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Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 3/2/2006 Publication Date: 6/1/2006 Citation: Van Raden, P.M. 2006. Fertility trait economics and correlations with other traits. Interbull Annual Meeting Proceedings. Interbull Bull. 34:53-56. Interpretive Summary: National fertility evaluations are computed using greatly differing trait definitions and statistical models. Genetic evaluations for fertility would be easier to compare if units, bases, and directions were more similar between countries. Relationships (correlations) of fertility traits (heifer fertility, the interval from calving to first insemination, cow nonreturn rate, and calving interval) with yield traits (milk, fat, and protein), longevity, and somatic cell score (SCS) were compared for 11 countries. Correlations were consistent and small but always favorable with SCS, larger and always favorable with longevity, and nearly always unfavorable with yield and angularity or dairy form. Correlations of fertility and longevity are helpful but difficult to compare because fertility definitions differ. To examine a uniform definition of fertility, correlations between evaluations for U.S. daughter pregnancy rate (DPR) and foreign evaluations for longevity were compared. Countries that have low longevity evaluations correlations with DPR evaluations (such as Finland, France, and Israel) also have low correlations with U.S. longevity evaluations. Economic indexes for total merit place about 20% of selection emphasis on fertility and longevity traits in nearly all countries. Exact economic values for fertility traits may be difficult to determine because of part-whole relationships and positive correlations of fertility with longevity. Selection for high yield has resulted in moderate to large declines in fertility traits across time. Knowledge of relationships between fertility and other traits of economic importance will allow more accurate breeding decisions when selecting animals as parents of the next generation. Technical Abstract: Correlations of fertility traits (heifer fertility, interval from calving to first insemination, cow nonreturn rate, and calving interval) with yield traits (milk, fat, and protein), longevity, and somatic cell score (SCS) were compared for 11 countries. Correlations were consistent and small but always favorable with SCS, larger and always favorable with longevity, and nearly always unfavorable with yield and angularity. To examine a uniform definition of fertility, correlations between evaluations for U.S. daughter pregnancy rate (DPR) and foreign evaluations for longevity were compared. Longevity traits in Ireland, Sweden, Great Britain, Canada, and Belgium had correlations of .66, .64, .58, .54, and .52, respectively, with U.S. DPR. Lowest correlations between foreign longevity and U.S. DPR were .28, .27, and .22 for Finland, France, and Israel, respectively; longevity evaluations from those countries also have low correlations with U.S. longevity evaluations. Economic indexes for total merit place about 20% of selection emphasis on fertility and longevity traits in nearly all countries. Exact economic values for fertility traits may be difficult to determine because of part-whole relationships and positive correlations of fertility with longevity. Selection for high yield has resulted in moderate to large declines in fertility traits across time. Knowledge of relationships between fertility and other traits of economic importance will allow more accurate breeding decisions when selecting animals as parents of the next generation. |
