| Popis: |
In-line milk progesterone records (n = 163,145) collected from June 2009 through November 2013 for 2,274 lactations of Holstein-Friesian cows in 12 commercial herds in the Netherlands were analyzed for commencement of luteal activity (CLA), luteal activity during first 60 days in milk (LA60), proportion of samples with luteal activity (PLA), interval from commencement of luteal activity to first service, length of first luteal phase, and number of inter-ovulatory intervals before first service. Heritability (0.13, 0.10, and 0.05) and repeatability estimates (0.26, 0.21, and 0.16) were greatest for CLA, PLA and LA60, respectively, compared with other traits. Genetic correlations were 0.96 to 0.99 between these traits. This study shows that in-line P4 records can be used to define and explore several heritable endocrine fertility traits that can be used in genetic improvement of fertility by selection. |
