Growth and reproductive responses of heifers consuming endophyte-infected tall fescue seed with or without sodium bicarbonate supplementation

Abstract

The objective of this study was to evaluate growth and reproductive characteristics of heifers consuming endophyte-infected (EI) tall fescue seed in a feedlot setting with or without sodium bicarbonate supplementation. A total of 48 commercial beef heifers (±1.2 mo; BW = 268 ± 24 kg) were used in an 84-d experiment. Animals were blocked by BW and assigned to treatments. Treatments were arranged in a 2 × 2 factorial design with heifers fed either EI fescue seed with 1,320 μg/kg total ergot alkaloid without sodium bicarbonate (E+B−) or with sodium bicarbonate (E+B+), or EI fescue seed with 11 μg/kg total ergot alkaloid without sodium bicarbonate (E−B−) or with sodium bicarbonate (E−B+). Data were analyzed utilizing R statistical software (R Foundation for Statistical Computing). At d 56, there tended to be an interaction between seed type and bicarbonate supplementation for G:F (P = 0.084) and ADG (P = 0.071). Neither fescue seed type nor bicarbonate supplementation affected DMI at d 56 (P ≥ 0.739). By d 84, bicarbonate supplementation tended to decrease ADG (P = 0.087), and intake of whole seed from E+ fescue tended to decrease DMI (P = 0.074). Prolactin concentrations tended to be lower in heifers consuming E+ when compared with heifers consuming E− on d 56 (P = 0.09). However, there was no difference in overall prolactin concentrations over the full experimental period (P > 0.05). The observations in this study failed to show any noteworthy abnormalities in growth and reproductive performance associated with feeding a whole E+ fescue seed with 1,320 μg/kg total ergot alkaloid, and as such, there was little positive influence of bicarbonate supplementation on the productive outcomes assessed. The lack of productive performance responses to endophyte-infected fescue seed or to sodium bicarbonate supplementation could be due to low power, whole-seed feeding, a corn-silage basal diet, the lack of thermal stress during the feeding period, or other experimental design limitations.