Influence of sodium bicarbonate and magnesium oxide on digestion and metabolism in yearling beef steers abruptly changed from high forage to high energy diets

Eight rumen-cannulated steers (initial wt 330kg) were adapted to a mixed alfalfa-grass hay diet for 30 d and abruptly changed to complete mixed diets of corn silage, snapped ear corn and a corn-based supplement to determine the effects of buffers on diet adaptation, digestion and ruminal metabolism. The diets contained: 1) no buffer, 2) .5% magnesium oxide (MgO), 3) 1.0% sodium bicarbonate (NaHCO3) and 4) .5% MgO and 1.0% NaHCO3, as a percentage of diet dry matter (DM). Digestion, metabolism and ruminal characteristics were measured in each of 2 wk immediately after the diet change. The animals were then adapted to the mixed alfalfa-grass hay diet, re-randomized and assigned to the four diets, thus four steers consumed each diet. Intakes and digestibilities of DM were generally greater for the diets containing buffers. The most notable differences were a greater DM intake with added NaHCO3 and an improved DM digestibility with added MgO. The higher DM digestibility with MgO was apparently related to improved neutral detergent fiber (NDF) and starch digestion. Fecal pH was significantly increased with MgO addition. Because of the greater intake and digestibilities, the amount of DM, NDF, and starch digested tended to be greater for the buffered diets. There were no diet X week interactions for intake and digestibilities, thus the responses observed existed during both wk 1 and 2 after the change in diets. In general, intake and digestibilities were greater in wk 2 than in wk 1 for all diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of diet concentrate level and sodium bicarbonate on site and extent of forage fiber digestion in the gastrointestinal tract of wethers

Four adult wethers (45 kg) with permanent ruminal and abomasal cannulae were used in a repeated measures Latin-square arrangement of treatments to quantitate the effects of diet concentrate level and sodium bicarbonate (NaHCO3) on site and extent of forage fiber digestion in the gastrointestinal tract. Experimental diets consisted of Kentucky-31 tall fescue hay, soybean meal and a semi-purified concentrate mixture in ratios of 95:5:0, 76:4:20, 57:3:40 and 38:2:60; NaHCO3 represented 0 or 7.5% of the concentrate mixture. Ruminal digestion (% of intake) of neutral detergent fiber (NDF) and hemicellulose decreased linearly (P less than .05), whereas acid detergent fiber (ADF) digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 improved ruminal digestion of NDF (P less than .10) and ADF (P less than .05), but not hemicellulose. Post-ruminal digestion (% of rumen non-degraded) of NDF and ADF tended to increase, whereas hemicellulose digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 decreased (P less than .05) post-ruminal digestion of all fiber fractions. Total tract digestion of NDF and ADF showed a cubic (P less than .05) response, whereas hemicellulose digestion responded in a quadratic (P less than .05) fashion to increasing concentrate level; NaHCO3 had no effect on total tract digestion of any fiber fraction. Correlations of ruminal hemicellulose digestion with mean pH (r = .33; P = .07) and minimum pH (r = .30; P = .09) were attained in a 24-h feeding cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutrients intake,digestibility, nitrogen balance and growth performance of sheep fed different silages with or without concentrate

The experiment was conducted to investigate the influence of maize (Zea mays), sorghum (Sorghum bicolor) and millet (Pennisetum americannum) silages with or without concentrate on nutrients intake, digestibility, nitrogen balance and weight gain in Sipli sheep. Six experimental diets were formulated having 100% maize silage (MS), maize silage and concentrate as 50:50 (MSC), 100% sorghum silage (SS), sorghum silage and concentrate as 50:50 (SSC), 100% millet silage (MiS) and millet silage and concentrate as 50:50 (MiSC), respectively. For this purpose, 24 Sipli lambs were randomly allotted to six experimental diets in a completely randomized design for 90 days, four lambs per diet. The results indicated that among various silage diets, lambs fed MS diet consumed higher dry matter (DM) than those fed SS and MiS diets. Likewise, lambs offered MSC had higher dry matter intake than those fed SSC and MiSC diets. Crude protein (CP) and neutral detergent fibre (NDF) consumed by the lambs also followed the similar trend. Higher DM, CP and NDF digestibilities were also observed in lambs fed MS and MSC diets than those fed SS, SSC, MiS and MiSC diets. Overall digestibilities of DM, CP and NDF were higher in experimental diets containing silage with concentrate. Lambs fed MS diet had 2.79 g/day and 4.45 g/day higher N retention than those fed SS and MiS, respectively. Similarly, lambs fed MSC diet had 2.24 g/day and 5.12 g/day higher N retention than those fed SSC and MiSC diets, respectively. The results showed that lambs fed MSC gained more daily weight gain had better feed conversion ratio than those fed MS, SS, SSC, MiS and MiSC diets. The findings of the present study indicated that lambs fed MSC diet had higher nutrients intake, digestibility, nitrogen balance and weight gain.     

Influence of source and level of ruminal-escape lipid in supplements on forage intake, digestibility, digesta flow, and fermentation characteristics in beef cattle.

Six ruminally fistulated steers (550 kg) and 24 heifers (315 kg) were used to determine the effect of source and amount of ruminal-escape lipid in a supplement on forage intake and digestion. Steers were used in a 6 x 6 Latin square digestion study to evaluate six supplementation treatments: 1) negative control (NC), no supplement; 2) positive control (PC), soybean meal:grain sorghum supplement; 3) low-Megalac (calcium salts of fatty acids; LM) supplement; 4) high-Megalac (HM) supplement; 5) low-Alifet (crystallized natural animal fat, LA) supplement; and 6) high-Alifet (HA) supplement. Supplements were fed at .30% of BW on a DM basis and were isoenergetic within fat levels (high vs low). Steers were fed mature brome hay (7.2% CP) at 1.5% of BW on a DM basis. In the forage intake trial, heifers were assigned randomly to the same supplement treatments. Prairie hay (4.4% CP) was offered at 130% of ad libitum intake. Dry matter and NDF digestibility, ruminal DM fill, indigestible ADF passage rate, and fluid dilution and flow rates were not different (P greater than .10) among treatments. Total VFA concentrations were greater (P less than .01) and acetate-to-propionate ratio (Ac:Pr) was less (P less than .01) in supplemented groups; however, neither source nor level of escape lipid influenced either total VFA or Ac:Pr. Forage intake was greater (P less than .01) for supplemented groups than for the NC. At the high level of fat inclusion, heifers supplemented with Alifet ate slightly more (P less than .05) forage than those supplemented with Megalac.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of source and level of dietary neutral detergent fiber on feed intake, ruminal fermentation, ruminal digestion in situ, and total tract digestion in beef cattle fed pelleted concentrates with or without supplemental roughage.

The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.     

Substitution of wheat dried distillers grains with solubles for barley grain or barley silage in feedlot cattle diets: intake, digestibility, and ruminal fermentation

The objective of this study was to evaluate the effects of substituting wheat dried distillers grains with solubles (DDGS) for barley grain and barley silage on intake, digestibility, and ruminal fermentation in feedlot beef cattle. Eight ruminally cannulated Angus heifers (initial BW 455 ± 10.8 kg) were assigned to a replicated 4 × 4 Latin square design with 4 treatments: control, low (25%), medium (30%), and high (35%) wheat DDGS (DM basis). The diets consisted of barley silage, barley concentrate, and wheat DDGS in ratios of 15:85:0 (CON), 10:65:25 (25DDGS), 5:65:30 (30DDGS), and 0:65:35 (35DDGS; DM basis), respectively. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy (grain) and fiber in feedlot finishing diets. Intakes (kg/d) of DM and OM were not different, whereas those of CP, NDF, ADF, and ether extract (EE) were greater (P < 0.01) and intake of starch was less (P < 0.01) for the 25DDGS compared with the CON diet. The digestibilities of CP, NDF, ADF, and EE in the total digestive tract were greater (P < 0.05) for 25DDGS vs. CON. Ruminal pH and total VFA concentrations were not different (P > 0.15) between 25DDGS and CON diets. Replacing barley silage with increasing amounts of wheat DDGS (i.e., from 25DDGS to 35DDGS) linearly reduced (P < 0.05) intakes of DM and other nutrients without altering (P=0.40) CP intake. In contrast, digestibilities of DM and other nutrients in the total digestive tract linearly increased (P < 0.05) with increasing wheat DDGS except for that of EE. Additionally, with increasing amounts of wheat DDGS, mean ruminal pH tended (P=0.10) to linearly decrease, and ruminal pH status decreased with longer (P=0.04) duration of pH <5.5 and <5.2, and greater (P=0.01) curve area under pH <5.8 and <5.5 without altering (P > 0.19) ruminal VFA and NH(3)-N concentrations. Results indicated that wheat DDGS can be effectively used to replace both barley grain and silage at a moderate amount to meet energy and fiber requirements of finishing cattle. However, when silage content of the diet is low (<10%), wheat DDGS is not an effective fiber source, so replacing forage fiber with wheat DDGS in finishing diets decreases overall ruminal pH status even though the rapidly fermentable starch content of the diet is considerably reduced.     

The effects of corn silage dry matter content and sodium bicarbonate addition on nutrient digestion and growth by lambs and calves

One lamb and three calf trials were conducted to determine if interactions existed between the effects of dry matter (DM) content of corn silage at harvest and sodium bicarbonate supplementation on diet digestibility, nitrogen balance, rate and site of digestion and feedlot performance. Corn plants were harvested from the same field when DM content was approximately 31% (early; E) or 44% (late; L). Sodium bicarbonate (1.2% of DM intake) was added in a completely mixed ration. When lambs were offered diets ad libitum, (trial 1), intakes were greater (P less than .05) for L-silage diets, but apparent digestibilities were similar. Nitrogen balance was greater for sodium bicarbonate-supplemented diets, and was a reflection of greater (P less than .10) DM intakes for these diets. At similar diet DM intakes, N balance was greater for L-silage diets, with no effects measured due to sodium bicarbonate addition. When growing, abomasally cannulated heifers (trial 2) were offered diets 12 times per day, a significant interaction among treatments was measured for total tract and acid detergent fiber (ADF) digestion. Adding bicarbonate to the E-silage diet increased (P less than .05) digestion by 9.1 percentage units (66.4 vs 75.5%) but decreased digestibility of the L-silage diet by 4.2 percentage units (73 vs 68.8%). Grams of ADF apparently digested in the rumen followed the same pattern as for total tract digestion. In trial 3, ruminal rates of liquid and particulate passage and in situ rats of NDF digestion were determined using four rumen-cannulated heifers calves.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of feeding alkaline hydrogen peroxide-treated wheat straw-based diets on intake, digestion, ruminal fermentation, and production responses by mid-lactation dairy cows.

The objective of this experiment was to determine the effects of feeding different levels of alkaline hydrogen peroxide-treated wheat straw (AHP-WS) in the diet on feed intake, nutrient digestion, ruminal fermentation, and production responses in mid-lactation dairy cows. Eight Holstein cows, averaging 147 d postpartum, were used in two replications of a 4 x 4 Latin square design. Complete mixed diets consisted of 70% forage and 30% concentrate (DM basis) with various levels of AHP-WS, alfalfa haylage, and corn silage as forage sources. Treatments contained 0 (control), 20.0, 40.1, or 60.0% AHP-WS in the diet. A quadratic effect (P = .08) of AHP-WS level on DMI was noted, with values of 2.16, 22.3, 20.8, and 18.9 kg/d for the control, 20.0, 40.1, and 60.0% AHP-WS treatments, respectively. Apparent digestibilities of DM, OM, CP, and ADF were not affected (P greater than .10) by replacing haylage and corn silage with increasing amounts of AHP-WS in the diet, but there was a linear increase (P = .03) in NDF digestibility (44% for control vs 59% for the 60.0% AHP-WS diet) and a parallel decrease (P less than .05) in cell content digestibility (82 vs 70% for these two diets). Yields of milk and 4% fat-corrected milk (FCM) were decreased (quadratic; P = .0001) as the level of AHP-WS increased in the diet. The addition of AHP-WS to the diet decreased the milk fat percentage from 3.72 to 3.60% (quadratic; P = .05) and decreased milk protein percentage from 3.27 to 3.13% (linear; P = .0001). Cows fed the higher levels of AHP-WS had linear increases (P = .0001) in ruminal concentrations of total VFA (128.0 mM for control vs 136.0 mM for the 60.0% AHP-WS treatment) and molar proportion of acetate, resulting in a quadratic effect (P less than .0001) on the acetate:propionate ratio. These data indicate that feeding the 40.1 and 60.0% AHP-WS diets lowered digestible DM and OM intakes, which resulted in reduced 4% FCM yield as nutrient intakes were decreased compared with cows fed the 20.0% AHP-WS diet or the control diet containing alfalfa haylage and corn silage. Although substituting AHP-WS for haylage and corn silage increased NDF digestibility and tended to increase digestible NDF intake, milk production was depressed because digestible DMI decreased.     

Effects of calcium soaps of long-chain fatty acids on feedlot performance, carcass characteristics and ruminal metabolism of steers

Two trials were conducted to determine the effects of calcium soaps of long-chain fatty acids (calcium soap) on feedlot performance, diet digestibility, carcass characteristics and ruminal metabolism of steers fed diets (85% concentrate:15% corn silage) containing 0, 2, 4 or 6% calcium soap. In Trial 1, increasing calcium soap decreased (P less than .05) DM, CP and gross energy intake but increased total fatty acid intake. Feed to gain ratio tended to improve with increased calcium soap; gross energy conversion was not affected (P greater than .05) by diet. Average daily gain and hot carcass weight decreased (P less than .05) with addition of calcium soap; other carcass characteristics were not affected (P greater than .05). Apparent digestibilities of DM, N, energy and ash were not affected (P greater than .05) by calcium soap. Neutral detergent fiber digestibility increased linearly (P less than .08) with increasing calcium soap, whereas digestibility of total fatty acids was affected quadratically (P less than .05); fatty acid digestibility was similar among 0, 2 and 4% calcium soap diets but decreased for the 6% calcium soap diet. In Trial 2, increased calcium soap did not affect (P greater than .05) ruminal VFA concentrations, pH or in sacco NDF disappearance of orchardgrass following 12, 24 and 48 h of incubation. Calcium soap increased (P less than .07) ruminal concentrations of calcium soap fatty acids at 1, 2, 4 and 8 h postfeeding. Calcium soap did not improve performance of feedlot cattle fed high-concentrate diets. Further, calcium soap did not affect ruminal fermentation and did not dissociate significantly even when ruminal pH was below 6 for extended periods of time.     

Effects of supplemental silage on forage intake and utilization by steers grazing wheat pasture or bermudagrass

Seven trials were conducted to determine the effects of increasing amounts of silage (corn, wheat or sorghum) on forage intake, gastrointestinal tract fill, fecal output and ruminal flow and degradation of forage by cattle grazing wheat pasture or bermudagrass. In each of 3 yr, 24 steers grazed a common wheat or bermudagrass pasture and were randomly allocated to four treatments (0, .35, .70 or 1.05 kg silage DM.100 kg body weight-1.d-1). Intake and ruminal flow of forage were measured by feeding a single pulse dose of Yb-labeled forage followed by collection of fecal samples for 4 to 5 d and fitting Yb concentrations to a one-compartment, age-dependent model. Ruminal digestion kinetics of wheat forage were estimated in situ using eight ruminally cannulated steers fed 0 or .55 kg sorghum silage DM.100 kg body weight-1.d-1. Supplemental silage decreased wheat forage (P less than .10) and bermudagrass (P less than .01) intake linearly. However, total forage intake of bermudagrass plus silage increased linearly (P less than .05). Each kilogram of added silage DM decreased DM intake of wheat forage by .66 +/- .25 and of bermudagrass by .63 +/- .17 kg. Flow and turnover of wheat forage or bermudagrass were not altered (P greater than .15) by supplemental silage. Silage consumption increased extent of ruminal degradation of wheat forage DM (P less than .05; 63.1 vs 52.5%), indicating a positive associative effect of silage on wheat forage utilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acid-base and electrolyte balance in dairy heifers fed forage and concentrate rations: effects of sodium bicarbonate

Eight Holstein heifers were fed diets of alfalfa hay, corn silage, or finely ground corn grain with or without NaHCO3 in a rotating experimental design. Acid-base status and renal excretion of electrolytes were evaluated during short-term (1 and 5 day) and long-term (24 day) feeding trials. Heifers fed alfalfa hay had a greater metabolic buffering capacity than did heifers fed corn silage. Heifers fed grain had lower blood pH and bicarbonate values than did those fed the forage diets. The most pronounced effects of grain-feeding were aciduria and phosphaturia. Aciduria did not occur when NaHCO3 was added to the grain at 2% of the ration on a dry matter basis. Grain-fed heifers had significantly (P less than 0.05) lower blood and urine pH and bicarbonate values, and excreted significantly more calcium, phosphorus, and magnesium in the urine than did those fed grain plus NaHCO3. Sodium bicarbonate, as a 2% dietary supplement, counteracted many effects of high-grain diets.     

Effect of supplemental sodium bicarbonate on nutrient digestibilities and ruminal pH measured continuously

A technique was used to monitor continuously ruminal pH using a strip-chart recording pH meter. Ruminal pH measurements were made in four ruminal-cannulated crossbred wether lambs (ag initial weight, 42.5 kg). For l.5 h daily, lambs were given ad libitum access to 50% concentrate-50% chopped orchardgrass hay diets supplements with 0, l.5, 3.0 and 4.5% sodium bicarbonate (NaHCO3). A split-plot Latin-square design was used to evaluate NaHCO3 level and day of adaptation on the percentage of time (%T) that ruminal pH was less than 6.6, 6.2, 5.8, 5.4 and 5.0. No effect due to day of adaptation existed for ruminal pH measurements (P more than .10), while the effect of dietary NaHCO3 level was quadratic (P more than .01) for the %T that ruminal pH was less than 5.4. To evaluate the effects of NaHCO3 on nutrient digestion, the same diets were fed to eight wether lambs (avg initial weight, 38 kg) at 85% of their ad libitum intake in a replicated 4 x 4 Latin-square digestion trial. Digestibilities of dry matter (DM), organic matter, N and fiber fractions were not different due to level of NaHCO3 (P greater than .10). Ash digestibility increased with increasing levels of dietary NaHCO3 (P less than .01). Four ruminal-cannulated mature Hereford steers were also given ad libitum access to the diets in a split-plot Latin-square trial to evaluate effects of dietary NaHCO3 level on ruminal pH and in situ digestion of soybean meal N and orchardgrass DM. During incubation of the dacron bags for 3, 6, 9, 12, 24 and 36 h also increased linearly with increasing level of NaHCO3. Ruminal solid and liquid dilution rates were not affected by level of supplemental NaHCO3 (P greater than .10). The results of these trials suggest that increasing level of dietary NaHCO3 greatly increases the proportion of time ruminal pH is above critical levels for ruminal protein and dry matter digestion, but does not affect total tract nutrient digestion when 50% concentrate diets are fed.     

Effect of salinomycin level on nutrient digestibility and ruminal characteristics of sheep and feedlot performance of cattle

A sheep digestion trial and two feedlot trials with cattle were conducted to study effects of an ionophore, salinomycin, on nutrient digestibility, ruminal metabolism and cattle performance. In trial 1, addition of salinomycin at 5.5, 11 or 22 ppm to 60% concentrate diets fed to ruminal-cannulated rams had no effect (P greater than .05) on apparent digestibility of dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF) or starch in comparison with control diets. Apparent nitrogen (N) digestibility was increased (P less than .05) in animals fed salinomycin. Salinomycin did not affect total volatile fatty acid (VFA) concentrations in the rumen, but resulted in a linear (P less than .05) increase in molar proportion of propionate and a linear (P less than .05) decrease in molar proportions of acetate and butyrate and in acetate:propionate ratios. Shifts in VFA proportions were fully expressed within 4 d after salinomycin was added to the diet. In trial 2, salinomycin was added at 5.5, 11, 22 or 33 ppm to 85% concentrate diets fed to finishing steers. Salinomycin level had a quadratic effect (P less than .05) on daily weight gain and resulted in a quadratic (P less than .05) decrease in feed intake with a resultant average improvement of 10.3% in feed efficiency. Salinomycin (5.5, 11, 16.5 or 22 ppm) and monensin (22 ppm) were added to 90% concentrate diets in trial 3 and produced increased rates of gain without affecting feed intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of wheat middlings as a supplement for beef cattle consuming dormant bluestem-range forage

Two experiments were conducted to evaluate wheat middlings as a supplement for cattle consuming dormant bluestem-range forage. Effects of supplement type and amount were evaluated in Exp. 1, which consisted of feeding supplements of soybean meal:grain sorghum (22:78) or two different amounts of wheat middlings. Sixteen ruminally fistulated steers were blocked by weight (BW = 374 +/- 8.3 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) soybean meal:grain sorghum (SBM/GS) formulated to contain the same CP concentration (21%) and fed to provide a similar energy level (3.5 Mcal of ME/d); 3) a supplement of 100% wheat middlings fed at a low level (LWM); and 4) 100% wheat middlings fed at twice the amount of LWM (7 Mcal of ME/d; HWM). The influence of different supplemental CP concentrations in a wheat middlings-based supplement was evaluated in Exp. 2. Sixteen ruminally fistulated steers were blocked by weight (BW = 422 +/- 8.1 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) 15% CP; 3) 20% CP; and 4) 25% CP supplements. These supplements consisted of 60% wheat middlings and various ratios of soybean meal and grain sorghum to achieve the desired CP concentration. In Exp. 1, SBM/GS and HWM supplements increased (P less than .10) and LWM tended to increase (P = .16) forage DMI compared with NS. All supplements in Exp. 1 increased (P less than .10) DM digestibility, ruminal DM fill, and ruminal indigestible ADF (IADF) passage rate compared with NS, although the greatest response in fill and passage was observed with HWM. In Exp. 2, forage DMI, DM digestibility, NDF digestibility, ruminal DM and IADF fill, IADF passage rate, and fluid dilution rate were increased (P less than .01) by supplementation. Forage DMI, ruminal IADF passage rate, and fluid dilution rate increased quadratically (P less than .10), and NDF digestibility, ruminal DM and IADF fill increased linearly (P less than .10) with increased supplemental CP concentration. These experiments indicate that wheat middlings performed similarly to a SBM/GS supplement of equal CP concentration, when both were fed to provide a similar amount of energy daily. Additionally, use of poor-quality range forage was enhanced when wheat middlings-based supplements were formulated to contain a CP concentration of 20% or greater.     

The effects of protein sources supplemented with urea-treated potato pulp (PP) silage and feeding levels of the PP silage-based concentrate on feed intake, digestibility and ruminal fermentation in beef steers

Six Japanese Black (Wagyu) steers (average initial weight 467 ± 45 kg) fitted with a ruminal cannula were used in a split‐plot design experiment comprising a 3 × 3 Latin square design (whole‐plot) and a randomized block design (subplot). The whole‐plot treatments were three different feeding levels of urea‐treated potato pulp (PP) silage‐based concentrate: 1.00%, 1.75% and 2.50% of body weight (BW) (on a dry matter (DM) basis). The subplot treatments consisted of the concentrate formulated to contain either soybean meal (SBM) as a rapidly rumen‐degraded protein source or corn gluten meal (CGM) as a slowly degraded protein source. Dry matter intake tended to be lower (P = 0.071) for CGM (8.9 kg/day) than for SBM (9.4 kg/day). Protein sources had no significant effect on digestibility and in situ degradation. Ruminal ammonia nitrogen (NH₃‐N) was lower (P = 0.033) for CGM (7.5 mg/dL) than for SBM (9.5 mg/dL). Protein sources did not affect ruminal pH and the total volatile fatty acids (VFA) concentrations. The molar proportions of ruminal acetate and valerate were higher (P = 0.032) for CGM than for SBM. The maximum daily intake of the PP silage‐based concentrate expressed as a percentage of BW was approximately 1.4% of BW. Dry matter intake was higher (P = 0.046) for steers fed at 1.0% of BW of the PP silage‐based concentrate than for steers fed at 1.75% or 2.5% of BW of the concentrate. The feeding levels of the PP silage‐based concentrate had no effect on DM and nutrients digestibility, except for crude protein (CP) digestibility. CP digestibility tended to be lower (P = 0.071) for steers fed at 1.75% of BW of the PP silage‐based concentrate than for steers fed at 1.0% or 2.5% of BW of the concentrate. The feeding levels of the PP silage‐based concentrate also did not affect the in situ degradation parameter of hay and PP silage. The feeding levels of the PP silage‐based concentrate did not affect ruminal pH, NH₃‐N and total VFA concentrations. The molar proportion of acetate was highest for steers fed at 1.0% of BW of the concentrate. In conclusion, in the urea‐treated PP silage‐based concentrate, CGM seems to be more effective than SBM for stabilizing the ruminal NH₃‐N concentration and to be advantageous for fiber digestion in the rumen. The feeding levels of the PP silage‐based concentrate did not change the amount of VFA production in the rumen and the DM digestibility.     

Processing index of barley grain and dietary undigested neutral detergent fiber concentration affected chewing behavior,ruminal pH,and total tract nutrient digestibility of heifers fed a high-grain diet

The objective of this study was to investigate the effects of processing index (PI) of barley grain and dietary undigested neutral detergent fiber (uNDF) concentration on dry matter (DM) intake, chewing activity, ruminal pH and fermentation characteristics, total tract digestibility, gastrointestinal barrier function, and blood metabolites of finishing beef heifers. The PI was measured as the density after processing expressed as a percentage of the density before processing, and a smaller PI equates to a more extensively processed. Six ruminally cannulated heifers (average body weight, 715 ± 29 kg) were used in a 6 × 6 Latin square design with three PI (65%, 75%, and 85%) × 2 uNDF concentration (low and high; 4.6% vs. 5.6% of DM) factorial arrangement. The heifers were fed ad libitum a total mixed ration consisting of 10% barley silage (low uNDF), or 5% silage and 5% straw (high uNDF), 87% dry-rolled barley grain, and 3% mineral and vitamin supplements. Interactions (P < 0.01) of PI × uNDF were observed for DM intake, ruminating and total chewing time, and DM digestibility in the total digestive tract. Intake of DM, organic matter (OM), starch, and crude protein (CP) did not differ (P > 0.14) between low and high uNDF diets, but intakes of NDF and acid detergent fiber were greater (P = 0.01) for high uNDF diets regardless of barley PI. Heifers fed high uNDF diets had longer (P = 0.05) eating times (min/d or min/kg DM) and tended (P = 0.10) to have longer total chewing times (min/kg DM) than those fed low uNDF diets. Additionally, heifers sorted (P = 0.01) against long particles (>19 mm) for high uNDF diets but not for low uNDF diets. Altering PI of barley grain did not affect (P > 0.12) total volatile fatty acid (VFA) concentration, molar percentages of individual VFA, or duration of ruminal pH < 5.8 and <5.6. Total VFA concentration was less (P = 0.01), acetate percentage was greater (P = 0.01), and duration of ruminal pH < 5.8 and <5.6 was less (P = 0.05) for high compared with low uNDF diets. Digestibility of DM, OM, and CP was greater (P = 0.02) for low vs. high uNDF diets with PI of 65% and 75%, with no difference between low and high uNDF diets at PI of 85%. Blood metabolites and gastrointestinal tract barrier function were not affected (P ≥ 0.10) by the treatments. These results suggest that increasing dietary uNDF concentration is an effective strategy to improve ruminal pH status in finishing cattle, regardless of the extent of grain processing, whereas manipulating the extent of barley processing did not reduce the risk of ruminal acidosis.     

Intake and ruminal digestion determined using omasal and reticular digesta samples in cattle fed diets containing sugar cane in natura or ensiled sugar cane compared with maize silage

Sugar cane is widely used in an in natura forage in tropical countries, but the adoption of silage methods facilitates the preservation of its nutritional value and improves the logistics of its use. To explain differences in performance using alternative forages, it is important to conduct studies that evaluate the various digestion sites for the nutrients provided in diets. However, considering that the collection of omasal digesta is quite laborious and requires the use of a vacuum pump, reticular sampling has been suggested as a promising alternative. Thus, the objective of this study was to evaluate the intake and ruminal digestibility obtained from samples of digesta collected in the reticulum and omasum of cattle fed different diets. Five rumen-fistulated crossbred cattle with an average initial live weight of 336±16.6 kg were used, being distributed in a 5×5 Latin square design. Five diets were evaluated, which contained 60% forage and 40% concentrate on dry matter basis using different forages: maize silage (CS); sugar cane in natura (SCIN); sugar cane silage (SCS0%); sugar cane silage treated with 0.4% calcium oxide (SCS0.4%) or 0.8% calcium oxide (SCS0.8%) on wet basis. The percentage of crude protein (CP) in all of the forages was corrected to 11% based on dry matter (DM) using a mixture of urea/ammonium sulfate (9:1). Six collections of reticular and omasal digesta were obtained over three days at 12 h intervals. To calculate the flow of reticular and omasal nutrients, a double marker system was employed, using cobalt–EDTA and indigestible neutral detergent fiber (NDFi) as markers. The reticular and omasal digesta were similar (P>0.05) to estimate ruminal digestibility of DM, organic matter (OM), CP, neutral detergent fiber (NDF) and non-fiber carbohydrates (NFC). However, the ruminal digestibility of ether extract (EE) and the intestinal digestibility of CP and EE differed (P<0.05) between sampling sites. The results indicate that the omasal digesta is more suitable than the reticular digesta for measuring the ruminal digestion of diet components.     

Voluntary feed intake, acid-base balance and partitioning of urinary nitrogen in lambs fed corn silage with added sodium bicarbonate or sodium sesquicarbonate

An experiment with growing lambs was designed to test the hypothesis that alterations in blood acid-base status would influence intake of corn silage. Six wethers (29 kg) were fed a diet of corn silage (36% DM, 8% CP) supplemented with 1.25% urea and .2% sulfur. At feeding time, sodium bicarbonate (NaHCO3) and sodium sesquicarbonate (NaSC) were added to the silage at levels of 0, 2% or 4% of diet DM. The treatments were arranged as a 2 x 3 factorial, and the study was conducted as a 6 x 4 incomplete latin square with four 17-d periods. Voluntary intake of OM was not different (P greater than .05) between NaHCO3 (1,008 g/d) and NaSC (1,041 g/d). There was no significant interaction between type of buffer (NaHCO3 or NaSC) and level of buffer on any of the variables measured. The progressive increase in buffer load did not alter feed intake (P greater than .05), although there was a quadratic response (P less than .05) in urine pH and a linear increase (P less than .01) in blood HCO3- 2 h after feeding. There was no evidence that lambs fed corn silage experienced metabolic acid stress. Urinary excretion of ammonia and urea were indicative of changes, although not pronounced, in ammoniuria and ureapoiesis in response to bicarbonate loading. This study implies that corn silage imposes no "acid stress" on lambs and, consequently, that there is no nutritional benefit in adding buffers to corn silage for sheep.     

Effect of field pea (Pisum sativum L.) level on intake,digestion, ruminal fermentation and in vitro gas production in sheep fed maintenance diets

The objective of this study was the characterization of the nutritive value, ruminal fermentation and nutrient digestibility of field pea (Pisum sativum L.) hay (FPH) by‐product through in situ, in vitro and in vivo tests. A FPH diet was administered ad libitum to four sheep (live weight (LW) 38.0 ± 2.0 kg) at four inclusion levels (0, 25, 50 and 75%) over a conventional sorghum grain/oat straw ration in a 4 × 4 Latin square design. The in situ degradability of FPH was 67% dry matter (DM), 71% crude protein and 66% neutral detergent fiber (NDF). The inclusion of FPH did not affect (P ≥ 0.05) the DM (61 ± 0.4 g/LW^0.75/day) and organic matter (OM) intake (56 ± 0.7 g/LW^0.75/day). Total DM digestibility (68 ± 2.5%), OM (70 ± 3%), and NDF (60 ± 3%), were not different (P ≥ 0.05) between control and FPH inclusion diets. The diet had no effect on ruminal pH, ruminal ammonia concentration, total and individual volatile fatty acids. The chemical composition and sheep intake behavior indicate that FPH by‐product is medium quality forage when incorporated in maintenance rations.     

Dry Matter Intake and Apparent Digestibility of Nutrients in the Ration of Mangalarga Marchador Weanling Horses Fed Sorghum Silage Versus Grass Hay

In central Brazil, there are two well-defined climatic periods, the rain and the dry season, the latter being marked by massive forage shortages in pastures. In this context, forage conservation such as making hay and silage for herbivores is imperative during the dry season. Grass hay is most commonly used for horses, but sorghum silage is often used for ruminants. The objective was to compare the nutrient digestibility, fecal production, and dry matter intake (DMI) of sorghum silage (Sorghum bicolor l. Moench CV. BRS 655) to that of vaquero hay (Cynodon CV. 90160 CD × CV. Mirage). Twelve Mangalarga Marchador fillies (8 months of age) were divided into two groups: S (sorghum silage, n = 6) and F (vaquero hay, n = 6). The ration was formulated to supply 3.0% body weight in dry matter (DM) per day, with a forage:concentrate ratio of 50:50 on a DM basis. The concentrate used was a corn-based ration formulated to meet or exceed requirements for growth when fed at 1.5% body weight DM to young horses. The animals were housed in individual stalls (3 × 3m) for a period of 25 days, with 21 days for adaptation, followed by 4 days of total collection of feces. During the collection period, an external marker of digestibility, Purified and Enriched Lignin (LIPE), was added to the concentrate as an external marker to determine the apparent digestibility coefficients of DM, crude protein, gross energy, neutral detergent fiber, acid detergent fiber, hemicelluloses, and cellulose. The forage DMI was calculated by subtracting the quantity supplied at each meal minus the amount of forage that was not eaten by the next meal (orts). The measures of digestibility of the sorghum silage were not different (P > .05) from that of vaquero hay. However, DMI of the sorghum silage was lower (P < .05) than the vaquero hay and may be of concern if fed for prolonged periods of time and not supplemented with carefully balanced concentrates. Purified and Enriched Lignin can be used as a marker for evaluation of digestibility of nutrients in weanling horses.