Chronic prepartum light-dark phase shifts in cattle disrupt circadian clocks, decrease insulin sensitivity and...

Area of Science:

• Animal Science
• Metabolic Physiology
• Chronobiology

Background:

• Circadian and metabolic systems are closely interconnected.
• Disrupting the circadian system may impact crucial physiological processes like glucose homeostasis and mammary development.

Purpose of the Study:

• To investigate the effect of circadian system disruption on glucose homeostasis and mammary development in periparturient dairy cows.
• To determine if chronic light-dark cycle phase shifts impact mammary gland development and insulin sensitivity.

Main Methods:

• Holstein cows were subjected to light-dark cycle phase shifts (PS) or constant conditions (CON) starting 35 days before expected calving.
• Mammary biopsies and intravenous glucose tolerance tests were performed prepartum and postpartum.
• Measurements included histological analysis, blood glucose, insulin, β-hydroxybutyrate, and nonesterified fatty acids.

Main Results:

• Phase shifting decreased mammary alveolar development and epithelial cell proliferation prepartum.
• Insulin area under the curve was elevated in phase-shifted cows prepartum and postpartum.
• Milk production was reduced in phase-shifted cows through 60 days in milk.

Conclusions:

• Chronic circadian disruption via light-dark phase shifts negatively affects mammary development in late gestation.
• Circadian disruption leads to increased insulin resistance in periparturient dairy cows.
• These effects may contribute to reduced milk yield in affected cows.