Effects of Type of Carbohydrate Supplementation to Lush Pasture on Microbial Fermentation in Continuous Culture

Department of Animal Science, University of Minnesota, St. Paul 55108, USA.
Journal of Dairy Science (Impact Factor: 2.57). 02/1999; 82(1):153-60. DOI: 10.3168/jds.S0022-0302(99)75219-7
Source: PubMed


Eight single-flow continuous culture fermenters were used to study the effects of the type of energy source on ruminal N utilization from high quality pasture. The four dietary treatments included high quality grass and legume pasture alone (50:50; wt/wt), pasture plus soybean hulls, pasture plus beet pulp, and pasture plus corn. Diets supplemented with additional sources of energy (soybean hulls, beet pulp, and corn) were isocaloric but differed in the type and rate of carbohydrate fermentation. Energy supplements constituted 45% of the total dietary dry matter and were fed twice daily at 12-h intervals in place of pasture, which is characteristic of grain feeding at milking when animals are in a grazing situation. Energy supplementation reduced pH, NH3 N flow, and NH3 N concentration and increased bacterial N flow (as a percentage of N intake). The supplementation of corn and soybean hulls resulted in the highest microbial N flow (as a percentage of N intake). Corn had a tendency to reduce fiber digestion because of excessively low NH3 N concentrations. Beet pulp was similar to corn in that it decreased NH3 N concentrations. Supplementation of soybean hulls resulted in a more synchronized fermentation, greater volatile fatty acid production, and greater fiber digestion. Nitrogen utilization by microbes was maximized by supplementation with soybean hulls or corn twice a day. With diets based on pasture, it may be more important to improve bacterial N flow and bacterial utilization of N than to maximize the efficiency of bacterial protein synthesis because better utilization of N by ruminal microorganisms results in higher bacterial N flow and higher fiber digestion.

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    • "Nevertheless, in this study, the NFC values for supplemented groups (29% to 39%) did not lead to a higher microbial protein synthesis. Bach et al. (1999), working in vitro with grass and legumes as forages supplemented with soybean hulls, beet pulp and corn, reported that the increment in NFC resulted in a rise of glycogen content in microbial cells and a decrease in bacterial N. Similarly to this study Feng et al. (1993), providing high and low NFC diets combined with rapidly or slowly degraded NDF on dairy cows, found that an increase from 29% to 39% of NFC in the diet resulted in a reduction in the EMPS. Although supplementation did not increase microbial protein yield, greater values for both measures and for DOMI were observed during P2 for all treatment groups. "
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    ABSTRACT: To determine whether non-fibrous carbohydrate (NFC) supplementation improves fiber digestibility and microbial protein synthesis, 18 Corriedale ewes with a fixed intake level (40 g dry matter (DM)/kg BW0.75) were assigned to three (n = 6) diets: F = 100% fresh temperate forage, FG = 70% forage + 30% barley grain and FGM = 70% forage + 15% barley grain + 15% molasses-based product (MBP, Kalori 3000). Two experimental periods were carried out, with late (P1) and early (P2) vegetative stage forage. For P2, ewes were fitted with ruminal catheters. Forage was distributed at 0900 h, 1300 h, 1800 h and 2300 h, and supplement added at 0900 h and 1800 h meals. Digestibility of the different components of the diets, retained N and rumen microbial protein synthesis were determined. At the end of P2, ruminal pH and N-NH3 concentration were determined hourly for 24 h. Supplementation increased digestibility of DM (P < 0.001) and organic matter (OM; P < 0.001) and reduced NDF digestibility (P = 0.043) in both periods, with greater values in P2 (P = 0.008) for the three diets. Daily mean ruminal pH differed (P < 0.05) among treatments: 6.33 (F), 6.15 (FG) and 6.51 (FGM). The high pH in FGM was attributed to Ca(OH)2 in MBP. Therefore, the decreased fiber digestibility in supplemented diets could not be attributed to pH changes. The mean ruminal concentration of N-NH3 was 18.0 mg/dl, without differences among treatments or sampling hours. Microbial protein synthesis was greater in P2 (8.0 g/day) than in P1 (6.1 g/day; P = 0.006), but treatments did not enhance this parameter. The efficiency of protein synthesis tended to be lower in supplemented groups (16.4, 13.9 and 13.4 in P1, and 20.8, 16.7 and 16.2 g N/kg digestible OM ingested in P2, for F, FG and FGM, respectively; P = 0.07) without differences between supplements. The same tendency was observed for retained N: 2.55, 1.38 and 1.98 in P1, and 2.28, 1.23 and 1.10 g/day in P2, for F, FG and FGM, respectively; P = 0.05). The efficiency of microbial protein synthesis was greater in P2 (P = 0.007). In conclusion, addition of feeds containing NFCs to fresh temperate forage reduced the digestibility of cell walls and did not improve microbial protein synthesis or its efficiency. An increase in these parameters was associated to the early phenological stage of the forage.
    Full-text · Article · Apr 2012 · animal
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    • "As pointed out by Bach et al. (2005), bacterial chemical composition is affected by the availability of energy and N as well as by the availability of AA (Wang et al., 2008). High proportions of concentrate in the diet (Ranilla and Carro, 2003) and supplementation of maize starch to grass pasture (Bach et al., 1999) were reported to reduce the N content in the microbial mass. In this study, N contents of microbial fractions were lowest in maize silage-and highest in grass silage-based diets. "
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    ABSTRACT: The objective was to investigate the effect of variation in forage source and feed particle size of a diet, including interactions, on the amount and the composition of microbial crude protein (CP) in a semi-continuous culture system (Rusitec). Different microbial CP fractions were compared. Five diets with mean forage proportion of 0.88 and different maize silage to grass silage ratios (100 : 0, 79 : 21, 52 : 48, 24 : 76 and 0 : 100) were used. Diets were ground through sieves with a pore size of either 1 or 4 mm, matching the particle size of fine (F) and coarse (C), respectively. Diets were characterised by increasing concentrations of CP and fibre fractions, and decreasing concentrations of starch with ascending inclusion rates of grass silage. Microbial mass was isolated from feed residues after incubation from the liquid phase of the fermenter and from the liquid effluent. The amount of synthesised microbial CP was determined on the basis of 15N balance. It increased quite linearly by the stepwise replacement of maize silage by grass silage, and was higher in C treatments compared to F treatments. Efficiency of microbial CP synthesis (EMPS) was improved from 29 to 43 mg microbial N/g degraded organic matter (OM) by increasing the proportion of grass silage in the diet, but was unaffected by particle size. The N content as well as the profiles of amino acids of the three microbial fractions was affected by diet composition and particle size. The ratio of solid- to liquid-associated microbes was affected by diet composition and feed particle size. The amount and EMPS seemed to be improved by degradation of OM from grass silage and an increasing availability of N. Moreover, the results of this study indicated a shift in the composition of the microbial community caused by variation in forage composition and feed particle size.
    Preview · Article · Feb 2011 · animal
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    • "It was also noted that propionate production was remarkably high and resulted in a suitable ratio of acetate to propionate ratio (2.38-3.29). Bach et al. (1999) found that the proportion of acetate increased when fiber intake increased, while Zebeli et al. (2008) found that elevating non-structural carbohydrate intake decreased ruminal acetate proportion. However, proportions of acetate, propionate and butyrate in this study were in accordance with Hungate (1966). "
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    ABSTRACT: Six male crossbred (Thai NativeAnglo Nubian) goats, with an average initial weight of , were randomly assigned according to a factorial arrangement in a Latin square design with a 21-d period to evaluate the effect of feeding rubber seed kernel (RSK) and palm kernel cake (PKC) in combination on nutrient utilization, rumen fermentation characteristics, and nitrogen utilization. The dietary treatments were as follows: i) concentrate containing 0% RSK and 20% PKC (), ii) 0% RSK and 30% PKC (), iii) 20% RSK and 20% PKC (), iv) 20% RSK and 30% PKC (), v) 30% RSK and 20% PKC (), and vi) 30% RSK and 30% PKC (). During the experiment, signal hay was given on an ad libitum basis as the roughage. It was found that RSK levels and PKC levels had no interaction effects on feed intake, apparent digestibility, -N, blood metabolites, VFA concentrations, and nitrogen utilization, but there were interactions between RSK levels and PKC levels with respect to total DMI (kg/d) and total VFA concentrations, and goats receiving 30% RSK had lower values (p0.05) feed intake, digestibility, rumen fermentation patterns, blood metabolites, and nitrogen utilization. However, increasing RSK levels (>20%) resulted in a slightly lower daily DMI (% BW and g/kg ), apparent digestibility (NDF and ADF), total N intake, and N excretion than in goats fed on 0 and 20% RSK. BUN, blood glucose, and propionate were variable among treatment and were highest in 0% RSK with the 20% PKC fed group having values which were higher than those in other groups. However, there were no differences (p>0.05) among treatments with respect to N retention, PD output, and microbial N supply. Based on this study, RSK levels up to 20% and PKC at 20-30% in concentrate could be efficiently utilized for goats fed on signal hay.
    Full-text · Article · Jan 2011 · Asian Australasian Journal of Animal Sciences
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