|Author:||Joseph J Klopfenstein|
|Clinic:||Oregon State College of Veterinary Madicine|
|City, State, ZIP:||Corvallis, OR 97331|
Jean A Hall, DVM Ph.D
Joseph J. Klopfenstein, DVM
1Carlson College of Veterinary Medicine, Oregon State University, Corvallis, Oregon 97331
Our goal is to prevent diseases in cattle by feeding selenium (Se) biofortified forages to optimize immune function. Major parts of the US, including Oregon, are deficient in Se. Regional differences are reflected in the Se content of forages and in whole-blood Se concentrations in cattle consuming these forages. In plants (and in yeast), Se is incorporated into methionine as selenomethionine, and when forage is consumed by cattle, Se from selenomethionine is incorporated into selenoproteins, whose functions range from antioxidant, anti-inflammatory, and detoxification to thyroid hormone activation. We propose to demonstrate that supplementing organic Se-yeast during pregnancy, which has similar effects to Se-enriched forage, increases cattle whole-blood Se concentrations, and alters blood neutrophil expression of selenoproteins and other genes involved in innate immunity. Our study involved calves born to cows supplemented during different stages of pregnancy. We will assess calves for passive transfer of immunoglobulins, for duration of passive immunity, and for calf performance from birth through weaning. Pregnant beef cows were supplemented with Se-yeast at different stages of pregnancy, i.e., fetal development, to enhance proliferation of myogenic precursor cells and improve the efficiency of lean growth and pre-weaning calf performance. We will correlate postnatal whole-blood Se concentrations and muscle gene expression.
Cows were assigned to one of four groups at conception (control, and groups 1, 2, and 3 corresponding to trimester of Se-treatment), using a randomized complete block design. These are Angus and Angus-cross cows that have calved at least once previously; 15 to 25 cows/group. Ear tags were used to identify cows. The cows are located at the Oregon State University Soap Creek ranch, Corvallis, OR. Routine farm management practices, including vaccinations and deworming, were the same for all treatment groups. Cows received Se-supplementation during their corresponding pregnancy trimester using boluses of Se-yeast administered orally with a balling gun. When not receiving Se-yeast, cows received a mineral supplement containing 120 mg/kg Se (US FDA regulations) from Na selenite.
Newborn calves were identified using ear tags. Body weights of all calves were recorded within 2 hours of calving. Blood samples were collected from cows at baseline, before and after Se treatment, and at parturition to measure whole-blood Se concentrations. Whole-blood was similarly collected from calves at birth to measure IgG and Se concentrations. Selenium concentrations in whole blood will be determined by a commercial laboratory (Utah Veterinary Diagnostic Laboratory, Logan, UT) using ICP-MS assay.
Passive transfer of immunoglobulins will be assessed within ± 3 days of birth, and duration of passive immunity will be determined at 8 weeks. Health records will be maintained to monitor health status during the pre-weaning period (e.g., days off feed, fever, respiratory disease, diarrhea, abscess, pink eye, etc.), treatments administered, and response to treatment.
Data is still being collected and compiled, but for this presentation we will have results for birth weight, 2 month weight, IgG levels at birth and at 8 weeks of age. We should also have results on blood selenium levels for cows during supplementation and at parturition and for calves at birth and at 8 weeks of age.
Selenium and its effect on the immune system of cattle is well documented. We hypothesize that supplemental selenium by feeding Se-yeast boluses to pregnant beef cows in each of three trimesters will alter cow and calf performance measures, IgG concentration and blood-Se concentrations at parturition.