Hybrid rye as potential alternative cereal in starter diets: effect of inclusion level and physical form on rumen bacterial community and fermentation efficiency in vitro

The higher drought tolerance, lower nutrient requirements and ergot resistance make hybrid rye an attractive economic alternative among cereals for calf feeding. As hybrid rye is a novel ingredient for calf diets, this study aimed to evaluate the effects of its inclusion level (25 and 46%) and physical form (ground versus rolled) as replacement for wheat in total mixed rations (TMR) for weaned calves on ruminal organic matter (OM) degradation, bacterial community and fermentation efficiency in vitro using the rumen simulation technique. Five TMR (n = 6) for calves were compared. Hybrid rye partially (i.e., 54%) or completely (i.e., 100%) replaced wheat, either in ground or rolled form. Replacing wheat by hybrid rye led to a similar degradation of OM and NDF among TMR irrespective of the inclusion level and physical form of hybrid rye. The TMR with 25 and 46% hybrid rye contained increasing amounts of fructans and β-glucans, which were readily fermented. Profiles of ruminal pH and total short-chain fatty acid (SCFA) production indicated similar fermentation intensity among wheat and hybrid rye-based TMR during the first 12 hours of fermentation. The fermentation efficiency for SCFA, including acetate, propionate and butyrate, was higher with rolled hybrid rye and 46% ground hybrid rye TMR (P < 0.05). β-diversity analysis indicated that the 46% ground hybrid rye TMR altered the bacterial community the most by decreasing the abundance of hydrogen-producers and -utilizers and propionate-producing genera and altering the abundance of lactic acid producers (P < 0.05). Positive correlations between Succinivirionaceae UCG-001 and propionate, as well as between Shuttleworthia and butyrate concentrations, confirmed relationships between bacterial abundance and SCFA production. Alpha-diversity (Shannon) was higher with ground compared to rolled hybrid rye (P < 0.05). In conclusion, our in vitro findings demonstrated that hybrid rye could completely replace wheat in the TMR without negatively impacting rumen nutrient degradation and fermentation irrespective of physical form and despite significant shifts in rumen microbiome composition over time. Future research should verify the results for ruminal fermentation and calf growth in vivo.

KWS SAAT SE & Co. KGaA
University of Veterinary and Animal Sciences
Universität für Bodenkultur