Effect of feeding corn, hull-less or hulled barley on fermentation by mixed cultures of ruminal microorganisms.

Increased demands for corn grain warrant the evaluation of alternative grain types for ruminant production systems. This study was conducted to determine the effects of hulled and hull-less barley (Hordeum vulgare L.) cultivars compared with corn (Zea mays L.) as an alternative grain type on fermentation in cultures of mixed ruminal microorganisms. Three continuous fermentors were fed 14 g of dry feed per day (divided equally between 2 feedings) consisting of alfalfa (Medicago sativa L.) hay pellets (40% of dry matter) and 1) ground corn, 2) hulled barley, or 3) hull-less barley concentrate (60% of dry matter) in each fermentor. Following an adaptation period of 5 d, culture samples were taken at 2 h after the morning feeding on d 6, 7, and 8 of each period for analysis. A second run of the fermentors followed the same treatment sequence to provide replication. Culture pH was reduced with corn (5.55) and did not differ between barley cultivars (average pH 5.89). Total volatile fatty acid concentration and acetate to propionate ratio were not different across grain type or barley cultivar with the exception of greater total volatile fatty acid concentrations with hull-less barley. Corn produced less methane (14.6 mmol/d) and ammonia-N (7.3 mg/100 mL) compared with barley (33.1 mmol/d and 22 mg/100 mL, respectively); methane was greater with hull-less barley but ammonia-N concentration was similar between the 2 barley cultivars. Hull-less barley had greater digestibility compared with hulled barley, and corn had reduced digestibility compared with barley. Concentrations of C18:0 were greater and those of C18:1 and C18:2 lesser in cultures fed hulled and hull-less barley compared with corn. Our data indicate that grain type and barley cultivar have an impact on ruminal fermentation. The lesser starch concentration of barley minimized the drop in culture pH and improved digestibility.