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)     

Lysocellin effects on growth performance, ruminal fermentation, nutrient digestibility and nitrogen metabolism in steers fed forage diets

Studies were conducted to determine the effects of lysocellin on growth performance and metabolism of steers fed forage-based diets. Treatments in all experiments consisted of 1) control, 2) 100 mg lysocellin/d, 3) 200 mg lysocellin/d and 4) 200 mg monensin/d. In each of two 90-d performance studies, 24 Hereford steers were individually fed greenchop (fungus-free tall fescue and Coastal and Tifton-44 bermudagrass) ad libitum and .91 kg/d of a corn-trace mineral salt supplement. In Exp. 1, tall fescue was fed from d 1 to 45 and bermudagrass from d 46 to 90. Bermudagrass was offered during d 1 to 45 and tall fescue during d 46 to 90 in Exp. 2. Lysocellin improved gain (Exp. 1, P less than .01) and feed conversion (Exp. 1 and 2 combined, P less than .05), decreased total VFA concentrations (P less than .05), increased molar proportions of propionate, isobutyrate and isovalerate (P less than .01), decreased molar proportions of acetate and butyrate (P less than .01) and lowered acetate:propionate (P less than .01). Two metabolism studies involving a total of 16 Hereford steers were conducted. Steers were fed tall fescue greenchop and .91 kg/d supplement for a 34-d adjustment period followed by a 5-d total collection period. Lysocellin increased N digestibility (P less than .01) and N retention (P less than .06) but did not (P greater than .05) affect DM, NDF or ADF digestibility. Data indicate that lysocellin results in major alterations in ruminal fermentation and can increase growth performance and N retention in steers fed forage-based diets.     

Use of chlortetracycline for treatment of new feedlot cattle

Two 56-d shipping fever trials of similar design were conducted the same season (fall) at Kansas State University (KSU) and at Purdue University (PU) to compare various levels of chlortetracycline (0 or 350 mg X head-1 X d-1 continuously or 1, 2 or 4 g X head-1 X d-1 for the first 14 d). Weanling crossbred steer calves were utilized (210 head of Angus X Simmental, averaging 197 kg, at KSU; 268 head of Angus X Hereford, averaging 192 kg, at PU). For the first 28 d in the KSU trial (October 13 to December 8), cattle that received 4 g X head-1 X d-1 the first 14 d gained more rapidly (P less than .05) than cattle fed 350 mg X head-1 X d-1 continuously or than the controls that received no chlortetracycline (CTC; 1.05 vs .92 or .93 kg/d, respectively). Cattle that received 4 g CTC X head-1 X d-1 for the first 14 d required less (P less than .05) dry matter per kg gain than steers that received 350 mg X head-1 X d-1 continuously over the 56-d period. In the PU trial (October 6 through December 1), all CTC treatments resulted in increased feed efficiency (P less than .05) over the controls through 28 d, and the 4 g X head-1 d-1 for 14 d and 350 mg X head-1 X d-1 continuously, improved feed efficiency over the other groups for the 56-d period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Salinomycin and lasalocid effects on growth rate, mineral metabolism and ruminal fermentation in steers

Two experiments were conducted to determine the effects of salinomycin and lasalocid on metabolism and growth of growing steers. In Exp. 1, 80 Angus steers (228 kg) were assigned to the following treatments: 1) control, 2) 50 mg salinomycin.hd-1.d-1, 3) 100 mg salinomycin.hd-1.d-1 and 4) 250 mg lasalocid.hd-1.d-1. Steers were fed corn silage once daily with allotments based on the amount of silage that each pen of five steers would consume in a 24-h period. In addition, .81 kg/hd of a corn-soybean meal supplement was fed daily during the 112-d study. Daily gains were similar across treatments, but feed intake was lower (P less than .05) for steers fed ionophores. Molar proportions of ruminal acetate were lower (P less than .05) in steers fed ionophores at 28 and 90 d. Ruminal propionate was lower (P less than .05) in control steers at 28 d, but values were similar across treatments on d 90. Plasma copper (Cu) was lower (P less than .05) in control steers on both sampling days. In Exp. 2, 16 Hereford steers were allotted to two blocks of eight animals each and assigned to one of three treatments: 1) control (n = 6), 2) 11 mg salinomycin/kg diet (n = 6) and 3) 33 mg lasalocid/kg diet (n = 4). Following a 28-d adjustment period, apparent absorption and retention of macrominerals and nitrogen (N) were determined during a 5-d collection period. Apparent absorption and retention of N did not differ among treatments when data were analyzed using N intake as a covariate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Administration of monensin in self-fed (salt limiting) dry supplements or on an alternate-day feeding schedule

Two series of trials were conducted to evaluate alternative methods of administering monensin to pasture cattle. In a series of five trials, monensin was incorporated into supplements at 440 mg/kg to provide an average intake of 200 mg X head-1 X d-1 for growing cattle on pasture. Comparisons were made between daily and alternate-day feeding of the supplements. A control treatment consisting of unmedicated supplement fed daily also was included. Monensin at 200 mg/d and 400 mg on alternate days increased gain by .077 (P less than .01) and .082 (P less than .01) kg/d above control-cattle gains (.54 kg daily). Nine pasture trials were conducted to compare the effectiveness of monensin in increasing the daily gain of growing cattle when hand-fed daily in a supplement or self-fed in supplements that contained salt to regulate supplement intake. Desired supplement intakes were approximately .454 kg X head-1 X d-1 in six trials, .68 kg/d in one trial and 1.81 kg/d in two trials. Monensin produced gain increases of .09 kg daily (P less than .01) with both feeding systems. The daily gains of cattle that were hand-fed and self-fed were equal (P greater than .10). Self-fed treatments containing monensin required fewer changes in salt level than self-fed treatments not containing monensin, and the salt levels required to limit intake were generally 25 to 50% lower when monensin was in the supplement.     

Effect of lasalocid on weight gains, ruminal fermentation and forage intake of stocker cattle grazing winter wheat pasture

Fifty fall-weaned heifers with initial weights of 209 kg (yr 1) and 222 kg (yr 2) were used to determine effects of lasalocid on weight gains, forage intake and ruminal fermentation of stocker cattle grazing winter wheat pasture. The heifers grazed a single wheat pasture for about 100 d each year, and were individually fed 1.06 kg of supplement (6 d/wk) pro-rated to supply 0, 100 or 200 mg lasalocid.head-1.d-1. Also, eight mature Hereford steers with large rumen cannula were used to evaluate further effects of lasalocid (0 or 300 mg) on ruminal fermentation during two grazing periods (immature and mature wheat forage) of yr 2 and an additional third year. Daily gains of heifers fed 200 mg lasalocid/d were .11 kg greater (P less than .05) than those of heifers fed 0 or 100 mg lasalocid/d. One hundred milligrams lasalocid did not increase weight gains. Digestibilities of forage dry matter (DM) and organic matter (OM) were similar (P greater than .05) among treatments, and lasalocid did not affect (P greater than .10) forage intake. Ruminal ammonia concentrations (10.57, 15.22 and 17.81 mg/dl +/- 1.71) were increased (P less than .05) by both levels of lasalocid in yr 1, but differences among treatment means of 8.32, 11.95 and 11.66 (SE +/- 1.44) were not significant in yr 2. Lasalocid did not consistently affect total volatile fatty acids concentrations. The acetic:propionic acid ratios in heifers were not different (P greater than .05) among treatments, but were decreased (P less than .10) by lasalocid in cannulated steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of forage level on response of feedlot steers to salinomycin supplementation

Two trials were conducted to evaluate the influence of forage level on the response of feedlot cattle to salinomycin. Diets containing 10, 15 and 20% forage were compared with 0 or 11 mg/kg salinomycin. In trial 1, treatment effects on feedlot performance were evaluated using 108 crossbred steers (295 kg) in a crossover design experiment. There were no salinomycin X forage level interactions (P greater than .20). Weight gain response to salinomycin supplementation averaged 5.4, 5.3 and 6.9%, respectively, for diets containing 10, 15 and 20% forage. Corresponding values for feed conversion response to salinomycin supplementation were 5.1, 3.9 and 5.9%. Averaged across forage level, salinomycin supplementation improved rate of weight gain and feed conversion by 5.9 and 5.2%, respectively (P less than .01). In trial 2, treatment effects on characteristics of ruminal and total tract digestion were evaluated in a 6 X 6 Latin-square design trial involving six crossbred steers (191 kg) with cannulae in the rumen and proximal duodenum. There were no interactions between salinomycin supplementation and forage level on characteristics of ruminal digestion (P greater than .20). Salinomycin supplementation did not influence synthesis of microbial N, ruminal digestion of organic matter, acid detergent fiber and starch, or molar proportions of acetate, propionate and butyrate (P greater than .20). Salinomycin supplementation increased passage of non-ammonia N to the small intestine (5.4%, P less than .10) and increased ruminal escape of feed N (24%, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Reducing phosphorus inputs for grazing Holstein steers

A 2-yr study was conducted to confirm that managed pastures can provide Holstein steers adequate P to meet their daily requirement. Treatments offered were trace mineralized salt with or without additional P. In the first year, 80 Holstein steers (248 kg of BW) were assigned to 4 grazing groups. Treatments were trace mineralized salt only or a 67:33 mixture of trace mineralized salt and dicalcium phosphate. Steers rotationally grazed a cool-season grass/legume mixture for 137 d. Fecal bags were placed on 3 steers from each grazing group (n = 12) over a 4-d period for estimation of forage DMI and forage contribution to daily P intake twice during the grazing season. Analyzed pasture samples contained 3.28 mg of P/g of DM. During the second year, 72 Holstein steers (297 kg of BW) were blocked into 2 BW groups and subsequently assigned to 1 of 4 pasture groups. Steers rotationally grazed the same forage base as the first year for 126 d. Pasture samples contained 3.27 mg of P/g of DM. No significant differences (P > 0.10) were detected for BW, ADG, or free-choice supplemental mineral intake. Forage provided 126% of the recommended NRC P requirement. Thus, supplemental phosphorous was not required for Holstein steers grazing mixed, cool-season, grass/legume pastures.     

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 grass species on grazing steers: II. Dry matter intake and digesta kinetics

Animal responses to treatments in grazing experiments frequently remain unexplained because of inadequate pasture and(or) animal measurements. This 2-yr study examined DMI, gastrointestinal tract fill of undigested DM (FILL), rate of digesta passage (ROP), and digesta mean retention time (MRT) for steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.). A randomized complete block design was used with two agronomic replicates. Comparisons in June (yr 1) among continuously grazed switchgrass (SG), flaccidgrass (FG), and bermudagrass (BG) or in May (yr 2) among tall fescue (TF), SG, and FG showed similar digesta kinetics, but different DMI (kg.d-1.100 kg BW-1), among these forages within each sampling. In the June evaluation, the DMI of SG and FG were similar (means = 3.09), DMI of bermudagrass (BG) was lowest (2.23), and fecal DM output (FO) was similar among forages. In the May evaluation, DMI by steers grazing SG (3.90) was higher than that by steers grazing FG (2.97); DMI of tall fescue (TF) was intermediate (3.41) but similar to DMI of FG. Differences in DMI were due to differences in diet in vitro DM disappearance (IVDMD) rather than to differences in digesta kinetics. In July (yr 2), the MRT was highest for BG (84 h) and similar for SG and FG (57 h). Steers grazing different forages exhibited similar ROP and FILL, but FO (kg.d-1.100 kg BW-1) among steers varied (.37 for steers fed BG; .74 for steers fed SG and FG).(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of grain and monensin supplementation on ruminal fermentation, intake, digesta kinetics and incidence and severity of frothy bloat in steers grazing winter wheat pastures

Three 10-d collection periods (April 4 to 14, early April, EApr; April 23 to May 3, late April, LApr; May 10 to 20, 1984, mid-May, MMay) were conducted to evaluate effects of no supplement (C), .5 kg-head-1.d-1 (as-fed basis) supplemental grain (steam-flaked milo, G) or G plus 170 mg monensin.head-1.d-1 (M) on forage intake and digestion by 12 ruminally cannulated beef steers (four/treatment; avg initially BW = 393 kg) grazing irrigated winter wheat pasture. Ruminal pH was greater (P less than .01) for M than for C or G during EApr but was not altered by treatments in LApr or MMay. Compared with C, ruminal NH3 was decreased (P less than .10) by G and M (5 h after supplementation) in EApr, decreased (P less than .05) by G (2h) and increased (P less than .05) by M (8 h) in LApr and decreased (P less than .10) by G (-1h) in MMay. Treatments had little influence on total VFA concentrations or on molar proportions of acetate and propionate. Butyrate molar proportion was decreased (P less than .10) by M during EApr and LApr, but not during MMay. Monensin increased (P less than .05) fluid passage rate compared with C and G in EApr but not in other periods, Particulate passage measurements did not differ (P greater than .10) among treatments within periods. Forage DM intake was not influenced (P greater than .10) by supplementation during any period. Extent of in situ forage DM disappearance was greater (P less than .10) for M than for C or G during EApr (12 and 30 h of incubation) but was not different (P greater than .10) in LApr or MMay. Incidence of frothy bloat was decreased (P less than .05) by M during EApr; this reduction may have been related to effects of M on ruminal pH, forage digestion and fluid passage.     

Effects of prepartum energy intake on steroids during late gestation and on cow and calf performance

At 50 d prior to predicted calving, 37 multiparous Angus cows were grouped by sire of mating, age and weight of cow and placed on either a high energy (HE, n = 19) diet or a moderate energy (ME, n = 18) diet. Objectives were to determine the effect of prepartum nutrition on: prepartum serum concentrations of estrone (E1), estrone sulfate (E1SO4) and progesterone (P4); pre- and postpartum cow body weight changes; calf birth weight and cow and calf postpartum performance. The ME cows were group-fed Coastal bermudagrass hay ad libitum and dormant pasture; HE cows were group-fed 2.7 kg ground corn X head-1 X d-1 in addition to the ME treatment. Both groups were combined and fed identically after calving. Cows fed HE were heavier (P less than .01) than cows fed ME at d 10 prepartum and their calves were heavier (P less than .05) at birth and weaning than calves from cows fed ME. Serum E1 concentrations were not significantly different between groups, but serum E1SO4 was higher (P less than .01) at d 10 prepartum in ME cows compared with HE cows. Serum P4 concentrations of ME cows were higher (P less than .05) than those of HE cows. Cow body weights were greater (P less than .01) for the HE group than for the ME group during the first 6 mo postpartum. Cow rebreeding performance was identical for both groups.     

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)     

Effects of energy, mineral supplementation, or both, in combination with monensin on performance of steers grazing winter wheat pasture

A 2-yr study was conducted during the 2004 to 2005 (YR1) and 2005 to 2006 (YR2) winter wheat grazing seasons to determine the effects of supplementation strategies and delivery methods on supplement intake and growth performance of grazing steers (YR1, n = 253, initial BW 255 +/- 25 kg; YR2, n = 116, initial BW 287 +/- 14 kg). The 5 treatments were as follows: 1) negative control (NC), no supplemental nutrients; 2) free-choice, nonmedicated mineral (MIN); 3) free-choice, medicated mineral with 1,785 mg of monensin/kg of mineral mixture (RMIN); 4) RMIN and soybean hulls (SH-RMIN); and 5) a soybean hull-based energy supplement containing 165 mg of monensin/kg (GRNGOLD). Energy supplements were hand-fed on alternate days (average daily intake = 0.91 kg/steer). Inclusion of monensin in the free-choice mineral mixture decreased intake of the mineral mixture by 63% in YR1 and 55% in YR2 when no other supplement was offered. Consumption of RMIN provided from 129 to 161 mg of monensin/steer on average, whereas GRNGOLD provided 150 mg of monensin/d. Compared with NC, MIN did not affect ADG in YR1 (P = 0.38) but increased (P = 0.01) ADG by 0.22 kg/steer in YR2. Conversely, ADG of RMIN steers was greater (P = 0.03) than that of MIN steers during YR1 (0.72 vs. 0.55 kg/steer) but not different (P = 0.35) in YR2. Providing supplemental energy increased ADG by 0.13 kg/steer (0.85 vs. 0.72 +/- 0.053) in YR1 compared with RMIN, but no increase in ADG was observed in YR2. No difference (P > 0.24) was observed in ADG between SH-RMIN and GRNGOLD in either year. Conversion of the energy supplements (kg of as-fed supplement divided by kg of additional ADG) was excellent in YR1, resulting in 1 kg of BW gain for each 3.1 kg of supplement consumed. However, due to smaller increases in ADG with the energy and monensin supplements in YR2, supplement conversion for YR2 averaged 17.6. The absence of a difference (P > 0.24) in ADG between steers that received SH-RMIN and GRNGOLD suggests that the method of delivery (separate packages vs. a single package) for energy, monensin, and mineral supplementation is not important.     

Escape protein supplementation of yearling steers grazing smooth brome pastures

Two grazing trials utilizing individually supplemented yearling steers were conducted to study the effect of supplemental escape protein on steer performance during the active growth periods, spring and fall, of smooth brome (Bromus inermis). Graded levels (0, .11, .23 and .34 kg.head-1.d-1) of an equal-protein-basis mixture of bloodmeal and corn gluten meal were offered daily, replacing corn starch, which was used as the negative control. All steers received 582 g supplemental dry matter per day. Supplementation with escape protein improved daily performance in both spring (P less than .01) and fall (P less than .02). Analysis of pooled data from both trials indicated a linear (P less than .01) and quadratic (P less than .05) increase in steer performance with increasing level of escape protein in the diet. Analysis of grass samples collected throughout and composited over each trial demonstrated that grass protein was highly degraded in the rumen. Using a modified dacron bag technique, 12-h degradability was found to be 80 to 90% of the potentially digestible protein fraction. Rates of protein degradability were 14 and 11.7%/h. Assuming 5%/h rate of passage, escape protein was calculated to be 9.2 and 13.1% of total protein. As a result of the significant growth response observed above that of the energy-supplemented controls and the high ruminal protein degradabilities of the grass observed in the laboratory, it was concluded that growing ruminants grazing actively growing smooth brome pastures were deficient in metabolizable protein.     

Influence of supplementation method on forage use and grazing behavior by beef cattle grazing bluestem range.

Two 25-d trials (late summer and early winter) were conducted to determine the influence of supplementation method on forage use and grazing behavior. Fifteen ruminally and 12 esophageally fistulated steers (316 and 400 kg, respectively) were blocked by weight and assigned randomly to one of three treatments: 1) self-feeding supplement (via Calan gates) with salt as a limiting agent; 2) daily hand-feeding supplement plus salt; and 3) daily hand-feeding supplement without salt. Supplement intake was restricted to .95 kg.steer-1.d-1 with .23 and .40 kg of salt.steer-1.d-1 during summer and winter, respectively. Neither season nor supplementation method affected forage (1.64% of BW) or total (1.89% of BW) OM intake (P greater than .10). Total OM digestibility was greater (P less than .05) in the summer, in salt-supplemented steers, and when steers were self-fed supplement. Digestibility of NDF was greater (P less than .05) in the summer than in early winter, but did not differ among treatments (P greater than .10). Fluid dilution rate was greater (P less than .05) for salt-fed and self-fed steers during the summer but similar among treatments (P greater than .10) during the winter. Total VFA concentrations did not differ among treatments during summer, but were slightly greater (P = .07) in hand-fed steers during the winter. Steers fed supplements containing salt consistently displayed lower (P less than .01) acetate:propionate ratios, and self-fed steers had lower (P less than .01) acetate:propionate ratios during the summer. Ruminal ammonia concentrations did not differ (P greater than .10) among treatments and between periods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of lasalocid and monensin plus tylosin on comparative feeding value of steam-flaked versus dry-rolled corn in diets for feedlot cattle

Two trials were conducted to characterize the differences in utilization of dry-rolled and steam-flaked corn in a growing-finishing diet for feedlot cattle supplemented with and without ionophores. Ionophore treatments were: 1) no ionophore, 2) 33 mg/kg monensin sodium plus 11 mg/kg tylosin and 3) 33 mg/kg lasalocid sodium. In trial 1, treatment effects on feedlot performance were evaluated in a 239-d growing-finishing trial involving 180 crossbred steers (approximately 25% Brahman with the remainder represented by Hereford, Angus, Shorthorn and Charolais breeds in various proportions) with an average initial weight of 153 kg. In trial 2, treatment effects on characteristics of digestion were evaluated using six steers of similar breeding and background to those used in trial 1, with cannulas in the rumen and proximal duodenum. There were no interactions between corn processing and ionophore supplementation (P greater than .20). Average daily gain was not affected by steam-flaking as opposed to dry-rolling, however, feed intake was decreased 5.4% and feed conversion was improved 6.8% (P less than .01). Steam-flaking increased the estimated net energy value of the diet 7.7% and 8.5% for maintenance and gain, respectively (P less than .01). Steam-flaking increased the digestibility of starch 6.6% (P less than .01). Steam-flaking increased ruminal molar concentrations of propionate and decreased acetate:propionate ratio and estimated methane production (P less than .10). Both monensin-tylosin and lasalocid resulted in reduced feed intake (12.3 and 6.5%, respectively, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Implant and copper oxide needles for steers grazing Acremonium coenophialum-infected tall fescue pastures: effects on grazing and subsequent feedlot performance and serum constituents.

Two experiments were conducted to compare the effects of a progesterone-estradiol implant (PEI) with no implant (NI) and 20 g of copper oxide needles (CuON) with no CuON on grazing, subsequent feedlot performance, and selected serum constituents of steers. In Exp. 1, 114 Limousin crossbred yearling steers (317 kg average initial BW) were stocked continuously on Acremonium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)-ladino clover (Trifolium repens L.) pastures (C) or were rotated to bermuda grass (Cynodon dactylon [L.] Pers.) during summer months (R) of two consecutive years. Implant and copper treatments were applied within pasture. Blood samples were collected four times during each grazing season. Continuously stocked steers had greater (P less than .05) grazing gain, less (P less than .10) feedlot gain, and heavier (P less than .05) carcass weights than R steers did. Implanted steers had greater (P less than .05) pasture but lesser (P less than .05) feedlot gains than did NI steers. Prolactin concentrations were greater (P less than .05) from R than from C steers in late summer 1988. Ceruloplasmin was greater (P less than .01) with CuON than without on the last three and last two sampling dates in 1988 and 1989, respectively. In Exp. 2, blood samples were collected twice from 40 mixed-breed steers (283 kg average initial BW) receiving the same implant and copper treatments as in Exp. 1 and grazing infected fescue for one season. Serum ceruloplasmin and copper concentrations were increased (P less than .01) by CuON, but other measurements did not differ among treatments. Summer grazing of bermuda grass increased serum copper, ceruloplasmin, and prolactin but decreased grazing performance. Implanting increased grazing performance. Copper oxide needles increased serum ceruloplasmin and copper concentrations but did not affect steer performance.     

Effects of supplement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle

Two experiments were conducted to determine the effects of supplement type on the rate of gain by heifers grazing bermudagrass and on the intake, apparent total-tract OM digestibility, ruminal fermentation, digesta kinetics, in situ DM digestibility, and forage protein degradation by steers fed prairie hay. In Exp. 1, 45 heifers (284+/-24 kg) grazed a bermudagrass pasture for 91 d in the late summer to determine the effects of no supplement (CON), or one of four individually fed monensin-containing (150 mg/[heifer x d]) supplements (MINCS; 0.1 kg of mineral mix with 0.2 kg [DM] of cottonseed hulls as a carrier/[heifer x d]), a pelleted protein supplement (PROT; 1 kg of DM, 242 g of degradable intake protein [DIP]/[heifer x d]), or high-fiber (HF) and high-grain (HG) (2 kg of DM, 243 and 257 g of DIP, respectively/[heifer x d]) pelleted energy supplements. In Exp. 2, four ruminally cannulated steers (311+/-22 kg) with ad libitum access to low-quality (4% DIP, 73% NDF, 40% ADF) prairie hay were individually fed monensin-containing (200 mg/[steer x d]) treatments consisting of 1) mineral mix + corn (MINCR; 0.1 kg of mineral and 0.4 kg of cracked corn [DM] as a carrier, 19 g of DIP/[steer x d]), 2) PROT (1.4 kg of DM, 335 g of DIP/[steer x d]), 3) HF, or 4) HG (2.9 kg of DM, 340 and 360 g of DIP, respectively/[steer x d]) in a 4 x 4 Latin square with 14-d adaptation and 6-d sampling periods. In Exp. 1, the HF-, HG-, and PROT-supplemented heifers had greater (P < 0.01) rates of gain than CON heifers, and the HF- and HG-supplemented heifers tended (P < 0.11) to gain more weight than those fed PROT. In Exp. 2, steers fed PROT consumed more (P < 0.05) hay OM than HF and HG, or MINCR. Total OM intake was greater (P < 0.01) by supplemented steers than MINCR-fed cattle. Hay OM digestibility was not affected (P = 0.19) by treatment, but total diet OM digestibility was greater (P < 0.01) for HF- and HG- than for MINCR- or PROT-fed steers. The rate of in situ DM digestibility was greater (P < 0.01) for HF, HG, and PROT than for MINCR. Results from these studies indicate that feeding milo- vs fiber-based energy supplements formulated to provide adequate DIP did not result in different forage intake, OM digestibility, or in situ DM digestibility, whereas both increased ADG in heifers consuming low-quality forages compared with unsupplemented or mineral- or protein-supplemented cattle. An adequate DIP:TDN balance decreased the negative associative effects often observed when large quantities of high-starch supplements are fed with low-quality hay.     

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)