Supplementing barley or rapeseed meal to dairy cows fed grass-red clover silage: II. Amino acid profile of microbial fractions

Four ruminally cannulated dairy cows were used to examine the effect of diet on the AA composition of rumen bacteria and protozoa, and the flow of microbial and nonmicrobial AA entering the omasal canal. Cows were offered grass-red clover silage alone, or that supplemented with 5.1 kg DM of barley, 1.9 kg DM of rapeseed meal, or 5.1 kg DM of barley and 1.9 kg DM of rapeseed meal according to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. During the first 10 d of each period, cows had free access to silage and, thereafter intake was restricted to 95% of ad libitum intake. Postruminal digesta flow was assessed using the omasal canal sampling technique in combination with a triple marker method. Liquid- (LAB) and particle- (PAB) associated bacteria were isolated from digesta in the reticulorumen and protozoa from digesta entering the omasal canal. Microbial protein flow was determined using 15N as a microbial marker. Flows of AA entering the omasal canal were similar in cows fed silage diets supplemented with barley or rapeseed meal. However, rapeseed meal increased nonmicrobial AA flow while barley increased the flow of AA associated with LAB and protozoa. Diet had negligible effects on the AA profile of microbial fractions. Comparison of AA profiles across diets indicated differences between LAB and PAB for 10 out of 17 AA measured. Rumen bacteria and protozoa were found to be different for 14 out of 15 AA measured. For grass silage-based diets, energy and protein supplementations appear to alter postruminal AA supply through modifications in the proportionate contribution of microbial and nonmicrobial pools to total protein flow rather than as a direct result of changes in the AA profile of microbial protein.     

Effects of Supplementation of a Grass Silage and Barley Diet with Urea,Rapeseed Meal and Heat-moisture-treated Rapeseed Cake on Omasal Digesta Flow and Milk Production in Lactating Dairy Cows

Four multiparous dairy cows, fitted with rumen and duodenal cannulas, were fed grass silage and one of four concentrates of barley (B), barley+urea (BU), barley+solvent-extracted rapeseed meal (BRM) or barley+heat-moisture-treated rapeseed cake (BRC). Despite marginal N deficiencies for the control diet (B), BU did not affect milk yield, ruminal fibre digestion or omasal total non-ammonia-N (NAN) or microbial NAN flow. In contrast, BRM and BRC diets significantly increased milk and milk protein yields and omasal dietary NAN flows. Effects of rapeseed meal (RSM) and rapeseed cake (RSC) on milk yield and omasal NAN flow were similar. The diets had no effect on rumen microbial protein synthesis. In general, non-protein N and soluble true protein comprised 0.20 of omasal total NAN flow, for all diets. Supplementary AAT from rapeseed feeds appeared to escape from the rumen as insoluble feed particles.     

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.     

Effects of supplemental ruminally degradable protein versus increasing amounts of supplemental ruminally undegradable protein on site and extent of digestion and ruminal characteristics in lambs fed low-quality forage

Four ruminally and duodenally cannulated Suffolk wether lambs (34.5 +/- 2 kg initial BW) were used in a 4 x 4 Latin square designed experiment to compare effects of supplemental ruminally degradable protein (RDP) vs. increasing amounts of supplemental ruminally undegradable protein (RUP) on ruminal characteristics and site and extent of digestion in lambs. Lambs were fed a basal diet of crested wheatgrass hay (4.2% CP) for ad libitum consumption, plus 1 of 4 protein supplements: isolated soy protein (RDP source) fed to meet estimated RDP requirements assuming a microbial efficiency of 11% of TDN (CON) or corn gluten meal (RUP source) fed at 50, 100, or 150% of the supplemental N provided by CON (C50, C100, and C150, respectively). Neither NDF nor ADF intake was affected (P >/= 0.18) by protein degradability, but they increased or tended to increase (P /= 0.26) for CON and C100, but increased (P /= 0.33) by protein degradability. However, true ruminal N digestibility was greater (P = 0.03) for CON compared with C100. Ruminal ammonia concentrations were greater (P = 0.002) for CON compared with C100 lambs, and increased (P = 0.001) with increasing RUP. Microbial N flows were not affected (P >/= 0.12) by protein degradability or increasing RUP. Likewise, neither ruminal urease activity (P >/= 0.11) nor microbial efficiency (P >/= 0.50) were affected by protein degradability or level of RUP. Total tract OM, NDF, and ADF digestibility was greater (P 相似文献   

Effect of nitrogen source in high-concentrate, low-protein beef cattle diets on microbial fermentation studied in vivo and in vitro

In Exp. 1, four Holstein heifers (112+/-5.5 kg BW) fitted with ruminal cannulas were used in a 4 x 4 Latin square to evaluate the effects of N source on ruminal fermentation and urinary excretion of purine derivatives. A 2 x 2 factorial arrangement of treatments was used; the factors were the type of protein source (soybean meal, SBM, vs a 50:50 mixture of fish meal and corn gluten meal, FMCGM) and the partial substitution of protein source by urea (with vs without). Heifers were allowed to consume concentrate and barley straw on an ad libitum basis. Barley straw:concentrate ratio (12:88) and average ruminal pH (6.25) were not affected (P > 0.05) by treatment. Ruminal NH3 N concentration and urinary excretion of purine derivatives were not affected (P > 0.05) by supplemental N source. In situ CP degradability of supplemented SBM was very low (50%). In Exp. 2, eight dual-flow continuous-culture fermenters were used to study diet effects on microbial fermentation and nutrient flow, using forage:concentrate ratio, solid and liquid passage rates, and pH fluctuation to simulate in vivo conditions. The treatment containing SBM without urea reached the greatest total VFA concentration (P < 0.01), molar percentage of acetate (P < 0.05), and NH3 N concentration (P < 0.05), followed by treatments with partial substitution of protein source by urea, and finally by the treatment containing FMCGM. True OM digestion tended to increase (P = 0.13) in treatments containing SBM. These results suggest that amino N from SBM and NH3 N concentration stimulated nutrient digestion. Microbial protein synthesis was lowest in treatments with FMCGM and without urea, indicating that rapidly available N limited microbial growth. The low CP degradability of SBM observed may have contributed to the limitation in N supply for microbial growth. Efficiency of microbial protein synthesis increased in treatments containing urea (P < 0.05). Protein source affected total (P < 0.05) and essential AA (P < 0.10) flows, which were greater in treatments containing FMCGM. Partial replacement of protein supplements by urea did not affect total and essential AA flows. Because mean dietary protein contribution to total N effluent was 46%, the AA profile of supplemental protein sources had a great impact on total AA flow and its profile.     

Effects of protein concentration and degradability on performance, ruminal fermentation, and nitrogen metabolism in rapidly growing heifers fed high-concentrate diets from 100 to 230 kg body weight

Twenty crossbred heifers (101 +/- 4.5 kg BW) were used to examine the effects of protein concentration and degradability on performance, ruminal fermentation, nutrient digestion, N balance, and urinary excretion of purine derivatives. Heifers were offered concentrate and barley straw for ad libitum consumption. Two protein concentrations (17 vs 14%, DM basis) and two protein sources differing in ruminal degradability (58 vs 42% of CP for soybean meal and treated soybean meal, respectively) were tested. The experiment was divided into four consecutive 28-d periods to evaluate the age (period) effect. Increasing protein concentration and degradability did not improve ADG or intake (P > .05). The increase in urinary N excretion (P < .001) in heifers fed 17% CP suggests that N was in excess of requirements. When the low-degradable protein source was supplemented and(or) CP concentration was low, ruminal NH3 N concentrations fell below 5 mg/100 mL. Urinary excretion of purine derivatives was not affected (P > .05) by protein concentration and degradability, suggesting that in high-concentrate diets NH3 N concentration was not limiting microbial growth. Total VFA concentration decreased (P < .001) and the acetate:propionate ratio increased (P < .01) with advancing period, suggesting an increase in ruminal absorption capacity and an increase in fiber fermentation. The decrease in ruminal NH3 N concentration in the last period suggests a greater use of NH3 N by microorganisms. This hypothesis is supported by the increase (P < .001) in urinary excretion of allantoin and estimated duodenal flows of purine bases and microbial protein with advancing period. Reducing CP concentration and increasing ruminal undegradable protein supply did not affect animal performance or estimated duodenal flow of microbial protein in rapidly growing heifers fed high-concentrate diets.     

Supplementing a ruminally undegradable protein supplement to maintain essential amino acid supply to the small intestine when forage intake is restricted in beef cattle

Twelve Angus crossbred cattle (eight heifers and four steers; average initial BW = 594 +/- 44.4 kg) fitted with ruminal and duodenal cannulas and fed restricted amounts of forage plus a ruminally undegradable protein (RUP) supplement were used in a triplicated 4 x 4 Latin square design experiment to determine intestinal supply of essential AA. Cattle were fed four different levels of chopped (2.54 cm) bromegrass hay (11.4% CP, 57% NDF; OM basis): 30, 55, 80, or 105% of the forage intake required for maintenance. Cattle fed below maintenance were given specified quantities of a RUP supplement (6.8% porcine blood meal, 24.5% hydrolyzed feather meal, and 68.7% menhaden fish meal; DM basis) designed to provide duodenal essential AA flow equal to that of cattle fed forage at 105% of maintenance. Experimental periods lasted 21 d (17 d of adaptation and 4 d of sampling). Total OM intake and duodenal OM flow increased linearly (P < 0.001) as cattle consumed more forage; however, OM truly digested in the rumen (% of intake) did not change (P = 0.43) as intake increased. True ruminal N degradation (% of intake) tended (P = 0.07) to increase linearly, and true ruminal N degradation (g/d) decreased quadratically (P = 0.02) as intake increased from 30 to 105%. Duodenal N flow was equal (P = 0.33) across intake levels, even though microbial N flow increased linearly (P < 0.001) as forage OM intake increased. Total and individual essential AA intake decreased (cubic; P < 0.001) as forage intake increased because the supply of nonammonia, nonmicrobial N flow from RUP was decreased (linear; P < 0.001) by design. Total duodenal flow of essential AA did not differ (P = 0.39) across these levels of forage intake. Although the profile of essential AA reaching the duodenum differed (P < or = 0.02) for all 10 essential AA, the range of each essential AA as a proportion of total essential AA was low (11.1 to 11.2% of total essential AA for phenylalanine to 12.3 to 14.3% of total essential AA for lysine). Duodenal essential AA flow did not differ (P = 0.10 to 0.65) with forage intake level for eight of the 10 essential AA. Duodenal flow of arginine decreased linearly (P = 0.01), whereas duodenal flow of tryptophan increased linearly (P = 0.002) as forage intake increased from 30 to 105% of maintenance. Balancing intestinal essential AA supply in beef cattle can be accomplished by varying intake of a RUP supplement.     

Effects of increasing level of supplemental barley on forage intake, digestibility, and ruminal fermentation in steers fed medium-quality grass hay

Objectives of this research were to evaluate effects of increasing level of barley supplementation on forage intake, digestibility, and ruminal fermentation in beef steers fed medium-quality forage. Four crossbred ruminally cannulated steers (average initial BW = 200 +/- 10 kg) were used in a 4 x 4 Latin square design. Chopped (5 cm) grass hay (10% CP) was offered ad libitum with one of four supplements. Supplements included 0, 0.8, 1.6, or 2.4 kg of barley (DM basis) and were fed in two equal portions at 0700 and 1600. Supplements were fed at levels to provide for equal intake of supplemental protein with the addition of soybean meal. Forage intake (kg and g/kg BW) decreased linearly (P < 0.01), and total intake increased linearly (P < 0.03) with increasing level of barley supplementation. Digestible OM intake (g/kg BW) increased linearly (P < 0.01) with increasing level of barley supplementation; however, the majority of this response was observed with 0.8 kg of barley supplementation. Treatments had only minor effects on ruminal pH, with decreases occurring at 15 h after feeding in steers receiving 2.4 kg of barley supplementation. Total-tract digestibility of DM, OM, NDF, and CP were increased (P < 0.04) with barley supplementation; however, ADF digestibility was decreased by 1.6 and 2.4 kg of barley supplementation compared with controls. Ruminal ammonia concentrations decreased linearly (P < 0.01) at 1 through 15 h after feeding. Total ruminal VFA concentrations were not altered by dietary treatments. Ruminal proportions of acetate and butyrate decreased (P < 0.10) in response to supplementation. Rate, lag, and extent (72 h) of in situ forage degradability were unaffected by treatment. Generally, these data are interpreted to indicate that increasing levels of barley supplementation decrease forage intake, increase DM, OM, and NDF digestibility, and indicate alteration of the ruminal environment and fermentation patterns.     

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.     

Effects of cooked molasses blocks and fermentation extract or brown seaweed meal inclusion on intake, digestion, and microbial efficiency in steers fed low-quality hay

Five ruminally, duodenally, and ileally cannulated steers (376 +/- 8.1 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of cooked molasses block supplementation and inclusion of fermentation extract (Aspergillus oryzae) or brown seaweed meal (Ascophyllum nodosum) on intake, site of digestion, and microbial efficiency. Diets consisted of switchgrass hay (6.0% CP; DM basis) offered ad libitum, free access to water, and one of three molasses blocks (0.341 kg of DM/d; one-half at 0600 and one-half at 1800). Treatments were no block (control), block with no additive (40.5% CP; POS), block plus fermentation extract bolused directly into the rumen via gelatin capsules (2.0 g/d; FS), fermentation extract included in the block (2.0 g/d; FB), and seaweed meal included in the block (10 g/d; SB). Steers were adapted to diets for 14 d followed by a 7-d collection period. Overall treatment effect on hay OM intake tended (8.1 vs. 7.6 +/- 0.5 kg/d; P = 0.14) to increase with block supplementation. Total OM intake (8.4 vs. 7.6 +/- 0.5 kg/d; P = 0.01) increased in steers consuming block compared with control. Apparent and true ruminal OM digestibility increased (P = 0.05) with block consumption. Steers fed SB had greater (P = 0.10) true ruminal OM digestibility compared with steers fed POS (61.0 vs. 57.9 +/- 1.6%). True ruminal CP digestibility increased (P = 0.01) with block supplementation compared with control (37.5 vs. 23.6 +/- 3.7%). Addition of fermentation extract did not affect intake or digestion. Treatments did not alter ruminal pH, total VFA, or individual VFA proportions; however, ruminal ammonia increased (P = 0.01) with block supplementation. In situ disappearance rates of hay DM (3.14 +/- 0.44 %/h), NDF (3.18 +/- 0.47 %/h), and ADF (3.02 +/- 0.57 %/h) were not altered by treatment. Seaweed block increased (P = 0.01) slowly degraded CP fraction compared with POS (39.5 vs. 34.0 +/- 2.07%). Similarly, SB increased (P = 0.01) the extent of CP degradability (74.2 vs. 68.9 +/- 1.81%). No treatment effects (P = 0.24) were observed for microbial efficiency. Block supplementation increased intake, and use of brown seaweed meal seemed to have beneficial effects on forage digestibility in low-quality forage diets.     

Rumen fermentation, microbial protein synthesis, and nutrient flow to the omasum in cattle offered corn silage, grass silage, or whole-crop wheat

The objectives of this study were to determine the relative effect of feeding corn silage (CS), fermented whole-crop wheat (FWCW), and urea-treated processed whole-crop wheat (UPWCW) compared with grass silage (GS), each supplemented with concentrates, on forage intake, ruminal fermentation, microbial protein synthesis, some plasma metabolites, and ruminal and total tract digestibility in cattle. Four ruminally fistulated steers with a mean BW of 509 kg (SD 6.3) were used in a 4 x 4 Latin square-designed experiment with each period lasting 21 d. The omasal sampling technique in combination with a triple marker method was used to measure nutrient flows to the omasum with Co-EDTA, Yb acetate, and indigestible NDF as liquid, small particle, and large particle phase markers, respectively. Microbial N flow was assessed from purine base concentrations. Steers fed CS, FWCW, and UPWCW consumed 2.7, 2.4, and 2.6 kg/d more (P < 0.05) forage and total DMI, respectively, than those fed GS-based diets. Rumen pH (P = 0.07) and lactic acid (P = 0.11) concentration did not differ between the forages. Rumen concentration of NH(3)-N was greatest for UPWCW and least for CS (P < 0.001). Total VFA concentrations were greater (P < 0.05) for CS than GS and UPWCW, with FWCW being intermediate. Acetate-to-propionate ratio (P < 0.05) was greater (P < 0.05) for UPWCW than the other forages, which did not differ. Apparent ruminal digestion of OM (P < 0.05) was less for CS, FWCW, and UPWCW than GS. Ruminal NDF digestibility was greater (P < 0.01) for GS than the other forages, which did not differ (P > or = 0.06). Total tract NDF digestibility was less (P < 0.05) for UPWCW than the other forages, with GS being greatest and CS and FWCW being intermediate. Starch intake was less (P < 0.001) for GS than the other forages, but there was no effect of forage on omasal starch flow (P = 0.23) or ruminal digestibility (P = 0.88). Flow of non-NH(3)-N and microbial N was greater (P < 0.05) for CS, FWCW, and UPWCW than GS. Efficiency of microbial N synthesis was greater (P < 0.05) for FWCW than GS and CS, with UPWCW being intermediate. Plasma beta-hydroxybutyrate concentrations were greatest with CS and least for GS (P < 0.001), whereas concentrations of plasma urea were least for CS and greatest for UPWCW (P < 0.001). In conclusion, feeding alternative forages to GS can significantly increase feed DMI and alter rumen fermentation and site of nutrient digestion when offered to cattle supplemented with 3 kg of concentrate daily.     

Effect of grain processing and silage on microbial protein synthesis and nutrient digestibility in beef cattle fed barley-based diets

Effects of the extent of grain processing and the percentage of silage in barley-based feedlot diets on microbial protein synthesis and nutrient digestibility were evaluated using four steers (initial BW of 442 +/- 15 kg) with ruminal and duodenal cannulas. The experiment was a 4 x 4 Latin square with four periods of 21 d each. Dietary treatments were arranged as a 2 x 2 factorial with two levels of barley silage (20 and 5% DM basis) and two degrees of barley grain processing (coarsely and flatly steamrolled to a processing index [PI] of 86 and 61%, respectively). The PI was quantified as the volume weight of the barley grain after processing, expressed as a percentage of the volume weight prior to processing. Digest a flow (Yb) and microbial (15N) markers were continuously infused into the rumen for a period of 13 d. Ruminal, duodenal, and fecal samples were collected at various times over the last 6 d of marker infusion. Diurnal ruminal pH was measured for 48 h. Intake of DM averaged 1.8% of BW, and was not different among the dietary treatments (P > 0.10). Ruminal starch digestibility was higher (P < 0.05) for the more extensively processed grain and tended (P < 0.10) to be highest when the more extensively processed grain was combined with 5% barley silage. In contrast, ruminal fiber digestibility for the 5% silage diets was reduced (P < 0.05) when the grain was more extensively processed. There was, however, no effect of grain processing on ruminal OM digestibility (P > 0.10), and hence, no inhibitory effect on microbial N flow to the intestine (P > 0.10). There was also no effect of the level of silage on microbial N flow (P > 0.10), but there was a tendency for improved efficiency of microbial protein synthesis for the 20% silage diets (P = 0.072). Ruminal escape of nonmicrobial N (P = 0.003) was greater, and thus, protein flow to the intestine was greater for the 5% silage diets. Diurnal ruminal pH was lower (P < 0.05) for 11 of the 24 hourly time points in steers fed the 5% silage diets than those fed the 20% silage diets. In conclusion, barley grain rolled to a PI of 86 to 61% and combined with 20 and 5% barley silage had little effect on microbial protein supply. Microbial protein supply was not inhibited when the barley grain was extensively processed (PI of 61%) and the silage was limited to only 5% of the diet DM, but feed intake of steers in this study was lower than would be expected in the feedlot.     

Effects of starch and protein sources on starch disappearance in the gastrointestinal tract of Hanwoo (Korean native) steers

Hanwoo (Korean native) steers (274.8 ± 4.6 kg) with ruminal and duodenal cannulae were used in a 4 × 4 Latin square design experiment to examine the effects of dietary treatments on starch disappearance in the gastrointestinal tract. Dietary treatments consisted of concentrate that were based on ground corn with soybean meal (C‐SBM), ground corn with corn gluten meal (C‐CGM), ground barley with soybean meal (B‐SBM) and ground barley with corn gluten meal (B‐CGM). Although the intakes of starch and protein for steers fed experimental diets were different, it did not change ruminal pH and total volatile fatty acid concentrations. Average duodenal CP flow and quantity of CP apparently digested post‐ruminally was higher (P = 0.001) for CGM‐based diets than SBM‐based diets. There were increases in quantity (P < 0.001) and percentage (P < 0.001) of corn starch digested post‐ruminally compared to barley starch. Synchronized diets showed higher percentages (P = 0.03) of starch apparently digested post‐ruminally than asynchronization. Hanwoo steers fed a corn‐based diet with a large quantity of starch reaching the duodenum and fed C‐CGM supplying great amounts of protein to the small intestine may have contributed to increased post‐ruminal starch digestion.     

Effects of season and inclusion of corn distillers dried grains with solubles in creep feed on intake, microbial protein synthesis and efficiency, ruminal fermentation, digestion, and performance of nursing calves grazing native range in southeastern North Dakota

Nine ruminally and duodenally cannulated (145 +/- 21 kg of initial BW; Exp. 1) and sixteen intact (181 +/- 36 kg of initial BW; Exp. 2), commercial, Angus, nursing, steer calves were used to evaluate the effects of advancing season and corn distillers dried grains with solubles in creep feed on intake, digestion, microbial efficiency, ruminal fermentation, and performance while grazing native rangeland. Calves were assigned to 1 of 2 treatments: a supplement containing 41% soybean meal, 26.25% wheat middlings, 26.25% soybean hulls, 5% molasses, and 1.5% limestone (control) or a supplement containing 50% corn distillers dried grains with solubles, 14.25% wheat middlings, 14.25% soybean hulls, 14% soybean meal, 5% molasses, and 1.5% limestone (CDDGS). Calves were offered supplement individually (0.45% of BW) once daily. Three 15-d collection periods occurred in June, July, and August. In Exp. 1, there were no differences in OM intake, or OM, N, NDF, or ADF digestion between control calves and those fed CDDGS. Forage and total OM intake increased (P < 0.03), whereas OM digestion decreased (P < 0.01), with advancing season. Duodenal microbial N flow (g/d) was not affected (P = 0.50) by treatment and increased linearly (P = 0.003) as season progressed. Calves consuming CDDGS had decreased (P < 0.01) ruminal acetate:propionate ratio, increased (P < 0.01) molar proportion of butyrate, and decreased (P < 0.001) molar proportions of isobutyrate and isovalerate. In Exp. 2, supplement OM intake (% of BW) was less for CDDGS compared with control calves, but there were no differences in performance or subsequent carcass composition between treatments. Inclusion of 50% corn distillers dried grains with solubles in a creep supplement for nursing calves produced similar results compared with a control creep feed based on soybean meal, soybean hulls, and wheat middlings.     

Manipulation of nitrogen digestion by sheep using defaunation and various nitrogen supplementation regimens

Five ruminally, duodenally, and ileally cannulated sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the applicability of using a combination of defaunation with N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) with different extents of ruminal degradation to manipulate microbial protein synthesis and amount of ruminal escape protein. Diets were fed twice daily (1,759 g DM/d). Defaunation was accomplished with 30-ml doses of alkanate 3SL3 (active ingredient: sodium lauryl diethoxy sulfate)/sheep daily for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N (45% of total dietary N) was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM (1:1 N ratio) N:33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation decreased (P less than .05) ruminal ammonia concentration (19 vs 26 mg/dl) and increased (P less than .05) CP flow to the duodenum (253 vs 214 g/d) due to a trend for increases in both bacterial (BCP) and nonbacterial (NBCP) CP flows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fermentation characteristics and ruminal ciliate protozoal populations in cattle fed medium- or high-concentrate barley-based diets

Fermentation characteristics were measured and numbers and distribution by genera of ciliate protozoa were determined in ruminal fluid samples collected from 10 ruminally cannulated steers during the first 30 d of their being fed barley-based diets containing 62% (Medium Barley) or 95% (High Barley) barley grain (DM basis). Ruminal samples were collected at 5-d intervals over the 30-d periods beginning after adaptation (i.e., at the first full feeding of each diet). Ruminal pH and ammonia concentrations were lower (P < 0.001) with the High Barley than with the Medium Barley diet. Concentrations of total VFA and propionate and amylase activity of ruminal fluid were higher (P < 0.001) on High Barley than on Medium Barley. Total protozoal numbers in ruminal fluid were 42% lower (P < 0.05) on High Barley (470 x 10(3)/mL) than on Medium Barley (804 x 10(3)/mL). On Medium and High Barley diets, respectively, Entodinium spp. made up 89 and 91% of the ciliate protozoal populations. With the Medium Barley diet, relative proportions of Dasytricha, Ophryoscolex, Ostracodinium, Diplodinium, and Metadinium spp. in the total ciliate population were 4.5, 0.4, 0.5, 0.7, and 0.3%, respectively. When the High Barley diet was fed, these genera were not detected. In a subsequent survey, ruminal samples were collected from 200 finishing cattle at slaughter. Average protozoal population was 328 x 10(3)/mL, and Entodinium spp. constituted 97% of the total. These data demonstrate that a large population of Entodinium spp. can persist in the rumen of cattle fed high barley grain-based finishing diets.     

Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley-based finishing diets

Four Holstein steers (282 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the influence of dietary urea level (0, 0.4, 0.8, and 1.2%, DM basis) in a steam-flaked barley-based finishing diet on digestive function. There were no treatment effects (P > 0.20) on ruminal digestion of OM and ADF. Increasing dietary urea level increased (linear, P < 0.01) ruminal starch digestion. Ruminal degradability of protein in the basal diet (no supplemental urea) was 60%. Increasing dietary urea level did not increase (P > 0.20) ruminal microbial protein synthesis or nonammonia N flow to the small intestine. There were no treatment effects (P > 0.20) on total-tract ADF digestion. Total tract digestion of OM (quadratic, P < 0.01) and starch (linear, P < 0.05) increased slightly with increasing urea level. Urea supplementation increased (linear, P < 0.01) ruminal pH 1 h after feeding; however, by 3 h after feeding, ruminal pH was lower (cubic, P < 0.05) with urea-supplemented diets. Urea supplementation did not affect (P > 0.20) ruminal molar proportions of acetate and propionate. One hundred twenty crossbred steers (252 kg; approximately 25% Brahman breeding) were used in an 84-d feeding trial (five pens per treatment) to evaluate treatment effects on growth performance. Daily weight gain increased (linear, P = 0.01) with increasing urea level, tending to be maximal (1.53 kg/d; quadratic, P = 0.13) at the 0.8% level of urea supplementation. Improvements in ADG were due to treatment effects (linear, P < 0.01) on DMI. Urea supplementation did not affect (P > 0.20) the NE value of the diet for maintenance and gain. Observed dietary NE values, based on growth performance, were in close agreement with expected based on tabular values for individual feed ingredients, averaging 100.4%. We conclude that with steam-flaked barely-based finishing diets, ruminal and total-tract digestion of OM and ruminal microbial protein synthesis may not be increased by urea supplementation. In contrast, ADG was optimized by dietary inclusion of 0.8% urea. Urea supplementation may not enhance the net energy value of steam-flaked barely-based finishing diets when degradable intake protein is greater than 85% of microbial protein synthesis.     

Effects of nonstructural carbohydrates and protein sources on intake, apparent total tract digestibility, and ruminal metabolism in vivo and in vitro with high-concentrate beef cattle diets

To investigate the effects of synchronizing nonstructural carbohydrate (NSC) and protein degradation on intake and rumen microbial fermentation, four ruminally fistulated Holstein heifers (BW = 132.3 +/- 1.61 kg) fed high-concentrate diets were assigned to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments studied in vivo and in vitro with a dual-flow continuous culture system. Two NSC sources (barley and corn) and 2 protein sources [soybean meal (SBM) and sunflower meal (SFM)] differing in their rate and extent of ruminal degradation were combined resulting in a synchronized rapid fermentation diet (barley-SFM), a synchronized slow fermentation diet (corn-SBM), and 2 unsynchronized diets with a rapidly and a slowly fermenting component (barley-SBM, and corn-SFM). In vitro, the fermentation profile was studied at a constant pH of 6.2, and at a variable pH with 12 h at pH 6.4 and 12 h at pH 5.8. Synchronization tended to result in greater true OM digestion (P = 0.072), VFA concentration (P = 0.067), and microbial N flow (P = 0.092) in vitro, but had no effects on in vivo fermentation pattern or on apparent total tract digestibility. The NSC source affected the efficiency of microbial protein synthesis in vitro, tending to be greater (P = 0.07) for barley-based diets, and in vivo, the NSC source tended to affect intake. Dry matter and OM intake tended to be greater (P > or = 0.06) for corn- than barley-based diets. Ammonia N concentration was lower in vitro (P = 0.006) and tended to be lower in vivo (P = 0.07) for corn- than barley-based diets. In vitro, pH could be reduced from 6.4 to 5.8 for 12 h/d without any effect on ruminal fermentation or microbial protein synthesis. In summary, ruminal synchronization seemed to have positive effects on in vitro fermentation, but in vivo recycling of endogenous N or intake differences could compensate for these effects.     

Effects of concentrated separator by-product (desugared molasses) on intake, site of digestion, microbial efficiency, and nitrogen balance in ruminants fed forage-based diets

In Exp. 1, 4 ruminally and duodenally cannulated beef steers (444.0 +/- 9.8 kg) were used in a 4 x 4 Latin square with a 2 x 2 factorial treatment arrangement to evaluate the effects of forage type (alfalfa or corn stover) and concentrated separator byproduct (CSB) supplementation (0 or 10% of dietary DM) on intake, site of digestion, and microbial efficiency. In Exp. 2, 5 wethers (44 +/- 1.5 kg) were used in a 5 x 5 Latin square to evaluate the effects of CSB on intake, digestion, and N balance. Treatments were 0, 10, and 20% CSB (DM basis) mixed with forage; 10% CSB offered separately from the forage; and a urea control, in which urea was added to the forage at equal N compared with the 10% CSB treatment. In Exp. 1, intakes of OM and N (g/kg of BW) were greater (P < 0.01) for steers fed alfalfa compared with corn stover. Steers fed 10% CSB had greater (P < 0.08) OM and N intakes (g/kg of BW) compared with 0% CSB-fed steers. Total duodenal, microbial, and nonmicrobial flows of OM and N were greater (P < 0.01) for steers fed alfalfa compared with corn stover. Steers fed 10% CSB had increased (P = 0.02) duodenal microbial flow (N and OM) compared with 0% CSB-fed steers. Forage x CSB interactions (P < 0.01) existed for total tract N digestibility; alfalfa with or without CSB was similar (67.4 vs. 69.5), whereas corn stover with CSB was greater than corn stover without CSB (31.9 vs. -23.9%). True ruminal OM digestion was greater (P < 0.09) in steers fed alfalfa vs. corn stover (73.0 vs. 63.1%) and in steers fed 10 vs. 0% CSB (70.3 vs. 65.8%). Microbial efficiency was unaffected (P > 0.25) by forage type or CSB supplementation. In Exp. 2, forage and total intake increased (linear; P < 0.01) as CSB increased and were greater (P < 0.04) in 10% CSB mixed with forage compared with 10% CSB fed separately. Feeding 10% CSB separately resulted in similar DM and OM apparent total tract digestibility compared with 10% CSB fed mixed. Increasing CSB led to an increase (linear; P < 0.02) in DM, OM, apparent N digestion, and water intake. Nitrogen balance (g and percentage of N intake) increased (linear; P < 0.08) with CSB addition. Feeding 10% CSB separately resulted in greater (P < 0.01) N balance compared with 10% CSB fed mixed. Using urea resulted in similar (P = 0.30) N balance compared with 10% CSB fed mixed. Inclusion of CSB improves intake, digestion, and increases microbial N production in ruminants fed forage-based diets.     

Ruminal fermentation and degradation patterns, protozoa population and urinary purine derivatives excretion in goats and wethers fed diets based on olive leaves

Olives leaves, accrued during the processing of olive harvests for oil extraction, are poor in N, rich in crude fat and ADF (1.19, 8.03 and 28.2 g/100 g of DM, respectively), and relatively low in condensed tannins (11.1 mg/g of DM). Three experiments were conducted in a 2 x 3 (two animal species: goats vs. wethers; and three experimental diets: olive leaves without or with polyethylene glycol supply and olive leaves supplemented with barley and faba beans) factorial design to evaluate ruminal degradation and passage kinetics (Exp. 1), fermentation pattern and protozoa population (Exp. 2), and urinary purine derivatives excretion (Exp. 3). Polyethylene glycol was supplied to evaluate the effects of condensed tannins contained in olive leaves. Ruminal degradability of CP was low in both goats and wethers, although goats showed higher (P < 0.05) values than wethers. Supplementation of olive leaves with barley and faba beans increased (P < 0.001) ruminal degradability of DM and CP. Both goats and wethers fed olive leaves showed similarly low particulate fractional passage rates (0.021 and 0.023/h, respectively). Ingestion of olive leaves promoted low NH3-N and VFA concentrations, which reflect poor microbial activity. These concentrations, especially that of VFA, increased when barley and faba beans were added. Ingestion of olive leaves affected ruminal protozoa: Entodiniomorphida showed low concentrations and Holotricha completely disappeared. When animals received a diet based on olive leaves, barley, and faba beans, Holotricha appeared in the ruminal liquor and Entodiniomorphida increased (P < 0.001). In goats and wethers fed olive leaves alone, urinary allantoin excretion was very low (163 and 164 micromol/kg BW0.75 in goats and wethers, respectively), and moderate values (352 and 389 micromol/kg BW0.75 in goats and wethers, respectively) were observed when a diet of olive leaves, barley, and faba beans was fed. The polyethylene glycol supply did not have an effect in goats or in wethers, indicating the lack of an effect of condensed tannins in olive leaves. Ingestion of olive leaves promotes a low microbial activity, although its supplementation with readily degraded carbohydrates and protein improves microbial activity and, as a consequence, increases its ruminal degradation. In general, for most of the measured variables, there were no animal species x diet interactions. Thus, goats and wethers had similar ruminal activities when fed diets based on olive leaves.