Effects of Degradable Protein and Non-Fibre Carbohydrates on Microbial Growth and Fermentation in the Rumen Simulating Fermenter (Rusitec)

Abstract

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<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 Ruminococcus albus (P≤0.01) and Ruminococcus flavefaciens (P≤0.09), the molar proportion of acetate (P<0.01), the acetate:propionate ratio (P<0.01), and methane production (P<0.01), but reduced the propionate proportion (P<0.01). Increasing dietary RDP increased the production of total VFA (P=0.01), methane (P<0.01), ammonia N (P<0.01), and microbial N (P<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 in vitro.

Effects of Replacing Extruded Maize by Dried Citrus Pulp in a Mixed Diet on Ruminal Fermentation, Methane Production, and Microbial Populations in Rusitec Fermenters

“…Neither MPS nor its efficiency were affected by diet in the present study, which is in agreement with the results of Ariza et al [21] when hominy feed was replaced by DCP in continuous-culture fermenters, although they observed a trend (p = 0.09) to decreased MPS efficiency by the inclusion of DCP. In contrast, Zhao et al [49] observed an increase in MPS in Rusitec fermenters when 15% of pure starch in the diet was substituted by 15% of pure citrus pectin, but the efficiency of MPS remained unchanged.…”

“…Barrios-Urdaneta et al [20] observed a linear decrease in the concentration of cellulolytic bacteria in the rumen of sheep when increasing proportions of DCP replaced barley grains in the diet, with no changes in amylolytic bacteria concentrations. In contrast, Zhao et al [49] observed an increase in the 16S rDNA gene copy numbers of Ruminococcus albus and Ruminococcus flavefaciens in Rusitec fermenters when 15% of pure starch in the diet was replaced by 15% pure citrus pectin. According to Ben-Ghedalia et al [18], highly digestible fiber, such as that of citrus pulp, provides an excellent substrate for bacterial colonization and increases the available substrates for cellulolytic bacteria.…”

“…Contrary to our results, several in vitro and in vivo studies reported decreases in NH 3 -N concentrations when the cereals in the diet were partly substituted by DCP. Zhao et al [49] observed that replacing 15% of starch by 15% pure citrus pectin in a mixed diet fed to Rusitec fermenters caused a reduction in the daily production of NH 3 -N, and Ariza et al [21] reported similar results in continuous-culture fermenters when DCP replaced dietary hominy feed. A reduction in NH 3 -N concentrations were also observed in the rumen of sheep when DCP substituted either 66% or 100% of barley grains [20] and when ensiled citrus pulp replaced 66% of wheat grains in the diet of dairy sheep [10].…”

“…In contrast, no pH changes caused by the inclusion of DCP in the diet have been observed by others. Thus, Zhao et al [49] reported no differences in rumen pH of Rusitec fermenters fed 50:50 forage:concentrate diets containing either 15% of pure citrus pectin or 15% of pure maize starch. Similarly, no differences in pH were reported when steers fed a tropical grass based diet were supplemented daily with 0, 1.5, or 2.5 kg of pelleted DCP [50], when DCP replaced maize in the concentrate fed to grazing cows [51], or when barley grains were totally replaced by DCP in a 50:50 forage:concentrate diet for dairy sheep [20].…”

Effects ofMomordica charantiapolysaccharide onin vitroruminal fermentation and cellulolytic bacteria

“…The result indicated that cellulolytic bacteria population responded differently to MCP inclusion. Zhao et al (2015) have reported that pectin increased the copy numbers of R. albus and R. flavefaciens in vitro using goat rumen fluid as inoculum. Joshua & Daniel (1993) have reported that rumial bacterial strains (Fibrobacter succinogenes, Ruminococcus flavefaciens, Ruminococcus albus and Butyrivibrio fibrisolvens) solubilised cotton stalks cell walls polysaccharides differently and the utilisation of solubilised cellulose, xylan, hemicellulose sugars and total carbohydrates by these ruminal bacterial strains was also varied.…”