Survival analysis on calving interval and gestation length in Simmental x South Anatolian Red F1XB1 crossbred cows

GÜRCAN İ. S., Akcay A.

ANKARA UNIVERSITESI VETERINER FAKULTESI DERGISI, cilt.54, sa.3, ss.219-222, 2007 (SCI-Expanded) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 54 Sayı: 3
  • Basım Tarihi: 2007
  • Dergi Adı: ANKARA UNIVERSITESI VETERINER FAKULTESI DERGISI
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), TR DİZİN (ULAKBİM)
  • Sayfa Sayıları: ss.219-222
  • Anahtar Kelimeler: calving interval, censored data, gestation length, survival analysis
  • Ankara Üniversitesi Adresli: Evet

Özet

The objective of this study was to compare the survival analysis for calving interval and gestation length in Simmental x South Anatolian Red crossbred F(1)xB(1) cows. The data set consisted of 1775 lactation records from January 1987 to October 1991, of which 3.10% were censored. The mean calving interval was 382.26 days (15.39 S.D) for young cow group while it was 386.27 days (8.90 S.D) for old cow group. The mean calving interval in young cow group is shorter than old cow group (p<0.01). The mean gestation length was 276.04 days (10.55 S.D) for young cow group while it was 278.89 days (9.63 S.D) for old cow group. The mean gestation length in young cow group was 2 days shorter than old cow group (p<0.001). The distribution of longevity data is extremely skewed. The methods based on assumptions of normality may give biased parameter estimates. Survival analysis to estimate breeding values for longevity should be able to cope with censored data and time dependent variables.