Reducing stress in sheep by feeding the seaweed Ascophyllum nodosum
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Feeding the extract of the seaweed Ascophyllum nodosum (ANOD) has been shown to mediate the response of livestock to certain environmental stressors. To determine if feeding ANOD is useful in alleviating handling and transport stress, two trials were conducted. The dose response trial was conducted to determine at which rate ANOD should be fed to obtain beneficial results. Forty-four lambs received ANOD at either 0 (control), 0.5, 1, or 2% of dry matter intake per day (approximately 0, 0.25, 0.5, and 1 g/kg of body wt per day). Sheep were administered ANOD twice daily for 14d. After 14d of supplementation, IgG and IgM antibody response to ovalbumin was reduced by ANOD. The sheep fed at the 2% rate had a narrower range of body temperature during transport than controls. The 2% rate also had lower body temperatures than the controls during times when the thermal heat index was above 80. The sheep fed the 2% rate had lower cortisol and aldosterone concentrations during walking and transport compared to the controls. Post transport, sheep supplemented at the 1 or 2% rates were less dehydrated as indicated by plasma chemistry profiles andelectrolyte concentrations. In a subsequent trial, the major components of the ANOD (fucoidan, salt, and betaine) were fed to determine which, if any, were responsible for the treatment effects in the dose response trial. After 14d supplementation, the salt and ANOD sheep had a depressed IgG and IgM antibody response to ovalbumin and an increase in white blood cell counts and lymphocyte numbers compared to controls. The ANOD sheep were generally lower in body temperature than the other treatments during transport. The ANOD and salt sheep had lower cortisol concentrations compared to controls. At the end of transport, sheep supplemented with ANOD or salt had lower electrolyte concentrations than control sheep. Supplementation with ANOD was associated with lowered body temperature; however, it also suppressed antibody titer which could leave animals susceptible to bacterial infection. The lowered antibody production is of concern and needs further study before ANOD can be recommended as a useful stress management tool.
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