Phenotypic, genetic and environmental trends in Kenya Sahiwal cattle
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Date
1988Author
Wanambacha, Jacob W
Type
ThesisLanguage
enMetadata
Show full item recordAbstract
Records covering a 20 year period (1964-1983) on
Sahiwal cows at the National Sahiwal Stud, Naivasha
were used to estimate phenotypic, genetic and
environmental trends of 305- day milk yield, calving
interval, birth weight and age at 55 kg liveweight
(AGE55) by best linear unbiased prediction (BLUP)
procedures while genetic parameters were estimated by
the maximum likelihood procedure. All the traits
studied were regarded as the traits of the dam. The
number of records analysed were 4837, 4272, 4837 and
3544 for milk yield, calving interval, birth weight and
age at 55 kg liveweight, respectively.
The means of 30S-day milk yield, calving interval,
birth weight and AGE55 were 1662~8.3 kg, 426.2+1.5 d,
22.7+0.04 kg and 97.8±..0.7 d , respectively. Year of
calving or birth affected al I the four traits studied.
Season of birth affected AGE55 only. Parity affected
all the traits except calving interval while sex of
calf affected birth weight, calving interval and AGE55.
The respective repeatability and heritability estimates
were 0.46±..0.02 and 0.27+0.06 for milk yield; 0.39+0.20
and 0.15~0.lO for calving interval; 0.48+0.05 and
0.40~0.07 for birth weight; and O.46±..0.03 and 0.35+0.05
for AGE55.
The respective
environmental changes
-15.42+5.0 kg for
annual phenotypic, genetic and
we re: -11 .56~5. 3, 3. 57±..0.64 CI. nd
305-day m i Ik yiel d; 2. 43±..0.63,
-0.23+0.03 Clnd 2.65+0.64 d for calving interval;
xii i
-0.02.::0.02, 0.004~0.003 and -0.03~0.02 kg for birth
weight; and 5.26.::0.25, -0.05~0.04 and 5.31~0.26 d for
AGE55. All the environmental trends were highly
significant (p<O.Ol).AI I phenotypic trends were highly
significant (p<O.Ol) except for birth weight. Genetic
trends were highly significant Cp<O.Ol) except for
birth weight and AGE55. In al I the four traits the
correlations between environmental and phenotypic
trends were highly significant (p<O.Ol). Although the
annual genetic changes were in the direction of the
breeding objectives, the annual genetic change in milk
yield was lower than expected.
Citation
Wanambacha, J.W(1988). Phenotypic, genetic and environmental trends in Kenya Sahiwal cattleSponsorhip
University of NairobiPublisher
Departmeni of Animal Production, University of Nairobi
Description
Msc-Thesis