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| Titel: |
Lifetime Performance in Dairy Cattle: Definition of Traits and Influence of Systematic Environmental Factors |
| Auteur: |
Strandberg, Erling |
| Verschenen in: |
Acta agriculturae Scandinavica. Section A, Animal science |
| Paginering: | Jaargang 42 (1992) nr. 2 pagina's 71-81 |
| Jaar: |
1992-05-01 |
| Inhoud: |
Lifetime economic performance traits were calculated from production, fertility and disease data on around 67 000 dairy cows with first calvings from 1982 to 1988. Almost 95% of the variation in lifetime income and cost was due to milk income or feed cost. The relative risk of culling (hazard) was maximum at approximately yearly intervals starting at 10 months of productive life. All lifetime economic traits were strongly affected by the length of productive life. The increase in, especially, lifetime net income per year, but also in lifetime income divided by cost with increased productive life, was highly curvilinear. This resulted from the spreading of the large heifer cost over an increasing productive life. When productive life exceeded two lactations the increase was smaller and fairly linear. A higher age at first calving was associated with lower lifetime economic performance, even though productive life increased slightly. The effect of month of first calving on lifetime economic traits was similar to its effect on milk yield. Considering various characteristics, lifetime income divided by cost seems to be the best trait for use as a single trait in the breeding goal. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 6 van 9 gevonden artikelen
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