title: The impact of hair coat color on longevity of Holstein cows in the tropics.
abstract: BACKGROUND
  Over two decades of observations in the field in South East Asia and Hawai'i suggest that majority of the commercial dairy herds are of black hair coat. Hence a simple study to determine the accuracy of the observation was conducted with two large dairy herds in Hawaii in the mid-1990s.
  
  
  METHODS
  A retrospective study on longevity of Holstein cattle in the tropics was conducted using DairyComp-305 lactation information coupled with phenotypic evaluation of hair coat color in two large dairy farms. Cows were classified into 3 groups: a) black (B, >90%); b) black/white (BW, 50:50) and c) white (W, >90%). Cows with other hair coat distribution were excluded from the study. In farm A, 211 out of 970 cows were identified having 4 or more lactations. In farm B, 690 out of 1,350 cows were identified with 2 or more lactations for the study.
  
  
  RESULTS
  The regression analyses and the Wilcoxon-Log-rank test for survival probability showed that Holstein cattle with 90% black hair coat had greater longevity compared to Holstein cattle with 90% white hair coat.
  
  
  CONCLUSIONS
  This study suggests that longevity of Holstein cattle in tropical regions was influenced by hair coat color and characteristics.
authors.affiliation: Department of Human Nutrition, Food and Animal Sciences, University of Hawaii-Manoa, Honolulu, HI 96822 USA.
authors.forename: C N
authors.initials: CN
authors.lastname: Lee
authors.affiliation: National Institute of Animal Science, RDA, Jeju Island, South Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Baek
authors.affiliation: Department of Statistics, University of Nebraska-Lincoln, Lincoln, NE 68583 USA.
authors.forename: A
authors.initials: A
authors.lastname: Parkhurst
keywords: Hair coat color; Holstein cows; Longevity; Milk production; Survival; Tropics