Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2000
Publication Date: N/A
Interpretive Summary: Vitamin D was added to the drinking water of turkeys which had been treated with a compound known to mimic the physical changes caused by stress. This compound was previously shown to cause turkeys to become susceptible to infection with small numbers of bacteria which would not usually cause any harm. Vitamin D had no effect when the turkeys were treated with the compound a single time. However, when turkeys were treated with the compound at the age of 5 weeks, and again at the age of 12 weeks, vitamin D protected the turkeys from disease. The ability of vitamin D to improve disease resistance of turkeys emphasizes the role of this vitamin as a hormone with wide-ranging effects in addition to its role in calcium and phosphorus metabolism. This research suggests that the ability to utilize vitamin D may be important as a selection criteria in the improvement of disease resistance in poultry stocks.
Technical Abstract: Supplemental vitamin D3 treatment was used to protect male turkeys from the immunosuppression induced by injection with dexamethasone (DEX) in two experiments. In Experiment 1, vitamin D3 was supplemented at a dosage of either 2064 IU/kg (Low) or 4128 IU/kg (High) in drinking water provided ad libitum from day 1 thru day 5 after hatch. In Experiment 2, vitamin D3 was provided at the Low dosage for the first 5 days after hatch, followed by treatment with the high dosage for 24 h before and 24 h after each stressful event which included weekly weighings and 2 DEX treatments. In both experiments, at 5 wk of age half of the birds were injected into a thigh muscle on three alternating days with 2mg/kg DEX. In Experiment 2, healthy surviving birds were grown for an additional 5 wk period, after which the DEX-treated birds were given a second series of DEX injections and were bled and necropsied 2 wk later. There were no significant effects of vitamin D3 treatment in combined GLM analysis of Experiment 1, however, when birds not treated with DEX or E.coli were compared to those both treated with DEX and E.coli, supplementation with the Low level of vitamin D3 significantly decreased TOC incidence. There were no significant effects of vitamin D3 treatment in birds treated with DEX at 5 wk of age in Experiment 2. However, when surviving birds were given a second DEX treatment at 12 wk, vitamin D3 treatment resulted in significantly lower incidence of mortality, TOC, green liver, and isolation of bacteria from tissues, lower airsacculitis scores, and lower heterophil to lymphocyte ratios than controls. Vitamin D3 treatment also tended to protect BW and relative weights of the liver, heart, spleen and bursa.