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ARS Home » Research » Publications at this Location » Publication #173105
Title: GENETIC ALTERNATIVES FOR DAIRY PRODUCERS WHO PRACTISE GRAZING

Author
item Norman, H
item Wright, Janice
item Powell, Rex

Submitted to: Grassland International Congress
Publication Type: Proceedings
Publication Acceptance Date: 3/8/2005
Publication Date: 7/3/2005
Citation: Norman, H.D., Wright, J.R., Powell, R.L. 2005. Genetic alternatives for dairy producers who practise grazing. In: Proceedings of Satellite Workshop of the XXth International Grassland Congress, July 3-6, 2005, Cork, Ireland. p. 176.

Interpretive Summary: The decline in cow fertility has had a negative impact on all dairy producers, especially those that practice seasonal calving with pasture-based dairying. One alternative that is being tried in the United States (US) by a few graziers who are interested in improved fertility is to use bulls from New Zealand (NZ) because NZ producers have practiced seasonal calving for some time. However, the interaction between genotype and environment is a concern; genetic correlations that have been derived by the International Bull Evaluation Service (Uppsala, Sweden) between bull rankings from different countries often were lower for NZ than for other countries. This study compared the performance of daughters of Holstein artificial-insemination bulls from NZ with daughters of other Holstein artificial-insemination bulls (predominantly from the US) that were in the same US herd and calved at the same time. Milk, fat, protein, somatic cell score (SCS, an indicator of mastitis), and days open were examined for the first three lactations of Holstein cows. Strain differences existed for several performance traits. Daughters of US bulls were more productive than daughters of NZ bulls for milk and protein. First-lactation daughters of US bulls also had lower SCS, but daughters of NZ bulls had fewer days open. Comparisons also are planned for productive life (longevity) and calving ease. Producers should consider the economic values of all the performance traits, and those should be combined into an index appropriate for expected economic conditions. Producers who practice grazing and seasonal calving should place more weight on fertility traits than is recommended for the general dairy cattle industry because of their higher economic value in a grazing environment.

Technical Abstract: The decline in cow fertility has had a negative impact on all dairy producers, especially those that practice seasonal calving with pasture-based dairying. One alternative that is being tried in the United States (US) by a few graziers who are interested in improved fertility is to use bulls from New Zealand (NZ) because NZ producers have practiced seasonal calving for some time. However, genotype-environmental interaction is a concern; genetic correlations that have been derived by the International Bull Evaluation Service (Uppsala, Sweden) between bull rankings from different countries often were lower for NZ than for other countries. The objective of this study was to compare the performance of daughters of Holstein artificial-insemination bulls from NZ with daughters of other Holstein artificial-insemination bulls (predominantly from the US) that were in the same US herd and calved at the same time. Milk, fat, protein, somatic cell score (SCS, an indicator of mastitis), and days open were examined for the first three parities of Holstein cows. Traits were standardized for environmental effects in the same manner as in the current USDA genetic evaluation. Cows were required to have calved after December 1999 and before August 2004 and to have had the opportunity to express the performance trait; i.e., the herd remained on production testing. Data for first-parity yield traits and SCS were from 489 daughters of NZ bulls and 5419 daughters of other bulls in 177 herds. Second- and third-parity yield traits represented 345 and 174 NZ daughters and 5057 and 2840 other daughters in 153 and 82 herds, respectively. Data for first-parity days open were from 450 daughters of NZ bulls and 5036 daughters of other bulls in 138 herds. Strain differences existed for several performance traits. Mean first-parity milk and protein yields were lower by 501 and 5 kg, respectively, for daughters of the NZ bulls than for daughters of other bulls. Mean second-parity milk and protein yields were lower by 467 and 5 kg, and third-parity means were lower by 448 and 4 kg. Fat yields were higher by 2 kg. First-parity daughters of NZ bulls had higher mean SCS than did daughters of other bulls (3.2 versus 3.0). Daughters of NZ bulls had 7 fewer days open during first lactation than did daughters of other bulls but had 2 and 3 greater days open during second and third lactations. Comparisons also are planned for productive life (longevity) and calving ease. Producers should consider the economic values of all the performance traits, and those should be combined into an index appropriate for expected economic conditions. Producers who practice grazing and seasonal calving should place more weight on fertility traits than is recommended for the general dairy cattle industry because of their higher economic value in a grazing environment.