Genetic analysis of groups of mid-infrared predicted fatty acids in milk.
The objective of this study was to investigate genetic variability of mid-infrared predicted fatty acid groups in Canadian Holstein cattle. Genetic parameters were estimated for 5 groups of fatty acids: short-chain (4 to 10 carbons), medium-chain (11 to 16 carbons), long-chain (17 to 22 carbons), saturated, and unsaturated fatty acids. The data set included 49,127 test-day records from 10,029 first-lactation Holstein cows in 810 herds. The random regression animal test-day model included days in milk, herd-test date, and age-season of calving (polynomial regression) as fixed effects, herd-year of calving, animal additive genetic effect, and permanent environment effects as random polynomial regressions, and random residual effect. Legendre polynomials of the third degree were selected for the fixed regression for age-season of calving effect and Legendre polynomials of the fourth degree were selected for the random regression for animal additive genetic, permanent environment, and herd-year effect. The average daily heritability over the lactation for the medium-chain fatty acid group (0.32) was higher than for the short-chain (0.24) and long-chain (0.23) fatty acid groups. The average daily heritability for the saturated fatty acid group (0.33) was greater than for the unsaturated fatty acid group (0.21). Estimated average daily genetic correlations were positive among all fatty acid groups and ranged from moderate to high (0.63-0.96). The genetic correlations illustrated similarities and differences in their origin and the makeup of the groupings based on chain length and saturation. These results provide evidence for the existence of genetic variation in mid-infrared predicted fatty acid groups, and the possibility of improving milk fatty acid profile through genetic selection in Canadian dairy cattle.
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Narayana
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Schenkel
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada. Electronic address: fleminga@uoguelph.ca.
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Fleming
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Koeck
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Malchiodi
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada; Canadian Dairy Network, Guelph, ON, N1K 1E5, Canada.
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Jamrozik
Canadian Dairy Network, Guelph, ON, N1K 1E5, Canada.
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Johnston
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada; Semex Alliance, Guelph, ON, N1H 6J2, Canada.
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Sargolzaei
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada; Canadian Dairy Network, Guelph, ON, N1K 1E5, Canada.
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Miglior
D000367:Age Factors; D000818:Animals; D002170:Canada; D002417:Cattle; D005227:Fatty Acids / Q000737:chemistry / Q000235:genetics*; D005231:Fatty Acids, Unsaturated / Q000235:genetics; D005260:Female; D059647:Gene-Environment Interaction; D014644:Genetic Variation; D007774:Lactation / Q000235:genetics; D008892:Milk / Q000737:chemistry*; D012044:Regression Analysis
D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated
heritability; mid-infrared; milk fatty acid; random regression model