To some extent, consideration was also taken to the bull-breeding index for calving ease, in which a bull with a low incidence of calving difficulty (a high index for calving ease) was preferred.
In the same manner, a calving ease index below 100 indicates a higher risk of calving problems, compared with a calving ease index above 100.
The AIPL effect size distributions ranked this marker #3 for daughter calving ease, #18 for service-sire calving ease, and #20 for body depth.
These included SNP effects for daughter calving ease, sire calving ease and protein percentage, but most of the effects fell in gene-sparse areas.
Breeding values related to calving ease and stillbirth are commonly available (Interbull, 2013).
This study evaluates different models for calving ease and stillbirth in United Kingdom Holstein-Friesian cattle.
This QTL was associated with most body weights and with calving ease direct in these breeds.
Similarly, many highly significant LS results for fat yield, protein yield, protein percentage, service-sire sire calving ease, daughter calving ease and foot angle were eliminated once the elite cows were removed.
*P < 0.05; heritabilities and genetic correlations DCE = direct calving ease, DSB = direct stillbirth, DGL = direct gestation length, MCE = maternal calving ease, MSB = maternal stillbirth, MGL = maternal gestation length; standard errors are indicated in brackets.
Highly significant chromosome regions and genes for this composite trait involved the significant regions and genes for milk, fat and protein yields, protein percentage, service sire calving ease, daughter calving ease, and service sire stillbirth (Additional File 5: Table S2.13).
Milkability belongs to the group of traits termed functional traits, which also include health, feed efficiency, fertility, and calving ease.
