When cows are kept on a changing schedule of light and dark before giving birth, their bodies produce less serotonin and more melatonin, which might affect how their internal clocks work.
Scientific Claim
Chronic disruption of the light-dark cycle in late-pregnant, nonlactating dairy cows is associated with lower serotonin concentrations and higher melatonin concentrations across the prepartum period, suggesting circadian disruption alters neuroendocrine signaling.
Original Statement
“overall level of 5HT was lower and MEL higher in PS cows across days sampled”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design cannot support claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The abstract uses observational language ('was lower', 'was higher') and does not claim causation. The study design is observational with no randomization confirmed, so 'association' is the correct verb strength.
Evidence from Studies
Supporting (1)
When cows were kept on a changing schedule of light and dark, their bodies produced less serotonin and more melatonin than normal, which means their internal body clock got messed up and affected their brain chemicals.