Document Type : Research Paper
Authors
- Mohammad Moradi Shahr Babak 1
- Fatemeh Esmaeili Lima 2
- Hossain Moradi Shahrbabak 1
- Ali Jalil Sarghale 3
1 Department of Animal Science, Agricultural College, Tehran University
2 Department of Animal Science, Agricultural College, University of Tehran
3 , Department of Animal Science, Faculty of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
Abstract
Abstract
Objective: Methane is a potent greenhouse gas with a global warming potential of 27.2 times greater than the carbon dioxide. The fermentation process in the ruminant gut results in the strong production of methane, a potent greenhouse gas. The aim of this research was to identify genomic regions associated with methane emission in Holstein dairy cattle using a genome-wide association method and volatile fatty acid ratios of acetate to propionate and propionate to butyrate.
Research Materials and Methods: Hair and rumen fluid samples (via an esophageal tube) were collected from 150 selected animals based on the bidirectional milk yield trait breeding values (EBV) method from an industrial Holstein dairy cattle herd and using related standards for sampling. Methane emission was measured for each animal using these acids after measuring the concentration of rumen fluid volatile fatty acids. Hair cards samples of 150 animals were sent to Gene Seek company in country of America, and the DNA samples were genotyped using SNP panel of GGP-LD v4' (containing 30,108 SNPs). Quality control of genotyping results was done using Plink2.0 software. Total estimated SNPs were 29558 and after quality control 5723 of them were culled due quality control criteria.
GWAS Analysis: GWAS analysis was used for identifying genomic regions related to methane emission and least squared analysis of variance with proc GLM (Generalized linear model) in SAS (2002-v 9.1) software was used to identify significant fixed effect factors related to methane emission. A mixed linear model in Plink (19) software was used to analyze the relation between genotypes and methane emission traits.
Results: The effect of age and barnyard were significant for predicted methane emission trait based on the results of least square analysis variance (P<0/05). Five and two significant SNPs were determined for acetate to propionate and propionate to butyrate traits respectively. SNPs related to ratio of acetate to propionate trait were located on chromosomes 3, 28 and those related to ratio if propionate to butyrate trait were located on chromosomes 10, 11 respectively. Using annotation, a series of QTLs associated with methane emission, body weight, milk production traits, and remaining lactation period were identified around some of these SNPs.
Conclusion: The results of this research demonstrate the potential of genetic selection to reduce methane emissions per animal, such that the improvement resulting from genetic selection is very useful due to heritability, accumulation, and permanence.
Keywords: genetic selection, genome-wide analysis study, Holstein cattle, Methane emissions
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