title: Short communication: Genetic correlation and heritability of milk coagulation traits within and across lactations in Holstein cows using multiple-lactation random regression animal models.
abstract: Genetic parameters of milk rennet coagulation time (RCT) and curd firmness (a30) among the first 3 lactations in Holstein cows were estimated. The data set included 39,960 test-day records from 5,216 Estonian Holstein cows (the progeny of 306 sires), which were recorded from April 2005 to May 2010 in 98 herds across the country. A multiple-lactation random regression animal model was used. Individual milk samples from each cow were collected during routine milk recording. These samples were analyzed for milk composition and coagulation traits with intervals of 2 to 3 mo in each lactation (7 to 305 DIM) and from first to third lactation. Mean heritabilities were 0.36, 0.32, and 0.28 for log-transformed RCT [ln(RCT)] and 0.47, 0.40, and 0.62 for a30 for parities 1, 2, and 3, respectively. Mean repeatabilities for ln(RCT) were 0.53, 0.55, and 0.56, but 0.59, 0.61, and 0.68 for a30 for parities 1, 2 and 3, respectively. Mean genetic correlations between ln(RCT) and a30 were -0.19, -0.14, and 0.02 for parities 1, 2, and 3, respectively. Mean genetic correlations were 0.91, 0.79, and 0.99 for ln(RCT), and 0.95, 0.94, and 0.94 for a30 between parities 1 and 2, 1 and 3, and 2 and 3, respectively. Due to these high genetic correlations, we concluded that for a proper genetic evaluation of milk coagulation properties it is sufficient to record RCT and a30 only in the first lactation.
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia. Electronic address: denis.pretto@emu.ee.
authors.forename: D
authors.initials: D
authors.lastname: Pretto
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia; Bio-Competence Centre of Healthy Dairy Products LLC, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: M
authors.initials: M
authors.lastname: Vallas
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia; Bio-Competence Centre of Healthy Dairy Products LLC, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: E
authors.initials: E
authors.lastname: Pärna
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia; Bio-Competence Centre of Healthy Dairy Products LLC, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: A
authors.initials: A
authors.lastname: Tänavots
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia; Bio-Competence Centre of Healthy Dairy Products LLC, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: H
authors.initials: H
authors.lastname: Kiiman
authors.affiliation: Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia; Bio-Competence Centre of Healthy Dairy Products LLC, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: T
authors.initials: T
authors.lastname: Kaart
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000502:physiology; D012085:Chymosin / Q000378:metabolism*; D005260:Female; D005838:Genotype; D007774:Lactation; D008892:Milk / Q000201:enzymology*; D023421:Models, Animal; D015999:Multivariate Analysis; D010298:Parity; D010641:Phenotype; D011247:Pregnancy; D012044:Regression Analysis
chemical_list: C025350:rennet; D012085:Chymosin
keywords: genetic correlation; milk coagulation property; multiple-lactation model; random regression