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SUMMARY: In the present experiment, a Thr fermentation product (FP) (75% minimum digestible Thr) was evaluated as a replacement for crystalline L-Thr (98.5% minimum digestible Thr) as a source of digestible Thr and other nutrients to support broiler performance (0–48 d) and processing characteristics. Five phase-fed diets included 1) a positive control (PC) diet containing L-Met, L-Lys•HCl, and L-Thr, 2) a reduced protein control (RPC) diet with added L-Val, L-Ile, and L-Arg, 3) a negative control (NC) identical to the RPC except that cellulose was added at the expense of L-Thr, 4) a RPC diet with Thr-FP used in place of L-Thr with only accounting for digestible Thr and energy contributions of the FP (TFP), and 5) a RPC diet with Thr-FP used in place of L-Thr and accounting for the full nutrient matrix of the FP (TFP-FM). Overall, broilers fed the RPC diet had similar growth performance compared to birds fed the PC diet, whereas broilers fed the NC diet had reduced BW gain and increased FCR compared to the RPC-fed birds. Birds fed either the TFP or TFP-FM diet had similar growth performance to the RPC-fed birds. At processing, broilers fed the RPC diet had similar parts yields, excluding wings, to the PC group. Parts yields for the Thr-FP and NC groups were similar to the RPC group. These data confirmed the importance of adequate dietary Thr concentration in maximizing broiler performance and that Thr provided by the Thr-FP supported equivalent performance to L-Thr.

Summary: Modern broiler diets may contain excess levels of leucine due to the increased level of this amino acid in cereal grains. Excessive levels of leucine have previously been shown to negatively influence broiler performance due to branched-chain amino acid antagonism. Therefore, 2 leucine titrations were conducted in male and female Cobb 500 broilers. Low and high leucine diets were formulated to contain leucine to lysine ratios of 115 and 170, respectively. These diets were subsequently blended to produce 6 experimental diets containing leucine to lysine ratios of: 115, 126, 137, 148, 159, and 170. Pelleted diets were fed to 8 replicate pens of male and female broilers during a 15 to 32-day period. A subset of broilers was processed on day 33 for determination of carcass traits. Male broilers did not respond to excessive levels of dietary leucine. Increased leucine resulted in a positive quadratic response (P = 0.020) in feed intake for female broilers. The overall lack of a response of increased dietary leucine on male and female broilers indicate that industry levels of isoleucine and valine are likely of a sufficient level to overcome the effects of leucine excess.

SUMMARY: Reductions in dietary crude protein have potentially allowed for the occurrence of branched chain amino acid antagonism which can negatively influence live performance and carcass traits. Therefore, 2 factorial studies were conducted with the first experiment evaluating valine and leucine interactions during a 32 to 45 d finisher period, while the second experiment evaluated valine and isoleucine interactions during a 39 to 52 d withdrawal period. Valine, leucine, nor their subsequent interaction influenced broiler live performance or carcass traits in Experiment 1. However, a valine × leucine interaction was observed for average woody breast score and occurrence of scores of 1 and 2. This interaction demonstrated that leucine does not increase woody breast in birds fed diets with a valine to lysine ratio of 77, but interaction differences for woody breast severity varied among valine and leucine ratios to lysine. In the second experiment, increasing valine marginally increased feed intake, while isoleucine influenced tender yield. No valine × isoleucine interactions were observed. Within the confines of the levels used in the current study, manipulation of dietary branched-chain amino acid levels had little influence on live performance or carcass traits during the tested growout periods. The occurrence of a valine × leucine interaction on the incidence and severity of woody breast is perplexing and requires more investigation to determine if a successful mitigation strategy could be developed.

SUMMARY: Branched-chain amino acid requirements have traditionally been determined using dose-response titrations without accounting for the influence of branched-chain amino acid antagonism. As recent data has indicated that inherent levels of the non-tested amino acid may influence response curves in diets mimicking industry, these methods may result in over or under estimation of requirement values. Therefore, an experiment was conducted to determine if dietary levels of isoleucine and leucine influence 29 to 42 day valine needs through the implementation of a 5 × 2 × 2 factorial design. Twenty diets were fed to 7 replicate pens of 12 broilers. Body weight gain, feed intake, and FCR were determined for the 29 to 42 day period, and carcass traits were assessed on day 44. Valine × isoleucine and valine × leucine interactions were observed for BW gain and total breast yield (P < 0.10). Body weight gain requirements ranged from 73 to 81 Val/Lys, whereas responses for total breast yield were generally negative. A 3 way interaction was observed for FCR in which requirements varied from 75 to 82 Val/Lys. These interactions indicate that formulation strategies based on previous data concerning valine or isoleucine may not produce the desired response in Cobb MV × 500 broilers and that the branched-chain amino acids should be considered as a whole and not individually.

SUMMARY: Recent research into the branched-chain amino acids has indicated that broiler responses to dietary isoleucine may vary from classic data. Current isoleucine data has focused on male broilers leaving a gap in the literature for female data. An experiment was conducted to determine the isoleucine requirements for a 22 to 42 day finisher period in Cobb MV × 500 female broilers. A basal diet was formulated to contain dietary isoleucine, valine, and leucine to lysine ratios of 56, 78, and 135, respectively, and graded amounts of L-isoleucine were added to achieve isoleucine to lysine ratios of 56, 59, 62, 65, 68, 71, and 74. An additional external control diet was formulated with isoleucine, valine, and leucine to lysine ratios of 65, 72, and 135, respectively, to which aliquots of L-isoleucine, L-valine, and L-leucine were added to create diets containing isoleucine, valine, and leucine ratios ranging from 65 to 71, 72 to 81, and 135 to 175, respectively. Digestible lysine was maintained at 1.10 percent. Linear responses were observed for day 42 BW, BW gain, feed conversion, fat pad yield, and breast yield. No other significant responses were observed for the isoleucine titrations. Comparison among the external controls generated a significant decrease in fat pad yield when all 3 branched-chain amino acids were increased compared to birds fed the 65 isoleucine to lysine diet. The linear response observed for both feed conversion and breast meat yield indicate that optimal isoleucine levels may be beyond the 74 isoleucine to lysine ratio tested in this study.

Summary: The use of direct-fed microorganisms (DFM) is an important alternative to antibiotic growth promoters (AGP) for improving growth and managing disease in poultry production. We investigated the administration of 2 multistrain Bacillus cultures administered as DFM on growth performance and mortality of broiler chickens reared under performance-reducing stress challenge. The first experiment evaluated the dose response of the growth of broiler chickens to the administration of 3 increasing concentrations of direct-fed Bacillus culture A (DFM A). Administration of the low dose of DFM A improved starter, grower, and cumulative FCR of broiler chickens as compared with an untreated control with no further benefit being observed at higher doses. The second experiment compared the administration of the low dose of DFM A with a second multistrain direct-fed Bacillus culture (DFM B) administered at a dose demonstrated previously to improve growth at a level similar to an AGP. The overall elevated level of mortality observed in this experiment was reduced by DFM A administration when compared with an untreated control over the grower phase and cumulatively. Additionally, when compared with an untreated control, DFM A administration reduced starter FCR, whereas DFM B administration reduced grower FCR. Overall, the results of our study suggest administration of multistrain Bacillus spp. cultures as DFM may be used as a potentially important alternative to AGP for improving growth and managing disease in poultry production.

Summary: The inclusion of L-Val and L-Ile is progressively becoming an economically feasible strategy to reduce the dietary CP content of broiler diets. In the current experiment, the influence of supplementing the feed-grade branched chain amino acids (BCAA) Val and Ile was evaluated in corn and soybean meal–based (CSBM) diets, with or without the inclusion of either peanut meal (PM) or an animal protein blend (APB), on broiler growth performance (0–48 D), processing characteristics, and incidence of pododermatitis and litter characteristics. Supplementation of BCAA reduced analyzed CP by an average of 1.62 percentage units across 4 feeding phases. Overall (0–48 D), broiler body weight gain and FCR were unaffected when fed supplemental BCAA; however, feed intake was increased for those supplemented with BCAA. Overall growth performance was similar when including either PM or APB in CSBM diets. At processing, broilers fed BCAA diets had increased relative and absolute breast fillets and total white meat weights, as well as heavier fat pad weights. Nitrogen excretion was reduced when BCAA were supplemented, but no differences were observed for footpad dermatitis (FPD) lesion scores. Interestingly, APB supplementation did not impact litter moisture or nitrogen but improved FPD scores compared to birds fed CSBM, with PM-fed birds having intermediate FPD scores. In conclusion, these data indicate that BCAA inclusion can support CP reductions while maintaining growth performance, improving breast fillet yield, and reducing nitrogen excretion in broilers reared to market ages.

Summary: The objective of this study was to evaluate the effect of digestible essential AA density (dEAA) on the performance and processing yield of straight-run Cobb 700 × MV broilers. Broilers were fed a control diet based on the breeder's nutrient recommendations or one of 4 treatments consisting of 5% incremental increases in dEAA density over the control (+5, +10, +15, and +20% dEAA). The digestible lysine content of the control diets was 1.18, 1.07, 0.96, and 0.89% during the starter (0–12 D), grower (12–26 D), finisher (26–36 D), and withdrawal (36–49 D) diets, respectively. Broilers fed the increased dEAA were heavier at 12, 26, and 36 D as compared with those fed the control, and cumulative feed conversion ratio (0–49 D) was decreased by 6 and 8 points when dEAA was increased over the control diet by +10 and +15%, respectively. A 5.75% increase in boneless–skinless breast yield as compared with the control diet was observed when broilers were fed the +20% dEAA diet. A 4.6% increase in tenderloin yield was observed when broilers were fed the +10% dEAA diet, but no further increase was observed with the +15 or +20% dEAA diets. Fat pad yield was observed to decrease from 1.56 to 1.11% as dEAA increased from the control diet to the +20% dEAA diet, respectively. Overall, the improvements to growth performance and processing yields observed in this study support the feeding of increased dEAA diets to Cobb 700 × MV broilers.

Summary: The overall cost of feed is influenced largely by the nutritional requirements that are specified in its formulation and the ingredients that are used to meet those nutrient specifications. To meet the demand for breast meat and further processed products, heavy broiler chickens are grown to body weights exceeding 3.5 kg. In this study, we evaluated the effects of altering AA density and AME content of the diets over the last 3 feeding phases (grower: 12–26 D, finisher: 26–36 D, and withdrawal: 36–49 D) on the growth performance and processing yield of mixed-sex Cobb 700 × MV broilers. Broilers were fed a common starter diet followed by a 3 × 2 factorial arrangement of diets with 3 levels of AA density (low, medium, and high) and 2 levels of energy (low and high) beginning with the grower period. Broilers fed the high AA diet were heavier as compared with those fed the low AA diet, and FCR was observed to decrease incrementally when AA density and energy level were increased independently. Skinless-boneless breast yield increased incrementally with AA density, whereas fat pad yield increased as AA density of the diet decreased. Overall, our results demonstrate that the performance and meat yield of mixed-sex Cobb 700 × MV broilers responded positively to a higher density of AA and energy.

ABSTRACT: The objective of the current study was to evaluate increasing levels of manganese hydroxychloride (MHC) in 45-wk-old white leghorn laying hens, using yolk and shell manganese (Mn) content as a potential marker for Mn concentration. A total of 80, 45-wk-old white leghorns were assigned to 6 dietary treatments, each consisting of 14 individually caged laying hens, with the exception of the reference diet containing 10 individually caged laying hens. The experiment consisted of a reference diet that contained 70 ppm of supplemental inorganic Mn in the form of Mn oxide and 5 experimental treatments each containing 0, 15, 30, 60, and 90 ppm supplemental MHC. Experimental birds were subjected to a 21 D depletion phase in which no supplemental Mn was included in the diet; however, during this time reference fed birds were fed the control diet (70 ppm Mn). After the 21 D depletion phase, the depleted birds were fed experimental diets for a 35 D evaluation period. Yolk and shell Mn content were analyzed at the end of the depletion phase and during the experimental phase on day 5, 10, 15, 25, and 35. During the experimental phase, Mn was replenished in the yolk and shell in all experimental treatments containing supplemental Mn; however, dose and time impacted the rate of replenishment. The yolk tended to be more sensitive to variations in Mn level as increases in Mn inclusion significantly (P < 0.05) increased concentration. These data demonstrate the ability to deplete and replenish Mn, and the use of egg yolk Mn concentration as measurement for determining changes in dietary Mn. At the conclusion of the experiment at 35 D, 60 ppm of Mn hydroxychloride seemed to be adequate in replenishing Mn to the level of the reference.

SUMMARY: Recent research within our laboratory has determined the optimal Ross 708 × Ross YP male broiler dIle:dLys ratio for the starter and grower phases to be 70 and 68%, respectively. Thus, the current objective was to continue to re-evaluate the optimal dIle:dLys ratio for this broiler, focusing on the finisher phase. On d of hatch, 2,400 chicks were equally allocated to 96 pens and fed a common starter (d 0–14; 70% dIle:dLys) and grower diet (d 14–28; 68% dIle:dLys). Pen weights were equalized at d 28 by block (12/treatment). Experimental finisher diets (d 28–42;18.0% crude protein, 3,200 kcal/kg, 0.97% dLys, 130% dLeu:dLys) were created from a common deficient (54% dIle:dLys) corn and soybean meal-based diet and contained animal protein. Half of the deficient was retained to create the summit (84% dIle:dLys). The remaining 5 diets were blended proportions of the deficient and summit diets (ranging from 59 to 79% dIle:dLys). A practical control diet (PRAC-CON; 69% dIle:dLys) was manufactured separately to verify the blended control diet (BLEND-CON). All dIle:dLys ratios were estimated using quadratic regression (QR; 95% of the asymptote), as well as linear and quadratic broken line models (LBL; QBL). Feeding equivalent to or slightly lower than current breeder dIle:dLys recommendations (69%) improved broiler performance from d 28 to 42. Based on the current data and multiple regression models, the estimated ratios ranged from 62 to 66% for BW and BWG and 63 to 66% for FCR. Further research should evaluate the optimal dIle:dLys ratio for this broiler throughout the remaining withdrawal phase.

SUMMARY: Previous research within our laboratory determined the optimal male Ross 708 dIle:dLys ratio for the starter phase to be greater than recent breeder recommendations (70 vs. 67%). Thus, the current objective was to assess the subsequent growth phase (grower) in order to evaluate the optimal dIle:dLys ratio for maximized growth performance of Ross 708 × Ross YP male broilers. On d of hatch, 2,400 chicks were equally allocated to 96 pens and fed a common starter diet. On d 14, pen weights were equalized by block (12 replications/treatments). Experimental grower diets (d 14–28) were created from a common Deficient (53% dIle:dLys) corn and soybean meal-based diet. After batching, half of the Deficient diet was used to create the Summit diet (83% dIle:dLys). The remaining 5 experimental diets ranged from 58 to 78% dIle:dLys and were blended proportions of the Deficient and Summit diets. A practical control diet (PRAC-CON; 68% dIle:dLys) was manufactured separately to verify the blended control diet (BLEND-CON; 68% dIle:dLys). All dIle:dLys ratios were estimated using quadratic regression (QR; 95% of the asymptote), as well as linear and quadratic broken line models (LBL; QBL). Based on the current data and using multiple regression models the estimated ratios ranged from 62 to 68% for BW and BWG, and 67-70% for FCR and are similar to the current breeder nutrient specifications for the grower phase. Further research should evaluate dIle:dLys requirements of male Ross 708 × Ross YP broilers during the remaining grow-out phases.

SUMMARY: Direct-Fed Microorganisms (DFM) and exogenous enzymes have been demonstrated to improve growth performance in poultry and are potentially important components of management programs for antibiotic-free (ABF) poultry production. In this study, we evaluated the effect of a feed additive composed of a DFM product containing spores of 3 Bacillus amyloliquefaciens strains and a multi-enzyme complex of xylanase, amylase, and protease on the performance of broilers with or without an antibiotic growth promoter (AGP), either bacitracin methylene disalicylate (BMD) or virginiamycin. Growth performance of broilers fed one of 6 treatments arranged in a 3 (AGP) × 2 (additive) factorial was evaluated over a 42 d production period. Overall, administration of the feed additive improved body weight, body weight gain, and feed conversion ratio. Administration of either antibiotic significantly reduced cumulative FCR when compared to the control, while BMD administration reduced foot pad lesions as compared to the control. Our results suggest the co-administration of DFM and enzymes may be an important component of ABF poultry production programs and the benefits of their use are not dependent on the presence or absence of AGP.

SUMMARY: Direct-Fed Microorganisms (DFM) are potentially important alternatives to antibiotic growth promoters (AGP). We investigated the administration of Bacillus subtilis administration as a DFM in broiler chickens. Comparison of DFM and AGP administration determined the DFM improved BW, BWG, ADFI, and carcass yield with compared to broilers fed an untreated diet and to those administered an AGP. Evaluation of DFM administration in broilers fed low and high distiller's dried grains with solubles (DDGS) diets determined starter and cumulative FCR of broiler fed a high DDGS diet was greater than those fed a low DDGS diet, while DFM administration improved FCR during the starter phase, days 0–28, and days 0–42 as compared to the untreated diet. Additionally, a DDGS × DFM interaction was observed on days 0–28 FCR. Although they were not significant, differences in FCR between untreated and DFM-treated broilers tended to be greater with high DDGS diets than with low DDGS diets. Overall, our results suggest that administration of B. subtilis as a DFM may potentially be used as an alternative to AGP and FCR improvements may be greater when broilers are fed high-DDGS diets compared to broilers fed low-DGGS diets.

SUMMARY: The objective of the current study was to evaluate the impact of increasing levels of phytase in corn-soy diets fed to male broilers. Experimental treatments included a positive control (PC) with a calculated non-phytate phosphorus (nPP) level of 0.43 and 0.39% for the starter and grower, respectively. The negative control (NC) diet included a reduction in nPP to 0.25 and 0.23% in the starter and grower, respectively, and phytase added to NC diet with increasing levels of 250, 500, 750, 1,000, 2,000, and 3,000/1,000 FTU/kg. All phytase treatments were fed throughout the study with the exception of the 3,000 FTU/kg treatment, which utilized a “step-down” program consisting of 3,000 FTU/kg in the starter being reduced to 1,000 FTU/kg in the grower. Treatment effects on performance, apparent metabolizable energy, apparent ileal digestibility of amino acids, phosphorus, and calcium, and bone mineralization were evaluated on days 14 and 28. The NC diet decreased feed consumption (FC) (P < 0.001), body weight (BW) (P < 0.001), and increased mortality adjusted feed conversion ratio (FCR) (P < 0.001) and mortality (P < 0.05) compared to the PC. Phytase addition improved FC, BW, FCR, and mortality. Birds fed the NC exhibited lower (P < 0.001) bone mineralization, and reduced (P < 0.05) ileal digestibility of all nutrients compared to birds fed the PC. Linear and quadratic effects were observed for tibia mineralization, and all digestibility parameters with phytase addition. High dose inclusion of phytase (2,000 and 3,000/1,000 FTU/kg) yielded the greatest improvement in bird performance, nutrient digestibility, and bone mineralization amongst treatments.

SUMMARY: The objective of the current study was to evaluate the impact of increasing manganese (Mn) hydroxychloride on growth performance and tibia strength of male broilers fed corn-soy diets. A total of 35 Ross 708 male broilers per pen were assigned to dietary treatments containing Mn hydroxychloride at 0, 40, 80, 120, and 160 ppm, respectively. Broilers were fed for a 55 d period. Performance parameters were evaluated, and on days 42 and 55, 5 right tibias from each pen were excised for determination of mineral characteristics. Manganese had no statistical impact on body weight (BW) throughout the duration of the study. During the later stages of production, broilers fed diets containing elevated levels of Mn at or above 80 ppm had improved (P < 0.05) feed conversion ratio (FCR) compared to the birds fed diets containing 0 ppm. Regression analysis correlated elevated dietary Mn with improved FCR through day 14, 28, 42, 49, and 55 and increased Mn tibia concentration on days 42 and 55. At the termination of the study, broilers fed Mn at 160 ppm exhibited improved (P < 0.05) tibia breaking strength as compared to broilers fed 80 and 120 ppm Mn. These data indicate that the dietary concentration of Mn needed to maximize growth performance is higher than the reported value in the NRC (1994) of 60 ppm. Additionally, the requirement to maximize bone strength in heavier broilers may be elevated as compared to the requirement to maximize BW and feed intake.

Summary: Administration of functional feed additives, including direct-fed microorganisms (DFM), dietary prebiotics, and phytogenic preparations, has been demonstrated to improve growth performance, animal health, and microbial food safety in poultry and is thought to be a potentially important component of antibiotic-free poultry production. In this study, we investigated the administration of Bacillus licheniformis (BL) as a DFM, coadministration of BL with an additive blend of a dietary prebiotic and a phytogenic preparation (BL + A), and coadministration of BL with a dietary prebiotic as a synbiotic in broiler chickens in comparison with an antibiotic over a 21 d growth period. Administration of BL improved FCR as compared with untreated broilers through 14 d after hatch. Administration of BL + A and synbiotic increased total Lactic Acid Bacteria and decreased Clostridium perfringens compared with the antibiotic-treated and untreated broilers, respectively. Administration of BL was also observed to increase the villus height to crypt depth ratio as compared with the untreated control. Overall, our results suggest coadministration of B. licheniformis as a DFM with other functional feed additives is able to improve feed efficiency, promote positive shifts in populations of gastrointestinal microbiota, and improve measures of gastrointestinal function.

An experiment was conducted to evaluate the digestible tryptophan (Trp) requirement of laying hens from 22 to 34 wk of age. A total of 252 Hy-line W-36 laying hens were selected at 16 wk of age and allocated by weight (P = 0.90) to 7 dietary treatments resulting in 12 replicate cages of 3 birds for each treatment. A Trp-deficient basal diet was formulated using corn, corn gluten meal, and soybean meal for each of the 3 dietary phases and supplemented with synthetic L-Trp to provide 105, 119, 133, 147, 162, 176, and 190 mg digestible Trp on a daily basis over the experimental period. To adapt the hens to experimental diets, pullets were fed complete diets that contained increasing amounts of corn gluten meal. Hens received a controlled amount of feed daily based on feed intake expected under commercial conditions. Linear and quadratic broken-line, and quadratic polynomial models were used to estimate digestible Trp requirements based on hen-housed egg production (HHEP), egg mass (EM), and feed efficiency (FE). FE was calculated using EM and feed intake. Digestible Trp requirements were estimated to be 137, 183, and 192 mg/d for HHEP; 133, 180, and 183 for EM and 133, 177, and 173 for FE using linear broken-line, quadratic broken-line, and quadratic polynomial analysis, respectively. The quadratic broken line model in this experiment resulted in the best fit (R2) for all parameters measured. Linear broken line estimates resulted in lower estimates that the other models, and HHEP resulted in higher estimated digestible Trp requirement than EM and FE.