Determination of TMEn, standardized amino acid digestibility, phosphorus digestibility, and phosphorus bioavailability in conventional and reduced phosphorus distillers dried grains with solubles.

The TMEn, amino acid (AA) digestibility, and P availability in 2 conventional corn distillers dried grains with solubles (C-DDGS1 and 2; 0.86 to 1.14% P, DM basis) and reduced phosphorus DDGS (RP-DDGS; 0.39% P) were evaluated. The TMEn of C-DDGS1 and 2 and RP-DDGS were determined in Experiment 1 using conventional adult Leghorn roosters, while standardized AA digestibility was determined in Experiment 2 using cecectomized roosters. Apparent ileal digestibility (AID) of P at different Ca levels was determined using precision-fed (crop intubation) broiler chickens in Experiments 3 and 4. The AID and total tract retention of P in C-DDGS2 were evaluated in Experiment 5 using ad libitum-fed broilers. Phosphorus bioavailability in C-DDGS2 relative to KH2PO4 based on bone ash was determined in Experiment 6. Experiments contained 4 to 5 replicates per treatment. In Experiment 1, the TMEn of C-DDGS1 and RP-DDGS was 3,428 and 2,840 kcal/kg, respectively (DM basis). In Experiment 2, there were no differences (P > 0.05) in rooster AA digestibility values between C-DDGS1 and RP-DDGS. In Experiment 3 with precision-fed chicks, AID of P in C-DDGS1 and RP-DDGS was 81 and 59%, respectively; there was no effect (P > 0.05) of increasing dietary Ca level from 0.04 to 1.0% for C-DDGS1 or reducing Ca from 1.5 to 1.0% for RP-DDGS. The AID of P in precision-fed chicks for C-DDGS2 in Experiment 4 was 48 and 80% at 1.3 and 0.3 Ca:total P ratios, respectively (P < 0.05). In Experiment 5, AID of P in C-DDGS2 at Ca:total P ratios of 1.3 and 2.5 was 63 and 42%, respectively, in precision-fed chicks. Regression of bone ash content (mg/tibia) on supplemental P intake in Experiment 6 yielded a P bioavailability of 61% relative to KH2PO4 for C-DDGS2. In conclusion, total and digestible P content in RP-DDGS was greatly reduced compared with C-DDGS, and the digestibility and bioavailability of the P in C-DDGS was affected by type of experimental assay and dietary Ca level.

Quantification of secretory IgA and mucin excretion and their contributions to total endogenous amino acid losses in roosters that were fasted or precision-fed a nitrogen-free diet or various highly digestible protein sources.

The objective of this study was to quantify total secretory IgA (sIgA) and mucin excretion via excreta in roosters fed diets containing highly digestible protein sources and to determine their proportional contributions to total endogenous amino acid (AA) losses. Precision-fed rooster assays with 24 h excreta collections were conducted using conventional White Leghorn roosters (4-8 roosters per treatment). In Experiment 1, roosters were fasted or precision-fed 30 g (crop intubation) of a nitrogen-free (NF) or semi-purified diet containing 10% casein. Roosters in Experiment 2 received a NF or semi-purified diet containing either 10% casein, 17% whole egg, 10% egg white, 9.8% soy protein isolate, 10.2% chicken breast meat, 11.2% spray-dried animal plasma (SDAP), or an AA mixture containing the same AA as casein. A Latin square design was used in Experiment 3, where roosters received NF or semi-purified diets containing either 10% casein, 17% whole egg, or 9.6% of a crystalline AA mixture to evaluate both diet and individual bird effects. In Experiment 1, mucin excretion did not differ (P > 0.05) among treatments; however, total sIgA excretion was lower for fasted birds, intermediate for the NF diet, and highest for casein (P < 0.05). Total endogenous AA losses (proportion of the total) from sIgA were higher for roosters fed casein, whereas mucin contributions were higher for fasted roosters (P < 0.05). In Experiment 2, sIgA excretion did not differ (P > 0.05) among treatments; however, mucin excretion was reduced for NF, whole egg, egg white, and chicken breast compared with casein and SDAP. In Experiment 3, sIgA and mucin excretion did not differ (P > 0.05) among treatments; however, sIgA excretion differed among individual roosters (7-27 mg/24 h; P < 0.05). Overall, fasting reduced sIgA excretion and sIgA and mucin excretion were affected by dietary protein source. Further, roosters excreted a substantial amount of sIgA, and sIgA and mucin were considerable contributors to total endogenous AA losses.

Standardized amino acid digestibility and true metabolizable energy for several increased protein ethanol co-products produced using back-end fractionation systems.

Precision-fed rooster trials were conducted to evaluate standardized AA digestibility and TMEn of the increased protein ethanol co-products corn fermented protein (CFP), high protein-distillers dried grains with solubles (HP-DDGS), and reduced fiber high protein-DDGS (RFHP-DDGS) produced using post-fermentation back-end fractionation systems. The TMEn was determined using conventional adult Leghorn roosters, while cecectomized roosters were used to determine standardized AA digestibility. Three to 6 roosters were fasted per treatment for 26 h prior to crop intubation with 27 g of sample and excreta were collected for 48 h post-feeding. Statistical analyses were conducted using a one-way ANOVA for a completely randomized design. Eight samples of CFP were found to contain a mean of 56% CP (DM basis) compared with a mean of 32% for conventional DDGS. The mean TMEn of CFP (3,556 kcal/kg) was greater (P < 0.05) than conventional DDGS1 and 2 (2,767 kcal/kg DM); mean standardized AA digestibility for CFP was similar to conventional DDGS and ranged from 88 to 94%. The mean digestible Lys, Met+Cys, and Thr concentrations for conventional DDGS were 0.79, 1.12, and 0.94%, respectively, whereas those for CFP were 1.74, 2.06, and 1.88%, respectively (DM basis). Two samples of HP-DDGS contained a mean of 51% CP (DM basis), a mean TMEn of 3,325 kcal/kg DM, a mean standardized AA digestibility of 90%, and mean concentrations of digestible Lys, Met+Cys, and Thr, which were 1.53, 1.77, and 1.60%, respectively (DM basis). The mean CP content of 2 RFHP-DDGS was 48% and the mean TMEn was 3,711 kcal/kg DM, which was greater (P < 0.05) than conventional DDGS3 and 4 (2,920 kcal/kg DM). Mean standardized AA digestibility of RFHP-DDGS was 90% and mean digestible Lys, Met+Cys, and Thr concentrations increased from 0.82, 1.01, and 0.95% for conventional DDGS, respectively, to 1.00, 1.59, and 1.44% for RFHP-DDGS, respectively (DM basis). Results indicate these high protein corn ethanol co-products have increased nutritional value for poultry compared with conventional DDGS.

Research Note: Evaluation of a precision-fed rooster assay for determination of phytic acid disappearance in feedstuffs.

The objective of this study was to evaluate a precision-fed rooster assay that is suitable for determination of phytic acid (myo-inositol 1,2,3,4,5,6-hexakis; InsP6) disappearance in plant-based feed ingredients. A 48-h precision-fed rooster assay was used to measure InsP6 disappearance using conventional White Leghorn roosters. A minimum of 4 individually-caged roosters per treatment were fasted for 26 h prior to crop intubation with 15 to 30 g of sample, and excreta were quantitatively collected for 48 h. Soybean meal, soybean hulls, canola meal, conventional distillers dried grains with solubles (DDGS), palm kernel meal (PKM), and wheat bran were evaluated in Experiment 1, whereas wheat middlings (WM) and rice bran (RB) were evaluated without and with 1,000 and 1,800 U/kg phytase in Experiment 2. Data from Experiment 1 were subjected to a one-way ANOVA for a completely randomized design, while data from Experiment 2 were subjected to two-way ANOVA for a 2 × 3 factorial arrangement of treatments. In Experiment 1, InsP6 disappearance ranged from 3 to 95% among all ingredients. The InsP6 disappearance for conventional DDGS (95%) was the highest (P < 0.05), wheat bran and soybean hulls were intermediate (47-48%), PKM was low (24%), and soybean meal and canola meal were very low (3-5%). In Experiment 2, there was a significant ingredient × phytase interaction (P < 0.05). Phytase inclusion at both 1,000 and 1,800 U/kg resulted in a significant improvement (P < 0.05) in InsP6 disappearance for RB; however, only the addition of 1,800 U/kg resulted in an increase in InsP6 disappearance for WM. The addition of 1,800 U/kg phytase increased the InsP6 disappearance from 58 to 74% for WM and from 26 to 53% for RB. These results suggest the precision-fed rooster assay can be used to evaluate phytic acid disappearance in plant-based feed ingredients and the assay was able to detect a significant effect of 1,800 U/kg of exogenous phytase on phytic acid disappearance for WM and RB.

Metabolizable energy and amino acid digestibility in spray-dried animal plasma using broiler chick and precision-fed rooster assays.

Four experiments were conducted to determine ME and amino acid (AA) digestibility of spray-dried animal plasma (SDAP) and soybean meal (SBM). The 48-h precision-fed adult rooster assay was used in 2 experiments; TMEn and standardized AA digestibility were determined using conventional and cecectomized roosters, respectively, 50 weeks of age and weighing approximately 2,200 g. Eight individually-caged roosters (4 per diet) were fasted for 26 h, then precision-fed 30 g of SDAP mixture (containing 50% corn) or SBM mixture (containing 50% corn). The TMEn and AA digestibility for SDAP and SBM were calculated by the difference procedure. The TMEn for SDAP was greater (P < 0.05) than SBM (3,743 and 2,669 kcal/kg DM, respectively). Similarly, mean AA digestibility of SDAP was greater (P < 0.05) than SBM (94 and 86%, respectively). Two assays were conducted using Ross male broilers to determine AMEn and apparent (AIAAD) and standardized (SIAAD) ileal AA digestibility of SDAP and SBM. A 3 × 2 factorial arrangement of treatments was used to determine AMEn; 126 chicks (6 replicate pens of 7 chicks) were fed a corn-SBM-based reference diet, a diet containing 30% SDAP, or a diet containing 30% SBM from d 7 to 10 and 18 to 21. A 2 × 2 factorial arrangement of treatments was used to determine AIAAD and SIAAD; 168 chicks (12 replicate pens of 7 chicks) were fed a semi-purified diet containing 25% SDAP or a semi-purified, isonitrogenous diet containing 41% SBM from d 7 to 10 and 18 to 21. The AMEn for SDAP was greater (P < 0.05) than SBM at d 10 (3,851 and 2,089 kcal/kg DM, respectively) and d 21 (4,239 and 2,849 kcal/kg DM, respectively). The second assay showed an increase (P < 0.05) in AIAAD and SIAAD for SDAP compared with SBM at d 10 (mean SIAAD for SDAP and SBM were 96% and 84%, respectively) and d 21 (97% and 87%, respectively). Regardless of assay or age, these results indicate SDAP is a highly digestible feed ingredient with high ME and AA digestibility.

Estimation of factors associated with the occurrence of white striping in broiler breast fillets.

Broiler breast fillets are sometimes characterized grossly by white parallel striations in the direction of the muscle fibers, and the condition is referred to as white striping. Depending on the severity of white striping, fillets can be classified as normal (NORM), moderate (MOD), or severe (SEV). The present study was intended to determine the factors associated with the occurrence of white striping in broiler breast fillets. Broiler birds (59 to 63 d) of 4 different commercial high-yielding strains (both males and females) fed with industrial type or phase-feeding regimens, were processed and ready-to-cook carcass weight was recorded. The carcasses were deboned at either 4 or 6 h postmortem. Fillets were scored for the degree of white striping at 24 h postmortem, and dimensions of fillets (length, width, cranial thickness, and caudal thickness), pH, color (L*, a* and b* values), cook loss, and Meullenet-Owens razor shear energy (MORSE) values were determined. About 55.8% of the birds used in the study showed some degree of white striping with MOD and SEV categories as 47.5 and 8.3%, respectively. Higher degrees of white striping were significantly (P < 0.05) related to higher cranial fillet thickness and ready-to-cook weights. The occurrence of SEV degrees of white striping was accompanied with increased b* values or yellowness of the meat. The growth differences in strains could influence the incidence of this condition, but feeding regimens and chill hour during processing did not. In addition, the degree of white striping did not show any significant (P > 0.05) relationship between various meat quality parameters such as pH, L*, a*, cook loss, and MORSE. In conclusion, the results of this study suggest that there is a greater chance of higher degrees of white striping associated with heavier birds, but the condition is not related to any major changes in cooked meat quality.

Phase feeding in a big-bird production scenario: effect on growth performance, yield, and fillet dimension.

Phase feeding (PF) has been effective at maintaining broiler growth while reducing production cost, but the effect on different broiler strains and sex has not been assessed. An experiment was conducted using 4 commercial broiler strains grown up to 63 d of age (n = 1,440), comparing a PF approach to an industry-type diet. At d 17, birds began either the industry or PF regimen. The industry regimen consisted of average industry nutrient levels with periods from 17 to 32 d, 32 to 40 d, 40 to 49 d, and 49 d to the end of trial. For PF, diets were prepared that contained Lys, sulfur amino acids, and Thr levels matching the predicted requirements for birds at the beginning (high nutrient density) and end (low nutrient density) of PF. Pelleted high and low nutrient density diets were blended to produce rations containing amino acid levels that matched the predicted PF requirements over 2-d intervals. Weight gain, feed intake, and feed efficiency were calculated through d 58. Birds were commercially processed at 59, 61, or 63 d; yield and fillet dimensions were measured. Phase feeding did not effect weight gain or feed intake of broilers during the overall growth period (17-58 d). For most strains, PF did not effect final BW, yield, or fillet dimensions. However, strain and sex had greater effects on growth performance, yields, and fillet dimensions. Strains B and D had greater breast yield than strains A and C. Reduced feed costs ($0.01 to $0.04 per kilogram of gain, depending on strain) were observed for all strains with PF for the overall growth period (17-58 d). Therefore, potential savings on feed costs are possible for all strains used in this study with the incorporation of the PF regimen.

Phase feeding in a small-bird production scenario: effect on growth performance, yield, and fillet dimension.

Phase feeding (PF) has been effective at maintaining broiler growth while reducing production cost, but the effect on different broiler strains grown in a small-bird production scenario has not been assessed. Three strains of commercial broilers were fed a diet containing average industry nutrient levels from 0 to 18 d. From 18 to 32 d, birds were fed either diets with average industry nutrient levels or diets with phased levels of amino acids. For PF, diets were prepared that contained Lys, sulfur amino acids, and Thr levels matching the predicted requirements for birds at the beginning (high nutrient density) and end (low nutrient density) of PF. Pelleted high and low nutrient-density diets were blended to produce rations containing amino acid levels that matched the predicted PF requirements over 2-d intervals, and diets were switched every other day during PF. Treatments were replicated in 6 pens; each pen contained 15 males and 15 females. Weight gain, feed intake, and feed efficiency were calculated. All birds were commercially processed; yield and fillet dimensions were calculated. Differences among strain BW were noted on d 0, 18, 32, and at processing. Males weighed more than females on d 18 (excluding strain C), 32, and the day of processing. Weight gain was affected by strain (P < 0.05) but not by feeding regimen in the overall growth period (18-39 d). Feed efficiency was improved by PF in strains B and C during the overall growth period. Fillet yield was improved with PF for strain B, and there were no significant differences between PF and industry fillet yields for the other 2 strains. Phase feeding had no effect on fillet dimensions, and there was little effect of strain. These results suggest that different strains may vary in their response to PF, although performance was similar or better in PF birds compared with birds fed the industry diet, regardless of strain.

Small bird programs: effect of phase-feeding, strain, sex, and debone time on meat quality of broilers.

Phase-feeding (PF) has been effective in maintaining broiler growth while reducing production cost, but the effect on different broiler strains grown in a small-bird production scenario has not been assessed. The objective of this study was to evaluate 3 commercial broiler strains typically used in a small-bird production scenario to assess the effect of various debone times and PF on yield and meat quality. Birds (n = 1,080) were fed either diets with average industry nutrient levels or diets with phased levels of amino acids. In total, 540 birds were commercially processed at 40 and 42 d of age. Breast fillets were harvested at 2, 4, and 6 h postmortem (PM). Muscle pH was measured at the time of debone and fillet dimensions, instrumental color (L*, a*, and b*), and pH were measured at 24 h PM. Fillets were cooked to 76°C and cook loss was calculated, followed by Meullenet-Owens Razor shear (MORS) analysis. Phase-feeding, strain, and sex had little effect on fillet yield, but deboning at 2 h PM resulted in a higher fillet yield compared with that of later debone times. Strain, sex, and debone hour had significant effects on fillet dimensions, with strain A producing longer and wider fillets than strains B and C. Males had larger fillets than females (longer and wider), whereas deboning early resulted in significantly thicker fillets compared with those of later deboning. There were no differences in fillet dimensions due to PF, however, uniformity was improved. The PF treatment did not affect pH, color, cook loss, or MORS energy. Deboning at 2 h PM resulted in higher MORS energy, indicating decreased tenderness in 2 of the strains, whereas in one strain, tenderness was not affect by debone time. Results of this study suggest PF does not adversely affect yield or meat quality of broilers in small-bird programs but strain, sex, and debone time can affect quality. Results also suggest that strain can effect tenderness of breast fillets when deboned prerigor.

Big-bird programs: Effect of strain, sex, and debone time on meat quality of broilers.

The industry trend toward early deboning of chickens has led to the need to explore the effect on meat quality, including the effects of strain and sex. An experiment was conducted using broilers of 4 different high-yielding commercial strains chosen because of their common use in big-bird production. Of each strain, 360 birds were commercially processed at 59, 61, and 63 d of age in 2 replicates per day. Breast fillets were harvested at 2, 4, and 6 h postmortem (PM). Muscle pH and instrumental color (L*, a*, and b*) were measured at the time of deboning and at 24 h PM. Fillets were cooked to 76°C and cook loss was calculated, followed by Meullenet-Owens razor shear (MORS) analysis. Muscle pH significantly decreased over time as aging before deboning increased. Furthermore, L* values significantly increased as aging time increased, with the fillets deboned at 6 h PM having the highest L* value, followed by 4 h, and then 2 h PM. After 24 h, the fillets deboned at 6 h still had the highest L* compared with those deboned at 2 or 4 h PM. Fillets from strain B had the highest L* values. Fillets deboned at 2 h PM had significantly higher cook losses and MORS energy (indicating tougher fillets) than fillets deboned at 4 or 6 h PM, but there was no difference in cook loss due to strain at any deboning time. Fillets deboned at 4 h PM also had higher MORS energy than fillets deboned at 6 h PM, and differences in MORS energy among the strains were observed at 4 h PM. There was no difference in instrumental color values or cook loss due to sex. However, fillets of males had significantly greater MORS energy (tougher fillets) when deboned at 2, 4, and 6 h PM than those of females. Results of this study suggest that deboning time, sex, and strain can affect meat quality in big-bird market programs.

Performance, livability, and carcass yield of slow- and fast-growing chicken genotypes fed low-nutrient or standard diets and raised indoors or with outdoor access.

Two experiments were conducted to assess the effect of genotype, production system, and nutrition on performance and livability of meat chickens for niche markets. Slow-growing (SG) and fast-growing genotypes (FG) were raised for 91 and 63 d, respectively, in experiment 1 (females) or 84 and 56 d, respectively, in experiment 2 (males). In each trial, SG were placed before FG to achieve a similar BW at processing. In experiment 1, each genotype was assigned to 8 pens of 20 birds each, with 4 pens within each genotype raised indoors in a conventional research facility or in a small facility with outdoor access. All birds were fed a low-nutrient diet. In experiment 2, genotype assignment to pens was as in experiment 1; however, 4 pens within each genotype were fed a low-nutrient diet or a conventional diet, and birds were raised indoors. Birds were gait-scored and commercially processed; legs were examined for tibial dyschon-droplasia lesions and scanned for bone mineral density. In experiment 1, FG gained more weight than SG (P < 0.05) even though they were placed later. Outdoor access increased feed intake, and feed efficiency was poorer (P< 0.05). Fast-growing genotypes had higher breast meat yield, whereas SG had higher wing and leg yields (P < 0.05). In experiment 2, the low-nutrient diet reduced (P< 0.05) gain of the SG; FG increased feed intake of the low-nutrient diet such that their gain was unaffected (P> 0.05). For FG, the low-nutrient diet resulted in a poorer (P < 0.05) feed efficiency. Although weight gain of the FG was maintained on the low-nutrient diet, breast yield was reduced (P < 0.05). Genotype affected bone health in both experiments, with SG having better gait scores and less tibial dyschondroplasia (P < 0.05). Outdoor access and the low-nutrient diet also resulted in better gait score (P < 0.05). These data indicate differences among genotypes and provide information about the efficiency and potential for alternative poultry systems.

Sensory attributes of slow- and fast-growing chicken genotypes raised indoors or with outdoor access.

Consumer interest in free-range and organic poultry is growing. An experiment was conducted to assess the impact of alternative genotype and production systems on the sensory attributes of chicken meat. Specifically, a slow-growing genotype and a fast-growing genotype were raised for 91 and 63 d. The slow-growing birds were placed before the fast-growing birds to achieve a similar final BW at processing. Each genotype was assigned to 4 pens of 20 birds each and raised in indoor floor pens in a conventional research facility; each genotype was also assigned to 4 floor pens in a small facility with outdoor access. The diet was formulated to be low in energy and protein for slow growth. Birds were commercially processed and deboned at 4 h postmortem. A descriptive analysis of breast and thigh meat was conducted on all treatments by a trained descriptive panel. A consumer analysis was also conducted on the breast and thigh meat from only 2 treatments: slow-growing birds raised with outdoor access and fast-growing birds raised indoors. A descriptive analysis indicated that the breast meat from birds with outdoor access was more cohesive than the meat from indoor birds (P < 0.05). There were no significant differences for most basic tastes; however, both the breast meat and thigh meat of the fast-growing birds tasted saltier than that of the slow-growing birds (P < 0.05). Meat of the slow-growing birds had more dark meat fat flavor than that of the fast-growing birds (P < 0.05). Results from the consumer panel showed no significant differences in overall liking, appearance, texture, or flavor of the breast meat or thigh meat. Just-About-Right distributions of consumer responses did not vary between slow-growing birds with outdoor access and fast-growing birds raised indoors for most attributes; however, more panelists found the breast meat of slow-growing birds with outdoor access too dry (P < 0.05). Although a descriptive panel detected some differences in texture and flavor among treatments, the consumer panel did not indicate differences in liking between conventional and specialty products.

Meat quality of slow- and fast-growing chicken genotypes fed low-nutrient or standard diets and raised indoors or with outdoor access.

Consumer interest in free-range and organic poultry is growing. Two concurrent experiments were conducted to assess 1) the impact of alternative genotype and production system and 2) the impact of genotype and diet on meat quality of chickens for specialty markets. Specifically, a slow-growing genotype (slow) and a fast-growing genotype (fast) were raised for 91 and 63 d (females), respectively, or 84 and 56 d in the case of the second trial (males). In each trial, the slow birds were placed before the fast birds to achieve a similar final BW at processing. Each genotype was assigned to 4 pens of 20 birds each and raised in indoor floor pens in a conventional poultry research facility; each genotype was also assigned to 4 floor pens in a small facility with outdoor access. A low-nutrient diet was used, formulated for a slower rate of production. Birds were commercially processed and deboned at 4 h postmortem. In the second trial, the diets compared were a conventional diet that met NRC requirements or the low-nutrient diet, and all birds were raised indoors. There was an interaction between genotype and production system for the color (b*; P < 0.05). The meat and skin of the slow birds became more yellow when the birds had outdoor access; however, this did not occur when the fast birds had outdoor access. The breast meat of the slow birds had more protein and alpha-tocopherol (P < 0.05) than the fast birds and half the amount of fat (P < 0.05). In addition, the meat of the outdoor birds had more protein than the indoor birds (P < 0.05). The slow birds had poorer water-holding capacity but were more tender than the fast birds (P < 0.05). The type of diet had little impact on meat quality. These data indicate that meat quality differences exist between genotypes with different growth rates and raised in alternative production systems.

Evaluation of the efficacy of vitamin D3 or its metabolites on thiram-induced tibial dyschondroplasia in chickens.

Two trials were conducted to determine if thiram-induced tibial dyschondroplasia (TD) in chickens was linked to a vitamin D deficiency and calcium homeostasis dysregulation, and whether feeding vitamin D fortified diets may prevent it. Day-old chickens were given grower diets containing different vitamin D products throughout the experiment until necropsy on day 16. Half of the birds in each feed group received thiram at levels of 100 ppm (trial 1) or 50 ppm (trial 2) between days 7-9 to induce TD. The birds were weighed, bled, and euthanized to determine TD incidences and severity by examining the growth plates. Tibial bones were used to measure biomechanical strength and ash content. Blood concentrations of 25-hydroxyvitamin D, Ca, P, alkaline phosphatase, and creatine kinase were measured in serum that showed no differences between different groups. Thiram reduced body weight and induced TD regardless of any vitamin D treatment to the same extent as untreated birds.

Homocysteine remethylation in broilers fed surfeit choline or betaine and varying levels and sources of methionine from eight to twenty-two days of age.

Experiments were conducted to assess the effect of surfeit choline (CHOL) or betaine (BET) on growth performance and homocysteine (HCY) remethylation of young broilers fed graded levels of DL-Met (DLM) or 2-hydroxy-4-(methylthio) butanoic acid (HMB). In Experiment 1, a corn-peanut meal diet deficient in Met (0.25% digestible) and Cys (0.28% digestible) was fed; treatments were formulated to contain graded levels (0, 0.04, or 0.08%) of Met from DLM or 0.04% HMB (adjusted for 88% purity) that were fed in the presence or absence of surfeit isomethyl CHOL (0.25%) or BET (0.28%). In Experiment 2, identical treatments were used, but an additional level of HMB (0.08%) was fed, and the basal diet was adequate in Cys (0.43% digestible). There was no overall effect of CHOL or BET on growth performance in Experiments 1 and 2 (P > 0.05); a significant improvement (P < 0.05) in weight gain and feed efficiency did occur with CHOL and BET addition to the basal diet in Experiment 2. In both experiments, weight gain increased linearly (P < 0.05) with the addition of DLM or HMB. Slope ratio methodology was used to assess HMB efficacy in Experiment 2. In the presence of adequate Cys, HMB efficacy was 81.3%; addition of surfeit BET or CHOL had minimal effect on efficacy. The stable isotope study revealed that CHOL and BET addition to diets deficient in Met and Cys or Met alone increased HCY remethylation. It also showed that CHOL and BET have greater influence on folate-dependent remethylation of HCY (via Met synthase) than on BET-dependent remethylation (via BET-HCY methyltransferase) and that levels of CHOL and BET and type of S amino acid deficiency effect remethylation and HMB efficacy.

Efficacy of an Escherichia coli phytase in broilers fed adequate or reduced phosphorus diets and its effect on carcass characteristics.

Five experiments (EXP) were conducted to assess the efficacy of an Escherichia coli phytase compared with 2 commercially available fungal phytases. In EXP 1 and 2, male broiler chicks were fed experimental diets that included a P-deficient control (0.13% available P; 0.88% Ca) alone or with graded levels of KH(2)PO(4) (0, 0.05, 0.10, or 0.15%) or phytase at levels of 250, 500, 1,000, 2,000, or 4,000 phytase units/kg of E. coli phytase (EXP 1 and 2), fungal phytase 1 (EXP 2), or fungal phytase 2 (EXP 2). In EXP 1 and 2, weight gain and tibia ash (mg/chick and %) responded linearly (P < 0.05) to inorganic P addition. In EXP 2, each level of E. coli phytase released more P than either fungal phytases 1 or 2, whether based on tibia ash weight (mg/chick) or percentage. In EXP 3, 4, and 5, dietary treatments containing adequate or deficient levels of P were fed with or without supplemental E. coli phytase. In EXP 3, weight gain and tibia ash were reduced (P < 0.05) by P deficiency, but gain and tibia ash of chicks fed E. coli phytase (250, 500, or 1,000 phytase units/kg) did not differ (P > 0.05) from that of chicks fed the P-adequate diet. In addition, carcass yield of broilers fed E. coli phytase was not reduced (P > 0.05). In EXP 4, E. coli phytase effectively supported weight gain, tibia ash, breast yield, and leg yield compared with birds fed the P-adequate diet, but clavicle breakage during processing was increased in birds fed E. coli phytase. In EXP 5, E. coli phytase again effectively supported weight gain, and no differences (P > 0.05; compared with the P-adequate diet) were noted for clavicle ash, diameter, or breaking strength. No differences (P > 0.05) in bone breakage during processing were noted among treatments. These results indicate that the addition of E. coli phytase to P-deficient broiler diets improves growth, bone, and carcass performance and is more effective at releasing phytate-bound P than the other phytase products that were tested.

Effect of reciprocating dietary lysine fluctuations on chick growth and carcass yield.

Three experiments (Exp) were conducted to study the effect of reciprocating (i.e., back-and-forth) fluctuations in dietary Lys concentration on growth performance of male broiler chicks. The Lys, CP, and ME concentrations were fluctuated in Exp 1 by varying corn and soybean meal concentrations. Corn-peanut meal diets in Exp 2 and 3 contained a constant calorie-protein ratio, but Lys concentrations were fluctuated by varying supplemental L-Lys x HCl. During 7-d feeding periods from d 8 to 43 posthatch, chicks fed the fluctuating regimen were provided diets with nutrient concentrations arranged in the following order (relative to control diets at any given point): excess-deficient-excess-deficient-adequate. In each Exp, differences in feed intake and gain:feed were observed during the first 7 d. Weight gain was never affected by dietary regimen. Overall, chicks fed the fluctuating regimen showed similar weight gain and feed intakes relative to chicks fed the control regimen. Additionally, efficiency of feed, Lys, CP, and ME utilization over the 35-d growth period of Exp 2 and 3 were not affected by dietary regimen. An increase in carcass yield (dressed, carcass weight as a percentage of live weight) of birds fed the fluctuating regimen was observed, but there were no differences in abdominal fat yield (as a percentage of dressed, carcass weight). These data support the conclusion that reciprocating 7-d periods of nutrient excess and deficiency do not affect overall growth performance of growing chicks.

Meat quality evaluation of minimally aged broiler breast fillets from five commercial genetic strains.

A total of 1,040 birds from 5 common commercial genetic broiler strains were raised and processed to analyze the effect of strain and deboning time on meat quality. The birds were processed at either 6 or 7 wk of age in 4 replications each. Carcasses were deboned at either 2 or 4 h postmortem (PM; n = 52 birds per treatment). Carcass and breast weights were measured on each bird to calculate breast yield. Muscle pH was measured at time of deboning. Fillets deboned at 4 h PM were measured for length, width, and height to evaluate footprint analysis. At 24 h PM, fillets were weighed to calculate drip loss, and color (L*) was also measured. The fillets were then cooked to 76 degrees C, and cook loss was calculated. Fillets were then subjected to shear analysis using the Meullenet-Owens razor shear method where shear energy (N x mm) was calculated to evaluate tenderness. The strains in this study were chosen for differences in yield; therefore, as expected, breast yield was significantly different among strains. Variation in meat quality attributes existed among strains deboned at 2 h PM, but there was no consistent relationship between meat quality and breast yield. However, at 4 h PM, fewer differences among strains existed in meat quality characteristics (tenderness, water holding capacity, and pH). As expected, deboning at 2 h PM resulted in higher shear energy, higher muscle pH, and lower L* value compared with deboning at 4 h PM in all but one strain. However, water-holding capacity was not affected by deboning time at either age interval. Footprint analysis showed that most differences among strains were in heights measured at the fillet midpoint and caudal end. These results suggest that early deboning may affect meat quality of broiler strains differently, resulting in greater variation within the industry.

The use of vitamin A-deficient diets and jugular vein ligation to increase intracranial pressure in chickens (Gallus gallus).

A technique was developed to record intracranial cerebrospinal fluid pressure (iCSFp) in chicks and mature chickens. Using that procedure, 2 methods were found to effect a significant elevation in intracranial pressure: 1) feeding a purified diet to roosters for 40 d containing 25% of the bird's requirement for vitamin A, and 2) ligating both jugular veins in birds. The purified diet significantly reduced plasma retinol levels from 1.080 to 0.046 microg/mL, and iCSFp was significantly elevated from 63.0 to 106.0 mmH2O (P < or = 0.05). Two limitations for using hypovitaminosis A diets were capillary fragility and a cisterna magna that did not develop to the size of that structure in birds of the same age fed control diets with adequate vitamin A content. The second procedure, a reversible surgical technique, showed that within 2.5 h from jugular vein ligation, intracranial pressure rose to 109.7 mmH2O, comparable with levels attained following feeding a vitamin A deficient diet to roosters. Bilateral clamping of the jugular veins overnight resulted in an elevation of iCSFp to 127 +/- 8.86 mmH2O. Results suggest that the chicken may be a useful animal model to investigate intracranial hypertension and its accompanying headaches known to occur in humans.

Evaluation of slower-growing broiler genotypes grown with and without outdoor access: sensory attributes.

Consumer interest in organic and natural poultry production is growing. An experiment was conducted to assess the impact of genotype and outdoor access on sensory attributes of broiler meat. One slow-growing genotype (S), 2 medium-growing genotypes (M1 and M2), and a commercial fast-growing genotype (F) were raised (straight-run) for 81, 67, or 53 d, respectively. The placement dates were staggered to achieve a similar final BW, and each genotype was processed on the same day. Each genotype was assigned to 3 pens of 24 birds each, and all birds were raised in indoor floor pens in a naturally ventilated facility. The S and F genotypes were also assigned to 2 floor pens with outdoor access (during daylight hours) containing 36 birds each. All birds were provided with the same starter, grower, and finisher feeds, and birds were commercially processed. Breast and thigh meat were evaluated for sensory attributes and acceptability by a consumer panel. The M1 and M2 breasts were more tender than other indoor genotypes (P < 0.05); however, all treatments scored "slightly to moderately tender." The thigh meat of the M2 birds was more flavorful than that of S birds (P < 0.05), and the flavor of the S thigh meat was less liked than other indoor genotypes (P < 0.05). Outdoor access did not impact flavor. These data indicate that differences in sensory attributes may exist among genotypes with different growth rates and reared with or without outdoor access.