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PubMed1991

Effects of urea and sodium bicarbonate supplementation of a high-fiber diet on nutrient digestion and ruminal characteristics of defaunated sheep.

Five sheep (average BW 48 kg) with ruminal, duodenal, and ileal cannulas were fed 63% roughage: 37% concentrate diets (CP = 14.5%) in a 5 x 5 Latin square design to study effects of urea and sodium bicarbonate supplementation on nutrient digestion and ruminal characteristics of defaunated sheep. Diets were fed twice daily (DMI = 1,076 g/d). Defaunation was accomplished with 25-ml doses of alkanate 3SL3/sheep daily for 3 d. Control sheep were faunated (Treatment 1) and fed soybean meal as the major N supplement. Remaining sheep were maintained defaunated and fed either the same diet as Treatment 1 (Treatment 2), Treatment 1 with urea replacing 30% of the soybean meal N (Treatment 3), or Treatment 1 with 2% sodium bicarbonate in the diet (Treatment 4). Treatment 5 was a combination of Treatments 3 and 4. Compared with the faunated control, defaunation decreased (P less than .05) total tract DM, OM, NDF, ADF, and CP digestibilities (71.5 vs 69.4, 73.8 vs 71.7, 64.6 vs 61.4, 58.7 vs 55.8, and 74.2 vs 70.6%, respectively) and average (2 to 12 h postfeeding) ruminal fluid ammonia (23.5 vs 13.7 mg/dl) and isobutyrate (.9 vs .7 mM) concentrations. However, defaunation increased (P less than .05) linoleic and linolenic acid flows (.58 vs .45 g C18:2/d; .17 vs .14 g C18:3/d) to and disappearance (.50 vs .39 g C18:2/d; .14 vs .11 g C18:3/d) from the small intestine. Urea supplementation increased (P less than .05) total tract DM (70.2 vs 68.6%) and OM (72.3 vs 71.0%) digestibilities of defaunated sheep but lowered (P less than .05) ruminal fluid isobutyrate concentration (.6 vs .8 mM). Sodium bicarbonate supplementation increased (P less than .05) ruminal fluid pH (6.4 vs 6.2), isobutyrate concentration (.75 vs .60 mM), total tract ADF digestibility (57.6 vs 54.2%), and ruminal NDF (41.6 vs 28.5%), ADF (36.6 vs 22.8%), and CP (-5.5 vs -26.8%) digestibilities in defaunated sheep. Dietary supplementation of urea or sodium bicarbonate increased nutrient digestion by defaunated sheep.

Absorption↗
PubMed1991

Effects of dietary energy level and protein source on nutrient digestion and ruminal nitrogen metabolism in steers.

Four Simmental steers with ruminal, duodenal, and ileal cannulas were used to examine effects of dietary forage: concentrate ratio and supply of ruminally degradable true protein on site of nutrient digestion and net ruminal microbial protein synthesis. Steers (345 kg) were fed ammoniated corn cob (high forage; HF)- or corn cob/ground corn/cornstarch (low forage; LF)-based diets supplemented with soybean meal (SBM) or a combination of corn gluten meal and blood meal (CB). Diets were fed at 2-h intervals with average DM intake equal to 2.2% of BW. Feeding LF vs HF increased (P less than .05) OM digestion (percentage of intake) in the stomach, small intestine, and total tract. Efficiency of microbial CP synthesis (EMCP; g of N/kg of OM truly fermented) decreased (P less than .05) for LF vs HF (24.1 vs 26.8), but microbial N and total N flows to the small intestine were similar (P greater than .05) between energy levels (average 112 and 209 g/d, respectively). Total N flows to the small intestine were 13.1% greater (P less than .05) for CB than for SBM because of increased (P less than .05) passage of nonmicrobial N. Feeding SBM vs CB increased (P less than .05) EMCP (27.3 vs 23.3) and microbial N flow to the small intestine (127.5 vs 112.5 g/d), but these increases were not likely due to increased ruminal concentrations of ammonia N (NH3 N). Decreased (P less than .05) incorporation of NH3 N into bacterial N and slower turnover rates of ruminal NH3 N for SBM vs CB suggest that direct incorporation of preformed diet components into cell mass increased when SBM was fed. Results of this study suggest that the inclusion of ruminally degradable protein in the diet may increase the supply of products from proteolysis and that this can increase EMCP and microbial protein flow to the small intestine.

Amino Acids↗
PubMed1993

Supplementation of growing cattle grazing warm-season grass with proteins of various ruminal degradabilities.

This study was conducted to determine in situ ruminal protein degradation and animal responses to ruminally degraded and escape protein supplementation of warm-season grass. Cattle grazed a mixed stand of primarily big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) with some indiangrass (Sorghastrum nutans [L.] Nash) from the 1st wk of June to the 3rd wk of August. In 1987, 72 yearling steers (286 kg) were allotted randomly to three treatments: energy control (cornstarch-molasses mixture) or energy control plus .1 or .2 kg.animal-1.d-1 of escape protein. The total amount of a supplement fed per day was 1 kg. In 1988, 90 yearling heifers (240 kg) were allotted to five treatments: negative control (no supplement), energy control, energy control plus .14 kg.animal-1.d-1 of escape protein, energy control plus .18 kg.animal-1.d-1 of ruminally degraded protein, or .36 kg.animal-1.d-1 of protein supplied by a combination of the two protein sources. The total amount of a supplement fed per day was 1.7 kg. During 1987, the .2-kg level of escape protein produced the greatest gains (P < .10). In 1988, gains did not differ between the control and escape protein treatments. Ruminally degraded protein tended (P = .12) to increase gains (.09 kg/d) compared with the energy control. The combination treatment supported .13 kg/d more ADG (P < .10) than the negative and energy controls and the escape protein treatment. Ruminal ammonia concentrations in unsupplemented steers were low, with few values > 5 mg/dL. Based on in situ measurements, 42 to 54% of the forage protein escaped ruminal degradation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1993

Effect of synchronization of energy and nitrogen supply on ruminal characteristics and microbial growth.

The effect of energy and N synchronization in the rumen on microbial growth was investigated. The same daily amount of readily available energy and N sources (19 g of ruminally degradable N/kg of fermentable OM) was supplied intraruminally to sheep, according to different patterns, namely both energy and N as 12-hourly pulse-doses (fast synchronized supply), energy as 12-hourly pulse-doses and N as a continuous infusion (unsynchronized supply), energy as a continuous infusion and N as 12-hourly pulse doses (unsynchronized supply), and both energy and N as continuous infusions (slow synchronized supply). The study was done near maintenance (Exp. 1) and at a higher level of nutrition (Exp. 2). The degree of energy and N synchronization affected neither microbial flow nor efficiency of growth (P > .2 for energy x N interaction). Continuous infusion of energy resulted in a 17% (P < .05) and 14% (P = .18) higher efficiency of microbial growth than did pulse dosing in Exp. 1 and 2, respectively. This coincided with lower (P < .01) ruminal pH and higher (P < .05) ruminal lactic acid concentration for energy pulse-dose treatments. The results suggest that merely improving the degree of synchronization between energy and N release rates in the rumen does not increase microbial yield. Dietary manipulation, rather, should be aimed at first obtaining the most even ruminal energy supply pattern, and then at providing the appropriate amount of ruminally available N. Thereafter some further advantage may be gained in also ensuring a more even N supply pattern, particularly avoiding too rapid a ruminal N release.

Ammonia↗
PubMed1994

Effects of substituting feather meal for soybean meal on ruminal fiber fermentation and lamb and wool growth.

Our objective was to evaluate the effects of substituting feather meal (FM) for soybean meal (SBM) on ruminal fiber fermentation, lamb gain, blood metabolite profiles, and wool growth. A SBM supplement was formulated, and FM replaced either 33% (33FM), 66% (66FM), or 100% (FMS) of the SBM protein. Four ruminally cannulated wethers were used in a 4 x 4 Latin square design to study in situ ruminal digestion. Wethers were limit-fed barley straw and fed the supplements once daily. Ruminal NH3 N concentrations reflected a sampling time x protein source interaction (P < .01). Within sampling times, ruminal NH3 N concentrations decreased linearly (P < .05) as FM replaced soybean meal. Cubic (0 h; P < .10) and quadratic (24 h; P < .05) responses also were noted for ruminal NH3 N concentration. Substitution of FM for SBM had no effect (P > .10) on rate and extent of straw NDF disappearance. A 56-d feeding trial was conducted using 28 wether lambs (n = 7 per treatment; initial BW 32.3 kg). Wethers were individually fed chopped barley straw and one of the four supplements described previously. Linear increases (P < .05) in BW gain and serum total protein concentration were observed as FM replaced SBM. Wool fiber diameter and sulfur content did not differ (P > .10) among treatments. These data suggest that FM can be substituted for SBM in protein supplements fed to sheep consuming low-quality roughages at a maintenance level of ME intake.

Ammonia↗
PubMed1994

Concentrations of folates in ruminal content of steers: responses to a dietary supplement of folic acid in relation with the nature of the diet.

In an attempt to evaluate the ruminal effects of dietary supplements of folic acid, eight steers (352 +/- 27 kg BW) fitted with a ruminal cannula were randomly assigned to a replicated 4 x 4 Latin square design. The treatments were 70% rolled barley + 30% timothy hay (HC), HC + 2 mg of folic acid per kilogram of BW (HC + FA), 30% rolled barley + 70% timothy hay (HF), and HF + 2 mg of folic acid per kilogram of BW (HF + FA). After 5 wk of adaptation to the dietary treatments, ruminal contents were sampled over three consecutive days, at 1, 2, 4, 8, 12, and 23 h after feed distribution. Concentrations of folates in solid and liquid ruminal fractions were increased by the dietary supplement of folic acid (P = .0001) and by the ingestion of concentrate compared with hay-based diets (P < .05). Preprandial concentrations of serum folates were not affected by the nature of the diet when steers received no folic acid but the increase of serum folates induced by the dietary supplement of folic acid was more important in steers fed concentrates than in those fed hay-based diets (diet x supplement of folic acid interaction P = .002). Microbial protein (P = .004) and microbial mass (P = .002) in ruminal fluid were increased with concentrate-based diets compared with hay-based diets; folic acid did not have any effect on these variables (P > .05). In conclusion, concentrations of folates in ruminal contents were affected by dietary supplements of folic acid and by the nature of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1994

Binding of radiolabeled monensin and lasalocid to ruminal microorganisms and feed.

Gram-negative, ionophore-resistant ruminal bacteria and Gram-positive, ionophore-sensitive species bound similar amounts of [14C]lasalocid, but neither group bound large amounts of [14C]monensin. Membrane vesicles also bound more lasalocid than monensin (P < .05). The binding was first-order at low cell or vesicle concentrations and saturable at high cell or vesicle densities. Streptococcus bovis was inhibited by both monensin and lasalocid (5 microM), but cells that were re-incubated in medium lacking ionophore grew rapidly. Lasalocid-treated cells grew very slowly when they were resuspended in fresh medium. Based on these results, it seemed that lasalocid had a higher affinity for bacterial membranes than monensin. Mixed bacteria, however, bound nearly equal amounts of [14C]monensin and [14C]lasalocid (P > .05). Monensin binding was greatly reduced when the mixed ruminal bacteria were pretreated with Tris+EDTA (P < .05), but Tris+EDTA did not affect the binding of lasalocid. Mixed ruminal protozoa always took up more lasalocid than monensin (P < .05), but feed particles bound equal amounts of [14C]lasalocid and [14C]monensin (P > .05). Based on the binding capacity of mixed ruminal bacteria, ruminal protozoa, and feed particles, there would be little free ionophore in ruminal fluid.

Animal Feed↗
PubMed1994

Influence of feeding Aspergillus oryzae fermentation extract (Amaferm) on in situ fiber degradation, ruminal fermentation, and microbial protein synthesis in nonlactating cows fed alfalfa or bromegrass hay.

Daily additions of 3 g of Amaferm to alfalfa (13% CP) and bromegrass (6% CP) diets were evaluated for effects on ruminal and postruminal fiber and organic matter digestion, fermentation profile, and duodenal bacterial nitrogen flow. Eight beef cows were fitted with ruminal and duodenal cannulas. Two experiments were conducted. Eight cows were fed bromegrass hay, four received Amaferm and four served as controls; later, seven cows received alfalfa hay with three receiving Amaferm and four serving as controls. Each experiment lasted 28 d: d 1 to 14 for adaptation, d 15 to 21 for measurement of feed intake, and d 22 to 28 for ruminal and duodenal sampling. Dacron bags containing NDF substrate from alfalfa or bromegrass were used to determine ruminal fiber degradation at 3, 6, 9, 12, 24, 48, and 72 h. There were no Amaferm effects (P > .15) on rate or extent of fiber degradation in situ when bromegrass of alfalfa was fed. There were no Amaferm effects (P > .10) on concentrations or molar proportions of ruminal VFA, pH, or NH3 or on feed intake in either experiment. There were no effects (P > .10) of Amaferm on site or extent of organic matter or fiber digestion, or duodenal nitrogen flow in cows fed either bromegrass or alfalfa. Amaferm increased (P < .10) the number of ruminal anaerobic bacteria in cows fed bromegrass but not in those fed alfalfa.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1995

Influence of ruminal or abomasal starch hydrolysate infusion on pancreatic exocrine secretion and blood glucose and insulin concentrations in steers.

Seven Holstein steers (234 +/- 6.4 kg) surgically fitted with pancreatic cannulas, ruminal and abomasal infusion cannulas, and hepatic-portal vein catheters were used in a 4 x 7 incomplete Latin square design experiment to examine the influence of ruminal and abomasal carbohydrate infusion on enzyme secretion and composition of pancreatic juice. Four treatments were arranged in a 2 x 2 factorial: 1) ruminal starch hydrolysate (SH; 34.2 g/[h.site]) or abomasal water and 2) abomasal SH or ruminal water. Starch hydrolysate is raw cornstarch that has been partially digested by a heat-stable alpha-amylase. Experimental periods were 14 d with 9 to 10 d of adaptation, 4 d of pancreatic collection, and blood collection on d 14. Abomasal SH infusion tended (P < .10) to increase pancreatic fluid secretion. The pH of pancreatic juice was higher (P < .01) for ruminal SH infusion, and abomasal SH infusion tended (P < .10) to result in lower pH of pancreatic juice. alpha-Amylase concentrations (units/milliliter and units/milligram of protein) and secretion (units/hour) were less (P < .002) for abomasal SH infusion. Chymotrypsin concentration (units/liter; P < .01) and secretion (units/hour; P < .10) were less for abomasal SH infusion; however, a rumen x abomasal interaction was found (P < .05). Chloride concentration (milligrams/deciliter) and secretion (milligrams/hour) were increased (P < .01) for abomasal SH infusion. Abomasal SH infusion resulted in increased (P < .01) portal blood glucose concentrations; however, portal plasma insulin concentration was not affected (P > .10). Abomasal SH infusion altered alpha-amylase secretion in steers, but ruminal SH infusion had minimal effect on alpha-amylase secretion. These changes suggest abosamal infusion of SH may negatively impact secretion of pancreatic alpha-amylase.

Abomasum↗
PubMed1995

Supplemental protein sources for steers fed corn-based diets: I. Ruminal characteristics and intestinal amino acid flows.

Five cannulated Holstein steers (302 +/- 23 kg) were used in a 4 x 4 Latin square design experiment with extra observations to evaluate the effect of supplemental protein source on postruminal flow and intestinal disappearance of N and amino acids (AA). Diets were formulated to contain 12.5% CP using cracked corn (70%), ground corn cobs (15%), and supplement (15%). Except for an all-urea supplemented control diet, 40% of the total dietary CP was supplied by soybean meal (SBM), a high ruminal escape soybean meal (SoyPLUS; SP), or a corn gluten meal/blood meal combination (CB; 50:50 on a CP basis). The steers were fed twice daily and DMI was restricted to 2.0% of initial BW. Supplementation with CB increased (P < .10) non-microbial N flow at the duodenum but tended to decrease microbial N flow such that no differences (P > .10) in total N flows at the duodenum were detected among treatments. The efficiency of microbial protein synthesis was not affected by treatment but was greatest for urea/and tended to decrease when SP and CB were fed (21.8, 20.5, 19.5, and 15.7 g of N/kg of OM truly digested for urea, SBM, SP, and CB, respectively). A possible shortage of ruminally degradable N, as evidenced by low ruminal NH3 N concentrations (3.6, 4.2, 3.9, and 2.1 mg/dL for urea, SBM, SP, and CB respectively), or other factors, may have limited microbial protein synthesis. However, microbial N flows averaged 60.0% of duodenal N flow across treatments. Duodenal flow of essential, nonessential, and total AA were similar (P > .10) among treatments and averaged 293, 361, and 653 g/d, respectively). Lysine and methionine flows did not differ (P > .10) and averaged 41.6 and 13.3 g/d, respectively. The source of supplemental protein had no impact (P > .10) on small intestinal disappearance of AA or total tract N disappearance. Feeding proteins resistant to ruminal degradation may have limited microbial protein production, resulting in a shift in the proportion of metabolizable protein arriving at the small intestine from dietary and microbial origins. These results suggest that corn-based diets may be limiting in ruminally degradable N, especially when high ruminal escape protein sources are fed as supplemental CP.

Amino Acids↗
PubMed1995

Portal and hepatic fluxes in sheep and concentrations in cattle ruminal fluid of 3-(4-hydroxyphenyl)propionic, benzoic, 3-phenylpropionic, and trans-cinnamic acids.

Extraction methods and HPLC procedures were developed for analysis of potential ruminal metabolites of dietary phenolics (reduced phenolics). Hepatic portal venous blood from wethers fed bromegrass, bermudagrass, ryegrass-wheat, and alfalfa hays also was analyzed for hippuric (HA), 3-(4-hydroxyphenyl)propionic (4OHPPA), benzoic (BA), 3-phenylpropionic (PPA), and t-cinnamic (CA) acids. Additionally, mesenteric arterial and hepatic venous blood was analyzed and, in conjunction with blood flow measurements, fluxes for portal-drained viscera (PDV) and liver were calculated. Ruminal fluid from four steers fed two levels of forage and two forage particle sizes in a Latin square design was analyzed for PPA and CA. 3-Phenylpropionic and benzoic acids were the most concentrated reduced phenolics identified in hepatic portal venous blood. Concentrations of PPA in ruminal fluid varied with ruminal disappearance of p-coumaric and ferulic acids. Additionally, hepatic portal venous concentrations of PPA were correlated (P < .05) with p-coumaric acid (r = .57) and ferulic acid (r = .67) intakes. Net release of PPA from PDV was observed, suggesting absorption of PPA from the gut. The liver removed PPA and BA with less efficiency. Given the relatively high concentrations of PPA in blood of ruminants, specific effects of this reduced phenolic on liver metabolism of ruminants should be assessed.

Animals↗
PubMed1997

Effect of forage quality and monensin on the ruminal fermentation of fistulated cows fed continuously at a constant intake.

A ruminal fermentation study was used to investigate the relationship between forage quality and monensin-dependent amino acid-sparing. Two fistulated cows were fed three concentrations of chopped (2.5 to 5.0 cm in length) timothy and alfalfa hays (100:0, 50:50 and 0:100) and two levels of monensin (0 and 350 mg.cow-1.d-1). The diets were offered 12 times per day (9 kg of DM/d), and the rumen reached a steady-state, reducing animal and day variation. Alfalfa hay had 1.4 times more CP and 1.4 times less NDF than timothy hay, and the substitution of timothy with alfalfa increased (P < .05) ruminal ammonia. Monensin had no effect on total ruminal ammonia when timothy hay was present in the diet, and it increased total ruminal ammonia with the 100% alfalfa diet. Effects on ruminal ammonia were, however, confounded by monensin-dependent decreases in ruminal pH (P < .05). Dissociated ammonia, the species most likely to be adsorbed from the rumen, declined when monensin was added to the 100% timothy diet (P < .05). Monensin had no effect on dissociated ammonia if alfalfa was 50% or 100% of the forage, but it counteracted alfalfa-dependent decreases in bacterial protein (P < .05). The idea that monensin could spare amino acids was supported by the observation that monensin decreased (P < .001) the specific activity of deanimation and increased bacterial protein at all combinations of alfalfa and timothy. Increases in bacterial protein could be explained by monensin-dependent increases in total VFA.

Ammonia↗
PubMed1997

Comparative ruminal and total tract digestion of a finishing diet containing fresh vs air-dry steam-flaked corn.

Ten Holstein steers (465 +/- 6 kg) with cannulas in the rumen and proximal duodenum were used in a crossover design experiment to evaluate the influence of air-dry vs fresh steam-flaked corn on characteristics of ruminal and total tract digestion. The basal diet contained 77% steam-flaked corn (DM basis). Air-dry steam-flaked corn (SFC-AD) was obtained from a single batch that had been allowed to air-dry for 5 d before beginning the trial. Fresh steam-flaked corn (SFC-F) was produced daily Monday through Friday. Following production, the SFC-F was placed in air-tight polybags and stored at 4 degrees C until the time of feeding. There was little difference (P > .20) between SFC-AD and SFC-F with respect to site and extent of digestion of OM, starch, and fiber. Moreover, the two treatments did not differ (P > .20) in ruminal degradability of feed N. Apparent total tract N digestion was slightly greater (2.4%, P < .05) for SFC-F than for SFC-AD. Treatments did not affect ruminal pH (P > .20); however, VFA concentration of ruminal fluid tended to be greater (8.3%, P < .10) for SFC-F than for SFC-AD, indicating that the initial rate of fermentation may have been greater with SFC-F. Ruminal molar proportions of acetate were not affected by treatments (P > .20), but ruminal molar proportions of propionate tended to be greater (9.7%, P < .10) and molar proportions of butyrate tended to be less (10.0%, P < .10) for SFC-F than for SFC-AD. We conclude that the characteristics of digestion and the feeding value of steam-flaked corn is not altered by air drying before feeding.

Animals↗
PubMed1998

Supplemental protein plus ruminally protected methionine and lysine for primiparous beef cattle consuming annual rye hay.

Primiparous beef cows (n = 35 Bos taurus, average initial BW of 498 kg) were allotted to treatments in a split-plot designed experiment to determine the effects of supplemental ruminally protected amino acids on cow and calf productivity and metabolic changes in the cows. Cows were fed chopped annual rye hay at 1.5% of BW. The following treatments were used: 1) .8 kg soybean hulls, 1.4 kg ground corn, .6 kg soybean meal (CON); 2) 1.4 kg ground corn, 1.4 kg soybean meal (PRO); 3) PRO plus ruminally protected methionine and lysine (supplied 5 and 10 g, respectively; PRO1); and 4) PRO with twice the level of ruminally protected amino acids in PRO1 (PRO2). Cow weight gain was not different (P > .26) among treatments and averaged 1.2 kg/d for the 45 + 6 d before parturition. After parturition, cow weight gain did not differ (P > .47) between CON and PRO treatments, but it decreased quadratically (P < .01) with increasing level of ruminally protected amino acids. Total milk yield, protein, and fat (4 h) were greater (P < .05) for cows consuming PRO supplements than for CON, whereas CON cattle tended (P = .11) to lose less body condition. Total milk protein showed a quadratic increase (P < .05) in response to level of ruminally protected amino acids that was the inverse of the quadratic response noted for cow weight gain. Serum urea N concentration was greater (P = .07) for cattle consuming additional protein. Metabolic hormones were not affected (P > .18) by dietary treatment, but they responded (P < .05) to changes in physiological state. Supplements with additional protein supported greater (P = .0001) milk urea N concentration and output. Milk urea N concentration increased (P < .05) and milk IGF-I decreased (P < .05) as the lactation period progressed. The measurement of CON and PRO diets revealed that supplements with additional soybean meal had greater (P < .05) DM and N degradation; the extent of forage DM and NDF degradation was similar (P > .05) among treatments. Production shifted away from body weight gain to increased milk protein production when daily supplementation of ruminally protected methionine and lysine increased from 5 and 10 to 10 and 20 g, respectively. This shift in production was not reflective of changes in the metabolic regulators measured.

Animal Feed↗
PubMed1998

Nutritional evaluation of poultry by-product meal as a protein source for ruminants: effects on performance and nutrient flow and disappearance in steers.

We conducted three studies with steers to evaluate poultry by-product meal (PBM) as a supplemental N source for ruminants. An in situ study compared the solubility, degradation rate, and ruminal escape of PBM N with blood meal (BM), corn gluten meal (CGM), and soybean meal (SBM) N. Additionally, an 84-d growth study (n = 95, 228+/-5 kg BW) and a digestion trial (6 x 6 Latin square) were conducted. The basal diet for the growth and digestion studies consisted of 49% corn silage, 36% cottonseed hulls, and 15% supplement (DM basis). Sources of supplemental N (% of total supplemental N) were 100% SBM and 0, 25, 50, 75, and 100% PBM, with urea used to balance for N. In situ ruminal escape N (25.2, 55.3, 86.7, and 98.9% for SBM, PBM, CGM, and BM, respectively) was greater (P < .05) for PBM than for SBM; however, a greater (P < .05) proportion of BM and CGM N escaped ruminal degradation compared with PBM. Dry matter intake, ADG and gain/ feed increased linearly (P < .003) as PBM increased; however, no differences (P > .48) were observed in these variables for 100% PBM compared with 100% SBM. Duodenal N flow and small intestinal N disappearance increased linearly (P < .05) as PBM increased in the diet. Bacterial N flow to the small intestine was not affected (P > .19) by treatment; however, 100% SBM decreased (P < .04) bacterial CP synthesis (g bacterial N/kg OM disappearance from the stomach) compared with 0 and 100% PBM. In vivo ruminal escape N of PBM and SBM was 40.6 and 13.7%, respectively. Ruminal NH3 N decreased linearly (P < .001) as PBM increased. These data suggest that PBM can replace SBM as a source of supplemental N for steer calves that consume a diet based on corn silage and cottonseed hulls.

Ammonia↗
PubMed1999

Effects of a return chewing gum/packaging material mixture on in situ disappearance and on feed intake, nutrient digestibility, and ruminal characteristics of growing steers.

In situ and in vivo digestibility experiments were conducted to determine the acceptability, digestibility, and safety of a return chewing gum/packaging (G/P) material mixture when fed to steers. In the in situ experiment, both ruminal and intestinal disappearances were measured. Two ruminally and duodenally cannulated steers, which were given free access to alfalfa hay (AH), were used in this study. Duplicate Dacron bags containing the G/P were incubated in the rumen for 0, 3, 6, 12, 24, and 48 h. After ruminal incubation, the 12-, 24-, and 48-h bags were placed in the duodenum and collected in the feces to determine intestinal disappearance. In situ ruminal DM disappearance was greater than 70% for all substrates tested at 0 h, indicating high solubility of the substrates in water, and began to reach a plateau after 12 h of incubation. Intestinal in situ disappearance was not different (P>.25) from zero. In the digestion trial, four ruminally cannulated steers (337+/-21.3 kg BW; mean +/- SD) were used in a 4x4 Latin square design with the following treatments: 0) 50% corn (C), 50% AH; 10) 45% C, 45% AH, 10% G/P; 20) 40% C, 40% AH, 20% G/P; 30) 35% C, 35% AH, 30% G/P. Steers fed G/P-containing diets had greater (P<.01) DMI than the control steers. Increasing the G/P resulted in a linear (P<.05) increase in DMI. Apparent DM digestibility tended to be higher (P<.10) for the G/P-containing diets than for the control. A quadratic effect (P<.05) on digestible DMI was observed, with greater (P<.01) digestible DMI values for G/P-containing diets (4.8 vs. 5.8 kg/d). Digestible organic matter and total nonstructural carbohydrate intakes followed trends similar to those of DM. Apparent aluminum digestibility of G/P-containing diets was not different (P>.13) from zero. The level of G/P in the diet had no effect (P>.2) on total VFA concentration or ruminal pH. There was a linear decrease (P<.01) in the molar percentage of isobutyrate and isovalerate in addition to a linear increase (P<.01) in butyrate and valerate with increasing levels of G/P. There was a quadratic effect (P<.01) on molar proportions of acetate and propionate and on the acetate:propionate ratio. Results of both experiments suggest that G/P may be fed to safely replace up to 30% of corn-alfalfa hay diets for growing steers with advantages in improving DMI and digestibility.

Animals↗
PubMed1999

Relationship between ruminal starch degradation and the physical characteristics of corn grain.

The objectives of this study were to determine the range of variation in the rate and extent of in situ ruminal starch degradation of 14 corns differing in vitreousness and to predict ruminal starch degradability by physical characteristics of corn grains. This study was conducted with eight dent and six flint corns. Ruminal starch degradability was determined by an in situ technique on 3-mm ground grains. Physical characteristics of corn grain were measured: hardness by grinding energy and particle size distribution, apparent and true densities, and specific surface area. Ruminal DM and starch degradabilities averaged 50 and 55.1% and varied from 39.7 to 71.5% and from 40.6 to 77.6%, respectively. Ruminal starch degradability averaged 61.9 and 46.2% in dent and flint types, respectively. The proportion of coarse particles (61.9 vs. 69.6% for dent and flint, respectively), the apparent density (1.29 vs. 1.36 g/cm3 for dent and flint, respectively), and the specific surface area (.13 vs. .07 m2/g for dent and flint, respectively) varied with the vitreousness. Ruminal starch degradability could be predicted accurately by vitreousness (r2 = .89) or by the combination of apparent density and 1,000-grain weight (R2 = .91), a measurement faster than the vitreousness determination.

Animal Feed↗
PubMed1999

Effects of ruminal administration of supplemental degradable intake protein and starch on utilization of low-quality warm-season grass hay by beef steers.

Hereford x Angus steers were used in a 13-treatment, four-period, incomplete Latin square design to examine the effects of starch and degradable intake protein (DIP) supplements on forage utilization and ruminal function. Steers were given ad libitum access to low-quality hay (4.9% CP) and were not supplemented (NS) or received different amounts of starch (cornstarch grits; 0, .15, and .3% of initial BW) and DIP (Na-caseinate; .03, .06, .09, and .12% of initial BW) administered via ruminal fistulae in a 3 x 4 factorial arrangement of treatments. Supplemented steers consumed more (P < .01) forage OM, total OM, NDF, and digestible OM (DOM) than NS steers. Forage OM, total OM, NDF, and DOM intakes increased linearly (P < .01) as the amount of supplemental DIP increased. The addition of starch to supplements linearly decreased ( P < .01) the intake of forage OM, NDF, and DOM. The digestion of DM, OM, and NDF increased linearly (P < .01) with supplemental DIP and decreased linearly (P < or = .06) with supplemental starch. Particulate and liquid passages generally increased with DIP; however, starch level influenced the nature of the response (P = .03 and .06, respectively). Similarly, ruminal acid detergent-insoluble ash content generally decreased as starch increased, but the effect was dependent on DIP level (P < .01). Supplementation increased (P < .01) ruminal NH3 and total VFA and decreased (P < .01) ruminal pH relative to NS. All treatments supported average pH values in a range (6.3 to 6.7) unlikely to inhibit fibrolytic bacteria. Ruminal NH3 concentration increased quadratically (P = .03) with DIP and decreased linearly (P = .02) with starch. As DIP increased, total VFA concentration increased linearly (P = .02). Providing supplemental DIP to steers fed low-quality forage increased OM intake and digestion, whereas addition of starch to supplements decreased forage intake and digestion.

Animal Feed↗