GENETIC PARAMETERS AND SELECTION RESPONSES FOR MILK PRODUCTION TRAITS OF THE FIRST LACTATION UNDER MONTHLY TEST DAY RECORDING SYSTEMS IN FLECKVIEH CATTLE

Data were collected in two consecutive years (1990 - 1991), it included 9652;
27158; 27886; 28017; 28049; 27842: 23902; 14517 and 9226 records of
different monthly test-day recording systems (SMRS) from the 2nd up to 10“ month of
the first lactation in Fleckvieh cows.
Yields of monthly test -day and simulated 305-day milk ,fal ,protein and fat-
plus- protein and percentage of protein yield /fat yield were studied Effects of calvmg
year- season. age at calving ,days open and stage of lactation were conSidered as
fixed effects ,and sire effect as random effect.
Data were analyzed using the LSMLMW computer program of Harvey
(7990).Variance components. heritabilities and genetic-, phenotypic- and
environmental correlations among those traits were estimated .The indirect selection
of those traits were calculated under the different recording systems (SMRS).
Heritability estimates for monthly test-day milk traits (TDMT) ranged from 0.19 to
0.48 Generally, the highest h2 estimates were under SMRSB (027 to 0.48); the
lowest were under SMRS; (0.19 to 0.23). Estimates of heritability for simulated 305-
day milk traits ( SMT) ranged from 0 40 to 0.61 under various SMRS. Generally, the
highest h2 estimates (0 54 to 0.61) were obtained under SMRSB up to SMRSm; the
lowest were under SMRSZ. Genetic- (rs) ,phenotypic- (rp) and environmental (r5)
correlations between simulated 305- day milk yield traits (SMYT) and monthly test-
day milk yield traits (TDMYT) under different SMRS were generally positive and
varied from moderate to high. Those estimates ranged from 059 to 1.0 for re, ; from
O 59 to 0.86 for rp and from 0.47 to O 76 for '5 Estimates of r6. rp and r5 between SVlT
and monthly test—day percentage of protein yield lfat yield (TDPOF%) varied generally
in direction and in magnitude from low to moderate .While, positive and moderate
estimates were observed between simulated 305- day percentage of protein yield /
fat yield (SPOF%) and TDPOF% and ranged from 0.78 to 0 99: 0.46 to 0.65 and 0 33
to 0 50 for r5, n: and r5, respectively
The results lead to conclude that us ng single trait selection for both TDMYT
(especially monthly test-day fat-plus- protein yield TDFPY) under SMRSB and
TDPOF% under SMRS; could be utilized satisfactorily for genetic improvement in
SMYT relative to other recording systems to obtain high genetic gain in MYT. This
procedure would ,also, reduce effort .time and costs of recording.