Multiprotease improves amino acid release in vitro, energy, and nutrient utilization in broilers fed diets varying in crude protein levels.

Low crude protein (CP) diets can reduce nitrogen (N) excretion and costs by increasing N utilization efficiency. Exogenous proteases may further improve protein digestibility in low CP diets. This study first evaluated in vitro the efficacy of a multiprotease on amino acid (AA) release from feedstuffs and broiler feed. Later, a broiler study evaluated the effect of feeding corn-soybean meal diets containing 3 CP levels (17, 19, and 21% CP) with supplementation on top of 0 or 2,400 U/kg multiprotease on chicken growth performance, total tract CP, and ileal AA digestibilities, and energy utilization. Ross 708 male chickens were placed in 42 cages and assigned to 6 treatments resulting from a 3 × 2 factorial arrangement. Three isocaloric basal diets were formulated to reduce CP, but all diets maintained digestible Lys:CP in 5.47% and the same ideal protein profile. Data were analyzed in a completely randomized design. On average, the multiprotease increased (P < 0.05) in vitro free AA release by 27.81% in most feedstuffs evaluated compared to the control. For broiler feed, 1,200 U/g multiprotease addition improved (P < 0.001) in vitro free AA release by 18.90%. This multiprotease showed interaction effects (P < 0.05) on chicken FCR, energy, and CP digestibility. As expected, BW at 24 d, BW gain, and FCR (8-24 d) worsened (P < 0.001) as dietary CP reduced from 21 to 17%, and multiprotease addition did not improve (P > 0.05) these parameters. BW gain decreased by 12.9% when N intake was reduced from 49.32 to 38.49 g/bird. Multiprotease supplementation improved (P < 0.01) AMEn by 71 kcal/kg, CP digestibility from 59.45 to 63.51%, ileal AA digestibility, and DM digestibility from 67.08 to 73.49%, but only in the 21% CP diet. No differences in ileal AA digestibility due to CP level (P > 0.05) were detected, except for Cys digestibility (P < 0.01). In conclusion, low CP diets reduced growth performance and improved N utilization but negatively affected energy utilization efficiency. Exogenous multiprotease supplementation improved AME, AMEn, protein, ileal AA, and DM digestibility in the 21% CP diet without significantly affecting growth performance.

Influence of extruded soybean meal with varying fat and oleic acid content on nitrogen-corrected apparent metabolizable energy in broilers.

High oleic (HO) soybeans may serve as a value-added feed ingredient; providing amino acids and estimating their dietary energy value for broilers is essential. In this study, we determined the apparent metabolizable energy (AME), AME corrected for zero nitrogen retention (AMEn), digestibility, and nitrogen (N) retention of HO full-fat (HO-FF) soybean as compared to solvent-extracted soybean meal (SE-SBM), normal oleic full-fat (NO-FF) and extruded expeller (NO-EE) soybean. A total of 240 Ross-708 male broilers were selected, with 8 replicates per treatment and 6 chicks per cage. The AME and AMEn were estimated using the difference method with a 30% inclusion of test ingredients using a corn-soy reference diet with partial and total excreta collection. The index method with partial excreta collection used titanium dioxide as an inert marker. The same starter diet was provided for all birds for 14 d, followed by the reference and assay diets for the next 6 adaptation days. Total excreta were collected twice a day for 3 d. The AME and AMEn values determined for the HO-FF and NO-FF were higher (P < 0.001) than the NO-EE and SE-SBM. The AME of SE-SBM and NO-EE were similar with both methods, but the AMEn of SE-SBM was lower than the NO-EE only with the partial collection method. The agreement between AME and AMEn values determined by partial and total excreta collection analysis was 98%. Data from the total excreta collection method yielded higher AME and AMEn values (P < 0.001) than those from the partial collection method. In summary, HO-FF and NO-FF soybean meals had similar AME and AMEn values. The HO-FF soybean had 39 and 24% higher AME and AMEn than SE-SBM. Hence, high oleic full-fat soybean meal could serve as a valuable alternative feed ingredient to conventional SE-SBM meals in broiler diets, providing additional energy while providing amino acids and more oleic acid to enrich poultry meat products.

Effects of high oleic full-fat soybean meal on broiler live performance, carcass and parts yield, and fatty acid composition of breast fillets.

The effects of high oleic oil full-fat (HO-FF) soybean meal (SBM) on broiler meat quality could lead to value-added food products. This experiment evaluated the effects of dietary normal oleic extruded expelled (NO-EE), normal oleic full-fat (NO-FF), or HO-FF SBM on live performance, carcass and parts yield, and breast fatty acid composition. Diets were formulated to be isoenergetic and isonitrogenous. A total of 540 Ross-708 male broilers were raised on floor pens with 18 broilers/pen and 10 replicates/treatment. Data were analyzed in a completely randomized design. Chickens were fed with a starter (0-14 d), grower (15-35 d), or a finisher diet (36-47 d) up to 47 d. Chickens were weighed at 7, 14, 35, and 47 d. At 48 d, 4 broilers per pen were processed. Breast samples were collected and evaluated for quality and fatty acid content. Broilers fed diets with NO-EE were heavier (P < 0.05) than chickens fed diets with full-fat SBM (NO-FF and HO-FF) at d 7, 14, 35 while feed conversion ratio (FCR) of NO-EE was best (P < 0.05) at 7 and 47 d. Carcass yield was also higher for broilers fed NO-EE than the other treatments. Diet did not affect parts yield, breast meat color, cooking, drip loss, white stripping, or SM quality parameters. More breast fillets without wooden breast (score 1) were observed (P < 0.05) for NO-FF than the other 2 treatments. The breast meat fatty acid profile (g fatty acid/100 g of all fatty acids) was significantly affected (P < 0.001) by diet. Broilers fed the HO-FF SBM diet had 54 to 86% more oleic acid, 72.5% to 2.2 times less linoleic acid, and reduced stearic and palmitic acid levels in the breast meat than NO-FF and NO-EE. In conclusion, feeding HO-FF to broilers enriched the oleic acid content of their breast meat while reducing the saturated fatty acid content relative to the NO-FF and NO-EE treatment groups.

Egg Quality, Yolk Fatty Acid Profiles from Laying Hens Housed in Conventional Cage and Cage-Free Production Systems in the Andean Tropics.

Egg consumers worldwide have increased their concerns about laying hens' welfare and its impact on final egg product quality. This study compared the egg quality parameters under the conventional cage (CC) and cage-free (CF) egg production systems in the tropics. The study was conducted on a commercial farm in Colombia using Hy-Line Brown pullets, reared under the same conditions for the first 15 wks. At 16 wks, the hens were distributed into two housing systems, CC and CF, on the same farm. The hens were fed the same diet for each phase in both systems and feed intake varied slightly. Egg samples were collected every six wks, from 22 to 82 wks of age. A total of 3960 eggs were analyzed at 11 sampling times. Parameters such as albumen height, egg weight, yolk color, eggshell thickness, eggshell strength, and Haugh units were determined using a DET-6000 machine. At 22 and 82 wks, screening for Salmonella spp. status was conducted using environmental and egg samples. Additionally, at 34, 64, and 82 wks, yolk samples were obtained for fatty acid profiles and crude protein (CP) analysis. The data were analyzed in a completely randomized block design with repeated measures (11 times): mean separation by Student's t-test yolk pigmentation, Haugh Units, and albumen height (p < 0.001) were higher in the CF compared with the CC between 38 and 69 wks of age, and eggs at 63 and 82 wks (p < 0.05) were heavier in the CF compared to the CC. Likewise, eggs from the CC had better eggshell strength from 57 to 82 wks. In the egg yolk fatty acid profile at the 34th wk, the pentadecanoic, palmitic, and heptadecanoic acids had higher concentrations in the CF systems than the CC. At the 64th wk, the egg yolk fatty acids-lauric, myristic, and heptadecanoic-had higher concentrations in the CF; likewise, at the 82nd wk, egg yolks from the CC had higher concentrations of lauric, heptadecanoic, and nervonic fatty acids than the CF. The eggs and environmental samples were negative for Salmonella spp. throughout the whole production phase. These results indicated that the production system might impact internal and external egg quality measures, potentially due to various stressors, including environmental factors or behavior restrictions.

Effect of Environmental and Farm-Associated Factors on Live Performance Parameters of Broilers Raised under Commercial Tropical Conditions.

Although temperature, relative humidity, and farm-associated factors are known to affect broiler live performance, data about the impact of these variables under commercial operations are still scarce. This study aimed to evaluate the effect of temperature, relative humidity, a thermal humidity index, management, and farm-associated factors on BW, BW gain, feed conversion ratio (FCR), and mortality of broilers raised to 35 d under commercial tropical conditions. The data analyzed included performance records of Ross 308 AP broiler flocks placed between 2018 and 2020. Environmental monitoring information was obtained from electronic sensors that captured data hourly from 80 flocks in 29 farms. Farm-associated factors were gathered using a survey of 86 farms. Three data analyses were conducted in parallel. Correlation analyses, one-way ANOVA, and machine learning techniques were employed. Results indicated that BW and BW gain were reduced, and FCR worsened (p < 0.001) up to 21 d when chickens were mainly exposed to temperatures 2.5 °C lower than the recommended optimums for each age period. At the same time, mortality at 28 and 35 d increased. In conclusion, all farm-associated factors affected chicken live performance. Variable importance analysis indicated that performance results at 14 and 21 d were significant to predict BW at 35. At the same time, sex, distance between the hatchery and farm, and farm altitude accounted for the most significant contributions from the farm-associated factors.

Standardized ileal amino acid digestibility of high-oleic full-fat soybean meal in broilers.

High-oleic (HO) soybean may serve as a value-added feed ingredient to enrich poultry meat due to its fatty acid content. However, the amino acid (AA) nutrient digestibility of soybean meal (SBM) made from these soybeans has yet to be determined. The objective of this study was to determine apparent ileal AA digestibility (AID) and standardized ileal AA digestibility (SID) of high-oleic full-fat (HO-FF) SBM compared to normal oleic full-fat (NO-FF), normal oleic extruded expeller (NO-EE), and solvent-extracted SBM (SE-SBM) in broilers. A nitrogen-free basal diet (NFD) was fed to 1 treatment group with 10 chicks/cage to determine basal endogenous losses (BEL). Titanium dioxide was used as an inert marker. The test diets contained 57.5% of the basal NFD and 42.5% of 1 of the 4 soybean sources. A total of 272 Ross-708 male broilers were placed in 40 battery cages with 5 treatments and 8 replicates per treatment. A common starter diet was provided to all the chickens for 14 d. Experimental diets were provided as a mash for 9 d before sample collection. Chickens were euthanized with CO2 on d 23, and contents of the distal ileum were collected, frozen, and freeze-dried. The BEL were similar to the values found in the literature. At d 23, broilers fed the SE-SBM had the highest body weight gain and best FCR compared to chickens fed the HO-FF and NO-FF treatments (P < 0.001). Broilers fed the SE-SBM and NO-EE experimental diets had (P < 0.001) higher apparent ileal AA digestibility and AA SID than broilers fed the HO-FF and NO-FF treatments. In conclusion, the SID of AA from HO-FF is similar to the digestibilities of other full-fat soybeans found in the literature and is lower than that of NO-EE and SE-SBM.

Data Analytics of Broiler Growth Dynamics and Feed Conversion Ratio of Broilers Raised to 35 d under Commercial Tropical Conditions.

Data collection is standard in commercial broiler production; however, growth modeling is still a challenge since this data often lacks an inflection point. This study evaluated body weight (BW) dynamics, feed intake, BW gain, feed conversion ratio (FCR), and mortality of broiler flocks reared under commercial tropical conditions with controlled feeding to optimize FCR. The data analyzed included performance records of 1347 male and 1353 female Ross 308 AP broiler flocks with a total of 95.4 million chickens housed from 2018 to 2020. Decision trees determined high- and low-feed-efficiency groups using FCR at 35 d. Logistic, Gompertz-Laird, and von Bertalanffy growth models were fitted with weekly BW data for each flock within performance groups. The logistic model indicated more accurate estimates with biological meaning. The high-efficiency males and females (p < 0.001) were offered less feed than the low-efficiency group and were consistently more efficient. In conclusion, greater feeding control between the second and the fourth week of age, followed by higher feed allowance during the last week, was associated with better feed efficiency at 35 d in males and females. Additionally, models demonstrated that a reduced growth rate resulted in heavier chickens at 35 d with better feed efficiency and greater BW gain.

Effects of corn hardness and drying temperature on digestibility of energy and nutrients in diets fed to growing pigs.

Two experiments were conducted to test the hypothesis that corn kernel hardness and drying temperature influence the ileal digestibility of starch and amino acids (AA), as well as apparent total tract digestibility (ATTD) of gross energy (GE) and total dietary fiber (TDF) in diets for growing pigs. Two corn varieties with average or hard endosperm were grown and harvested under similar conditions, and after harvest, each variety was divided into 2 batches that were dried at 35 and 120 °C, respectively. Therefore, four batches of corn were used. In experiment 1, 10 pigs (67.00 ±â€…2.98 kg) with a T-cannula installed in the distal ileum were allotted to a replicated 5 × 5 Latin square design with 5 diets and 5 periods giving 10 replicates per diet. A nitrogen-free diet and four diets containing each source of corn as the only AA source were formulated. Results indicated that neither variety of corn nor drying temperature influenced apparent ileal digestibility of starch in the grain. The standardized ileal digestibility of most AA was less (P < 0.05) in corn dried at 120 °C compared with corn dried at 35 °C resulting in concentrations of most standardized ileal digestible AA being less (P < 0.05) in corn dried at 120 °C than in corn dried at 35 °C. In experiment 2, 40 pigs (20.82 ±â€…1.74 kg) were housed in metabolism crates and allotted to 4 diets with 10 replicate pigs per diet. The four corn-based diets used in experiment 1 were also used in experiment 2. Feces and urine were collected using the marker-to-marker approach with 5-d adaptation and 4-d collection periods. Results indicated that diets containing hard endosperm corn had greater (P < 0.05) ATTD of TDF than diets containing average endosperm corn. The ATTD of GE in hard endosperm corn was also greater (P < 0.05), and concentrations of digestible energy and metabolizable energy in hard endosperm corn were greater (P < 0.01) than in average endosperm corn. Diets containing corn dried at 120 °C had greater (P < 0.05) ATTD of TDF compared with diets containing corn dried at 35 °C; however, drying temperature did not influence the ATTD of GE. In conclusion, endosperm hardness did not influence the digestibility of AA and starch; however, drying corn at 120 °C reduced digestible AA concentrations. Hard endosperm corn had greater ATTD of GE and TDF, but drying temperature did not influence energy digestibility.

Drying temperatures and corn varieties that inherently differ in kernel hardness, virtuousness, and protein solubility index may influence nutrient digestibility in corn. However, information about interactive effects of corn source (i.e., endosperm hardness) and drying method on nutrient digestibility is limited. Therefore, two experiments were conducted to test the hypothesis that corn source and drying temperature influence energy and nutrient digestibility in corn. Two corn varieties (i.e., average or hard endosperm) were planted in plots with similar soil and similar agronomic conditions and harvested in the same week. Both corn sources were dried at 35 °C or 120 °C. Results indicated that endosperm hardness did not influence the apparent ileal digestibility of starch or standardized ileal digestibility (SID) of amino acids (AA) in pigs; however, values for SID of most AA in corn dried at 120 °C were less than in corn dried at 35 °C. Hard endosperm corn also had greater apparent total tract digestibility of gross energy and total dietary fiber than corn with average endosperm, but drying temperature did not influence energy digestibility. Further research is needed to determine the optimum drying temperature and corn variety to maximize nutritional value in corn.

Effects of full-fat high-oleic soybean meal in layer diets on nutrient digestibility and egg quality parameters of a white laying hen strain.

This study was conducted to understand the impact of including full fat high-oleic soybean meal in layer hen diets on nutrient digestibility and added nutritional value in eggs. Forty-eight layers (∼36 wk old) were randomly assigned to one of 4 isonitrogenous (18.5% crude protein) treatment diets with 12 replicate birds per treatment in a 3-wk study. Treatments were 1) solvent extracted defatted soybean meal + corn diet, 2) dry extruded defatted soybean meal + corn, 3) full-fat soybean meal + corn, 4) high-oleic full-fat soybean meal + corn diet. Apparent ileal digestibility of crude fat (CF) and crude protein (CP) were determined using celite (∼2%) as an indigestible marker. Tibia strength and egg quality parameters (egg weight, shell strength, Haugh unit, shell color, and yolk color) were recorded during the study. Fatty acid profiles, including the monounsaturated fatty acid, oleic acid (C18:1, cis), in eggs and adipogenic tissue (liver, muscle, and fat pad) were measured using gas chromatography (GC-FID). Digestibility values of CF ranged from 71 to 84% and CP varied from 67 to 72% for treatment diets, with treatment mean values being no different (P > 0.05) between treatment diets. No differences between treatment diets in tibia strength or egg quality parameters (egg weight, shell strength, and Haugh unit) were observed (P > 0.05) except for yolk color. Similarly, there were no differences in the total lipids in egg yolk (P > 0.05) between treatment diets. However, oleic acid percentage of total lipid in egg and tissue was significantly higher (P < 0.001) in hens given the high-oleic full-fat soybean meal diet than in other treatment groups. No difference was observed in oleic acid percentage of total lipid in egg between the other 3 treatment diets (P > 0.05). Overall, the results exhibited that the eggs and tissue of layer hens fed the full-fat high-oleic acid soybean meal diet were higher in oleic acid while the CF and CP digestibility remained similar to the digestibility of the other diets.

Corn kernel hardness, drying temperature and amylase supplementation affect live performance and nutrient utilization of broilers.

Drying temperature (DT) of corn can influence its nutritional quality, but whether this is influenced by endosperm hardness is not clear. Two parallel experiments were conducted to investigate the effects of 2 yellow dent corn hybrids with average and hard kernel hardness, dried at 3 temperatures (35, 80, and 120°C), and 2 supplementation levels of an exogenous amylase (0, 133 g/ton of feed) on live performance, starch and protein digestibility, and energy utilization of Ross 708 male broilers. Twelve dietary treatments consisting of a 2 × 3 × 2 factorial arrangement were evaluated using 3-way ANOVA in a randomized complete block design. In Experiment 1, a total of 1,920 male-chicks were randomly allocated to 96 floor pens, whereas 480 day-old chicks were distributed among 96 cages for Experiment 2. At 40 d, interaction effects (P < 0.05) were detected on BWG, FCR, and flock uniformity. Supplementation with exogenous amylase resulted in heavier broilers, better FCR and flock uniformity, only in the diets based on corn dried at 35°C. Additionally, interaction effects were observed on FCR due to kernel hardness and DT (P < 0.01), kernel hardness and amylase supplementation (P < 0.001), and DT and amylase supplementation (P < 0.05). Exogenous amylase addition to the diets based on corn with an average hardness improved FCR up to 2 points (1.49 vs. 1.51 g:g) whereas there was no effect of amylase on FCR of broilers fed diets based on corn with hard endosperm. Total tract retention of starch was increased (P < 0.05) in broilers fed diets based on corn with average kernel hardness compared to hard kernel. Corn dried at 80 and 120°C had up to 1.21% points less starch total tract retention than the one dried at 35°C. Supplementing alpha-amylase resulted in beneficial effects for broiler live performance, energy utilization, and starch total tract digestibility results. Treatment effects on starch characteristics were explored. Corn endosperm hardness, DT and exogenous amylase can influence the live performance of broilers. However, these factors are not independent and so must be manipulated strategically to improve broiler performance.

Effects of amino acid levels during rearing on Cobb 500 slow-feathering broiler breeders: 2. Reproductive performance.

Crude protein and amino acid (AA) content in rearing diets affect body composition and reproductive performance. This study evaluated the effects of 4 dietary AA levels during rearing on BW, egg production and composition, fertility, hatchability, and embryo mortality up to 65 wk of age on Cobb 500 slow-feathering (SF) broiler breeders. The treatments consisted in 80% (low-AA), 90% (moderate-AA), 100% (standard-AA), and 110% (high-AA) of the AA recommendations for Cobb 500 SF pullets from 5 to 24 wk. AA was guided by an ideal protein profile based on digestible Lys. A total of 1,360 pullets and 288 Cobb MV cockerels were randomly placed in 16 pullets and 16 cockerel floor-pens. At 22 wk, 1,040 females and 112 males were transferred into 16-floor pens in a laying house. BW increased linearly (P < 0.01) as AA augmented at 25, 36, and 40 wk. No effects (P > 0.05) at the onset of lay were observed. Moderate-AA and standard-AA resulted in the best hen-housed egg production (HHEP) at 65 wk with 174.3 and 176.5 eggs, respectively. The optimum level of AA for HHEP at 65 wk was estimated (P < 0.001) in 96.7% and 94.7% by the quadratic and broken line models, respectively. Overall, the lightest egg weight (P = 0.022) was obtained with 89%AA during rearing, and the heaviest eggs (P < 0.001) were found at 54 wk. Response surface regression indicated linear effects on albumen and yolk percentages (P < 0.01) increasing and decreasing, respectively, as AA levels augmented; consequently, AA had a negative linear effect on Y:A ratio (P = 0.004) with quadratic effects (P < 0.01) of age (R2 = 0.92). No statistical effect of treatments was observed in fertility (P > 0.05), but AA had a quadratic effect (P = 0.046) on hatchability up to 50 wk of age with 97% as optimum, and decreased linearly (P = 0.004) from 51 to 65 wk. A few effects of treatments (P < 0.05) on embryo mortality were observed. In conclusion, AA levels during rearing affect broiler breeder reproductive performance.

Effects of amino acid levels during rearing on Cobb 500 slow-feathering broiler breeders: 1. Growth and development.

Adequate pullet nutrition is essential to reach BW and suitable body composition for reproduction. An experiment was conducted to determine the effects of 4 dietary amino acid (AA) levels on BW, flock uniformity, body conformation, organ, leg, and feathering development of broiler breeder pullets during the rearing phase from 5 to 24 wk. A total of 1,360 Cobb-500 slow-feathering (SF) pullets were randomly placed in 16-floor pens with 85 females per pen. Diets with corn, soybean meal, and wheat-midds were formulated without protein restriction maintaining minimum ratios between essential AA and Lys on a digestible (dig) ideal basis. Treatments consisted of 4 dietary AA levels with 80% (low-AA), 90% (moderate-AA), 100% (standard-AA), and 110% (high-AA) of the Cobb-Vantress recommendations guided by dig Lys using balanced protein. Up to 4 wk, all pullets were fed a common starter crumble diet. Grower and developer mash diets were fed to pullets from 5 to 15 wk and from 16 to 24 wk, respectively. Pullets fed standard-AA and high-AA diets were heavier (P < 0.001) than those fed low-AA diets at 10, 15, and 20 wk of age. High-AA diets resulted in better (P = 0.040) flock uniformity at 10 wk. Pullets fed a high-AA diet had the highest (P = 0.041) relative breast weight at 20 wk of age and the lowest (P = 0.044) deposits of abdominal fat at 15 wk of age. Fleshing increased (P < 0.05) as AA content rise in the diet, while the relative shank length (P < 0.001) and the number of wing juvenile feathers (P = 0.004) decreased. Pullets fed the lowest dietary AA level had the longest (P = 0.007) small intestine relative to BW at 10 wk of age, but a smaller (P = 0.001) liver than those fed moderate and standard-AA diets at 20 wk of age. Dietary AA levels have important effects on pullet BW, fleshing, and organ development during rearing with potential reproductive performance impacts.

Identification of reliable reference genes for expression studies in the magnum of laying hens housed in cage and cage-free systems.

Stress factors during poultry production can evoke changes in gene transcription and protein synthesis in the hen oviduct and could affect the internal and external egg quality. Studies of relative gene expression require the identification of the most stable reference genes for the quantitative polymerase chain reaction (qPCR) to investigate the reproductive tissues' response in laying hens kept in different production systems. The objective of this study was to determine the most stable reference genes of the magnum tissues of laying hens housed in two different production systems. Hy-Line Brown hens were reared under the same sanitary conditions until 15 weeks of age. Later on, they were transferred into two different production systems, conventional cage (CC) and cage free (CF), up to 82 weeks of age. At 50 and 60 weeks, a total of six hens from each production system were euthanized, and magnum samples were collected. The qPCR was used to determine the RNA transcription level of five reference genes, ACTB, 18S, GAPDH, MSX2 and HMBS. These genes were evaluated for transcript expression in magnum tissues by NormFinder, BestKeeper, geNorm and RefFinder software. The results indicated that the most stable gene in the CF housing system was HMBS in three of the algorithms and in the CC housing system was the 18S, and the best combination of reference genes was HMBS/GAPDH in CF and 18S/HMBS in CC. In conclusion, HMBS, 18S and GAPDH genes could be used together as reference genes for the normalization of the magnum tissues transcript expression of hens in CF and CC housing systems.

Effects of graded levels of exogenous xylanase in corn-soy diets with two amino acid density and fat levels postpellet in broiler chickens: live performance, energy utilization, digestibility, and carcass characteristics.

This experiment evaluated the interactive effects among xylanase (XL; 0, 8,000, 16,000, and 32,000 BXU/kg), amino acid density (AA; high and low 10% difference), and additional fat (AF; 0 or +1.17%) applied postpellet in corn-soybean meal diets with dried distillers grains with solubles on performance, energy utilization, digestibility, and carcass traits in Ross 708 male broilers. A completely randomized block (pen location) design with 16 treatments arranged factorially (4 XL levels, 2 AA, and 2 AF) was analyzed using mixed models. No significant interactions or main effects were observed for feed intake at 49 d (P > 0.05) but chicks were heavier when consuming diets containing 0 or 8,000 BXU/kg (P = 0.015), high AA (P < 0.001), and 1.17% AF (P < 0.001). Feed efficiency did not vary with XL supplementation (P > 0.05) but was improved in broilers fed the higher AA and AF diet (P = 0.015 for AA × AF). AME, GE, and CP digestibility were assessed at days 17 and 42. There were multiple interactions observed at day 17 with a significant three-way showing that AME and CP digestibility improved when increasing the XL and AF levels in the high AA fed birds compared with the low-density diets. At day 42, XL and AF significantly affected AMEn, GE, or CP digestibility; however, there was a significant interaction between XL and AF. Diets supplemented with 1.17% AF improved AMEn significantly in broilers fed the highest XL level. Breast yield was not affected by treatments, but wing yield decreased with high AA density when diets contained 16,000 BXU/kg without differences for the other diets (P = 0.04 for XL × AA). Effects of XL, AA, and AF interactions on performance and cut-up-part yields have to be considered until day 42 for most of the variables studied. However, at 49 d of age, the dietary AA density and AF did not markedly influence the response to XL in maize-based diets.

Corn drying temperature, particle size, and amylase supplementation influence growth performance, digestive tract development, and nutrient utilization of broilers.

Broiler live performance may be influenced by postharvest corn drying temperature, and results could depend on particle size after grinding. The supplementation with an exogenous amylase may improve performance parameters, but responses to enzymes are also affected by particle size. Two parallel experiments were conducted to evaluate the effects of hard-kernel corn dried at 2 temperatures (35°C and 120°C), ground at 2 particle sizes (coarse or fine), and 3 supplementation levels (0, 133, and 266 g ton-1) of an exogenous amylase on live performance, gastrointestinal organ development, energy utilization, and nutrient digestibility. Twelve dietary treatments resulting from a 2 × 2 × 3 factorial arrangement of drying temperature, particle size, and amylase supplementation were evaluated in both experiments. A total of 1,920 day-old male chicks were randomly allocated to 96 floor pens, while 480 chicks were distributed among 4 battery brooder units. Ileal and fecal samples were collected to determine energy utilization and nutrient digestibility using titanium dioxide as inert marker. At 42 D, organs were collected, and relative weight or length was determined. Data were analyzed using a three-way ANOVA in a randomized complete block design. Feeding fine corn-based diets showed improvements on live performance for both studies. At 40 D, supplementing 266 g ton-1 of amylase improved feed conversion ratio (P < 0.05) by 1 point compared to chickens that consumed nonsupplemented diets and feed with amylase at 133 g ton-1. Broilers fed coarse corn-based diets had heavier gizzard (P < 0.001) and liver (P < 0.05) than chickens that consumed fine corn-based diets. In addition, starch digestibility was improved by amylase (P < 0.05) at 133 g ton-1 and by feeding coarse corn-based diets (P = 0.06). For chicks raised in cages (16 D), AMEn was increased (P < 0.01) by amylase supplementation regardless of its inclusion level. In conclusion, drying temperature and particle size interactions influenced broiler live performance, gastrointestinal organ development, nutrient digestibility, and energy utilization, and these parameters were improved by supplementing amylase.

The Role of Incubation Conditions in the Onset of Avian Myopathies.

White striping, wooden breast, and spaghetti muscle have become common myopathies in broilers worldwide. Several research reports have indicated that the origin of these lesions is metabolic disorders. These failures in normal metabolism can start very early in life, and suboptimal incubation conditions may trigger some of the key alterations on muscle metabolism. Incubation conditions affect the development of muscle and can be associated with the onset of myopathies. A series of experiments conducted with broilers, turkeys, and ducks are discussed to overview primary information showing the main changes in breast muscle histomorphology, metabolism, and physiology caused by suboptimal incubation conditions. These modifications may be associated with current myopathies. Those effects of incubation on myopathy occurrence and severity have also been confirmed at slaughter age. The impact of egg storage, temperature profiles, oxygen concentrations, and time of hatch have been evaluated. The effects have been observed in diverse species, genetic lines, and both genders. Histological and muscle evaluations have detected that myopathies could be induced by extended hypoxia and high temperatures, and those effects depend on the genetic line. Thus, these modifications in muscle metabolic responses may make hatchlings more susceptible to develop myopathies during grow out due to thermal stress, high-density diets, and fast growth rates.

The Potential of Guanidino Acetic Acid to Reduce the Occurrence and Severity of Broiler Muscle Myopathies.

Guanidinoacetic acid (GAA) is the biochemical precursor of creatine, which, in its phosphorylated form, is an essential high-energy carrier in the muscle. Although creatine has limited stability in feed processing, GAA is well established as a source of creatine in the animal feed industry. Published data demonstrate beneficial effects of GAA supplementation on muscle creatine, energy compounds, and antioxidant status, leading to improvements in broiler body weight gain, feed conversion ratio, and breast meat yield. Although increases in weight gain and meat yield are often associated with wooden breast (WB) and other myopathies, recent reports have suggested the potential of GAA supplementation to reduce the occurrence and severity of WB while improving breast meat yield. This disorder increases the hardness of the Pectoralis major muscle and has emerged as a current challenge to the broiler industry worldwide by impacting meat quality. Genetic selection, fast-growth rates, and environmental stressors have been identified to be the main factors related to this myopathy, but the actual cause of this disorder is still unknown. Creatine supplementation has been used as a nutritional prescription in the treatment of several muscular myopathies in humans and other animals. Because GAA is a common feed additive in poultry production, the potential of GAA supplementation to reduce broiler myopathies has been investigated in experimental and commercial scenarios. In addition, a few studies have evaluated the potential of creatine in plasma and blood enzymes related to creatine to be used as potential markers for WB. The evidence indicates that GAA could potentially minimize the incidence of WB. More data are warranted to understand the factors affecting the potential efficacy of GAA to reduce the occurrence and severity of myopathies.

Temporal characterization of wooden breast myopathy ("woody breast") severity and correlation with growth rate and lymphocytic phlebitis in three commercial broiler strains and a random-bred broiler strain.

Wooden breast myopathy (WBM), or "woody breast" or "wooden breast" affects modern, rapidly growing, high breast-yield broiler chickens. Decreased meat quality due to undesirable organoleptic properties and condemnation of affected breast meat cause economic losses. The pathogenesis of WBM remains unknown. In this study, WBM lesion development was determined in three modern broiler strains and Athens Canadian Random Bred (ACRB) broilers, a 1950s unselected broiler chicken. Correlations between WBM severity and incubation temperature profile, sex, strain, body weight, and lymphocytic phlebitis were also determined. At 2, 4, 6, and 8 weeks of age, samples of breast muscle from 10 male and 10 female birds from each strain, incubated under optimal or low-early, high-late temperatures, were scored histologically for severity of WBM and lymphocytic phlebitis. WBM lesions, identified as early as 2 weeks, became progressively more severe with age and growth in the three commercial broiler strains. WBM severity was significantly correlated with lymphocytic phlebitis and body weight. Lymphocytic phlebitis and minimal WBM were present in the ACRB broilers at all samplings, but did not progress in severity over time. There were no significant differences in severity of WBM among the commercial broiler strains, between sexes, or between incubation temperature profiles. The positive correlation between WBM severity and lymphocytic phlebitis indicates vascular injury is likely an important factor in the pathogenesis. Mild muscle lesions in ACRB birds without overt clinical signs indicate subclinical muscle disease may have been present in broilers prior to the description of WBM.

Prevalence and severity of osteochondrosis of the free thoracic vertebra in three modern broiler strains and the Athens Canadian Random Bred control broiler.

Osteochondrosis (OCD) results from a disturbance of endochondral ossification in articular cartilage and is an important cause of lameness in several animal species, including chickens. OCD lesions in the free thoracic vertebra (FTV) of chickens are essential to the pathogenesis of pathogenic Enterococcus cecorum. The goal of this study was to determine the prevalence of OCD in the FTV among three modern broiler chicken crosses (strains A/A, A/B, and C/C) and Athens Canadian Random Bred (ACRB) chickens, which served as the control group. The effect of sex, age, strain, body weight, and incubation temperature profile on OCD severity for each group was determined. At 2, 4, 6, and 8 weeks of age, the FTV of 10 male and 10 female birds from each strain exposed to either optimal or low-early, high-late incubation temperature profiles were collected and scored histologically for OCD lesion severity. OCD spectrum lesions were detected in >70% of all strain/sex combinations, including the ACRB controls. No association was observed between mean OCD score and broiler strain, incubation temperature profile, sex, age, or body weight. These findings indicate that OCD of the FTV is common in broiler chickens with similar prevalence observed in broilers with modern genetics and the ACRB broilers which represent 1950s broiler genetics. As the parameters examined did not have a statistical correlation with OCD, additional work is needed to understand factors that contribute to development of OCD in chickens.