Biomedical subjects

E A Dunnington

Publications and source records attributed to E A Dunnington.

At least 19 recordsLinked to original sources

PubMed2001

Effect of route of inoculation on humoral immune response of White Leghorn chickens selected for high or low antibody response to sheep red blood cells.

Effects of route of SRBC inoculation and antigen dosage on primary and secondary antibody response of White Leghorn lines selected for high (HA) or low (LA) 5-d antibody response to a single i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC were studied in two trials. In the first trial, chicks from parents of generation S24 of each line were randomly assigned to one of four treatments. At 35 d of age, they were inoculated into the brachial vein with 0.1 mL of 0.25% suspension of SRBC or into the breast muscle with 0.1 mL of 0.25, 2.50, or 25.00% SRBC. Plasma SRBC antibody was measured 3, 6, 10, and 20 d later. In the second trial, chicks from parents of generation S25 of each line were randomly assigned to treatment groups. At 28 d of age they were inoculated with 0.1 mL of 0.25% SRBC into the brachial vein, 0.1 mL of 25.00% SRBC into the thigh (T-L) or breast muscle (B-L), or 0.5 mL of 25.00% SRBC into the thigh (T-H) or breast muscle (B-H). Twenty-one days later, chicks (except five per group) were given a booster inoculation of 0.1 mL of 25.00% SRBC into the thigh muscle. Six and 10 d after each inoculation, plasma SRBC antibody, IgG, and IgM titers were measured. The SRBC antibody titers after primary i.v. inoculation with SRBC were always higher for HA than LA chicks. When inoculations were i.m., differences between lines varied with dosage. Low dosages inoculated into the breast failed to induce line differences consistently, whereas at higher dosages, titers were greater for HA than LA chicks regardless of inoculation site. For Line LA, inoculation into the thigh elicited higher titers than inoculations into the breast. Antibody titers to the booster inoculation of SRBC were similar for the lines.

Animals↗

PubMed2000

Antibody responses to different dosages of sheep red blood cells in lines of chickens selected for high and low antibody response to sheep red blood cells.

Temporal patterns of SRBC antibody response after primary and secondary inoculations were measured in White Leghorn males from lines selected 24 generations for high (HA) or low (LA) 5-d antibody titers to an i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC. Primary i.v. inoculations were administered at 50 d of age as 0.1 mL of either 0.025 or 0.25% suspension of SRBC. Antibody levels of SRBC were measured 3, 5, 7, 9, 11, 13, and 20 d after inoculation. Also, IgG levels were measured on samples obtained 3, 7, 13, and 20 d after inoculation. At 70 d of age, half of the cockerels in each line-dosage subclass were given a booster inoculation of 0.1 mL of 0.25% SRBC. The SRBC antibody was measured 3, 6, 9, and 13 d later in chicks both receiving and not receiving the second inoculation. Patterns of antibody response to SRBC dosage differed according to line, resulting in interactions of line by dosage by day. Concentrations of IgG were greater for Line HA than for LA at 7 and 11 d after inoculation with SRBC but not at 3 and 20 d. Antibody responses to the booster inoculation differed between lines with a dosage effect present for LA but not for HA chicks. The greater anamnestic response observed in LA than in HA chicks is explained in the context of the resource allocation paradigm.

Animals↗

PubMed1999

Effect of genetic selection and MHC haplotypes on lymphocyte proliferation and interleukin-2 like activity in chicken lines selected for high and low antibody production against sheep red blood cells.

Chickens from third generation matings of lines of chickens selected for high (HA) and low (LA) antibody production to sheep red blood cells (SRBC) and typed for MHC genotypes B13/13, B13/21, and B21/21 were used in this study. Chickens from both lines carried all the three genotypes B13/13, B13/21, and B21/21. To study T- and B-lymphocytes mitogenic activity, 12-week-old female chickens were injected intravenously with 0.2 ml of 9% SRBC and spleens were collected at 0, 6 h, and 6 day post-antigen injection (pAg). Isolated lymphocytes were incubated with either Concanavalin-A (Con-A) for T-cell activity, or Pokeweed mitogen (PWM) for B-cell activity and thymidine 3H uptakes were measured. To study the Interleukin-2 (IL-2)-like activity in the same lines and genotypes, splenic lymphocytes from 12-week-old chickens were passed through nylon wool columns to enrich the T-cell population. After a 24 h incubation with Con-A, the conditioned media (CM) were collected. The CM were tested for IL-2 like activity by determining whether they altered the proliferation of Con-A stimulated T cells. This proliferation effect was then compared to that of a reference conditioned media (RCM) prepared from K-strain birds and that were used as the standard for the assay. There was no significant difference (p > 0.05) in IL-2 like activity between HA and LA lines, however, the LA was significantly higher than HA (p < 0.05) in T- and B-cell mitogenic activity. The genotype B13/13 had significantly higher (p < 0.05) IL-2 like activity than the B21/21. The genotype B13/13 was also significantly higher (p < 0.05) in T- and B-cell mitogenic activity than the B21/21. At 0 h, pAg T- and B-mitogenic activity was significantly higher (p < 0.05) than 6 h. In summary, our results indicate that although the birds were selected for high antibody production to SRBC, their lymphocyte mitogenic activity was lower than those selected for low antibody production. Hence, humoral and cell-mediated immune responses appear to be under different genetic controls, and that selection for greater humoral response may be at the expense of cellular responses. Our results also suggest differences in IL-2 like activity production between chickens carrying different MHC B-haplotypes, and that genetic control of such activity is possibly linked to the MHC genes.

Animals↗

PubMed1999

Diet and immunological memory of lines of White Leghorn chickens divergently selected for antibody response to sheep red blood cells.

Antibody responses to a first, second, and third injection with SRBC, and growth were studied in lines of White Leghorn chickens selected for high (HA) or low (LA) 5-d antibody titers to an i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC. The experiment involved parallel studies on two groups of chicks hatched from the same matings of parental lines HA and LA at a 14-d interval. Chicks of each age-line subclass were fed either a high or low nutrient density diet from hatch onwards. When chicks of Hatches 1 and 2 were 28 and 14 d of age (doa) respectively, they were injected with 0.1 mL of 0.25% suspension of SRBC, and antibody titers measured 3 and 6 d later. A second and a third injection of the same concentration of SRBC was given to chicks of each age-line-diet subclass at 10-d intervals and antibody titers measured 3 and 6 d after each injection in different chicks randomly sampled from each age-line-diet subclass. After the first injection, antibody (primary) responses of HA chicks were higher than those of LA chicks regardless of age and diet. This difference (HA > LA) observed for the primary response was seldom evident in the responses to the second (secondary) and third (tertiary) injections. Antibody responses of LA chicks after the second and third injections were anamnestic. For HA chicks given the first injection at 28 doa, neither the secondary nor tertiary responses suggested anamnestic capacities, whereas there was apparent memory exhibited by the secondary and tertiary responses of HA chicks initially injected at 14 doa. The LA chicks were significantly heavier than HA chicks at all ages. Even though the higher nutrient density diet increased BW of chicks of both lines, its effect on memory responses was sporadic. The results of this experiment show that, even though divergent selection has been successful in the primary responses, correlated responses in immunological memory were not always observed, suggesting that the two types of responses might be under different genetic control.

Animal Husbandry↗

PubMed1999

Heterosis and developmental stability of body and organ weights at hatch for parental line broiler breeders and specific crosses among them.

Body, yolk sac, left and right shanks with toes, empty left and right ceca, left and right lungs, heart, and bursa of Fabricius weights were obtained at hatch for 50 chicks from each of five commercial broiler parental lines (three sire and two dam) and three F1 crosses involving them. Differences among stocks and between sexes were inconsistent among mating combinations. Although correlation coefficients between yolk-free chick weight with organ weights were generally stock specific, they were high (> 0.75) with shank weight, intermediate with heart and lung weights, and low (< 0.25) with ceca and bursa weights. Heart:lung ratios of all F1 crosses were greater than those for their respective parental lines; however, the degree of heterosis differed among populations. Developmental stability, as measured by percentage relative asymmetry, was less in two of the sire parental lines than in their respective dam lines and F1 crosses.

Analysis of Variance↗

PubMed1999

Kinetics of antibody responses in hens from chicken lines divergently selected for response to sheep red blood cells.

Changes in antibody titers to SRBC were monitored for 180 d after inoculation in hens from two lines divergently selected for 24 generations for high (HAS) or low (LAS) antibody response to SRBC. The HAS hens not only had a higher peak of antibody response (12.9 vs 9.4), but also showed greater persistence in maintaining antibody levels than LAS hens. As a result, HAS hens exhibited higher antibody titers for the 180-d assay period than LAS hens. Antibodies to SRBC were detected in all day-old chicks hatched from HAS eggs collected 10 to 14 d after inoculation as well as 92 to 119 d after inoculation. Only a portion (20 to 75%) of progeny for LAS hens had detectable levels of antibody during the same periods. Among responders, antibody titers were higher for HAS than for LAS progeny. There was a positive correlation among antibody titers taken at different times after the inoculation with SRBC.

Animal Husbandry↗

PubMed1999

Heterosis following long-term bidirectional selection for mating frequency in male Japanese quail.

Reciprocal crosses (sire line shown first and dam line second) among high (H) and low (L) selected lines and the randombred control line (C), which was the base population for the selected lines, were made after 40 generations of bidirectional selection for mating frequency of male Japanese quail. Significant heterosis for the selected trait was found only in crosses between Lines C and L, being 62 and 92% for LC and CL, respectively. Heterosis for percentage of maters was present in all crosses, ranging from 8% for HC and CH to 46% for HL. Three (HC, LH, and CL) of the six crosses had significant heterosis for both 4- and 8-wk BW. Heterosis for 4- and 8-wk BW was also significant for the HL and CH crosses, respectively. For area of the cloacal gland, heterosis was significant in five crosses. Although crosses tended to exhibit higher relative aggressiveness than their respective midparent means, heterosis for this trait was not significant. Reciprocal effects, although not important for most traits, were present for BW in crosses between Lines C and L and Lines H and C. In general, long-term selection for mating frequency of males changed the genetic basis of selected and correlated traits with considerable nonadditive genetic effects observed for most traits in specific crosses.

Animals↗

PubMed1998

Comparison of sex-linked dwarf genes in chickens from two sources when introgressed into unrelated genetic backgrounds.

1. Sex-linked dwarfing genes from 2 broiler stock origins (EU and US) were each introgressed into 2 White Leghorn populations that had been divergently selected for antibody response to sheep erythrocytes. 2. When the resulting backcrossed populations were 87.5% of their respective. White Leghorn line, non-dwarf pullets were assessed for body weights, shank lengths, immunoresponsiveness, age and body weight at sexual maturity, egg production, average egg weight, and duration of fertility. For measurements where there were no differences between non-dwarf pullets from the 2 origins of the dwarfing genes, then the dwarf pullets (which were full sisters to the non-dwarfs) were compared. 3. Shank length at 8 weeks of age and mature (24-week) body weights were higher for dwarf pullets from EU than US dwarf origin. Immune response and several egg production traits were higher for dwarf pullets from the high antibody backcross than from those of the low antibody backcross. 4. There were few differences in expression of the dwarfing genes from 2 origins in the unrelated backcross populations used in this study. Also each of the dwarfing genes, when introgressed into different genomic backgrounds, was not discernibly different in its expression in terms of antibody response or egg production characteristics.

Analysis of Variance↗

PubMed1998

Forty generations of bidirectional selection for mating frequency in male Japanese quail.

A bidirectional replicated selection experiment for high (H1 and H2) or low (L1 and L2) cumulative number of complete matings (CNCM) in male Japanese quail was conducted for 40 generations. In the S32 generation, a subline was taken from each selected line and selection was relaxed. In the randombred control line (C), CNCM and unselected traits changed significantly over generations. Means of the selected lines were adjusted each generation for deviations from the control means. After 40 generations of selection, there was a 21-fold difference in CNCM (59.4 vs 2.8) between Lines H1 and L1. Whereas means increased and variation decreased in the high lines, means decreased and variation increased in the low lines. Regressions of mean CNCM on generation of Lines H1, H2, L1, and L2 were 1.15 +/- 0.08, 0.61 +/- 0.08, -0.26 +/- 0.04, and -0.34 +/- 0.03, respectively. Although responses to selection were observed throughout the 40 generations in Line H1, the low lines appeared to have reached a limit to selection after the S30 generation. Relaxed lines provided supporting evidence for this conclusion. Mean CNCM decreased in the relaxed high lines to that of the control, whereas the low relaxed lines remained at the same level as their corresponding selected lines. Line H2 went into extinction in the 37th generation as a result of reduced fitness. Realized heritabilities of CNCM were 0.09, 0.07, 0.06, and -0.15 in Lines H1, H2, L1, and L2, respectively. As correlated responses to the selection, male quail in the high lines were heavier, exhibited greater relative aggressiveness, and had larger cloacal glands than those of the control and low lines.

Animals↗

PubMed1998

Hematocrit values in weight-selected and relaxed lines of White Rock chickens.

Hematocrits (PCV) were measured at 29 and 106 d of age (PCV1 and PCV2, respectively) in male and female White Plymouth Rocks. Four lines were used, two of which had undergone 40 generations of divergent selection for 8-wk BW (HWS, LWS), and two respective sublines (HWR, LWR), in which selection had been relaxed for five generations. At both ages, males and females did not differ for PCV in lines HWR, LWR, and LWS. For line HWS there was an age by sex interaction that resulted from an age effect for males but not for females, and from a sex effect at each age. At both ages, PCV was higher for the HW than the LW lines. Initially, there was no difference between the selected and their respective relaxed lines, but by 106 d, HWR chickens had a higher PCV than HWS chickens. In lines HWR and LWR, PCV increased with age. There was a negative correlation in HWS males for PCV1 with 28 and 56 d BW. The HWR males also had a negative correlation for PCV1 with BW at 28 d, but not between PCV2 and BW. The correlation for PCV1 with PCV2 was high and positive for HWR males and females.

Aging↗

PubMed1998

Mode of inheritance of unselected traits in lines of chickens selected for high or low antibody response to sheep red blood cells. 1. Resistance to marble spleen disease virus and juvenile body weight.

Two lines of White Leghorns that had undergone long-term selection for high (HH) or low (LL) antibody response to sheep red blood cell antigen(s) formed the nuclear lines for this experiment. Matings were made in a full diallel cross to produce in a single hatch from age-contemporary breeders the parental lines, reciprocal F1 and F2 crosses, and backcrosses for 16 progeny types. For males and females, there were parental line differences in BW to 42 d of age, after which there was decline between lines for males. Differences in BW between reciprocal F1 crosses and maternal heterosis declined with age, primarily reflecting dissipation of effects of egg weight. Heterosis of BW was dependent on the particular F1 cross and recombination effects were not important. At 50 d of age chicks were inoculated with either a 1 or 10% suspension of spleen extract from chickens infected with marble spleen disease virus (MSDV). A third group served as uninjected controls. Response to MSDV was evaluated by spleen weight 6 d after inoculation. Spleen weights relative to BW of control chicks were heavier for the HH than LL line with evidence from the crosses of sexlinkage and negative heterosis. Line LL chicks were more resistant to MSDV than Line HH chicks was F1 crosses intermediate to and different from either parental line with no evidence of heterosis.

Adenoviridae Infections↗

PubMed1998

Mode of inheritance of unselected traits in lines of chickens selected for high or low antibody response to sheep red blood cells. 2. Heterophils, lymphocytes, and hematocrits.

The nuclear lines for this experiment were White Leghorns that had undergone long-term selection for high (HH) or low (LL) antibody response to sheep red blood cell antigen(s). Sixteen progeny types consisting of parental lines, reciprocal F1 and F2 crosses, and backcrosses were produced in a single hatch from age-contemporary parents. At 30 d of age, blood was obtained from a random sample of 10 males per progeny type (n = 160) and slides prepared for subsequent determination of number of heterophils and lymphocytes. Twelve days later, blood was collected from random samples of 10 males and 10 females per progeny type (n = 320) for measuring hematocrits. There were no differences between parental lines for heterophils, lymphocytes, or the heterophil:lymphocyte ratio. Reciprocal effects were evident in the F1 crosses and directional heterosis was present in one cross but not the other. Neither maternal heterosis nor recombination effects were significant for either heterophils or lymphocytes. Although hematocrits were similar for males and females and parental lines, sex-linked and recombination effects appeared to be important.

Animals↗

PubMed1998

Effects of season and diet on tensile strength and mineral content of the equine hoof wall.

Studies evaluating nutritional and seasonal influences on hoof strength and composition in horses, as well as the scientific justification for feeding supplements to improve hoof quality, are lacking. The horseman and veterinarian need controlled studies in this area to make informed decisions. This project quantified, in 2 trials, relative elasticity, tensile strength, % moisture, and mineral composition of hooves of 48 mature Thoroughbred mares maintained on different nutritional/management regimens, sampled quarterly over 12 month periods. Tensile strength was positively associated with sulphur content. Per cent moisture was not significantly associated with tensile strength, relative elasticity, or mineral content measures. Results indicated that both seasonal trends and nutritional regimes greatly affected hoof wall strength and mineral composition.

Animal Nutritional Physiological Phenomena↗

PubMed1997

Tissue-specific alterations in insulin-like growth factor-I concentrations in response to 3,3',5-triiodo-L-thyronine supplementation in the growth hormone receptor-deficient sex-linked dwarf chicken.

Insulin-like growth factor-I (IGF-I) mediates many of the effects of growth hormone (GH). The regulation of IGF-I, independent of GH, is methodologically difficult to assess in vivo, as hypophysectomy results in derangement of many pituitary hormone axes in addition to GH, and a gene knockout model is not available. The recessive sex-linked dwarfing (SLD) gene (dw) in chickens results in a lack of functional target tissue GH receptors due to a variety of molecular defects, which provides a unique model for evaluating GH-independent regulation of IGF-I. In the present study, the impact of 3,3', 5-triiodo-l-thyronine (T3) on circulating and tissue IGF-I was determined in normal versus SLD birds. Adult, nonovulatory female normal and SLD chickens were restrict-fed 40 g of feed/kg bw/day containing 0, 0.5, or 1.0 ppm T3, resulting in supplementation levels of 0 (control), 20 (low dose), or 40 (high dose) microg T3/kg bw/day for 10 days. Samples of GH target tissues including liver, abdominal fat pad, skeletal muscle (pectoralis major), and spleen were extracted and assayed for IGF-I. Plasma T3, T4, GH, and IGF-I were determined by homologous RIA. Tissue GH binding was determined for hepatic membranes by radioreceptor assay. Under control conditions, dwarf chickens were markedly hypersomatotropic (33.3 +/- 4.1 ng GH/ml plasma; mean +/- SEM) compared to normals (2.4 +/- 3.9 ng/ml), and T3 supplementation reduced this to normal levels. Despite the high circulating level of GH in dwarfs, plasma IGF-I was low compared to normal controls (dwarfs 1.5 +/- .9 ng/ml; normals 5. 3 +/- .9 ng/ml; P = 0.004), but this difference was eliminated with low-dose T3. In this study, tissue IGF-I was undetectable in liver and pectoralis muscle in adults (55 weeks of age) of both genotypes, under all treatments. In contrast, adipose tissue IGF-I was relatively high and did not differ (P = 0.84) between genotypes under control conditions (normals 776.5 +/- 236.7; dwarfs 844.6 +/- 236.7 pg/mg protein), but was increased in normals and decreased in dwarfs, resulting in higher levels (P = 0.02) in the normal (1249.9 +/- 200.0 pg/mg protein) than in the dwarf genotype (558.4 +/- 200.0 pg/mg protein) at the higher level of T3 supplementation. This relationship was somewhat reversed in spleen, where T3 tended to decrease tissue IGF-I concentration in normals and increase it in dwarfs. The low level of plasma IGF-I despite nonmeasureable hepatic IGF-I tissue concentrations suggests that IGF-I synthesis by extrahepatic tissues contributes to the circulating pool of IGF-I. The relatively high control levels of adipose tissue IGF-I in the dwarf genotype further suggest that considerable IGF-I synthesis exists that is GH-independent in this extrahepatic tissue. The presence of GH action, however, may mediate the effects of other hormones that can influence local IGF-I production in this tissue, as reflected by the differential response to T3 supplementation between genotypes. The tissue-specific nature of the effect of T3 on IGF-I production supports an additional point of regulation of hormone action at the target tissue level.

Adipose Tissue↗

PubMed1997

Effect of tumor necrosis factor-alpha on progesterone production by granulosa cells in laying hens of different genetic lines.

In vitro progesterone production by granulosa cells in the presence or absence of human recombinant tumor necrosis factor-alpha (hrTNF-alpha) was measured at 10, 20, and 30 wk of egg production in White Leghorn hens selected for high (HA)- or low-antibody (LA) response to sheep red blood cell challenge. Isolated granulosa cells from the three largest preovulatory follicles (F1-F3) were incubated with 5 or 250 ng/ml hrTNF-alpha, and progesterone production was determined by the use of a validated radioimmunoassay. F1, F2 and F3 granulosa cells from HA hens produced more (P < or = 0.05) progesterone (140.8, 107.2, and 49.7 ng/ml) than LA hens (109.4, 78.9, and 26.9 ng/ml). The treatment of granulosa cells with hrTNF-alpha consistently inhibited (P < or = 0.05) progesterone secretion by all follicles among HA and LA hens, but not always at both doses. Generally, 5 ng/ml hrTNF-alpha was the maximum inhibitory dose. In the laying hen, a decrease in steroid production in response to cytokines may upset the steroid balance created by follicular hierarchy and inhibit or delay ovulation.

Animals↗

PubMed1997

Antibody transmitting ability of hens from lines of chickens differing in response to SRBC antigen.

1. Hens from White Leghorn lines selected for high (HA) or low (LA) antibody response to sheep red blood cells (SRBC) were inoculated with 0.1 ml of either 0.25% or 2.50% SRBC suspension. Eggs laid over the next 15 d were grouped into 5, 3-d collection periods and incubated. Maternal antibody titres were determined in chicks at hatch and 7 d after hatch. 2. In a subsequent experiment, hens of the 2 lines were inoculated with 0.1 ml of 2.50% suspension of SRBC, and eggs laid on days 10 to 13 after inoculation were incubated. Maternal antibody titres were determined in 15 and 18-d embryos as well as in chicks at 0, 5, 10, 15, 20, and 25 d after hatch. 3. Dosage of SRBC had no effect on the antibody titres in line HA; however, the higher dosage elicited greater antibody titres than the lower dosage in line LA. 4. Maternal antibodies were detected earlier in chicks of line HA (eggs laid on days 7 to 9) than those of line LA (eggs laid on days 10 to 12) regardless of dosage administered to the hens. 5. In both lines, antibodies specific to SRBC were observed on day 15 of incubation, with the frequency of responders greatest at hatch. The high frequency of HA responders was maintained for 15 d after hatch, whereas there was an immediate decline with age in LA responders. 6. It was concluded that lines HA and LA have diverged in the pattern of maternal antibody levels as a result of the divergent selection for antibody response to SRBC.

Aging↗

PubMed1997

Developmental stability in stocks of White Leghorn chickens.

The degree of asymmetry in bilateral morphological characters may reflect genetic and environmental stressors. Shank length and diameter, weight and length of the first primary wing feather, and distance between the junction of upper and lower mandibles and auditory canal (face length) were used to classify bilateral types and measure relative asymmetry (RA) in six genetic stocks. The stocks were the S23 generation of White Leghorn lines selected for high or low antibody response to SRBC, sublines in which selection had been relaxed for eight generations, and reciprocal crosses of the selected lines. Differences were found among all stocks for the traits measured. Rankings among traits for RA in descending order were face length, shank diameter, feather weight, and shank and feather lengths. The RA of shank and feather lengths did not differ from each other. An overall RA composed of mean RA of the five traits showed that the two selected lines exhibited greater RA than the crosses between them. The RA of the two lines where selection had been relaxed was similar to that of selected lines. This research suggests that an overall RA created as a combination of RA of several bilateral traits can be a valid measure of genetic stress in chickens and provides a method of comparing developmental stability among populations.

Aging↗

PubMed1997

Dietary effects on immune response of fast-growing chicks to inoculation of sheep erythrocytes and Escherichia coli.

Responses to SRBC and Escherichia coli inoculations were measured during the early posthatch period in broiler cockerels fed diets differing in nutrient density. Diet A consisted of 20% protein and 2,685 kcal ME/kg and Diet B consisted of 24% protein and 3,146 kcal ME/kg. There was no effect of diet on antibody response of chicks inoculated at 10 d of age with 0.25, 2.50, 5.00, or 25.00% suspensions of SRBC. A significantly larger proportion of chicks, however, produced antibody at the 25.00% than at the 0.25% dosage of SRBC. When inoculated at 15 d of age with 10(-6), 10(-4), or 10(-2) dosage of E. coli, there were no significant diet by dosage interactions for lesion scores, or relative change in BW 24, 48, and 120 h after inoculation. There were differences among E. coli dosages for severity of lesions and mortality, with rankings being 10(-2) > 10(-4) > 10(-6). Lesion scores and mortality were higher for the chicks fed Diet B than those fed Diet A. Also, deleterious effects of E. coli on BW 24, 48, and 120 h after inoculation were greater for chicks fed Diet B than for chicks fed Diet A. Responses to inoculations of SRBC and E. coli of broilers fed a diet with a lower nutrient density were equal or superior to those of broilers fed a diet with a higher nutrient density.

Animal Feed↗