Reduction of 3-methylindole production and prevention of acute bovine pulmonary edema and emphysema with lasalocid

A study was conducted to determine the dose of lasalocid that would effectively reduce ruminal conversion of tryptophan (TRP) to 3-methylindole (3MI) and prevent the development of acute bovine pulmonary edema and emphysema (ABPE). After adaptation to a maintenance diet for 3 wk, 20 mature beef cows were randomly divided into four groups of five cows each and fed 0, 200, 400 or 600 mg lasalocid X head-1 X d-1 in .5 kg ground barley for the 12-d experimental period. In vitro conversion of TRP to 3MI and indole by ruminal fluid and volatile fatty acid (VFA) concentrations were determined on d 0, 2, 4, 6 and 12. On d 6, an oral dose of .35 g TRP/kg body weight was given to induce ABPE, and ruminal production of 3MI and indole was determined at intervals thereafter. Formation of 3MI was sharply reduced (P less than .01) both in vitro and in vivo by lasalocid treatment at 200 mg X head-1 X d-1. Further suppression of 3MI production occurred as the lasalocid dose was increased (P less than .05). Linear (P less than .0001) and quadratic (P less than .002) components were determined for the relationship between lasalocid dose and 3MI production. Indole formation was variable, but tended to increase (P less than .05) with increasing lasalocid dose. Cows that received no lasalocid developed moderate to severe clinical signs of ABPE and three cows died of acute lung disease. Lasalocid treatment at all levels prevented ABPE. Lasalocid decreased ruminal acetate and butyrate, and increased propionate concentration (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of monensin on monovalent ion metabolism and tissue concentrations in lambs

A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of sodium (Na) and potassium (K) and to examine changes in tissue and ruminal fluid concentrations of these minerals in lambs. Eight lambs (39 kg) were used in trial 1 and 10 lambs (37 kg) were used in trial 2. Animals were used in randomized block designs, blocked by weight, and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections for mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were obtained on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Sodium retention decreased (P less than .05) 86.2% when monensin was fed. Apparent K absorption increased (P less than .05) 16.7%, while K retention increased (P less than .10) 52.6% when monensin was fed. In lambs fed monensin, ileal Na decreased (P less than .10) 13.8%. These results indicate that dietary monensin alters the metabolism of Na and K in lambs.     

Net absorption of 3-methylindole and indole in cattle after oral administration of L-tryptophan

The time course and quantity of 3-methylindole (3MI) and indole absorbed after oral administration of L-tryptophan (TRP) was determined in 2 steers. The relationship between the appearance of 3MI and indole in the rumen and blood plasma to absorption of 3MI and indole was also studied. Two Hereford X Angus steers with portal vein, mesenteric vein, and femoral (steer 1) or iliac (steer 2) artery catheters were used. Absorption rates from the portal drained viscera (net absorption) of 3MI and indole were determined by the product of portal and arterial concentration difference and blood flow. Blood flow was determined by primed continuous infusion of p-aminohippuric acid into a mesenteric vein. Three absorption measurements 30 minutes apart were taken at midpoint times of 0, 12, 24, 36, and 48 hours after oral administration of 0.4 g of TRP/kg of body weight. Steer 1 was dosed twice resulting in a total of 45 absorption measurements. Net absorption of 3MI and indole peaked at an average of 1.05 and 0.81 g/hr, respectively. By 48 hours, 29.2% and 15.3% of the TRP dose were accounted for by 3MI and indole absorption, respectively. Closed system in vitro incubations of TRP with ruminal fluid from the same 2 steers resulted in a TRP to 3MI conversion of 23.2% and a TRP to indole conversion of 10.7%. Net absorption of 3MI and indole closely followed and was correlated with concentration of 3MI and indole in ruminal fluid and blood plasma.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of monensin on Mg, Ca, P and Zn metabolism and tissue concentrations in lambs

A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of magnesium (Mg), phosphorus (P), calcium (Ca) and zinc (Zn) and to determine mineral changes in tissue and ruminal fluid. Eight lambs (39 kg) were used in trial 1, and 10 lambs (37 kg) were used in trial 2. Animals were blocked by weight and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections to determine mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were taken on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Monensin supplementation increased (P less than .05) Mg retention 42.0%. Urinary Ca excretion decreased (P less than .05) 60.0% when monensin was fed. Monensin supplementation decreased (P less than .05) liver Ca and bone Ca, 45.5 and 2.9%, respectively. Apparent P digestibility increased (P less than .05) 40.0% and P retention increased (P less than .10) 26.8% due to monensin supplementation. Both apparent absorption and retention of Zn increased (P less than .01) 50.0 and 45.0%, respectively, with monensin supplementation. Ruminal fluid Zn concentrations decreased (P less than .05) 33.0% with the addition of monensin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of laidlomycin propionate and monensin on the in vitro mixed ruminal microorganism fermentation.

The objective of this study was to compare the effects of laidlomycin propionate and monensin on the in vitro fermentation of ground corn, Trypticase, or alfalfa hay by mixed ruminal microorganisms. Ruminal fluid was collected from two steers fed 9.27 kg DM of a high-concentrate (62.2% ground corn and 17.4% cottonseed hulls) diet per day and composited. In the first study, no ionophore was included in the diet; the diet in the second study contained 11.1 g of laidlomycin propionate per ton of feed. The animals were allowed an adjustment period of 14 d for each dietary treatment before samples were collected. When ruminal fluid from unadapted animals was used, both monensin and laidlomycin propionate decreased (P<.05) CH4 concentration and the acetate:propionate ratio with ground corn and alfalfa hay. Monensin reduced (P<.05) in vitro dry matter disappearance of alfalfa and increased (P<.05) final pH in the ground corn and alfalfa hay fermentations. Both laidlomycin propionate and monensin decreased (P<.05) concentrations of acetate, propionate, isobutyrate, isovalerate, CH4, and NH3 in Trypticase fermentations. When ruminal fluid from adapted animals was used, both ionophores still reduced the concentrations of most fermentation products. However, there was generally less inhibition compared with fermentations inoculated with unadapted mixed ruminal microorganisms. In the presence of 5 mM maltose, mixed ruminal bacteria produced high concentrations (10 to 11 mM) of lactate, and addition of both ionophores to these fermentations was effective in reducing (P<.05) lactate production. In conclusion, laidlomycin propionate alters the mixed ruminal microorganism fermentation in a manner similar to monensin, but, at the concentrations used in this study, monensin seemed to be a more potent inhibitor.     

Site of 3-methylindole and indole absorption in steers after ruminal administration of L-tryptophan

To determine the site of 3-methylindole (3MI) and indole absorption in cattle after ruminal administration of L-tryptophan (TRP), 4 Holstein steers were given 0.4 g of TRP/kg of body weight directly into the rumen through ruminal cannulas. Chromium EDTA and ruthenium phenanthroline were added to feedings of orchard grass hay twice a day for measurement of fluid and particulate flow to the duodenum, respectively. Passage of 3MI and indole (products of ruminal fermentation of TRP) to the duodenum was determined by the products of digesta flow rate and concentration in duodenal contents. Ruminal fluid, duodenal contents, and jugular blood were sampled at postdosing hours (PDH) 0, 6, 12, 18, 24, 36, and 72 for analysis of 3MI, indole, and digesta flow markers. Ruminal, duodenal, and jugular plasma concentrations of 3MI and indole peaked at PDH 12 to 24 at 152.4 and 25.9; 15.5 and 1.0; and 8.7 and 2.2 mg/L, respectively. Most 3MI and indole reaching the duodenum were associated with the particulate phase of the digesta. On a molar basis, total passage of 3MI to the duodenum during 72 hours amounted to 1.0% of the TRP dose for 3MI and 0.1% of the TRP dose for indole. Absorption of 3MI and indole in these steers was almost entirely proximal to the duodenum.     

Effect of monensin and supplemental hay on ruminal 3-methylindole formation in adult cows after abrupt change to lush pasture.

The effect of feeding monensin, with or without dry hay plus wilted forage, on ruminal formation of 3-methylindole (3MI) was investigated in pastured cattle. Eighty-two cows were allotted to 3 groups. Cows of group-1 served as controls and were given a daily energy supplement (1 kg/head) without monensin for 1 day before and for 7 days after being allowed access to lush pasture. Cows of groups 2 and 3 were given the same daily energy supplement, which also contained monensin (200 mg/kg of supplement). Cows of group 3 also were fed dry hay for 5 days before the start of the study and continued to be given supplemental hay for 4 days after being allowed access to lush pasture containing a layer of wilted forage. Ruminal 3MI and indole concentrations increased on day 1 after all groups were allowed access to lush pasture. By day 7, 3MI concentration in all cows had decreased to pregrazing concentration. Indole concentration did not reach pregrazing concentration until day 10 for cows of groups 1 and 2. Group-3 cows had pregrazing indole concentration on day 7. Ruminal indole concentration did not differ (P greater than 0.05) between groups 1 and 2. Ruminal indole concentration was lower (P less than 0.01) in group-3 cows on all sample collection days, except day 10, compared with that in the other groups. Monensin reduced (P less than 0.01) 3MI formation on days 1 and 7 in group-2 cows, compared with group-1 cows. Group-3 cows had lower 3MI concentration than did group-1 cows (P less than 0.01) on days -1, 1, 4, and 7.(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance, methanogenesis and nitrogen metabolism of finishing steers fed monensin and nickel

Sixty-four Angus steers initially averaging 354 kg were allotted to a 2 X 2 factorial arrangement of treatments to determine the effects of dietary Ni (0 or 5 mg/kg supplemental), monensin (0 or 33 mg/kg) and their possible interaction on performance, methane production and N metabolism. The basal diet was a high energy, corn-cottonseed hull based diet containing 10.2% crude protein and .30 mg/kg Ni on a dry matter basis. Monensin reduced (P less than .05) feed intake, did not affect average daily gain and improved (P less than .05) feed conversion over the 102-d study. Nickel supplementation did not significantly alter or interact with monensin to affect steer performance. However, steers fed Ni tended to have higher average daily gains and improved feed conversions. Monensin decreased (P less than .05) in vitro methane production, altered several carcass traits, increased (P less than .05) molar proportion of ruminal propionate and decreased (P less than .05) molar proportion of ruminal acetate. Nickel did not alter methane production, carcass characteristics or ruminal volatile fatty acid proportions. Both monensin and Ni increased (P less than .05) ruminal fluid urease activity when samples were obtained before feeding. A significant monensin X Ni interaction was found to affect ruminal epithelial urease activity. Monensin increased ruminal epithelial urease in steers not receiving supplemental Ni, but had no effect on ruminal epithelial urease activity in steers fed supplemental Ni. Ruminal fluid protein and ammonia-N were decreased (P less than .05) by monensin. Results of this study indicate that Ni may interact with monensin to affect ruminal epithelial urease activity but not performance or methane production in finishing steers.     

Effects of a monensin ruminal delivery device on daily gain, forage intake and ruminal fermentation of steers grazing irrigated winter wheat pasture

Two trials evaluated the effects of a monensin ruminal delivery device (MRDD) on steers grazing winter wheat pasture. In Trial 1, 60 Hereford steers (initial wt 238.5 kg) grazed a 21.9-ha paddock of Vona-variety winter wheat for 112 d. Steers were assigned to either MRDD or control (C) treatments in a randomized complete block design. In Trial 2, eight ruminally cannulated steers (avg wt 234.4 kg) grazed a 2.4-ha paddock of Vona-variety wheat and were assigned randomly to either MRDD or C treatments. Three 11-d collection periods were conducted during early February, early March and early April. Chromic oxide was dosed to determine fecal output, and ruminal samples were collected on d 6 of each period. Nylon bags containing ground wheat forage were incubated ruminally beginning on d 8. In Trial 1, steers with MRDD tended (P less than .11) to gain more weight than C steers (.44 vs .38 kg/d). In Trial 2, wheat forage intake, in situ DM disappearance, ruminal pH, ruminal ammonia concentrations and ruminal proportions of acetate and total VFA concentrations were not affected by treatment. Ruminal proportions of propionate were increased (P less than .05) slightly by MRDD (20.3 and 19.2 mol/100 mol for MRDD and C, respectively). Butyrate proportions in ruminal samples were decreased (P less than .05) by MRDD during March but not in other sampling periods. Ruminal fluid chlorophyll concentration was less (P less than .05) for MRDD-treated vs C steers during early March but was greater (P less than .10) for MRDD-treated steers during early April. The MRDD shows promise as a method of supplying monensin to cattle grazing winter wheat forage.     

Milk residues and performance of lactating dairy cows administered high doses of monensin

Milk residues and performance were evaluated in lactating cows that were fed up to 10 times the recommended dose of monensin. Following an acclimatization period of 14 d, during which cows were fed a standard lactating cow total mixed ration containing 24 ppm monensin, 18 lactating Holstein dairy cows were grouped according to the level of feed intake and then randomly assigned within each group to 1 of 3 challenge rations delivering 72, 144, and 240 ppm monensin. Outcome measurements included individual cow daily feed intakes, daily milk production, body weights, and monensin residues in composite milk samples from each cow. There were no detectable monensin residues (< 0.005 microg/mL) in any of the milk samples collected. Lactating cows receiving a dose of 72 ppm monensin exhibited up to a 20% reduction in dry matter intake, and a 5% to 15% drop in milk production from the pre-challenge period. Cows receiving doses of 144 and 240 ppm monensin exhibited rapid decreases in feed intake of up to 50% by the 2nd d and milk production losses of up to 20% and 30%, respectively, within 4 d. Lactating cows receiving up to 4865 mg monensin per day had no detectable monensin residues (< 0.005 microg/mL) in any of the milk samples collected. Results of this study confirm that food products derived from lactating dairy cattle receiving monensin at recommended levels are safe for human consumption.     

Monensin effects on digestibility, ruminal protein escape and microbial protein synthesis on high-fiber diets

The influence of monensin level (0, 6.1, 12.2, 18.3 and 36.6 ppm) on diet fiber digestibility, microbial protein synthesis and ruminal escape of dietary protein was evaluated in two steer metabolism trials. A growth trial was conducted to study possible interactions of forage quality and monensin level. In metabolism trial 1, four ruminal-cannulated steers were assigned to four monensin levels in a 4 X 4 Latin square design to measure fiber digestibility, rate of passage and protein metabolism. In metabolism trial 2, five duodenal-cannulated steers were assigned to five monensin levels in a 5 X 5 Latin square design to measure fiber digestibility, bacterial N flow and plant N flow. In the two metabolism trials, the level of monensin influenced organic matter (OM) digestibility, neutral detergent fiber (NDF) digestibility and ruminal NDF digestibility quadratically, with the intermediate levels of monensin being superior either to the high level of monensin or no monensin. A quadratic increase in particulate disappearance rate (P = .09) and no effect (P = .95) on liquid disappearance were also observed in trial 1. In trial 1, monensin level quadratically decreased (P = .10) the bacterial protein concentration and increased (P = .02) the ratio of total N:diaminopimilic acid in whole rumen contents. In trial 2, no overall difference in duodenal N flow (P = .64) or flow of individual amino acids (P = .46) was observed. In the growth trial, no interaction of cornstalk quality and monensin was observed (P less than .38).(ABSTRACT TRUNCATED AT 250 WORDS)     

饲粮添加海南霉素和莫能菌素对奶牛瘤胃发酵特性和氮平衡的影响

本研究旨在探究饲粮添加海南霉素和莫能菌素对奶牛瘤胃发酵特性和氮平衡的影响.选用3头体重为(460.0±20.6)kg、装有永久性瘤胃瘘管的成年荷斯坦奶牛,采用3×3拉丁方试验设计,对照组饲喂基础饲粮,试验组分别饲喂在基础饲粮添加20 mg/d海南霉素和350 mg/d莫能菌素的试验饲粮.结果表明:饲粮添加海南霉素和莫能菌素没有显著影响瘤胃液pH和丁酸含量(P＞0.05),但显著降低了瘤胃液总挥发性脂肪酸浓度、乙酸含量、乙酸/丙酸和氨态氮浓度(P＜0.05).与对照组相比,海南霉素组和莫能菌素组丙酸含量分别提高了16.26％和15.79％(P ＜0.01).饲粮添加海南霉素和莫能菌素显著降低了尿囊素排出量、尿嘌呤衍生物排出量和微生物氮产量(P＜0.05).饲粮添加海南霉素和莫能菌素也降低了粪氮量和尿氮量(P＜0.05),提高了沉积氮量(P＜0.01).与对照组相比,海南霉素组和莫能菌素组的表观氮消化率分别提高了5.61％和7.05％(P =0.03).总之,与莫能菌素相似,饲粮添加海南霉素可以改变瘤胃发酵模式,使其更趋向于丙酸型发酵,并且能够提高氮利用效率.     

Changes in ruminal concentrations of microbial ammonia and amino acids due to monensin and time

The effect of monensin (33 mg/kg) and no monensin on distribution of ammonia and free amino acids in fluid and particulate phases of ruminal contents was studied. Two Jersey cows and two Angus-Hereford steers, weighing approximately 350 kg and each containing a ruminal cannula were meal fed a 65% concentrate diet for two periods. Feed was available for 30 min; any feed not eaten was removed after this time. Whole ruminal contents were sampled before feeding, immediately after feed removal and 1, 2, 3, 4, 6, 8, 10 and 12 h after feed removal. A crossover design with split-plot in time was used with four observations per time point per treatment. Extracellular (E) ammonia and amino acids were determined on high speed supernatants of strained ruminal fluid. Total (T) ammonia and amino acids were obtained by lysing microbial cells with 1% cetyltrimethylammonium bromide (CTAB) and one freeze treatment before centrifugation. Intracellular (I) amino acids and ammonia were determined as T minus E. Squeezed particles were suspended in .1 N HCl containing 1% CTAB. Total and E ammonia were higher throughout the study for no monensin vs monensin (P less than .05). Intracellular ammonia was low (.03 to 1 mM) and did not change (P greater than .10) across time for either dietary treatment. Intracellular amino acids ranged from 1.2 to 4.5 mM and were higher (P less than .05) than E amino acids (.9 to 2.2 mM) for both diets immediately after feeding. Monensin did not significantly lower (P greater than .10) T amino acids compared with no monensin throughout sampling (2.6 and 3.1 mM, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance, blood and ruminal characteristics of cows receiving monensin and a magnesium supplement

Forty-eight Angus and Hereford cows were used in a completely random design with a 2 X 2 factorial arrangement of treatments to evaluate the effects of monensin and two sources of Mg on performance, ruminal characteristics and mineral status of mature beef cows. Cows were fed wheat straw treated with NH3 during late gestation and straw treated with NH3 plus bromegrass haylage after calving along with a protein supplement that contained either MgO (7.5 g/kg) or MgSO4 (11 g/kg). One half of the cows received monensin (1 g/kg) in their protein supplement. During the precalving period, MgO without monensin increased (P less than .01) plasma Mg compared with Mg in plasma of cows receiving MgSO4 or MgO with monensin. Magnesium oxide also increased cow weight gains during late gestation (P less than .05) compared with weight gains of cows supplemented with MgSO4, but magnesium source had no effect on weight gain postcalving. Plasma glucose was increased by monensin (P less than .05) and by MgSO4 (P less than .01) during early lactation. Monensin increased the proportion of propionate before (P less than .05) and after (P less than .10) calving in the ruminal fluid of cows. Monensin also increased (P less than .05) cow weight gain precalving and tended to decrease (P less than .10) milk fat in lactating cows. Calf weight gains were not affected by treatment of dam. Magnesium oxide appeared to have higher Mg bioavailability than MgSO4 for cows precalving, but Mg bioavailability was not different postcalving. Monensin increased cow weight gains precalving and improved feed efficiency postcalving.     

The effect of a monensin ruminal delivery device on performance of cattle grazing pasture

A total of 28 trials utilizing 2,262 steers and heifers were conducted to evaluate a sustained monensin2 ruminal delivery device (RDD) on the daily gain of grazing cattle. Five series of trials, with four to eight trials per series within a grazing season, were conducted to evaluate the daily gain response under different environmental conditions and locations. Pastures grazed included both summer (cool- and warm-season grasses and native range) and winter (rye, ryegrass and wheat) growing pastures. The experimental design for all trials in each of five series was a randomized complete block with initial weight or breed as the blocking factor. The treatments compared in series I, III, IV and V (20 trials) were a control and a single RDD, whereas in series II (eight trials), a 2 x 2 factorial was utilized that compared RDD and estradiol 17-beta controlled release implants. In the five series of trials, the monensin RDD increased daily gain .04 (P = .002), .03 (P = .07), .09 (P = .01), .05 (P = .10) and .08 kg (P = .04) compared with the controls. Use of the RDD provided an effective method of achieving consistent monensin delivery and weight gain improvement without requiring the extra labor needed to administer monensin via hand-feeding or self-feeding supplements, blocks or loose mineral.     

Ruminal and plasma concentrations of 3-methylindole associated with tryptophan-induced pulmonary edema and emphysema in cattle.

Five Hereford cows were given an intraruminal dose of L-tryptophan (0.35 g/kg of body weight), and 2 cows were used as controls. Of the 5 treated cows, 3 developed clinical signs of interstitial pul monary edema, and emphysema and severe pulmonary lesions were seen at necropsy after 96 hours. Another cow developed moderate clinical signs and pulmonary lesions, and the remaining cow had few clinical signs and mild pulmonary lesions. The severity of clinical signs in each cow was related to the severity of pulmonary lesions at necropsy. The 3-methylindole (3MI) was present in ruminal fluid and plasma within 6 hours after administration of tryptophan, and the concentrations increased to 3.0 and 9.0 mug/ml within 12 to 24 hours. Severity of pulmonary lesions was related to maximal concentration and duration of 3MI in the plasma. At necropsy, gross lesions were characterized by diffuse, pulmonary edema and interstital emphysema; and the lungs were dark red, firm, and heavier than normal. Predominant microscopic changes included accumulation of proteinaceous residue, hypertrophy and hyperplasia of alveolar lining epithelium, thickening of alveolar septums, and emphysematous thickening of interstitial tissues. These changes were similar to previously reported 3MI-induced pulmonary lesions. The presence of 3MI in ruminal fluid and plasma after administration of tryptophan and the relationship between concentration of 3MI and severity of clinical signs indicate that 3MI is the principal metabolite of ruminal fermentation which leads to the development of acute pulmonary edema and emphysema in cattle given tryptophan.     

Effect of the ionophore antibiotic monensin on the ruminal biotransformation of benzimidazole anthelmintics

The benzimidazole (BZD) anthelmintics, netobimin (NTB) pro-drug and albendazole sulphoxide (ABZSO) are reduced to albendazole (ABZ) by ruminal microflora. The aim of the current work was to evaluate the influence of the ionophore monensin (MON) on the in vitro biotransformation of NTB and ABZSO by sheep ruminal fluid. Ruminal fluid, collected from Corriedale sheep, was preincubated (24 h) either without (control) or with known MON concentrations (0.5, 1.5 and 3.0 microg/mL) at 38 degrees C under a CO2 atmosphere. Afterwards, aliquots from both MON-pretreated and control ruminal fluid samples were incubated (30 and 60 min) with 2 microg/mL of either NTB or ABZSO. Incubated samples were chemically extracted and analysed by High Performance Liquid Chromatography to quantify the metabolites formed. The rate of ABZ production after 30 min of NTB incubation with control ruminal fluid was 0.023 microg/min. Conversely, the rates of ABZ formation were significantly (P<0.05) lower (0.009, 0.011 and 0.013 microg/min) when NTB was incubated with ruminal fluid pretreated with MON (at 0.5, 1.5 and 3.0 microg/mL, respectively). After both incubation periods, the reduction of ABZSO to ABZ was 22 to 70% lower when the ruminal fluid was preincubated with the different MON concentrations. The lower ABZ production observed in the presence of MON may result in a modified availability of this molecule in the gastrointestinal (GI) tract and hence, on its anthelmintic efficacy against GI nematodes.     

Sugar beet mash silage as a component of a total-mixed-ration for dairy cows--effects on parameters of digestion and animal performance.

Sugar beet mash silage (BMS) was offered in amounts up to 35% of DM to dairy cows as a component of a total-mixed-ration (TMR). Barley and molasses in the control ration were replaced by BMS half in ration BMS 1/2 and in total in ration BMS 1/1 on the basis of the calculated contents of net energy for lactation. Two trials were carried out. In trial I each ration was tested on parameters of rumen fermentation and digestibility of crude nutrients using 4 Holstein cows with rumen fistula. Chewing activity was tested on 2 Holstein cows for each ration. With the BMS rations the ruminal NH3 concentration was lower and the drop in pH was less than in the control ration. The pattern of volatile fatty acids in the rumen fluid from the BMS groups tended towards more propionic and butyric acid. The feeding of BMS showed no negative impact on chewing and rumination. Energy digestibility raised significantly from 59.8% in the control ration to 72.6% in the BMS 1/1 ration. In trial II the same rations were fed in a change-overdesign to a herd of 24 Holstein cows to test feed intake and animal performance. The results showed no significant effects of BMS rations on DM intake and milk production. The results of both trials indicate that even high amounts of cereals can be replaced by BMS without negative effects on rumen fermentation, milk yield and milk composition with slight drop in fat content. For a better handling of BMS, it is of advantage to include it in a TMR.     

Influence of lysocellin and monensin on mineral metabolism of steers fed forage-based diets

Studies were conducted to determine the effects of lysocellin and monensin on mineral metabolism of steers fed forage-based diets. In each study treatments consisted of 1) control, 2) 100 mg lysocellin/d, 3) 200 mg lysocellin/d and 4) 200 mg monensin/d. Twenty-four growing Hereford steers were used in each of two experiments to evaluate the effects of ionophore feeding on plasma and ruminal soluble mineral concentrations. Steers were fed individually greenchop (tall fescue and bermudagrass) ad libitum and .91 kg/d of a corn-trace mineral salt-ionophore supplement. Plasma and ruminal fluid samples were obtained on d 28 and 84 in both studies. Ruminal concentrations of soluble phosphorus (P) and iron (Fe) were higher (P less than .05), whereas soluble manganese (Mn) was lower (P less than .01), in steers fed lysocellin than in controls. Steers fed lysocellin had higher (P less than .05) plasma magnesium (Mg) concentrations than control steers. Plasma and ruminal soluble mineral concentrations generally were similar for the monensin and 200 mg lysocellin treatments. Two additional studies were conducted to determine the effects of lysocellin and monensin on macromineral apparent absorption and retention in steers fed tall fescue greenchop. Steers were adjusted to their diets for 28 d and then placed in metabolism crates for a 6-d acclimation followed by a 5-d collection of urine and feces. Percent apparent absorption of calcium (Ca), potassium (K), Mg and P was higher (P less than .05), whereas sodium (Na) absorption was lower (P less than .05), in steers fed lysocellin than in controls. Mineral absorption was similar in steers fed 200 mg lysocellin or monensin. Calcium (P less than .05) and K (P less than .10) retention (percent of intake) was increased by ionophore feeding. Results indicate that lysocellin and monensin alter apparent absorption and retention of certain minerals in steers fed forage-based diets.     

Effects of adding polyclonal antibody preparations on ruminal fermentation patterns and digestibility of cows fed different energy sources

Nine ruminally cannulated cows fed different energy sources were used to evaluate an avian-derived polyclonal antibody preparation (PAP-MV) against the specific ruminal bacteria Streptococcus bovis, Fusobacterium necrophorum, Clostridium aminophilum, Peptostreptococcus anaerobius, and Clostridium sticklandii and monensin (MON) on ruminal fermentation patterns and in vivo digestibility. The experimental design was three 3 × 3 Latin squares distinguished by the main energy source in the diet [dry-ground corn grain (CG), high-moisture corn silage (HMCS), or citrus pulp (CiPu)]. Inside each Latin square, animals received one of the feed additives per period [none (CON), MON, or PAP-MV]. Dry matter intake and ruminal fermentation variables such as pH, total short-chain fatty acids (tSCFA), which included acetate, propionate, and butyrate, as well as lactic acid and NH(3)-N concentration were analyzed in this trial. Total tract DM apparent digestibility and its fractions were estimated using chromic oxide as an external marker. Each experimental period lasted 21 d. Ruminal fluid sampling was carried out on the last day of the period at 0, 2, 4, 6, 8, 10, and 12 h after the morning meal. Ruminal pH was higher (P = 0.006) 4 h postfeeding in MON and PAP-MV groups when compared with CON. Acetate:propionate ratio was greater in PAP-MV compared with MON across sampling times. Polyclonal antibodies did not alter (P > 0.05) tSCFA, molar proportion of acetate and butyrate, or lactic acid and NH(3)-N concentration. Ruminal pH was higher (P = 0.01), 4 h postfeeding in CiPu diets compared with CG and HMCS. There was no interaction between feed additive and energy source (P > 0.05) for any of the digestibility coefficients analyzed. Starch digestibility was less (P = 0.008) in PAP-MV when compared with CON and MON. In relation to energy sources, NDF digestibility was greater (P = 0.007) in CG and CiPu vs. the HMCS diet. The digestibility of ADF was greater (P = 0.002) in CiPu diets followed by CG and HMCS. Feeding PAP-MV or monensin altered ruminal fermentation patterns and digestive function in cows; however, those changes were independent of the main energy source of the diet.