Evaluation of fertility traits of Friesian X Bunaji dairy cows
Data from 13 primaparous and 47 multiparous Friesian-Bunaji (F1) crossbred cows were used to evaluate the reproductive performance of Friesian x Bunaji dairy cows. Four fertility traits; days to first insemination (DFI), days open (DO), Non-return rate 56 days after first insemination (NRR56) and numbers of insemination per conception (NIC) were analysed . The results revealed that the average days to first insemination (DFI), days open (DO) , number of insemination per conception (NIC), and non- return rate 56 days after first insemination (NRR56) were 122.29 days, 171.18 days, 1.64, and 61%, respectively. These traits were highly variability (CV = 54.01-80.90%). The effects of sire and sex of calf on the reproductive characteristics were not significant (p>0.05). The dam body condition score (BCS) had significant effect on all the reproductive characteristics. The DFI, DO and NIC decreased with increase in BCS. Dams with BCS of < 2.50 had longer DFI and DO, and required higher number
of inseminations before conception (NIC), while those with BCS of >3.50 had shorter DFI and DO with minimum number of insemination per conception (1.00). Dam parity had no significant effect (p>0.05) on the reproductive characteristics except on NRR56 and NIC. However, the heifer had longer days to first insemination (DFI), and days open (DO) and
required higher number of inseminations per conception than the older cows. Season of calving had no significant effect (p>0.05) on the reproductive characteristics except on NRR56. The cows that calved during the wet seasons (early and late dry) had higher NRR56 (69 – 71%), than those of the dry (early and late wet) seasons (40 – 59%). The reproductive
performance of the cows depreciated significantly (p<0.05) within the 3 years (2010 - 2012) of this study; DFI increased from 88.47 to 131.49 days, DO increased from 80.39 to 269.14 days, NIC increased from 1.01 to 2.72, while the percentage non-return rate (NRR56) decreased from 86% to 42%.The heritability (h2) estimates for fertility traits was very low ranging from 0.014 to 0.087. Dam body condition score, parity, season and year of calving are important sources of variation in fertility traits of dairy cows. These results illustrate that environmental effects makes larger contributions to the variability of fertility traits than direct genetic effects, thus reproductive health and feeding management are very important
determinant of reproductive performance of dairy cows.
Keywords: Fertility, Friesian x Bunaji cows, Parity, Body condition score, Season, Year