Antimicrobial activity of essential oils and structurally related synthetic food additives towards Clostridium perfringens.

AIMS: To assess the potential of essential oils and structurally related synthetic food additives in inhibiting the growth of Clostridium perfringens for the control of necrotic enteritis in chickens. METHODS AND RESULTS: The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Thirty-three of 66 oils/compounds exhibited > or =80% inhibition. Seven with the highest potency were further studied. The oils/compounds had MIC(95) values between 167 and 425 microg ml(-1). Most of them were tolerant to low pH (2.0) and exhibited minor or no inhibition of Lactobacillus isolates from the chicken intestine. When mixed with chicken ileal digesta, the oils/compounds retained their efficacy against C. perfringens, but had little effect on the total number of lactobacilli and anaerobic bacteria in the digesta. CONCLUSIONS: Some essential oils/compounds demonstrated good potential in controlling C. perfringens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has identified candidates of essential oils/compounds for in vivo studies for the control of necrotic enteritis in chickens.

Effects of zinc bacitracin, bird age and access to range on bacterial microbiota in the ileum and caeca of broiler chickens.

AIMS: Determining the effects of zinc bacitracin, bird age and access to range on bacterial microbiota in the ileum and caeca of broilers. METHODS AND RESULTS: 16S rRNA gene-based polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE) profiling, DNA sequencing and real-time quantitative PCR techniques were used. The richness of both ileal and caecal microbiota increased with chicken age. The microbiota from those birds of the same age demonstrated relatively similar PCR-DGGE profiles and tended to form closely related clusters in the relatedness analyses. Dietary treatment with bacitracin (50 mg kg(-1)) and access to range did not change the richness but altered the composition of the microbiota. The impact of bacitracin was particularly obvious in 3-day-old chicks. Lactobacilli were abundant in the caecal microbiota of 3-day-old chicks regardless of the dietary treatment with bacitracin. The access to range enriched Bifidobacterium in both the ileum and caeca. CONCLUSIONS: Bacitracin, bird age and access to range all influenced bacterial microbiota in the ileum and caeca of broilers, with bird age having the greatest apparent effect. SIGNIFICANCE AND IMPACT OF THE STUDY: Providing useful information for the development of antibiotic replacement therapy for poultry production.

Media for the aerobic resuscitation of Campylobacter jejuni.

The microaerophilic nature of Campylobacter jejuni has complicated its recovery from human and animal sources. In this study, enhancement of the growth and aerotolerance of C. jejuni ATCC 35921 in nutrient broth no. 2 (NB2) was investigated. The efficiency of recovery of C. jejuni in NB2 containing FBP (0.025% [each] ferrous sulfate, sodium metabisulfite, and sodium pyruvate), 5% laked horse blood, hemin, Oxyrase, or activated charcoal in an aerobic atmosphere was compared with that obtained under microaerophilic incubation. The shortest lag time (lamda) for cells grown aerobically was observed with NB2 supplemented with FBP, 5% laked horse blood, 0.01 g/liter of hemin, or 0.15 U/ml of Oxyrase. The efficacy of these media to resuscitate C. jejuni cells in late exponential phase, as well as cells subjected to stress induced by cold, heat, starvation, or acid, was determined in aerobic or microaerobic atmospheres. The h of cells grown aerobically in NB2 containing both FBP and blood was similar to that obtained in the same medium incubated in a microaerobic environment (P > 0.05). However, the X was longer during aerobic growth when low numbers of cells (approximately 1 log CFU/ml) in late exponential phase were used as the initial inoculum. The best recovery of stressed C. jejuni was observed in NB2 supplemented with FBP and blood and incubated aerobically. Enrichment in media incorporating FBP and 5% laked horse blood is a simple, convenient, and time-saving method to replace microaerophilic incubation methods for the resuscitation of C. jejuni.

Genetic effects of acute spermatogonial X-irradiation of the laboratory rat.

The genetic effects of one generation of spermatogonial X-irradiation in rats, by a single dose of 600r in one experiment and by a fractionated dose of 450r in another, were measured in three generations of their descendants. Estimates of dominant lethal mutation rates--(2 to 3) X 10-4/gamete/r--from litter size differences between irradiated and nonirradiated stock were consistent with previous estimates from rats and mice. Similar consistency was found for estimates of sex-linked recessive mutation rates--(1 to 2) X 10-4 chromosome/r--from male proportions within strains; however, when measured in crossbreds the proportion of males was higher in the irradiated than in the nonirradiated lines. This inconsistency in results is in keeping with the contradictory results reported for recessive sex-linked lethal mutation rates in mice. The effects used to estimate recessive lethal mutation rates which were unusually high--(2 to 14) X 10-4/gamete/r--were not significant. Other factors that could have contributed to the observed effects are postulated.

Prediction of heterosis from DNA fingerprints in chickens.

To assess the value of DNA fingerprints for the prediction of heterosis in chickens, retrospective analyses of data from three crossbreeding experiments and DNA fingerprints (DEP) of parental strains were conducted using two minisatellite and one middle-repetitive DNA probes. DEP bands were assessed on pooled DNA samples of 10-15 individuals per parental genetic group. The number of DEP bands evaluated in the experiments ranged from 81 to 139. The probes varied in their predictive value, but predictability of heterosis generally increased with multiple probes. Highly significant correlations (0.68-0.87) between band sharing ratios (SH) and heterosis were found in 25 crosses of White Leghorns in the first egg production cycle for age at sexual maturity, egg production, and mature body weight: traits with heterosis of 10% or more of the means. Regressions on SH explained 78.4% of the variation in heterosis in age at sexual maturity, 60.2% in egg production and 46.4% in mature body weight. For "broiler" traits with heterosis of < 1%, none of the correlations, based on 13 crosses, were significant. It was concluded that multilocus probe DFP of pooled DNA samples show promise as predictors of heterosis.

Ontogeny of growth hormone receptor gene expression in tissue of growth-selected strains of broiler chickens.

The purpose of this study was to determine the relationship between genetic selection for growth traits and tissue expression of the chicken growth hormone receptor (cGHR) gene. Two different populations of broiler chickens were studied. One population consisted of strain (S) 80, selected for 14 generations for high 9-week body weight (BW), and its progenitor, S90 (a 1950's strain). The second population consisted of S21, selected for 10 generations for high 4-week BW and low abdominal fat, and its progenitor S20 (a 1970's strain). Tissue (liver, fat, breast and leg muscle) and blood samples were collected from six birds/strain at 2-week intervals between 1 and 11 weeks of age. An RNase protection assay was developed to measure mRNA levels of full-length cGHR (3.2 and 4.3 kb) transcripts and chicken glyceraldehyde 3-phosphate dehydrogenase (for normalization) in total RNA prepared from tissue. Analysis of the area-under-curve (AUC) was used for strain comparisons of certain developmental profiles (BW, plasma hormones and tissue cGHR mRNA). The BW AUC showed that the growth rates are different (P < 0.05) among the four strains (S21 > S20 > S80 > S90). Both slow-growing strains (S90 and S80) had a higher (P < 0.05) plasma GH AUC than the two fast-growing strains (S20 and S21). The plasma T3 AUC was highest (P < 0.05) in S90 due to maintenance of higher T3 levels after 3 weeks of age. At 11 weeks of age, hepatic and plasma GH-binding activities were positively related to growth rate (S21 > S20 > S80 > S90). However, the developmental increase in cGHR mRNA in liver and fat was similar among these different populations of growth-selected broiler chickens. Steady-state levels of cGHR mRNA increased in a developmental manner in the liver (5-fold at 9 weeks of age) and abdominal fat (4.5-fold at 11 weeks of age) of all strains. In contrast, there was no developmental increase or strain difference in cGHR mRNA levels in breast and leg muscle. There is a discrepancy between GH-binding activity in liver and plasma, which is different among strains, and steady-state levels of tissue cGHR mRNA which are similar among strains. These observations suggest that the cGHR is under translational or post-translational regulation which would determine the amount of cGHR protein available for GH binding.

Alpha-subunit G-protein antisense oligodeoxynucleotide effects on supraspinal (i.c.v.) alpha2-adrenoceptor antinociception in mice.

An in vivo antisense strategy was used to examine the involvement of G-protein subunits in supraspinal (intracerebroventricular; i.c.v.) alpha2-adrenoceptor-mediated antinociception. Mice that were injected with 33-mer antisense oligodeoxyribonucleotides (6 nmol) or vehicle were tested (tail-flick) with an agonist (clonidine, guanfacine or BH-T 920) administered i.c.v. 18 - 24 h later. Gi3alpha antisense treatment attenuated BH-T 920 and clonidine-induced antinociception. Gi2alpha antisense produced differential effects on the three agonists. Gi1alpha and G(s)alpha antisense treatment had no significant effect. Together with the previous demonstration that i.c.v. mu-opioid antinociception is mediated via Gi2alpha, the present results suggest that different receptors may mediate antinociception via different G-protein subunits and, hence, that specific subunits might offer novel targets for drug discovery.

Determination of male fertility in thirteen commercial lines of broiler parents.

Male reproductive capacity evaluated as percent fertility, hatchability, and duration of fertility was assessed for cockerels of 13 commercial broiler lines at 39 and 59 weeks of age using White Leghorn females. For each age the eggs were collected for 21 days following a second insemination of females with .05 ml of undiluted semen. With the exception of duration of fertility the differences among strains were not significant, suggesting that the differences among males within a strain were greater than those among strains for fertility and hatchability. The average percent fertility for a 4-day and 7-day postinsemination interval was 92.1% and 89.9% for Age I and 87.7% and 84.3% for the respective fertilities for Age II. The differences due to age were not significant. However, age had a significant effect on hatchability of settable eggs during 4 days (85.5% vs. 78.2%) and 7 days (83.2% vs. 74.9%) following artificial insemination (AI). The percentage of hatched chicks decreased progressively after day 7 following AI due to the greater incidence of infertile eggs and gradual increase in early embryonic mortality. The duration of fertility among broiler lines ranged between 9.7 to 13.9 days. The significant interaction between strain and age for duration of fertility reflected the changes in ranking among various broiler strains.

Maternal and sex-linked genetic effects in broiler parent stocks.

Sire and dam populations of chickens were synthesized from commercial broiler parent stocks at the Animal Research Centre, Ottawa. The production of two-way and four-way crosses during synthesis permitted measurement of maternal and sex-linked genetic effects on body weight and conformation traits. Sex-influenced effects were also measured. Reciprocal cross differences were minimal. Consequently, there was no evidence among stocks within parental type of maternal effect differences and only minimal evidence of sex-linked genetic effects. As expected, sex-influenced effects were large. Hence, it appears that breeders must work within strains or stocks to improve maternal and sex-linked genetic effects for body weight and conformation.

Genetic parameters of plasma very low density lipoproteins, abdominal fat lipase, and protein, fatness, and growth traits of broiler chickens.

Genetic parameters of physiological, growth, and fatness traits were investigated in one control and two selected dam strains of broiler chickens. Feed consumption and efficiency were measured between 28 and 42 days of age but were adjusted to estimate values of population average body weights at these ages. Birds were bled at 45 days of age for assay of plasma very low density lipoproteins (VLDL) and killed at 47 days of age for carcass and fat measurements. Abdominal fat was assayed for lipase activity expressed per milligram of protein (LIP/mgP) or per gram of fat (LIP/gF) and protein content of the enzyme preparation expressed as microgram protein/mL (P/mLEPrep). Absolute values of partial correlations corrected for sex and strain were low between production and physiological traits and between fatness and LIP/mgP but were moderate at .3 between fatness and plasma VLDL, LIP/gF, and P/mLEPrep. Heritabilities were moderate to high (greater than or equal to .32) for growth and fatness traits, moderate (.25) for plasma VLDL, and low (less than or equal to .16) for P/LEPrep, LIP/mgP, and LIP/gF. Genetic correlations involving plasma VLDL were as follows: .49 with body weight at 42 days, -.74 with feed consumption, .64 with feed efficiency, .24 with carcass weight at 47 days, 1.07 with abdominal fat weight, and .97 with abdominal fat percentage. Similarly, absolute values of genetic correlations involving P/mLEPrep tended to be as high or higher but genetic correlations involving LIP/mgP and LIP/gF tended to be lower than those involving plasma VLDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-constant versus weight-constant feed consumption and efficiency in broiler chickens.

Weekly body weights, feed consumption (FC), and feed efficiencies (FE = gain:feed) of 148 male and 125 female broilers were measured individually between 2 and 7 wk of age. Multiple regression analyses of these traits were performed to examine the influence of body weight, weight gain or feed consumption, age, and individual broiler differences. Four different measures of FC and FE from 4 to 6 wk of age were compared within sex: age-constant FC and FE; weight-constant FC and FE; age-constant-weight-corrected FC and FE; and weight-corrected FC and FE, which estimate weight-constant measures. Much of the variation (85 to 90%) among broilers in FC and FE was due to age and body weight differences. Partial regression coefficients indicated that increased body weight at commencement of testing was associated with increased FC and reduced weight gain and FE. Correlations between age-constant and weight-constant FC were zero. This indicates the two forms have little in common. Correlations of body weights and weight gain with FC were negative (-.5 to -.8) for weight-constant values but positive (.5 to .8) for age-constant values. Hence, correlations of the correct (weight-constant) measure of FC with body weights indicate that faster growth gives rise to lower broiler feed consumption. Age-constant and weight-constant FE values were positively correlated (.8 to .9); however, the latter values had larger correlations with body weights and weight gain. These results emphasize the need to correct age-constant FC and FE for body weight differences in order to evaluate differences in efficiency among broilers more accurately.

Genetic correlations among growth, feed, and carcass traits of broiler sire and dam populations.

Genetic correlations based on sire variance and covariance components were estimated for broiler traits. Data were collected from various selected and control strains of sire and dam populations during five generations of selection. Results of analyses of variance for each of the strains within generations and populations were pooled across strains and generations. Correlations between body and carcass weights were all above .8. Weight gain (WG) had similar correlations with these traits with the exception of body weight at 28 days (.57 in site and .69 in dam populations). Body and carcass weights and WG had high correlations with feed consumption (FC) (greater than .7); however, values for feed efficiency (FE) varied: -.58, -.23 for 28-day body weight; -.17, .16 for 42-day body weight; .25, .43 for WG; and .53 in the dam population for carcass weight. Correlations of body and carcass weights and WG with abdominal fat weight (AFW) and percentage (AFP) were generally small to moderate with values being about half as large for AFP as for AFW. Feed consumption and FE were negatively correlated (-.51, -.22) in both populations. In the dam population, FC was positively correlated with AFW and AFP (.42, .55) but FE was negatively correlated with these traits (-.41, -.70). Abdominal fat weight and AFP were highly correlated (.99, .97). Values tended to be similar not only for these populations but also for this and other studies. Simultaneous genetic improvement of growth rate, FE and carcass leanness is feasible in broilers. Selection for WG, FE, and AFP should be effective.

Genetic variation of broiler feed consumption and efficiency corrected for differences in test body weights.

Feed consumption and feed efficiency data obtained over nine generations from three selected strains of broilers were adjusted for differences in either initial or initial and final test BW (at 28 and 42 d, respectively). Genetic and environmental variables were estimated for each strain using an animal model with restricted maximum likelihood procedures to avoid bias due to reduced genetic variation caused by selection. Variance component and heritability estimates before and after adjustment of these traits for differences in test weights were evaluated. Adjustments of feed consumption data for either initial test BW or both initial and final test BW reduced additive genetic and environmental variation. Reductions were relatively greater for additive genetic than for environmental variance, thereby reducing the heritability of the adjusted trait. Adjustment of feed efficiency for initial test BW altered additive genetic variation little and reduced environmental variation slightly; however, correction for both test BW reduced variation of both components. Heritability of adjusted feed efficiency was 40% larger (.33 to .35 vs .21 to .28) than for uncorrected feed efficiency, but phenotypic variation of the adjusted feed efficiency was reduced 42% (5.82 to 6.13 vs 10.30 to 11.35). Heritabilities of feed consumption and efficiency were essentially the same (.34 and .36) after adjustment for both test weights. Changes in genetic and environmental variation and heritability due to adjustments were similar for the three strains.

Plasma very low density lipoproteins, abdominal fat lipase, and fatness during rearing in two strains of broiler chickens.

Experimental control Strains 30, representative of commercial broiler dam stocks in the late 1970's, and K, representative of commercial broiler stocks of 20 years earlier, were compared. Development of carcass fatness and related traits and physiological traits from 3 to 17 weeks of age were studied. About 12 chickens of mixed sex of each strain were bled and killed at 2-week intervals beginning at 3 weeks of age for measurement of traits. From 3 to 17 weeks of age, percentage abdominal fat of carcass, carcass fat (ether extract) and plasma very low density lipoproteins (VLDL) increased with age. Percentage carcass nitrogen, ash, and water, lipase activity of abdominal fat expressed per mg protein or per g of fat (LIP/g F), and protein concentration of the abdominal fat enzyme preparation (P/ml EPrep) decreased with age. Strain 30 had a higher percentage of abdominal fat and carcass fat, but less carcass nitrogen, ash, and water than Strain K, although there were interactions with sex and age. For physiological traits, Strain 30 had more LIP/g F and less P/ml EPrep than Strain K. Males had lower percentages of abdominal fat, carcass fat, and plasma VLDL, and higher percentages of carcass nitrogen, ash, and water than females. There were no significant differences between sexes for the other physiological traits. There were significant (P less than .01) partial correlations between plasma VLDL and percentage abdominal fat (.22), and between P/ml EPrep and percentages of abdominal fat (-.25), carcass fat (-.29), carcass nitrogen (.30), and carcass water (.30). These observations in conjunction with multiple regression analyses indicated that, in addition to plasma VLDL, protein concentration of adipose tissue expressed as P/ml EPrep might be a useful predictor of fatness in chickens.

Estimation of genetic parameters for ascites syndrome in broiler chickens.

Genetic parameters for the ascites syndrome (AS) were estimated for meat-type chickens. Data had been collected over 11 generations of selection for body weight and other traits within two distinct breeds (Cornish and White Rock). Linear methods (LM) were used to estimate genetic parameters and also to analyze a binary measure of survival. Survival analyses (SA) were also conducted to estimate the effects of various factors influencing the incidence of AS by evaluating the number of days that the birds survived. The animal model was used exclusively with linear methods. Heritabilities (h2) on the liability scale were 0.12 +/- 0.02 and 0.22 +/- 0.01 in the White Rock and Cornish breeds, respectively; however, the genetic correlation (r(g)) with body weight was not possible to estimate due to the low prevalence of the defect trait studied (1.5% in the Cornish and 1.1% in the White Rock). Because males are more prone to AS, the h2 using the male records only were 0.22 +/- 0.017 and 0.41 +/- 0.009, and the r(g) were 0.35 +/- 0.007 and 0.22 +/- 0.009 in the dam and sire populations, respectively. In conclusion, the heart defect investigated was heritable and had a positive genetic correlation with body weight.

The influence of complex carbohydrates on Salmonella typhimurium colonization, pH, and density of broiler ceca.

Salmonella typhimurium colonization, pH, and density of ceca were measured in 3-, 5-, and 6-wk-old broilers fed either a control ration or rations with added fructooligosaccharides (FOS) or lactose derivatives (LD). The purpose was to compare dietary crude FOS from Jerusalem artichokes with refined FOS and two LD for ability to reduce Salmonella colonization as determined by semi-quantitative procedures. Chicks were challenged commencing at 5 d, by exposure to chicks orally infected with S. typhimurium. With the exception of chicks fed crude FOS, the high prevalence of Salmonella infection at 3 wk declined as chicks aged. At 6 wk, broilers fed crude FOS had higher Salmonella counts than all other broiler groups, whereas broilers fed refined FOS had lower infections than control broilers. The decline of Salmonella infection of broilers fed either refined FOS or LD ceased after dietary additives were discontinued at 5 wk of age. At 6 wk, infection rates of the latter groups were at least as high as those of control broilers. Both FOS and LD reduced cecal pH and density. Broilers fed the control ration had higher pH at 5 and 6 wk and higher cecal densities at 3 and 5 wk than those of broilers fed rations containing 5% (wt/wt) carbohydrates. Treatment differences for cecal pH and density disappeared within 1 wk of withdrawal of carbohydrates from 5-wk-old broilers. No consistent effect of cecal pH and density on Salmonella infection was observed. Density was dependent on cecal volume, and at 6 wk of age, on broiler size.

Genetic variation in body size, composition, temperature, and feed intake in mature chickens.

Genetic variation for more than 40 traits was assessed in 26 stocks of mature chickens reared together and fed ad libitum from hatching to slaughter at 507 days of age. There was greater genetic variation among males than among females. The intraclass correlation, t, was high (greater than .75) for measures of size and weight and moderate (.20 to .60) for most other traits (P less than .05) including a measure of lean distribution (.37). Three main categories of stocks were studied, viz. outbred Leghorns, medium-sized stocks, and contemporary heavy meat chickens. Differences in lean distribution were not associated with category, but differences of 40 to 50 g/kg lean in the breast of some stocks may be caused by a single gene. Lean:bone ratios were similar in medium and heavy stocks but were greater (P less than .05) in heavy meat-types compared with outbred Leghorns. Bone density was higher (P less than .01) in females compared with males and in outbred Leghorns compared with heavier stocks (P less than .01). Heavy meat-type males were leaner (P less than .01) and had proportionately less fat in the abdominal cavity than outbred Leghorns. Carcass fatness was similar among stocks of females, but abdominal fat was lower in Leghorns selected for high egg production compared with unselected Leghorns (P less than .05) and heavy stocks (P less than .001). One resistant and two Marek's disease-susceptible stocks were replicated in a specific pathogen-free (SPF) environment. Spleen weight was larger (P less than .001) in the conventional environment. Females were relatively smaller (P less than .05) than males in the conventional environment. Body temperature (t = .25, P less than .05) and feed intake were assessed in males. Heavy meat birds had a lower (P less than .01) body temperature than outbred Leghorns and medium-sized stocks. Differences among stocks for feed intake (t = .77) were significant (P less than .05); however, they were greatly reduced when feed intake was expressed as g/kg liveweight (LW) (t = .49) or g/kg LW.75 (t = .25). Outbred Leghorns ate less in absolute terms but significantly more (P less than .01) as a proportion of LW or LW.75 than the medium and heavy lines.

Screening chickens for endogenous virus ev21 viral element by the polymerase chain reaction.

The molecular architecture of the sex-linked late-feathering region of the chicken genome is still poorly defined. Current evidence points to a strong association between the presence of the endogenous viral element ev21 and the late-feathering phenotype. However, analysis at the molecular level has demonstrated that this is not a simple case of insertional mutagenesis. Instead, the structure of the region of the chicken genome containing the feathering locus is complex and variable between and within lines of chickens. Significant clues to the molecular structure of this genomic region can be obtained by analyzing rare and revertant genotypes. However, searching for rare genotypes can only be carried out effectively using quick screen methodology. This paper describes a quick, polymerase chain reaction-based test for ev21 that facilities the search for rare genotypes.

Characterization of eight endogenous viral (ev) genes of meat chickens in semi-congenic lines.

Restriction fragment length polymorphism analysis was conducted for a set of eight different meat chicken-derived endogenous viral genes (ev genes) of the avian leukosis viral (ALV) family. Each viral element was first isolated into a separate single-element line by selective breeding. Genomic DNA from the founder male for each semi-congenic, single-element line was digested with each of four restriction enzymes, and the resulting Southern blots were each hybridized with up to four probes representing different portions of the ALV retroviral genome. Among the eight elements, there was one that represents the broiler equivalent of locus ev3 of White Leghorn chickens. A second broiler element showed a SacI-specific junction fragment similar to that of ev8. The remainder appeared to be different from any of the 21 ev genes previously described for White Leghorn chickens. Four of the eight elements examined were essentially complete, but the rest have sustained internal deletions.

Endogenous viral gene distribution in populations of meat-type chickens.

The present study was designed to document the complexity of endogenous viral (ev) genes and seek evidence for their association with production traits in selected and control strains of meat-type chickens. Three populations were studied, each consisting of a control strain and one to three strains selected for various production traits. The ev genes were revealed by digesting genomic DNA with restriction enzymes and detecting DNA fragments on Southern blots using radioactive probes from nucleotide sequences of the avian leukosis virus genome. A total of 31 polymorphic ev loci were identified in these populations from a SacI digest, with an average of 7.3 ev genes per bird. There were no significant differences in ev genes per bird between strains within populations or between selected and control strains overall. Thirty of 62 comparisons in the three populations indicated ev gene frequency differences (P less than .05). Within populations, 13 of 93 comparisons of ev gene frequencies between control and selected strains and 8 of 62 between three selected strains of a sire population showed such differences (P less than .05). Selection for body weight and feed efficiency had been observed to reduce gene frequencies of the slow-feathering gene, which usually contains the ev21 locus; however, these effects were not detected (.05 less than P less than .06) between strains of the dam population in the current study. Such differences suggested possible associations between ev genes and production traits in meat-type chickens.