Selenium Form-Dependent Regulation of Fertility in Cows

In cattle, increasing concentrations of early luteal phase progesterone (P4) advances development of the uterine endometrium, increases length of the conceptus at maternal recognition of pregnancy, and increases fertility. We recently reported that providing a defined, 1:1 mix of inorganic and organic forms of selenium (Se) to the diet of forage-based beef cows increases early luteal phase P4 (when compared to supplementation with the industry standard of inorganic Se alone). Given that Se-deficient soils are widespread in northwestern, northeastern and southeastern regions of the US, with supplementation of Se by free-choice mineral mixes already implemented by many producers, this strategy can/will be implemented at the production level. The switch to a 1:1 mix of inorganic and organic forms of Se represents a practical, nutritionally- based method for the producer to facilitate the increase in P4 that is known to increase fertility. This project will determine 1) the mechanism by which the provision of 1:1 blend of organic and inorganic forms of Se increases early luteal phase concentrations of P4, and 2) how this Se- mediated increase in P4 affects the uterine endometrium and development of the conceptus; investigation required before pre-breeding recommendations of the form of Se to be provided to cattle can be made. This proposal is therefore written in response to priority area A1211, Animal Reproduction of the Animal Health and Production and Animal Products program area. This