Variance Components and Sire Evaluation for Milk Flow Rates
نویسندگان
چکیده
منابع مشابه
Sire Evaluation by Only Extended Partial Milk and Fat Records
The standard of comparison for dairy production records is the 305-day lactation, and much research has been directed to estimating 305-day milk and fat records from incomplete or in-progress records. This study was to determine the effect of several methods of extending incomplete records on sire evaluation. Complete 305-day milk and fat records of first lactations of 73,724 daughters of 1,362...
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The effects of heterogeneity of variance among herds on dairy sire evaluation were examined. Data consisted of 111,196 first lactation Holstein production records of heifers calving in Ontario between 1978 and 1983. To account for selection, older sires without first crop daughters in the data were treated as fixed effects. Herds were classified into one of nine groups based on their estimated ...
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Variance components for a sire-maternal grandsire (MGS) threshold model were estimated from subsets of the US calving ease (CE) database, which includes over 10 million calving records with CE scored 1 (no problem) to 5 (extreme difficulty). Selected records included sire and MGS among the 2601 most frequently appearing bulls. The data were further restricted by requiring at least 20 records in...
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The animal model for genetic evaluations of dairy cattle by the USDA currently includes a term for interaction effects of sire and herd. The relative magnitude of the variance of that effect was established in the 1960s as 14% of the total variance, but recent research has shown that the proportion is 2% or less. This report compared EBV using either the 14% or the actual estimate from 20 sampl...
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(Co)variance components for stillbirth in US Holsteins were estimated under a sire-maternal grandsire threshold model using subsets of data from the national calving ease database, which includes over 6 million calving records with associated stillbirth scores. Stillbirth was coded as a binomial trait indicating whether the calf was alive 48 h postpartum. Records were selected for calves whose ...
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ژورنال
عنوان ژورنال: Journal of Dairy Science
سال: 1979
ISSN: 0022-0302
DOI: 10.3168/jds.s0022-0302(79)83295-6