No abstract

Our aim was to investigate whether four fertility traits were different in herds using the activity tag Heatime for reproduction management compared within other herds. The genetic parameters were estimated using animal models. The fertility traits were number of inseminations (NINS), interval from first to last insemination (IFL), age at first insemination (AFI), and age at first calving (AFC) in Danish Holstein heifers. The means of the traits were all significantly different between the two groups of herds. Heritabilities for NINS and IFL were lower than 1%, while heritabilities for AFI and AFC were 12-29%. Heritabilities were all lower in Heatime herds than in reference herds. The genetic correlations between traits in different environments were high for NINS, AFI, and AFC (>0.88), while the correlation for IFL was 0.68 but with a higher SE (0.313). Thus, IFL seems not to be the same trait in Heatime and reference herds.