|Van Vleck, Lloyd|
Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2004
Publication Date: 3/1/2005
Citation: Al-Seaf, A., Hanford, K.J., Keown, J.F., Van Vleck, L.D. 2005. Estimates of genetic parameters for yield traits and scs for cows treated or not treated with bovine somatotropin [abstract]. Midwestern Section of the American Society of Animal Science 83(2):40. Interpretive Summary: No interpretive summary is required.
Technical Abstract: Records from DRPC, Raleigh, NC were divided into three sets: 1) first lactation, 2) second lactation and 3) lactations from three to five. About 10% were for cows treated with bovine somatotropin (bST). Numbers of records for treated and untreated cows by set were 4,337 and 48,765; 3,730 and 37,796; and 3,645 and 33,957. A two-trait animal model with records of cows treated or untreated as different traits was used to estimate genetic parameters for milk traits and somatic cell score. Cows treated with bST produced more milk than untreated cows by 10.0, 9.6, and 7.7 kg/100, respectively. Cows with bST had lower SCS than cows not receiving bST for Set 1 (-0.4). Estimates of heritability for milk yield for treated and untreated cows were (0.13, 0.16 and 0.09) and (0.18, 0.18 and 0.14). Corresponding estimates of repeatability for Set 3 were 0.50 and 0.41 for treated and untreated cows. Estimates of heritability for fat for treated and untreated cows were (0.31, 0.16 and 0.12) and (0.27, 0.21 and 0.16), with estimates of repeatability of 0.45 and 0.40. Estimates of heritability for protein yield for treated and untreated cows were (0.13, 0.17 and 0.12) and (0.20, 0.23 and 0.16). In general, estimates of heritability for milk yield traits were less for Set 3 than for first and second lactations for both treated and untreated cows. Estimates of heritability for somatic cell score for treated and untreated cows were (0.09, 0.15 and 0.13) and (0.11, 0.13 and 0.13) with estimates of repeatability of 0.52 and 0.45. Estimates of genetic correlations were high between milk yields of cows with and without bST (0.99) for first and later lactations and about 0.70 for second lactations. Fat and protein had similar estimates of genetic correlations. Estimates of genetic correlations for somatic cell score were 0.99 for Sets 1, 2, and 3. Estimates of genetic correlations between treated and untreated cows were high enough to consider records to be one trait for selection.