Selection of Bulls for Progeny Testing Using Pedigree Indices and Characteristics of Potential Bull-Dams' Herds

Mao, I.L.; Dong, Min; Meadows, C.E.

doi:10.3168/jds.s0022-0302(91)78454-3

Cited by 4 publications

(4 citation statements)

References 7 publications

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“…The bias in the PI of bulls for milk yield has been well documented by different studies and it has usually been lower for animal models (Ferris and Wiggans, 1991;Mao, Dong and Meadows, 1991) than for other evaluation methods (Wilhelm and Mao, 1989;Ferris et al, 1990;Pedersen, 1991). This equals about one-third of the genetic standard deviation for the trait.…”

Section: Bias In Pedigree Indicesmentioning

confidence: 96%

Repeatability and bias of estimated breeding values for dairy bulls and bull dams calculated from animal model evaluations

Uimari¹,

Mäntysaari²

1993

Anim. Sci.

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Link to this article: http://journals.cambridge.org/abstract_S0003356100006772How to cite this article: P. Uimari and E. A. Mäntysaari (1993). Repeatability and bias of estimated breeding values for dairy bulls and bull dams calculated from animal model evaluations. AbstractAn animal model and an approximative method for calculating repeatabilities of estimated breeding values are used in Finnish dairy cow evaluation. Changes in estimated breeding values over time as daughters accumulate were studied. Special emphasis was given to the accuracy and potential bias in the pedigree indices of young sires. The data set used was the same as in the national evaluation and the traits investigated were protein yield and somatic cell count. The average repeatability in evaluation of bulls without daughters was 0-37. The empirical repeatability defined as a squared correlation between the pedigree index and the final sire proof was only 0-15. The reduction in the repeatability was attributed to the selection on pedigree index. The upward bias observed in pedigree indices was 5 kg (approx. 0-3 of genetic standard deviation). The bias was caused by the overestimation of bull dams' breeding value. Also the proofs of bull sires increased after the second crop of daughters. The correlation between the evaluations of the same sire calculated from two separate equal size daughter groups was 0-91 when the bull had 10 to 50 daughters and 0-87 with over 100 daughters. This illustrates how the relative weight of the pedigree decreases while more progeny information is accumulated in the evaluation.

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Section: Bias In Pedigree Indicesmentioning

confidence: 96%

Repeatability and bias of estimated breeding values for dairy bulls and bull dams calculated from animal model evaluations

Uimari¹,

Mäntysaari²

1993

Anim. Sci.

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“…Butcher and Legates (1975) found lower correlations for milk yield. Mao et al (1991) found higher correlations between PTA of the bull and PTA of its dam, probably because they did not use the conversion equations. Correlations between bull EBV for protein, FS, and ICO and their dam EBV were not significantly better than with MGS and MGGS.…”

Section: Spanish Pt Programmentioning

confidence: 94%

“…Preferential treatment of bull dams may have contributed to this result as well. Preferential treatment has been studied widely in other papers (Mao et al, 1991;Weigel et al, 1994) and it was avoided (insofar as possible) in this PT program. The PT bull EBV for protein, FS, and ICO showed similar correlations with MGS and MGGS EBV, and showed slightly lower correlations with dam EBV.…”

Section: Spanish Pt Programmentioning

confidence: 99%

Genetic Analysis of an Artificial Insemination Progeny Test Program

González-Recio

Ugarte²,

Alenda

2005

Journal of Dairy Science

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The success of the progeny test (PT) program from one Spanish artificial insemination (AI) organization was evaluated. The annual genetic trend for the organization was compared with PT programs from other countries. The relationships among parents' estimated breeding values (EBV) and PT results for sons were also studied. Estimated breeding values for type and production traits were obtained from international genetic evaluations from February 2004. The annual genetic gain of the Spanish PT program was similar to that of other international programs. The Spanish AI organization graduated 13% of its sampled bulls, and 52% of primiparous cows were daughters of Spanish bulls (32% from proven bulls and 20% from sampling bulls). Correlations between EBV for PT bulls and their pedigree indices (0.52 to 0.70) were slightly lower than correlations between EBV for PT bulls and their parent averages (0.63 to 0.73). Both young and mature cows contributed to genetic progress. Success of PT bulls (defined by number of second-crop daughters) depended mainly on their EBV for final score, protein yield, and the type-production index. Significant correlations of sire EBV were found for final score and type-production index with the number of second-crop daughters (0.22 and 0.17). Likewise, significant correlations of dam EBV for final score and type-production index with the number of second crop daughters were found (0.25 and 0.18). Final score and protein yield were the main factors in success of a PT bull. The type-production index for PT bulls was not important for success unless it was 2.5 standard deviations above average. The PT bulls with low EBV for type-production index were used as proven bulls when they had higher EBV either for protein or final score.

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“…ly the pedigree indices (PI) of young sires are often considerably higher than their future EBVs based on progeny testing (Ferris and Wiggans 1991, Mao et al 1991, van der Werf et al 1994, Zhang et al 1994. One source of the bias can be a heterogeneous intraherd variance, which can be caused by reasons like small herd sizes (Uimari and Mäntysaari 1995), or upgrading of the breed, but also if animals of the same herd do not have the same environment; e.g., the superior cows could receive more attention from the farmer than their herd mates.…”

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confidence: 99%