This study was aimed to assess the efficacy of oral treatment of commercial product of vitamin D3 (VITOL-80 C ORAL®, Interchemie, Holland) in growing Najdi sheep suffering from musculoskeletal illness due to vitamin D3 deficiency in Basra province, Iraq. Using a Najdi sheep model bred in Iraq, here we focused on measuring the serum levels of total vitamin D3, calcium, phosphorus, parathyroid hormone (PTH), alkaline phosphatase (ALP) and alanine aminotransferase (ALT) as well as complete blood count (CBC) and clinical examinations pre and post-treatment with VITOL-80 C ORAL®. No significant changes (P > 0.05) of the vitamin D status were recorded in Najdi sheep with vitamin D3 deficiency post treatment with (VITOL-80 C ORAL®). However, a sharp (P < 0.0001) decline of the total serum vitamin D3 concentration were observed in those Najdi sheep per-administration (21.95 ± 1.82 ng/ml) and postadministration (22.29 ± 1.34 ng/ml) of vitamins therapy contrast to control healthy Najdi sheep (89.75 ± 6.84 ng/ml). An interaction between vitamin D3 status and the serum concentrations of calcium/phosphorus, PTH, ALP and ALT was observed. With vitamin D3-deficient Najdi sheep; values of CBC, and calcium/phosphorus concentrations were lower while PTH, ALP and ALT were higher than the healthy control Najdi sheep; thus, no significant changes (P > 0.05) of these values were recorded post treatment of (VITOL-80 C ORAL®). In conclusion, vitamin D3 deficiency threats the health of local Najdi sheep and has a potential role through suppressing their immunity. Oral administration of the commercial product as a source of vitamin D3 is not effective suggesting involvement of vitamin D receptors (VDR) and/or dysfunction of liver and kidneys.