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

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

Effects of reduced crude protein diets while maintaining essential amino acid concentrations on growth performance, nitrogen output, ammonia production, and meat yield.

An experiment was conducted to determine the effect of feeding reduced crude protein (CP) diets to Ross × Ross 708 male broilers while providing adequate essential amino acid (AA) concentrations on growth performance, nitrogen (N) and ammonia output, and carcass characteristics from d 1 to 33 post hatch. Birds received 1 of 6 dietary treatments (10 replicate pens per treatment) varying in CP content. Diet 1 (control) was formulated with DL-Met, L-Lys, and L-Thr (23.2, 20.7, and 19.1% CP) in the starter (1-14 d of age), grower (15-25 d of age), and finisher (26-33 d of age) periods, respectively. Dietary L-Val, Gly (only in starter period), L-Ile, L-Arg, and L-Trp were sequentially supplemented in the order of limitation in Diets 2 through 6. Dietary CP was reduced gradually across the dietary treatments resulting in a CP reduction in Diets 1 to 6 by 3.4, 3.4, and 2.3% points in the starter, grower, and finisher periods, respectively. At d 14, 25, and 33 posthatch, feed conversion decreased (P < 0.05) with L-Val addition (Diet 2) and increased (P < 0.01) with L-Val to L-Trp addition (Diet 6) to the control. Dietary treatments did not alter weights and yields of carcass, breast, drum, or thighs. Dietary CP reduction with added L-Val (Diet 2), L-Val to L-Arg (Diet 5), or L-Val to L-Trp (Diet 6) increased abdominal fat (P < 0.01) compared with control. Nitrogen excretion (g/bird; P = 0.003) and equilibrium ammonia concentration (mg/kg; P = 0.041) at day 33 reduced by 16% and 48% respectively in birds fed reduced-CP diets with L-Val to L-Trp (Diet 6) compared with control-fed birds. This study indicated that sequential addition of supplemental AA in the order of limitation from DL-Met to L-Arg allowed reduction of dietary CP beyond 2%-point without depressing growth performance and meat yield of broilers from day 1 to 33 while reducing nitrogen excretion and ammonia emissions.

Effects of phytase supplementation and increased nutrient density on growth performance, carcass characteristics, and hypothalamic appetitive hormone expression and catecholamine concentrations in broilers from 1 to 43 days of age.

Two experiments were conducted to evaluate extra-phosphoric effects of phytase and nutrient density on growth performance, meat yield, and hypothalamic appetitive hormone expression and catecholamine concentrations of broilers. Experiment 1 determined differences of digestible amino acid concentrations and AMEn using 256 Yield Plus × Ross 708 broilers (32 cages, 8 birds/cage) fed diets without or with 4,500 phytase units (FTU)/kg inclusion (16 reps/treatment). In Experiment 2, 832 Yield Plus × Ross 708 broilers (32 pens; 26 birds/pen) were provided diets in a 2 × 2 factorial arrangement consisting of 2 nutrient contents (without or with increased density) and 2 phytase inclusions (0 or 4,500 FTU/kg). Increased nutrient density was formulated to contain 0.007, 0.015, 0.013, 0.021, 0.024%, and 61 kcal/kg higher digestible SAA, Lys, Thr, Val, Ile, and AMEn (from Experiment 1) respectively, compared with the control diet. Growth performance was determined at 14, 28, and 40 d of age and carcass characteristics at 41 d of age. At 43 d of age, plasma inositol, hypothalamic appetitive hormone expression, and catecholamine concentrations were determined from 4 birds/pen. Additive effects of phytase inclusion and increased nutrient density resulted in the lowest (P < 0.05) feed conversion from 1 to 40 d of age and the heaviest (P < 0.01) breast meat weights among dietary treatments. Phytase addition numerically increased feed intake (P = 0.06) and BW gain (P = 0.051) compared with birds fed diets without phytase from 1 to 40 d of age. Plasma inositol and dopamine concentrations were 2.3- and 1.2-fold higher (P < 0.01), respectively, in broilers fed phytase-added diets than birds fed diets without phytase inclusion. However, mRNA expression of neuropeptide Y, agouti-related peptide, proopiomelanocortin, cholecystokinin A receptor, ghrelin, and serotonin concentration were not different (P > 0.05) among treatments. These data indicated additive effects of phytase supplementation and increased nutrient density on growth performance and meat accretion of broilers. However, the influence of phytase on feed intake warrants future research.

Determination of the optimum digestible isoleucine to lysine ratios for male Yield Plus × Ross 708 broilers between 1.0 and 4.0 kg body weight utilizing growth performance and carcass characteristics.

Three experiments (Exp) were conducted to determine optimal digestible Ile to Lys ratios for male Yield Plus × Ross 708 broilers from approximately 1.0 to 4.0 kg BW. Broilers were fed dose-response diets with inclusions of blood cells that were formulated to contain a gradient of digestible Ile to Lys ratios (0.46 to 0.83). Treatments for Exp 1 to 3 were fed from 21 to 35, 28 to 42, and 35 to 49 d of age, respectively, to target market weights from 2.5 to 4.0 kg. Experiments utilized positive control (PC) diets that did not contain blood cells and were formulated to the same Ile ratios as Treatment 5. Birds and feed were weighed by pen on the first and last days of the experimental period to determine growth performance. Selected broilers were processed and deboned to determine carcass characteristics. For all Exp, quadratic effects (P ≤ 0.001) were observed with BW gain, feed conversion ratio (FCR), breast meat weight, and breast meat yield (BMY) as digestible Ile to Lys ratios increased. Contrasts between PC and Treatment 5 for each Exp displayed no effect of blood cell inclusion with the exception of FCR in Exp 1 (P = 0.001) and BMY in Exp 3 (P = 0.017). Optimum digestible Ile to Lys ratios for Exp 1 were determined to range from 0.640 to 0.725 for growth from 1.0 to 2.5 kg BW (P ≤ 0.001) and breast meat characteristics. In Exp 2, optimum ratios ranged from 0.664 to 0.682 for growth and breast meat characteristics from 1.6 to 3.1 kg BW (P ≤ 0.001). For growth and breast meat characteristics of broilers in Exp 3, optimum ratios ranged from 0.625 to 0.730, from 2.6 to 3.9 kg BW (P ≤ 0.001). Based on these findings, optimum digestible Ile to Lys ratios were determined to range from 0.63 to 0.73 for broilers from 1.0 to 4.0 kg BW.

Inositol and gradient phytase supplementation in broiler diets during a 6-week production period: 1. effects on growth performance and meat yield.

An experiment was conducted to evaluate effects of inositol and gradient phytase supplementation on growth performance and meat yield of broilers from 1 to 41 d of age. A total of 1,920 Yield Plus × Ross 708 male chicks were placed in 64 floor pens (30 birds per pen). Each pen received one of the 8 dietary treatments (8 replicate pens) from 1 to 15, 16 to 29, and 30 to 40 d of age. Treatment 1 was formulated to contain 0.165 and 0.150% lower calcium and phosphorus, respectively, than treatment 7 (positive control). Phytase was added to treatment 1 at concentration of 500, 1,500, 4,500, 13,500, and 40,500 phytase units (FTU)/kg to establish treatments 2 to 6, respectively. Treatment 8 was formulated by adding inositol to treatment 7 based on the expected inositol liberation in treatment 6. Feed and birds were weighed at 1, 15, 29, and 40 d of age to determine BW gain, feed intake, and feed conversion. Twelve birds per pen were processed at 41 d of age to determine carcass characteristics. From 1 to 40 d of age, log-quadratic effects of phytase (treatments 1-6) were observed for BW gain (P = 0.002) and feed conversion in broilers (P = 0.018), whereas feed intake increased log-linearly (P = 0.045). The addition of 40,500 FTU/kg of phytase increased cumulative BW gain (P = 0.001) and decreased cumulative feed conversion (P = 0.005) by 4.7 and 2.6%, respectively, compared with birds subjected to treatment 8. Log-quadratic effects of phytase additions were observed for carcass (P < 0.001) and breast meat weights (P = 0.004). Growth performance and carcass characteristics of broilers subjected to treatment 7 were similar (P > 0.05) to those of birds subjected to treatment 8. These data demonstrate that the extraphosphoric effects of phytase may be associated with increased feed intake of broilers. Inositol supplementation did not provide additional benefits to broilers in this study.

Inositol and gradient phytase supplementation in broiler diets during a 6-week production period: 2. Effects on phytate degradation and inositol liberation in gizzard and ileal digesta contents.

An experiment was conducted to evaluate effects of dietary phytase and inositol supplementation on phytate degradation in gizzard and ileal digesta contents of broilers from 1 to 43 d of age. One thousand nine hundred and twenty Yield Plus × Ross 708 male chicks were placed in 64 floor pens (30 birds/pen). Each pen received 1 of 8 dietary treatments from 1 to 43 d of age. Treatment 1 was formulated to contain 0.165 and 0.150% lower calcium and phosphorus, respectively, than treatment 7. Treatments 2 to 6 were formulated by adding phytase at 500, 1,500, 4,500, 13,500, and 40,500 phytase units (FTU)/kg, respectively, to treatment 1. Treatment 8 was established by adding inositol to treatment 7 based on the maximum inositol liberation in treatment 6. At 15, 29, and 43 d of age, gizzard contents, ileal digesta, and blood were collected for analysis of inositol and inositol phosphate (IP) 2, 3, 4, 5, and 6 concentrations. Increasing phytase from 0 to 40,500 FTU/kg resulted in log-quadratic reductions (P < 0.01) of inositol pentaphosphate and inositol hexakisphosphate concentrations in the gizzard and ileal digesta contents of broilers at 15, 29, and 43 d of age. The increase in phytase doses in treatments 1 to 6 reduced IP3 and IP4 concentrations in a log-quadratic manner (P < 0.05) at each collection period in gizzard contents but only at 43 d of age in the ileal digesta of broilers (P < 0.01). Log-quadratic increases (P < 0.05) of inositol concentrations were observed in gizzard and ileal digesta contents when increasing phytase activity from 0 to 40,500 FTU/kg at each collection period, which translated to a log-quadratic increase (P < 0.01) in plasma inositol concentration of broilers at 15, 29, and 43 d of age. Phytase supplementation up to 40,500 FTU/kg may benefit broilers by reducing phytate concentrations in the gizzard and ileal digesta contents. Moreover, inositol release in the ileal digesta may translate to increased plasma inositol concentration.

Influence of exogenous phytase supplementation on phytate degradation, plasma inositol, alkaline phosphatase, and glucose concentrations of broilers at 28 days of age.

Inositol is the final product of phytate degradation, which has the potential to serve as an indicator of phytase efficacy. An experiment was conducted to evaluate effects of supplementing broiler diets with phytase on phytate degradation and plasma inositol concentrations at 28 d of age. Twenty-four Ross × Ross 708 male chicks were placed in battery cages (4 birds per cage) from 1 to 21 d of age and individually from 22 to 28 d of age. At 27 d of age, a catheter was placed in the brachial vein of broilers to avoid repeated puncture of the vein during blood collection. At 28 d of age, broilers received 1 of 3 experimental diets formulated to contain 0, 400, or 1,200 phytase units (FTU)/kg, respectively, in diet 1, 2, and 3. Blood was collected 1 h before feeding experimental diets and from 20 to 240 min after feeding experimental diets at 20-min intervals with a final blood collection at 480 min to determine plasma inositol concentrations. Inositol phosphate (IP) ester degradation was determined in gizzard contents and ileal digesta. Broilers provided the 1,200 FTU/kg phytase diet had 60% less (P < 0.01) IP6 concentration in gizzard content (1,264 vs. 4,176 nmol/g) and ileal digesta (13,472 vs. 33,244 nmol/g) than birds fed the 400 FTU/kg diet. Adding phytase at 1,200 FTU/kg increased (P < 0.01) inositol concentrations in gizzard content and ileal digesta of broilers by 2.5 (2,703 vs. 1,071 nmol/g) and 3.5 (16,485 vs. 4,667 nmol/g) fold, respectively, compared with adding 400 FTU/kg. Plasma inositol concentration of broilers was not different (P = 0.94) among the dietary treatments at each collection time. Inositol liberation in the digesta of broilers fed diets with 1,200 FTU/kg phytase did not translate to increased plasma inositol concentrations, which warrants further investigation.

Effects of dietary amino acid density and feed allocation during the starter period on 41 days of age growth performance and processing characteristics of broiler chickens given coccidiosis vaccination at hatch1.

A study was conducted to determine if increasing digestible (dig) amino acid (AA) density or feed allocation of starter diets fed to broilers receiving coccidiosis vaccination can ameliorate poor cumulative growth performance and reduce meat yield. A total of 1,600 Yield Plus Ross × Ross 708 male broilers were assigned to a 2 × 3 factorial arrangement of dig AA density [moderate (1.15% dig Lys) and high (1.25% dig Lys)] and feed allotment (0.45, 0.73, and 1.00 kg/bird) with 2 positive control treatments during the starter period. Diets were formulated to essential AA ratios relative to dig Lys. Vaccinated birds received a 1x dosage of Coccivac- B52 prior to placement, whereas non-vaccinated birds in the positive control groups were fed diets containing diclazuril. Following consumption of the starter diets, birds were provided common grower and finisher diets. Broilers fed the high AA density diet during the starter period had higher cumulative BW gain and lower cumulative feed conversion ratios (P < 0.05) than those fed the moderate AA density diet. Broilers fed the high AA density diet had heavier (P ≤ 0.005) carcass and total breast weights than birds fed the moderate AA density diet. Broilers fed a starter allotment of 1.00 kg/bird produced heavier carcass weights (P ≤ 0.006) than did birds provided lower allotments. Additionally, broilers fed the high AA density diet had a greater percentage of 0 scores (P = 0.005) for the upper intestinal region during scoring. Results from this study indicated that feeding the high AA density diet at higher feed allotments during the starter period resulted in increased AA intake, which supported the bird through the vaccine challenge and enhanced the cumulative growth and meat yield.

Effects of age and supplemental xylanase in corn- and wheat-based diets on cecal volatile fatty acid concentrations of broilers1.

An experiment was conducted to evaluate the effects of age and supplemental xylanase in corn- or wheat-based diets on cecal volatile fatty acid (VFA) concentrations of Ross × Ross 708 male broilers during weekly intervals from 14 to 42 d of age. Day-old chicks (1,500) were randomly distributed into 60 floor pens (25 chicks/pen; 0.078 m2/bird) and fed 1 of 4 dietary treatments (TRT) throughout the starter (1 to 14 d of age), grower (15 to 28 d of age), and finisher (29 to 42 d of age) phases with 15 replicates per TRT. Dietary TRT consisted of a 2 × 2 factorial arrangement with 2 diet types (corn- or wheat-based) and 2 xylanase inclusions (0 or 16,000 BXU/kg) as the main factors. At 14, 21, 28, 35, and 42 d of age, cecal contents were collected (4 birds/pen) for VFA analysis. Main effects of cereal grain source (P < 0.05) affected propionic, isobutyric, butyric, isovaleric, valeric, and isocaproic acid concentrations at 14, 21, 28, 35, and 42 d of age. Broilers fed corn-based diets had higher (P < 0.05) propionic, isobutyric, isovaleric, valeric, and isocaproic concentrations than those fed wheat-based diets from 14 to 42 d of age. However, broilers fed wheat-based diets had higher (P < 0.05) butyric acid concentrations at 28, 35, and 42 d of age compared with those fed corn-based diets. Individual and total VFA concentrations increased (P < 0.05) linearly from 14 to 42 d of age. Age and cereal grain interacted (P < 0.05) to affect propionic, isobutyric, butyric, isovaleric, and valeric acid concentrations. These results indicate that broiler cecal VFA concentrations are influenced by cereal grain source and age. In contrast, supplemental xylanase inconsistently influenced broiler cecal VFA concentrations. Therefore, future research evaluating factors affecting supplemental xylanase and cecal VFA production in broilers is warranted. Additionally, research investigating cereal grain source effects on cecal microflora development and fermentative patterns may be beneficial for optimizing cecal VFA production in broilers.

Effects of pre-starter and starter diets varying in amino acid density given to broiler chickens that received coccidiosis vaccination at hatch1.

An experiment was conducted to evaluate broilers vaccinated against coccidiosis fed combinations of pre-starter and starter diets varying in digestible amino acid (dAA) density from 1 to 19 d of age on subsequent growth performance and meat yield. A total of 1,800 Yield Plus Ross × Ross 708 male broilers were allocated to 60 floor pens and assigned to 1 of the 6 treatments. Four pre-starter diets varying in dAA density [1.15% dLys, 1.25% dLys, 1.35% dLys, and Positive Control (1.15% dLys + Diclazuril)] were fed until 9 d of age. Then, 3 starter diets varying in dAA density [1.15% dLys, 1.25% dLys, and PC (1.15% dLys + Diclazuril)] were given from 10 to 19 d of age. All diets were formulated to similar dAA ratios to dLys; hence, resulting in increasing amino acid (AA) density among the dietary treatments. Birds were given common grower and finisher diets for the remainder of the experiment. At 19, 27, and 40 d of age, broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had increased BW gain (P ≤ 0.006) compared with broilers fed the 1.15% dLys density diets. Broilers that received the 1.15% dLys density pre-starter diet had a lower cumulative BW gain (P = 0.007) than those fed the 1.35% and 1.25% dLys density pre-starter diets. Broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had the heaviest (P ≤ 0.008) total breast weights. Increasing the pre-starter dAA density enhanced (P ≤ 0.03) total breast weight by 28 g (1.25% dLys density) and 51 g (1.35% dLys density). Results from this study indicated that increasing dAA density from 1 to 19 d of age enabled a 1 to 19 d dAA intake increase of 4.8 g, which enhanced cumulative growth and meat yield of broilers vaccinated against coccidiosis.

Effects of cereal grain source and supplemental xylanase concentrations on broiler growth performance and cecal volatile fatty acid concentrations from 1 to 40 d of age2.

An experiment was conducted to evaluate the effects of feeding diets varying in cereal grain source and supplemental xylanase concentrations on growth performance and cecal volatile fatty acid (VFA) concentrations of Ross × Ross 708 male broilers from 1 to 40 d of age. A total of 1,536 day-old chicks were randomly distributed into 64 floor pens (24 chicks/pen; 0.08 m2/bird) and fed 1 of 8 dietary treatments (TRT) with 8 replicates per TRT. Experimental TRT were of either corn- (TRT 1 to 4) or wheat-based (TRT 5 to 8) origins. The 4 dietary TRT for each cereal grain source consisted of a positive control (PC) reference diet and 3 reduced AMEn diets (AMEn reduced 66 kcal/kg below PC) with supplemental xylanase at either 0 (negative control), 12,000, or 24,000 BXU/kg. Birds and feed were weighed at 1, 14, 26, and 40 d of age to determine BW gain, feed intake, and feed conversion ratio. At 26 and 40 d of age, cecal contents were collected and pooled per pen (7 birds/pen; 5 replicate pens/TRT) for VFA concentrations. No TRT differences (P > 0.05) in cumulative growth performance were observed. Likewise, no TRT differences (P > 0.05) in acetic or total VFA concentrations were observed at 26 or 40 d of age. However, cereal grain source (P < 0.05) influenced propionic, isobutyric, butyric, and isovaleric concentrations at 26 and 40 d of age with birds receiving the corn-based diets having higher (P < 0.05) cecal propionic, isobutyric, and isovaleric concentrations, and lower (P < 0.05) butyric acid concentrations than those fed the wheat-based diets. These results indicate that dietary cereal grain source may influence individual cecal VFA concentrations. However, supplemental xylanase did not affect broiler growth performance or cecal VFA concentrations. Therefore, future research evaluating factors limiting xylanase responses on broiler growth performance and cecal VFA production is warranted.

Skeletal muscle growth characteristics and myogenic stem cell activity in broiler chickens affected by wooden breast.

The degenerative myopathy known as wooden breast (WB) has been increasingly observed in the breast muscle (PM) of commercial broilers during the last decade. Previous research has demonstrated that WB may be induced or ameliorated by modulating dietary digestible Lys (dLys) concentrations. Two concurrent experiments (Exp) were conducted to verify the effects of feeding 2 diets formulated to 75% and 100% of recommended dLys concentrations from 15 to 25 d of age on production responses and WB incidence (Exp 1), and the characterization of muscle stem cell activity in broilers affected by WB (Exp 2). At 25 and 43 d of age, birds were injected with 5΄-bromo-2΄-deoxyuridine (BrdU) prior to the collection of PM tissue to label mitotically active cells. Muscle samples were processed for cryosectioning and immunofluorescence staining and microscopy in order to determine myofiber cross-sectional area (CSA), to enumerate Myf-5+ and Pax7+ myogenic stem cell populations, and to determine the mitotic activity (BrdU+) of these populations. The reduced dLys diet produced broilers with differing (P < 0.001) incidences of WB within the same flock (Exp 1), with some detrimental effects on performance and processing characteristics. In Exp 2, broilers with severe WB had increased numbers (P = 0.016) and proportions (P = 0.022) of mitotically active, myogenic stem cells, as well as increased proportions (P < 0.05) of large CSA myofibers relative to broilers unaffected by WB at 25 d of age. At 43 d of age, broilers affected by severe WB had a greater (P = 0.011) total population of myogenic stem cell types (Myf-5+, Pax7+, or Myf-5+:Pax7+) and a concurrent increase (P = 0.007) in the mitotic activity (Myf-5+:BrdU+, and Pax7+:BrdU+, and Myf-5+:Pax7+:BrdU+) of these cells. Additionally, a greater (P < 0.05) proportion of small CSA myofibers was observed in broilers with severe WB. These results provide evidence that myofiber CSA, as well as the heterogeneity and mitotic activity of myogenic stem cell populations were altered in the presence of WB.

Effects of reduced digestible lysine density on myopathies of the Pectoralis major muscles in broiler chickens at 48 and 62 days of age.

Quantitative control of nutrient intake may decrease the incidence of wooden breast (WB) and white striping (WS) myopathies with some impairment of live performance. Two experiments (Exp) utilizing Yield Plus × Ross 708 male broilers were conducted to determine if a reduction in myopathies may be obtained through a qualitative approach by reducing digestible lysine (dLys) density. All birds received an identical starter diet until 11 d of age. In Exp 1 (63 pens; 22 birds/pen), each pen was then randomly assigned to 1 of the following 7 dietary treatments (TRT) for a 47 d production period. Seven dietary treatments were provided for the grower 1 (G1; 12 to 18 d of age) and grower 2 (G2; 19 to 26 d of age) phases: 1) 100% of primary breeder recommendations for dLys throughout Exp; 2) 85% of TRT 1 dLys for G1; 3) 85% of TRT 1 dLys for G2; 4) 85% of TRT 1 dLys for G1 and G2; 5) 75% of TRT 1 dLys for G1; 6) 75% of TRT 1 dLys for G2; 7) 75% of TRT 1 for G1 and G2. In Exp 2 (24 pens; 30 birds/pen), birds were randomly assigned to 1 of the following 4 dietary TRT (Table 2) during a 61 d production period. Four dietary treatments were provided for the grower (G; 12 to 28 d) and finisher 1 (F1; 29 to 40 d of age) phases: 1) 100% of primary breeder recommendations for dLys 2) 85% of TRT 1 dLys for G; 3) 85% of TRT 1 dLys for F1; 4) 85% of TRT 1 dLys for G and F1; thereafter, birds received common finisher 1 (Exp 1: 27 to 42 d of age), finisher 2 (Exp 2: 41 to 48 d of age) and withdrawal (Exp 1: 43 to 47 d of age; Exp 2: 49 to 61 d of age) diets. Ideal amino acid ratios were not maintained in reduced dLys diets in either Exp. At 48 (Exp 1; 18 birds/pen) and 62 (Exp 2; 30 birds/pen) d of age, selected birds were processed and fillets were visually scored for WB and WS. No differences (P > 0.05) in cumulative live performance responses between TRT 1 and the remaining TRT were observed in either Exp. In Exp 1, the incidence of severe WB (20.8%) and WS (42.3%) at 48 d of age among birds receiving TRT 7 was reduced (P < 0.01) compared with TRT 1 (WB: 36.6%; WS: 64.3%), at the expense of reduced (P = 0.003) breast weights and yield. In Exp 2, the incidence of severe WB (18.8%) and WS (17.8%) at 62 d of age for birds receiving TRT 4 was reduced (P < 0.05) compared with TRT 1 (WB: 39.3%; WS: 38.3%), without any detrimental effects on processing characteristics. These results indicate that altering dietary dLys during critical periods of the growth trajectory may be a viable strategy for reducing the incidence and severity of WB and WS.

Effects of reduced dietary energy and amino acid density on Pectoralis major myopathies in broiler chickens at 36 and 49 days of age1.

Two experiments (Exp) were conducted to determine if reductions in the incidence and severity of wooden breast (WB) and white striping (WS) may be obtained by reducing dietary nutrient density. In each Exp, Yield Plus × Ross 708 male broiler chicks were placed into 63 pens (22 birds/pen). All birds received an identical prestarter diet until 7 d of age, after which time each pen was randomly assigned to 1 of the following 7 dietary treatments (TRT) for the starter (8 to 14 d), grower (15 to 24 d), finisher 1 (Exp 1: 26 to 35 d; Exp 2: 26 to 42 d), and withdrawal (Exp 2: 43 to 48 d) phases: 1) 100% of primary breeder recommendations for digestible amino acid and metabolizable energy density throughout Exp; 2) 95% of TRT 1 until 14 d of age, then as TRT 1; 3) 95% of TRT 1 until 24 d of age, then as TRT 1; 4) 95% of TRT 1 throughout Exp; 5) 90% of TRT 1 until 14 d of age, then as TRT 1; 6) 90% of TRT 1 until 24 d of age, then as TRT 1; 7) 90% of TRT 1 throughout Exp. At 36 d (Exp 1) and 49 d (Exp 2), 18 birds per pen were processed and evaluated for WS and WB. In Exp 1, reduced dietary density in the starter phase (TRT 2 and TRT 5) resulted in increased (P ≤ 0.05) incidences of severe WB (32.9% and 34.7%) relative to TRT 1 (18.2%). In Exp 2, broilers assigned to TRT 7 had reduced (P < 0.01) incidences of severe WB (20.8%) and WS (42.3%) relative to the control (WB: 36.5%; WS: 64.5%). In both Exp, plasma creatine kinase and lactate dehydrogenase increased (P ≤ 0.05) with increasing scores for WB and WS. Reducing dietary nutrient density from 8 to 14 d may exacerbate fillet myopathies in broilers reared to 35 d of age. Although reducing dietary energy and amino acid density to 90% of recommendations from 1 to 48 d reduced the severity of myopathies, these reductions occurred with compromises in live performance. Altogether, these results indicated that concurrent manipulation of dietary amino acid and energy density is not a viable practical solution for breast myopathies.

Effects of feeding reduced crude protein diets on growth performance, nitrogen excretion, and plasma uric acid concentration of broiler chicks during the starter period.

An experiment (2 trials) was conducted to determine the effects of feeding reduced crude protein (CP) diets to Ross × Ross 708 male broilers while maintaining adequate essential amino acid (AA) concentrations on growth performance, nitrogen excretion, and plasma uric acid (UA) concentration during the starter period. In trial 1, 11 dietary treatments were fed from 1 to 18 d of age containing 1.20% digestible Lys. Diet 1 (23.2% CP) was formulated with DL-Met, L-Lys, and L-Thr to contain 1.70 total Gly + Ser to digestible Lys ratio whereas diets 2 (23.4% CP) to 11 were formulated with additional Gly to contain 1.90 total Gly + Ser to digestible Lys ratio. Free AA were added sequentially in the order of limitation (L-Val, L-Ile, L-Arg, L-Trp, L-His, L-Phe, and L-Leu) from diets 3 to 10 to decrease CP content from 22.6 to 18.8%, respectively. In diet 11, L-Gln was added to increase the CP content to 23.4%. Feed conversion of broilers fed diet 2 was lower (P < 0.05) than those consuming diets 6 to 11 from 1 to 17 d of age. Nitrogen excretion (mg/b/d) decreased (P < 0.001) by 14.1% when broilers were fed diet 4 compared with birds fed diet 2 from 15 to 16 d of age. Broilers fed diet 4 had lower (P = 0.011) plasma UA concentration than birds fed diet 2 at 18 d of age. In trial 2, 8 dietary treatments containing 1.25% digestible Lys and 1.70 total Gly + Ser to digestible Lys ratio were fed from 1 to 21 d of age. Diet 1 (24.0% CP) was supplemented with DL-Met, L-Lys, and L-Thr. Free AA (L-Val, Gly, L-Ile, L-Arg, L-Trp, L-His, and L-Phe) were sequentially supplemented in the order of limitation to decrease CP content in diets 2 to 8 from 23.8 to 20.3%. Broilers fed diet 1 had higher (P < 0.05) body weight gain and lower (P < 0.05) feed conversion when compared with diet 7 or 8. Plasma UA concentration of broiler provided diets 4 to 8 was lower (P < 0.05) compared with diet 1 at 21 d of age. Placing a minimum on dietary CP percentage may not be necessary when proper AA ratios are implemented in diet formulation.

Effects of quantitative nutrient allocation on myopathies of the Pectoralis major muscles in broiler chickens at 32, 43, and 50 days of age.

An experiment was conducted to determine if myopathies of the Pectoralis major muscles are influenced by differences in growth trajectory achieved through a controlled feeding program. Male Yield Plus × Ross 708 broiler chicks were placed into 28 pens (25 birds/pen) equipped with plastic slats to prevent coprophagy. All birds received identical starter (1 to 10 d), grower (11 to 32 d), finisher (33 to 42 d), and withdrawal (43 to 50 d) diets that were formulated to meet or exceed nutrient recommendations of the primary breeder. Each pen of birds was randomly assigned to one of 4 pair-feeding programs (TRT 1: ad libitum; TRT 2: 95% of TRT 1 intake; TRT 3: 90% of TRT 1 intake; and TRT 4: 85% of TRT 1 intake) with 7 replicate pens per treatment. Feed intake and mortality were recorded daily. Individual BW was recorded at 31, 42, and 49 d of age. Blood samples were collected from 4 birds per pen at 31, 41, and 48 d of age and subsequently analyzed for plasma creatine kinase (CK) and lactate dehydrogenase (LDH). At 32, 43, and 50 d of age, 4 birds per pen were euthanized for necropsy. The right breast fillet of each bird was visually scored for white striping (WS) and wooden breast (WB). Linear decreases (P ≤ 0.01) in feed intake, BW gain, feed conversion ratio, and mortality were observed with decreasing feed allocation. Linear decreases (P ≤ 0.01) in severity were observed for WS and WB at 33, 43, and 50 d with decreasing feed allocation. Severity of WB at 33 and 43 d, as well as that of WS at 43 and 50 d, decreased (P ≤ 0.05) quadratically with decreasing feed allocation. Reduced feed allocation produced quadratic decreases (P ≤ 0.05) in CK and LDH concentrations at 31, 41, and 48 days. These results indicate that the incidence of breast fillet myopathies in broilers may be reduced through controlled feeding programs.

Digestibility of energy and lipids and oxidative stress in nursery pigs fed commercially available lipids.

An experiment was conducted to evaluate the impact of lipid source on GE and ether extract (EE) digestibility, oxidative stress, and gut integrity in nursery pigs fed diets containing 10% soybean oil (SO), choice white grease (CWG), palm oil (PO), distillers' corn oil with approximately 5% FFA (DCO-1), or distillers' corn oil with approximately 10% FFA (DCO-2). Fifty-four barrows weaned at 28 d of age were fed a common starter diet for 7 d, group fed their respective experimental diets for an additional 7 d, and then moved to metabolism crates and individually fed their respective diets for another 10 d. Following this period, a 4-d total fecal and urine collection period was used to determine apparent total tract digestibility (ATTD) of GE and EE and to determine the DE and ME content of each lipid source (11.03 ± 0.51 kg final BW). Following the last day of fecal and urine collection, pigs were given an oral dose of lactulose and mannitol and fed their respective experimental diets with urine collected for the following 12 h. A subsequent urine collection occurred for 5 h to determine thiobarbituric acid reactive substances (TBARS) and isoprostane (IsoP) concentrations. Following this urine collection, serum was obtained and analyzed for TBARS and endotoxin concentrations. Soybean oil had the greatest ( < 0.05) DE (9,388 kcal/kg) content compared with DCO-1, DCO-2, CWG, and PO (8,001, 8,052, 8,531, and 8,293 kcal/kg lipid, respectively). Energy digestibility was greatest for SO compared with the other lipid sources ( < 0.05). The ATTD of EE averaged 85.0% and varied slightly (84.4 to 85.6%) among treatments. Differences in ME content among lipids were similar to those reported for DE, with ME values for DCO-1, DCO-2, CWG, PO, and SO being 7,921, 7,955, 8,535, 8,350, and 9,408 kcal/kg lipid, respectively. Metabolizable energy as a percentage of DE did not differ among lipid sources. Pigs fed lipid diets had greater ( < 0.05) serum TBARS compared with pigs fed the control diet, but no differences were observed in urinary TBARS excretion among the lipid treatments. Urinary IsoP excretion differed among treatments ( < 0.01) but was highly variable (34.0 to 104.6 pg). However, no differences were observed among treatments for the urinary lactulose:mannitol ratio and serum endotoxin. These results indicate that DE and ME content of SO are greater than that of other lipid sources evaluated, but feeding these lipids has no effect on gut integrity while producing variable effects on oxidative stress.

Methodology affects measures of phosphorus availability in growing broilers. 2. Effects of calcium feeding strategy and dietary adaptation period length on phytate hydrolysis at different locations in the gastrointestinal tract1.

An experiment was conducted to determine the effects of dietary adaptation period length (DAPL; 0, 24, and 48 h) and Ca feeding strategy (0.35% or 1.4:1 Ca:P ratio) on apparent phytate P (myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate; IP6) hydrolysis (AIP6H) and apparent digestibility (AΣIPD) of the sum of all inositol phosphate esters (ΣIP) of corn-titration diets at 3 locations (proventriculus/gizzard [Pro/Giz], jejunum, and distal ileum) in the gastrointestinal tract (GIT). Four hundred thirty-two Ross × Ross 708 male broilers were placed into 36 battery cages and fed a common starter diet until 18 d of age. Eight semipurified diets and a control diet for DAPL were fed from 19 to 21 d of age. Digesta were collected at each location from 4 birds per pen after each DAPL. Diets formulated with a 1.4:1 Ca:P ratio had higher (P < 0.001) AIP6H and AΣIPD when measured in the jejunum and ileum, but no differences were observed in the Pro/Giz. No interaction effects between DAPL and sampling location were observed for AIP6H and AΣIPD of the control diet. Conversely, interactive effects (P < 0.05) were measured for AIP6H and AΣIPD of the corn-titration diets. The highest values for both AIP6H (73.9%) and AΣIPD (80.7%) were measured in the Pro/Giz after 24 h. Phytate hydrolysis and AΣIPD were similar regardless of DAPL when sampled from the distal ileum. Concentrations of TiO2, IP6 and ΣIP also varied (P < 0.05) in response to DAPL and sampling location. Variability was likely due to inconsistencies in the flow of inositol phosphate esters and TiO2 through the GIT, specifically the Pro/Giz. Therefore, the use of TiO2 as an inert marker may have limitations when determining the hydrolysis and digestibility of phytate esters.

Methodology affects measures of phosphorus availability in growing broilers: Effects of calcium feeding strategy and dietary adaptation period length on true ileal phosphorus digestibility and predicted endogenous phosphorus losses1.

An experiment was conducted to determine the effects of Ca feeding strategy and dietary adaptation period length (DAPL) on the apparent ileal P digestibility (AIPD) and apparent ileal myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (IP6) hydrolysis (AIIP6H) of corn titration diets. Nine hundred sixty Ross × Ross 708 male broiler chicks were placed into 80 battery cages. Broilers received a common starter diet until 18 d of age and then were fed one of 10 experimental treatments from 19 to 21 d of age. Nine diets were formulated to evaluate 5 corn inclusion concentrations (15, 30, 45, 60, or 75%) and 2 Ca feeding strategies (fixed at 0.35% or 1.4:1 Ca:P) after 3 DAPL (zero, 24, and 48 h). As a control for DAPL, one treatment group received the common starter diet for the duration of the experiment. Broilers consuming the control diet had higher (P < 0.001) BW gain and feed intake than broilers fed the corn titration diets. Apparent ileal P digestibility of the control diet was affected (P = 0.038) by DAPL. For diets formulated with a 1.4:1 Ca:P ratio, negative linear effects (P < 0.05) on AIPD and AIIP6H were observed with increasing corn. Conversely, for diets formulated with 0.35% Ca, positive linear effects (P < 0.05) were measured for AIPD after a 48 DAPL while no linear or quadratic effects (P > 0.05) were measured for AIPD or AIIP6H for other DAPL. Broilers fed diets formulated with 1.4:1 Ca:P had variable (P < 0.05) true ileal P digestibility (TIPD; 32.2, 15.1, and 35.4%) and negative endogenous P losses (EPL; -190, -499, and -262 mg/kg DM intake) for zero, 24, and 48 h DAPL, respectively. Conversely, TIPD values (41.2, 39.1, and 47.3%) were similar (P > 0.05) and EPL were positive (102, 197, and 154 mg/kg DM intake), regardless of DAPL, for broilers fed diets formulated with 0.35% Ca. These data demonstrated that formulating diets with a 1.4:1 Ca:P ratio affected AIPD of the titration diets, shifting the regression line and predicted negative EPL and an underestimation of TIPD.

Results of an international phosphorus digestibility ring test with broiler chickens.

The objective of this ring test was to investigate the prececal phosphorus (P) digestibility of soybean meal (SBM) in broiler chickens using the trial protocol proposed by the World's Poultry Science Association. It was hypothesized that prececal P digestibility of SBM determined in the collaborating stations is similar. Three diets with different inclusion levels of SBM were mixed in a feed mill specialized in experimental diets and transported to 17 collaborating stations. Broiler chicks were raised on commercial starter diets according to station-specific management routine. Then they were fed the experimental diets for a minimum of 5 d before content of the posterior half of the ileum was collected. A minimum of 6 experimental replicates per diet was used in each station. All diets and digesta samples were analyzed in the same laboratory. Diet, station, and their interaction significantly affected (P < 0.05) the prececal digestibility values of P and calcium of the diets. The prececal P digestibility of SBM was determined by linear regression and varied among stations from 19 to 51%, with significant differences among stations. In a subset of 4 stations, the prececal disappearance of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate)-P; InsP6-P) also was studied. The prececal InsP6-P disappearance correlated well with the prececal P digestibility. We hypothesized that factors influencing InsP6 hydrolysis were main contributors to the variation in prececal P digestibility among stations. These factors were probably related to the feeding and housing conditions (floor pens or cages) of the birds in the pre-experimental phase. Therefore, we suggest that the World's Poultry Science Association protocol for the determination of digestible P be should extended to the standardization of the pre-experimental period. We also suggest that comparisons of P digestibility measurements among studies are made only with great caution until the protocol is more refined.