VFA Molar Proportions Research Articles

Performance of dairy cows offered silages produced from grass swards harvested on either three or five occasions during the growing season

The nutritive value of grass silage can be improved by harvesting herbage at a less mature growth stage, which in practice usually involves more frequent harvests. This study examined the performance of dairy cows offered grass silages produced from perennial ryegrass (Lolium perenne) based swards harvested at 2 different frequencies during the growing season (3-harvest (3H) vs. 5-harvest (5H)). Thirty-four mid-lactation (av. 147 d in milk) dairy cows (30 multiparous, 4 primiparous) were offered either 3H or 5H silages in a continuous design (21 wk) experiment. Within each treatment cows were offered silage from each harvest (in harvest number order) for a pre-determined number of days in proportion to herbage DM yield at each harvest. Silages were offered ad libitum while a common concentrate was offered to all cows at 12.0 kg per cow/d over the first 15 wk of the study, 8.0 kg per cow/d during wk 16 -19 and 6.0 kg cow/d during wk 20 - 21. Total yield of herbage harvested over the season from within 3H and 5H were 12.6 and 11.2 t DM/ha, respectively. Across all harvests the mean ME and CP concentration of silages were 10.9 MJ/kg DM and 131 g/kg DM for 3H, and 11.5 MJ/kg DM and 152 g/kg DM for 5H. Silage DMI was greater for cows offered 5H silages compared with 3H silages (14.1 vs. 11.7 kg/d, respectively). Cows offered 5H silages had a greater daily milk yield (33.5 vs. 31.9 kg) and ECM yield (37.4 vs. 35.6 kg) compared with cows offered 3H silages. Treatment had no effect on milk fat or protein concentration. Cows offered 5H silages produced milk with greater concentrations of CLA and n-3 fatty acids. Treatment had no effect on mean BW or BCS, or on efficiency metrics such as milk yield or ECM yield per kg of DMI. Molar proportions of VFA in ruminal fluid differed between the treatments, with cows offered 3H silages having higher proportion of total butyrate (15.9 vs. 14.4% of total VFA) and lower total valerate (3.2 vs. 3.7% of total VFA) compared with those offered 5H. The acetate: propionate and acetate plus butyrate: propionate ratios were unaffected by treatment. In conclusion, increasing herbage harvesting frequency from 3 to 5 times per year improved the nutritional value of the resulting silages, and this led to higher silage DMI, milk yield and ECM yield. However, overall production efficiency (ECM/DMI) was unaffected by treatment.

Characterization of various wheat types and processing methods using in vitro ruminal batch cultures

This study investigated the effect of kernel hardness, processing method, and their interaction on particle size, dry matter (DM) disappearance (DMD), and fermentation characteristics of wheat grain in batch cultures. The study was a completely randomized design with 3 wheat classifications (soft, medium, hard) × 3 processing methods (grinding, dry- and temper-rolling). Fifty-five wheat samples were characterized for chemical traits and classified for kernel hardness. Samples were either ground through 1-mm screen, dry-rolled or temper-rolled to a constant processing index (PI) of 0.80. In vitro gas production (GP) kinetics, fermentation characteristics and DMD at 6, 24 and 48 h of incubation were measured. Crude protein (CP) (g/kg) was lower and starch (g/kg) was higher for soft than medium and hard wheat. The PSD of rolled wheat was affected (P < 0.01) by a wheat hardness × processing interaction. With dry-rolling, soft wheat had more particles retained on the 2.36-mm sieve and less on the 1.18-mm sieve, while, with temper-rolling, soft wheat had more particles retained on the 3.35-mm sieve and less on the 2.36-mm sieve than those for dry- or temper-rolled medium and hard wheat. Kernel hardness × processing was observed (P < 0.01) for DMD and CPD after 24 h and 48 h of incubation; the DMD and CPD were higher (P < 0.01) with dry- than temper-rolled hard or medium wheat, but no differences in DMD and CPD were observed between dry- and temper-rolled soft wheat. A kernel hardness × processing interaction was also noted for total VFA production and molar proportions of propionate after 24 h of incubation (P < 0.05). Dry-rolled soft wheat had a higher (P = 0.04) total VFA concentration and molar proportion of propionate after 24 h of incubation as compared to dry-rolled hard wheat. Compared to grinding, VFA concentrations and proportion of propionate were all reduced by both dry- and temper rolling with the magnitude of these differences generally being greater for soft as compared to medium and hard wheat. In conclusion, regardless of kernel hardness, PSD of dry- and temper-rolled wheat had a significant impact on DMD. Tempering was more effective at reducing the generation of fine particles than dry-rolling, particularly with hard wheat, a factor that may reduce the risk of digestive disturbances in ruminants fed wheat.

180 Effects of Forage Mixtures on Rumen Fermentation Parameters as Assessed by Continuous Culture

Abstract The impact of using diverse forage mixtures on rumen performance is poorly characterized. The objective of this study was to evaluate the impact of feeding diverse pastures on rumen performance using in vitro continuous culture fermenters. Treatments were assessed using a 4 x 4 Latin square design. Each 10-d period included 7-d of adaption followed by 3-d of sample collection. Dietary treatments (DM basis) included 1) 50% orchardgrass + 50% alfalfa (OG-ALF); 2) 50% OG-ALF + 50% red clover (RC); 3) 50% OG-ALF + 50% pearl millet (MIL); and 4) 50% OG-ALF + 50% sorghum x sudangrass (SUD). Forage diets (131 g DM/ fermenter/ d) were divided into 4 portions/d (33%, 0600 h; 17%, 0720 h; 33%,1800 h; 17%, 1920 h). Fermenter pH measurements were collected every min for the entire experiment. Methane concentrations were measured using a gas probe and recorded twice daily (0530 h,1730 h) in triplicate on d 7, 8, 9, and 10. Daily total effluent samples were collected on d 8, 9, and 10 for VFA analysis. Results were analyzed using PROC MIXED of SAS. There were no differences in total VFA concentrations (P = 0.08), molar proportions (P = 0.22), or individual VFA ratios (P &amp;gt; 0.05) as a result of treatment. Fermenter pH did not differ between fermenters as a result of treatment (P &amp;gt; 0.05). Fermenters receiving OG-ALF had the greatest methane concentration (50.8 mg/dL), which was higher (P &amp;lt; 0.05) than methane concentrations in fermenters receiving MIL (6.2 mg/dL), SUD (6.9 mg/dL), or RC (21.2 mg/dL). Methane concentrations from the MIL, SUD and RC treatments did not differ (P &amp;gt; 0.05). This indicates that binary forage mixtures may have lower nutritional value compared with diverse mixtures, and this diversification could provide nutritional benefits.

Supplementation of Jengkol Peel on VFA Molar Proportion, Methane Production, and Hydrogen Balance in Vitro

This research was designed to study about effects of supplementation jengkol (Archidendron jiringa) peel powder on VFA molar proportion, production of methane, and hydrogen balance in vitro. The experiment used randomized block design with 4 treatments (0%, 2%, 4%, 6%) and 4 replications. The research observed of VFA molar proportion, production of methane, and hydrogen balance. Data were analyzed using Analysis of Variance (ANOVA), and the Duncan Multiple Range Test examined the differences among treatment means. The results showed that the supplementation of jengkol (A. jiringa) peel powder until 6% did not affect (P&gt;0.05) VFA molar proportion but the treatment without supplementation of jengkol (A. jiringa) peel powder had the highest (P&lt;0.05) methane and H2 production. It was concluded that the supplementation of jengkol (A. jiringa) peel powder until 6% decreased methane and hydrogen production but did not affect on VFA molar proportion.

Frequency of diet delivery to dairy cows: Effect on nutrient digestion, rumen fermentation, methane production, nitrogen utilization, and milk production

The objective of this study was to examine the effect of frequency of diet delivery to dairy cows on nutrient digestion, rumen fermentation, milk production, nitrogen utilization, enteric methane emission, and manure methane production potential. Twelve lactating cows were used in a replicated 3 × 3 Latin square design (35-d period) and offered a TMR ad libitum [56:44 ratio of forage to concentrate, dry matter (DM) basis] once (0930 h), twice (0930 and 2130 h), or 4 times daily (0930, 1300, 1630, and 2130 h). Frequency of diet delivery did not affect intake or apparent total-tract digestibility of DM and nutrients. Likewise, milk production, milk composition (fat, protein, and lactose), and milk production efficiency (kg of milk/kg of DM intake or g of milk N/g of N intake) were not changed by frequency of diet delivery. Although diurnal variation of ruminal pH, total VFA, and acetate molar proportion were influenced by frequency of diet delivery, daily average ruminal pH, total VFA, and acetate and propionate molar proportions were not affected by frequency of diet delivery. Daily enteric CH4 emission averaged 534 g/d and was not changed by frequency of diet delivery. Methane energy losses (on gross energy intake basis) were lower when cows received the diet once daily (5.8%) versus twice or 4 times daily (6.1%). Urinary N excretion was higher for cows receiving the diet 4 times daily compared with cows receiving the diet once or twice daily (36 vs. 34% of N intake). Frequency of diet delivery had no influence on manure volatile solids excretion or maximal CH4 production potential. Results from this study show that delivering the diet once daily reduces enteric CH4 energy losses compared with twice or 4 times daily, whereas urinary N losses increased by delivering the diet 4 times daily compared with once or twice daily. However, milk production and maximal manure CH4 emission potential were not affected by frequency of diet delivery.

In dairy cattle, the stomach tube method is not a feasible alternative to the rumen cannulation method to examine in vitro gas and methane production

The objectives were to compare in vitro gas and methane (CH4) production kinetics using rumen fluid as inoculum collected via the rumen cannulation (CAN) method and with the oral stomach tube (OST) method, and to test for interactions between the type of inoculum and the diet fed to the donor cows as well as with the substrate incubated. Four rumen-cannulated lactating Holstein-Friesian cows (364 ± 20 days in milk, 690 ± 37 kg of bodyweight, 22.0 ± 6.0 kg of milk/day; mean ± SD) were blocked in pairs balanced over treatment sequence in a 2 × 2 crossover design. Cows were fed a total mixed ration consisting of 40% maize silage, 30% grass silage, and 30% concentrate on dry matter (DM) basis, with or without dietary linseed oil (a difference of 23 g/kg DM in fat content between the two diets). Rumen fluid was collected using the CAN and the OST method from each cow at d 17 of each experimental period. Subsequently, a 48 h gas production (GP) experiment was performed in which rumen fluid from each donor cow × rumen fluid sampling method was incubated with three substrates, viz. amygold, lupine, and wheat. The pH of the rumen fluid obtained using the OST method was higher than that of the rumen fluid obtained using the CAN method, whereas the total VFA concentration was lower and the VFA molar proportions unaffected. Multiple diet × inoculum and substrate × inoculum interactions in in vitro GP and CH4 kinetic parameters were observed. Furthermore, several GP and CH4 kinetic parameters, including total GP, absolute, asymptotic, and relative CH4 production, and maximum CH4 production rate, were higher for the CAN method compared with the OST method. The opposite was observed for, amongst others, the switching characteristic of the CH4 production profile and the half time to reach maximum asymptotic GP of the insoluble fraction. In conclusion, rumen fluid obtained using the OST sampling technique differs from that obtained using the CAN method, resulting in differences in in vitro gas and CH4 production profiles between both methods. The multiple interactions indicate that the rumen fluid sampling method can affect the in vitro GP and CH4 kinetics found for diet and for substrate. The results of this study therefore do not support the OST method as a feasible alternative to the CAN method in dairy cattle to examine in vitro gas and CH4 production.

Evaluation of Brassica carinata meal on ruminant metabolism and apparent total tract digestibility of nutrients in beef steers1,2.

Brassica carinata is a new oilseed crop with the potential of producing high-quality jet biofuel. A high-protein meal (~40% crude protein) is obtained as a byproduct of hexane-solvent oil extraction; however, limited research is available on the use of this meal as a protein supplement for beef cattle. A duplicated 4 × 4 Latin square design was used to determine the effects of supplementation with B. carinata meal on ruminal fermentation, digestibility, and blood metabolites in beef cattle consuming bahiagrass hay (Paspalum notatum Flüggé), compared with frequently used protein supplements. Eight Angus crossbred steers (473 ± 119 kg initial BW) were randomly allocated to 8 pens, over 4 periods of 28-d each. Within period, steers were assigned to 1 of 4 treatments: 1) 1.62 kg/d cottonseed meal (CSM); 2) 2.15 kg/d dry distillers grains plus solubles (DDGS); 3) 1.39 kg/d B. carinata meal pellets (BCM); or 4) 1.17 kg/d soybean meal (SBM), supplemented daily, on an isonitrogenous basis. Steers had ad libitum access to bahiagrass hay and water. Intake was measured using the GrowSafe system. Following a 14-d adaptation, feed and fecal samples were collected to determine apparent total tract nutrient digestibility using indigestible NDF as an internal marker. Blood and ruminal fluid samples were collected before providing the protein supplements and then every 3 h, during a 24-h period, to analyze urea nitrogen (PUN) and glucose in plasma, as well as ruminal pH, ammonia nitrogen (NH3-N), and VFA concentrations. Data were analyzed using PROC MIXED of SAS with repeated measures. Model included the fixed effects of treatment, time, treatment × time, square, and period, and the random effects of steer(square) and steer(treatment). No effect of treatment (P > 0.05) was observed for pH, NH3-N, or glucose concentration. An effect of treatment (P < 0.01) was observed for PUN, with steers receiving SBM having greater concentrations. A treatment × time interaction was observed (P < 0.05) for total VFA concentration, acetate to propionate ratio, and molar proportions of acetate, propionate, butyrate, and valerate. Steers consuming SBM had greater molar proportions of branched-chain VFA (P < 0.01) compared with CSM and DDGS. There was no effect of treatment (P > 0.05) on intake or apparent total tract digestibility of nutrients. Brassica carinata performed similarly to commonly used protein supplements indicating its viability as a protein supplement for beef cattle.

Effects of branched-chain volatile fatty acids on lactation performance and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows

Branched-chain volatile fatty acids (BCVFA) supplements could promote lactation performance and milk quality by improving ruminal fermentation and milk fatty acid synthesis. This study was conducted to evaluate the effects of BCVFA supplementation on milk performance, ruminal fermentation, nutrient digestibility and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows. A total of 36 multiparous Chinese Holstein cows averaging 606±4.7 kg of BW, 65±5.2 day in milk (DIM) with daily milk production of 30.6±0.72 kg were assigned to one of four groups blocked by lactation number, milk yield and DIM. The treatments were control, low-BCVFA (LBCVFA), medium-BCVFA (MBCVFA) and high-BCVFA (HBCVFA) with 0, 30, 60 and 90 g BCVFA per cow per day, respectively. Experimental periods were 105 days with 15 days of adaptation and 90 days of data collection. Dry matter (DM) intake tended to increase, but BW changes were similar among treatments. Yields of actual milk, 4% fat corrected milk, milk fat and true protein linearly increased, but feed conversion ratio (FCR) linearly decreased with increasing BCVFA supplementation. Milk fat content linearly increased, but true protein content tended to increase. Contents of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0 and C15:0 fatty acids in milk fat linearly increased, whereas other fatty acids were not affected with increasing BCVFA supplementation. Ruminal pH, ammonia N concentration and propionate molar proportion linearly decreased, but total VFA production and molar proportions of acetate and butyrate linearly increased with increasing BCVFA supplementation. Consequently, acetate to propionate ratios linearly increased. Digestibilities of DM, organic matter, CP, NDF and ADF also linearly increased. In addition, mRNA expressions of peroxisome proliferator-activated receptor γ, sterol regulatory element-binding factor 1 and fatty acid-binding protein 3 linearly increased, mRNA expressions of acetyl-coenzyme A carboxylase-α, fatty acid synthase and stearoyl-CoA desaturase quadratically increased. However, lipoprotein lipase mRNA expression was not affected by treatments. The results indicated that lactation performance and milk fat synthesis increased with BCVFA supplementation by improving ruminal fermentation, nutrient digestibility and mRNA expressions of genes related to milk fat synthesis.

Effects of exogenous fibrolytic enzyme supplementation to diets with different NFC/NDF ratios on the growth performance, nutrient digestibility and ruminal fermentation in Chinese domesticated black goats

This study was conducted to evaluate the effects of exogenous fibrolytic enzymes (EFE) supplementation into diets with different non-fiber carbohydrates (NFC)/neutral detergent fiber (NDF) ratios on growth performance, nutrient digestibility, ruminal fermentation, and microbiome in Chinese domesticated Lezhi black goats. Treatments were 2 × 2 factorial arrangement of diets using low vs. high NFC/NDF ratios (1.06 or 1.66) and with or without EFE supplementation (0 or 0.4 g cellulase and xylanase/kg dry matter of diet). Sixty four Lezhi black goats (11 ± 0.8 kg of live weight) were randomly assigned to the four treatments. High NFC/NDF ratio and EFE supplementation achieved greater average daily gain and improve feed conversion ratio (P < .05). The same treatments also significantly increased digestibility of organic matter (OM), acid detergent fiber (ADF) and NDF. In addition, the high NFC/NDF ratio diet, but not the EFE supplement, improved digestibility of crude protein (CP) and reduced ruminal pH (P < .001). Both high NFC/NDF ratio and EFE supplement decreased ruminal NH3-N concentrations significantly (P < .001), and increased the production of rumen total volatile fatty acids (VFA, P < .001), especially the molar proportion of propionate (P < .05). They reduced the molar proportion of acetate and thus the ratio of acetate to propionate (A: P) (P < .05). Both the high NFC/NDF ratio and the EFE supplement elevated the levels of microbial crude proteins (P < .01). Importantly, the combination of high NFC/NDF ratio and the EFE supplement diet raised the content of the microbial crude proteins to the highest levels among the 4 different treatment groups (P = .012). However, the high NFC/NDF ratio and the EFE supplementation had different impacts on fiber degrading activities. The high NFC/NDF ratio diet decreased, while EFE supplementation increased, the activities of cellulase and xylanase (P < .05). Among the three cellulytic bacteria detected (Ruminococcus albus, Ruminococcus flavefaciens, Fibrobacter succinogenes), only the abundance of Fibrobacter succinogenes was significantly decreased with the high NFC/NDF ratio (P = .004). These results illustrate that the diet with a high NFC/NDF ratio and EFE supplementation can improve ADG, feed conversion ratio and nutrient utilization in Lezhi black goats. These improvements are likely attributed to the elevated production of microbial crude proteins and a shift in the molar proportions of VFA in the rumen, rather than increase of cellulolytic bacteria in the rumen microbiota.

Influence of dietary cation–anion difference in finishing diets fed to Holstein steers during periods of high ambient temperature on feedlot performance and digestive function

ABSTRACTOne hundred twenty-six Holstein steers (457.1 ± 27.5 kg BW) were used in a 127-d experiment to evaluate the influence of dietary cation–anion difference (DCAD) on growth performance and carcass characteristics. Treatments consisted of steam-flaked corn-based diets supplemented to provide DCAD of 34, 84 or 134 mEq/kg diet DM. There was no treatment effect (P > .20) on ADG, DMI, gain efficiency or dietary NE. Six Holstein steers (196 ± 3 kg) with cannulas in rumen and proximal duodenum were used in a replicated 3 × 3 Latin Square design to evaluated treatment effects on digestion characteristics. The DCAD did not affect (P > .20) ruminal or total digestion of OM, NDF, starch and N, or ruminal pH and VFA molar proportions. It is concluded that increasing DCAD of Holstein steers fed a conventional steam-flaked corn-based diet under conditions of high ambient temperature will not enhance growth performance.

553 Effects of pentacyclic triterpenes on in vitro fermentation of bahiagrass hay and a high-grain substrate

Triterpenes are the most representative group of phytochemicals, comprising more than 20,000 recognized molecules. The diversity of triterpenes is highly associated with their broad range of pharmacological effects. Previous studies have demonstrated their anti-microbial potential. Our objective was to determine potential effects of pentacyclic triterpenes (TT) on in vitro batch culture fermentation of bahiagrass hay and a high-grain substrate. A randomized complete block design was used to determine the effects of increasing concentrations of the following TT types: oleanolic acid (OA), ursolic acid (UA) and malsinic acid (MAL) on in vitro fermentation of bahiagrass hay (BGH) or a high-grain substrate (HG) comprised of 43% soybean hulls pellets, 42% corn gluten feed pellets, and 15% peanut hulls (DM basis). Treatments were arranged as a 4 × 3 factorial with 4 doses (0, 4, 25 and 100 mg/L of incubation volume) for each of the 3 TT types. Four ruminally cannulated crossbred steers (362 ± 30 kg BW) were used as ruminal fluid donors. Two steers were fed HG ad libitum, while the other two steers were fed BGH ad libitum for at least 14 d prior to the first incubation day. Each replicate d, 125-mL serum bottles containing 50 mL of a 4:1 buffer:ruminal fluid inoculum and 0.63 g of BGH substrate (DM basis) were incubated for 48 h, and a 2:1 buffer:ruminal fluid inoculum and 0.63 g of HG substrate (DM basis) were incubated for 24 h. Three d (block) of incubation were performed. In vitro OM digestibility (IVOMD) was determined in a separate set of tubes. Data were analyzed using PROC MIXED of SAS with the fixed effect of treatment, and random effect of incubation day. No effect was observed (P>0.05) on total gas production, IVOMD, NH3-N concentration and H2S production. There was no effect (P>0.05) of any TT types or doses on concentrations or molar proportions of VFA. No effect (P>0.05) of TT type or dose were observed on acetate:propionate ratio (A:P). In conclusion, the acid form of the pentacyclic triterpenes did not affect ruminal fermentation of either substrate. Future studies should focus on increasing the solubility of these pentacyclic triterpenes by using a sodium salt.

Compositional mixed modeling of methane emissions and ruminal volatile fatty acids from individual cattle and multiple experiments.

The aim of the study was to investigate the association of methane (CH) yields (g/kg DMI) with rumen VFA molar proportions and animal and diet-related covariates from individual animals and multiple experiments. The dataset available consisted of 284 measurements of CH yields for beef cattle from 6 experiments measured in indirect respiration chambers. A compositional modeling approach was employed where VFA measurements were considered as a whole, instead of in isolation, emphasizing their multivariate relative scale. The analysis revealed expected close groupings of acetate and butyrate; propionate and valerate; iso-butyrate and iso-valerate. Linear mixed models were then fitted to examine relationships between CH yield and VFA, represented by meaningful log-contrasts of components called compositional balances, while accounting for other animal and diet-related covariates and random variability between experiments. A compositional balance representing (acetate × butyrate)/propionate best explained the contribution of VFA to variation in CH yield. The covariates DMI, forage:concentrate proportion (expressed as a categorical variable diet type: high concentrate, mixed forage:concentrate or high forage), and diet ME were also statistically significant. These results provided new insights into the relative inter-relationships among VFA measurements and also between VFA and CH yield. In conclusion, VFA molar proportions as represented by compositional balances were a significant contributor to explaining variation in CH yields from individual cattle.

Effect of dietary roughage level on chewing activity, ruminal pH, and saliva secretion in lactating Holstein cows

Increasing dietary roughage level is a commonly used strategy to prevent subacute ruminal acidosis. We hypothesized that high-roughage diets could promote chewing activity, saliva secretion, and hence more alkaline to buffer rumen pH. To verify the hypothesis, 12 multiparous Holstein cows in mid lactation were randomly allocated to 4 treatments in a triplicated 4 × 4 Latin square experiment with one cow in each treatment surgically fitted with a ruminal cannula. Treatments were diets containing 40, 50, 60, or 70% of roughage on a DM basis. Increasing dietary roughage level decreased DM, CP, OM, starch, and NEL intake, increased ADF intake, and decreased milk yield linearly. Intake of NDF was quite stable across treatments and ranged from 7.8 to 8.1 kg/d per cow. Daily eating time increased linearly with increased roughage level. The increase in eating time was due to increased eating time per meal but not number of meals per day, which was stable and ranged from 8.3 to 8.5 meals per day across treatments. Increasing dietary roughage level had no effect on ruminating time (min/d), the number of ruminating periods (rumination periods per d), and chewing time per ruminating period (min/ruminating period). Ruminating time per kilogram of NDF intake and total chewing time per kilogram of ADF intake were similar across treatments (57.4 and 183.8 min/kg, respectively). Increasing dietary roughage level linearly increased daily total chewing time; linearly elevated the mean, maximum, and minimum ruminal pH; and linearly decreased total VFA concentration and molar proportion of propionate in ruminal fluid. Saliva secretion during eating was increased, the secretion during rumination was unaffected, but the secretion during resting tended to decrease with increased dietary roughage level. As a result, total saliva secretion was not affected by treatments. In conclusion, the results of the present study did not support the concept that high-roughage diets elevated ruminal pH through increased salivary recycling of buffering substrates.

Aspergillus oryzae α-amylase supplementation on rumen volatile fatty acid profile and relative abundance of mRNA associated with nutrient absorption in ruminal and duodenal tissue from beef steers

ABSTRACT The objective of this experiment was to investigate the effect of Aspergillus oryzae α-amylase (AAM) supplementation on rumen VFA profile and relative abundance of mRNA associated with nutrient absorption in ruminal and duodenal tissue from beef steers. Nine crossbred beef steers (BW 622 ± 50 kg), fitted with rumen and duodenal fistulas, were used in this experiment. Steers were housed in individual stanchions and fed a high-concentrate finishing diet (6% forage NDF) twice daily for 8 d. Treatments included (1) control (corn meal; n = 5) and (2) AAM (fungal α-amylase 750 units/g; n = 4). Dietary treatment supplements were manufactured before each feeding by mixing 3 g of α-amylase or corn meal into 150 g of dried distillers grains for the morning feeding and 2 g of α-amylase or corn meal into 100 g of dried distillers grains for the afternoon feeding. Supplements were applied as a top dress for every feeding and thoroughly mixed by hand. On d 5, rumen fluid samples were obtained every 4 h for 24 h and analyzed for VFA. On d 9, rumen papillae and duodenal mucosal tissue samples were collected. Total tissue RNA was extracted for real-time PCR analysis. Sodium/potassium ATPase pump α1; glucose transporter 2 and 5; putative anion transporter isoform 1; sodium/hydrogen antiporter isoforms 1, 2, and 3; 3-hydroxy 3-methylglutaryl coenzyme A synthase isoform 2; downregulated in adenoma; monocarboxylate cotransporter isoform 1; and glyceraldehyde-3-phosphate dehydrogenase mRNA were tested. No treatment differences (P > 0.21) were detected for any of the genes analyzed in ruminal or duodenal tissue. Concentrations of VFA and the acetate-to-propionate ratio did not differ (P > 0.22) among treatments. However, the acetate-to-propionate ratio and molar percentages of butyrate were numerically greater (P = 0.17) in AAM steers compared with controls. Under the conditions of this experiment, AAM supplementation had no effect on relative expression of mRNA associated with nutrient absorption and minimal effects on molar proportions of VFA.

Effects of flaxseed and chia seed on ruminal fermentation, nutrient digestibility, and long-chain fatty acid flow in a dual-flow continuous culture system.

Flaxseed (FS) and chia seed (CS) are oilseeds rich in omega-3 fatty acids, which may change meat and milk composition when added to ruminants' diets and may have health benefits for humans. Literature on the effects of CS supplementation on ruminal metabolism is nonexistent. A dual-flow continuous culture fermenter system consisting of 6 fermenters was used to assess the effect of FS and CS supplementation in an alfalfa hay-based diet on ruminal fermentation, nutrient digestibility, microbial protein synthesis, and long-chain fatty acid flow. Diets were randomly assigned to fermenters in a replicated 3 × 3 Latin square design, with 3 consecutive periods of 10 d each, consisting of 7 d for diet adaptation and 3 d for sample collection. Each fermenter was fed a total of 72 g of DM/d divided in 6 equal portions. Treatments were 1) alfalfa hay + calcium soaps of palm oil fatty acid (MEG; 69.3 g DM/d of alfalfa hay plus 2.7 g DM/d of calcium soaps of palm oil fatty acid), 2) alfalfa hay + FS (FLAX; 68.4 g DM/d of alfalfa hay plus 3.6 g DM/d of ground FS), and 3) alfalfa hay + CS (CHIA; 68.04 g DM/d of alfalfa hay plus 3.96 g DM/d of ground CS). Dietary treatments had similar amounts of total fat, and fat supplements were ground to 2-mm diameter. Effluents from the last 3 d of incubation were composited for analyses. Data were analyzed using the MIXED procedure of SAS. Ruminal apparent and true nutrient digestibility of all nutrients did not differ ( > 0.05) among treatments. Compared with MEG, FLAX and CHIA increased the flows of C18:3 -3, C20:4 -6, and total PUFA ( < 0.01). Both CHIA and FLAX treatments had greater ruminal concentrations of C18:0, indicating that both CS and FS fatty acids were extensively biohydrogenated in the rumen. The NH-N concentration, microbial N flow, and efficiency of microbial protein synthesis were not affected ( > 0.05) by treatments. Lastly, there were no differences ( > 0.05) among diets for total VFA concentration and molar proportions of individual VFA. Results from this study indicate that FS and CS supplementation did not impair ruminal fermentation, digestibility, microbial efficiency, and ruminal N metabolism. Overall, CS appears to be as effective as FS as a fat source when added to ruminants' diets using a dual-flow continuous culture system.

Influence of flake fragmentation on the feeding value of steam-flaked corn in finishing diets for feedlot cattle

Two trials were conducted to evaluate the influence of fines on the feeding value of steam-flaked corn (SFC) in finishing diets for feedlot cattle. Three levels (0, 333 and 667g/kg) of re-rolled SFC replaced standard SFC (0.31kg/L) in a corn-based finishing diet (DM basis). Diets were offered as total mixed rations. Re-rolled SFC consisted of standard air-dry SFC that was passed through the rollers a second time to simulate loss of flake integrity which can occur during feed-handling. In experiment one, the influence of fines in SFC on growth performance was evaluated in eighteen crossbred steers (294±5kg) in a replicated 3×3 Latin square design. Daily weight gain was similar (P>0.10) among treatments, averaging 1.31kg/d. Dry matter intake tended to be greater (quadratic effect, P=0.06) for diets containing re-rolled steam-flaked corn. Gain efficiency and dietary NE were not influenced by dietary treatments (P>0.10). In experiment two, six Holstein steers (308±17kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3×3 Latin square design to evaluate treatment effects on characteristics of digestion. Reductions in particle size of SFC due to rerolling did not influence ruminal or total tract digestion of OM, NDF, N, or starch (P>0.10). Likewise, there were no treatment effects (P>0.10) on ruminal microbial efficiency, ruminal pH, or ruminal VFA molar proportions. It is concluded that the impact of flake disintegration during conveyance and handling on feedlot cattle growth performance and characteristics of digestion will be marginal, if appreciable.

Forage and sugar in dairy calves' starter diet and their interaction on performance, weaning age and rumen fermentation

The effects of sugar and forage inclusion in calves' starter and their interaction on animal performance and rumen fermentation parameters were investigated. Twenty-eight neonatal Holstein male calves 3 days of age with average body weights of 42 ± 4 kg were allocated to four different treatments. All calves were fed a similar basal diet consisting of milk and concentrate. The experimental treatments were: (i) basal diet with no supplementation (Control, hereafter designated by C), (ii) basal diet plus 5% granular sugar cane (Sugar, designated by S), (iii) basal diet plus 5% forage (Forage, designated by F) and (iv) basal diet plus 5% forage with 5% granular sugar cane (F × S). Supplement ingredients were used on a dry matter (DM) basis. Rumen fluid parameters were measured twice on days 35 and 70 of the study period. The calves were weaned when they could consume 1 kg of starter for three consecutive days. The results show that starter intake was not affected by treatment; however, the lowest ADG was observed with calves in the sugar treatment. Weaning age was affected by treatments, and forage showed to reduce milk consumption period down to its shortest. Forage-sugar interaction was found to have no effects on animal performance. The structural body indices as well as the health status of the calves were similar in different treatments. Rumen pH did not differ among the treatment groups. Among the rumen parameters, total VFA concentration and molar proportions of butyrate and propionate did not exhibit any significant differences among the treatments. However, ruminal acetate concentration decreased in calves that fed sugar cane during the early weeks of the study period. Comparison of forage and sugar included in the starter diets revealed that forage reduced weaning age, while sugar cane had a negative effect on calves' performance.

Influence of forage NDF level, source and pelletizing on growth performance, dietary energetics, and characteristics of digestive function for feedlot cattle

One hundred sixty Holstein steers (222±1kg) were used in a 264-d growing-finishing trial to evaluate the influence of forage aNDFom level (40 vs 80g/kg DM) and source [ground forage (alfalfa, sudangrass, and rice straw) or pelletized rice straw] on growth performance. Forage source did not influence (P>0.10) gain efficiency or dietary net energy (NE). Daily weight gain (ADG) and dry matter intake (DMI) were similar (P>0.10) for alfalfa, sudangrass and ground rice straw. Pelletizing rice straw depressed ADG (P<0.01) and DMI (P<0.01). Increasing forage aNDFom decreased gain efficiency (P=0.09), and dietary NE (P=0.04). Four Holstein steers (197kg) with ruminal and proximal duodenal cannulas were used in a 4×4 Latin square design to compare effects of alfalfa vs sudangrass hay at 40 vs 80g/kg of forage aNDFom on digestion. There were no treatment effects on ruminal aNDFom digestion (P>0.10). Ruminal OM digestion was not affected by forage aNDFom level (P=0.96); however, it was greater (P=0.04) for sudangrass vs alfalfa supplemented diets. Microbial efficiency was not affected by forage aNDFom level (P=0.53); however, it was greater (P=0.02) for alfalfa vs sudangrass supplemented diets. Forage source did not affect total tract aNDFom digestion (P=0.86). However, aNDFom digestion was greater (P=0.08) for 80 vs 40g/kg of forage aNDFom. There were interactions between forage aNDFom level and source on total tract OM digestion (P=0.03). With alfalfa, level of forage aNDFom did not affect OM digestion. With sudangrass, increasing forage aNDFom decreased (P<0.05) total tract OM digestion. There were interactions between forage aNDFom level and source on ruminal pH (P=0.05), and acetate:propionate ratio. With alfalfa, increasing forage aNDFom did not affect ruminal pH, but increased acetate:propionate molar ratio. With sudangrass, the increasing forage aNDFom increased ruminal pH, but did not affect VFA molar ratios. Four Holstein steers (189kg) were used in a 4×4 Latin square design to compare effects of ground vs pelletized rice straw at 40 vs 80g/kg of forage aNDFom on digestion. There were no treatment effects (P>0.10) on ruminal OM digestion or microbial efficiency. Ruminal aNDFom digestion was greater (P=0.05) for pelletized vs ground rice straw. There were no treatment effects (P>0.10) on total tract aNDFom digestion. Pelletizing did not affect (P=0.78) total tract OM digestion. Tract OM digestion was greater (P=0.03) for 40 vs 80g/kg of forage aNDFom. Level of forage aNDFom did not affect (P>0.10) ruminal pH or VFA molar proportions. Ruminal pH and acetate:propionate molar ratio were greater (P<0.10) for ground vs pelletized rice straw. Differences among forage sources are minimized when forages are compared at similar levels of forage aNDFom concentration. Compared to ground, pelleted rice straw in finishing diets may produce lower ruminal pH and growth-performance of cattle.

Effects of bulk density of steam-flaked corn in diets containing wet corn gluten feed on feedlot cattle performance, carcass characteristics, apparent total tract digestibility, and ruminal fermentation1

The effects of varying bulk density of steam-flaked corn (SFC) in diets containing wet corn gluten feed (WCGF; Sweet Bran; Cargill Corn Milling, Blair, NE) have not been defined. In Exp. 1, yearling steers (n = 108; initial BW = 367 ± 1.18 kg) were housed in 27 pens (4 steers/pen) and received 1 of 3 different SFC bulk density treatments in a randomized complete block design. Bulk density treatments were 283, 335, or 386 g/L SFC in diets containing 25% WCGF (% of DM). Steers were fed once daily to provide ad libitum access to feed for an average of 163 d. For a 5-d period before d 70 of the experiment, DMI was measured, and fecal samples were collected from each pen for measurement of nutrient digestibility using dietary acid insoluble ash as a marker. Varying bulk densities of SFC did not affect (P ≥ 0.233) overall DMI, ADG, or G:F on a live- or carcass-adjusted basis. Dressing percent and LM area increased linearly (P ≤ 0.05) as bulk density increased, but other carcass traits were not affected by treatments. Intake of DM, OM, and CP during the 5-d digestion phase did not differ among bulk densities; however, starch intake increased linearly (P = 0.004) as bulk density of SFC increased. Digestibility of DM, OM, and CP tended (P ≤ 0.065) to decrease and starch digestibility decreased (P = 0.002) linearly as bulk density of SFC increased. In Exp. 2, a 3 × 3 Latin square design was used for collection of ruminal fluid from 3 ruminally cannulated Jersey steers adapted to the same diets used in Exp. 1. Bulk density did not affect NH3 concentrations, VFA molar proportions, ruminal fluid osmolality, and IVDMD of the diets. Total gas production increased linearly (P = 0.003) as bulk density of SFC increased from 283 to 335 g/L, but it decreased (P = 0.002) at 386 g/L. Present data suggest that bulk density can be increased up to 386 g/L in finishing diets containing 25% (DM basis) WCGF without affecting cattle performance and with limited effects on ruminal fermentation; however, digestibility of starch seemed to be affected negatively by increased bulk density in these diets.

Nutrient utilization, ruminal fermentation, microbial nitrogen flow, microbial abundances, and methane emissions in goats fed diets including tomato and cucumber waste fruits1

The effects of replacing 50% of cereals-based concentrate with feed blocks (FB) including wastes of tomato fruits (diet ACT), wastes of cucumber fruits (diet ACC), or barley grain (diet ACB) on nutrient use, ruminal fermentation, microbial N flow to the duodenum, methane emissions, and abundances of total bacteria and methanogen were studied in goats. Four adult, dry, nonpregnant, rumen-fistulated Granadina goats (32.1 ± 5.52 kg BW) were used and 4 diets were studied in 4 trials by using a 4 × 4 Latin square experimental design. Diets consisted of alfalfa hay plus concentrate in a 1:1 ratio (AC) or 1:0.5 plus FB including wastes of ACT, ACC, or ACB. In each trial, goats were randomly assigned to 1 of the diets. Intake of each FB including ACT, ACC, and ACB were 203 ± 73, 179 ± 39, and 144 ± 68 g·animal(-1)·d(-1), respectively. The ACT and ACC diets did not (P > 0.05) compromise digestible and metabolizable energy, but reduced N retention by up to 29% (P = 0.03). Cucumber-based FB decreased the purine bases (PB):N ratio (P = 0.02) in total bacterial pellets isolated from the rumen content. Tomato-based FB decreased purine derivatives urinary excretion (P = 0.04) and microbial N flow (P = 0.03) without affecting the efficiency of synthesis but decreased methane emission by 28% (P < 0.001) compared with the other diets. Tomato and cucumber-based FB resulted in greater (P < 0.001) rumen VFA concentration and molar proportions of propionate and butyrate (P ≤ 0.02) than AC and ACB diets. No effect (P = 0.07) of diet on total bacteria abundance was observed whereas the abundance of methanogens increased (P = 0.01) with wastes-based FB. Our study suggests that ACC-based FB could replace one-half of the amount of concentrate in goat diet without compromising rumen fermentation and nutrient and energy use and without increasing methane emissions. Blocks including ACT showed an antimethanogenic effect but reduced microbial N flow to the duodenum. Further research is needed to improve both N and energy use of diets including ACT- and ACC-based FB.