Skip to main content
ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #117057
Title: HETEROGENEITY OF VARIANCE AND ESTIMATION OF GENETIC PARAMETERS

Author
item VAN VLECK, LLOYD
item SPLAN, REBECCA - VIRGINIA TECH UNIVERSITY
item CUNDIFF, LARRY

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/5/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The Germ Plasm Evaluation (GPE) project at the USMARC encompasses two generations of matings. The F1 progeny of several sire breeds mated to Hereford and Angus cows are measured directly. The F1 heifers are then mated to bulls of other breeds which allows for expression of maternal characteristics of the original sire breeds. The two sets of data can be combined to estimate direct (h-2) and maternal (m-2) heritability and the direct-maternal genetic correlation r(a,m). For this study, 14 sire breeds were included. Two traits, birth weight (BWT) and weaning weight (WWT) were analyzed. The numbers of observations available were 3,530 and 5,610 for direct BWT and WWT and 7,095 and 8,591 for maternal BWT and WWT. For WWT, little descrepancy was found between separate analyses of the two data sets and the combined data set or when standardized by dividing by the respective standard deviations. For BWT, h-2 estimates were .48 and .35 for rdirect and maternal data but for the combined data, h-2 was .64, m-2 was .06, and r(a,m) was -.23. When records within data set were standardized by dividing by the respective standard deviations; h-2, m-2, and r(a,m) were .54, .06, and -.03. When records were standardized by the unadjusted standard deviations; h-2, m-2, and r(a,m) were .45, .06, and .18. For WWT, ratio of phenotypic SD for the two data files was (23.5/21.8). For BWT, the ratios were 4.35/4.57 and 5.36/6.09 (unadjusted). Heterogeneity of variance across generations and method of standardizing variances seem to influence estimates of heritability and the direct-maternal genetic correlation.