Abstract
The edited data set for the estimation of heritability, genetic and phenotypic correlations of fertility traits contained up to 23,402 records from 10,894 cows calved between 2001 and 2015. Heritability estimates for success in first service (FS), gestation length (GL), number of inseminations (NI), insemination outcome (IO), calving interval (CI), calving birth weight (CBW) and days open (DO) were low and ranged between 0.016 (DO) and 0.123 (GL). Repeatability of fertility traits was estimated to vary from 0.021 (FS) to 0.411 (IO). The genetic correlations between DO × CI, DO × NI and CI × NI were positive and nearly perfect (0.98, 0.88 and 0.88, respectively), while those between DO × IO and CI × IO were negative (-0.98 and -1, respectively). Further, the phenotypic correlations between DO × CI, DO × NI, CI × NI, CBW × IO and SF × IO were 0.99, 0.83, 0.83, 0.99 and 1, respectively, while those between DO × IO, CI × IO, GL × IO and NI × IO were -0.99, -0.99, -0.99 and -1, respectively. Overall genetic parameters imply a good practical management in heat stress conditions will be essential for improving fertility efficiency.
Highlights
Fertility traits are considered very important because of their impact on the economy of dairy cattle breeding
The temperature–humidity index (THI) was lowest in January and February, which was associated with the winter season, and highest in June through September, which was associated with the summer season and heat stress condition
The joint analysis of calving interval (CI) and number of inseminations (NI) indicates that the genetic correlation between these 2 traits was 0.88, consistent with those reported by González-Recio and Alenda (2005) and Eghbalsaied (2011) (0.89 and 0.81, respectively). These results suggest that these reproductive traits (DO × CI, days open (DO) × NI and CI × NI) are almost genetically equivalent, i.e., they are influenced by the same genes
Summary
Fertility traits are considered very important because of their impact on the economy of dairy cattle breeding. Pozveh, Shadparvar, Shahrbabak, and Taromsari (2009) estimated genetic parameters for calving interval (CI), days open (DO), and gestation length (GL) in traits collected by the Animal Breeding Center of Iran from 1980 to 2004 on a data set including fertility records from 6000 cows. These traits and other economically important traits, such as number of insemination (NI), insemination outcome (IO), success in first service (SF) and calving birth weight (CBW) were not considered in heat stress condition. The objectives of this study were to estimate heritability, repeatability, genetic and phenotypic correlations of fertility traits of Holstein dairy cattle in warm and temperate climate
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