This study evaluated the effects of
melatonin administration 60 days prior to
expect calving (drying-off period) on milk yield
during the next lactation. Sixty dairy cows were
treated with subcutaneous melatonin implants
during summer (n=30) or winter (n=30) period.
Another 60 animals were not treated and
served as the control. There were no differences
in the average milk yield between treated and
untreated animals (44.5±3.7 and 44.8±5.0 kg/day
for melatonin and control cows, respectively).
There was an effect of season with a higher
winter milk yield than in summer (43.8±5.0
and 47.1±3.0 kg/day for melatonin and control
groups, respectively). The interaction between
melatonin and season showed no significant
effect; however, during winter, milk yield
tended to be higher (P=0.06) in control cows
than in melatonin treated cows (45.3±3.7 and
49.2±3.0, respectively). This study indicates that
treatment with melatonin prior to calving did
not modify milk yield during the following
lactation. Only a tendency for a reduction
in milk yield during winter was observed in
melatonin treated cows
