Estimation of Genetic Parameters for Concentrations of Milk Urea Nitrogen

The objective of this study was to use field data collected by dairy herd improvement programs to estimate genetic parameters for concentrations of milk urea nitrogen (MUN). Edited data were 36,074 test-day records of MUN and yields of milk, fat, and protein obtained from 6102 cows in Holstein herds...

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Bibliographic Details
Published in:Journal of dairy science 2003-07, Vol.86 (7), p.2462-2469
Main Authors: Wood, G.M., Boettcher, P.J., Jamrozik, J., Jansen, G.B., Kelton, D.F.
Format: Article
Language:English
Subjects:
age
animal genetics
animal physiology
Animal productions
Animals
Biological and medical sciences
calving
calving season
Cattle - genetics
Cattle - metabolism
dairy cows
Environment
Female
Fundamental and applied biological sciences. Psychology
genetic correlation
genetic parameter
heritability
Lactation - genetics
lactation number
Lipids - analysis
Milk - chemistry
milk composition
milk fat yield
milk protein yield
Milk Proteins - analysis
milk urea nitrogen
milk yield
Nitrogen - analysis
parity (reproduction)
Phenotype
Regression Analysis
seasonal variation
Selection, Genetic
Terrestrial animal productions
urea
Urea - chemistry
Vertebrates
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Summary:The objective of this study was to use field data collected by dairy herd improvement programs to estimate genetic parameters for concentrations of milk urea nitrogen (MUN). Edited data were 36,074 test-day records of MUN and yields of milk, fat, and protein obtained from 6102 cows in Holstein herds in Ontario, Canada. Data were divided into three sets, for the first three lactations. Two analyses were performed on data from each lactation. The first procedure used ANOVA to estimate the significance of the effects of several environmental factors on MUN. Herd-test-day effects had the most significant impact on MUN. Effects of stage of lactation were also important, and MUN levels tended to increase from the time of peak yield until the end of lactation. The second analysis used a random regression model to estimate heritabilities and genetic correlations of MUN and the yield traits. Heritability estimates for MUN in lactations one, two, and three were 0.44, 0.59, and 0.48, respectively. Heritabilities for the yield traits were of a similar magnitude. Little relationship was observed between MUN and yield. Raw phenotypic correlations were all
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(03)73840-5