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Monday, PM, Arkansas Ballroom D, PHYSIOLOGY
Plasma Amino Acid Levels and Growth Per-
Susceptibility to heat stress in fast and slow
formance of Broilers Fed Supplemental L-Arginine During
growing turkey lines.
L. J. Mills*1,2, M. A. Mitchell1, and M.
Cool Temperature Exposure. C. A. Ruiz-Feria*1, M. T. Kidd2,
Mahon2, 1Roslin Institute (Edinburgh), Midlothian, UK, 2University of and R. F. Wideman1, 1Department of Poultry Science, University of Arkansas, Fayetteville AR 72701, 2Nutri-Quest, Inc., Chesterfield MO,63017.
Commercial selection for improved growth rate may increase susceptibil-ity to pre-slaughter stress which could have important implications for L-arginine (Arg) is an essential amino acid for avian species and the welfare and meat quality. The study was divided into two parts. In the precursor for the potent vasodilator Nitric Oxide (NO). Previously, sup- first, groups of 24 birds from fast (FL) and slow (SL) growing lines of plemental dietary Argreduced pulmonary arterial pressure and the in- turkeys were placed in climate chambers at either 19.6±0.1◦C and 23±1% cidence of ascites. High levels of Arg in feed can result in high plasma RH (control) or 38.1±0.4◦C and 31±2% RH (heat stress) for 2 hours and urea, which has been reported to inhibit NO synthesis by macrophages.
their physiological responses compared. In the second part the metabolic This study was designed to evaluate growth performance, ascites mortal- rate of 6 birds from each line was determined by indirect calorimetry dur- ity, and plasma Arg, urea, and ornithine in broilers fed low (LP) or high inga 2 hour control period (20.4±1.5◦C and 65±7% RH) followed by a (HP) crude protein with no additional Argin feed or water (CTL), or 3 hour heat stress (35.5±1.5◦C and 64±7% RH). Continuous recordings 0.3% Argin the drinkingwater (ARW) for 24 h every 72 h, or 0.15 or of deep body temperature were obtained from data loggers implanted in 0.3% supplemental Argin the feed. Male broiler chicks were raised on the peritoneum. Heat stress resulted in a significant increase in body litter in 48 pens, and at 21 d the temperature was lowered to 16oC. At temperature with a marked hypocapnic alkalosis in both lines. The body 38 d, one bird in each pen was blood sampled, then ARW was provided temperature and pCO2 responses were significantly greater in FL than in (Time 0, 700 h). For CTL and ARW groups, additional blood samples SL. Body temperature rose by 3.7±0.9◦C in the fast growing birds com- were collected for one bird per pen at 3, 6, 12, and 36 h after time 0.
pared to 0.7±0.4◦C in the slower line (p<0.001). The pantinginduced Plasma amino acids were analyzed usingHPLC, and data were analyzed hypocapnia was 2.3 fold greater in FL (p=0.01).
with the SAS program. Birds fed the HP diet were heavier at 42 d than greater thermoregulatory effort (panting) in FL paradoxically resulted in birds fed the LP diet (3.27 vs 3.11 kg). No differences were found in feed less successful control of body temperature compared to SL. Metabolic conversion or ascites mortality due to protein or Argtreatment. Plasma heat production (MHP) was 35% (p<0.005) higher in FL than in SL dur- Arg was similar for all groups at time 0, but increased in the ARW group ingheat stress. The elevated MHP was accompanied by a sig at 3, 6 and 12 h after Argwas provided in the water. Within 12 h after greater hyperthermia than in the SL counterparts (p<0.05) suggesting returningto tap water, plasma Arglevels of the ARW group did not dif- that the efficiency of respiratory evaporative heat loss may be less in the fer from CTL. Plasma urea and ornithine exhibited the same pattern as faster growing birds. It is concluded that the fast growing lines of turkeys Arg, but HP diets resulted in higher plasma levels of urea and ornithine exhibit less efficient thermoregulation than slow growing lines even at the compared with LP diets. These results indicate that kidney arginase was same body weight and are thus more susceptible to thermal stress which readily activated by Argprovided in the water, resultingin an immediate may be reflected in more extensive hyperthermia-induced pathology and increase in plasma urea and ornithine. The absence of an Argeffect on ascites mortality may be associated with the excessively elevated plasmaurea values.
Key Words: Heat stress, Turkeys, Metabolic heat production, Indirectcalorimetry, Thermoregulation Key Words: Ascites, Arginine, Urea, Nitric Oxide Cellular mechanisms of adaptation in intestinal
hexose absorption in the broiler chicken during chronic heat
Furosemide does not facilitate pulmonary va-
stress. M. A. Mitchell*, A. J. Carlisle, and R. R. Hunter, Roslin Insti-
sodilation during acute unilateral pulmonary artery occlu-
tute (Edinburgh), Midlothian, UK.
sion in clinically healthy broilers.
Wideman, Jr., University of Arkansas, Fayetteville, AR.
ed exposure to elevated environmental temperatures a range of homeostatic responses are employed to maximise heat loss and Previously we demonstrated that mean systemic arterial pressure declines minimise heat production. The mechanisms of concomitant adaptations in broilers (≤ 75 mmHg) triggering renal retention of fluid and solute dur- in intestinal absorptive and digestive function are poorly understood. In- ing the pathophysiological progression of pulmonary hypertension syn- creases in hexose and amino acid absorption in vivo have been described drome (PHS). The onset of PHS in broilers was delayed when broilers in the chronically heat stressed broiler. The present study has therefore with chronic unilateral pulmonary artery occlusion were reared on a diet attempted to characterise the mechanisms mediatingsuch responses by containinga diuretic, 0.015% furosemide (FURO). In the present experi- measurement of galactose uptake in heat stressed fowls using an in vitro ment, we tested the hypothesis that furosemide would postpone the onset isolated enterocyte preparation. Broiler chickens were reared from 4-6 of PHS by actingas a pulmonary vasodilator. Cardio-pulmonary func- weeks of age at temperatures of either 22◦C or 35◦C. Enterocytes were tion was evaluated in lightly anesthetized, clinically healthy, 35 to 49 d prepared from jejunal tissue and incubated at 41.5◦C for 1 hour in a old male broilers reared on a CONTROL diet or the same diet contain- medium containing1.9mM galactose and trace amounts of C14-labelled ing0.015% FURO from day 14 to day 49. Acute unilateral pulmonary hexose. Galactose accumulation rates and steady state intracellular hex- artery occlusion triggered equivalent increases in blood flow through the ose concentration were significantly elevated in enterocytes from heat unoccluded pulmonary artery, as well as similar increases in pulmonary adapted birds compared to controls as reflected in a 49% increase in arterial pressure, and pulmonary vascular resistance in the CONTROL the accumulation ratio (p<0.01).
and FURO groups. In both groups, the mean systemic arterial pressure brane glucose transporter system with phloridzin and omission of sodium from the medium abolished these differences. Inhibition of hexose efflux total peripheral resistance duringunilateral pulmonary artery occlusion.
via the sodium independent basolateral membrane system by cytocha- Cardiac output, heart rate and stroke volume did not change consis- lasin B greatly enhanced galactose accumulation by approximately 5 fold tently in either group during pulmonary artery occlusion. When com- (p<0.001) in enterocytes from control and heat stressed birds. Cells from pared with broilers fed the CONTROL diet, the FURO diet did not alter the latter group were capable of achieving a much higher intracellular body weight, heart rate, ECG wave amplitude, hematocrit, or absolute galactose concentration and maintaining a greater concentration gradi- and normalized ventricular weights. However, the FURO diet did sig- ent through the sodium dependent transport system. Enhanced hexose nificantly raise the percentage saturation of hemoglobin with oxygen in absorption observed in vivo duringchronic heat stress in fowls may be contrast with broilers fed the CONTROL diet (89.2 vs 84.2 %). Dietary mediated, at least in part, by increased uptake of substrate by the en- FURO does not appear to delay the onset of PHS in broilers by acting terocyte through the sodium dependent, brush-border membrane, active as a pulmonary vasodilator. Instead, the diuretic action of furosemide transport system (SGLT-1). It is proposed that this phenomenon may alleviates fluid and sodium retention contributingto venous cong involve changes in the electrochemical gradient for sodium.
and right-sided congestive heart failure during the pathophysiologicalprogression leading to PHS.
Key Words: Intestinal absorption, Heat stress, Adaptation Key Words: Ascites, Pulmonary Hypertension, Furosemide, Diuretic, Sys-temic Hypotension Luminal fluid composition in the small intestine
Effects of NH4Cl,KCl and NH4Cl + KCl on
of the broiler chicken under thermoneutral and heat stress
Serum Blood Electrolytes and Performance of Broilers Un-
conditions. M. A. Mitchell* and R. R. Hunter, Roslin Institute (Ed-
der Chronic Heat Stress. H. Kermanshahi*1, J. Arshami1, and A.
Hessabi Nameghi1, 1Ferdowsi University of Mashhad, Faculty of Agri-culture, Dept. Animal Science.
It is recognised that the absorption of sugars and amino acids from thesmall intestine is accomplished by both high affinity transporters and To study nutritional-physiological effects of NH4Cl and KCl on serum systems. Uncertainty about luminal substrate electrolytes and the performance of broilers, 560 meat type chicks from concentrations makes it difficult to calculate the relative contributions 35-56 days of age were kept under Chronic Heat Stress(CHS) at 35 C of mediated vs non-mediated absorption.
for 4 hours per day usingcompletely randomized desig fore the composition of bulk phase luminal fluid has been determined replicates per treatment, 14 birds per replicate. With a 2∗4 factorial ar- in three regions of the small intestine of broilers (n=12) fed ad libitum rangements, male and female birds were separately divided in pens and under thermoneutral (TN) and moderate heat stress (HS) conditions.
received the followingtreatments addingto their drinkingwater: I)0.3% Luminal glucose ranged from 68±22mM in the duodenum to 8±5mM NH4Cl; II)0.3% KCl; III)I + II; IV)Control. Feed and water provided in the ileum in TN and from 56±23mM to 12±8mM duringHS in the ad libitum. Blood was collected on days 42, 49, and 56 days in order Luminal methionine concentration exhibited a to determine the levels of K+, Cl−, Ca++, and Na+ in serum. In a de- similar proximal-distal gradient in TN (11±3 to 3±2mM) but concentra- scendingmanner, with increasingage, CHS decreased the levels of K+, tions were <2mM throughout in HS. Sodium concentration was highest Ca++, and Na+ and increased the level of Cl− in all treatments. Sex in ileum (84±22mM) in TN but in the duodenum (118±10mM) in HS.
showed the same trend except for Na+ that the results for females were Potassium concentration was consistently greater in the lower small in- inconsistent. A significant increase of K+ in serum was seen at day 42 testine in both thermal environments being27-37mM in the ileum and in NH4Cl and KCl treatments (P≤0.05) and this effect reversed at day 12-20mM in the duodenum. The proximal-distal gradient was more pro- 56. Sex had no effect on K+ level in each period. Combination of NH4Cl nounced in HS. The duodenal and jejunal contents were acid (pH =6.4- + KCl decreased the level of K+ on days 49 and 56 while the levels of 6.8) in both TN and HS but ileal chyme was alkaline (pH=7.7-8.2) the Ca++ and Cl− in the serum increased (P≤0.05). The levels of Ca++ higher value occurring in HS. Total osmolarity ranged from 389±58mOsm and Na+ were higher in male chickens on days 42, 49, and 56 (P≤0.05) in the duodenum to 430mOsm in the jejunum of TN birds but was ele- but no significant difference were seen in K+ and Cl− levels in all peri- vated throughout the small intestine of the heat stressed group (413±47 ods except for males at day 56 that the level of K+ was higher. NH4Cl to 463±24 mOsm in ileum and duodenum respectively). Thus luminal decreased feed intake and body weight during 35-56 days of age. KCl in- fluid tends to be hyperosmolar compared to plasma, has a much elevated creased body weight of chickens during this period (P≤0.05). Daily gain potassium and reduced sodium concentration and contains high concen- also significantly increased during 42-56 days of age. KCl numerically trations of both glucose and methionine favouring non-transporter me- increased daily feed intake but had no effect on feed conversion ratio.
diated absorption. Heat stress may alter the luminal fluid composition Male chickens were heavier and consumed more feed (P≤0.05). Under substantially. The findings have important implications the study and CHS conditions of this experiment, NH4Cl had no considerable effect on understandingof nutrient absorption in both in vivo and in vitro systems.
the broiler performance. KCl improved feed intake and thus its use indrinkingwater might be useful in chickens under CHS.
Key Words: Luminal fluid, Intestinal absorption, Heat stress, Broiler Key Words: Chronic Heat Stress, NH4Cl and KCl, Electrolytes, Broilers Ultrastructural and Molecular Changes in the
Heart Tissue From Ascitic Broiler Chickens. A. A. Olkowski*1,
B. M. Rathgeber2, and H. L. Classen1, 1Department of Animal and
Echocardiographic evaluation of heart function
Poultry Science, 2Department of Applied Microbiology and Food Sci- in normal chickens and chickens with heart failure and as-
ence,University of Saskatchewan,Saskatoon,SK,S7N 5B5.
cites. A. A. Olkowski* and H. L. Classen, Department of Animal and
Poultry Science, University of Saskatchewan.
This study examined ultrastructural and molecular features of cardiomy-ocytes in leghorn chicks, (resistant to heart disease), slow growing broilers Landmarks of ascites in broiler chickens include severe changes in the (low incidence of heart disease), fast growing broilers (high incidence of ventricular chamber dimensions and chamber geometry. Most of the cur- heart failure), and chickens with heart failure and ascites. There were rent knowledge on patho-physiology of the heart in ascitic chickens is considerable differences in the extra-cellular matrix (ECM) and the my- derived from studies on surgically altered subjects or using post-mortem ofibril contractile apparatus architecture between normal and abnormal material. Hence, there is a shortage of information on heart function in hearts. A significant reduction in the myofibril component was seen in vivo obtained usingnon-invasive methods. In the present study we used the hearts from ascitic broilers. The fine network of collagen struts was echocardiography to evaluate heart function in vivo in 5 leghorn chick- disrupted and the mesh of endomysial collagen encompassing cardiomy- ens, 6 feed restricted broilers, 4 ad-libitum fed broilers, and 10 ascitic ocytes was considerably reduced in the affected hearts. Most extensive broilers. The birds were 35 to 42 days of age at the time of examina- changes in the ECM were observed in the myocardium from ascitic birds.
tion. The Doppler study revealed left and right atrio-ventricular valve The activity of matrix metalloproteinase (MMP) in the cytosolic fraction regurgitation in 8 out of 10 chickens showing clinical signs of heart fail- of ventricular myocardium homogenates revealed the presence of both ure, whereas there was no evidence of faulty valves in normal broilers pro MMP-2 (72 KDa), and active MMP-2 (69 KDa). The relative gelati- A typical M-mode echocardiogram from a chicken nolytic activity of pro MMP-2 was higher in preparations from broilers, ns of heart failure demonstrated impaired ventric- particularly in the preparations from the left ventriculum (LV) of fast ular wall motion and severely dilated left and right ventricular cham- growing broiler chicks in comparison to slow growing chicks (p<0.03).
Fractional shortening(FS) was considerably reduced (p<0.001) SDS-PAGE profile of washed myofibrils from LV myocardium of ascitic in ascitic birds (mean: 19.5 ± 2.0 SE) in comparison to normal birds birds showed several distinctly different features not seen in other prepa- (mean: 39.1 ± 3.6 SE). Four apparently normal broilers had lower FS rations. Western blot analysis of these samples showed several fragments in comparison to leghorn chickens. Two dimensional echocardiography of myosin heavy chain, M-protein, and titin. The content of titin was 10 revealed that prominent pericardial effusion (PE) is commonly present to 30% lower in myofibrils preparations from broilers in comparison to in affected birds and some apparently birds. This was later confirmed leghorn chickens. Titin content was lowest in preparations from the LV of on post mortem examination. The present study indicates that clinical broilers with advanced heart failure and ascites, and constituted approxi- features such as valve incompetence, left and right ventricular chamber mately 43% of titin present in the preparation from leghorn chicks. These dilation, impaired ventricular wall motion, and reduced FS are common data indicate that heart pump failure in ascitic broilers is associated with in ascitic birds. Also, heart function appears to be considerably reduced extensive remodelingof ECM and molecular chang in some apparently normal broilers. These birds may be at high risk of heart failure and ascites. The reduction in FS is consistent with decreasedcardiac output. The significance of PE is not known at present, but this Broiler, Ascites, Extra-cellular matrix, Ultrastructural, issue deserves more attention because accumulation of fluid around the heart muscle may impair diastolic function.
Key Words: Broiler, Heart failure, Ascites, Echocardiography Influence of NH4Cl,KCl,and NH4Cl + KCl on
between male (M) and female (F) chicks. AHS increased Cl− duringand Blood Electrolytes and Mortality of Chicks Under Acute
at the end of period. The treatments increased level of Cl− before and Heat Stress.
J. Arshami*1 and A. Hessabi Nameghi1, 1Ferdowsi duringAHS but decreased at the end with highest for I and II respectively Univ. Mashhad, Faculty of Agriculture, Dept. Animal Sci., Mashhad, (P≤0.05). The level of Cl− decreased in M and F with no differences at the end. AHS was decreased Ca++ duringand at the end. The treat-ments increased Ca++ at the beginning then gradually decreased by the Sudden heat induction of summer time in N.E. of Iran as a cause of end with lowest for NH4Cl (P≤0.05). The M group showed higher Ca++ mortality was evaluated in a randomized design experiment (2∗4 facto- than F (P≤0.05). The level of Na+ decreased under AHS. Treatments rial) usingLohman chicks (14/pen, 20 pens/sex). Chicks were received I and III showed lowest and highest Na+ at the end (P≤0.05). The M 4 treatments (I:0.6% NH4Cl; II:0.6% KCl; III:I + II; and IV: Control) chicks had higher Na+ than F (P≤0.05). The pH increased in all treat- on day 33rd in drinkingwater and the Acute Heat Stress (AHS) on day ments at the end of AHS (P≤0.05). Treatments I and III showed lowest 34th at 40◦C for 5 hrs. Blood samples were collected at the beginning, pH before and duringAHS (P≤0.05). The F chicks showed lower pH during(2:30 hrs.) and at the end of AHS in order to determine the levels than M under AHS (P≤0.05). The % mortality was highest for control of K+, Cl−, Ca++, Na+, pH, and % mortality. The AHS increased K+ group and lowest for treatments (P≤0.05). NH4Cl would acts better on during, but decreased at the end. The treatments increased K+ before, duringand at the end of AHS with the highest for treatments I and IIIrespectively (P≤0.05). The effect of AHS on K+ did not show differences Key Words: Acute Heat Stress, NH4Cl, KCl, Electrolytes, Mortality Tuesday, AM, John Q. Hammons Hall I, ENVIRONMENT AND MANAGEMENT
Effect of vitamin and trace mineral withdrawl
(35 and 33.5%, respectively). Moisture content was lowest (P<.05) in on performance of broilers reared under high density stress.
birds fed the pro-biotic added diets. A main effect, but no interaction, K. V. Vo*, N. A. Adefope, C. L. Fenderson, and S. H. Kolison, Tennessee of nutrient level and pro-biotic was seen on amount of nitrogen and P in State University, Nashville, TN 37209.
the excreta with the lowest (P<.05) levels seen in excreta from birds fedthe LN+ diet. These effects were consistent between phases. These data Five hundred and four 42-day-old commercial broilers were used in a show that the addition of the pro-biotic improved nutrient (protein, Ca, 2x3 factorial design to evaluate the effect of withdrawal of vitamins (V) P) retention and allowed the birds fed the LN+ to overcome the effect and trace minerals (TV) duringthe last 7 days of the growingperiod on of low nutrient (12% less protein and 18% less Ca and nPP) density on growth performance, processing yield, and stress response. Three floor performance. This has implications on the economics of production and space allowances used were 855 (D1), 615 (D2), and 475 sq cm per bird (D3). Half of the birds were fed a control finishingration while the otherhalf were fed a finishingration with no supplemental vitamins and trace Key Words: Pro-biotic, Performance, Retention, Protein, Minerals minerals. Feed and water were given ad libitum. All birds received a con-tinuous lighting program. Results from this study indicated that rearing Broiler performance and carcass quality at dif-
density had a significant (P≤.05) effect on weight gain. The average 7- ferent stocking densities. J. J. R. Feddes1, E. J. Emmanuel*1,
day weight gains were 586.6, 545.2 and 444.3 g for D1, D2 and D3 groups, R. H. McGovern2, and M. J. Zuidhof2, 1University of Alberta, Edmon- respectively. Feed conversions were poorer with increasingrearingden- ton, AB, Canada, 2Alberta Agriculture, Food and Rural Development, sities. Crowdingcondition produced a hemo-stress response in birds as indicated by an increase in the percent of heterophils and a decrease inthe percent of lymphocytes.
The effects of four stockingdensities and nipple drinker densities on of birds in the group D3 significantly (P≤.05) reduced weight gain and broiler performance and carcass traits were measured. The stockingden- increased feed:gain ratio. No significant differences in these parameters sities of 0.45, 0.60, 0.75 and 0.90 ft2/bird corresponded to 260, 195, 156 were observed in groups D1 and D2 due to withdrawal. Hematocrit, dif- and 130 birds per pen, respectively. The nipple drinker densities were 5, ferential white blood cell count, dressingpercentage, fat and part yields 10, 15 and 20 birds/nipple. Two trials were conducted with the birds in were not significantly affected by withdrawal of V and TM for 7 days.
trial 1 shipped at day 39 and those in trial 2 shipped at day 42. Wa- Based on these results, it is not feasible to withdraw V and TM dur- ter and feed were provided ad libitum and light was provided 23h/day.
ingthe last 7 days of the growingperiod when birds were reared under Nipple density had no effect on broiler performance and carcass quality.
The effect of stockingdensity showed that the 0.45 ft2/bird treatmenthad a significantly lower BW (1898 g) and carcass weight (1334 g), while Key Words: Broiler, Rearingdensity, Vitamin and trace mineral with- the 0.75 ft2/bird treatment had the highest BW (1985 g) along with car- cass weight (1432). Although the 0.45 ft2/bird treatment had the lowestBW, the yield of broilers per unit of floor space was highest in this treat- Performance and nutrient retention in broilers
ment (46.0 kg/m2). The coefficient of variation (flock uniformity) was fed a lactobacilus-based pro-biotic. C. R. Angel*1, P. Melv in2, R.
significantly higher in the 0.90 ft2/bird treatment (15.3 %) while the A. Dalloul1, N. M. Tamim1, T. A. Shellem1, and J. A. Doerr1, 1Univ. other treatments were the same (13 %). The birds in the 0.90 ft2/bird of Maryland, College Park, 2Perdue Farms, Inc., Salisbury, MD.
treatment consumed the least amount of feed (2993 g/bird) and those inthe 0.75 ft2/bird treatment consumed the highest amount of feed (3183g/bird). The amount of water consumed and the water to feed ratio was Four hundred male broilers (Ross 308) were reared on floor pens and highest in the 0.45 ft2/bird treatment (5546 ml/bird) which also had a provided starter diet with or without pro-biotic (Primalac, .2 lb/ton).
significantly higher water to feed ratio (1.85 ml/g). Stocking density had At 18 d, birds were weighed and, within pro-biotic treatment, randomly no significant effects on mortality, breast yield, carcass grading, scratches assigned to battery pens (8/pen, 10 pens/trt). A 2x2 factorial arrange- ment of nutrient density [control (C) (19.3% protein (CP), .84%, Ca,.37% nonphytate P (nPP); 17.1% CP, .8% Ca, .3% nPP in the grower Key Words: Broiler, Stockingdensity, Body weight, Feed consumption and finisher diet, respectively) and low nutrient (LN) (17% CP, .69% Ca,.30% nPP; 15% CP, .66% Ca, .25% nPP in the grower and finisher diet, respectively)] and pro-biotic [0 or 2 (+) lb/ton] was used. Body weightand feed efficiency were determined and excreta collected at the end of Gene amplification approach for detection of
the grower (18-28 d) and finisher (28-42 d) phases. At the end of each Salmonella typhimurium in poultry aerosol samples.
phase, 3 birds/pen were sampled. At 28 d, birds were randomized within Jackson*1, D. E. Corrier2, S. D. Pillai3, C. L. Woodward1, J. Pe˜ treatment into 6 pens /trt (4 birds/pen).
S. C. Ricke1, 1Department of Poultry Science, Texas A&M University, fed LN weig hed less (P<.05) than those fed C, and C+ fed birds gained College Station, TX, 2USDA-ARS, College Station, TX, 3Department more (P<.05) than either C or LN. At 42 d LN+ fed birds were heav- of Soil & Crop Sciences, Texas A&M University, El Paso, TX.
ier (P<.05) than those fed C. There was a nutrient level and pro-bioticmain effect, but no interaction, on protein, Ca, and P retention at 28 d and 42 d of age. Ca and P retention at 28 d was higher (P<.05) in The development of effective bioaerosol samplingmethods is critical con- LN+ fed birds (50.9 and 43.6%, respectively) and lowest in C fed birds

Source: http://www.poultryscience.org/meeting-abstracts/psa99/99psab22.pdf