Forb and shrub effects on ruminal fermentation in cattle.

Abstract

One experiment involving steers fed low-quality grass diets singly and mixed with native forbs, native shrubs, or alfalfa (Medicago sativa L.) was conducted to compare the influence of these diets on ruminal fermentation. Native forbs used in our study were a 50:50 mixture of scarlet globemallow (Sphaeralcea coccinea Nutt.) and leatherleaf croton (Croton pottsii Lam.); native shrubs were a 50:50 mixture of fourwing saltbush (Atriplex canescens [Pursh.]) and mountain mahogany (Cercocarpus montanus Raf.). Neither passage rate of indigestible neutral detergent fiber nor fluid passage rate differed (P > .10) among the 4 diets. Ruminal pH did not differ (P > .10) among diets, and ruminal ammonia concentrations differed (P < .10) inconsistently among diets, depending on time after feeding. Likewise, total ruminal volatile fatty acid (VFA) concentrations did not differ (P > .10) among diets. Except for butyrate [less (P < .05) with alfalfa], proportions of individual VFA showed little difference among diets. Based on these data, adding forbs or shrubs with low-quality forage diets appears to elicit few changes in ruminal digests kinetics and fermentation patterns compared to including alfalfa hay.