Effects of degradable protein and non-fibre carbohydrates on microbial growth and fermentation in the rumen simulating fermenter (Rusitec)

• Main Authors: Xiang H. Zhao, Jian M. Gong, Shan Zhou, Chuan B. Fu, Chan J. Liu, Lan J. Xu, Ke Pan, Ming R. Qu
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2015-05-01
• Series: Italian Journal of Animal Science
• Subjects: Microbial protein synthesis; Pectin; Ruminal degradable protein; Rusitec
• Online Access: http://www.aspajournal.it/index.php/ijas/article/view/3771
• ISSN: 1594-4077; 1828-051X

A rumen simulation technique (Rusitec) apparatus with eight 800 ml fermentation vessels was used to investigate the effects of rumen degradable protein (RDP) level and non-fibre carbohydrate (NFC) type on ruminal fermentation, microbial growth, and populations of ruminal cellulolytic bacteria. Treatments consisted of two NFC types (starch and pectin) supplemented with 0 g/d (low RDP) or 1.56 g/d (high RDP) sodium caseinate. Apparent disappearance of dry matter and organic matter was greater for pectin than for starch treatment (P&lt;0.01) with low or high RDP. A NFC × RDP interaction was observed for neutral detergent fibre disappearance (P=0.01), which was lower for pectin than for starch only under low RDP conditions. Compared with starch, pectin treatment increased the copy numbers of <em>Ruminococcus albus</em> (P≤0.01) and <em>Ruminococcus flavefaciens</em> (P≤0.09), the molar proportion of acetate (P&lt;0.01), the acetate:propionate ratio (P&lt;0.01), and methane production (P&lt;0.01), but reduced the propionate proportion (P&lt;0.01). Increasing dietary RDP increased the production of total VFA (P=0.01), methane (P&lt;0.01), ammonia N (P&lt;0.01), and microbial N (P&lt;0.01). Significant NFC × RDP interaction and interaction tendency were observed for ammonia N production (P=0.01) and daily N flow of total microorganisms (P=0.07), which did not differ under low RDP conditions, but pectin produced greater microbial N and less ammonia N than starch with increased RDP. Results showed NFC type, RDP level, and their interaction affected ruminal fermentation and microbial growth, and under sufficient ruminal degradable N pectin had greater advantage in microbial N synthesis than starch <em>in vitro</em>.