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A total of 713
first lactation records of Sahiwal cows maintained at
National Dairy Research Institute, Karnal over a period of
49 years (1961-2009) were analyzes to study the effect of
non-genetic factors (seasons, periods and age groups) on
test day milk yields at monthly interval (6th, 35th, 65th,
95th,125th,155th,185th, 215th, 245thand 275th days) and
first lactation 305-day milk yield (FL305DMY). The overall
least squares mean for first lactation 305-day milk yield
and ten test day milk yields (6th, 35th, 65th, 95th, 125th,
155th, 185th, 215th, 245th and 275th day) were 1834.87 ±
36.89, 4.88 ± 0.14, 7.84 ± 0.16, 7.75 ± 0.15, 7.38± 0.14,
7.01 ± 0.14, 6.54 ± 0.13, 6.34 ± 0.13, 6.15 ± 0.13, 6.07 ±
0.13 and 5.73 ± 0.12 kg, respectively. The season and period
of calving was having significant influence on most of the
milk yields, while age groups had significant effect on some
of the traits.
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