2.1. General History of Genetic an Animal
2.2. General Manner of Genetic Parameters
2.3. Previously of Researches
2.4. Specification of Genetic Parameters
2.4.1. Calving Difficulty
Calving difficulty of Holsteins has a major economic impact on the dairy cattle industry. The National Association of Animal Breeders sponsors genetic evaluation of AI sires for calving ease. The AI organizations and dairy records processing centers collect data from herds that have progeny of AI bulls. Genetic predictions of merit for calving ease have been available for Holstein AI bulls in the US since 1978. A threshold model was implemented during 1988. The threshold model adjusts for the effects of herd-year, season, sex of calf, parity, and birth-year group of sire to predict the genetic merit of each sire for calving ease. Pedigree information from sires, sons, and grandsons is also included in the analysis to improve the reliability of genetic predictions for bulls that have pedigree data available. Each sire’s genetic prediction for calving ease is reported as the expected percentage of difficult births of primiparous cows. National in scope, genetic predictions for calving ease are used internationally by breeders of dairy cattle to minimize the risk of difficult births of primiparous cows and to increase the use of AI for young cows.
Genetic improvement programs have been applied to a wide number of traits of dairy cattle. Although the selection objective is usually limited to increased production, other traits can improve the economic efficiency of individual herd breeding programs. Dystocia, defined as delayed and difficult parturition, has a major economic impact on the dairy cattle industry (4, 6, 12). The purpose of this paper is to focus on current policies and procedures for the genetic evaluation of AI sires in the US for calving ease. A full discussion of technical details is not possible here in.
Brief History
Research on dystocia began in 1972 under the direction of Pollak and Freeman (11) at Iowa State University with data provided by Midwest Breeders Cooperative, which is now 21st Century Genetics (Shawano, WI). Select Sires (Plain City, OH) also collected some early data. Pollak (10) analyzed the first data on dystocia in Holsteins and later identified many of the factors associated with dystocia (e.g., season of birth, sex of calf, parity of dam, and sire of calf) (11). During 1977, the National Association of Animal Breeders WAAB) began sponsoring the evaluation of Holstein AI sires in the United States for calving ease. Initially, evaluations were computed within AI organizations. Beginning in 1980, the evaluations were computed across all AI organizations to allow inter-organizational comparisons. Scores for calving ease were analyzed until 1987 with a BLUP sire model (2) that included the inverse of the relationship matrix among sires. An ordered categorical analysis that uses a threshold model was implemented during 1988 (3, 5). Reliability of each sire’s evaluation,
2.4.2. Birth Weight
2.2. General Manner of Genetic Parameters
2.3. Previously of Researches
2.4. Specification of Genetic Parameters
2.4.1. Calving Difficulty
Calving difficulty of Holsteins has a major economic impact on the dairy cattle industry. The National Association of Animal Breeders sponsors genetic evaluation of AI sires for calving ease. The AI organizations and dairy records processing centers collect data from herds that have progeny of AI bulls. Genetic predictions of merit for calving ease have been available for Holstein AI bulls in the US since 1978. A threshold model was implemented during 1988. The threshold model adjusts for the effects of herd-year, season, sex of calf, parity, and birth-year group of sire to predict the genetic merit of each sire for calving ease. Pedigree information from sires, sons, and grandsons is also included in the analysis to improve the reliability of genetic predictions for bulls that have pedigree data available. Each sire’s genetic prediction for calving ease is reported as the expected percentage of difficult births of primiparous cows. National in scope, genetic predictions for calving ease are used internationally by breeders of dairy cattle to minimize the risk of difficult births of primiparous cows and to increase the use of AI for young cows.
Genetic improvement programs have been applied to a wide number of traits of dairy cattle. Although the selection objective is usually limited to increased production, other traits can improve the economic efficiency of individual herd breeding programs. Dystocia, defined as delayed and difficult parturition, has a major economic impact on the dairy cattle industry (4, 6, 12). The purpose of this paper is to focus on current policies and procedures for the genetic evaluation of AI sires in the US for calving ease. A full discussion of technical details is not possible here in.
Brief History
Research on dystocia began in 1972 under the direction of Pollak and Freeman (11) at Iowa State University with data provided by Midwest Breeders Cooperative, which is now 21st Century Genetics (Shawano, WI). Select Sires (Plain City, OH) also collected some early data. Pollak (10) analyzed the first data on dystocia in Holsteins and later identified many of the factors associated with dystocia (e.g., season of birth, sex of calf, parity of dam, and sire of calf) (11). During 1977, the National Association of Animal Breeders WAAB) began sponsoring the evaluation of Holstein AI sires in the United States for calving ease. Initially, evaluations were computed within AI organizations. Beginning in 1980, the evaluations were computed across all AI organizations to allow inter-organizational comparisons. Scores for calving ease were analyzed until 1987 with a BLUP sire model (2) that included the inverse of the relationship matrix among sires. An ordered categorical analysis that uses a threshold model was implemented during 1988 (3, 5). Reliability of each sire’s evaluation,
2.4.2. Birth Weight
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