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

Abstract

The objective of this study was to compare the survival analysis for calving interval and gestation length in 1Simmental x South Anatolian Red crossbred F1XBBBOctober 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

Keywords

• Calving interval
• censored data
• gestation length
• survival analysis

Simental x Güneydoğu Anadolu Kırmızısı F1XBB1 melezi ineklerin buzağılama aralığı ve gebeliksüresinin yaşam analizi ile incelenmesi

Abstract

Bu çalışmada, Simmental x Güneydoğu Anadolu F1XBBmelezi genç ve ergin çağdaki ineklerde, buzağılama aralığı ve gebelik süreleri, yaşam analizi metodu ile incelenmiştir. Çalışmanın verileri, Ceylanpınar tarım işletmesinde Ocak 1987 ile Ekim 1999 tarihleri arasında yer alan 1775 laktasyon kayıdından elde edilmiştir. Verilerin %3.1’i sensörlüdür. Genç ineklerin ortalama buzağılama aralığının, (382.26 ± 15.39 Gün) ergin yaştakilerden (386.27 ± 8.9 Gün) daha kısa olduğu (p<0.01), ergin yaştakilerin gebelik süresinin (278.89 ± 9.63 S) gençlerden (276.04 ±10.55 S) 2 gün daha fazla olduğu görülmüştür (p<0.001). Yaşam verilerine ait damızlık değerlerinin tahmin edildiği çalışmalarda normallik varsayımı üzerine kurulu metotlar yanlı tahminler vermektedir. Zamana bağımlı ve sansürlü verilerin analizinde yaşam analizi metodu kullanılmalıdır

Keywords

• Buzağılama aralığı
• gebelik süresi
• sansürlü veri
• yaşam analizi

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