Influence of rumen fluid and substrate concentration on fermentation kinetics measured with a fully automated time related gas production apparatus

A 2 3 2 factorial feeding experiment was conducted to examine the effects of varying the maturity level of the grass used to prepare silage and the nature of concentrate starch source and their interactions on dry matter intake (DMI), diet digestibility, energy corrected milk (ECM) production and milk composition in dairy cows. Twenty-eight multiparous Swedish Red dairy cows, 133 6 45 days in milk (DIM), with an average milk yield of 30 6 4 kg/day and a live weight of 624 6 69 kg were blocked by DIM and randomly assigned to seven replicated balanced 4 3 4 Latin squares with four 21-day experimental periods. The experimental diets consisted of four total mixed rations (TMR) consisting of early-cut grass silage (EGS) supplemented with either barley-or maize-based concentrate and late-cut grass silage (LGS) supplemented with either barley-or maize-based concentrate. All TMR contained identical proportions of forage (51%) and concentrate (49%). Total tract digestibility was estimated by determining indigestible NDF (iNDF) concentrations in feeds and faeces and using iNDF as an internal marker. The feeds' ruminal degradation parameters were determined using both in situ (nylon bag) and in vitro (gas production (GP)) techniques. Cows offered diets containing EGS had greater (P , 0.001) daily dry matter (DM) intakes, ECM yields and total tract digestibilities for DM and organic matter (OM), but these were not affected by the nature of the concentrate starch source. No interaction between the maturity of the silage and the nature of the concentrate starch source was observed for DMI, diet digestibility or ECM yield. Both grass silages and concentrates had similar rates of ruminal degradation of NDF when measured in situ. The in situ DM (P , 0.001) and starch (P 5 0.001) degradation rates of barley-based concentrate were greater than those for maize-based concentrate. In vitro OM GP rates and extents were similar for both concentrate feeds. The results showed that diets containing EGS offered better animal performance and diet digestibility than diets containing LGS. The concentrate starch source did not affect animal performance, but total NDF digestibility was better with diet containing barley-than maize-based concentrate.

Section: Animals Diets Feeding and Experimental Designmentioning

confidence: 99%

The effects of and interactions between the maturity of grass silage and concentrate starch source when offered as total mixed rations on the performance of dairy cows

Tahir

Lund

Hetta

2013

“…Caecal fluid was then strained through eight layers of cheesecloth and kept at 398C under a constant flux of CO 2 . Incubations were performed using methods previously described by Cone et al (1996) with minor modifications. The buffer-mineral solution was N-free and contained 10.03 g/l NaHCO 3 , 1.43 g/l Na 2 HPO 4 , 1.55 g/l KH 2 PO 4 , 0.15 g/l MgSO 4 Á 7H 2 O, 0.52 g/l Na 2 S, 0.017 g/l CaCl 2 Á 2H 2 O, 0.015 g/l MnCl 2 Á 4H 2 O, 0.002 g/l CoCl 3 Á 6H 2 O, 0.012 g/l FeCl 3 Á 6H 2 O and 0.125 mg/l resazurin.…”

Section: Gas Production Incubationsmentioning

confidence: 99%

The influence of casein and urea as nitrogen sources on in vitro equine caecal fermentation

Santos

Ferreira

Martin‐Rosset

et al. 2012

To access the fermentative response of equine caecal microbial population to nitrogen availability, an in vitro study was conducted using caecal contents provided with adequate energy sources and nitrogen as limiting nutrient. Two nitrogen (N) sources were provided, protein (casein) and non-protein (urea). Caecal fluid, taken from three cannulated horses receiving a hay-concentrate diet, was mixed with a N-free buffer-mineral solution. The influence of four N levels (3.7, 6.3, 12.5 or 25 mg of N in casein or urea) was studied using the gas production technique. Total volatile fatty acids (VFA), NH 3 -N and gas production were measured after a 24-h incubation period. Microbial biomass was estimated using adenine and guanine bases as internal markers, and ATP production was estimated stoichiometrically. Microbial growth efficiency (Y ATP ) and gas efficiency (E gas ) were estimated. Fermentation with casein as the sole N source was generally characterized by lower total VFA, NH 3 -N, total gas production and higher acetate : propionate (A : P) ratio and Y ATP than with urea. Results herein presented indicate that, under these in vitro conditions, caecal microbial population does in fact use urea N, but less efficiently than casein in terms of microbial growth.

“…The in vitro fermentation was performed using a fully automated gas production technique as described by Cone et al (1996). Rumen fluid was collected 2 h after morning feeding from three lactating rumencannulated cows (220 ± 38 days in milk; production 27.9 ± 3.3 kg milk/day), fed as described in the previous section.…”

Section: Methodsmentioning

confidence: 99%

“…Rumen fluid was collected 2 h after morning feeding from three lactating rumencannulated cows (220 ± 38 days in milk; production 27.9 ± 3.3 kg milk/day), fed as described in the previous section. Samples of 0.5 g of the total feed ingredient and their isolated non-washout fraction obtained by washing machine rinsing were incubated in 60 ml buffered rumen fluid in 250 ml bottles in a shaking water bath at 39 o C, and gas production was recorded for 48 h as described by Cone et al (1996). Individual incubations were stopped at 4, 8, 24 and 48 h by addition of hydrochloric acid and contents of the bottles were freeze dried.…”

Section: Methodsmentioning

confidence: 99%

Estimation of the in situ degradation of the washout fraction of starch by using a modified in situ protocol and in vitro measurements

Jonge

Laar

Dijkstra

2015

The in situ degradation of the washout fraction of starch in six feed ingredients (i.e. barley, faba beans, maize, oats, peas and wheat) was studied by using a modified in situ protocol and in vitro measurements. In comparison with the washing machine method, the modified protocol comprises a milder rinsing method to reduce particulate loss during rinsing. The modified method markedly reduced the average washout fraction of starch in these products from 0.333 to 0.042 g/g. Applying the modified rinsing method, the fractional degradation rate ( k d ) of starch in barley, oats and wheat decreased from on average 0.327 to 0.144 h −1 whereas for faba beans, peas and maize no differences in k d were observed compared with the traditional washing machine rinsing. For barley, maize and wheat, the difference in non-fermented starch in the residue between both rinsing methods during the first 4 h of incubation increased, which indicates secondary particle loss. The average effective degradation of starch decreased from 0.761 to 0.572 g/g when using the new rinsing method and to 0.494 g/g when applying a correction for particulate matter loss during incubation. The in vitro k d of starch in the non-washout fraction did not differ from that in the total product. The calculated ratio between the k d of starch in the washout and non-washout fraction was on average 1.59 and varied between 0.96 for oats and 2.39 for maize. The fractional rate of gas production was significantly different between the total product and the non-washout fraction. For all products, except oats, this rate of gas production was larger for the total product compared with the non-washout fraction whereas for oats the opposite was observed. The rate of increase in gas production was, especially for grains, strongly correlated with the in vitro k d of starch. The results of the present study do not support the assumption used in several feed evaluation systems that the degradation of the washout fraction of starch in the rumen is much faster than that of the non-washout fraction.Keywords: particulate matter loss, in situ protocol, in vitro, rumen degradability, starch ImplicationThis study showed that the fractional degradation rate (k d ) of starch of the washout fraction was lower than generally assumed. In addition, the rinsing method affected the k d caused by particulate matter loss. The effect of both observations on the effective degradation of starch varied between feed ingredients, and can therefore change the ranking in nutritive value.