Standardized ileal amino acid digestibility in wheat distillers dried grains with solubles for broilers.

A study was conducted to estimate the ileal digestibility of amino acids (AA) in 5 different samples of wheat distillers dried grains with solubles (DDGS) fed to broilers. Two hundred sixteen male Ross broiler chicks were fed a commercial starter diet from d 1 to 15 of age followed by the test diets from d 15 to 21. The 5 test diets consisted of a DDGS sample or wheat as the sole source of AA, dextrose, minerals, and vitamins. Chromic oxide (0.3%) was included in all diets as a digestibility marker. Each test diet was randomly assigned to 6 replicate cages, each with 6 birds. On d 21, birds were killed to sample ileal digesta for determining the apparent (AID) and standardized (SID) ileal AA digestibilities. The SID values were calculated using ileal endogenous AA losses previously determined in our laboratory. Among the indispensable AA in wheat DDGS, the lowest and highest AID average values were observed for Lys (35.6%) and Phe (79.2%), respectively. The most variable AID estimates of wheat DDGS samples were observed for Lys (24.4 to 45.7%), Thr (48.2 to 60.9%), and His (57.4 to 69.1%) as indispensable and Asp (32.5 to 50.9%), Gly (49.6 to 63.1%), and Ala (53.6 to 66.8%) as dispensable AA, respectively. Apparent ileal digestibility estimates of the wheat sample for Lys, Thr, His, Gly, and Ala were 77.5, 74, 83.6, 79.3, and 78.9%, respectively. All AA digestibility estimates for both AID and SID determined in wheat were higher than in wheat DDGS samples (P < 0.05). Considering both AID and SID coefficients of wheat DDGS samples, Lys was the least digestible AA, averaging 35.6 and 40.0%, respectively. Using SID values in practical diet formulation can increase accuracy, prevent overformulation of diets, and reduce cost of safety margins.

Amino acid digestibility of distillers dried grains with solubles, produced from sorghum, a sorghum-corn blend, and corn fed to growing pigs.

The objective of this experiment was to measure the concentration and digestibility of CP and AA in distillers dried grains with solubles (DDGS) produced from sorghum (S-DDGS) or a blend of sorghum and corn grains (SC-DDGS), and to compare these values with the digestibility of CP and AA in corn-based DDGS (C-DDGS). Eleven growing barrows (initial BW = 44.6 +/- 6.5 kg) were surgically fitted with a T-cannula in the distal ileum and allotted to a Youden square design with 11 diets and 8 periods. One diet contained 66.7% S-DDGS, 1 diet contained 66.7% SC-DDGS, 8 diets contained 66.7% C-DDGS, and 1 diet was N-free. Chromic oxide (0.3%) was used in all diets as an indigestible marker. The direct procedure was used to measure apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in the 10 sources of DDGS. Results of the experiment showed that the AID of Lys was not different among S-DDGS, SC-DDGS, and C-DDGS. The mean SID of CP, Arg, and Lys in C-DDGS were not different from values obtained in S-DDGS and SC-DDGS. The SID of Trp in S-DDGS (72.0%) was greater (P < 0.01) than in C-DDGS (64.9%), but there was no difference between C-DDGS and SC-DDGS (62.4%). The SID of CP and all AA were different among the 8 sources of C-DDGS (P < 0.01). Among the indispensable AA, Lys had the greatest variation and the SID ranged from 55.7 to 68.7%. The concentration of total and digestible AA was highly correlated (r(2)) for Arg (0.88), Ile (0.85), Leu (0.82), Phe (0.84), and Trp (0.84), but reduced r(2) values were observed for Lys (0.66) and Thr (0.39). A low correlation between the concentration and digestibility of AA indicates that it is desirable to develop in vitro procedures to predict digestible AA concentration in DDGS. In conclusion, SID values for CP and Lys in S-DDGS and SC-DDGS are within the range of values obtained in C-DDGS, but for many other AA, SID values in S-DDGS and in SC-DDGS are less than in C-DDGS.

Apparent absorption of methionine and 2-hydroxy-4-methylthiobutanoic acid from gastrointestinal tract of conventional and gnotobiotic pigs.

The effect of commensal microbiota and feeding corn or wheat/barley-based diets on the apparent gastrointestinal absorption of dl-methionine (MET) and 2-hydroxy-4-methylthiobutanoic acid (MHA-FA) was studied in conventional (n = 32) and gnotobiotic pigs (n = 24). Conventional pigs (CON) were vaginally delivered and sow-reared until weaning at 14 days of age. Gnotobiotic pigs were derived by caesarian section and reared in HEPA (high efficiency particulate air)-filtered isolator units with ad libitum access to a milk-based formula. Corn or wheat/barley-based diets were fed to all pigs from 14 to 24 days of age. At 24 days of age, after an overnight fast, pigs were fed 20 g/kg BW of experimental diet supplemented with 107 Bq of either 3H-l-MET or 3H-l-MHA-FA per kg of feed and chromic oxide (0.5% wt/wt). Pigs were killed for sample collection 3 h after consuming the meal. Residual 3H-MET and 3H-MHA-FA were estimated in gastrointestinal contents as the ratio of 3H : chromic oxide in digesta samples to the ratio of 3H : chromic oxide in feed. In CON pigs, feeding a wheat/barley-based diet increased (P < 0.05) total aerobes, whereas supplementation with MHA-FA increased (P < 0.05) total aerobes and lactobacilli populations in proximal small intestine (SI). Among the gnotobiotic pigs, bacterial contamination occurred such that eight pigs (two isolators) were monoassociated with a Gram-negative bacteria closely related to Providencia spp. and 16 pigs (four isolators) were monoassociated with Gram positive Enterococcus faecium. Species of monoassociated bacterial contaminant and diet composition did not affect residual methionine or MHA-FA in digesta. In both CON and monoassociated (MA) pigs, methionine and MHA-FA were retained in stomach (92%) but disappeared rapidly from proximal SI. Residual methionine and MHA-FA in digesta was not different in MA pigs; however, in CON pigs, less (P < 0.01) apparent residual methionine was found in digesta recovered at 25% (from cranial to caudal) and 75% of SI length compared with MHA-FA. Apparent residual methionine was 16% and 8% compared with 34% and 15% for MHA-FA, at the 25% and 75% locations, respectively. In proximal SI tissue, significantly (P < 0.05) higher radioactivity (cpm/mg wet tissue) was associated with MET pigs (8.56 ± 0.47) as compared to MHA-FA ones (5.45 ± 0.50). This study suggests that microbial metabolism of MHA-FA increases retention in small intestinal digesta relative to methionine and contributes, in part, to the lower bioefficacy of MHA-FA compared to methionine.

Factors affecting the variability in ileal amino acid digestibility in corn distillers dried grains with solubles fed to growing pigs.

Two experiments were conducted to compare the ileal digestibility of AA in distillers dried grains with solubles (DDGS) sourced from different regions (IL, MN, KY), to compare AA digestibility in DDGS and in distillers dried grains (DDG) and to compare AA digestibility in DDGS from ethanol production (DDGS(ethanol)) and DDGS from beverage production (DDGS(beverage)). In Exp. 1, five samples of DDGS(ethanol) were sourced from Minnesota (MN1, MN2), Illinois (IL1, IL2), and from Kentucky (KY). In Exp. 2, six samples of DDGS(ethanol), 1 sample of DDG, and 1 sample of DDGS(beverage) were used to compare values for apparent ileal digestibility and standardized ileal digestibility (SID) of AA between DDGS(ethanol) and DDGS(beverage) and between DDG and DDGS(ethanol). Results of Exp. 1 showed that the SID of Lys in DDGS from MN2 (72.8%) was greater (P < 0.01) than in DDGS from MN1 (66.8%), IL1 (66.8%), and KY (65.8%) but not different from IL2 (70.1%). Except for Leu and Glu, no differences in SID for any of the other AA were observed among the 5 sources of DDGS. In Exp. 2, the SID for Lys in DDGS(beverage) was greater (P < 0.01) than in DDGS(ethanol) (69.3 vs. 64.8%), but for CP and all other AA except His, no differences between the 2 types of DDGS were observed. The SID for most AA in DDG were greater (P < 0.05) than in DDGS(ethanol), which suggests that the AA in the solubles that are added to DDGS may be less digestible than the AA in DDG. In conclusion, results of these experiments confirm that the digestibility of Lys is more variable among sources of DDGS than the digestibility of other AA. However, the SID of AA among DDGS sources within a region can vary as much as among DDGS sources from different regions, and AA in DDGS(beverage) may be as digestible as AA in DDGS(ethanol). The digestibility of AA in DDG is greater than in DDGS, which indicates that AA in the solubles have a lower digestibility than AA in DDG.

Comparison of various methods for endogenous ileal amino acid flow determination in broiler chickens.

The purpose of this study was to compare estimates of ileal endogenous amino acid (IEAA) losses determined in broiler chicks with a nitrogen-free diet (NFD), diets containing highly digestible proteins as intact casein or enzymatically hydrolyzed casein (EHC), and the regression method (RM). Male Ross 308 broiler chicks were fed a commercial starter diet from d 1 to 15 of age and the following test diets from d 15 to 21: NFD and diets containing 5, 10, or 15% casein or EHC as the sole protein source. All diets contained chromic oxide as a digestibility marker. Each diet was assigned to 6 replicate cages, with 10 birds each. On d 21, birds were euthanized to sample ileal digesta. Feeding increasing levels of EHC or casein linearly (P<0.0001) increased IEAA flow. Nonlinearity (P<0.05) was detected for Ile, Val, Glu, and Ser with EHC and for Met with casein. Compared with the NFD method, IEAA values extrapolated to zero EHC or casein intake were similar for all amino acids except Ile (200 vs. 321 mg/kg of DM intake), Val (270 vs. 341 mg/ kg of DM intake), Ala (217 vs. 262 mg/kg of DM intake), and Ser (343 vs. 577 mg/kg of DM intake), whose flows were higher with EHC (P<0.05). The present results show that IEAA values determined with the NFD, EHC, and casein diets, at different inclusion levels, were different for most amino acids and that, for all amino acids, the values obtained with NFD and RM involving feeding graded levels of casein or EHC were comparable. Thus, using IEAA values obtained with either the NFD or the RM to calculate standardized ileal amino acid digestibility coefficients will give similar values.

Ideal ratios of isoleucine, methionine, methionine plus cystine, threonine, tryptophan, and valine relative to lysine for white leghorn-type laying hens of twenty-eight to thirty-four weeks of age.

Seven separate experiments were conducted with Hy-Line W-36 hens to determine the ideal ratio of Arg, Ile, Met, Met+Cys, Thr, Trp, and Val relative to Lys for maximal egg mass. The experiments were conducted simultaneously and were each designed as a randomized complete block design with 60 experimental units (each consisting of 1 cage with 2 hens) and 5 dietary treatments. The 35 assay diets were made from a common basal diet (2,987 kcal/kg of ME; 12.3% CP; 4.06% Ca, 0.47% nonphytate P), formulated using corn, soybean meal, and meat and bone meal. The true digestible amino acid contents in the basal diet were determined using the precision-fed assay with adult cecectomized roosters. Crystalline L-Arg (free base), L-Ile, L-Lys.HCl, DL-Met, L-Thr, L-Trp, and L-Val (considered 100% true digestible) were added to the basal diet at the expense of cornstarch to make the respective assayed amino acid first limiting and to yield 5 graded inclusions of the assayed amino acid. Hens were fed the assay diets from 26 to 34 wk of age, with the first 2 wk considered a depletion period. Egg production was recorded daily and egg weight was determined weekly on eggs collected over 48 h; egg mass was calculated as egg production x egg weight. The requirement for each amino acid was determined using the broken-line regression method. Consumption of Arg did not affect egg mass, thus a requirement could not be determined. The true digestible amino acid requirements used to calculate the ideal amino acid ratio for maximum egg mass were 426 mg/d of Ile, 538 mg/d of Lys, 253 mg/d of Met, 506 mg/d of Met+Cys, 414 mg/d of Thr, 120 mg/d of Trp, and 501 mg/d of Val. The ideal amino acid ratio for maximum egg mass was Ile 79%, Met 47%, Met+Cys 94%, Thr 77%, Trp 22%, and Val 93% on a true digestible basis relative to Lys. The ideal Met and Met+Cys ratios were verified in an ensuing identical experiment with 52- to 58-wk-old hens.

Effect of amino acid formulation and amino acid supplementation on performance and nitrogen excretion in turkey toms.

A 2 x 2 factorial experiment was conducted to determine whether diets formulated with 2 (Lys and Met) or 3 (Lys, Met, and Thr) supplemental AA to 100 or 110% of NRC (1994) amino acid (AA) recommendations would affect performance and N excretion of turkey toms. Diets were formulated with corn, soybean meal (SBM), and 6% meat and bone meal. Diets were formulated to maximize SBM inclusion when formulated with 2 supplemental AA, thereby resulting in 2.0, 1.5, 1.4, and 1.0% units more CP than diets containing 3 supplemental AA at 4 to 8, 8 to 12, 12 to 16, and 16 to 20 wk of age, respectively. Each diet was fed to 12 replicate pens of birds with 10 birds per pen. Body weight, feed intake, and feed/gain was not affected by AA formulation or AA supplementation (average 20-wk BW = 20.7 kg). Similarly, the weight of the pectoralis major at 20 wk of age was not different between birds fed different diet regimens. Nitrogen intake was affected by diet with birds fed 100% NRC AA consuming 144 g (7.3%) less N, with $0.48 less feed cost/20-wk tom, than those fed 110% NRC AA. Similarly, birds fed 3 vs. 2 supplemental AA consumed 154 g less feed N (8.4%) with $0.37 less feed cost/20-wk tom to 20 wk of age. These differences in N intake resulted in 0.8 kg more N in litter/pen (7%; P = 0.067) in birds fed 100% NRC AA vs. those fed 110% NRC. Similarly, birds fed 3 vs. 2 supplemental AA had 1.24 less N in litter/pen (10.8%). These data suggest that diets containing AA formulations above NRC (1994) recommendations do not provide any additional performance or pectoralis major yield benefits, yet results in considerable increases in excreted N. In addition, formulation with 3 supplemental AA results in a sizeable reduction in N consumed and excreted.

Effect of different dietary methionine sources on intestinal microbial populations in broiler chickens.

Two experiments were conducted to study the effect of various levels of DL-Met or 2-hydroxy-4-methylthiobutanoic acid (MHA-FA) on Clostridium perfringens and other intestinal bacteria in broiler chickens. In each experiment, 2 cages of 6 birds (14 d posthatch) were assigned to 1 of 7 different diets in a 2 x 4 factorial arrangement. The main effects were Met source (either DL-Met or MHA-FA) and Met level (0, 0.2, 0.4, or 0.8% dl-Met or 0, 0.227, 0.454, and 0.908% MHA-FA, thus providing 4 corresponding equimolar levels of each Met source). All birds were orally gavaged with a C. perfringens type A broth culture on d 1 and on d 14 to 20 and killed on d 28. Intestinal populations of C. perfringens, lactobacilli, Streptococcus group D, and coliforms were enumerated in the ileum and cecum, and necrotic enteritis intestinal lesions were scored. There was a significant reduction (P < 0.05) in C. perfringens populations in birds fed either Met source in the cecum (experiment 1) or the ileum and cecum (experiment 2). In experiment 2, the lactobacillus populations were significantly higher (P < 0.05) in the ceca of birds receiving 0.8% Met than in the birds given diets with the other levels of Met tested. Significantly lower populations (P < 0.05) of coliforms and Streptococcus group D were enumerated in the ileum of birds fed the 0.8% Met-supplemented diet than in the other dietary treatments. The effect of Met source on intestinal bacteria was not significant, suggesting that both DL-Met and MHA-FA have similar antibacterial properties. Last, there were no significant differences in intestinal lesion scores or the performance of birds fed different Met sources and concentrations. The results suggest that both DL-Met and MHA-FA may reduce intestinal populations of C. perfringens in broiler chickens when used in relatively high concentrations, and may reduce the risk of necrotic enteritis. Thus, feeding low-protein diets supplemented with crystalline amino acids might be beneficial in terms of the growth of various enteric pathogens.

The effect of corticosterone-induced stress on amino acid digestibility in Ross broilers.

Two experiments (Exp.) were conducted to establish amino acid (AA) digestibility coefficients (DC) for broilers given corticosterone (CS)-induced stress using the apparent ileal digestibility assay. For Exp. 1, 192 Ross x Ross 708 male broilers were placed into 16 floor pens (12 birds/pen). For Exp. 2, 120 Ross x Ross 308 male broilers were placed into 10 floor pens (12 birds/pen). Pens contained nipple drinkers, pan feeders, and soft-wood shavings. Both experiments were completely randomized designs using pen as the experimental unit. In both experiments, chicks were given a common starter diet from d 1 to 20. From d 21 to 30, broilers were provided a control diet or the control + 15 mg of CS/kg of diet dissolved in soybean oil (8 and 5 replications/treatment in Exp. 1 and 2, respectively). Diets were based on corn (65.07%) and soybean meal (26.36%) and contained an indigestible marker (chromic oxide 0.3%). Diets were formulated to contain 3,175 kcal of ME, 18.5% CP, 0.79% digestible TSAA, and 1.00% digestible Lys. Stress validation was accomplished by measuring BW gain, feed intake, and liver weight on d 30. Evidence that stress occurred was apparent due to the fact that broilers fed CS had lower BW gain and higher liver weight than those fed control. On d 30, the ileal contents were removed from 3 birds/pen, pooled, dried, and analyzed for AA content. Amino acid DC were calculated using the following equation: DC = 100 -(dietary marker % x ileal AA %) / (ileal marker % x dietary AA %) x 100. Amino acid digestibility did not differ (P > 0.05) between treatments in either experiment. Based on this research, future research should be directed at establishing DC for other nutrients in stressed broilers or the effect of different nutrients on the stress response.

Broiler responsiveness (Ross x 708) to diets varying in amino acid density.

Sex-separate male and female broilers (2,592 broilers; Ross x 708) were placed in 144 floor pens (12 replications per treatment) and fed diets containing high (H) and moderate (M) amino acid density from 1 to 55 d of age. Diets were formulated using ileal digestible amino acid ratios to Lys. Six dietary treatment combinations (MMMMM, HMMMM, HHMMM, HHHMM, HHHHM, and HHHHH) were implemented in 5 diet phases (1 to 5, 6 to 14, 15 to 35, 36 to 45, and 46 to 55 d of age). Male birds were heavier (P < or = 0.05) and had lower (P < or = 0.05) feed conversion, abdominal fat, and breast yield than female birds. Birds fed H diets in the first 3 phases had optimal (P < or = 0.05) BW and feed conversion (d 35, and 45), but optimal (P < or = 0.05) feed conversion at d 55 warranted H diets in all phases. Breast meat (d 35) and carcass (d 55) relative to BW were highest (P < or = 0.05) in birds fed H diets in the first 3 phases; however, differences in 55 d breast meat yield did not occur. Results indicate that amino acid needs of Ross x 708 broilers are most critical from 1 to 35 d of age. Predicted economic margins were advantageous in birds fed H diets resulting in dollar 0.12 and dollar 0.05/bird more income over feed costs at 35 and 55 d, respectively, in comparison with birds fed M diets.

Dietary tryptophan need of broiler males from forty-two to fifty-six days of age.

Tryptophan requirements of broiler males from 42 to 56 d of age were studied. Ross x Ross 308 chicks were placed in an open-sided house, and provided common starter and grower diets from 0 to 42 d of age. Subsequently, a corn, soybean meal, corn gluten meal, and gelatin combination of feedstuffs provided 0.12% Trp to which 0.04% increments of L-Trp were supplemented at the expense of an isonitrogenous amount of L-Glu to 0.24%. Birds that received diets containing 0.12% Trp exhibited aberrant behavior based on the spillage of considerable amounts of feed from the trough and contamination of adjacent waterers with floor litter. There were reductions in body weight gain, feed conversion, and carcass and breast fillets weights and yields with dietary Trp at 0.12%, but these were not affected at Trp levels at or above 0.16%. Exponential regression analyses showed that body weight gain improved as Trp increased, with maximum overall performance being attained at 0.17%, whereas chilled carcass weight maximized at 0.16% dietary Trp. Nitrogen retention measured using the same experimental feeds and sample birds at 48 to 49 d of age was unaffected by dietary Trp. Plasma uric acid, albumin, total protein, and aspartate-transferase measured concurrently with nitrogen retention were not altered; however, blood glucose was reduced in broilers fed 0.12% dietary Trp. Overall results suggest that broiler males need approximately 0.17% dietary Trp between 42 and 56 d of age, which closely agrees with the NRC (1994) recommendation of 0.16% Trp estimated from modeling for this feeding period.

Dietary glycine concentration affects intestinal Clostridium perfringens and lactobacilli populations in broiler chickens.

Previous studies have reported that intestinal populations of Clostridium perfringens, the causative agent of necrotic enteritis (NE), are correlated with diets high in glycine. To establish a direct causative link, 3 trials were conducted to examine the effect of dietary glycine levels on gut populations of C. perfringens, alpha-toxin production, and NE lesion scores in broiler chickens. In trials 1 and 2, 12 groups of 4 birds were fed 4 different ideal protein-balanced diets formulated to contain 0.75, 1.58, 3.04, or 4.21% glycine from d 14 to 28 of age. In trial 3, 24 groups of 4 birds were given 6 different ideal protein-balanced diets formulated to contain 0.50, 0.75, 1.00, 1.50, 2.00, or 4.00% glycine. All birds were orally challenged with a broth culture of C. perfringens type A on d 1 and between d 14 and 21 of age and killed on d 28. The majority of birds showed clinical signs of NE with 4.16 to 8.33% mortality in the 3 trials. The highest mortality and intestinal lesion scores were observed in chickens receiving 3.04% glycine in trials 1 and 2, and 4.00% glycine in trial 3. Clostridium perfringens populations in the cecum varied quadratically with increasing dietary glycine, with the maximal response seen at 3.30,3.89, and 3.51% dietary glycine in trials 1, 2, and 3, respectively. Numbers of lactobacilli in cecum declined significantly (P < 0.05) with increasing levels of glycine. The results suggest that dietary glycine level has a significant effect on C. perfringens and lactobacilli populations and may be a predisposing factor for NE in broiler chickens.

Threonine needs of broiler chickens with different growth rates.

The Thr needs in 3 commercial broiler strains (A, multipurpose; B, high yield; C, high yield) known to differ in terms of feed intake, growth rate, and breast yield were evaluated. Birds were randomized across 96 floor pens (12 birds/pen), received a common diet from d 1 to 20, and were fed graduations of Thr (0.52 to 0.87% total Thr in 0.07% increments) from d 21 to 42. Treatments (3 x 6 factorial) were replicated 5 or 6 times. The corn, soybean meal, and peanut meal test diet contained 0.43 and 0.96% digestible Thr and Lys, respectively. An additional group of strain C birds (6 pens) was maintained on a corn-soybean meal diet containing surfeit Thr (0.73% of diet). Birds fed the corn and soybean meal diet performed similarly (P < or = 0.05) to birds fed peanut meal diets. A feed conversion interaction (P < or = 0.05) occurred indicating that strain C was more sensitive to Thr deficiency than strains A and B. The abdominal fat interaction (P < or = 0.05) indicated that strain A had more relative abdominal fat than strains B and C. All strains differed (P < or = 0.05) in terms of BW gain (A, 78.2; B, 75.1; C, 72.9 g/d). Strain C had the lowest (P < or = 0.05) feed intake, which resulted in the lowest (P < 0.05) Thr intake, but it had the highest (P < or = 0.05) breast meat yield. Most parameters tested yielded quadratic (P < or = 0.05) models whereby Thr estimates could be predicted. Namely, BW gain and breast meat yield resulted in total Thr estimates (95% of maximum response) of 0.74 and 0.71%, respectively, which are in close agreement with the 1994 NRC (0.74%). The plasma Thr sigmoid response verified the former estimates. Analysis of strain intercepts and slopes as affected by Thr differed (P < or = 0.05) in terms of feed intake but not BW gain or breast meat yield. The 21 to 42 d Thr need across strains was estimated as 0.74% total or 0.65% digestible. Because dietary Lys was not in excess of the bird's needs, the former digestibility estimate equated to a Thr/Lys of 0.68.

Valine needs of male broilers from 42 to 56 days of age.

An experiment was conducted using Ross x Ross 308 males to estimate the proportion of dietary valine needed to optimize performance in broilers from 42 to 56 d of age. All birds received common feeds from 0 to 42 d, and then experimental diets were given to 56 d of age. A diet consisting of corn, soybean meal, and corn gluten meal (17% CP, 3.25 kcal of ME/g) having 0.60% valine served as basal feed. All other essential amino acids were above recommended levels. Successive additions of 0.07% of L-valine were isonitrogenously substituted for L-glutamic acid up to a total of 0.81%. Regression analysis (95% of response) indicated that valine at 0.72% of the diet maximized body weight gain, whereas 0.73% optimized feed conversion. Depot fat removed from the abdominal cavity after processing was unaltered, and weights of resultant chilled carcasses maximized at 0.73% valine in parallel with final live weight. The amount of fillets recovered from chilled carcasses optimized at 0.73% valine; however, the incidence of distinctive blood streaks in the meat (splash) progressively increased with valine as did the level of redness apart from streaking, based on light reflectance. Given lysine at 0.85%, a ratio of 0.86 with valine appears to be adequate. The presently determined requirement of 0.73% total valine (0.67% digestible) for broiler males from 42 to 56 d of age is slightly higher than the 0.70% recommended by the NRC.

Lysine needs of summer-reared male broilers from six to eight weeks of age.

Experimentation was conducted to estimate dietary lysine needed to optimize production of summer-reared broilers between 42 to 56 d of age. Male Ross x Ross 308 chicks were placed in floor pens of an open-sided house and provided common feeds from placement to 42 d of age. During the subsequent 42 to 56 d, birds received a corn-soybean meal basal diet (18% CP and 3,250 kcal/kg ME) established to provide limiting essential amino acids favorably balanced near requirement levels with the exception of lysine. Four 0.10% increments of L-lysine isonitrogenously displaced L-glutamic acid from the basal diet to provide analyzed values progressing from 0.85 to 1.25%. Body weight gain and mortality were not altered as dietary lysine increased; however, feed conversion linearly improved. Chilled carcass yield, amount of abdominal fat, and recovery of skinless boneless breast meats were not affected. Measurements on nitrogen balance and plasma levels of total protein, albumin, glucose, and uric acid taken at 49 d from a concurrent study using sample birds in raised-wire cages and identical feeds also failed to define a requirement. However, plasma aspartic transferase increased to a maximum approximating 1.05% lysine, whereas free lysine concentration linearly increased to the highest level. Overall data supported a lysine requirement no less than 0.95% that was greater than the previous minimum of 0.85% obtained under similar terms without heat stress. Suppression of growth from heat stress appears to reduce the absolute need for lysine; however, increased dietary concentration appears necessary to accommodate depressed feed intake and improve its effectiveness.

Arginine need of heavy broiler males: applying the ideal protein concept.

An experiment was conducted to determine arginine need of male broilers between the ages of 42 to 56 d, in conjunction with dietary protein approaching a previously advocated ideal amino acid pattern. Ross x Ross 308 chicks were reared in floor pens (32 pens with 35 birds each) of an open-sided house on common feeds until 42 d of age. From 42 to 56 d of age, birds were fed a corn-soybean meal diet (17% CP, 3,250 kcal/kg ME, and 0.85% lysine) having basal arginine at 0.80%, and then progressive additions of 0.15% were made until 1.25% was reached to form the dietary treatments. Final body weight together with body weight gain and feed conversion through the 42-to-56-d experimental period were optimized at 0.98% arginine. Weight of the chilled carcass was optimized at 1.00% arginine, whereas depot fat that had been removed from the abdominal cavity continued to decrease to the highest level of supplementation. Additional total arginine to 1.05% was needed to maximize weight recovery of fillets and total breast meat. An arginine requirement for nutritional purposes approximating 1.00% as advocated by NRC (1994) is in general agreement with present results for live production and meat yield; however, carcass incidence of skin scratch infections and parts defects from processing stresses continually responded until the highest level to suggest that additional amounts would be needed for immunological and connective tissue challenges.

Relative effectiveness of methionine hydroxy analog compared to DL-methionine in broiler chickens.

Two broiler experiments were conducted to assess the relative bioefficacy of liquid DL-Met hydroxy analog-free acid (MHA-FA) and DL-Met (DLM). Exponential regression analysis was used to determine biological efficacy based on body weight, feed conversion, and carcass responses to dietary Met source. In Trial 1, four graded inclusion levels of DLM and liquid MHA-FA (0.06, 0.12, 0.18, and 0.24%) were each added to a basal diet that met the nutrient and energy requirements of broiler chickens, with the exception of Met + Cys. In four additional treatments, diluted DLM (65%) was added at the same supplementation levels as pure DLM and liquid MHA-FA. In the 42-d trial, broilers responded significantly (P < 0.05) to the supplements. Regression analysis revealed that liquid MHA-FA was 68% (weight gain), 67% (feed conversion), 62% (carcass yield), and 64% (breast meat yield) as efficacious as pure DLM on an as-fed basis. Responses to liquid MHA-FA and diluted DLM were very similar at corresponding supplementation levels. Diluted DLM as an internal standard confirmed that exponential regression analysis was a statistically valid technique for determination of the relative efficacy of nutrient sources. In Trial 2, five graded inclusion levels of each DLM (0.040, 0.091, 0.152, 0.222, and 0.303%) and liquid MHA-FA (0.045, 0.102, 0.170, 0.250, and 0.350%) were added to a basal diet limiting in Met + Cys but adequate in all other nutrients and energy. Liquid MHA-FA was 72% (weight gain), 51% (feed conversion), 48% (carcass yield), and 60% (breast yield) as efficacious as DLM on a weight-for-weight basis.

Lysine need of heavy broiler males applying the ideal protein concept.

An experiment was conducted to measure the response of broiler males to dietary lysine progressing from 0.75 to 1.15% between 42 and 56 d of age. Chicks (Ross x Ross 308) were placed in floor pens (30 pens having 35 chicks each) of an open-sided house and provided common feeds to 42 d of age. From 42 to 56 d, a corn-soybean meal diet (18% CP and 3,250 kcal/kg ME) having total lysine at 0.75% was supplemented with additions of 0.10% until 1.15%. All other essential amino adds were "ideally" balanced to one another within the limits of practicality assuming 0.85% total lysine. Birds had continuous access to feed, water, and light. Live performance during experimentation was particularly favorable. Weight gain between 42 and 56 d of age was similar among birds receiving all levels of lysine, while feed conversion was optimized at 0.85%. Depot fat removed from the abdominal cavity, yield of the resultant chilled carcass, and the amount of fillet (pectoralis major) cone deboned from the breast were unaltered by dietary lysine level. However, yield of tenders (pectoralis minor) decreased as supplemental lysine increased, whereas the incidence of myopathy (green muscle disease) increased. The lysine requirement of 0.85% as advocated by NRC (1994) for broilers between 42 and 56 d of age is in agreement with present results and may have been predisposed by its favorability of balance with all other essential amino adds.