PSII-3 Effect of molasses-based block supplementation on cattle fed endophyte-infected Tall Fescue (Festuca arundinacea) seed

Abstract

Abstract Ergot-alkaloid toxicosis induces persistent vasoconstriction in cattle, interfering with efficient thermoregulation. Our objective was to evaluate impact of cooked molasses-based block supplements (MBS) on performance and physiological measurements in cattle fed ergot-containing Tall Fescue seed (TFS). Crossbred steers (n = 95; 287 ± 6.4 kg) were blocked by body weight, randomly assigned to individual indoor feeding pens and treatments consisting of: Negative Control (NC; prairie hay only); Positive Control (PC; hay plus TFS); and molasses block treatments fed hay and TFS with ad libitum access to a 38% protein block (CB); 38% protein block containing 0.3% crystalline menthol (MB); or a 38% protein block containing a proprietary blend of mannan oligosaccharide and capsaicin (AB). The TFS was mixed with molasses (9:1), and amount fed was increased gradually at 3-d intervals from 45 to 520 g/animal daily by day 42. Temperature differential between ocular conjunctiva and ear tip (ΔT) was determined weekly using thermographic imaging. Coccigeal vein diameter (CVD) was measured with Doppler ultrasound imaging (DU) on days 63 and 84. Data were analyzed as mixed models with block as a random effect and treatment, time, and treatment by time interaction as fixed effects. Block intakes did not differ among MBS treatments (P > 0.05). Cattle fed MBS had greater ADG, DMI, gain:feed (P < 0.01) compared to NC and PC. For the second half of the study MBS treatments had lower ΔT (P < 0.05). Supplementing cooked molasses-based block supplements low-moisture molasses block can improve performance and potentially enhance peripheral blood irrigation in cattle consuming ergot-infested feeds.