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Prepartum light shifting circadian rhythm disruption did not affect amount of muscle and adipose mobilized in transition dairy cows.

C. J. McCabe

Events

06-23-2020

Abstract:

173
Prepartum light shifting circadian rhythm disruption did not affect amount of muscle and adipose mobilized in transition dairy cows.
C. J. McCabe*, A. Suarez-Trujillo, T. M. Casey, J. P. Boerman. Purdue University, Department of Animal Sciences West Lafayette, IN.

Circadian clocks function to maintain homeostasis by coordinating internal physiology to the external environment through the generation of 24 h rhythms. Circadian clocks are integrated with the metabolic system and disruption of clocks by altering timing of external cues affects metabolism, with long-term disruption associated with development of diseases in humans and rodents. During the periparturient period, dairy cattle are often in a negative energy balance and accommodate for nutrient gaps by mobilizing stores from adipose and muscle. The objective of this study was to determine the effect of exposure to chronic light-dark cycle phase shifts during the nonlactating prepartum period on tissue mobilization postpartum. Multiparous Holstein cows (n = 16) were exposed to 16 h of light and 8 h of dark (CON; n = 8) or phase shifting (PS; n = 8) of the start of the light cycle forward 6 h every 3 d beginning 35 d before expected calving (BEC). Following calving both treatments were exposed to control lighting through 60 DIM. Longissimus dorsi and backfat ultrasounds measured muscle and backfat depth at 35, 21, and 7 d BEC and 0, 10, 21, 30, and 60 DIM. Cows lost muscle mass from 35 d BEC to 60 DIM (4.02 vs. 3.01 cm; P < 0.01), with no differences between treatments (P > 0.05). Muscle depth at 35 d BEC positively correlated to the amount of muscle mobilized over the study (P = 0.002; R2 = 0.50). Backfat depth was less between 35 d BEC and 30 and 60 DIM (P < 0.05). Creatinine, 3-methylhistidine, and NEFA, measured in plasma samples taken on ultrasound dates and 28, 14 d BEC and 7, 14 DIM as indicators of total muscle mass, and muscle and adipose mobilized, respectively, were not different between treatment (P > 0.05), but NEFA increased and creatinine decreased for all cows between pre and postpartum periods (P < 0.01). In this study, circadian clock disruptions in the prepartum did not affect the quantity of tissue mobilized nor blood metabolites during the dairy cow periparturient period.

Keywords: circadian rhythm, ultrasound, tissue mobilization.