Changes in genetic trends in US dairy cattle since the implementation of genomic selection
ABSTRACT: Genomic selection increases accuracy and decreases generation interval, accelerating genetic changes in populations. Assumptions of genetic improvement must be addressed to quantify the magnitude and direction of change. Genetic trends of US dairy cattle breeds were examined to determine t...
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| Format: | Article |
| Language: | English |
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Elsevier
2023-02-01
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| Series: | Journal of Dairy Science |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S0022030222007093 |
| _version_ | 1811159577393102848 |
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| author | F.L. Guinan G.R. Wiggans H.D. Norman J.W. Dürr J.B. Cole C.P. Van Tassell I. Misztal D. Lourenco |
| author_facet | F.L. Guinan G.R. Wiggans H.D. Norman J.W. Dürr J.B. Cole C.P. Van Tassell I. Misztal D. Lourenco |
| author_sort | F.L. Guinan |
| collection | DOAJ |
| description | ABSTRACT: Genomic selection increases accuracy and decreases generation interval, accelerating genetic changes in populations. Assumptions of genetic improvement must be addressed to quantify the magnitude and direction of change. Genetic trends of US dairy cattle breeds were examined to determine the genetic gain since the implementation of genomic evaluations in 2009. Inbreeding levels and generation intervals were also investigated. Breeds included Ayrshire, Brown Swiss, Guernsey, Holstein (HO), and Jersey (JE), which were characterized by the evaluation breed the animal received. Mean genomic predicted breeding values (PBV¯) were analyzed per year to calculate genetic trends for bulls and cows. The data set contained 154,008 bulls and 33,022,242 cows born since 1975. Breakpoints were estimated using linear regression, and nonlinear regression was used to fit the piecewise model for the small sample number in some years. Generation intervals and inbreeding levels were also investigated since 1975. Milk, fat, and protein yields, somatic cell score, productive life, daughter pregnancy rate, and livability PBV¯ were documented. In 2017, 100% of bulls in this data set were genotyped. The percentage of genotyped cows has increased 23 percentage points since 2010. Overall, production traits have increased steadily over time, as expected. The HO and JE breeds have benefited most from genomics, with up to 192% increase in genetic gain since 2009. Due to the low number of observations, trends for Ayrshire, Brown Swiss, and Guernsey are difficult to infer from. Trends in fertility are most substantial; particularly, most breeds are trending downwards and daughter pregnancy rate for JE has been decreasing steadily since 1975 for bulls and cows. Levels of genomic inbreeding are increasing in HO bulls and cows. In 2017, genomic inbreeding levels were 12.7% for bulls and 7.9% for cows. A suggestion to control this is to include the genomic inbreeding coefficient with a negative weight to the selection index of bulls with high future genomic inbreeding levels. For sires of bulls, the current generation intervals are 2.2 yr in HO, 3.2 in JE, 4.4 in Brown Swiss, 5.1 in Ayrshire, and 4.3 in Guernsey. The number of colored breed bulls in the United States is currently at an extremely low level, and this number will only increase with a market incentive or additional breed association involvement. Increased education and extension could be beneficial to increase knowledge about inbreeding levels, use of genomics and genetic improvement, and genetic diversity in the genomic selection era. |
| first_indexed | 2024-04-10T05:44:40Z |
| format | Article |
| id | doaj.art-c78ae6ca315943509d97593371eab61a |
| institution | Directory Open Access Journal |
| issn | 0022-0302 |
| language | English |
| last_indexed | 2024-04-10T05:44:40Z |
| publishDate | 2023-02-01 |
| publisher | Elsevier |
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| series | Journal of Dairy Science |
| spelling | doaj.art-c78ae6ca315943509d97593371eab61a2023-03-06T04:44:49ZengElsevierJournal of Dairy Science0022-03022023-02-01106211101129Changes in genetic trends in US dairy cattle since the implementation of genomic selectionF.L. Guinan0G.R. Wiggans1H.D. Norman2J.W. Dürr3J.B. Cole4C.P. Van Tassell5I. Misztal6D. Lourenco7Department of Animal and Dairy Science, University of Georgia, Athens 30602; Corresponding authorCouncil on Dairy Cattle Breeding, 4201 Northview Drive, Suite 302, Bowie, MD 20716Council on Dairy Cattle Breeding, 4201 Northview Drive, Suite 302, Bowie, MD 20716Council on Dairy Cattle Breeding, 4201 Northview Drive, Suite 302, Bowie, MD 20716URUS Group LP, 2418 Crossroads Drive, Suite 3600, Madison, WI 53718Animal Genomics and Improvement Laboratory, Agricultural Research Service, United States Department of Agriculture (USDA), Beltsville, MD 20705Department of Animal and Dairy Science, University of Georgia, Athens 30602Department of Animal and Dairy Science, University of Georgia, Athens 30602ABSTRACT: Genomic selection increases accuracy and decreases generation interval, accelerating genetic changes in populations. Assumptions of genetic improvement must be addressed to quantify the magnitude and direction of change. Genetic trends of US dairy cattle breeds were examined to determine the genetic gain since the implementation of genomic evaluations in 2009. Inbreeding levels and generation intervals were also investigated. Breeds included Ayrshire, Brown Swiss, Guernsey, Holstein (HO), and Jersey (JE), which were characterized by the evaluation breed the animal received. Mean genomic predicted breeding values (PBV¯) were analyzed per year to calculate genetic trends for bulls and cows. The data set contained 154,008 bulls and 33,022,242 cows born since 1975. Breakpoints were estimated using linear regression, and nonlinear regression was used to fit the piecewise model for the small sample number in some years. Generation intervals and inbreeding levels were also investigated since 1975. Milk, fat, and protein yields, somatic cell score, productive life, daughter pregnancy rate, and livability PBV¯ were documented. In 2017, 100% of bulls in this data set were genotyped. The percentage of genotyped cows has increased 23 percentage points since 2010. Overall, production traits have increased steadily over time, as expected. The HO and JE breeds have benefited most from genomics, with up to 192% increase in genetic gain since 2009. Due to the low number of observations, trends for Ayrshire, Brown Swiss, and Guernsey are difficult to infer from. Trends in fertility are most substantial; particularly, most breeds are trending downwards and daughter pregnancy rate for JE has been decreasing steadily since 1975 for bulls and cows. Levels of genomic inbreeding are increasing in HO bulls and cows. In 2017, genomic inbreeding levels were 12.7% for bulls and 7.9% for cows. A suggestion to control this is to include the genomic inbreeding coefficient with a negative weight to the selection index of bulls with high future genomic inbreeding levels. For sires of bulls, the current generation intervals are 2.2 yr in HO, 3.2 in JE, 4.4 in Brown Swiss, 5.1 in Ayrshire, and 4.3 in Guernsey. The number of colored breed bulls in the United States is currently at an extremely low level, and this number will only increase with a market incentive or additional breed association involvement. Increased education and extension could be beneficial to increase knowledge about inbreeding levels, use of genomics and genetic improvement, and genetic diversity in the genomic selection era.http://www.sciencedirect.com/science/article/pii/S0022030222007093genomic informationgenetic gaincolored breedsgeneration intervalinbreeding |
| spellingShingle | F.L. Guinan G.R. Wiggans H.D. Norman J.W. Dürr J.B. Cole C.P. Van Tassell I. Misztal D. Lourenco Changes in genetic trends in US dairy cattle since the implementation of genomic selection Journal of Dairy Science genomic information genetic gain colored breeds generation interval inbreeding |
| title | Changes in genetic trends in US dairy cattle since the implementation of genomic selection |
| title_full | Changes in genetic trends in US dairy cattle since the implementation of genomic selection |
| title_fullStr | Changes in genetic trends in US dairy cattle since the implementation of genomic selection |
| title_full_unstemmed | Changes in genetic trends in US dairy cattle since the implementation of genomic selection |
| title_short | Changes in genetic trends in US dairy cattle since the implementation of genomic selection |
| title_sort | changes in genetic trends in us dairy cattle since the implementation of genomic selection |
| topic | genomic information genetic gain colored breeds generation interval inbreeding |
| url | http://www.sciencedirect.com/science/article/pii/S0022030222007093 |
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