three methods (fasted, NFD, or HDP) in precision-fed caecectomised roosters were compared. 3. EAA flow did not differ between broilers and laying hens on either the NFD or HDP diets. 4. Endogenous amino acid flow in caecectomised roosters was 3.5-12-fold higher than for broilers and laying hens for both methods (NFD and HDP) of estimation. 5. When caecectomised roosters were fasted or precision-fed (NFD or HDP), there was no difference in EAA flow between the NFD- or HDP-fed birds. 6. However, flows from fasted roosters were lower than from roosters receiving either the NFD or HDP diet. 7. Results from this study showed that EAA flow is method-dependent. Total amino acid flow from fasted birds was 31% less than when a NFD was fed to caecectomised roosters.

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.

Endogenous amino acid flow in broiler chicks is affected by the age of birds and method of estimation.

The determination of ileal endogenous amino acid (IEAA) and total amino acid (TAA) concentrations is critical to standardizing amino acid digestibility coefficients. The IEAA and TAA flow in broiler chicks was measured on d 5, 15, and 21 at 2 geographical locations. Chicks were fed a nitrogen-free diet (NFD) or graded levels of casein (50, 100, or 150 g/kg of diet), which were assumed to be highly digestible. The IEAA and TAA flow (mg/kg of DM intake) on d 5 in chicks fed the NFD was higher (P < 0.05; Met = 154, Thr = 539) than values for d 15 (Met = 51, Thr = 274) and d 21 (Met = 50, Thr = 274). A comparison of the regression and NFD analyses showed higher (P < 0.05) flows on d 5 for those birds fed the NFD diet, with no differences between methods on d 15 and 21, with the exception of Lys, Met, and Glu (d 21). At all 3 ages evaluated, there was a linear increase (P < 0.05) in IEAA and TAA flows with increasing level of dietary casein. There was a decrease in IEAA and TAA flows that stabilized between d 15 and 21. The result suggests that the NFD and the regression method will give similar results on d 15 and 21. These observations also suggest that the relatively low apparent amino acid digestibility coefficients for broiler chicks at a younger age may be the result of a significantly high level of endogenous amino acid flow.

Standardized ileal amino acid digestibility of meat and bone meal from different sources in broiler chicks and turkey poults with a nitrogen-free or casein diet.

The aim of this study was to determine the effect of the standardization method and age on standardized ileal amino acid digestibility (SIAAD) of 4 meat and bone meal (MBM) samples in broiler chicks and turkey poults. The SIAAD were obtained by correcting apparent ileal digestibility (AID) values for basal ileal endogenous amino acid flow obtained from chicks and poults fed a N-free diet or a highly digestible protein diet (HDP; 100 g of casein/kg of diet). Four diets were formulated to contain 20% CP by using MBM as the only source of CP. Each diet was fed to 6 replicate cages of 30 or 8 birds/cage at 5 and 21 d, respectively, for 5 d. With the exception of all-beef MBM, chick AID values on d 21 were higher (P < 0.05) than on d 5. In poults, however, AID was not different between the 2 ages, with the exception of His, which was higher (P < 0.05) at d 21. There was no difference between methods on SIAAD on d 5 or 21 for all 4 MBM samples in either species. There was no effect of the method of standardization on SIAAD at either age for most amino acids. For chicks, however, standardization of the all-beef MBM sample with HDP resulted in higher (P < 0.05) SIAAD values for most of the amino acids (d 5). In poults at d 5, however, the SIAAD for most of the amino acids in the blended MBM were higher (P < 0.05) with HDP correction. The CV in SIAAD in chicks between the 2 methods of standardization was higher on d 5 (8.1%) relative to d 21 (5.0%) for all treatments. In poults, greater variability was observed on d 21 (8.2%) relative to d 5 (6.7%). Results from this study showed that at d 21, SI-AAD with either the N-free or the HDP diet resulted in similar digestibility values.

Effect of age and method on ileal endogenous amino acid flow in turkey poults.

Ileal endogenous amino acid (IEAA) flow in turkey poults was determined at 2 experimental locations on d 5, 15, and 21 posthatch using 3 methods, namely a N-free diet (NFD), a highly digestible protein (casein), and the regression method, obtained by regressing IEAA flow against dietary casein levels. The diets were semipurified and contained 0, 50, 100, or 150 g of casein/kg of diet as the sole source of dietary protein. Each diet was fed for 5 d to 6 replicate cages of 30 (d 5), 10 (d 15), or 8 (d 21) birds per cage. There was no interaction between locations and age or locations and diet, so the data from both locations were pooled. Ileal endogenous amino acid flow on d 5 (NFD method) was higher (P < 0.05) than on d 15 or 21. Ileal endogenous amino acid flow estimated from the NFD and the regression methods was different on d 5 (P < 0.05), but there were no differences in IEAA flow for most of the amino acids on d 15 and 21. Increasing the level of casein resulted in a linear (P < 0.05) increase in IEAA flow. The amino acids with the lowest flow were Trp and Met, whereas Glu had the greatest flow. The results obtained from this study indicate that data generated across laboratories were repeatable. The results also suggest that about twice as much amino acids of endogenous origin are found in the digesta of poults on d 5 relative to d 21. Also, as poults age, there is a decrease in IEAA flow from d 5 to 15, but flows from d 15 to 21 are not different. These observations suggest that apparent digestibility coefficients for poults on d 5 and d 15 or 21 could be significantly influenced by the level of endogenous amino acids, more so on d 5.