Effects of cottonseed meal supplementation time on ruminal fermentation and forage intake by Holstein steers fed fescue hay.

Four ruminally cannulated Holstein steers (average BW 303 kg) were used in a 4 x 4 Latin square design digestion trial to study the influence of daily cottonseed meal (CSM; 1.6 g of CP/kg of BW) supplementation time on forage intake and ruminal fluid kinetics and fermentation. Steers were housed individually in tie stalls and were fed chopped fescue hay on an ad libitum basis at 0600 and 1400. Treatments were 1) control, grass hay only (CON) and grass hay and CSM fed once daily at 2) 0600 (EAM) 3) 1000 (MAM), or 4) 1400 (PM). Ruminal NH3 N concentrations reflected a time of supplementation x sampling time interaction (P less than .05); CON steers had the lowest (P less than .05) ruminal NH3 N concentrations at all times other than at 0600, 1000, 1200, and 2400, when they did not differ (P greater than .05) from at least one of the supplemented groups. Forage intake, ratio of bacterial purine:N, rate of DM and NDF disappearance, and ruminal fluid kinetics were not influenced (P greater than .05) by supplementation time. Total ruminal VFA differed (P less than .05) between CON and supplemented steers, as well as among supplemented steers (linear and quadratic effects P less than .05). Acetate, propionate, and valerate proportions were influenced (P less than .05) by a sampling time X supplementation time interaction. Under the conditions of this study, greater peak ammonia concentrations with morning supplementation than with afternoon supplementation did not stimulate ruminal fermentation or rate of NDF disappearance.     

Effects of supplemental protein percentage and feeding level on intake, ruminal fermentation, and digesta passage in beef steers fed prairie hay.

Twelve ruminally cannulated steers (average initial BW 357 kg) were allotted to four treatments (three steers per treatment) in a replicated 4 x 4 Latin square design with 21-d periods (12 d for adaptation and 9 d for collection) to compare the effects of protein supplements that differed in percentage of CP and feeding level on low-quality forage utilization. Treatments were 1) control (C), ad libitum access to 5.6% CP prairie hay, 2) C +600 g of DM.steer-1.d-1 of a 43% CP supplement based on cottonseed meal (PS), 3) C + 1,200 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (GS), and 4) C + 600 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (LS). Ruminal total VFA concentrations were increased 8% (P less than .07) by PS vs GS 1 h after supplementation. Among supplemented steers, ruminal acetate (mol/100 mol) was decreased 1.2 mol/100 (P less than .03) by GS vs PS and LS; however, supplementation did not affect (P greater than .10) acetate proportions compared with C. Neither propionate nor butyrate was affected (P greater than .10) by supplementation, but among supplemented steers, butyrate proportions were 8% greater (P less than .03) for GS than for PS and 5% less (P less than .10) for LS than for the average of GS and PS. Ruminal pH did not differ (P greater than .10) among treatments. Ruminal ammonia concentrations were increased 1.4 to 4.8 mg/100 mL (P less than .07) by supplementation and typically were less for LS than for PS and GS at most sampling times. Prairie hay DMI (average = 16.3 g/kg BW) was not affected (P greater than .10) by supplementation. Fluid dilution rate was 8% faster (P less than .01) when steers were supplemented than when they were not fed supplement, and fluid dilution rate was increased 4% (P less than .04) by GS compared with PS. Particulate digesta passage rate was not affected (P greater than .10) by treatment, but total tract retention time was decreased (P less than .01) 10% by supplementation. Extent and rate of prairie hay NDF digestion in situ were not greatly affected by supplementation, but in situ disappearance of supplement N was 6 to 10 percentage units less (P less than .06) for GS than for PS and 2 to 6 percentage units less for LS than for the average of PS and GS supplements.(ABSTRACT TRUNCATED AT 400 WORDS)     

The delivery of cottonseed meal at three different time intervals to steers fed low-quality grass hay: effects on digestion and performance

A ruminal fermentation trial and a steer growth trial were conducted to evaluate the effects of time interval of cottonseed meal (CSM) supplementation of predominantly meadow fescue grass hay (GH; CP = 6.6%) on nutrient digestion and growth performance of beef steers. The fermentation trial used four ruminally cannulated steers assigned to a 4 x 4 latin square design with dietary treatments of GH fed alone (C) or GH supplemented with 3 g CP/kg BW.75 daily as supplied by CSM every 12, 24 or 48 h. Nylon bags containing GH were inserted into the rumen on d 1 and 2 of each collection period and incubated for 12, 24, 48 and 96 h to measure NDF and ADF degradation. Subsequently, steers were fed Yb-labeled GH and fecal samples were collected to determine particulate passage rate (PR). Dry matter and NDF intake, mean NDF and ADF in situ disappearance and ruminal VFA concentrations were greater (P less than .05) when CSM was fed; however, the delivery of CSM at various times did not affect (P greater than .10) these variables. Supplemented diets tended (P = .08) to have faster PR compared with the C diet. In the growth trial, CSM supplemented steers consumed more digestible DM (P less than .05) and had greater (P less than .05) daily gain compared with C steers. Effects due to time of CSM supplementation were not observed for the variables measured in the present study.     

Time of daily supplementation for steers grazing dormant intermediate wheatgrass pasture.

To compare the effects of time of daily protein supplementation on grazing behavior, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites, 12 ruminally cannulated Holstein steers (449 and 378 kg average initial and final BW, respectively) were allotted to three groups. Treatments consisted of CON = no supplement, AM = cottonseed meal (.25% of BW) at 0600, and PM = cottonseed meal (.25% of BW) at 1200. Steers grazed a dormant (1.1% N) intermediate wheatgrass (Thinopyrum intermedium Host) pasture. Sampling trials occurred in December, January, and February. Supplementation altered (P = .01) time spent grazing; CON steers grazed approximately 1.5 h longer than supplemented steers. Supplemented steers lost less (P = .02) BW (-40 kg) than CON steers (-75 kg) did. Supplementation did not alter (P greater than .15) forage OM intake; however, total OM intake was greater (P = .01) for supplemented steers (22.3 g/kg of BW) than for CON (18.4 g/kg of BW) steers. Supplementation did not affect (P greater than .15) digesta kinetics. Extent of in situ NDF (96 h) and rate (%/h) of disappearance for supplemented steers was greater (P = .01) than for CON steers. Across all periods, ruminal NH3 N and total VFA concentrations were lower (P = .01) for CON steers than for supplemented steers. Serum insulin (ng/mL) concentration was lower (P = .03) and concentration of serum growth hormone (ng/mL) was higher (P = .02) for CON steers than for supplemented steers. Cottonseed meal supplementation enhanced utilization of intermediate wheatgrass; however, supplementation time had minimal effects on the variables measured.     

Influence of protein type and level on nitrogen and forage use in cows consuming low-quality forage

Minimal quantities of ruminally degradable protein from supplements may improve supplement use efficiency of ruminants grazing dormant forages. In Exp. 1, N retention, ruminal NH(3), serum urea N, and NDF digestibility were evaluated for 12 ruminally cannulated cows (Bos spp.) in an incomplete Latin Square design with 3 periods of 42 d each. Cows were fed weeping lovegrass [Eragrostis curvula (Schrad.) Nees] hay (4.1% CP, 75% NDF, OM basis) at 1.3 % BW/d and offered 1 of 3 sources of CP [urea, cottonseed (Gossypium spp.) meal (CSM); or 50% blood meal and 50% feather meal combination (BFM)] fed to supply 0, 40, 80, or 160 g/d of CP. Beginning on d 22 of supplementation, ruminal contents and serum samples were collected at -2, 0, 3, 6, 9, 12, 18, 24, 30, 36, and 48 h relative to the morning offering of hay. On Day 24, feces and urine were collected for 72 h. In Exp. 2, 4 ruminally cannulated steers were used in a replicated 4 by 4 Latin Square to evaluate use of supplements differing in quantity and ruminal CP degradability. Steers were fed 6.8 kg/d chopped sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse] hay (3.7% CP, 74% NDF on OM basis) and supplemented with 56 g/d of a salt mineral mix (CON); CON + 28 g/d blood meal + 28 g/d feather meal (BFM); CON + 98 g/d CSM (LCS); or CON + 392 g/d CSM (HCS). Treatments provided 0, 40, 40, or 160 g/d of CP for CON, BFM, LCS, and HCS respectively. In Exp. 1, N use and total tract NDF digestibility were not affected by protein sources or amounts (P ≥ 0.18). Ruminal NH(3) concentrations exhibited a quadratic response over time for UREA (P < 0.05) and was greater with increasing inclusion of urea (P < 0.05); whereas BFM or CSM did not differ (P > 0.05) by amount or across time. In Exp. 2, supplementation had a tendency (P = 0.09) to increase DM disappearance. Supplementation also increased (P < 0.01) serum glucose concentrations; however, no difference (P ≥ 0.28) was found between supplements. Serum urea N and ruminal NH(3) concentrations were increased (P ≤ 0.01) in steers fed HCS. Feeding low quantities of a high-RUP supplement maintained rumen function without negatively affecting DM or NDF digestibility of a low-quality forage diet.     

Feed intake and digestion by beef steers consuming and receiving ruminal insertions of prairie hay differing in level and particle size

A 5 X 5 Latin square design involving five cannulated beef steers (342 and 358 kg avg initial and final body weights, respectively) fed prairie hay (76.7% neutral detergent fiber, 5.7% acid detergent lignin and .85% N) was conducted to evaluate effects on feed intake and nutrient digestion of variations in physical characteristics of ruminal digesta achieved by ruminal insertion of different amounts of prairie hay differing in particle size. Steers were fed hay ad libitum in two equal meals (0800 and 2000). At 1200, four of the steers received manual, ruminal insertions of ground hay. Fine hay (F) was ground through a screen with 2-mm openings (.39 mm mean particle size), whereas coarse hay (C) was ground through a screen with 2.54-cm openings (4.46 mm mean particle size). Amounts of hay inserted were .2 (low, L) or .4% (high, H of initial body weight of individual steers. Ruminal hay insertions comprised 18% of total dry matter (DM) intake for L and 34 and 37% for HF and HC, respectively. Fed hay consumption decreased (P less than .05) with hay insertion and was lower for H than L; total DM intake was not influenced by treatment (P greater than .10). Ruminal NH3-N concentrations and ruminal organic matter digestion was greater (P less than .05) with ruminal hay insertion than without and with H than with L (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pretanned leather shavings in a supplement mixture for steers: I. In situ and in vitro disappearance, ruminal fermentation, and organic matter, nitrogen, and fiber digestion

Two digestion studies were conducted to evaluate the use of pretanned leather shavings as a component of a protein supplement. In Exp. 1, the in situ and in vitro disappearance of pretanned leather shavings and soybean meal was evaluated. Results revealed that less than 18.4% of the pretanned leather shavings was solubilized and disappeared when exposed to McDougall's buffer for 48 h, but there was 90.0% disappearance with 48-h exposure to a .1 N HCl/pepsin treatment and 97.0% disappearance with exposure to a two-stage digestion. In situ disappearance following 72 h in the rumen allowed 6.8% disappearance. Thus, leather shavings seem to be relatively indigestible in the rumen, but postruminal digestion may be possible. In Exp. 2, six Angus x Holstein steers, fitted with ruminal and duodenal cannulas, were used in a replicated 3 x 3 Latin square to evaluate ruminal and digestion effects of the following supplements combined with fescue hay at 1.7% of BW (DM basis): no supplementation (control); supplementation intraruminally with soybean meal at .07% of BW (as-fed basis); and supplementation intraruminally with a combination of soybean meal and pretanned leather shavings (17:8 ratio) at .05% of BW (isonitrogenous to soybean meal; as-fed basis). Ruminal fluid passage rate was greater and fluid turnover time was shorter in steers fed leather shavings than in those fed soybean meal (P = .10). Ruminal pH was lower (P = .04) for supplemented steers than for control steers and ruminal NH3 N concentration was greater (P = .01) in steers fed soybean meal than in those fed leather shavings. Total VFA concentration was increased (P = .02) by supplementation. Supplementation with soybean meal increased (P < .05) ruminal molar proportions of butyrate, valerate, and isovalerate compared with leather shavings. Duodenal OM flow and OM disappearing in the intestines were increased by supplementation (P < .10), but not by the type of supplement fed (P > .10). Ruminal digestion of OM and total tract OM digestion were unaffected (P > .10) by supplementation and the type of supplement fed. Flow and digestion of NDF were unaffected (P > .10) by the treatments. Flow of N and the quantity of N disappearing in the intestines were increased (P < .05) by supplementation but did not differ (P > .10) between supplementation groups. Microbial N flow, N utilization for net microbial protein synthesis, and ruminal N disappearance were unaffected (P > .10) by supplementation and the type of supplement provided. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on digestion or fermentation and to allow for escape of some N to the lower tract.     

Feed intake and digestion by beef cows fed prairie hay with different levels of soybean meal and receiving post-ruminal administration of antibiotics

Six cannulated beef cows (one Angus, two Hereford and three Angus x Hereford; 405 kg) were used in a 6 x 6 latin square experiment with a 2 x 3 factorial arrangement of treatments. Prairie hay (.77% N, 73% neutral detergent fiber [NDF] and 7% acid detergent lignin) was fed ad libitum from d 1 through 14 and at 90% of ad libitum intake from d 15 through 21 during digesta collection. Periods lasted 21 d. Soybean meal (SBM) was offered at 0 (control, C), .12 (low, L) or .24% of body weight (high, H; dry matter basis). Cows received daily doses of an antibiotic mixture (1 g neomycin and .125 g bacitracin) or saline in the duodenum. Prairie hay dry matter (DM) intake increased (P less than .05) linearly with SBM supplementation, being 25 and 40% greater for L and H than for C, respectively. Ruminal fluid concentrations of NH3-N and total volatile fatty acids increased (P less than .05) linearly as SBM was added to the diet. Ruminal fluid dilution rate increased linearly and particulate passage rate increased (P less than .05) quadratically with increasing SBM. True ruminal digestibilities of organic matter, NDF and N increased (P less than .10) quadratically with increasing SBM (organic matter; 50.3, 57.9 and 58.3%; NDF: 54.7, 60.4 and 59.8%; N: 17.5, 45.1 and 51.4% for C, L and H, respectively). Main effects of antibiotic administration were not significant. Increases in DM intake when SBM was given were large compared with the small elevations in ruminal digestion, implying that metabolic regulation was modifying intake of low-quality forage.     

Source and level of energy supplementation for yearling cattle fed ammoniated hay

Brahman x British crossbred steers were used in growth and digestion trials to evaluate the response of source (corn, sugar cane molasses, or soybean hulls) and feeding rate (0, 1.4, or 2.8 kg DM per steer daily in the growth trials; 0, 15, or 30% of the ration DM in the digestion trial) of energy supplementation in cattle fed ammoniated (4% of forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Cattle on all treatments were fed 0.5 kg cottonseed meal daily. In the growth trials, steers grazed dormant bahiagrass (Paspalum notatum) pasture. Increasing the levels of supplementation decreased hay intake but increased total dietary intake for all diets (P < 0.07). Daily gain and feed efficiency of steers were improved (P < 0.03) with supplementation. Steers supplemented with corn or soybean hulls at 2.8 kg DM/d had a higher ADG (0.92 kg) and gain/feed (0.103) than steers supplemented with molasses (0.78 kg, 0.08, respectively) at the same level. Seven crossbred steers (200 kg) were used in a five-period digestion trial to evaluate apparent OM, NDF, ADF, and hemicellulose digestibility. Apparent OM digestibility of all diets increased linearly (P = 0.02) as the level of supplementation increased. Apparent NDF and ADF digestibility decreased (P < 0.03) as the level of supplementation with corn or molasses increased, whereas increasing the level of soybean hulls in the diet increased (P < 0.06) apparent NDF and ADF digestibility. Four ruminally fistulated crossbred steers (472 kg) were used in a 4 x 4 latin square design to investigate ruminal characteristics with energy supplementation at 30% of ration DM. Ruminal pH in steers supplemented with soybean hulls or corn declined after feeding. Ruminal pH decreased more rapidly with corn supplementation and remained below 6.2 for a longer period of time than with the other diets. Ruminal pH did not change within 24 h after feeding for steers fed the control or molasses diets. No change in total VFA concentration was observed in steers fed molasses or corn. Total ruminal VFA concentration in steers supplemented with soybean hulls increased initially after feeding and then declined within 24 h after feeding. Soybean hulls produced fewer negative associative effects than corn when fed with ammoniated stargrass hay at 2.8 kg DM/d. The reduced gain/feed of steers supplemented with molasses compared to soybean hulls or corn indicates that molasses was not utilized as efficiently as the other energy sources.     

Pretanned leather shavings in a supplement mixture for steers: II. Digesta kinetics, ruminal fermentation, and grazing behavior in steers grazing dormant wheatgrass pasture

Twelve ruminally cannulated steers (Angus x Holstein; average initial BW = 533 +/- 3.28 kg) were randomly allotted to one of three treatments (four steers/treatment) to evaluate the use of pretanned leather shavings as a component of a protein supplement for steers grazing dormant intermediate wheatgrass (Thinopyrum intermedium Host). Steers were allotted to one of three treatments: 1) no supplement (control); 2) supplementation intraruminally at 0700 with soybean meal at .2% of BW (as-fed basis); 3) supplementation intraruminally with soybean meal and pretanned leather shavings (17:8 ratio, respectively) at .16% of BW (as-fed basis). Supplements were formulated so that intakes were isonitrogenous and were placed intraruminally once daily (0700). Sampling periods were conducted February 3 to 16 and February 17 to March 5, 1995. In situ organic matter disappearance of the soybean meal supplement was greater (P > .05) than that of the leather shavings supplement at all incubation times (1, 3, 6, 9, 12, 24, and 48 h). Data suggested that pretanned leather shavings within the leather shavings supplement were only 25% degradable within the rumen. Forage OM intake (control = 12.7, soybean meal = 12.7, and leather shavings = 13.4 g/kg of BW), grazing time, and grazing efficiency were not altered (P > .10) by supplementation or type of supplement provided but did increase between the February and March samplings. Total intake was increased (P = .09) with supplementation and reflected the addition of the protein supplements. Particulate and fluid passage estimates were unaffected (P > .10) by the supplements; however, gastrointestinal fill increased (P = .01) between the February and March samplings. Ruminal pH was lower (P = .04) and ruminal NH3 N concentration was greater (P = .02) for supplemented steers than for control steers, and supplementation treatments did not differ (P > .10). Total VFA concentrations were increased (P = .01) by supplementation but were not affected by type of supplement provided (P > .10). Ruminal molar proportions of acetate and propionate and the ratio of these two VFA did not differ (P > .10) between supplementation types. Nonetheless, supplementation increased molar proportions of butyrate (P = .04), valerate (P = .02), and isovalerate (P = .05), and leather shavings supplementation increased (P = .10) isobutyrate proportions over those in steers supplemented with soybean meal. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on forage intake, digesta passage, grazing behavior, or ruminal fermentation and seemed to provide effects similar to those of soybean meal alone.     

Effects of supplementation frequency on ruminal fermentation and digestion by steers fed medium-quality hay and supplemented with a soybean hull and corn gluten feed blend

Reducing the frequency of supplementation to beef cattle would reduce labor and vehicle maintenance costs and could have the potential to increase profits if performance is not negatively affected. Six ruminally cannulated beef steers (362 ± 18 kg of BW) were used in a replicated 3 × 3 Latin square design to determine the effect of supplementation frequency (daily or on alternate days) on digestion and ruminal parameters when feeding medium-quality hay and supplementing with a mixture of soybean hulls and corn gluten feed. Dietary treatments consisted of ad libitum fescue hay (8.8% CP and 34.8% ADF) that was supplemented at 1% of BW daily (SD), supplemented at 2% of BW on alternate days (SA), or not supplemented (NS). The supplement (14.6% CP and 29.8% ADF) contained 47% soybean hull pellets, 47% corn gluten feed pellets, 2% feed grade limestone, and 4% molasses (as fed). Each period consisted of a 12-d adaptation phase followed by 6 d of total fecal, urine, and ort collection. All supplement offered was consumed within 2 h. Ruminal fluid was collected every 4 h for 2 d. Hay intake was reduced (P < 0.01) for SD and further reduced (P < 0.01) for SA. Hay intake was 1.54, 1.19, and 1.02% of BW (SEM ± 0.036) for NS, SD, and SA, respectively. There was a treatment (P < 0.01) × day interaction for mean ruminal pH. On the day of supplementation, ruminal pH for SA (6.13) was lower (P < 0.01) than those for both SD (6.29) and NS (6.52). However, on the day the SA treatment did not receive supplement, ruminal pH of SA (6.53) did not differ (P = 0.87) from ruminal pH of NS and was greater (P < 0.01) than that of SD. Ruminal pH of SD was lower (P < 0.01) than that of NS. Diet DM digestibility was increased (P < 0.01) by supplementation but did not differ (P = 0.58) because of frequency. Dry matter digestibility was 57.9, 64.1, and 64.6% (SEM ± 0.65) for NS, SD, and SA, respectively. The amount of N retained did not differ (P = 0.47) because of frequency (24.9 ± 5.61 and 22.0 ± 5.50 g/d for SD and SA, respectively) and was greater (P < 0.01) for the supplemented treatments than for NS (4.2 ± 3.30 g/d). When supplementing a blend of soybean hulls and corn gluten feed, producers can reduce the frequency of supplementation to every other day without reducing digestibility or N retention.     

Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows

Laboratory, digestion and growth studies were used to evaluate energy and protein supplements for ammoniated (4% of the forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Ammoniation increased (P less than .05) total N concentration (.7 to .9% vs 1.7 to 2.0%) and in vitro digestion of OM, NDF and ADF and reduced (P less than .05) NDF concentration of stargrass hay. Two digestion (3 x 3 Latin square, 250-kg steers) and two growth (400-kg Brahman crossbred cull cows, eight head per pasture, two pastures per treatment, November through February) trials evaluated citrus pulp or liquid cane molasses (Trial 1) and molasses or molasses plus cottonseed meal (Trial 2) supplementation of ammoniated hay. Supplementation with byproduct energy sources, citrus pulp or molasses (either alone or with cottonseed meal), improved (P less than .05) OM digestibility but reduced (P less than .05) NDF and ADF digestibilities. Apparent nutrient digestibilities were similar (P greater than .05) between diets supplemented with citrus pulp and molasses and between diets supplemented with molasses and molasses plus cottonseed meal. In Trial 1, ADG by cull cows was greater (P less than .05) for citrus pulp- (.71 kg) or molasses-(.68 kg) supplemented diets than for hay fed alone (.49 kg). In Trial ADG was greater (P less than .05) for cull cows fed ammoniated hay supplemented with molasses plus cottonseed meal (.85 kg) than for those supplemented with molasses only (.69 kg). Feeding cows over the winter increased their (P less than .05) carcass weight, marbling score, USDA quality grade and lipid percentage of the 9-10-11 rib section compared with cows slaughtered at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of base ingredient in cooked molasses blocks on intake and digestion of prairie hay by beef steers

Twelve steers (332 kg) were used in three simultaneous 4 x 3 incomplete Latin squares to evaluate effects of beet molasses (BEET), cane molasses (CANE), or concentrated separator by-product (CSB) as base ingredients in cooked molasses blocks on intake and digestion of prairie hay and ruminal characteristics. All steers had ad libitum access to prairie hay (5.9% CP and 69.4% NDF; DM basis). The four experimental treatments included a control (no supplement) and three cooked molasses blocks, based on BEET, CANE, or CSB, fed daily at .125% of BW (.42 kg/d as-fed, .13 kg/d CP). Forage OM, NDF, and N intakes; digestible OM, NDF, and N intakes; and total tract OM and N digestibilities (percentage of intake) were greater (P < .05) for steers fed cooked molasses blocks than for control steers. Total tract OM digestibility was greater (P < or = .06) for steers fed BEET blocks (54.0%) than for those fed CSB (52.1%) or CANE blocks (52.2%). Digestion of NDF was greatest (P < .05) for steers fed BEET blocks (51.9%) and tended to be greater (P < .07) for steers fed CANE (49.3%) or CSB blocks (49.3%) than for control steers (46.9%). Ruminal ammonia concentrations were greater (P < .05) for steers fed cooked molasses blocks (.89 mM) than for control steers (.21 mM); this was primarily due to increases to 4.6 mM at 2 h postfeeding for steers fed blocks. Concentrations of total VFA in ruminal fluid were greater (P < .05) for steers fed BEET (92.7 mM) and CSB (88.1 mM) blocks than for control steers (80.3 mM), whereas concentrations for steers fed CANE blocks were intermediate (85.4 mM). Steers supplemented with cooked molasses blocks had greater molar percentages of butyrate than did control steers, particularly shortly after feeding. In summary, supplementation with cooked molasses blocks increased forage intake and digestion. The three base ingredients elicited similar responses, although steers fed BEET had slightly greater OM and NDF digestibilities than those fed CANE or CSB.     

Effects of ammoniation of tall fescue on phenolic composition, feed intake, site and extent of nutrient digestion and ruminal dilution rates of steers

Tall fescue hay (H) supplemented with corn and urea (HU) or corn gluten meal (HCGM) and ammoniated tall fescue hay supplemented with corn (AH) or corn gluten meal (AHCGM) were fed to steers in two 4 X 4 Latin-square trials. Diets were fed to four Angus-Hereford steers (550 kg) at equal intakes in trial 1 and to four Hereford steers (350 kg) at ad libitum intakes in trial 2. Ammoniation reduced cell wall concentrations of p-coumaric acid and ferulic acid by 48 and 67%, respectively. Concentrations of other phenolics were also reduced. Apparent total tract digestibilities of vanillin, p-coumaric acid and ferulic acid were lower (P less than .05, .001 and .01, respectively) when nontreated hay was fed in trial 1, but were not different between hay types in trial 2. In trial 1, greater negative intestinal digestibilities of p-coumaric acid (P less than .001) and vanillin (P less than .05) occurred for steers fed HU and HCGM vs AH and AHCGM diets. Digestibilities of neutral detergent fiber (NDF) and acid detergent fiber (ADF) were greater (P less than .001) for steers fed ammoniated hay diets in both trials and greater (P less than .05) for HCGM vs HU in trial 1. More than 96% of the NDF and ADF digested by steers in trial 1 was digested in the stomach. Intakes of digestible NDF and ADF, but not indigestible NDF or ADF, were higher (P less than .001) for steers fed AH and AHCGM in trial 2. In situ dry matter disappearance rate of ammoniated hay was greater (P less than .05) than that of nontreated hay, but rate of cotton thread disappearance from bags suspended in the rumen of steers fed the various diets was similar among treatments. In both trials, feeding ammoniated hay resulted in higher (P less than .05) ruminal concentrations of acetate and higher (P less than 0.05) acetate:propionate ratios. Ruminal liquid dilution rates were lower (P less than .05) for steers fed AH and AHCGM in trial 1, but were not different in trial 2. Ruminal dry matter concentration and solids dilution rate were not affected by diet in either trial. The results are interpreted to indicate that increased intake of ammoniated hay is a result of increased rate and extent of fiber digestion.     

Characteristics of water soluble markers for measuring rumen liquid volume and dilution rate

The utility of five water soluble markers (WSM) for measuring rumen liquid volume and dilution rate was examined in nine in vitro and in vivo experiments. The WSM tested included polyethylene glycol (PEG) and ethylenediaminetetraacetic acid (EDTA) complexes of Cr, Co, Fe and Yb. Feedstuffs incubated in vitro absorbed variable amounts of distilled H2O and autoclaved rumen fluid with roughages imbibing greater (P less than .05) amounts of fluid than feeds higher in starch. Liquid present in the feeds tested reached equilibrium with added WSM in about 20 min. Corn grain in the whole or ground form appeared to exclude 4 to 16% of the WSM while imbibing water. Cottonseed hulls reduced detectable PEG due to some water soluble substance present. The WSM tested did not produce different estimates of dilution rate (P = .65) and volume (p = .29) of steers fed either 80% whole shelled corn, 90% chopped alfalfa hay or 90% prairie hay diets. Ruminal liquid measured by hand removal was about 4% greater than volume estimated by WSM. The percentage of total ruminal water associated with solids varied from 27 to 86% among steers. Compared with steers fed an 80% whole shelled corn diet, steers fed equal dry matter from alfalfa hay had 15% more dry matter in the rumen, 21% larger liquid volume, 80% greater ruminal liquid dilution rate and 116% greater rate of liquid flow from the rumen. Dilution rate of ruminal liquid during feeding was examined with six steers fed a 90% chopped alfalfa hay diet once daily at 1.8% of body weight. Dilution rate estimated with Co EDTA increased by 166% during the 4 h after feeding. The WSM did not influence (P greater than .10) digestibility of dry matter with steers fed a 90% roughage or a 90% concentrate ration. Recovery of WSM administered via a rumen cannula ranged from 96.8 to 99.7% in feces and 1.2 to 3.4% in urine. All WSM examined appeared suitable for estimating rumen liquid volume and dilution rate for diets not containing cottonseed hulls.     

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)     

Influence of supplemental four- and five-carbon volatile fatty acids on forage intake and utilization by steers

Four ruminally and duodenally cannulated crossbred steers (avg wt 282 kg; trial 1) and 12 intact Hereford steers (avg wt 336 kg; trial 2) were used to evaluate the effects of supplemental four- and five-carbon volatile fatty acids (SFA) on intake and digestion of low-quality prairie grass hay (PH). Steers were fed PH at 1.8% body weight (trial 1) or free choice (trial 2) together with a 34% protein, urea-cottonseed meal supplement (365 g/d trial 1; 500 g/d trial 2) plus 0 or 30 g/d of SFA (Ca-salts of isoC4, C5, and isoC5 acids). Ruminal pH, ammonia-N and total volatile fatty acid concentrations were not influenced (P greater than .10) by SFA. Addition of SFA increased the molar proportions of isobutyric (.84 vs .11; P less than .05), isovaleric (1.01 vs .32; P less than .01), and valeric (.66 vs .47; P less than .07) acids but did not significantly alter the proportions of other acids. Apparent total tract organic matter digestion (51.9 vs 53.7%; P = .095) tended to decrease with SFA, while ruminal and total tract digestion of acid detergent fiber and N were not affected by SFA. Microbial N (MN) flow to the duodenum and efficiency of microbial crude protein (MCP) synthesis were similar for both treatments (66.7 vs 57.4 g MN/d and 29.8 vs 24.4 g MCP/100 g apparently fermented organic matter, respectively). In trial 2, total tract dry matter and acid detergent fiber digestion and voluntary intake were similar for both diets. Results suggest that intake and utilization of prairie hay was not limited by a ruminal deficiency of SFA.     

Effects of protein supplementation to steers consuming low-quality forages on greenhouse gas emissions

Providing supplements that enhance the efficiency of feed utilization can reduce methane (CH₄) emissions from ruminants. Protein supplementation is widely used to increase intake and digestion of low-quality forages, yet little is known about its impact on CH₄ emissions. British-cross steers (n = 23; initial body weight [BW] = 344 ± 33.9 kg) were used in a three-period crossover design to evaluate the effect of protein supplementation to beef cattle consuming low-quality forage on ruminal CH₄, metabolic carbon dioxide (CO₂) emissions, forage intake, and ruminal fermentation. Steers individually had ad libitum access to low-quality bluestem hay (4.6% crude protein [CP]) and were provided supplemental protein based on (dry matter basis): cottonseed meal (CSM; 0.29% of BW daily; 391 g/d CP), dried distillers grains with solubles (DDGS; 0.41% of BW daily 563 g/d CP), or none (CON). Urea was added to DDGS to match rumen degradable protein provided by CSM. Ruminal CH₄ and metabolic CO₂ fluxes were obtained 2.4 ± 0.4 times per steer daily using an automated open-circuit gas quantification system (GreenFeed emission monitoring system; C-Lock Inc., Rapid City, SD). Forage intake increased (P < 0.01) with protein supplementation; however, no difference in forage intake (P = 0.14) was observed between CSM and DDGS treatments. Flux of CO₂ (g/d) was greater (P < 0.01) for steers fed CSM and DDGS than for steers fed CON. Steers supplemented with CSM had greater (P < 0.01) CH₄ emissions (211 g/d) than DDGS (197 g/d) both of which were greater (P < 0.01) than CON (175 g/d). Methane emissions as a proportion of gross energy intake (GEI) were lowest (P < 0.01) for DDGS (7.66%), intermediate for CSM (8.46%) steers, and greatest for CON (10.53%). Steers fed DDGS also had the lowest (P < 0.01) ruminal acetate:propionate ratio (3.60), whereas CSM (4.89) was intermediate, and CON (5.64) steers were greatest. This study suggests that the common practice of supplementing protein to cattle consuming low-quality forage decreases greenhouse gas emissions per unit of GEI.     

Utilization of magnesium and other macrominerals in sheep supplemented with different readily-fermentable carbohydrates

Sheep were used to determine the effects of dietary supplementation with readily-fermentable carbohydrates on Mg, Ca, K and P utilization. In each of two metabolism trials, 15 mature, crossbred wethers (average weight, 49.2 kg) were allotted to five dietary treatments consisting of 800 g/d of orchardgrass (Dactylis glomerata, L.) hay alone, or supplemented with 450 g/d of either glucose, sucrose, lactose or starch. Each trial consisted of a 5-d adjustment period, a 10-d preliminary period and a 10-d collection period. Compared with wethers fed hay alone, supplementation with each kind of carbohydrate to the diet decreased (P less than .05) fecal Mg excretion and increased (P less than .05) apparent absorption and retention of Mg. Apparent absorption of the Ca was lower (P less than .05) in wethers fed lactose and tended to be decreased by glucose, sucrose and starch supplementation. Calcium retention was lower (P less than .05) in wethers fed sucrose and lactose, compared with those fed hay alone. All types of supplementary carbohydrates depressed (P less than .05) apparent absorption and urinary excretion of K. Serum Mg and Ca were not affected and serum K was depressed (P less than .05) by carbohydrate supplementation. Ruminal fluid pH was decreased (P less than .05) by glucose and lactose supplementation, and addition of these carbohydrates tended to decrease molar proportions of acetate and increase those of propionate and butyrate, compared with sheep fed hay alone. Sucrose addition decreased (P less than .05) acetate and increased (P less than .05) butyrate molar proportions in the ruminal fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of supplemental zinc and manganese on ruminal fermentation, forage intake, and digestion by cattle fed prairie hay and urea

One in vitro and one in vivo metabolism experiment were conducted to examine the effects of supplemental Zn on ruminal parameters, digestion, and DMI by heifers fed low-quality prairie hay supplemented with urea. In Exp. 1, prairie hay was incubated in vitro for 24 h with five different concentrations of supplemental Zn (0, 5, 10, 15, and 20 ppm) and two concentrations of supplemental Mn (0 and 100 ppm), both provided as chloride salts. Added Mn increased (P < 0.02) IVDMD, but added Zn linearly decreased (P < 0.03) IVDMD. Added Zn tended to increase the amount of residual urea linearly (P < 0.06) at 120 min and quadratically (P < 0.02) at 180 min of incubation, although added Mn counteracted these effects of added Zn. Six 363-kg heifers in two simultaneous 3 x 3 Latin squares were fed prairie hay and dosed once daily via ruminal cannulas with urea (45 or 90 g/d) and with Zn chloride to provide the equivalent of an additional 30 (the dietary requirement), 250, or 470 ppm of dietary Zn. After a 7-d adaptation period, ruminal contents were sampled 2, 4, 6, 12, 18, 21, and 24 h after the supplement was dosed. Supplemental Zn did not alter prairie hay DMI (mean = 4.9 kg/d) or digestibility, although 470 ppm added Zn tended to decrease (P < 0.06) intake of digestible DM, primarily due to a trend for reduced digestibility with 470 ppm supplemental Zn. Zinc x time interactions were detected for both pH (P = 0.06) and NH3 (P = 0.06). At 2 h after dosing, ruminal pH and ruminal ammonia were linearly decreased (P < 0.05; P < 0.01) by added Zn. At 5 h after feeding, ruminal pH was linearly increased (P < 0.05) by added Zn, suggesting that added Zn delayed ammonia release from urea. The molar proportion of propionate in ruminal fluid was linearly and quadratically increased (P < 0.02; P < 0.01) whereas the acetate:propionate ratio was linearly and quadratically decreased (P = 0.02; P < 0.05) by added Zn. Through retarding ammonia release from urea and increasing the proportion of propionate in ruminal VFA, Zn supplementation at a concentration of 250 ppm may decrease the likelihood of urea toxicity and increase energetic efficiency of ruminal fermentation.