Rumen Fermentation of Feed Mixtures Supplemented with Clay Minerals in a Semicontinuous In Vitro System

Interest in using clays in the diets of ruminants to improve health and performance is increasing. The microbial fermentation of 65:35 (HC) or 35:65 (HF) concentrate:forage feeds, alone or with zeolite (Z), bentonite (B), or sepiolite (S), was studied in an in vitro semicontinuous culture system. The medium pH was allowed to drop for the first 6 h and was gradually buffered thereafter. For the HC diet, the medium pH was higher with Z throughout incubation (p 0.05) were observed in dry matter disappearance, microbial mass, or volatile fatty acids. However, the inclusion of B in HC reduced the ammonia concentration at 6 and 12 h with respect to C (p < 0.05). The inclusion of zeolite as an additive in the diets of ruminants stabilizes the rumen environment during the first stages of fermentation in terms of pH and ammonia concentration, especially in high-concentrate diets. The buffering effect of bentonite and sepio-lite was lower, and both might reduce ruminal microbial fermentation, depending on the concentrate proportion

Fitting of the in vitro gas production technique to the study of high concentrate diets

In vitro rumen fermentation systems are often adapted to forage feeding conditions, with pH values ranging in a range close to neutrality (between 6.5 and 7.0). Several attempts using different buffers have been made to control incubation pH in order to evaluate microbial fermentation under conditions simulating high concentrate feeding, but results have not been completely successful because of rapid exhaustion of buffering capacity. Recently, a modification of bicarbonate ion concentration in the buffer of incubation solution has been proposed, which, together with using rumen inoculum from donor ruminants given high-concentrate diets, allows for mimicking such conditions in vitro. It is important to consider that the gas volume recorded is in part directly produced from microbial fermentation of substrates, but also indirectly from the buffering capacity of the medium. Thus, the contribution of each (direct and indirect) gas source to the overall production should be estimated. Another major factor affecting fermentation is the rate of passage, but closed batch systems cannot be adapted to its consideration. Therefore, a simple semicontinuous incubation system has been developed, which studies the rate and extent of fermentation by gas production at the time it allows for controlling medium pH and rate of passage by manual replacement of incubation medium by fresh saliva without including rumen inoculum. The application of this system to studies using high concentrate feeding conditions will also be reviewed here

Fermentation pattern of several carbohydrate sources incubated in an in vitro semicontinuous system with inocula from ruminants given either forage or concentrate-based diets

The fermentation pattern of several carbohydrate sources and their interaction with the nature of microbial inoculum was studied. Barley (B), maize (M), sorghum, (S), sugarbeet pulp (BP), citrus pulp (CP) and wheat bran (WB) were tested in an in vitro semicontinuous system maintaining poorly buffered conditions from 0 to 6 h, and being gradually buffered to 6.5 from 8 to 24 h to simulate the rumen pH pattern. Rumen fluid inoculum was obtained from lambs fed with either concentrate and barley straw (CI) or alfalfa hay (FI). The extent of fermentation was higher with CI than FI throughout the incubation (p < 0.05). Among the substrates, S, BP and M maintained the highest pH (p < 0.05), whereas CP recorded the lowest pH with both inocula. Similarly, CP recorded the highest gas volume throughout the incubation, followed by WB and B, and S recorded the lowest volume (p < 0.05). On average, the total volatile fatty acid (VFA), as well as lactic acid concentration, was higher with CP than in the other substrates (p < 0.05). The microbial structure was more affected by the animal donor of inoculum than by the substrate. The in vitro semicontinuous system allows for the study of the rumen environment acidification and substrate microbial fermentation under intensive feeding conditions. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Fitting of pH conditions for the study of concentrate feeds fermentation by the in vitro gas-production technique

Two experiments were conducted to simulate in vitro the fermentation conditions under high-concentrate feeding. The concentration of bicarbonate ion in the buffer of the incubation solution was assayed in Experiment 1, by adjusting medium pH to 6.50, 6.25, 6.00, 5.75 and 5.50, in two incubation series of 12 h, using barley as the reference substrate. The pH diminished linearly (P < 0001) by lowering the buffer, and remained constant throughout 12 h, except for treatments 5.75 and 5.50, where pH dropped to 5.51 and 5.31 at 12 h. Gas production decreased linearly with a decreasing medium pH (P < 0.001), with the total volume of gas produced after 12 h being highly dependent (P < 0.01) on pH at 12 h (R 2 = 0.629), thus demonstrating the importance of the incubation pH for estimation of fermentation of concentrate feeds. In Experiment 2, the effect of pH on direct and indirect proportion of gas was studied by adding 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 mmol of acetic acid, either with or without (water added instead) rumen inoculum, to the media. Linear multiple regressions established between the volume of gas produced and the addition of acetic acid, and the bicarbonate ion concentration showed high determination coefficients for water (R 2 = 0.929) and rumen inoculum (R 2 = 0.851). Without inoculum, indirect gas production ranged from 9.4 to 12.4 mL/mmol of acid for medium pH of 5.50-6.50. With rumen inoculum, indirect gas was 20.8 mL/mmol acid, although this may have been biased by the contribution of inoculum itself to direct fermentation

In vitro fermentation pattern and acidification potential of different sources of carbohydrates for ruminants given high concentrate diets

The in vitro fermentation pattern of five sources of carbohydrates of differing nature (maize grain, MZ; sucrose, SU; wheat bran, WB; sugarbeet pulp, BP; and citrus pulp, CT) under conditions of high concentrate diets for ruminants was studied. A first 8 h incubation trial was performed under optimal pH using inoculum from ewes given a fibrous diet, to compare fermentative characteristics of substrates. As planned, incubation pH ranged within 6.3 to 6.6. The gas produced from CT was higher than MZ, SU and BP from 4 and 6 h onwards, and at 8 h, respectively (p0.05) on total volatile fatty acid (VFA) concentration, nor on acetate or propionate proportions, but butyrate was lowest (p<0.05) with CT and BP. The second incubation trial was performed in a poorly-buffered medium, with inoculum from ewes given a concentrate diet. All substrates showed a gradual drop of pH, being lowest with SU after 4 h (p<0.05). Throughout the incubation, gas production was highest with CT and lowest with MZ and BP (p<0.05). Total 8 h VFA concentration was higher with CT than BP, SU and MZ (p<0.05). Acetate proportion was higher, and that of propionate lower, with BP than WB (p<0.05), butyrate proportion being higher with MZ and WB than with BP and CT (p<0.05). Lactic acid concentration was higher (p<0.05) with SU than WB and BP. Fermentation characteristics and acidification potential of feeds depend on the nature of their carbohydrate fraction, and must be considered for practical applications

In vitro acidification potential and fermentation pattern of cereal grains incubated with inoculum from animals given forage or concentrate based diets

This work aimed to study the acidification and fermentation pattern of maize (M1, M2, M3), barley (B1, B2, B3) and sorghum (S1, S2, S3) varieties depending on the rumen environment (inoculum from forage or concentrate diets, FI or CI), in 10 h incubation series with a low buffered medium. With CI, gas volume from barley was similar to maize (P > 0.05) except at 4 and 6 h, when M2 and M1 were lower. Barley or maize varieties did not differ in gas production (P > 0.05). After 10 h, barley and maize produced on average 82.5 and 73.0 mL/g organic matter (OM), whereas S1, S2 and S3 rendered 68.4, 31.1 and 39.7 mL/g. With FI, differences between barley and maize were detected after 6 h (61.0, 35.3 and 14.1 mL/g OM at 10 h for barley, maize and sorghum). Among inocula, pH with CI was lower than with FI (P < 0.001). Incubation pH at 10 h was 5.51, 5.21 and 5.00 with CI, and 5.52, 5.85 and 5.91 with FI, for sorghum, maize and barley varieties. Gas production and total volatile fatty acid (VFA) concentration were higher (P < 0.001) with CI than FI (67.3 vs 36.8 mL/g and 31.0 vs 19.9 mmol/L at 10 and 8 h). Butyrate and valerate proportions were higher with CI (P < 0.001), whereas acetate and branched chain VFA were lower (P < 0.001). Fermentative activity against vitreous starch such as maize or sorghum was lower for forage than concentrate inoculum. Study of fermentation of starch-rich substrates in a low buffered medium gives a more realistic picture than conventionally buffered conditions

Growth and bacterial dynamics of beef calves during transition from milk/pasture to a high-concentrate diet added with tannins or medium-chain fatty acids

Context. Rumen fermentation modulation with feed additives during the transition period to high-concentrate diets might help to avoid bacterial dysbiosis. Aims. Assessing the effects of the addition of tannins and medium-chain fatty acids (MCFA) to the adaptation diet of beef calves to a high-concentrate ration on the rate of intake, animal performance and rumen bacterial composition. Methods. Eighteen 7-month-old beef calves were abruptly weaned and transitioned over a 28-day period from a milk/grass regime to one of the following diets: a non-supplemented high-concentrate diet plus wheat straw, both given ad libitum (C); C plus 20 g/kg of a 65:35 chestnut and quebracho tannin extract; and C plus 6 g/kg of a commercial mixture of MCFA. Concentrate and straw rate of intake were recorded. Rumen fluid was collected on Days 0, 1, 7, 14, 21 and 28 at 0, 3, 6 and 9 h after feeding to characterise rumen fermentation. Samples from 0 h were analysed to assess the bacterial population using Ion Torrent sequencing. Key results. The rate of intake of concentrates and straw, as well as daily gains and final weights, were similar (P > 0.05) among diets. The addition of tannins or MCFA did not modify (P = 0.98) the rumen bacterial population, which was affected by sampling day (P < 0.001). The additives inclusion did not affect relative abundances of the main bacterial taxa (P < 0.05), most of them differing across days (P < 0.001). Diversity indexes (Shannon and richness) declined over sampling days (P < 0.05), although some genera emerged after concentrate inclusion. Conclusions. At the doses used in the present experiment, tannins and MCFA did not exert any effect on intake, animal performance and bacterial population. Abrupt transition to high-concentrate diets modified the rumen environment and bacterial community, indicating bacterial adaptation to new environmental conditions. Implications. Abrupt transition of 7-month-old calves from milk/pasture to a high-concentrate diet did not impair rumen microbiota or performance; therefore, the use of feed additives seems unnecessary. © 2021 CSIRO. All rights reserved

In vitro fermentation of barley according to the inclusion of levels of fatty acid additives in diets for intensive beef production

En dietas para rumiantes en cebo intensivo, así como para vacuno lechero, la adición de grasa en el concentrado permite aumentar la concentración energética y modificar el perfil de ácidos grasos absorbidos, además de atenuar la actividad fermentativa (Palmquist y Jenkins, 1980), contribuyendo a reducir el riesgo de acidosis ruminal.Trabajo financiado con el Proyecto AGL 2013-46820 (MINECO), con la ayuda del Departamento de Industria e Innovación) y el Fondo Social Europeo. S. Yuste disfrutó de una beca FPU (Ministerio de Educación, Cultura y Deporte).Unpublishe

Effect of adding essential oil compounds in diets for intensive beef production on in vitro barley fermentation

La intensificación de los sistemas de producción de carne en rumiantes supone la aparición frecuente de procesos de acidosis (Nagaraja y Titmeyer, 2007), pero un buen manejo alimentario puede prevenir la aparición de estos trastornos digestivos.Trabajo financiado con el Proyecto AGL 2013-46820 (MINECO), con la ayuda del Departamento de Industria e Innovación (Gobierno de Aragón) y el Fonso Social Europeo. S. Yuste disfrutó de una beca FPU (Ministerio de Educación, Cultura y Deporte).Publishe

Effect of preweaning diet on rumen fermentation and blood metabolites in beef calves

El consumo de alimentos sólidos (forrajes o pienso) durante la lactación es vital para alcanzar una correcta transición de pre-rumiante a rumiante adulto (Coverdale et al., 2004). La naturaleza de estos alimentos juega un papel importante en el desarrollo del rumen, provocando una mejor adaptación del animal a la posterior dieta de cebo, con altos niveles de carbohidratos rápidamente fermentables, y ayudando a prevenir la posterior aparición de problemas de acidosis (Khan et al., 2011). El objetivo de este experimento fue determinar el manejo nutricional más adecuado durante la lactación para conseguir una buena adaptación al posterior periodo de cebo en ganado vacuno de carne.Thirty calves of two breeds (Parda de Montaña and Pirenaica) were used to assess !he most suitable feeding strategy (milk only, milk + grass hay or milk + concentrate) during lactation to achieve an adequate adaptation of beef calves to the fattening period, when a high-concentrate die! is offered. Rumen fermentation parameters were affected by supplementation, resulting in a more developed rumen when concentrate was offered. Glucosa and P-hidroxybutyrate concentrations in plasma were not influenced by die! bu! showed a shift in metabolic pathways and fue! used by !he animal, except far animals supplemented with grass hay. Supplementing with concentrates during lactation seems a recommendable practica sinca it improvas ruman farmantation with a carry-ovar effact during transition when cattle will be fed a high-concentrate diet.Financiación procedente de Gobierno de Aragón, INIA-FEOER (RZP2012-02), MINECO (AGL2013-46820P), INIA-FSE (Contrato de M. Blanco) y MECO (beca FPU de S. Yuste, Ref.15/01960).Unpublishe