5-hydroxytryptophan mitigation of ergot alkaloid-induced vasoconstriction in pregnant ewes on blood metabolites, placental and fetal growth, and maternal microbiome.

Abstract

Twin bearing ewes were randomly assigned and individually fed one of three treatments: 1) total mixed ration (TMR) (CON, n = 10), 2) 5-hydroxytryptophan (5-HTP, 2.5 mg/kg BW) and toxic tall fescue seed containing 1.77 mg ewe^-1d^-1 ergovaline/ergovalinine (E+) in TMR (E⁺/5-HTP, n = 10), or 3) E+ tall fescue seed in TMR (E⁺, n = 10) from gestational day (gd) 86 to 110. At terminal necropsy (gd111), placental and fetal growth measurements were collected and analyzed as a completely randomized design. Maternal blood samples were collected over time and samples of rumen microbiome and fetal blood were collected at necropsy. Feeding E+ fescue seed reduced (P < 0.05) total fetal weight per ewe by 20% compared to CON with E⁺/5-HTP being intermediate. Supplementation of 5-HTP increased (P < 0.05) circulating 5-HTP and 5-HIAA but not 5-HT. Ergovaline was detected in the maternal and fetal blood samples collected at necropsy from E⁺ and E⁺/5-HTP fed ewes. Serum non-esterified fatty acid concentrations were greater (P < 0.05) in CON at the end of the study; however, serum glucose and plasma insulin concentrations did not differ. Individual caruncle and cotyledon weights differed by treatment and placentome type. Ewe rumen microbiome diversity was greater with E⁺/5-HTP compared to E⁺. Feeding E⁺ tall fescue seed to ewes from gd 86 to 110 reduced fetal growth; however, supplementation of 5-HTP partially mitigated the negative effects of E⁺. Further research is needed at higher dose levels of 5-HTP to fully mitigate the negative effects of E+ on fetal growth.