Feeding Regimen, Dietary Vitamin E, and Genotype Influences on Immunological and Production Traits of Broilers

02OOo Applied Poultry Sdmce, lac

FEEDING REGIMEN, DIETARY VITAMIN E, AND GENOTYPE INFLUENCES ON IMMUNOLOGICAL AND PRODUCTION TRAITSOF BROILERS

Primary Audience: Poult7 Producers, Production Managers, Geneticists, Nutritionists, Veterinarians

1

To whom correspondence should be addressed

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

E B. SIEGEL~ Department of Animal & Poultry Sciences, Virginia Tech, Blacksburg, VA 24061-0306 Phone: (540)231-6472 FAX: (54) 231-3010 E-mail:jacksons@vt. edu C. T.LARSEN D e p h e n t of Laige Animal Sciences, Hwkia Tech, Blacksburg, VA 24061-0442 D. A. EMMERSON Department of Animal & Poulby Sciences, Virginia Tech, Blacksburg, VA 24061-0306 PJERRE-ANDREGERAERT Rhdne-PoulencAnimal Nutrition, Research Department, BP 100 943oOAntony Cedex, France MICHEL PICARD Institut National de la Recherche Agronomique, Station de RecherchesAvicoles, 37380 Nouzilly, France

DILUTED STARTER A N D VITAMIN E

270

each line were randomly assigned to hghtDESCRIPTION OF PROBLEM and temperature-controlled pens with wood shavings as bedding. There were 12 pens of chicks from each line (24 pens total) with 24 chicks per pen. Lighting was continuous to Day 28 and from 01:OO to 23:OO hr thereafter. Feed in mash form and water were provided ad libitum. %o feeding regimens, assigned at random to each line, were consistent with those described by Picard et al. [15J Regimen F consisted of feeding the control diet (Table 1) to 12 days of age. Regimen D consisted of feeding the control diet diluted with 50% wheat bran from 0 to 5 days of age and diluted with 20% bran from 5 to 12 days. Three levels of vitamin E in the form of dl-a-tocopheryl acetate were provided in each diet and were randomly assigned to four pens of each linefeeding regimen subclass. Levels of dietary vitamin E were 10 (L), 100 (M), and 300 (H) IU/kg [16]. From Day 12 to the end of the experiment all chicks were fed the 10 IU/kg control diet. TRAITS MEASURED Individual body weights (BW) were obtained for all chicks at hatch and at 5,12, and 22 days of age. Feed consumption was measured on a pen basis for the periods 0 to 5 and 0 to l2 days of age. From these data feed efficiencywas calculated as gain in BW divided by welght of feed consumed. Immune responses and disease resistance were evaluated by a series of tests. To do this the 24 pens were assigned to either Group I or Group 11. Half of the broilers in each of the l2 pens that made up Group I were inoculated at 12 days of age via the brachial vein with 0.1 mL of 0.25% suspension of sheep red blood cells (SRBC). Plasma antibody levels of SRBC measured 6 and 10 days after immunization [17] were expressed as the log2 of the reciprocal of the last dilution for which agglutination was detected. This procedure was repeated on Day 22 by inoculation of the remaining half of the broilers in each of these pens. At the time of inoculation on Days 12 and 22, samples of blood were obtained from 10 individuals within each pen, smears prepared, and heterophil~and lymphocytes counted to a total of 60 cells [18].

MATERIALSAND METHODS LINES, HUSBANDRY, AND FEEDING REGIMENS Eggs from two broiler parental lines (A and B) known to differ in growth and yield were incubated in the same machine. At hatch, chicks were wing-banded, weighed (g), and vaccinated for Marek’s disease. Chicks from

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

Today’s broiler is a function of husbandry programs designed to maximize the genetic potential of chickens bred for efficient production of edible meat. Improving yield and reducing age at market weight are important in the economics of broiler production. Although market weight has increased because of the shift from whole-bird to cut-up to value-added products and to maximkhg breast yield, the 50-yr trend for marketing broilers at younger ages continues. Consequently, the first 2 wk after hatch has become an increasing proportion of the life of a broiler. Many functional changes occur during the fvst 2 wk after a chick hatches. Synchrony in growth of body components occurs when resources are preferentially allocated to supply (e.&, pancreas, liver, intestine) rather than demand (e.&, muscle, fat) organs [l]. This early allocation of resources to supply organs is essential if demand organs are to reach their growth potential. During this early post-hatch period major changes are also occurring in the thermoregulatory, digestive, circulatory, respiratory, and immune systems [2, 3, 41. Compromises in an orderly growth of supply and demand organs and development of functional systems contribute to skeletal and metabolic disorders and reduced immunocompetence [5, 6, 7, 81. The array of husbandry procedures studied to alleviate these compromises includes various feed restriction programs [9, 10, 111 and dietary supplementation of vitamin E [l2, U, 141. Results from these studies have been mixed, and because most were conducted on a single genetic stock, generalities across stocks may be limited. In the present study we compared feeding regimens, dietary vitamin E levels, and genetic lines in a factorial arrangement.

Research Report SIEGEL et al.

271

STARTERCONTROL (Mash) 0 to 12 Days

INGREDIENT

Cam

soybean meal 48%

I Wheat bran

I

53.75 38.00

I

-

ILvsine. %

I I

I Sulfur amino acids. %

I

0.95

I Threonine. %

I

0.86

I Trvotmhan. % I calcium. %

I I

0.27

Available phosphorus, %

I

5 to 12 Days

43.00 30.00

26.00

18.40

I

50.00

I

20.00

I

I 3034 2250 1.24

Crude ~ r ~ t e i% n.

STARTERDILUTED (20% Bran)

0.98

2203 18.60 0.91 0.71 0.67 0.24 1.00 0.42

I I I I I I

0.43

On Day 22, broilers in each of the 12pens assigned to Group I1 were divided into two equal groups and given an inoculationcontaining either or lo4 E. coli in the posterior thoracic air sac [19]. Five days later they were killed by cervical dislocation and scored for pericardial and air sac lesions [u)]. Mortality was recorded daily to Day22 for Group I1 broilers and to Day 41 for Group I broilers. On Day 41, Group I broilers were weighed and their feed withdrawn overnight. The next morningrandom samples of 10males and 10 females from each line, feeding regimen, and H and L vitamin E level subclass were killed by cervical dislocation and mea-

2693 20.90

I I I I I

1.10

0.86 0.78

0.26

0.98

0.44

surements made for weight (g) of heart, spleen, bursa, gizzard, and the following bilateral traits: e Pectomlis major - weight (0.1 g), length (0.1 cm),width (0.1 cm) 0 Pectoralis minor - weight (0.1 g) 0 shank - weight (0.1 g including toes), length (0.1 cm without toes) 0 lung - weight (0.01 g) 0 ceca - length (0.1 cm) Bilateral differences were analyzed to evaluate developmental stabilities [21]. Descriptions of these analyses and those used for all of the other traits measured are provided

PI.

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

I CALCULATED COMPOSITION AM%, kcavkg

!5TARTERDILUTED (50% Bran) Oto5Days

DILUTED STARTER A N D VITAMIN E

272

out. Sexual dimorphism of 5, 6, 12, and 18% RESULTS AND DISCUSSION for BW on Days 5,12,22, and 41, respectively, in Line A contrasted with 2,5,10, and 12% at these ages in Line B. BW of males and females from feeding Regimen F were 6 and 9% heavier, respectively, at 5 days of age than those from Regimen D (Table 2). When all chicks were placed on feeding Regimen F (Day 12), the relative difference in BW between Regimens D and F was 17% for males and 15% for females. Ten days later (Day 22) the difference between Regimens D and F had decreased to 9% for males and 7% for females. Although there was further reduction to 2% for males and 3% for females, there was no clear capacityfor weight compensation following growth restriction. These results are

BODY WEIGHT (g)

TREQTMENT 5 Days

I

12 Days

22DV

41 DaysA

Broiler line

A

Ma

246'

739

22za

B

82b

2Zb

6nb

2069b

F

€9

255'

740'

2173

D

82b

218b

676b

2134

H

84

239

718

2159

M L

84

239

712

2140

85

234

700

2148

1

4

7

35

A B

82

231'

660'

80

21Sb

61Sb

Pooled standard errors Broiler l i e

1880

I

1854

F

85'

242'

668'

1900

D

7ab

21Ob

622b

1846

H M

81

2311

666'

1920a

81

222b

6Mb

1869ab

L

81

I Pooled standard errors 1

1

6Xb

219b

I

3

I

7

1820b

I

*Group I broilers only. "%leans in a column for a treatment without a common superscript differ significantly (PS.05).

27

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

BODY WEIGHT Chicks from both lines were of the same welght (44.5k0.3 g) at hatch. This similarity was a result of incubating eggs of similar welghts. The known difference in growth potential of the lines (A>B) was evident by 5 days of age in males and 12 days in females (Table 2). BW obtained at subsequent ages provided further evidence of differences in growth patterns between sexes within each line and between lines within each sex. A 7% difference between lines in female BW at 12 and 22 days decreased to about 1% by Day41. In contrast, for males differences between lines remained between 8 and 10% through-

Research Report 273

SIEGEL et al. consistent with those obtained with other stocks and these diets [15] @e., through this age there was no clear capacityof weight compensation for a delayed starting period). BW responses to feeding different dietary levels of vitamin E to l2 days of age were not the same for males and females. Although BW of males were similar regardless of dietary level of vitamin E, femalesfed the H level were heavier than those fed the M and L levels at 12 and 22 days of age (Table 2). The difference between H and L persisted to Day 41, with M being intermediate and not different from either H or L.

H M L Pooled standard errors

superior feed efficiency for both time periods. Behavioral responses of chicks were monitored at the time changes were made in feeding regimens. To measure feed consumption, feeders were removed from the pen, weighed, and returned to the pen. ’IfipicaUy,when feeders were returned, chicks would eat for a few minutes and then rest. On Day 5, when chicks on Regimen D changed from 50 to 20% bran dilution,chicks in 11 of the 12 pens where the change was made continued to eat to crop capacity (about 10 min), suggestingessentially immediate recognition that the less dilute diet contained compensatingnutrients [111. MORTALITY AND HETEROPHIL/ LYMPHOCYTE RATIOS, E. COLI CHALLENGE There were no differences between lines or feeding regimens for mortality to 22 days of age (Table 4). Although mortality increased from 22 to 41 days in both lines, overall there was no difference between them in mortality. In contrast, while mortality for Regimen D increased only from 3.6 to 4.2%, the change for Regimen F was from 4.3 to 9.4%.Among chicks fed different levels of vitamin E to Day 12, mortality to Day 22 was less for H than M and L levels. This advantage did not carry over to 41 days, when primary causes of mortality were ascites and sudden death syndrome.

52

0.73

2578

52

0.71 0.71

242b

53 1

0.02

242b

4

0.74 072 0.73 0.02

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

FEED CONSUMPTION AND EFFICIENCY Through 5 and 12 days of age Line A chicks consumed more feed than those from Line B (Table 3). Because Line A chicks were heavier than those from Line B, feed efficiency was similar for the lines. Dietary level of vitamin E had no influence on feed consumption to Day 5. By Day 12, however, consumption was greater for the H than the M and L levels. As with line effects, there was no difference among levels of vitamin E for feed efficiency, because H females weighed more than M and L females. To Day 5 feed consumption was similar for feeding Regimens F and D (Table 3). By Day 12, however, consumptionwas greater for Regimen F than for D. The greatly enhanced

growth of F chicks resulted in their having

JAPR DILUTED STARTER AND VITAMIN E

274

TABLE 4. Mean heterophil to lymphocyte ratios and % mortalityof broilers byline, feeding regimen, and dietary level of vitamin E

TRENTMENT

MORTALITY

HEEROPHWLYMPHOCYTE

12 Days

I

22 Days

22Dv

41 DaysA

Broiler line A

0.22

O.4gb

3.8

8.2

B

0.26

0.7@

4.2

5.8

F

0.27 0.22

0.66=

4.3

9.4B

0.4sb

3.6

4.2

D

0.22

0.64

l.lb

5.4

0.24

051

4.8'

75

L

0.27

057

5.4'

8.6

0.03

0.06

Pooled standard errors'

%ortalitywas analyzed by frequencies, therefore no standard errors are given.

'bMeans in a column for a treatment without a common superscript differ significantly(Ps.05).

ANTIBODY RESPONSE TO SRBC HeterophWymphocyte (HL)ratios at Maturation of the immune system contin12 days of age were similar for lines, feeding ues during the first few wk after hatching. Inregimens, and dietary levels of vitamin E ("hble 4). Rapid changes occur during this volved is the threshold of response and the period in the maturation of this system [By magnitude of response once the threshold is 241, which may reduce this parameter's value reached, both of which may be influenced by genetic and nongenetic factors [XI. A typical as a measure of stress [25lat very young ages. Ten dayslater (Day22), therewere differences antibody response to an intravenous inoculabetween lines (B >A) and feeding regimens tion of SRBC is for titers to peak at about 5 to 6 days and then decline [26,27j. Dosage may (F>D), but not among dietary levels of be a factor, because too high a dose of antigen vitamin E. When challenged with E. coli on Day 22, can mask response differences among stocks chicks became listlessand reduced feed intake and treatment groups, and too low a dose may for about 24 hr. By 48 hr their behavior and fail to elicit a response [2T71. When injected feed consumption appeared to have returned with 0.1 mL of 0.25% SRBC at 12 days of age, to their prechallenged status. Lesion scores 59% of chicks produced visible agglutination 5 days after challenge were similar for males 6 days later. By Day 10 after inoculation, the (2.45k0.11) and females (23620.13) and proportion declined to 21%. In contrast, when for feeding Regimen F (2.70k0.18) and D inoculated at 22 days of age with SRBC the (2.6320.15). There was an E. coli challenge respective percentages 6 and 10 days later dose effect, with lesions being more severe at were 93 and 86, results consistent with previous reports [26,27l. the higher (3.0720.13) than the lower (2.2820.10) dose. Of particular relevance was The frequency of responders to inoculathe significant line by dietarylevel of vitamin E tion at 12 days of age did not differ between interaction that resulted from no influence of lines or between feeregimens (Table 5). dietary vitamin E in Line A (H = 2.6620.12; There was a difference among dietary levels M =2.57+0.13; L = 2.7120.14) and lower of vitamin E with the frequency being greater lesion scores at the high level (2.3620.11) for H than M and L 6 days after inoculation than at the medium (2.80k0.12) and lower and less 10 days after inoculation. This higher frequency of initial response at young ages (2.9520.14) levels in Line B.

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

H

M

Research Report SIEGEL et al.

275

&

9b

95

86

452

2.67

47b

24a

93

88

4.67

2.70

L

49b

24a

91

82

5.19

2.89

0.21

0.14

Pooled standard errors

followed by a decrease has been observed in other populations [XI. Antibody titers of responders were very low both 6 days (2.5020.15) and 10 days (2.3020.14) after the 12-day inoculation, and there were no differences between lines, feeding regimens, or dietary levels of vitamin E. The frequency of responders of chicks inoculated with SRBC at 22 days of age was similar for lines, feedingregimens, and dietary level of vitamin E (Table 5). Antibody titers 6 and 10 days after inoculation did not differ among feeding regimens or dietary levels of vitamin E, and the decline observed between 6 and 10 days was expected. Antibody titers were lower for Line A than Line B both 6 and 10 days after inoculation. This inverse relationship of growth and antibody titers to SRBC in genetic lines has been observed in several populations [a, 291. SKELETAL, MUSCLE, AND INTERNAL ORGAN SIZES Results are presented separately for males and females because sexual dimorphism was present at 42 days for most of these traits. Weights are expressed as a percentage of BW and lengths as absolute values with text values given as means 2 standard errors.

Bilateral traits are presented as left and right weight or length combined and their symmetry discussed. Shanks and Breasts. There were no differences between lines, feeding regimens, and dietary levels of vitamin E for the weight or length of shanks. There was no evidence of bilateral asymmetryfor either weight or length of shank and, as expected, males had longer (73f0.1 vs. 6.8k0.1 cm)and heavier shanks than females (2.720.03 vs. 1.9220.03%). Relative to BW the I? major was heavier for Line A than Line B males (14.321.9 vs. 11.3215%) and females (13.722.7 vs. 11.1+1.8%). The relationship between lines for the€?minor was similar to that for I? majo5 being 3.3220.04% for Line A males, 2.91+0.05% for Line B males, 3.4920.08% for Line A females, and 2.9220.05% for Line B females. Feeding regimen did not influence relative weights of these muscles. Although dietary level of vitamin E had no influence on weights of these muscles in males, H females had heavier €?major (13.223.5 vs. 11.9+2.7%) and €?minor (3.3520.09 vs. 3.10+0.07%) muscles than L females. Directional asymmetry with muscles on the left side being heavier than those on the right side was present in both sexes. On an

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

H M

DILUTED STARTER AND VITAMIN E

276

D

I

1.69

I

I

Neither feeding regimen nor level of vitamin E influenced bursa weight. Dietary level of vitamin E did not influence g k u d weight. Significantline by feeding regimen interactions were present in both males and females for gizzard weight. The interactions resulted from a difference between lines for feedingRegimen F (B > A) and no difference between lines for Regimen D (Table 6). When feeding regimens were compared within lines, for males there was no difference between them in Line A while there was a difference for Line B (F > D). This pattern reversed for females. Interactions of line with dietary level of vitamin E and line with feeding regimen were significantfor heart weight. As seen in Table 6, when fed the higher level of vitamin E, males and females from Line A had heavier hearts than those from Line B.At the lower dietary vitamin E level, there was no difference between lines for females, whereas for males weights were greater for B than A. The line by feeding regimen interaction of heart weights

1.78

I

1.96

I

1.92

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

absolute weight basis the R major was about 5% and R minor was about 3% heavier on the left than right side. None of the treatments influenced the length of the Prnajor. Width, while similar for dietary levels of vitamin E, was greater for Line A than Line B males (8.2f0.1 vs. 7.420.1 cm)and feeding Regimen F than D (8.1+0.1 vs. 7.720.1 cm).In contrast, for females, the IT major of those fed the higher level of vitamin E was wider than that of those fed the lower level (7.7k0.1 vs. 7.4k0.1 cm), whereas neither line nor feeding regimen influenced the width of this muscle. As with weight there was directional asymmetry, with the left Z? major being about 1% longer and 3% wider than the right side. Internal Organs. Spleen weights were similar for males (0.097k0.004%) and females (0.10lkO.o06%) as well as for lines, feeding regimens, and dietary levels of vitamin E. Bursa were heavier for Line A than Line B males (0.189k0.007 vs. 0.157kO.o06%) and females (0.180k0.009 vs. 0.165k0.010%).

Research Report 277

SIEGEL et al.

bilateral traits [21, 221. The bilateral traits measured in this experiment included skeletal, muscle, respiratory, and digestive organs. RA was measured for each trait and as an average of all bilateral traits. The only signrficant effect for the average RA of all bilateral traits was a line x feeding interaction: RA under Regimen F was greater for Line B (1.820.1) than for Line A (1.4+0.1%), while for Regimen D there was no difference between lines. Moreover, for seven of the eight bilateral measures, RA was greater for Line B than Line A. The exception was ceca length RA was the same (1.0+0.2) for both lines. RA for the eight bilateral traits measured was greatest for lung (4.5205%) and least for shank weight (0.620.1%). For the other bilateral traits the RA was 0.9 for shank length, 1.0 for ceca length, 1.0 for I! minor weight, and 1.1,13,and 1.7forR major length, weight, and width, respectively.

CONCLUSIONS AND APPLICATIONS 1. This paper describes an experiment designed to compare performance of two broiler lines differing in growth and yield, when reared to 12 days of age under full and diluted feeding regimens containing dietary levels of 10,100, or 300 IU/kg of vitamin E. Thereafter both lines were reared under the same feeding program and the 10 IU/kg dietary level of vitamin E. Performance criteria included a range of growth- and health-related traits. 2. Generally there was a trade-off between lines in allocation of resources. For healthrelated traits, faster growing, higher yielding Line A was inferior to Line B. Concomitantly, full feeding the undiluted diet to 12 days of age, while enhancing body weight and feed efficiency, was inferior for health-related traits (e.g., resistance to E. coli, heterophiVlymphocyteratios, and sheep red blood cell antibody titers) to a diet diluted with 50% bran to Day 5 and 20%bran to Day 12. 3. There was directional asymmetry, with breast muscles on the left side being larger than those on the right side. When treatmentswere sigdkant they influencedweight and width but not length of the R major muscle. Lung weight and ceca length showed antisymmetry. For seven of eight bilateral measures relative asymmetry of bilateral traits, an indicator of developmentalinstability, was greater for Line B than Line A. 4. Effects of feeding the high level of vitamin E to 12 days of age were nil, or when positive were in most cases age, sex, andlor line specific. For example, the high level had positive effectsfor body weight, breast yield, and lung weight of females but had no effect on males. Mortality of chicks fed the high level was lower to Day22, with no effect to Day 41. Feeding the high dietary level of vitamin E reduced lesion scores resulting fromE. coli challenge in Line B while having no effect in Line A.

REFTERENCESAND NOTES 1.K.tsnb.t, M.N., P.B.Sitgel, and EA Dundnglon, 1988. Organ growth of selected lines of chickens and their R crosses to a common body weight or age. Theor.

Appl. Genetics 7 4 S 5 4 4 .

2. LiIburn, M.S., 1998.Practical aspects of early nutrition forpoultry. J. Appl. Poultry Res. 7420-424.

3. Dibner, J.J., C.D. Knight, M.L Kitchell, C.A. &ell, AC.Downs, andPJ. Ivey, 1998.Ekrlyfeedingand

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

for males resulted from a difference between feeding regimens for Line B (F > D) but not Line A. Lung weights and ceca lengths were similar for Line A and Line B females. For males, however, lungs were heavier (0.437k0.012 vs. 0.39520.009%) and ceca were longer (18.620.4 vs. 17.4k0.2 cm)for Line B than Line A. The only difference between feeding regimens for these traits was for ceca length. Males from Regimen F had longer ceca than those from Regimen D (18.520.3 vs. 17.4k0.3 cm). Females fed the higher dietary level of vitamin E had heavier lungs than those fed the lower level (0.422+0.011 vs. 0.40720.010%). Leftright comparisons revealed antisymmetry for both lung weight and ceca length. Relative Asymmetries. Developmenta1 instabilities, which may result from genetic and/or environmental stressors, can be measured by relative asymmetries (RA) of

278

DILUTED STARTER AND VITAMIN E

devel ment of the immune system in neonatal poultry. J. Appof:Poultry Res. 7425436. 4. Noy, Yael p1II.d David SLLn, 1998. Metabolic response to eartynutntion. J. Appl. Poultry Res. 7437451.

19. Chickswere inoeulatedwith0.1 mLcontainink10-2 01:Kl incubated for 24 r in ! z z r p t e r i o r thoracic air sac.

5. si@, P.B. .ndEA. r 1 @ 0 1998. 4 Resource nses. Pages 95-98 allocations: Growth and immune in:Proc. 10th European Poultry&TJerusalem, Israel. 6. Pirard, M.,M. Plonatra, md J.M. Faure, 1998. Interaction of difEerent disci Lines in broilers: Nutrition and food intake behaviour. !ages 99-104 in: Proc. 10th European Poultry Conf., Jerusalem, Israel.

7.Nlr, I., 1998. Interaction of enetic stocks, growth rate, f e c d i n g r e r and metabofc diseases.Pages 105112 in: Proc. 1 h European Poultry Cod.,Jerusalem, Israel.

L and S. € I d % 1985.The performance 9. Piaof broiler chick during and following severe feed restriction at an early age. Poultry Sci. 64348-355. 10. Robinson, F.E, EL CLssen, J.A. Hansen, and D. Onderka, 1992. Growth rformance, feed efficiency, and the incidence of s k e g a l and metabolic disease in full-fed and restricted broiler and roaster chickens. J. Appl. Poultry Res. 133-41. P.B. 11. Nir, ,.I Z NitsPn, EA. Fhnnhq$o? cts of food intake resmction in young domestic f d % etabolic and enetic considerations. World’s Poultry Sci. J. 52251-26%. Sicgel, 1996.

12. M c I b y , S.G., EA. Goodd, D.A Rict, M.S. McNnlty, and D.G. Kenncdy, 1993. Improved performance in commercialbroiler flockswith subclinicalinfectious bursal disease when fed diets containing incrtastd concentrationsof vitamin E.Avian Path. 281-94.

13.Gore,AB.and M A Qureshl, 1997.Enhancement vitamin E after of humoral and cellular immunity emblyonic exposure. Poultry Sci. 76&991. G.F., W.G. B o t ~ cT ,.K. B e d , M.D. AerdrleL, 14. and C.A. Fritfs, 1998. Effects of dietary vitamin E on the immune system of broilers: Altered proportions of CD4 T cells in the thymus and spleen. Poultry Sci. 773529-537.

”,

15. Picard, P.B. Sicgel, C. Leierrkr, and P A Geraert, 1999. Diluted starter diet, growth performance, and digestivetract d e v e l T t in fast- and slow-growing broilers. J. Appl. Poultry .8122-131. 16.Chemical analysis of vitamin E in IU for low, medium, and hi@ levels were 11, 100, and% for the starter control dtet, and 12,120, and 300 for both the 50 and 20% dilute diets, respectively.

17. Wegmann, T.G. nnd 0. Smlthles, 1966. A simple hemagglutination system rcquirin small amounts of red cells and antibodies. Transfusion f:67-73. 18. Gross, W.B. nnd RS.Skgell983. Ehluation of hilllymphocyteratio as a measure of stress in %gL?vian DE. 27972-979.

20.Scores for pericardial and air sac lesions were: 1-none, %mild air sac, fmoderate air sac, 4-mild to moderate heart, S-extensive heart, 6death between time of challenge and scoring for lesions. 21. Ypqg,A, EA. DnnniagtOn, and P.B. Siegel,1998. Developmental stability in stocks of White Leghorn chickens. Poultry Sci. 7616321636.

22. Bilateral differencesof left minus right (L- R for each trait were tested for fluctuating asymmetry (&A), defmed as mean zero with normal distribution; directional asymmetry @A), defmed as mean not zero with normal distribution; and antisymmetry (AS), defined as mean zero with a distribution that was not normal. Each signed (+ or -1 bilateral aqmmet (L R was tested for nonnalitywth mean zeroby Wand one-sample t-test. Relative asymmetries(L- W[(L + R)E]) x 100 and feed efficiennes were transformed to arc sine square roots prior to statistical analysis. Organ weights were analyzed relative to body weight ([organ weightbody weight] X 100) with the latter transformed to arc sin square roots prior to statistical ana is. Body weights were transformed to common logarit& nor to statistical analysis. All traits were analyzed by &OVA except mortality,which was analyzed by Chi-square.

23. Borbn, RR and J.S. Harrison,1969. The relative differential leucocyte count of the newly hatched chick. Poultry Sci. 4E2451-453.

24. ZnlkitU, I. and P.B. Sicgel, 1994. Heterophil to lymphocyte ratios during perinatal and neonatal stages in chickens. Br. Poultry scl. 35:309-313. 25. Gross, W.B. and H.S. Siegel, 1983. Evaluation of heterophiVlymphocyte as a measurement of stress in chickens. Avian Dis. 27972479.

26.Bocl-Ampon~em,E.,EA. DW&@O~ and P.B. Sicgel, 1998. Diet and humoral responsiveness of lines of chickens divergent selected for antib response to sheep red blood ceg. Avian Dis. 42565-5 1.

9

27. Ubosl, C.O., EA. Dondngton, W.B. Gross,and P.B. Siegel, 1985. Divergent selection of chickens for antibody res nse to sheep erythrocytes. Kinetics of grimary anBOsecondary immunizations. Avian Dis. 9347-355. 28. Boa-Amponsem, K, EA. Dnnnington, K.S. Baker, and P.B. Sicgel, 1999. Diet and immunological memory of lines of White Leghorn chickens divergently response to sheep red blood cells. selected for antib Poultry Sci. 7 8 A a 7 0 . 29. p i n s n l - ~ a nde Laan, M., P.B. SiWl, and SJ. Lamod. 1998. Lessons from selection emeriments of immune response in the chicken. Poultry ind Avian Biology Rev. 9125-141.

ACKNOWLEDGEMENTS Appreciation is expressed to S.H. Price for technical assistance and S.I. Jackson for manuscript preparation.

Downloaded from http://japr.oxfordjournals.org/ by guest on May 25, 2015

8. cllh.ner, A,N. Deb, R YIlnlg andY. Lnvi, 1998. Reduced stress tolerance in fast growing broilers. Pages 113-117 in: Proc. loth Europcan Poultry Conf., Jerusalem, Israel.

&:zk$)