Location: Livestock Behavior ResearchTitle: Exposure to chronic light-dark phase shifts during the prepartum dry period attenuates circadian rhythms, decreases blood glucose and increases milk yield in the subsequent lactation
|SUAREZ-TRUJILLO, ARIDANY - Purdue University|
|SUN, HUI - Purdue University|
|HUFF, KATELYN - Purdue University|
|CUMMINGS, SHELBY - Purdue University|
|FRANCO, JACKELINE - Purdue University|
|STECKLER, TABITHA - Purdue University|
|BOERMAN, JACQUELYN - Purdue University|
|WERNET, GRACE - Purdue University|
|TOWNSEND, JONATHAN - Purdue University|
|GROTT, MICHAEL - Purdue University|
|PLAUT, KAREN - Purdue University|
|CASEY, THERESA - Purdue University|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2020
Publication Date: 3/1/2020
Citation: Suarez-Trujillo, A., Sun, H., Huff, K., Cummings, S., Franco, J., Steckler, T., Boerman, J., Wernet, G., Townsend, J., Grott, M., Johnson, J.S., Plaut, K., Casey, T. 2020. Exposure to chronic light-dark phase shifts during the prepartum dry period attenuates circadian rhythms, decreases blood glucose and increases milk yield in the subsequent lactation. Journal of Dairy Science. https://doi.org/10.3168/jds.2019-16980.
Interpretive Summary: When dairy cows transition from pregnancy to lactation they often enter a state of negative energy balance when energy intake cannot keep up with lactation demand. If a cow cannot successfully adapt to this stress, it can result in disease states (i.e., milk fever and ketosis) and an overall reduction in productivity. Previous research shows that photoperiod is an important factor that determines how a cow adapts to this stress. Therefore, the study objective was to determine the effects of exposure to chronic shifts of the light-dark cycle, during the last 5 weeks of the prepartum dry period on 1) circadian rhythms of body temperature and plasma melatonin and behavior (feed intake and activity); 2) blood metabolites; and 3) milk yield and milk composition. We hypothesized that disruption of the circadian timing system in dairy cows during the dry period would cause metabolic disturbances affecting cattle health and milk production. Results from this study indicated that chronic shifts of the light-dark cycle impacted cow behavior, reduced blood glucose, attenuated the circadian rhythms of core body temperature and melatonin, and increased milk production. These findings suggest that less accentuated variation in physiological rhythms may facilitate the onset of milk production.
Technical Abstract: Maintaining metabolic balance is a key factor in the health of dairy cattle during the transition from pregnancy to lactation. The circadian timing system (CTS) regulates metabolic homeostasis. We hypothesized that disruption of the cow’s CTS by exposure to chronic light-dark phase shifts (PS) during the prepartum dry period causes metabolic disturbances and would be associated with reduced milk production in the subsequent lactation. The objective was to determine the effect of exposure to chronic light-dark PS during the last 5 weeks of the dry period on core body temperature, melatonin, periparturient blood glucose, ß-hydroxybutyric acid (BHBA) and non-esterified fatty acid (NEFA) levels and milk production. Multiparous cows were moved to tie stalls at 5 wk before expected calving (BEC) and assigned to control (C; n=16) or PS (n=16) treatments. C cows were exposed to 16h L: 8h D; PS cows were exposed to the same photoperiod, however the LD cycle was shifted 6h every 3d until parturition. Resting behavior and feed intake were recorded. Core body temperature was recorded vaginally for 48 h at 23 d and 9 d BEC using calibrated data loggers. Blood melatonin, glucose, BHBA and NEFA were measured during pre and postpartum periods. Milk yield and composition was measured through 60 DIM. Treatment did not affect feed intake or body condition. Cosine fit analysis of 24 h core body temperature and circulating melatonin indicated a significant (P<0.05) attenuation of circadian rhythms of PS treatment. Cows in PS had lower rest consolidation indicated by more total resting time, but shorter resting period durations (P<0.05). Treatment had an overall effect on decreasing blood glucose by 4 mg/dL (P<0.05), but BHBA and NEFA were not different. Milk yield and milk fat yield were higher in PS animals (P<0.04). Attenuation of circadian rhythms of core body temperature, melatonin and rest-activity behavior during the prepartum dry period was associated with increased milk fat and milk yield, despite decreased blood glucose pre and post-partum. Less accentuated variation in physiological rhythms may facilitate onset of lactogenesis.