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  • Biochemistry and Biotechnology  (1)
  • Disease  (1)
  • Egglayers  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 65 (1983), S. 317-322 
    ISSN: 1432-2242
    Keywords: Disease ; Lymphoid leukosis ; Chickens ; Variance ; Heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of disease, particularly when congenitally transmitted, on variance components and heritability were studied. Observations on lymphoid leukosis, a congenitally transmitted, viral disease of chickens, were used as the basis of the considerations but the results are deemed applicable to other situations where a population is similarly affected by a disease or another factor resulting in alteration of performance. The numbers of pullets tested for lymphoid leukosis virus (LLV) shedding into eggs were 1785 in 1976 and 1699 in 1977. A comparison of the distribution of LLV shedders (approximately 8% of the birds tested) among sire and dam families with its binomial expectations supported earlier reports that only dams play a role in congenital transmission of LLV. The effects of LLV infection on variance components and heritability were assessed in the 1976 data by comparing estimates from both LLV-shedders and nonshedders (population A) with estimates from nonshedders only (population B). Sire variances for age at first egg, number of eggs per hen housed, egg production rate, and egg weight were 3 to 18% greater in population A compared to population B. The corresponding differences in dam variances were generally larger (5 to 48%) while relative differences in individual variances were small (1 to 10%). Total phenotypic variances for the traits were 2 to 13% larger in population A than B. Corresponding changes in percent sire heritability ranged from −1 to 6%, and in dam heritability from −2 to 12%. The significance of these effects was not established with certainty due to standard errors of the estimates (9 to 13%). The study pointed out the need to consider possible effects of agents such as LLV on designing breeding plans, experiments and in data analyses.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Egglayers ; Marek's disease resistance ; Egg production ; Endogeneous viral genes ; Group specific antigen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Endogenous viral (ev) genes related to the avian leukosis virus were classified in two differentially selected strains of Leghorns in order to investigate whether such genes affect production traits. Strain K had been selected for resistance to Marek's disease (MD) and for high egg production and egg weight, whereas strain S had been selected only for MD susceptibility. Except that founders of strain K included a few commercial birds, both strains were derived from a common genetic base. DNA restriction fragment length analyses of 110 strain K and 94 strain S birds revealed the presence of 8 different ev-genes, 6 of which were identical to previously identified loci. This result was confirmed by assays for group specific antigen (gs-antigen), the product of the gag region of the ev-genes. The levels of gs-antigen in the birds closely followed what had been predicted from data obtained from previously described ev-genes. Both strains had a similar average number of ev-genes per bird (3.5 and 3.2 for strains S and K, respectively). However, strain K carried only five different ev-genes while strain S carried seven. Four of these loci were present in both strains. Among the ev-genes absent or occurring less frequently in strain K were those that code either for infectious endogenous virus (ev-10 and possibly ev-19) or for the internal viral gag-proteins (ev-3). Only those ev-genes which are transcriptionally silent or which code for the viral envelope gene were present in increased frequencies in strain K. The results indicate that selection for egg traits and/or Marek's disease resistance reduces the frequency of ev-genes which produce endogenous virus or the viral gag-proteins.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1087-1094 
    ISSN: 0006-3592
    Keywords: fermentation ; optimization ; enzymatic reactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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