Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 5/5/2008
Citation: Fellner, V., Burns, J.C., Marshall, D.S. 2008. Effects on feeding corn, hull-less or hulled barley on fermentation by mixed cultures of ruminal microorganisms. Journal of Dairy Science. 91:1936-1941. Interpretive Summary: Corn is generally the grain of choice to serve as an energy source in ruminant diets. Yet, corn is high in starch and excess starch may negatively influence animal performance. Barley, on the other hand, contains less starch than corn, but the proportion fermented in the rumen is more. This degree of fermentation provides an energy source to go with the release of nitrogen in the rumen, thereby capturing more of both energy and nitrogen for productive purposes. The use of hulless barley resulted in greater digestibility of barley grain. This study showed that barley at 48 % of the diet was equal or superior to corn as an energy source and greater than corn for diet and fiber digestibility. Barley can and should play a more important role as an energy source for ruminants.
Technical Abstract: This study was conducted to determine the effects of barley (Hordeum vulgare L.) type or corn (Zea mays L.) as a grain source on fermentation in cultures of mixed ruminal microorganisms. Three continuous fermentors were fed 14 g of dry feed per day (divided equally between two feedings) consisting of alfalfa (Medicago sativa L.) hay pellets (40% of DM) and 1) ground corn, 2) hulled barley or 3) hulless barley concentrate (60% of DM) in each of three fermentors. Following an adaptation period of 5 d culture samples were taken at 2 h after the morning feeding on day 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 (P < 0.01) with corn (5.55) and did not differ (P > 0.10) between barley types (average pH 5.89). Total VFA concentration and acetate to propionate (A:P) ratio were not different (P < 0.10) across grain source or barley type with the exception of greater (P < 0.01) total VFA concentrations with hulless barley. Corn reduced (P < 0.01) methane (14.6 mmol/d) and ammonia-N (7.3 mg/100mL) when compared with barley (33.1 mmol/d and 22 mg/100mL, respectively); methane was greater (P < 0.01) with hulless but ammonia-N concentration was similar (P> 0.10) between the two barley types. Efficiency of microbial protein synthesis was not affected (P > 0.10) by grain source but apparent digestibility was lesser (P < 0.03) with corn. Feeding hulled barley resulted in greater (P < 0.04) efficiency of microbial protein synthesis but lesser (P < 0.02) digestibility. Concentration of C18:0 was greater (P < 0.01) and that of C18:1 and C18:2 lesser (P < 0.01) in cultures fed hulled and hulless barley compared with corn. Our results show that grain source and barley type have an impact on ruminal fermentation. The lesser starch concentration of barley minimized the drop in culture pH and improved digestibility. Unexpectedly, the lesser fiber content of the hulless barley reduced microbial protein synthesis but improved digestibility.