Ruminal Volatile Fatty Acids Research Articles

Growth performance and carcass characteristics of lambs fed halophytes as a partial or whole replacement of berseem hay

The aim of this study was to evaluate partial or whole substitution of berseem hay with Atriplex nummularia (AT) and/or Acacia saligna (AC) in the diet of Barki lambs. Thirty-six male lambs (body weight 26.5±1.1kg and age 13±1.1 months) were divided into four groups and fed: (1) the control diet (70% concentrate mixture and 30% berseem hay), (2) AT (AT15 diet) or (3) AC (AC15 diet) replaced 50% of berseem hay in the diet, or (4) AT and AC at a ratio of 1:1 to replace 100% of berseem hay (TC30 diet), respectively. Lamb growth performance, rumen fermentation, blood chemistry, carcass characteristics and intestine histological properties were investigated. Dry matter intake, daily weight gain and feed conversion were measured every two weeks (period) for 10 weeks. Interactions were observed (P<0.05) between period×diet for these measurements and period affected (P<0.05) daily weight gain and feed conversion. Lambs in the AT15 and AC15 groups had increased (P<0.05) dry matter intake (g/lamb/day), water consumption (L/lamb/day), daily weight gain (g/lamb/day) and feed conversion (feed intake/body weight gain) during the last 2, 6, 2 and 8–10 weeks, respectively. The treatments AT15, AC15 and TC30 had decreased concentrations (P<0.01) of ruminal volatile fatty acids, but did not affect ruminal ammonia-N concentrations. Lambs fed the experimental diets had lower (P<0.05) concentrations of blood cholesterol, low density lipoproteins and glucose and higher (P<0.05) concentrations of serum urea. The treatment AT15 had increased (P<0.05) gut fill, pelt and mesentery weights, whereas the treatment AC15 increased (P<0.05) spleen and lung weight as a percentage of carcass weight. In regards to the protein content of the 9–11th ribs, the treatment AT15 was similar to the control, but the AC15 and TC30 were lower (P<0.05) than the control. Lambs in the treatment groups showed a normal histology of ileum, sub-mucosa and Peyer's patches. It could be concluded that AT or AC can replace 50% of berseem in the diet of Barki lambs without compromising lamb growth performance.

Effect of exogenous xylanase on rumen in vitro gas production and degradability of wheat straw.

The objective of this study was to determine effects of xylanase on in vitro gas production (GP) and in sacco degradability of wheat straw. Rumen fluid was obtained from three Mongolian native goats fitted with permanent rumen cannulas. The trial consisted of five doses (0, 0.5, 1.0, 1.5, 2.0 μL/g of substrate) of a commercial xylanase (Dyadic® xylanase PLUS, Dyadic International, Inc., Jupiter, FL, USA). For the in sacco degradability, different levels of xylanase enzyme were added directly onto 2 g of wheat straw in nylon bags and incubated in the rumen for 3, 6, 12, 24 and 48 h to estimate degradability of wheat straw. Total GP increased (P < 0.001) at all times of incubation at intermediate levels of xylanase. Methane production had a similar pattern at 3 and 12 h of incubation; increased linearly at 24 h of incubation, and was unaffected at 6 and 48 h of incubation. Rumen NH3 -N concentration increased linearly at 3 h and the highest values were observed with intermediate enzyme levels. All ruminal volatile fatty acids increased linearly with intermediate levels of the fibrolytic enzyme. The in sacco rate of dry matter degradation decreased linearly (P = 0.020) with increasing enzymes. Intermediate levels of xylanase improved rumen kinetic fermentation and degradability. The outcome of this research indicated that the application of xylanase enzyme could improve in vitro GP fermentation of wheat straw.

Transfer of dietary aflatoxin B1 to milk aflatoxin M1 and effect of inclusion of adsorbent in the diet of dairy cows

The objectives of this study were to investigate the transfer of aflatoxin from feed to milk and to evaluate the effects of Solis Mos (SM; Novus International Inc., St. Charles, MO) on milk aflatoxin M1, plasma biochemical parameters, and ruminal fermentation of dairy cows fed varying doses of aflatoxin B1 (AFB1). Three groups of 8 multiparous Holstein cows in late lactation (days in milk=271±29; milk yield=21.6±3.1kg/d) were assigned to 1 of 3 experiments in a crossover design. Cows in experiment 1 received no aflatoxin, cows in experiment 2 received 20 µg of AFB1/kg of dry matter, and cows in experiment 3 received 40 µg of AFB1/kg of dry matter. Cows in each experiment were assigned to 1 of 2 treatments: control or 0.25% SM. Each experiment consisted of 2 consecutive periods with the first 4 d (d 1 to 4) as adaptation, followed by AFB1 challenge for 7 d (d 5 to 11), and finally clearance for 5 d (d 12 to 16) in each period. Samples of total mixed ration and milk were collected on d 1, 2, and 10 to 14 of each period. Blood samples were collected from the coccygeal vein on d 1, 11, and 14 of each period. Rumen fluid was collected by oral stomach tube 2 h after the morning feeding on d 1 and 11 of each period. Adding SM to basal or AFB1-contaminated diets at 0.25% had no effect on lactation performance, liver function, or immune response. However, addition of SM improved antioxidative status, as indicated by increased plasma concentrations of superoxide dismutase and reduced malondialdehyde regardless of dietary AFB1 level. Addition of SM to the AFB1-free diet eliminated the background AFM1 in milk and increased total ruminal volatile fatty acid (99.6 vs. 94.2 mM) concentrations. Adding SM to the AFB1-contaminated diet in experiment 2 decreased the AFM1 concentration (88.4 vs. 105.3ng/L) and the transfer of aflatoxin to milk (0.46 vs. 0.56%), and increased total volatile fatty acid concentration (99.8 vs. 93.4 mM). Adding SM to diets with 40 µg/kg of AFB1 did not elicit changes in rumen parameters or AFM1 output. These results indicated that adding SM to diets containing 0 or 20 µg of AFB1/kg decreased milk AFM1 concentration, improved antioxidative status, and altered rumen fermentation, whereas adding SM to a diet containing 40 µg of AFB1/kg did not reduce AFB1 transfer but did increase the antioxidant status of the liver.

Effects of Crushed Linseed or Linseed Oil Supplementation on Performance of Dairy Goats and Fatty Acids Profile in Milk Top of Form

In a complete random block design, fifteen lactating Damascus goats (43.5±2 kg body weight) after the first week of lactation, were divided into 3 groups (five goats each) to evaluate effect of linseed or linseed oil as diet supplement on rumen parameters, milk production, milk composition and milk fatty acid profile in lactating goats. Animals were fed on a total mixed ration of 50% concentrates and 50% berseem clover (control), control ration+50g/head/day crushed linseed (LS) and control ration+20 ml/head/day linseed oil (LO) for 90 days. Dry matter intake was not affected by LO or LS. Ruminal volatile fatty acids (VFA) and butyrate proportions were increased (P 0.05) with experimental additives. Milk yield, milk protein and milk fat percent were higher (P 0.05) the proportion of C18:3N3 in milk fat. Total unsaturated fatty acids were increased (P<0.05) with LO; however, insignificantly increased with LS versus control. The proportions of conjugated linoleic acid increased (P<0.05) with addition of LO or LS in the diet. It may be concluded that adding the linseed or linseed oil to lactating goat rations improved the productivity of lactating goats and enhance milk components with no deleterious effects on general health. (S.M. Kholif, T.A. Morsy, O.H. Matloup, H.M. Ebeid, A.M. Kholif. Effects of Crushed Linseed or Linseed Oil Supplementation on Performance of Dairy Goats and Fatty Acid Profile in Milk. Life Sci J 2015;12(2s):94-99). (ISSN:1097-8135). http://www.lifesciencesite.com . 14

Effects of Feeding Programs Based on One or Two Milk Replacer Daily Meals on Growth, Solid Feed Intake and Rumen Fermentation and Development of Dairy Calves

Sixteen Holstein calves were used to study the effects of two feeding programs (FP) on growth, intake, rumen development and ruminal metabolism from birth to weaning. Two feeding programs based on milk replacer (MR) were tested: a once a day (OAD) MR (200 g/L) distribution vs. a standard twice a day (TAD) MR (125 g/L) distribution. All calves received water, wheat straw and a starter concentrate ad libitum. Four calves per group were slaughtered at weaning and rumen epithelium from the ventral sac was sampled for papillae (RP) density. Results showed that the FP had no effect on body weight of calves and total feed intake. From day 42 to day 56, ruminal pH was lower (P = 0.036) and ruminal oxydo-reducing potential was higher (P = 0.001) in OAD than TAD calves. Ruminal total volatile fatty acid (VFA) concentrations did not significantly differ between FP. From day 21 to day 63, butyrate ruminal concentration was significantly higher in OAD than TAD calves (5.17 vs 3.95 mmol/L). This probably explained the higher development of RP in calves fed once daily. Finally, the tested feeding system based on a once daily MR distribution affects the concentrate feeding pattern of calves.

Bacterial communities in the rumen of Holstein heifers differ when fed orchardgrass as pasture vs. hay.

The rich and diverse microbiota of the rumen provides ruminant animals the capacity to utilize highly fibrous feedstuffs as their energy source, but there is surprisingly little information on the composition of the microbiome of ruminants fed all-forage diets, despite the importance of such agricultural production systems worldwide. In three 28-day periods, three ruminally-cannulated Holstein heifers sequentially grazed orchardgrass pasture (OP), then were fed orchardgrass hay (OH), then returned to OP. These heifers displayed greater shifts in ruminal bacterial community composition (determined by automated ribosomal intergenic spacer analysis and by pyrotag sequencing of 16S rRNA genes) than did two other heifers maintained 84 d on the same OP. Phyla Firmicutes and Bacteroidetes dominated all ruminal samples, and quantitative PCR indicated that members of the genus Prevotella averaged 23% of the 16S rRNA gene copies, well below levels previously reported with cows fed total mixed rations. Differences in bacterial community composition and ruminal volatile fatty acid (VFA) profiles were observed between the OP and OH despite similarities in gross chemical composition. Compared to OP, feeding OH increased the molar proportion of ruminal acetate (P = 0.02) and decreased the proportion of ruminal butyrate (P < 0.01), branched-chain VFA (P < 0.01) and the relative population size of the abundant genus Butyrivibrio (P < 0.001), as determined by pyrotag sequencing. Despite the low numbers of animals examined, the observed changes in VFA profile in the rumens of heifers on OP vs. OH are consistent with the shifts in Butyrivibrio abundance and its known physiology as a butyrate producer that ferments both carbohydrates and proteins.

Effects of nitrate addition to a diet on fermentation and microbial populations in the rumen of goats, with special reference to Selenomonas ruminantium having the ability to reduce nitrate and nitrite.

This study investigated the effects of dietary nitrate addition on ruminal fermentation characteristics and microbial populations in goats. The involvement of Selenomonas ruminantium in nitrate and nitrite reduction in the rumen was also examined. As the result of nitrate feeding, the total concentration of ruminal volatile fatty acids decreased, whereas the acetate : propionate ratio and the concentrations of ammonia and lactate increased. Populations of methanogens, protozoa and fungi, as estimated by real-time PCR, were greatly decreased as a result of nitrate inclusion in the diet. There was modest or little impact of nitrate on the populations of prevailing species or genus of bacteria in the rumen, whereas Streptococcus bovis and S. ruminantium significantly increased. Both the activities of nitrate reductase (NaR) and nitrite reductase (NiR) per total mass of ruminal bacteria were increased by nitrate feeding. Quantification of the genes encoding NaR and NiR by real-time PCR with primers specific for S. ruminantium showed that these genes were increased by feeding nitrate, suggesting that the growth of nitrate- and nitrite-reducing S. ruminantium is stimulated by nitrate addition. Thus, S. ruminantium is likely to play a major role in nitrate and nitrite reduction in the rumen.

Effects of monensin and virginiamycin supplementation in finishing diets with distiller dried grains plus solubles on growth performance and digestive function of steers

Two trials were conducted to evaluate the influence of virginiamycin (26 mg/kg) and monensin (34 mg/kg) supplementation of a steam-flaked corn-based finishing diet containing 15% distiller dried grains plus solubles (DDGS) on growth performance and digestive function. In Trial 1, 135 steers (257 ± 21 kg) were used to evaluate treatment effects on 145-d growth performance. There were no treatment effects (P > 0.20) on dry matter intake (DMI). Antibiotic supplementation tended to increase average daily gain (ADG; 7%, P = 0.07); increased gain efficiency (11%, P < 0.01) and estimated dietary net energy (NE; 10%, P < 0.01). Carcass marbling score was greater (12%, P = 0.04) for virginiamycin vs. monensin. In Trial 2, three Holstein steers (300 ± 7 kg) were used in a 3 × 3 Latin square to evaluate treatment effects on digestion. Both monensin and virginiamycin depressed ruminal digestion of organic matter (OM; 6%, P < 0.01) and feed nitrogen (N, 15%, P = 0.03) and microbial protein synthesis (15%, P = 0.03). There were no treatment effects of total tract OM and N digestion. Antibiotic supplementation increased (2.3%, P = 0.02) ruminal pH, associated with decreased (7%, P = 0.04) ruminal volatile fatty acids (VFA) concentrations. It is concluded that monensin and virginiamycin supplementation of growing-finishing diets for feedlot cattle may enhance daily weight gain, gain efficiency and dietary energetics. These effects are associated with a shift towards great intestinal OM digestion and decreased ruminal degradation of feed N and microbial protein synthesis.

Improving the quality of rice straw by urea and calcium hydroxide on rumen ecology, microbial protein synthesis in beef cattle.

Four rumen-fistulated beef cattle were randomly assigned to four treatments according to a 4 × 4 Latin square design to study the influence of urea and calcium hydroxide [Ca(OH)2 ] treatment of rice straw to improve the nutritive value of rice straw. Four dietary treatments were as follows: untreated rice straw, 50 g/kg urea-treated rice straw, 20 g/kg urea + 20 g/kg calcium hydroxide-treated rice straw and 30 g/kg urea + 20 g/kg calcium hydroxide-treated rice straw. All animals were kept in individual pens and fed with concentrate at 0.5 g/kg of BW (DM), rice straw was fed ad libitum. The experiment was conducted for four periods, and each period lasted for 21 days. During the first 14 days, DM feed intake measurements were made while during the last 7 days, all cattle were moved to metabolism crates for total faeces and urine collections. The results revealed that 20 g/kg urea + 20 g/kg calcium hydroxide-treated rice straw improved the nutritive value of rice straw, in terms of dry matter intake, digestibility, ruminal volatile fatty acids, population of bacteria and fungi, nitrogen retention and microbial protein synthesis. Based on this study, it could be concluded that using urea plus calcium hydroxide was one alternative method to improve the nutritive value of rice straw, rumen ecology and fermentation and thus a reduction of treatment cost.

RUMINAL FERMENTATION AND BLOOD GLUCOSE AT LOW AND HIGH LEVEL INTAKE OF GROWING AND MATURE KACANG GOAT

This study was conducted to compare ruminal Volatile Fatty Acids (VFA) concentration andblood glucose in young and mature Kacang goats at different feeding levels. Eigth male young Kacanggoats weights at 12.75±2.68 kg (6-7 months) and male mature goat weights at ± 17.34±3.32 kg (8-12months) were used in this study. The pelleted complete feed was formulated to give 18,8% of CrudeProtein (CP) and 78.82% of total digestible nutrients (TDN). The experiment design was nested designexperimental 2x2 with 4 replications. The main factors (based on nested) were young and mature goatsand the second factor was low feeding (near maintenance level) and high feeding (2X maintenance).Data measured were daily feed intake, feed digestibilities, ruminal VFA concentration and bloodglucose. The data obtained were analyzed by using analysis of variance. The results showed that drymatter intake (DMI), digestible carbohydrates, digestible crude fiber, and digestible organic matter wasaffected by age (P 0.05). Ruminal VFA and blood glucose concentrations were found similar (P>0.05) neither in young and mature goats. However, VFA and concentration on the 3 and 6 h on high feeding aswell as blood glucose on 3 h in high feeding were higher than those on low feeding.

Preparation of Glycerol-Enriched Yeast Culture and Its Effect on Blood Metabolites and Ruminal Fermentation in Goats

The aim of this study was to isolate a glycerol-producing yeast strain from nature to prepare glycerol-enriched yeast culture (GY), and preliminarily evaluate the effects of GY on blood metabolites and ruminal fermentation in goats. During the trial, six isolates were isolated from unprocessed honey, and only two isolates with higher glycerol yield were identified by analysis of 26S ribosomal DNA sequences. One of the two isolates was identified as Saccharomyces cerevisiae, a direct-fed microbe permitted by the FDA. This isolate was used to prepare GY. The fermentation parameters were optimized through single-factor and orthogonal design methods to maximize the glycerol yield and biomass. The final GY contained 38.7±0.6 g/L glycerol and 12.6±0.5 g/L biomass. In vivo, eight castrated male goats with ruminal fistula were used in a replicated 4×4 Latin square experiment with four consecutive periods of 15 d. Treatments were as follows: control, LGY, MGY, and HGY with 0, 100, 200, and 300 mL GY per goat per day, respectively. The GY was added in two equal portions at 08∶00 and 17∶00 through ruminal fistula. Samples of blood and ruminal fluid were collected on the last one and two days of each period, respectively. Results showed that the plasma concentrations of triglyceride and total cholesterol were not affected by the supplemented GY. Compared with the control, goats supplemented with MGY and HGY had significantly higher (P<0.05) concentrations of plasma glucose and total protein, ruminal volatile fatty acid and molar proportion of propionate, and significantly lower (P<0.05) ruminal pH and ammonia nitrogen. These parameters changed linearly with increasing GY supplementation level (P<0.05). In conclusion, GY has great potential to be developed as a feed additive with dual effects of glycerol and yeast for ruminants.

Ration formulations containing reduced-fat dried distillers grains with solubles and their effect on lactation performance, rumen fermentation, and intestinal flow of microbial nitrogen in Holstein cows

Sixteen multiparous lactating Holstein cows were used in 2 experiments to evaluate the effects of reduced-fat dried distillers grains with solubles (RFDG) on milk production, rumen fermentation, intestinal microbial N flow, and total-tract nutrient digestibility. In experiment 1, RFDG was fed at 0, 10, 20, or 30% of diet dry matter (DM) to 12 noncannulated Holstein cows (mean ± standard deviation: 89±11d in milk and 674±68.2kg of body weight) to determine effects on milk production. In experiment 2, the same diets were fed to 4 ruminally and duodenally cannulated Holstein cows (mean ± standard deviation: 112±41d in milk; 590±61.14kg of body weight) to evaluate the effects on rumen fermentation, intestinal flow of microbial N, and total-tract nutrient digestibility. In both experiments, cows were randomly assigned to 4×4 Latin squares over 21-d periods. Treatments (DM basis) were (1) control (0% RFDG), (2) 10% RFDG, (3) 20% RFDG, and (4) 30% RFDG. Feed intake and milk yield were recorded daily. In both experiments, milk samples were collected on d 19 to 21 of each period for analysis of milk components. In experiment 2, ruminal pH was measured; samples of rumen fluid, duodenal digesta, and feces were collected on d 18 to 21. Microbial N was estimated by using purines and DNA as microbial markers. Milk yield was not affected by treatment and averaged 34.0±1.29kg/d and 31.4±2.81kg/d in experiments 1 and 2, respectively. Percentage of milk protein tended to increase in experiment 1; estimates were 3.08, 3.18, 3.15, and 3.19±0.06% when RFDG increased from 0 to 30% in the diets. However, milk protein concentration was not affected in experiment 2 and averaged 3.02±0.07%. Percentage of milk fat was not affected and averaged 3.66±0.05% and 3.25±0.14% in experiments 1 and 2, respectively. Total ruminal volatile fatty acids and ammonia concentrations were not affected by treatment and averaged 135.18±6.45mM and 18.66±2.32mg/dL, respectively. Intestinal microbial N flow was not affected by treatment; however, purines yielded higher estimates of flow compared with DNA markers. When averaged across treatments, intestinal flow of microbial N was 303 and 218±18g of N/d, using purines and DNA as the markers. Dry matter, organic matter, neutral detergent fiber, and nonfiber carbohydrate digestibility tended to increase with increasing inclusion of RFDG. Results from these experiments indicate that dairy rations can be formulated to include up to 30% RFDG while maintaining lactation performance, volatile fatty acids concentration, and intestinal supply of microbial N.

牛第一胃液のpHと揮発性脂肪酸濃度に及ぼす重曹含有食塩ブロック剤舐食給与の影響

牛第一胃液のpHと揮発性脂肪酸濃度に及ぼす重曹含有食塩ブロック剤舐食給与の影響

Comparison of enantiomers of organic acids for their effects on methane production in vitro

This study aimed to evaluate the effect of organic acids on in vitro fermentation characteristics. Four organic acids (tartaric, malic, fumaric and citric) and their enantiomers (L-tartaric, D-tartaric, DL-tartaric, L-malic and DL-malic) were analysed using in vitro batch culture incubations, at four concentrations (0, 5, 10 and 15 mM). Cumulative total gas and methane (CH4) production (mL/g DM) were measured at 6, 12 and 24 h; ammonia, pH, volatile fatty acids (VFA) and in vitro dry matter digestibility (IVDMD) were determined after 24 h of fermentation. Overall, addition of acids at 5 to 15 mM increased (P &lt; 0.0001) cumulative gas and CH4 production. No effect (P &gt; 0.10) of enantiomers, individual acid or interaction acid × concentration was detected at 12 and 24 h for cumulative gas or CH4 production. Addition of DL-malic, L-malic and fumaric acids increased (P &lt; 0.0001) the percentage of propionic acid in the ruminal fluid total VFA compared with all concentrations of the other organic acids or their enantiomers. Ammonia concentration was not affected (P ≥ 0.28) by the addition of organic acids, concentrations or interactions. These findings are evidence that ruminal microorganisms can metabolise both D- and L-enantiomers of organic acids. None of the organic acids and their enantiomers at four different concentrations demonstrated potential as CH4 mitigation agents.

The Effect of Starch, Inulin, and Degradable Protein on Ruminal Fermentation and Microbial Growth in Rumen Simulation Technique

A rumen simulation technique 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 inulin) supplemented with 0 g/d (low RDP) or 1.56 g/d (high RDP) sodium caseinate. No significant differences existed among dietary treatments in the apparent disappearance of dietary nutrients except for dietary N, which increased with increased dietary RDP (P<0.001). Compared with starch, inulin treatments reduced the molar proportion of acetate (P<0.001), the acetate:propionate ratio (P<0.001), and methane production (P=0.006), but increased the butyrate proportion (P<0.001). Increased dietary RDP led to increases in production of total volatile fatty acid (P=0.014) and methane (P=0.050), various measures of N (P≤0.046), and 16s rDNA copy numbers of Ruminococcus flavefaciens (P≤0.010). Non-fibre carbohydrate source did not affect daily microbial N flow regardless of dietary RDP, but ammonia N production was lower for inulin than for starch treatments under high RDP conditions (P<0.001). Compared with starch treatments, inulin depressed the copy numbers of Fibrobacter succinogenes in solid fraction (P=0.023) and R. flavefaciens in liquid (P=0.017) and solid fractions (P=0.007), but it increased the carboxymethylcellulase activity in solid fraction (P=0.045). Current results suggest that starch and inulin differ in ruminal volatile fatty acid fermentation but have similar effects on ruminal digestion and microbial synthesis in vitro, although inulin suppressed the growth of partial ruminal cellulolytic bacteria.

The production of acetate, propionate and butyrate in the rumen of sheep: fitting models to 14C- or 13C-labelled tracer data to determine synthesis rates and interconversions

A procedure is described for solving an open, fully exchanging, three-compartment model representing ruminal volatile fatty acids (VFA) kinetics in sheep. This model was solved using results from a published study in which labelled VFA, viz. 1-14C-acetate (Ac), 1-14C-propionate (Pr) and 1-14C-butyrate (Bu), were infused individually at a constant rate for 240 min into the rumen of sheep on different occasions. During the tracer infusions, the sheep were given 75 g of lucerne (Medicago sativa) every hour. The patterns of increasing specific radioactivity (SA) during the infusions were described by differential equations that were solved using the computer software, WinSAAM. This linear kinetic analysis gave estimates of the rates of synthesis and absorption of Ac, Pr and Bu and the carbon interconversions between each acid. The sizes of the Ac, Pr and Bu compartments (10.5, 3.9 and 2.1 g C respectively), were also estimated, which is not possible with commonly used algebraic analyses. The model output showed that tracer : tracee equilibrium (plateau SA) had not been reached in the Ac, Pr and Bu compartments during the 240 min of tracer infusion and the algebraic method of analysis used in the original study was therefore compromised. The procedures described here eliminated this source of error; in addition, confidence in the model solution was improved because all data representing the build-up to plateau SA were used, rather than just estimates of ‘plateau’ SA. After accounting for VFA interconversions, the rates of VFA absorption (or incorporation into other materials such as microbial polymers or methane) were 85, 48 and 49 g C/day, or 78%, 91% and 73% of the total production of each VFA, respectively. The variability in the observed SA responses to the tracer infusions was relatively large and this is discussed. Model solutions using the linear kinetic analysis and the previously widely used algebraic analyses are compared. The effect of positional labelling in tracer VFA is also discussed in the light of evidence that the rate of absorption of Pr may be overestimated when [1-14C]-Pr rather than [2-14C]-Pr or uniformly labelled [14C]-Pr is used as the Pr tracer.

Milk production is unaffected by replacing barley or sodium hydroxide wheat with maize cob silage in rations for dairy cows

Starch is an important energy-providing nutrient for dairy cows that is most commonly provided from cereal grains. However, ruminal fermentation of large amounts of easily degradable starch leads to excessive production and accumulation of volatile fatty acids (VFA). VFA not only play a vital role in the energy metabolism of dairy cows but are also the main cause of ruminal acidosis and depressed feed intake. The aim of the present study was to compare maize cob silage (MCS) as an energy supplement in rations for dairy cows with highly rumen-digestible rolled barley and with sodium hydroxide wheat (SHW), which has a higher proportion of by-pass starch than barley. Two studies were carried out: (1) a production study on 45 Danish Holstein cows and (2) an intensive study to determine digestibilities, rumen fermentation patterns and methane emission using three rumen-cannulated Danish Holstein cows. Both studies were organised as a 3×3 Latin square with three experimental periods and three different mixed rations. The rations consisted of grass-clover silage and maize silage (~60% of dry matter (DM)), rapeseed cake, soybean meal, sugar beet pulp and one of three different cereals as a major energy supplement: MCS, SHW or rolled barley (~25% of DM). When MCS replaced barley or SHW as an energy supplement in the mixed rations, it resulted in a lower dry matter intake; however, the apparent total tract digestibilities of DM, organic matter, NDF, starch and protein were not different between treatments. The energy-corrected milk yield was unaffected by treatment. The fat content of the milk on the MCS ration was not different from the SHW ration, whereas it was higher on the barley ration. The protein content of the milk decreased when MCS was used in the ration compared with barley and SHW. From ruminal VFA patterns and pH measures, it appeared that MCS possessed roughage qualities with respect to rumen environment, while at the same time being sufficiently energy rich to replace barley and SHW as a major energy supplement for milk production. The environmental impact, expressed as methane emissions, was not different when comparing MCS, SHW and barley.

Effects of a Bacteria-Based Probiotic on Ruminal pH, Volatile Fatty Acids and Bacterial Flora of Holstein Calves

ABSTRACTTwelve ruminally cannulated Holstein calves (age, 12 ± 3 weeks) were used to identify the effect of a probiotic comprised of Lactobacillus plantarum, Enterococcus faecium and Clostridium butyricum on ruminal components. The calves were adapted to a diet containing a 50% high-concentrate (standard diet) for 1 week, and then, the probiotic was given once daily for 5 days (day 1–5) at 1.5 or 3.0 g/100 kg body weight to groups of four calves each. Four additional calves fed the standard diet without probiotic served as the corresponding control. Ruminal pH was measured continuously throughout the 15-day experimental period. Ruminal fluid was collected via a fistula at a defined time predose and on days 7 and 14 to assess volatile fatty acid (VFA), lactic acid and ammonia-nitrogen concentrations, as well as the bacterial community. The probiotic at either dose improved the reduced 24-hr mean ruminal pH in calves. The circadian patterns of the 1 hr mean ruminal pH were identical between the probiotic doses. In both probiotic groups, ruminal lactic acid concentrations remained significantly lower than that of the control. Probiotic did not affect ruminal VFA concentrations. L. plantarum and C. butyricum were not detected in the rumen of calves given the high-dose probiotic, whereas Enterococcus spp. remained unchanged. These results suggest that calves given a probiotic had stable ruminal pH levels (6.6–6.8), presumably due to the effects of the probiotic on stabilizing rumen-predominant bacteria, which consume greater lactate in the rumen.

Effects of inoculation with rumen fluid on nutrient digestibility, growth performance and rumen fermentation of early weaned lambs

Thirty weaned male lambs (28 days old) with live weight of 10.3kg were randomly assigned to one of 3 treatments for a 56 days feeding period to study effects of inoculation with rumen fluid from mature sheep on growth performance and rumen fermentation. Treatments consisted of: (1) starter grain ration (SGR, control), (2) fed SGR and inoculated with 100ml fresh rumen fluid (FRF) daily for 7 days and (3) fed SGR and inoculated with 100ml lyophilized rumen fluid (LRF) for 7 days. Results showed that there were no differences in DM intake, apparent digestibilities of crude protein and acid detergent fiber (ADF), ruminal pH, and ruminal concentrations of ammonia N and total volatile fatty acid (VFA). However, both inoculations decreased feed conversion rate (FCR) (P<0.01). Inoculation of FRF increased average daily gain (ADG), apparent digestibilities of DM (P<0.01) and neutral detergent fiber (NDF) (P<0.05), while inoculation of LRF increased apparent digestibility of fat (P<0.05). There were significant interactions between treatment and sampling time for all individual ruminal VFA (P<0.05), except butyric acid and the ratio of acetic to propionic acid (P<0.001). In conclusion, FRF inoculation was beneficial to improving growth performance of lambs during the transition. Further research is needed to explain the mechanism of action of the FRF as probiotic.

Evaluation of predictions of volatile fatty acid production rates by the Molly cow model

Predicting ruminal volatile fatty acid (VFA) production is important, as VFA are an energy source to the animal, affect nutrient partitioning, and dictate methane production. The VFA production submodel in the Molly cow model was evaluated using data from 8 publications that reported VFA production rates for cattle. Evaluations were conducted with ruminal water balance predictions enabled and the ruminal VFA stoichiometry coefficients set to “mixed” for all diets, or “mixed” when forage represented between 20 and 80% of the diet, “concentrate” when <20% forage, or “forage” when >80% forage. Prediction errors were relatively insensitive to changes in VFA coefficients by diet type. Root mean square prediction errors (RMSPE) were 63, 63, and 49% for acetate, propionate, and butyrate production rates, respectively. A large proportion of the error was slope bias for acetate and butyrate, and a modest proportion for propionate. Because interconversions between acetate and propionate represent approximately 15% of the variation in net production rates, lack of such consideration in the model may contribute to the substantial model prediction errors. The potential of using thermodynamic equations to predict interconversions was assessed using observed ruminal pH and VFA concentrations from 2 studies and assuming constant hydrogen pressure and concentrations of CO2, H2O, adenosine diphosphate, ATP, and inorganic P. Rate constants for conversion of acetate to propionate and propionate to acetate were derived independently from the control treatments and used to predict the fluxes for the other treatment. The observed changes in VFA concentrations and pH explained the observed changes in conversion of acetate to propionate, but overpredicted the change in the propionate to acetate flux in one study. When applied to the other study, the equations predicted the increase in propionate to acetate flux, but failed to predict the observed reduction in acetate to propionate flux. The inability to predict responses accurately may be due to a lack of data for controlling factors other than pH and VFA concentrations.