Abstract:
The model of wood (1967) which is used to fit the lactation yield data
of dairy cattle on time had been adopted here to fit egg production
curve for two hybrid layer strains and their standard manual.
The strains are Hyline W98 and Lohmman LSL which kept under
Sudan conditions. The egg production performance data of four
poultry farms in different size in Khartoum state were used. Two of
those farms reared Lohmman LSL hybrid strain while the other two
farms reared Hyline W98 hybrid strain. The traits of age at the first
lay, age at 50%, H.D production, age at peak production, percentage at
peak, mortality rate, feed intake and production period were
calculated and tested for the significance of difference between the
two layer hybrid strains using t-test. The difference between each
hybrid strain and the standard reported on its manual was also tested
using single sample t-test. The weekly H.D egg production from 5%
production for each farm was regressed on time according to wood
(1967) lactation curve equation:-
Y= a x b . e x p (-cx)
Where:-
Y = egg production. a = initial egg production.
x = age in week. b = rate of increase to the peak.
c = rate of decrease from the peak.
No significant difference between the two hybrid strains and their
standard values were found in most of the production traits.
There is a significant difference (P<0,05) in mortality rate up to the
end of production in each hybrid strain when compared to its standard
manual. Hyline W98 feed consumption was significantly (P<0,05)
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lower than that of Lohmman LSL where as feed conversion ratio ofHyline W98 was significantly (P<0,05) improved. Egg weight of
Lohmman LSL was significantly (P<0,05) higher than that of Hyline
W98 while the later has longer production cycle. Mortality rate of
Hyline W98 was higher during the period from first lay up to the end
of production than that of lohmman LSL but the difference was not
significant.
The components of the production curve were examined for
significance of different between the two hybrid strains using t-test.
The components of the production curve were:-
a = age of first egg.
b = rate of increase of curve to peak.
c = rate of decrease of curve from the peak.
b/c = week of the peak.
b + 1 lin c = persistency of the peak of the curve.
No significant differences between the two hybrid strains and their
corresponding standard values in production curve parameters.
The study results concluded that the formula of wood (1967) could be
precisely fitted the data of the egg production and therefor it can be
used for the prediction and evaluation of egg production.
The study also concluded that the two hybrid strains perform under
Sudan conditions were similar to their standard manuals which
indicating that these hybrid strains have a good adaptability to the
tropical environments.
Further more, there are no differences between the two hybrid strains
in most of the traits examined.
