Threshold dose of 1,25-dihydroxycholecalciferol-glycosides on mineral metabolism and circulating serotonin and dopamine in bovines

Abstract

Plant-derived 1,25(OH)₂D₃-glycosides modulate calcium (Ca) and phosphorus (P) metabolism, but the safety of sustained oral supplementation in cattle remains unclear. The objective of this study was to establish a safe upper limit for dietary supplementation of 1,25(OH)₂D₃-glycosides in steers and to assess its impact on mineral and neurotransmitters metabolism. Six Holstein steers (452 ± 61.5 kg) were used in a replicated 3 × 3 Latin Square design. Treatments consisted of oral administration of 1,25(OH)₂D₃-glycosides at doses of 0, 0.2, and 0.4 µg/kg body weight (BW) for five consecutive days. Blood samples were collected prior to the initiation of treatment, as well as immediately before (0 h) and at 3, 6, 12, 24, 48, 72, 96, and 168 hours following the final dose on day 5. The serum Ca remained (P < 0.001) elevated up to 72 h and 96 h following the final administration of 1,25(OH)₂D₃-glycoside at doses of 0.2 µg/kg BW and 0.4 µg/kg BW, respectively. In contrast, serum P concentrations remained significantly elevated (P = 0.001) for more than 168 hours post-treatment, regardless of the administered dose. No significant effects were observed on serum alkaline phosphatase (ALP) activity (P = 0.298), parathyroid hormone (PTH; P = 0.183) concentrations, or circulating serotonin (P = 0.428) and dopamine (P = 0.846). Additionally, no clinical signs consistent with vitamin D intoxication were observed. Oral supplementation with 1,25(OH)₂D₃-glycosides at doses up to 0.4 µg/kg BW for 5 days induces a sustained elevation in serum Ca and P concentrations, more evidently at higher dosages, without altering serum concentration of ALP, PTH, serotonin or dopamine indicating that 0.4 µg/kg BW dosage might be close to the upper threshold of 1,25(OH)₂D₃-glycosides in cattle while 0.2 µg/kg BW can be considered as safe.