Prepartum daylight exposure increases serum calcium concentrations in dairy cows at the onset of lactation.

Özcelik, Ranya; Bruckmaier, Rupert; Hernandez Castellano, Lorenzo Enrique (2017). Prepartum daylight exposure increases serum calcium concentrations in dairy cows at the onset of lactation. Journal of animal science, 95(10), pp. 4440-4447. American Society of Animal Science 10.2527/jas2017.1834

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In dairy cows, hypocalcemia is caused by the sudden calcium demand by the mammary gland at the onset of lactation. Calcitriol (1,25-dihydroxy vitamin D; 1,25-VitD) increases the intestinal calcium absorption and the renal calcium reabsorption. Daylight contributes to the formation of 1,25-VitD, as it transforms 7-dehydrocholesterol into cholecalciferol, a 1,25-VitD precursor. Calving pens are usually set in quiet places where cows can stay calm and relaxed before parturition. However, those pens often have poor lighting conditions and therefore cows may become vitamin D deficient because of inadequate daylight exposure. Therefore, we have tested the hypothesis that direct daylight exposure supports the synthesis of 1,25-VitD and consequently attenuates the decline of calcium concentrations at parturition. Twenty Holstein dairy cows were randomly assigned to 2 experimental groups (daylight group, DL; and control group). Beginning on d -10 before expected parturition, both groups were placed in a standard indoor calving pen from 1700 h to 800 h. From 800 h to 1700 h cows from the DL group were moved into a contiguous open pen with direct access to daylight whereas controls remained at the standard indoor calving pen. After parturition both groups were permanently placed in an indoor calving pen until the end of the experimental period (d 30 postpartum). Blood samples were collected daily from d -10 prior to expected parturition through d 7 postpartum with an additional sample on d 30 postpartum. Milk yield was recorded at each milking during the whole experimental period. In the DL group, 25-hydroxyvitamin D (25-VitD), 1,25-VitD and total calcium concentrations around parturition were higher than in the controls. Higher parathyroid hormone concentrations were observed in the control group compared to the DL group at parturition. Pyridinoline concentrations did not differ between groups on d 1, and therefore it is assumed that the intensity of calcium transfer from the bones to the bloodstream was not affected by the increased daylight exposure. The measured plasma metabolites (β-hydroxybutyrate, fatty acids and glucose) as well as milk yield were not affected by the increased daylight exposure. In conclusion, the increased daylight exposure before parturition increased 25-VitD and 1,25-VitD concentrations, preventing a considerable decline of total calcium concentrations around parturition.

Item Type:	Journal Article (Original Article)
Division/Institute:	05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Veterinary Public Health Institute 05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Veterinary Physiology 05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH)
UniBE Contributor:	Özcelik, Ranya, Bruckmaier, Rupert, Hernandez Castellano, Lorenzo Enrique
Subjects:	500 Science > 590 Animals (Zoology) 600 Technology > 630 Agriculture
ISSN:	0021-8812
Publisher:	American Society of Animal Science
Language:	English
Submitter:	Hélène Elisabeth Meier
Date Deposited:	19 Jun 2018 16:09
Last Modified:	05 Dec 2022 15:12
Publisher DOI:	10.2527/jas2017.1834
PubMed ID:	29108038
URI:	https://boris.unibe.ch/id/eprint/114681