Potential for live yeast culture to enhance nitrate mitigation of methanogenesis in Jersey dairy cattle

Abstract Text: Concern over the environmental impact of dairy production has stimulated research to decrease enteric CH₄ production.  One approach is feeding the electron acceptor, NO₃, to be reduced by bacteria such as the selenomonads, thus outcompeting methanogens for aqueous H₂. We hypothesized that a live yeast culture, [Yea-Sacc® (YS); Saccharomyces cerevisiae; Alltech, Inc.] would stimulate the reduction of NO₃ completely to NH₃ and thereby improve the ratio of CH₄ emission:energy-corrected milk production while decreasing blood methemoglobin concentration. Twelve lactating Jersey cows (8 multiparous and non-cannulated; 4 primiparous and ruminally cannulated) were used in a replicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments.  Cattle were fed diets either containing 1.5% NO₃ (from calcium nitrate) after an adjustment period or a control diet (containing urea isonitrogenous to NO₃) and were given a top-dress of ground corn without or with YS.  All non-cannulated cows were spot-measured for CH₄ emission by mouth using GreenFeed (C-Lock Inc., Rapid City, SD). The main effect of NO₃ decreased (P < 0.01) methane 17% but decreased (P < 0.01) DMI by 10% (from 19.8 to 17.8 kg/d) such that CH₄:DMI tended (P = 0.14) to decrease by 8%. Milk and milkfat production were not affected, but NO₃ decreased (P < 0.01) milk protein from 758 to 689 g/d. Ruminal pH was decreased more after feeding diets without NO₃, and acetate:propionate was greater for cows fed NO₃, especially when combined with YS (interaction, P = 0.01). Others who have noted lower palatability and lower consumption per meal, which is consistent with our observations. Methemoglobin was higher (P = 0.01) for cattle fed NO₃ than those fed urea but were still low (1.5 vs 0.5% and only once exceeded 5%), documenting minimal risk for NO₂ accumulation at our feeding levels of NO₃. Although neither apparent OM nor NDF digestibilities were affected (P > 0.15), apparent N digestibility had an interaction (P = 0.06) such that, compared with those fed either diet without NO₃, N absorption was slightly higher for those fed NO₃ without YS but slightly lower for those fed NO₃ with YS. Under the conditions of this study, NO₃ did mitigate ruminal methanogenesis but was not particularly effective after considering that it depressed DMI and milk protein. Based on few interactions detected, YS had a minimal role in attenuating either of these responses.

Keywords:

Nitrate

Live Yeast Culture

Methane