Evaluation of Alterations in Uterine Blood Flow using Doppler Ultrasonography in Pregnant, Genotyped Beef Cows and Heifers Consuming Endophyte-Infected Tall Fescue Seeds and Supplemented with Rumen-Protected Niacin

Fescue toxicity is a nutritional-related disease generated in a forage-based beef herd exposed to ergot alkaloids (i.e. ergovaline) present in endophyte-infected tall fescue that produces important economic losses. The combination of a genetic test for susceptibility to fescue toxicity and supplementation with rumen-protected niacin could potentially reduce the toxic effects of ergovaline on beef cow and heifers' reproductive performance during mid-gestation by improving uterine blood flow. Our main objective was to use color Doppler ultrasonography to evaluate the occurrence of any alteration in uterine arterial blood flow in pregnant, genotyped beef cows and heifers exposed to endophyte-infected tall fescue seeds and supplemented with rumen-protected niacin. We hypothesize that genetically-tested susceptible control beef cows will have narrower uterine arteries and decrease blood flow as compared to tolerant cows that received rumen-protected niacin. Rumen-protected niacin was selected for this study due to its well-known effect as a vasodilator. Therefore, it might help cope with blood vessel constriction generated by ergovaline present in endophyte-infected tall fescue seeds. Results showed the negative effect of exposure to ergovaline in the uterine blood flow of pregnant beef cattle through an increase in the resistivity index. No Doppler parameters detected positive effects of genetic and nutritional treatments