Genetic Studies On Replacement Rate And First Lactation Traits In Holstein Friesian Cattle At Holeta Bull Dam Station Ethiopia

The study was conducted on 901 Holstein Friesian cows maintained at Holeta Bull Dam Station fromrn1976 to 2003 with the objectives of estimating demographic parameters, genetic of replacement ratesrnand first lactation traits. The lactation specific parameters viz. loss rate, survival rate, stayability,rnexpected herd life, female calf births and reproductive value at first lactation were estimated atrn0.2619, 0.7381, 0.7373, 2.4573, 0.4808 and 1.0488, respectively. Overall lifetime parameter valuesrnfor mean lactations of cows present, mean lactations of cows lost, mean rate of loss per cow perrnlactation, average life expectancy at birth, net reproductive rate and generation interval wererncomputed as 3.4949 lactations, 4.3548 lactations, 0.3204, 1.2825 lactations, 1.4984 female calves perrncow and 3.5451 years, respectively. The overall averages for abnormal and normal births, malefemalernsex ratios, mortality and culling rate in females up to age at first calving and femalernreplacement rates based on female births and total pregnancies were 12% and 88%, 52.5% and 47.5%,rn23% and 7% and 70% and 29%, respectively. The effects of parity and year of calving on above traitsrnwere found to be significant, except parity effects on culling rate and replacement rate based on totalrnpregnancies, which were non-significant. The season effects for all traits were non-significant. Sirernaffected significantly the type of birth, calf loss, replacement rate and coefficient of gene replication.rnAbout 1/3rd of cows calved only once and similar proportion of the cows experienced abnormalrncalving during first lactation. The overall means for longevity, productive herd life, total calves,rnfemale calves, selective values and coefficient of gene replication were 2864±63 days, 1638±58 days,rn3.55±0.12, 1.68±0.07, 1.12±0.06 and 0.56±0.03. Cows calved at early age and low producers hadrnshort herd life, less number of total and female calves. Heritability for abnormal birth, sex ratio,rnmortality, culling, and replacement rate from total calves produced and total pregnancy werern0.16±0.009, 0.10±0.019, 0.18±0.029, 0.71±0.029, 0.00±00 and 0.66±0.029, respectively. Thernrepeatability for the above traits were 0.964±0.012, 0.038±0.017, 0.060±0.028, 0.0895±0.029,rn0.780±0.019 and -0.2403±0.022, respectively. The heritability estimates for longevity, productivernherd life, total calves born, total normal calves born, total female calves born, coefficient of genernreplication and selective value were 0.31±0.085, 0.32±0.088, 0.11±0.018, 0.12±0.018, 0.10±0.019, -rn0.08±0.029 and 0.66±0.029, respectively. The heritability for age at first calving (AFC), first servicernperiod (FSP), first dry period (FDP), fist lactation period (FLP), 305 day milk (305DMY), firstrnlactation milk yield (FLMY) and first calving interval (FCI) were 0.53±0.116, 0.26±0.113,rn0.24±0.1170, 0.23±0.102, 0.23±0.106, 0.28±0.124 and 0.28±0.141, respectively. The phenotypicrncorrelations of AFC with FLMY, 305DMY, FLP, FSP and FCL were very small. High phenotypic,rngenetic and environmental correlations existed between FLMY and 305DMY. All correlations amongrnFSP, FDP and FCL were high and positive. Sire affected the additive genetic variances for abnormalrnbirth, mortality, culling and replacement rate and their frequency can be changed through selection ofrnthe sire. Moreover, information on the genotype of semen must be available along with production.rnAge at first calving had high heritability value and it can be included in the selection index. Furtherrnresearch is required on identification of genetic abnormalities at embryonic and progeny level and therneffect of storage and deposition of semen on sex ratio.

Get Full Work

Report copyright infringement or plagiarism