Preliminary Observations upon Factors Influencing Cellulose Digestion by Rumen Microorganisms1
Summary
A laboratory method is described for studying cellulose digestion by rumen microorganisms. The major features of this method include the use of continuous 36-hour fermentation periods, in which the original starting inoculum was a mixed culture of organisms taken directly from the rumen of cattle. The inoculum used in the second and succeeding 36-hour periods consisted of half the residue from the preceding fermentation. Cellulose digestion was determined chemically on the half portions not used as inoculum, and Gram stains of the microflora were observed at the beginning and end of each fermentation period.
Application of the method in preliminary trials resulted in data showing pronounced differences in the ability of rumen microorganisms to digest cellulose, depending upon additions or withdrawals from the nutrient medium as the fermentation periods progressed. Additions which proved helpful to cellulose digestion included a complex salt solution, the ash of alfalfa extract, autoclaved rumen liquid, and an autoclaved water extract of manure. Recovery trials with certain additions of these materials restored the ability to digest cellulose which had previously been lost through the omission of such additions.
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Effect of substrate and feed antibiotics on in vitro production of volatile fatty acids and methane in caecal contents of chickens
1999, Animal Feed Science and TechnologyAn attempt was done to identify some factors influencing the caecal fermentation pattern in poultry. Experiments were conducted to study effects of carbohydrate substrates (feed components and supplements) and antibiotics on the formation of volatile fatty acids (VFA) and methane in in vitro incubations of the caecal contents of 7-week-old chickens. Stoichiometry of fermentation differed in cultures with different carbohydrates. Fermentation pattern characterized by high propionate and low acetate production was found in cultures with lactose (0.447 and 0.376 mol/1 mol of VFA produced, respectively) and, to a lesser extent, also in cultures with raffinose. Acetate was the predominant metabolite of starch, pectin and xylan (0.727, 0.773 and 0.685 mol/1 mol of VFA produced, respectively). Fermentation of inulin resulted in high proportion of butyrate, 0.221 mol/1 mol of VFA. Other polysaccharides produced only 0.060–0.111 mol of butyrate per 1 mol of VFA. Oligosaccharides (lactose, raffinose) were fermented more rapidly than polysaccharides. Fermentation of inulin yielded more VFA than fermentation of starch, pectin and xylan. No production of VFA from carboxymethylcellulose was observed. On average, 11 mols of VFA were produced per mol of methane. Lasalocid significantly increased molar proportion of propionate, which is potentially beneficial from the point of view of salmonellae control. The magnitude of improvement, however, was small. Other feed antibiotics tested (avoparcin, bacitracin, lincomycin, spiramycin, tylosin, virginiamycin) produced only non-significant or marginal fermentation shifts. Formation of valerate, isoacids and methane was not significantly influenced by the substrate or by antibiotic treatment.
Effects of supplementation with fish meal or fish protein hydrolysate on growth, nutrient digestibility and rumen fermentation of growing cattle fed grass silage
1997, Animal Feed Science and TechnologyTwo experiments were conducted to determine the effects of supplementing grass silage (S) with isonitrogenous amounts of fish meal (FM; 380 g head−1 d−1) or fish protein hydrolysate (FPH; 300 g head−1 d−1) on growth, diet digestibility and rumen fermentation in beef cattle. In the first experiment, 36 crossbred steers were used in a 112 d growth trial to determine treatment effects on dry matter intake (DMI), average daily gains (ADG) and feed to gain ratio. Protein supplementation did not affect silage DMI, but increased ADG by 18% (P < 0.01) and feed to gain ratio by 6% (P < 0.08). The increase in ADG with FM was 12% higher than that obtained with FPH (P < 0.01). In a second experiment, six rumen fistulated heifers were used in a double 3 × 3 Latin square to study treatment effects on apparent digestibility and rumen fermentation. Protein supplementation increased apparent DM and N digestibility when compared to the S treatment (P < 0.04). Apparent ADF digestibility was 3.0% higher in heifers fed FM than in those fed FPH (P < 0.05). Rumen pH decreased immediately after feeding (P < 0.001), but was not affected by the treatments. Total volatile fatty acids (VFA) concentrations were not significantly affected by supplementation but by time; they were higher for the FM than for the FPH diet at all times (P < 0.02). Acetate propionate ratio was lower in heifers fed silage alone (P < 0.02). Rumen NH3N levels during the first 4 h after feeding were higher in animals receiving protein supplements (P < 0.001). From 0 to 2 h after feeding, rumen free α-amino-N increased almost twice as high in heifers fed FM than in those fed FPH (P < 0.05); however, at 4 and 6 h post feeding, the situation reversed. Plasma urea N was lower in animals fed only silage (P < 0.01). Total essential amino acids were higher in animals receiving protein supplementation than in those fed silage alone (P < 0.03) and tended to be higher in heifers fed FM than in those fed FPH (P < 0.08).
Degradation of methionine by rumen contents in vitro and efficiency of its protection
1997, Animal Feed Science and TechnologyDegradation of methionine (M), soya isolate (S) and casein hydrolysate (C) has been evaluated by incubation of these substrates (100 mg) with sheep rumen contents in vitro, in the presence of starch (250 mg). Five incubations were performed using one adult rumen fistulated sheep fed 300 g of hay and 300 g of concentrate daily. Total NH3 production at different sampling times (after 2, 4, 6, 8 and 24 h of incubation) was calculated by subtracting the net NH3-N production observed in the incubation containing starch only from that produced in the incubation containing the substrate. Protected M preparations, Smartamine (Sm) and Mepron (Mp), were also used. During two incubations of M, using four sheep on permanent pasture or fed four different hays, it was shown that the net disappearance of free M matches net NH3 production at both low (2 mM) and high (20 mM) M concentration. The results indicate that the initial M degradation rate (3 h of incubation) was 12–14% that of C and never exceeded 1.5 mmol h−1 l−1 of rumen contents. Adaptation of the sheep rumen by daily introduction of 5 or 20 g of DL-methionine for 21 and 8 days, respectively, did not change this result (three to four incubations with rumen contents of three sheep fed 300 g of hay and 300 g of two different concentrates). The results also indicate that protection against rumen degradation was effective for Sm but not for Mp. The ‘effective degradation rate’ of M was estimated as 0.30 that of protein. Considering the high price of protected M (four to five fold the price of non protected M), and the low degradation rate of M, it is suggested that the latter be used at 1.43 of the amount normally added as rumen protected M, to obtain the same result.
Lasting effects of monensin on rumen and caecal fermentation in sheep fed a high grain diet
1996, Animal Feed Science and TechnologyEventual adaptation of rumen fermentation to monensin feeding has been studied in two rumen and caecal fistulated sheep fed 150 g of hay and 500 g of concentrates at 9.00 h and 16.00 h. After a control period of 23 days, a dose of 60 mg of monensin was infused for 6 days. This period was followed by a 29 day period during which 50 mg were administered. Monensin was introduced into the rumen as an aqueous suspension, just prior to feeding (with the 60 mg dose: before the morning feeding; with the 50 mg dose: 25 mg twice daily before each feeding).
The following rumen fermentation parameters were determined in vivo: methane expelled through the fistula for 6 h per day, pH, total volatile fatty acids (VFA) concentration, molar proportions of VFA, lactate and ammonia concentration in rumen fluid sampled 2 h after monensin administration, and in sacco degradability of hay (24 h). In vitro incubations of 24 h were carried out with caecal contents sampled continuously from one sheep between 9.30 h and 10.00 h.
Methane production in the rumen (in vivo) and in the caecum (in vitro) was decreased by monensin feeding. The molar proportion of propionate in the rumen was increased, while acetate and butyrate percentages were sometimes lowered. Total VFA concentration was not significantly decreased while ammonia concentration was lowered. Production of propionate in the caecum in vitro was stimulated by monensin administration while methanogenesis and acetate production were inhibited. The in sacco degradability of hay (dry matter) was not affected by monensin administration.
These modifications of rumen and caecum fermentation persisted as long as monensin was given, indicating that on a high grain diet, no adaptation of rumen fermentation to the ionophore was observed. On the other hand, the incubations with caecal contents showed clearly that monensin caused analogous and persistent changes in fermentation pattern in the lower gastro-intestinal tract also.
Lipolysis and Biohydrogenation of Soybean Oil in the Rumen In Vitro: Inhibition by Antimicrobials
1995, Journal of Dairy ScienceThis experiment attempted to lower rumen lipolytic activity, biohydrogenating activity, or both using antimicrobial compounds. In vitro incubations were carried out with rumen fluid, 80 mg of soybean oil, and .5 g of commercial concentrates as substrate. Unless stated otherwise, the final concentration of the additives in the incubation was 20 ppm. Lipolysis and biohydrogenation were determined by separation of triacylglycerols and FFA by TLC; the fatty acid composition of each was determined by GLC before and after incubation and with or without additive. With some of the antibiotics, lipolysis was inhibited 10 to 20%, and the most potent inhibitors were ionophores and amoxicillin. Biohydrogenation (including c18:1) decreased only for lasalocid, but no additive could prevent hydrogenation of linolenic acid liberated from triacylglycerols. Some additives decreased hydrogenation of linoleic acid, but only slightly. Lipolytic activity decreased VFA production more than the other potent additives (amoxicillin, avoparcin, lasalocid sodium, monensin, and salinomycin sodium). This result could indicate a more specific toxic effect on lipolytic microbes. Finally, different antimicrobials influenced fermentation patterns differently (VFA proportions and CH4 production), but shifts were always in accordance with stoichiometric principles.
In vitro digestibility studies of some local and high yielding varieties of rice straw (Oryza sativa)
1993, Animal Feed Science and TechnologyFive local and four high-yielding varieties (HYV) of rice straw (Oryza sativa) were analysed for their various chemical constituents. The HYV rice straw samples were found to contain more glucose and xylose residues and less crude protein than those of the local varieties. Ash and silica contents were high in both groups.
Extensive in vitro rumen digestibility studies showed that the HYV rice straw generally had higher dry matter disappearance (DMD) and organic matter disappearance (OMD) values compared with the local varieties. The in vitro rumen degradation patterns of cellulose, hemicellulose and bound p-coumaric and ferulic acids in rice straw cultivars ‘BR14’ and ‘Balam’ were similar. Klason lignin degradation was low in both the samples.
Alkali treatment increased the DMD and OMD values of all the samples by an average of 14% and 15%, respectively.
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Published with the approval of the Director of the Ohio Agricultural Experiment Station. Supported in part by a grant-in-aid from Swift and Company, Chicago, Illinois.