PSI-1 Effects of Pre-Transit Diets and Road Transportation on Plasma, Salivary Cortisol, and Rumen Environment of Beef Heifers
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AbstractIncreased salivary cortisol in cattle may be detrimental to rumen bacterial diversity. Effects of transportation and diet before transportation on plasma and salivary cortisol and on rumen conditions of 20 ruminal-cannulated heifers (346 16 kg BW) were evaluated. Heifers were fed ad libitum 40% Sorghum Sudan grass hay and 60% commercial pellet (64% TDN, 12.4% CP, DM basis) for 13 d before study initiation. Heifers were randomly assigned to a 2 2 factorial arrangement of 8-h transportation (TR) vs. no transportation (NT) and 100% Sorghum Sudan grass hay (HAY) vs. 30% hay and 70% pellets (H+P) fed ad libitum for 3 d before transportation. All groups were fasted during the 8-h transit period. Upon feedlot arrival at 8 h, cattle were fasted an additional 4 h. At 12 h, cattle were fed 30% wheat hay and 70% commercial feed (69% TDN, 16.6% CP, DM basis). Blood and ruminal fluid were sampled at 0, 8, 12, 24, 28 and 72 h. No diet transport interactions were observed for any variable. Plasma cortisol was decreased for HAY vs. H+P heifers at 72 h (P > 0.05, diet hour). Rumen pH and total volatile fatty acid concentrations did not differ between groups. Molar percentages of acetate increased, molar percentages of propionate decreased, and acetate-to-propionate ratios increased at 0 and 12 h for HAY compared to H+P (P > 0.05, diet hour). At 0 h, molar percentages of butyrate were less for HAY vs. H+P (P > 0.05, diet hour). Bacterial phyla richness was decreased for NT/HAY compared to NT/H+P and was increased for TR/HAY compared to TR/H+P heifers (P > 0.05, diet transport). Proteobacteria relative abundances were less at 0 h for heifers fed HAY vs H+P (P > 0.05, diet hour). Genera evenness was increased at 8 h for TR compared to NT cattle (P > 0.05, transport hour). Genera Shannon-wiener indices were greater at 0 and 8 h for cattle consuming HAY compared to H+P (P > 0.05, diet hour). Genera richness was increased at 0 h for cattle fed HAY compared to H+P (P > 0.05, diet hour). Prevotella relative abundances were less for cattle fed HAY compared to H+P at 0 and 8 h (P > 0.05, diet hour). In summary, due to negligible response to transportation, salivary cortisol effect on bacteria population and diversity were presumably minimal.
