Biomedical subjects

A Cahaner

Publications and source records attributed to A Cahaner.

At least 37 records · Page 2Linked to original sources

PubMed1999

The effects of the naked neck (Na) and frizzle (F) genes on growth and meat yield of broilers and their interactions with ambient temperatures and potential growth rate.

High ambient temperatures (AT) decrease the growth of broilers because of difficulty in dissipating heat through the feather coverage. Broilers selected for higher growth rate eat more and generate more heat per unit of time; hence, they may become more sensitive to high AT. Reduced feather coverage, either by decreased number or by modified shape, may help birds to dissipate internal heat more efficiently. Two broiler stocks were studied; each was segregated for four genotypes with regard to the genes for naked neck (Na) and frizzled feathers (F): heterozygous naked neck (Na/na f/f), heterozygous frizzle (na/na F/f), double heterozygous (Na/na F/f), and normally feathered (na/na f/f). One stock had a high growth rate (GR) similar to current commercial broilers, whereas the second stock had a lower GR. Birds of each stock, genotype, and sex were reared under constant standard AT (24 C) or high AT (32 C). Body weight at 4 and 7 wk, weight gain (WG) from 4 to 7 wk, breast meat yield, and feather weight were recorded. Reduction in WG from 4 to 7 wk because of high AT was greater in high-GR birds than in low-GR birds, but, in both stocks, the high AT effect was greater on normally feathered birds than on the other three genotypes. AT 32 C, in low- and high-GR stocks, the F allele increased WG from 4 to 7 wk and increased the BW at 7 wk of fully feathered (na/na) broilers but had no effect on meat yield. The effects of the Na allele were similar to or greater than those of the F allele. The Na allele did not affect breast meat yield of low-GR broilers but increased it significantly in high-GR broilers. Combining the two allles resulted in an additive effect, which was more pronounced in the high-GR stock.

Alleles↗

PubMed1998

Thermoregulation in naked neck chickens subjected to different ambient temperatures.

1. Heterozygous (Na/na) naked neck chickens and their normally feathered (na/na) sibs, were exposed to constant ambient temperatures (Ta) ranging between 15 and 35 degrees C and 12h: 12h diurnal high:low temperatures of 15 degrees C:35 degrees C. 2. No significant effect of genotype was obtained in weight gain and food intake. However, the naked neck birds tended to gain somewhat more weight at high Ta and consume more food at low Ta. 3. At 35 degrees C Na birds showed better regulation of body temperature (Tb) and demonstrated considerably higher radiation from the neck. 4. The greater food intake of the naked neck chickens at 15 degrees C was associated with significantly higher packed cell volume, haemoglobin concentration, heart and liver size. These appear to involve both higher heat production and haemodynamic changes to accommodate the higher oxygen demands of the naked neck chickens at low Ta. 5. The results indicate the ability of the naked neck chickens, on the one hand to thermoregulate at low Tas and, on the other their slightly better capacity to maintain Tb at high Tas. However, no genotype advantage was obtained under diurnal cyclic temperature conditions.

Analysis of Variance↗

PubMed1998

Comparative effects of added sodium chloride, ammonium chloride, or potassium bicarbonate in the drinking water of broilers, and feed restriction, on the development of the ascites syndrome.

A hypothesis that the ionic composition of drinking water might affect development of the ascites syndrome in broilers was investigated in two trials. The first trial comprised four groups of 650 male chicks. A control treatment was normal tap water and the other three treatments comprised the addition to the tap water of 1,000 mg/L sodium as NaCl, 5,000 mg/L NH4Cl, or 5,000 mg/L KHCO3, supplied from age 2 to 47 d. At Day 28, equally sized subsets of these groups were moved to individual cages, where they received a severe exposure to ambient cold. The development of the ascites syndrome was monitored by measurements of hematocrit and arterial blood oxygen saturation (PaO2) by oximetry, body weight, and examination of dead birds for cause of death. Mortality from ascites in cold-exposed birds from Days 28 to 47 was 28, 48, 40, and 16% in the tap water, NaCl, NH4Cl, and KHCO3 groups, respectively; only the NaCl mortality was significantly different from the tap water mortality. The KHCO3 treatment increased PaO2 (compared with tap water treatment) at Day 28 by 5.5% and at Day 35 by 10.5%, but not at Day 42. The KHCO3 caused a reduction in body weight, which was 13% less than the tap water group at Day 42, probably due to a chronic toxicity. The second trial specifically examined the same parameters with lower water levels of KHCO3 (3,000 and 1,000 mg/L), in comparison to a 10% feed restriction protocol, in order to clarify whether the increased PaO2 was due to a specific effect of the KHCO3 or was a metabolic manifestation of a reduced growth rate. The 3,000 mg/L KHCO3 treatment had no effect on PaO2, but the 1,000 mg/L treatment augmented PaO2 by 5.3% at Day 35 (but not at Days 28 or 42), without reducing the final body weight. The feed restriction group showed an elevated PaO2 of 5.4% at Day 35 (but not at Days 28 or 42), with no reduction in the final body weight. The inclusion of 1,000 mg/L of KHCO3 into the drinking water of broilers or a temporary 10% feed restriction may be means to augment PaO2.

Ammonium Chloride↗

PubMed1997

Comparative evaluation of three commercial broiler stocks in hot versus temperate climates.

Hot climate is a major limiting factor of broiler production in tropical and subtropical regions. The use of standard stocks in hot climates may result in large economic losses because genotypes selected in temperate climates may respond differently to the high ambient temperatures in hot regions or seasons. The summer and fall in Izmir, Turkey, provided the natural hot and temperate climates, respectively, for this study. Broiler chicks were obtained from three commercial stocks, all bred in temperate climates. Male and female chicks, 60 per pen, were housed in four pens per stock per season. Individual BW was determined at hatch, and at 4 and 7 wk of age. Feed consumption and efficiency were determined per pen. Feathering was scored at 4, 5, and 6 wk of age. Body temperature was measured twice on three birds per sex per pen, 16 h and immediately before slaughter, and feather weight was determined for each of these birds. The two seasons clearly differed in ambient temperature at the broiler house, and consequently, BW at 7 wk was significantly lower in the summer than in the fall in all stocks, with an average reduction of 23%. The season effect was largest (33.5%) on BW gain from 4 to 7 wk, along with 23 and 15% reductions in feed consumption and efficiency, respectively, during these 3 wk. A significant season by stock interaction was detected for BW gain from 0 to 4 wk and 4 to 7 wk. The three stocks exhibited similar 4- to 7-wk BW gains under the temperate fall climatic conditions, but differed significantly in the summer. These differences were not related to normal differences in feather coverage or body temperature, suggesting that standard broiler stocks must be tested in hot climates in order to find the one most suited to these conditions.

Analysis of Variance↗

PubMed1997

Performance of naked neck and normal broilers in hot, warm, and temperate climates.

Chickens suffer at high ambient temperatures because their feather coverage hinders internal heat dissipation. Naked neck broilers (Na/na) and their normally feathered sibs (na/na) were evaluated in three natural climates. Three experiments were conducted in Turkey, during the summer in the extremely hot region of Adana (Ad-Sm), and in the moderate region of Izmir during the spring (Iz-Sp) and summer (Iz-Sm), always following the same experimental protocol. Ambient temperatures averaged 19, 28, and 32 C in Iz-Sp, Iz-Sm, and Ad-Sm, respectively. About 300 birds per genotype were included in each experiment. Feather weight was lower by about 20% in Na/na broilers than in na/na ones, independent of climate, sex, and age (6 or 7 wk). The Na/na broilers exhibited higher breast weight in all cases, from 2.5 to 10.9% higher than their na/na counterparts. Body weight gain from 4 to 7 wk (BWG4-7) clearly reflected the differences in ambient temperature among climates. The effect of the Na/na genotype on BWG4-7 interacted with climate and sex. In the hottest climate (Ad-Sm), both male and female Na/na broilers exhibited a highly significant advantage over their na/na counterparts. In the more moderate climate (Iz-Sm), the Na/na genotype exhibited superior growth only among males, and the magnitude of this advantage was lower than in Ad-Sm. In the cool temperate climate (Iz-Sp), BWG4-7 and BW7 (BW at 7 wk) means were similar for both genotypes. In Iz-Sp, feed efficiency (FE) of the Na/na birds was lower by about 4%, but in the two summer climates (Iz-Sm and Ad-Sm), FE of the Na/na birds was about 9% higher than that of their na/na counterparts. Body temperature was lower in the Na/na broilers than in their na/na counterparts; in all cases, the difference increasing with ambient temperature. The results indicate that the reduction in feather coverage provided relative heat tolerance, and therefore, under hot climates the Na/na broiler were superior to their normally feathered counterparts. It is concluded that naked neck broilers should be preferred in hot climates.

Animals↗

PubMed1996

Hematocrit values and mortality from ascites in cold-stressed broilers from parents selected by hematocrit.

A hypothesis that the relative hematocrit value of broilers is inherited and can serve as an indicator of partial resistance to the ascites syndrome in cold-stressed broilers was shown to be valid in a field trial. Hematocrits were determined for male and female grandparent breeding stocks. Matings were then made between low (LL), low-medium (LM), medium-high (MH), and high (HH) hematocrit parents: LL x LL, LM x LM, MH x MH, and HH x HH. The progeny of HH parents had higher hematocrit values than the progeny of lower hematocrit parents (P < 0.0001). Exposure of the progeny from all the parental groups to an ascites-predisposing cold environment caused higher losses from ascites in the progeny of the HH parents (P < 0.0001). The progeny of LH parents had an increased mortality from causes other than ascites (P < 0.0001). This work suggests that elimination of birds with HH in broiler breeding programs may be desirable where cold-induced ascites is an important problem.

Age Factors↗

PubMed1996

Genetic differences and heritability of antibody response to Escherichia coli vaccination in young broiler chicks.

Broiler chicken lines, selected divergently for high (HC) or low (LC) antibody titer to Escherichia coli vaccination at an early age, were evaluated for antibody response at the S5 and S9 generations of selection. The full-pedigreed populations consisted of about 300 and 400 chicks per line in S5 and S9, respectively. At S5, all chicks were vaccinated at 10 d of age (VA10) and antibody titer was determined twice for each chick, at 8 and 12 d postvaccination (dPV). At S9, each line was divided into two equal groups; in the HC line, one group was vaccinated at 8 d of age (VA8), and the other at 10 d of age (VA10), whereas in the LC line, one group was VA10 and the other was VA12. Antibody titers were determined twice for each chick, 8 and 10 dPV. The effects of line, age at vaccination (VA), and days for antibody development (dPV) were tested, and the heritability of antibody titer was estimated for each line-VA-dPV set of data. The HC and LC lines differed significantly in the maturation process of their immune systems. The percentage of chicks with detectable antibody at 18 d of age (VA10-8 dPV) among HC chicks was significantly higher than among LC chicks (85 vs 48% in S5 and 96 vs 63% in S9). In S9, 90% of the HC chicks had already responded at 16 d of age and 100% at 18 d of age, whereas among the LC chicks, only 62% were positive at 18 d of age, increasing to no more than 98% at 22 d of age. The results demonstrates that selection of antibody titer to E. coli vaccination at 20 d of age actually affects the earliest age of immune response, as the immune system of the HC chicks matures earlier than that of the LC chicks. The HC S9 chicks at 8 dPV exhibited a fourfold higher antibody titer than their LC 8 counterparts. This difference further increased at 10 dPV, indicating that the lines differed not only in the level of antibody at a specific age, but also in their rate of antibody titer development. The highest estimate of heritability was very similar in both lines (0.44 and 0.42 in HC and LC, respectively). However, in the HC line this heritability was exhibited at 18 d of age, and only at 22 d in the LC line. Thus, both lines have a similar amount of genetic variation for early immune response, but in the HC line this variation is fully expressed 4 d earlier than in the LC line. These results suggest that selection for high or low antibody response in young chicks results in early or late antibody production, respectively. To maximize the efficiency of selection for early immune response, one must determine the best vaccination age and timing of antibody evaluation in any given population, and these values must be revalidated and updated as selection proceeds.

Age Factors↗

PubMed1996

Associations of individual genomic heterozygosity, estimated by molecular fingerprinting, and of dam major histocompatibility complex with growth and egg production traits in layer chickens.

Growth and egg production data from F2 layer chickens produced from a mating of MHC-heterozygous B15B44 sires to B15B44 and B15B43 dams were analyzed for associations with the level of the individual's genomic heterozygosity and dam MHC. The F1 sires and dams were produced from mating of birds from two genetically distinct, highly inbred lines. Genomic heterozygosity (expressed as composite band frequency, CBF) was estimated based on the average proportion of shared bands of individual birds compared to a composite pool of Hinf I-digested DNA samples from the two inbred lines. Birds from dams of genotype B15B43 had significantly greater BW than progeny from B15B44 dams at 6 wk and thereafter. Dam MHC genotype differences were also significant for number of eggs laid from 20 to 28 wk of age, with B15B43 progeny being superior. Negative regression coefficients at hatch, 32 and 44 wk were observed for the effect of CBF on BW of progeny from B15B43 dams and at hatch and 32 wk from progeny of pooled dam genotypes. Similarly, negative regression coefficients were observed for the association of CBF with number of eggs within progeny from the B15B44 dam MHC genotypes at 20 to 28 wk and total period recorded, and at 28 to 36 wk for progeny from B15B43 dams. The CBF regression coefficients and the differences among progeny based on dam MHC genotypes suggest that individual heterozygosity and MHC genotype may be associated with BW and egg production in chickens.

Animals↗

PubMed1995

Effects of dietary protein under high ambient temperature on body weight, breast meat yield, and abdominal fat deposition of broiler stocks differing in growth rate and fatness.

The effect of dietary protein on growth, feed intake and efficiency, abdominal fat deposition, and breast meat yield was investigated in broiler males from a commercial stock (WI) and from experimental stocks selected for low (LF) or high (HF) abdominal fat. All birds were kept at constant high ambient temperature (32 C) and were provided with low- (LP) or high-protein (HP) diets from hatch until 8 wk of age (Experiment 1) or from 4 to 8 wk of age (Experiment 2). In both experiments, HP diet significantly increased 4- to 8-wk BW gain in the LF and HF stocks but reduced it in the WI stock as compared with the LP diet. Abdominal fat, as percentage of BW, was almost twofold higher in the HF birds than in the LF ones, with WI mean being intermediate. In contrast to the HF and WI birds, in which abdominal fat decreased with increased protein intake, abdominal fat was not affected by dietary protein in the LF stock. The HP diet substantially increased breast meat yield in LF birds but not in the WI birds, with HF birds exhibiting intermediate increase in breast meat weight. It was concluded that birds of varied inherent growth rate and tendencies toward protein and fat deposition respond differently to dietary protein level under heat stress.

Adipose Tissue↗

PubMed1994

Differences in major histocompatibility complex frequencies after multitrait, divergent selection for immunocompetence.

White Leghorn chickens from lines selected for four immune-response traits (IR lines) were serotyped for B system alloantigens characterizing the haplotypes and genotypes to examine the effect of divergent selection for multitrait immunocompetence on MHC haplotype and genotype frequencies. The selected lines were derived from the Ottawa Strain 7. The selection index included four immunocompetence traits: antibody production against Mycoplasma gallisepticum (MG) and Pasteurella multocida, inflammatory response to phytohemagglutinin, and reticuloendothelial carbon clearance. The four lines include two replicates of high and low multitrait-immunocompetence lines. After four cycles of selection, significant differences (P < .05) in several B system haplotype frequencies were observed, both among IR lines and between the IR lines and the Ottawa Strain 7. The B2 haplotype frequency was greater in all IR lines than in the Ottawa Strain 7. The B21 frequency was less in both high lines than in the Ottawa Strain 7. In comparisons among lines, frequencies of B21 were greater in both replicates of the low lines and the B12 and B19 frequencies were significantly greater (P < .05) in the high lines. A gene substitution model showed effects (P < .10) of specific haplotypes on MG and on the index. The B2 haplotype had a positive effect associated with MG. Haplotype B21 was positively associated with the multitrait index. Haplotype B13 had a negative effect on both MG and the index. Significant differences (P < .01) in genotype frequencies were also noted among the IR lines. Associations between specific MHC haplotypes or genotypes and immune-response traits may offer insight into MHC-mediated mechanisms of disease resistance.

ABO Blood-Group System↗

PubMed1994

Direct and correlated responses to multitrait, divergent selection for immunocompetence.

Leghorn lines had been selected for an immunocompetence index based on four traits: antibody production to Mycoplasma gallisepticum (MG) and Pasteurella multocida (PM) vaccines, reticuloendothelial clearance of colloidal carbon (CCA), and cell-mediated, wing web response to phytohemagglutinin (PHA). The purpose of this study was to produce replicated lines of chickens with divergent levels of multitrait immunocompetence by index selection. The objectives of analyses of Generations 5 to 7 of this study was to characterize these lines with respect to immune-response traits, correlations among these traits, and correlated responses in other important production traits. Differences (P < .05) existed between the lines selected for high or low immune response and between the two replicates in mean breeding values and in individual immune-response traits. Averages of heritability estimates, weighted by number of offspring and pooled across three generations (two cycles of selection), estimated by using sire variance components and parent-offspring correlations were, respectively, .16 and .09 for the index, .31 and .08 for MG, .21 and -.02 for PM, .06 and .05 for CCA, and .08 and .12 for PHA. Realized heritabilities (response divided by effective selection differential) pooled across the two selection cycles, were .19 and .11 for the index, .06 and -.01 for MG, .44 and .32 for PM, 1.52 and -1.21 for CCA, and .48 and .15 for PHA, for Replicates 1 and 2, respectively. Phenotypic correlations among traits were generally small, and several estimates were negative. Estimates of genetic correlation varied widely. Juvenile and adult body weights, age of first egg, 32-wk egg weight, and rate of egg production were analyzed to evaluate effects of selection on these traits of direct economic importance. Very few differences were noted.

Age Factors↗

PubMed1994

Parental effect on the humoral immune response to Escherichia coli and Newcastle disease virus in young broiler chicks.

Genetic and environmental variables influence animal resistance to disease infection. In addition, maternal effects were also found in studies with egg-type chicken lines. In our laboratory, meat-type chicken lines were divergently selected for either early or late maturation of the immune system, based on family and individual antibody responsiveness at 10 d of age. The high-antibody (HC) and low-antibody (LC) lines differed significantly in the early immune response to Escherichia coli, to Newcastle disease virus (NDV) vaccination, and to several other immune functions. Reciprocal crosses between the HC and LC lines were performed over 2 yr at three different locations. Immune responses to E. coli and NDV vaccination provided separate estimates of maternal and paternal effects. Dam effect on immune response to E. coli vaccine was significantly larger than sire effect; the antibody titer in both reciprocal crosses was intermediate between the parental lines, but the mean titer of the HC x LC cross was significantly lower than that of the LC x HC cross. Similar, but not significant, ranking of crosses was observed for the response to NDV. Evidently, the level of the offspring humoral immune response was more a dam than a sire effect.

Animals↗

PubMed1993

DNA fingerprint bands applied to linkage analysis with quantitative trait loci in chickens.

An efficient approach to detect association between quantitative traits and bands of DNA fingerprint patterns uses intra-family tail analysis, which compares fingerprints of DNA mixes from individuals at the two tails of a phenotypic distribution. In analysis of 67 paternal half-sibs of a meat-type chicken family, of 57 sire bands generated by two probes, one sire-specific band (S6.6) was associated with abdominal fat deposition. The band effect was estimated by a linear model analysis to be 0.88 standard deviations, or about 30% of the family mean. The association between band S6.6 and abdominal fat was further examined by testing progeny of paternal half-sibs of the chickens which were used in the tail analysis, establishing genetic linkage between the DNA marker and a genetic locus affecting abdominal fat deposition.

Adipose Tissue↗

PubMed1993

Major histocompatibility complex class IV restriction fragment length polymorphism markers in replicated meat-type chicken lines divergently selected for high or low early immune response.

Information on MHC may improve the efficiency of selection for immunological traits via the application of marker assisted selection or by selecting directly for a specific restriction fragment length polymorphism (RFLP) band or MHC haplotype. An experimental procedure is presented here for identifying MHC genes that are related to early immune response. A Class IV cDNA clone was used to probe Southern blots of erythrocyte genomic DNA from chickens. Chickens were taken from the second (S2) and third (S3) generations of replicated lines divergently selected for high antibody response (HC1, HC2) or low antibody response (LC1, LC2) to Escherichia coli vaccination at 10 days of age. These selection criteria have been found to be associated with other immunological parameters. The hypothesis that these selected lines differ in their MHC loci was evaluated by comparing the frequencies of MHC RFLP markers (single RFLP bands) and haplotypes (patterns of RFLP bands). The significant differences between LC and HC in the frequency of many MHC RFLP bands and of five MHC haplotypes indicate that early antibody production is influenced by MHC genes. The reliability of the association between the selection and frequency differences was tested and proven in most cases by analysis of the replicated lines. These differences in RFLP markers represent a change in allelic frequencies in MHC genes, probably due to selection. The results imply a connection between the Class IV genes and early antibody production, and they show the potential of prospective breeding not only by immunological phenotype but also by genotype (i.e., using RFLP markers of the MHC).

Animals↗

PubMed1992

Immunological parameters in meat-type chicken lines divergently selected by antibody response to Escherichia coli vaccination.

Our group has established two lines of meat-type chickens divergently selected for early (HC line) and late (LC line) antibody responsiveness at 10 days of age to immunization with inactivated pathogenic Escherichia coli bacteria. The question addressed in the study presented here is whether this selection has changed other immunological responses, increasing the overall 'early' immunocompetence. Broilers of the third and fourth generations (S3 and S4) of the selected lines (HC and LC) and a control, unselected line (CT) were vaccinated at 10 days of age with E. coli vaccine, Newcastle virus vaccine (NDV), sheep erythrocytes (SRBC) or bovine serum albumin (BSA). Line-HC chicks exhibited higher antibody titers to E. coli, NDV and SRBC than CT or LC chicks. At 20 days of age HC chicks demonstrated a higher total protein and a higher beta- and gamma-globulin levels in their serum. At 21 days of age, HC chicks cleared carbon particles faster than LC chicks. Peripheral blood lymphocytes (PBL) from HC chicks vaccinated with E. coli vaccine, proliferated in vitro more actively in the presence of the stimulating antigen than the PBL of LC chicks. Peripheral blood lymphocytes (PBL) obtained from HC-line chicks exhibited a higher proliferative response to concanavalin A (Con A)-, phytohemagglutinin (PHA)- or pokeweed mitogen (PWM)-stimulation than LC PBL. These results demonstrate that the selection for high or low antibody response to E. coli at a young age resulted also in a significant change in the response of other parameters of the immune system. The high response to E. coli was found to be associated with a high antibody response to other antigens (NDV and SRBC), increased phagocytic activity and increased proliferative response to antigen or mitogens. The selection most probably affected early immunocompetence.

Aging↗

PubMed1992

Effect of different dietary levels of protein on fat deposition in broilers divergently selected for high or low abdominal adipose tissue.

1. Male broilers selected for high (HF) or low (LF) abdominal fat were fed from 8 to 53 d of age on diets containing different concentrations of protein: according to N.R.C. (1984) recommendations (IP), 14% lower (LP) or 14% higher (HP). 2. The growth of LF birds fed on the LP diet was depressed until 35 d of age, but did not differ from the other groups later on. 3. The HF birds had heavier adipose tissues (AT) (g/kg body weight) than the LF birds. Significant line by diet interactions indicated a difference in magnitude of the response of the lines to dietary protein content. 4. Fat concentration of the AT and skin was higher, and in the tibia lower in the HF than in the LF birds. The fat concentration in liver and in breast muscle was not affected by line or by diet. 5. The ratio of saturated plus monoenoic fatty acids to polyenoic fatty acids, considered as an index of fat synthesis, was higher in the abdominal adipose tissue (AAT) of HF compared with LF birds. In AAT, liver and in breast muscle, this ratio was inversely related to dietary protein content.

Adipose Tissue↗

PubMed1992

Restriction fragment length polymorphism analysis of major histocompatibility complex class IV (B-G) genotypes in meat-type chickens.

Restriction fragment length polymorphism (RFLP) was used as a molecular genotyping approach to characterize differences in major histocompatibility complex class IV genes in meat-type chickens. A high level of polymorphism was observed following digestion with each of the two restriction endonucleases PvuII and BglII. Examination of DNA from 54 chickens revealed 23 polymorphic fragments. Application of RFLP techniques in the analysis of family groups should make possible the determination of B-G genotypes in the meat type chickens.

Animals↗

PubMed1992

Replicated divergent selection of broiler chickens for high or low early antibody response to Escherichia coli vaccination.

Four sublines of broiler chickens were selected from a base population for three generations for high or low antibody response to vaccination with Escherichia coli at 10 days of age. Two sublines were selected for a high response (HC) and two for a low response (LC). Realized heritability estimates over three generations of selection for each pair of replicated lines averaged .23 in HC lines and .32 in LC lines. No correlated response in the important production trait, body weight at marketing age, was observed. The ability to survive pathogenic E. coli challenge with or without prevaccination showed no differences between the lines in the unvaccinated chicks, although following vaccination there was higher mortality and morbidity in the LC lines. These data suggest that the use of antibody response in young chicks to E. coli vaccine may be a useful genetic indication of more general disease resistance.

Animals↗