Abstract
Selection to improve dairy cattle production leads to a decline in fertility performance due to unfavourable association between the traits. Analysis was carried out to study the genetic trend in the fertility traits of Karan Fries (Holstein Friesian crossbred) cattle due to selection favouring production traits. Data spread over a period of 34 years (1978 to 2012) were utilized to study the traits viz . first lactation 305 day milk yield (F305MY), first service period (FSP) and first lactation daughter pregnancy rate (FDPR). Heritability estimates were obtained using average information restricted maximum likelihood (AIREML) were 0.31±0.10, 0.12±0.06 and 0.02±0.05 for F305MY FSP, and FDPR, respectively. Significant phenotypic trend estimates obtained for F305MY, FSP and FDPR were 18.71±8.37 kg/year, 1.14±0.51 days and -0.0061±0.0018, respectively. Unfavourable genetic trend estimates of -0.0012±0.0004 was obtained for FDPR. The results indicated that continuous selection for production performance had negatively impacted fertility which was evident from a declining trend in fertility performance of Karan Fries cattle in contrast to an increasing trend in production performance.
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