title: Genetic evaluation of dairy sires for milking duration using electronically recorded milking times of their daughters.
abstract: The potential of using electronically recorded data from on-farm milking parlor and herd management software programs for genetic evaluation of dairy sires for milking duration of their daughters was assessed in the present study. Single measurements of milking duration were collected weekly from 29 herds between June 1, 2003 and April 1, 2004. These included 73,547 observations corresponding to 10,152 Holstein cows from 1551 sires. Average milking duration for a single milking in our data set was 4.5 min. Estimated heritability of milking duration was 0.17, and predicted transmitting abilities (PTA) of individual sires ranged from -0.48 min for sires with the fastest milking daughters to 0.59 min for sires with the slowest milking daughters. The correlation between PTA for milking duration and PTA for somatic cell score (SCS) was -0.15, indicating that sires whose daughters milk most quickly also tend to transmit higher SCS to their progeny. Correlations between PTA milking duration and PTA for teat placement and teat length were -0.14 and 0.20, respectively, indicating that sires that transmit wide teat placement and long teats tend to have daughters that milk slowly. Based on the results presented herein, it appears that genetic selection based on objective, electronically recorded milking times is possible. This approach would greatly improve the quality and efficiency of data collection relative to conventional evaluations of milking speed, which are based on farmer surveys. The number of herds currently equipped to routinely capture milking times is limited, but this number is increasing very rapidly. Future research should focus on refinement of data reporting and validation systems, as well as estimation of the economic value of milking duration. This trait may have an intermediate optimum, because cows that milk too slowly will disrupt parlor flow and reduce milking efficiency, but cows that milk too quickly may be at greater risk for mastitis.
authors.affiliation: University of Wisconsin, Department of Dairy Science, Madison, WI 53706, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Zwald
authors.forename: K A
authors.initials: KA
authors.lastname: Weigel
authors.forename: Y M
authors.initials: YM
authors.lastname: Chang
authors.forename: R D
authors.initials: RD
authors.lastname: Welper
authors.forename: J S
authors.initials: JS
authors.lastname: Clay
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000502:physiology; D002452:Cell Count / Q000662:veterinary; D005260:Female; D020022:Genetic Predisposition to Disease; D007774:Lactation / Q000235:genetics / Q000502:physiology*; D008297:Male; D008321:Mammary Glands, Animal / Q000033:anatomy & histology* / Q000502:physiology; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000235:genetics; D008892:Milk / Q000166:cytology / Q000378:metabolism; D013997:Time Factors