THE EFFECTS OF FORM OF SELENIUM ON THE BOVINE CORPUS LUTEUM, UTERINE ENDOMETRIUM, AND DEVELOPMENT OF THE CONCEPTUS

Widespread regions of the southeast United States have soils deficient in selenium (Se), necessitating Se supplementation to cattle grazing in these areas. Adequate dietary Se is required for optimal immune function, growth, and fertility. In forages, Se is predominantly found in the organic form (OSe), which is known to increase bioavailability. However, the inorganic form (ISe) is typically found in commercial mineral mixes. We previously reported that supplementation with an isomolar 1:1 mix (MIX) of ISe (sodium selenite, Prince Se Concentrate; Prince Agri Products, Inc., Quincy, IL) and OSe (SEL-PLEX, Alltech Inc., Nicholasville, KY) increases early luteal phase concentrations of progesterone (P4) above that in cows on ISe or OSe alone. Research has demonstrated that increased early luteal phase P4 advances embryonic development. A series of experiments were performed to investigate the effect of form of supplemental Se on 1) the early bovine corpus luteum and 2) the uterine endometrium and conceptus at maternal recognition of pregnancy. The objective of Experiment 1 was to investigate the effect of form of supplemental Se on the transcriptome of the bovine corpus luteum (CL) with the goal of elucidating form of Se-regulated luteal processes affecting fertility. Results indicated that MIX-supplemented cows had increased mRNA abundance of transcripts regulating cholesterol biosynthesis and increased CL content of several immune-response transcripts compared to cows supplemented with ISe alone. These results suggest that the MIX-induced increase in early luteal phase P4 is due to an increase in cholesterol availability and that the form of dietary Se affects immune function of the CL. Experiment 2 examined the effect of form of supplemental Se on the uterine endometrium and conceptus development at maternal recognition of pregnancy. The objective was to determine changes induced by the form of supplemental Se on the bovine endometrium and developing conceptus on day 17 of pregnancy. Form of supplemental Se differentially affected the transcriptome of the uterine endometrium at maternal recognition of pregnancy, resulting in form-induced effects on embryonic length. Combining the results from both experiments, supplemental Se in the MIX versus ISe form alters the transcriptome of the bovine CL on day 7 of the estrous cycle, the transcriptome of the uterine endometrium at maternal recognition of pregnancy and advances embryonic development. In conclusion, incorporating Se into a mineral supplementation strategy as MIX is an easy transition for producers that can ultimately increase the fertility levels in their herds. An increase in fertility can cause a shift in the calving distribution, leading to more calves born earlier in the season and subsequently calves are older and heavier at weaning, ultimately leading to increased profit potential.
�� 2021 Benjamin Ryne Crites