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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 68 (1984), S. 385-389 
    ISSN: 1432-2242
    Keywords: Coccidiosis ; Eimeria tenella ; Eimeria acervulina ; Heritability ; Genetic resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic variability of 18 sire families of the Athens-Canadian randombred population infected with coccidiosis was assessed by examining the response variables of weight gain, packed red blood cell volume, mortality and coccidial lesions. A significant gain and PCV depression and high lesion scores for Eimeria tenella and E. acervulina were produced in the infected group compared to the noninfected group. Significant variation among the sire families was observed for all of the response variables except E. acervulina lesions and a significant sex x sire interaction was observed for weight gain. The heritability (h2) estimates for the response variables revealed that resistance to coccidiosis in chickens is moderately heritable. The h2 estimates for gain and PCV increased with the coccidial infections indicating that maximum progress in selecting for resistance should be made when the population was exposed to coccidial infection. Gain was positively correlated to the other measures of resistance and thus selecting for coccidial resistance should not reduce growth rates. PCV was similarly correlated but had higher positive correlation with E. tenella lesion. Percent mortality which is the selection parameter in most coccidial selection programs was correlated with resistance to coccidiosis. The phenotypic and genotypic correlations demonstrated that chickens susceptible to E. tenella were also susceptible to E. acervulina. Total lesion scores were moderately to highly correlated with the other variables and would be a suitable variable to use in coccidiosis experimentation including a genetic selection program for resistance. This study shows that progress could be made in selecting for resistance to coccidiosis in chickens using one or a combination of these response variables.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 63 (1982), S. 207-212 
    ISSN: 1432-2242
    Keywords: Heritability ; Genetic correlations ; Albumin ; Protein ; PCV ; Cholesterol ; Body weight ; Broiler ; Chicken ; Aflatoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A pedigreed, commercial broiler population of 31 sire families was administered dietary aflatoxin at levels of either 0.0 or 5.0 μg of aflatoxin per g of diet from 7 to 21 days of age and their response assessed by various physiological parameters. Body weight, gain, packed red blood cell volume (PCV). plasma albumin, plasma protein and cholesterol responses were significantly reduced from control values by the 5.0 μg/g aflatoxin diet. Males had greater body weights and gains in both dietary regimes than females. Females had significantly higher PCV, protein, albumin and cholesterol values in the 5.0 μg/g aflatoxin group than their male counterparts. These differences resulted in significant sex × aflatoxin level interactions for these parameters. Coefficients of variation were increased for all parameters measured in the 5.0 μg/g aflatoxin treatment compared to values for the control group. This increase was greatest for plasma protein, albumin, and cholesterol responses. Heritabilities were calculated for all responses within both treatment groups and were found to be increased in all cases by the 5.0 μg/g aflatoxin diet. Highly significant phenotypic correlations were determined between body weight and gain and between plasma albumin and total plasma protein in both treatment groups. High phenotypic correlations among PCV, plasma cholesterol, plasma protein, and plasma albumin were noted in the 5.0 μg/g aflatoxin group. Significant genetic correlations were determined between body weight and gain and between plasma albumin and plasma protein in the control group. Body weight and gain and plasma protein, albumin, cholesterol and PCV were genetically correlated in the 5.0 μg/g aflatoxin group. Genetic correlations calculated across environments for the same traits were high for PCV, body weight and gain and much lower for plasma albumin, plasma protein, and plasma cholesterol. The results of this study demonstrate that genetic variability for resistance to aflatoxin exists in commercial broiler populations. Strong genetic and phenotypic relationships, and high heritabilities associated with plasma albumin and protein suggest their applicability as selection criteria for aflatoxin resistance. Genetic correlation for these traits across dietary environments indicate that responses for aflatoxin resistance should be measured during aflatoxin challenge and suggest that selection for growth and selection for aflatoxin resistance are not antagonistic.
    Type of Medium: Electronic Resource
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