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Genetic resistance to gastro-intestinal nematodes in goats
The present study aimed at exploring the possibility of incorporating Gastro Intestinal Nematode (GIN) resistance as a criterion for selection in goat breeding. Here Faecal Egg Count (FEC) was taken as an indicator of host resistance. Heritability estimate for FEC and correlation of FEC with Packed...
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| Format: | Ph.D Thesis |
| Language: | Undetermined |
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Mannuthy
Department of Animal Breeding, Genetics and Biostatistics, College of Veterinary and Animal Sciences
2010
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| 100 | |a Aparna Sankar | ||
| 245 | |a Genetic resistance to gastro-intestinal nematodes in goats | ||
| 260 | |a Mannuthy |b Department of Animal Breeding, Genetics and Biostatistics, College of Veterinary and Animal Sciences |c 2010 | ||
| 502 | |b MVSc | ||
| 520 | 3 | |a The present study aimed at exploring the possibility of incorporating Gastro Intestinal Nematode (GIN) resistance as a criterion for selection in goat breeding. Here Faecal Egg Count (FEC) was taken as an indicator of host resistance. Heritability estimate for FEC and correlation of FEC with Packed Cell Volume (PCV) were calculated. While assessing resistance at phenotypic level using FEC as indicator, the possibility of using PCV as an alternative to FEC was also considered. Using IFNγ intron 1 as the locus of study, an attempt was made to identify a genetic marker for GIN resistance in goats. University Livestock Farm, Mannuthy and two field centers under All India Co-ordinated Research Project (AICRP), namely - Tellichery and Badagara, formed the venue for study. In the present investigation, data from three genetic groups - Malabari, Attappady Black and Malabari crossbreds were used. Representative population in the study comprised of 150 goats. The nematode eggs encountered during the study belonged to Strongyle and Strongyloides sp. Mean FEC was 764.39 eggs per gram of the faeces (epg) with values ranging from 0.00 to 16700 epg. The value of PCV estimated ranged between 19 and 48 per cent. Effect of non-genetic factors on FEC was analyzed after logarithmically transforming the FEC. University Goat & Sheep farm, Mannuthy recorded the least FEC. This might be due to the improved immune status of the animal through careful selection along with scientific managemental practices followed in the University farm. The non-significant influence of sex, birth weight and type of birth might be due to uniform managemental conditions given to kids irrespective of sex, birth weight or type of birth, which do not favour GIN prevalence. The reason for failure of season in influencing FEC could be due to the fact that, not much demarcation was observed between seasons during the study. The genetic similarity between Malabari purebreds and Malabari crossbreds, lesser sample size for Attapady Black breed and similar management given to the breeds led to non significant effect of breed on FEC. A negative phenotypic correlation estimate of -0.1791 was observed between LFEC and PCV. The heritability estimated for FEC was 0.39 ± 0.3630 as per paternal half sib correlation method and it was moderate. This moderate heritability estimate for FEC shows that there is significant genetic variation within the population for the trait, which makes selection for nematode resistance possible. Genomic DNA was isolated from blood samples of 150 goats maintained in the farm and two field centers of Kerala using phenol chloroform extraction procedure. Through PCR, a 202bp product of IFN γ intron 1 was amplified. On restriction digestion of the amplified product, the restriction-endonuclease, BspHI cut PCR product into two fragments of 180 bp and 22 bp sizes. Monomorphic pattern was observed on the particular RFLP analysis. The 202bp PCR product was sequenced by the dideoxynucleotide sequencing method with M13 universal reverse primer using an automated DNA sequencer. The sequence included a tetra nucleotide repeat, (GT4)5 and an Adenine present at a position, 49 bp downstream of this microsatellite. The sequence had 100 per cent homology with sheep, 89 per cent with European cattle, 73 per cent with pig and 70 per cent with human. On submission of the nucleotide sequence data of goat-IFNγ intron1 to the GenBank DNA database, an Accession Number: HM047072 was obtained. As per available literature, this work seems to be the first of its kind in establishing the DNA sequence data of intron1 of IFN γ gene in goats. It is recommended that study of this gene in a larger population with greater genetic base might bring out the polymorphism and help in marker assisted selection for GIN resistance in goats. Overall, the study aided in establishing nucleotide sequence of IFN γ intron1 in goats and showed that there is immense scope for selection of animals for nematode resistance. This study emphasizes the fact that along with other production traits, host genetic resistance should also be included as a criterion for selecting goats, producing genetically superior stock. | |
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