Before giving birth, cows have daily rhythms in body temperature and key hormones, but after birth, these daily patterns disappear, no matter if their light schedule was changed or not.

Scientific Claim

Circadian rhythms of core body temperature and multiple hormones (cortisol, progesterone, serotonin, melatonin, growth hormone) are detectable in late-pregnant dairy cows under control lighting, but are diminished or lost after calving in both control and phase-shifted groups.

Original Statement

“In the PP, circadian rhythmicity was lost or diminished for all hormones and body temperature in both treatments”

From study:Effect of circadian system disruption on the concentration and daily oscillations of cortisol, progesterone, melatonin, serotonin, growth hormone, and core body temperature in periparturient dairy cattle.

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 claim uses descriptive language matching the abstract. No causal verbs are used, and the study design cannot confirm mechanisms, so 'association' is appropriate.

Evidence from Studies

Supporting (1)

Effect of circadian system disruption on the concentration and daily oscillations of cortisol, progesterone, melatonin, serotonin, growth hormone, and core body temperature in periparturient dairy cattle.

Cohort Study

Animal

2022 Mar

Before giving birth, cows have daily body temperature and hormone cycles like a biological clock, but after giving birth, those daily rhythms disappear—even if their light schedule was changed before birth.

Contradicting (0)

No contradicting evidence found

Source Study

Effect of circadian system disruption on the concentration and daily oscillations of cortisol, progesterone, melatonin, serotonin, growth hormone, and core body temperature in periparturient dairy cattle.

Score: 10

DOI: 10.3168/jds.2021-20691

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