MOST PROBABLE PRODUCING ABILITY, FERTILITY AND RELATED SELECTION CRITERIA FOR HEREFORD COWS

Persistent Link:
http://hdl.handle.net/10150/282536
Title:
MOST PROBABLE PRODUCING ABILITY, FERTILITY AND RELATED SELECTION CRITERIA FOR HEREFORD COWS
Author:
Itulya, Susan B.
Issue Date:
1980
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Data on 5130 registered Hereford cattle owned and managed by the San Carlos Apache Indian tribe were used to study cow productivity in terms of Most Probable Producing Ability and fertility. Analyses of variance and regression analyses were utilized to investigate sources of variation in the weaning weights of the calves and in their day of birth (which was a measure of cow fertility). Heritability estimates for various weights and gains and correlations (genetic, environmental and phenotypic) for weights, gains and MPPA were also calculated. Large year effects caused the most variation in weaning weight. Important too, were the effects of age of dam, interaction between year and age of dam and regression of weaning weight on day of birth. The repeatability of weaning weight was .25. This value was low compared to the average usually seen. Heritability estimates for weaning weight were .05 for males and .18 for females. Not much progress could be made selecting for weight at that stage. The heritability of postweaning weights were higher. The values for 20-month-weight were .46 for males and .31 for females, indicating reasonable progress could be made selecting for weight at that age. Twelve-month-weight had heritability estimates of .21 (males) and .17 (females). Since a weight loss occurred during the period between weaning and the 12-month-stage, the trait being measured may be a response to nutritional stress. The genetic correlations between weights at various stages were high. Some of the same genes are responsible for weights at various stages of growth. Correlations (genetic) between the weights and MPPA were generally low except the correlation of 12-month-weight with MPPA (.41). Day of birth measured as a trait of the calf was a reflection of gestation length. Heritability estimates for day of birth were .26 for calves of cows dry during the breeding season and .04 for the calves of lactating cows. When calculated as a trait of the cow, day of birth was considered a measure of cow fertility with a resulting heritability of .09. In evaluating overall cow productivity both MPPA and fertility must be considered jointly, perhaps in the form of a selection index or through independent culling levels.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Hereford cattle -- Breeding.; Hereford cattle -- Arizona.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Genetics
Degree Grantor:
University of Arizona
Advisor:
Ray, Donald E.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMOST PROBABLE PRODUCING ABILITY, FERTILITY AND RELATED SELECTION CRITERIA FOR HEREFORD COWSen_US
dc.creatorItulya, Susan B.en_US
dc.contributor.authorItulya, Susan B.en_US
dc.date.issued1980en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractData on 5130 registered Hereford cattle owned and managed by the San Carlos Apache Indian tribe were used to study cow productivity in terms of Most Probable Producing Ability and fertility. Analyses of variance and regression analyses were utilized to investigate sources of variation in the weaning weights of the calves and in their day of birth (which was a measure of cow fertility). Heritability estimates for various weights and gains and correlations (genetic, environmental and phenotypic) for weights, gains and MPPA were also calculated. Large year effects caused the most variation in weaning weight. Important too, were the effects of age of dam, interaction between year and age of dam and regression of weaning weight on day of birth. The repeatability of weaning weight was .25. This value was low compared to the average usually seen. Heritability estimates for weaning weight were .05 for males and .18 for females. Not much progress could be made selecting for weight at that stage. The heritability of postweaning weights were higher. The values for 20-month-weight were .46 for males and .31 for females, indicating reasonable progress could be made selecting for weight at that age. Twelve-month-weight had heritability estimates of .21 (males) and .17 (females). Since a weight loss occurred during the period between weaning and the 12-month-stage, the trait being measured may be a response to nutritional stress. The genetic correlations between weights at various stages were high. Some of the same genes are responsible for weights at various stages of growth. Correlations (genetic) between the weights and MPPA were generally low except the correlation of 12-month-weight with MPPA (.41). Day of birth measured as a trait of the calf was a reflection of gestation length. Heritability estimates for day of birth were .26 for calves of cows dry during the breeding season and .04 for the calves of lactating cows. When calculated as a trait of the cow, day of birth was considered a measure of cow fertility with a resulting heritability of .09. In evaluating overall cow productivity both MPPA and fertility must be considered jointly, perhaps in the form of a selection index or through independent culling levels.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectHereford cattle -- Breeding.en_US
dc.subjectHereford cattle -- Arizona.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeneticsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRay, Donald E.en_US
dc.identifier.proquest8027744en_US
dc.identifier.oclc8696747en_US
dc.identifier.bibrecord.b13910036en_US
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