title: Genetic evaluation of in-line recorded milkability from milking parlors and automatic milking systems.
abstract: The overall objective of this study was to assess the use of in-line recorded milkability information from dairy herds with conventional milking parlors (CMP) and from herds with automatic milking systems (AMS) for genetic evaluation. Some genetic parameters were previously studied on AMS data for 2,053 Swedish Holstein (SH) and 1,749 Swedish Red (SR) cows in 19 herds. These data were combined in the present paper with milkability information from 74 herds with CMP, including 11,123 SH cows and 7,554 SR cows. Genetic parameters were estimated for the CMP data and genetic correlations were estimated between milkability traits measured in the 2 systems. Average flow rate and milking time were derived and used as similar milkability traits for both systems, whereas box time was used only for AMS herds. Estimated heritabilities were in the range from 0.24 to 0.49. Even though the traits were differently defined in the 2 milking systems, the corresponding traits recorded in AMS and CMP were genetically closely related (0.93-1.00). Similarly, close genetic relationships were shown between milkability traits in different lactations in both breeds (0.93-0.99). Thus, it should be possible to treat milkability traits in different lactations and from different milking systems as the same traits in genetic evaluations. The various milkability traits were also highly genetically correlated, indicating that the inclusion of just one trait in the genetic selection program would efficiently select for milkability without the need to consider all measures. Comparisons of repeatability and random regression models, combining all information from the 2 systems for genetic evaluation, were done to find the most suitable model for genetic evaluation purposes. Even though the random regression models were favored in the formal model tests to evaluate suitability, correlation coefficients between test-days within lactation were high (0.7-0.8) and small differences in breeding values resulted among different models. That would indicate that a few test-days per cow would produce accurate breeding values for milkability.
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, SE-750 07 Uppsala, Sweden. Electronic address: caroline.carlstrom@slu.se.
authors.forename: C
authors.initials: C
authors.lastname: Carlström
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, SE-750 07 Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Strandberg
authors.affiliation: Växa Sweden, Box 7023, S-75007 Uppsala, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Johansson
authors.affiliation: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, SE-753 23 Uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Pettersson
authors.affiliation: Viking Genetics, Box 64, S-532 21 Skara, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Stålhammar
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, SE-750 07 Uppsala, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Philipsson
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001947:Breeding; D002417:Cattle / Q000235:genetics* / Q000502:physiology*; D003612:Dairying / Q000379:methods*; D005260:Female; D008892:Milk; D008954:Models, Biological; D012641:Selection, Genetic
keywords: genetic evaluation; genetic parameter; milk flow rate; milking system