26,375 research outputs found

    A Comparison of the Productivity of Suckler Cows of Different Breed Composition

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    End of project reportThe findings obtained in a comparison of 5 suckler dam breed types {Limousin x Friesian (LF), Limousin x (Limousin x Friesian) (LLF), Limousin (L), Charolais (C) and Simmental x (Limousin x Friesian) (SLF)} and their progeny through to slaughte

    Identification of Quantitative Trait Loci Affecting Female Reproductive Traits in a Multigeneration Meishan-White Composite Swine Population

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    A multigeneration crossbred Meishan- White composite resource population was used to identify quantitative trait loci (QTL) for age at first estrus (AP) and the components of litter size: ovulation rate (OR; number of ova released in an estrous period) and uterine capacity (UC). The population was established by reciprocally mating Meishan (ME) and White composite (WC) pigs. Resultant F1 females were mated to either ME or WC boars to produce backcross progeny (BC) of either ¾ WC ¼ ME or ¼ WC ¾ ME. To produce the next generation (F3) , ¾ WC ¼ ME animals were mated to ¼ WC ¾ ME animals yielding half-blood (½ WC ½ ME) progeny. A final generation (F4) was produced by inter se mating F3 animals. Measurements for AP and OR were recorded on 101 BC, 389 F3, and 110 F4 gilts, and UC data were from 101 BC and 110 F4 first parity litters. A genomic scan was conducted with markers (n = 157) spaced &#;20 cM apart. All parental, F1, BC, and F4 animals but only 84 F3 animals were genotyped and included in this study. The QTL analysis fitted a QTL at 1-cM intervals throughout the genome, and QTL effects were tested using approximate genome-wide significance levels. For OR, a significant (E[false positive] \u3c .05) QTL was detected on chromosome 8, suggestive (E[false positive] \u3c 1.0) QTL were detected on chromosomes 3 and 10, and two additional regions were detected that may possess a QTL (E[false positive] \u3c 2.0) on chromosomes 9 and 15. Two regions possessed suggestive evidence for QTL affecting AP on chromosomes 1 and 10, and one suggestive region on chromosome 8 was identified for UC. Further analyses of other populations of swine are necessary to determine the extent of allelic variation at the identified QTL

    Estimation of genetic parameters for height using spatial analysis in Tsuga heterophylla full-sibling family trials in British Columbia

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    Non-spatial and spatial analyses were carried out to study the effects on genetic parameters in ten-year height growth data across two series of 10 large second-generation full-sib progeny trials of western hemlock [Tsuga heterophylla (Raf.) Sarg.] in British Columbia. To account for different and complex patterns of environmental heterogeneity, spatial single trial analyses were conducted using an individual-tree mixed model with a two-dimensional smoothing surface with tensor product of B-spline bases. The spatial single trial analysis, in all cases, showed sizeable lower Deviance Information Criterion values relative to the non-spatial analysis. Also, fitting a surface displayed a consistent reduction in the posterior mean as well as a decrease in the standard deviations of error variance, no appreciable changes in the additive variance, an increase of individual narrow-sense heritability, and accuracy of breeding values. The tensor product of cubic basis functions of B-spline based on a mixed model framework does provide a useful new alternative to model different and complex patterns of spatial variability within sites in forest genetic trials. Individual narrow-sense heritabilities estimates from the spatial single trial analyses were low (average of 0.06), but typical of this species. Estimated dominance relative to additive variances were unstable across sites (from 0.00 to 1.59). The implications of these estimations will be discussed with respect to the western hemlock genetic improvement program in British Columbia.Fil: Cappa, Eduardo Pablo. British Columbia Ministry of Forests and Range; Canadá. University of British Columbia; Canadá. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Recursos Biológicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Yanchuk, A. D.. British Columbia Ministry of Forests and Range; CanadáFil: Cartwright, C. V.. British Columbia Ministry of Forests and Range; Canad

    Analysis of the meiotic segregation in intergeneric hybrids of tilapias

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    Tilapia species exhibit a large ecological diversity and an important propensity to interspecific hybridisation. This has been shown in the wild and used in aquaculture. However, despite its important evolutionary implications, few studies have focused on the analysis of hybrid genomes and their meiotic segregation. Intergeneric hybrids between Oreochromis niloticus and Sarotherodon melanotheron, two species highly differentiated genetically, ecologically, and behaviourally, were produced experimentally. The meiotic segregation of these hybrids was analysed in reciprocal second generation hybrid (F2) and backcross families and compared to the meiosis of both parental species, using a panel of 30 microsatellite markers. Hybrid meioses showed segregation in accordance to Mendelian expectations, independent from sex and the direction of crosses. In addition, we observed a conservation of linkage associations between markers, which suggests a relatively similar genome structure between the two parental species and the apparent lack of postzygotic incompatibility, despite their important divergence. These results provide genomics insights into the relative ease of hybridisation within cichlid species when prezygotic barriers are disrupted. Overall our results support the hypothesis that hybridisation may have played an important role in the evolution and diversification of cichlids

    Developing selection indexes & estimation of genetic parameters for traits of economic importance in dairy cattle under once-a-day milking : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Animal Science, Institute of Veterinary, Animal Biomedical Sciences, Massey University, Palmerston North, New Zealand

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    In New Zealand, about 5% of dairy herds are milked once-a-day (OAD). The cows are inseminated using sires from the twice-a-day milking system (TAD) evaluated on breeding worth (BW) or an OAD selection index. Testing for sire-by-milking frequency (MF) interaction (S×MF) could reveal if developing an OAD-specific selection scheme is justified. In this thesis production records were analysed from herds milked OAD and an equivalent TAD population provided by Livestock Improvement Corporation. Across MF, heritabilities (h2) and genetic correlations were similar for milk yields (h2: 0.21-0.36), although they tended to be greater in TAD. Genetic correlations were 0.35-0.40 between milk and fat yields, 0.85 between milk and protein yields and 0.54-0.60 between fat and protein yields. Observed rank correlation between OAD and TAD EBVs of the sires were moderate to high for milk yields, being greater in Jersey (J) (0.74-0.84) sires compared to Holstein-Friesian (F) and F×J crossbred (0.55-0.77) sires. Those values were greater than their critical values of the expected correlations (5th percentile), indicating that S×MF was not significant. Data from a university herd indicated that J cows were more efficient at production of milk solids (MS; fat + protein) per 100 kg of live weight than F or F×J cows milked OAD. In comparison, data from commercial herds milked either OAD or TAD indicated that F cows milked OAD had 19%-25% lower milk yields, whilst the reduction in yields from F×J and J cows was around 15%-19%. Breed effects (F-J) were lower on OAD compared to TAD systems, but heterosis effects were similar across MF (4.1%-7.6%). Under a progeny testing selection scheme for herds milked OAD, estimated genetic gains ranged from 3.3 to 3.7 kg/year for MS. Nevertheless, genetic gain resulting from the selection of bulls generated in TAD systems and dedicated to OAD herds would results in a similar increase compared with a separate scheme (only 11%-13% less of MS), indicating that there is little advantage in the implementation of a separate selection scheme. The main conclusion was that the S×MF interaction was not significant and farmers operating under OAD milking achieve similar genetic gain using sires from the TAD milking selection scheme but ranked on an OAD-selection index

    Breeding of resistant strawberry cultivars for organic fruit production – Diallel crossing strategies and resistance tests for Botrytis cinerea and Xanthomonas fragariae

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    Organic strawberry production suffers from high yield losses caused by numerous fungal and bacterial diseases. Two of the most important diseases are the grey mould disease caused by Botrytis cinerea Pers. (teleomorph Botryotinia fuckeliana), and the bacterial angular leaf spot disease caused by Xanthomonas fragariae (Kennedy & King). Beside cultivation methods and organic plant protection measures, the development of resistant cultivars seems to be the most promising strategy in order to improve the productivity in organic strawberry cultivation. Therefore, we established resistance tests to determine resistant and susceptible strawberry cultivars and breeding selections. In a first run, 40 different cultivars and selections were tested for their susceptibility towards B. cinerea by artificial inoculation of fruits and leaves and evaluation of the disease symptoms. Plants of 40 cultivars were tested for susceptibility to X. fragariae by artificial inoculation in the greenhouse. In a diallel crossing approach, 12 commonly cultivated strawberry cultivars have been crossed reciprocally and propagated in a field trial. Important characteristics of the progeny such as ripening time, yield, morphological traits and occurrence of diseases have been evaluated for a period of two consecutive years and lead to the determination of general (GCA) and specific (SCA) combining abilities. Together with the results of the resistance tests we identified a set of genotypes that show resistant characteristics towards B. cinerea and might be suitable for use in organic cultivation systems. Furthermore, they can be used for targeted breeding experiments in the future

    Virus Replication as a Phenotypic Version of Polynucleotide Evolution

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    In this paper we revisit and adapt to viral evolution an approach based on the theory of branching process advanced by Demetrius, Schuster and Sigmund ("Polynucleotide evolution and branching processes", Bull. Math. Biol. 46 (1985) 239-262), in their study of polynucleotide evolution. By taking into account beneficial effects we obtain a non-trivial multivariate generalization of their single-type branching process model. Perturbative techniques allows us to obtain analytical asymptotic expressions for the main global parameters of the model which lead to the following rigorous results: (i) a new criterion for "no sure extinction", (ii) a generalization and proof, for this particular class of models, of the lethal mutagenesis criterion proposed by Bull, Sanju\'an and Wilke ("Theory of lethal mutagenesis for viruses", J. Virology 18 (2007) 2930-2939), (iii) a new proposal for the notion of relaxation time with a quantitative prescription for its evaluation, (iv) the quantitative description of the evolution of the expected values in in four distinct "stages": extinction threshold, lethal mutagenesis, stationary "equilibrium" and transient. Finally, based on these quantitative results we are able to draw some qualitative conclusions.Comment: 23 pages, 1 figure, 2 tables. arXiv admin note: substantial text overlap with arXiv:1110.336