Feed intake, digestion and digesta characteristics of cattle fed Bermudagrass or orchardgrass alone or with ground barley or corn

Feed intake, digestion and digesta characteristics of cattle fed bermudagrass (BG) or orchardgrass (OG) alone or with supplemental ground corn or barley were determined in two 6 x 6 latin squares with 2 x 3 factorial treatment arrangements. In Exp. 1, beef cows (Hereford, Angus and Hereford-Angus; 452 kg) cannulated in the rumen and duodenum were fed BG (7.9% CP, 79% NDF and 8.7% ADL) or OG (9.8% CP, 79% NDF and 7.2% ADL) hays at 1.2% of BW per day either alone or with added ground barley (.64% BW) or ground corn (.60% BW daily). The increase in microbial OM flow with corn was greater for OG than for BG; corn elevated microbial OM flow more than did barley with OG but less than with BG (forage type x grain source interaction; P less than .10). The increase in total tract OM digestion with grain was greater for BG than for OG (supplementation effect and forage type x supplementation interaction; P less than 05). In Exp. 2, Holstein steers (228 kg) were fed BG and OG hays ad libitum either alone or with addition of either 1.07% of BW per day of barley or 1.00% BW of corn. Total DM intake was 2.19, 3.03 and 2.82% BW for BG and 2.14, 2.80 and 2.52% BW for OG alone or with barley or corn supplements, respectively, being affected by forage type, grain supplementation, grain type and a forage type x grain supplementation interaction (P less than .05). Organic matter digested daily (g/d) was higher for OG than for BG, higher with than without grain and higher for barley than for corn (P less than .05).     

Comparative utilization of warm- and cool-season forages by cattle, sheep and goats

The quality of different classes of forage hay (C3, C4 grasses and legumes) was determined in intake and digestibility trials with mature cattle, sheep and goats. For all nine hays, DM and NDF digestibility by cattle and goats was higher (P less than .05) than by sheep, with no differences due to forage class. Cattle had a higher (P less than .01) DM intake than sheep or goats averaged across forage (92.6 vs 65.8 and 68.6 g/kg BW.75); hay intake was highest on legume, with no difference between C3 and C4 grasses. Mean NDF intake by cattle was greater than by sheep or goats (58.7 vs 39.6 and 42.6 g/kg BW.75); NDF intake for all animal species decreased in the order C4 grass greater than C3 grass greater than legume. Particle passage rates did not differ (P greater than .05) with forage class but were higher (P less than .02) for sheep and goats than for cattle. Prefeeding ruminal DM fill values, determined by emptying, were 10.6, 15.0 and 19.9 g/kg BW1.0 for alfalfa, orchardgrass and switchgrass hays fed to cattle, and 11.2, 11.3 and 16.5 g/kg BW1.0 for the same hays fed to sheep. Estimated turnover times for DM and NDF were shorter (P less than .05) for sheep than for cattle; DM turnover was longer for switchgrass than for alfalfa and orchardgrass, with no forage differences in NDF turnover between these two animal species. Results show that goats were superior to sheep in NDF digestion.     

Effects of grass maturity and legume substitution on large particle size reduction and small particle flow from the rumen of cattle.

Five ruminally and abomasally cannulated heifers (average weight 365 kg) were fed 6 kg/d of early (EOG) or late (LOG) maturity orchardgrass (OG) hay with or without replacement of EOG or LOG by 1.5 kg/d red clover hay (RC) in a 5 x 5 Latin square design. A fifth treatment, of LOG supplemented with 100 g/d casein (LOG + C), was used to evaluate the effect of supplemental protein. In situ fiber digestion, in vivo nutrient digestion and rate of passage from the rumen of large (retained on a 1.68-mm screen; labeled with La) and small (passed a 1.68-mm screen; labeled with Sm) EOG and LOG particles were determined in heifers fed these diets. Early maturity OG hay had 20% and 62%, respectively, greater (P less than .05) rates, and 61% and 73%, respectively, greater (P less than .05) extents of in situ NDF and ADF disappearance than LOG. Red clover substitution for OG increased (P less than .05) in situ extent of NDF disappearance by 6%. Early maturity OG large and small particles had 40% and 36%, respectively, greater (P less than .05) rates of passage than LOG. Large and small particle ruminal pool sizes were increased (P less than .05) by 115% and 33%, respectively, with LOG. Red clover substitution for OG increased (P less than .10) large and small particle output (kg/d) from the rumen by 15% and large particle rate of passage by 20%. Grass maturity may be affecting intake through rate of large particle size reduction and passage and small particle passage, although legume supplementation of OG may influence intake by increasing rate of large particle size reduction and passage.     

Effect of distillers grains or corn supplementation frequency on forage intake and digestibility

Ten ruminally cannulated heifers (BW = 416 kg; SD = 24) were used to test the effect of the form and frequency of supplemental energy on forage DMI and digestibility. Five treatments were arranged in a replicated, 5 x 4 Latin rectangle (n = 8), and included no supplement (control), dry-rolled corn (DRC) fed daily, DRC fed on alternate days (DRC-A), dried distillers grains plus solubles (DDGS) fed daily, and DDGS fed on alternate days (DDGS-A). Supplements fed daily were fed at 0.40% of BW, whereas alternate day-fed supplements were fed at 0.80% of BW every other day. Chopped grass hay (8.2% CP) was fed to allow ad libitum DMI, and the intake pattern was measured. Control heifers had greater (P < 0.01) hay DMI than supplemented heifers (1.88 vs. 1.66% of BW daily, respectively), although total DMI was lower (P < 0.01) for control. Hay DMI did not differ (P = 0.45) between DRC and DDGS, and tended to be lower (P = 0.08) by heifers on DDGS-A and DRC-A than by heifers supplemented daily. Hay intake was lower (P < 0.01) on supplementation days for DDGS-A and DRC-A than on nonsupplemented days. Heifers in alternate-day treatments had fewer (P < 0.01) and larger (P < 0.01) meals and spent less (P < 0.01) time eating than those supplemented daily. Average rumen pH was greater (P = 0.05) for control than supplemented heifers (6.30 vs. 6.19). Control heifers had greater (P = 0.04) rates and extents of NDF disappearance than supplemented heifers. Rate of hay NDF disappearance was lower (P = 0.02) for DRC than for DDGS. Supplementation decreased hay DMI and changed digestion kinetics. Supplementation frequency affected amount and pattern of DMI. Rate of hay NDF disappearance was greater for DDGS than DRC.     

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 Bermuda grass hay or corn on intake, digestion and performance of cattle consuming endophyte-infected fescue

Effects of supplemental Bermuda grass hay (BG) or ground corn on intake, digestion and performance of cattle consuming endophyte-infected fescue (I) were studied. In Exp. 1, a Latin square study, five growing Holstein steers (158.1 kg) consumed I ad libitum and were offered 0, .3, .6, .9 or 1.2% body weight (BW) of BG daily. Total dry matter (DM) intake rose linearly (P less than .05) with increasing BG, although intake was numerically similar with .6, .9 and 1.2% BW of BG. Digestibility was constant with diet (P greater than .10). Six growing Holstein steers used in Exp. 2, a Latin square with a 2 x 3 factorial arrangement of treatments, ingested I or noninfected (NI) fescue hay ad libitum with 0, .5 or 1.0% BW of ground corn. Total DM intake increased linearly as the level of corn rose (P less than .05). Total intake with I increased more with the first than with the second addition of corn, and the opposite occurred with NI (interaction between fescue infection and the quadratic effect of corn level, P less than .10). Organic matter digested (g/d) was greater for NI than for I and rose linearly with increasing corn ingestion (P less than .05). Ninety-six crossbred beef heifers and steers (184.2 kg avg initial live weight) were used in a 77-d fall grazing experiment (Exp. 3) with a 2 x 3 factorial treatment arrangement. Cattle grazed I or NI paddocks and were given no supplement or .34% BW of BG or .65% BW of ground corn on a daily basis (DM).(ABSTRACT TRUNCATED AT 250 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.     

Intake, digestion, passage rate and serum prolactin in growing dairy steers fed endophyte-infected fescue with noninfected fescue, clover or wheat straw

Growing Holstein steers were used in two Latin-square experiments to determine the effects of supplementation of endophyte-infected fescue hay diets with other forages on intake, digestion, passage rate and serum prolactin concentration. In Exp. 1, five steers (average weight of 186 kg) were fed ad libitum amounts of endophyte-infected and noninfected fescue hays (I and NI, respectively) of similar quality in 0:1, 1:3, 1:1, 3:1 and 1:0 proportions. Total dry matter (DM) intake as a percentage of body weight (BW) linearly decreased .0055% for each 1% increase in dietary I (P less than .05). Dry matter intakes with 100% I and 100% NI diets were 2.13 and 2.72% of BW, respectively. Total tract digestion of neutral detergent fiber (NDF) increased linearly (P less than .05) with increasing I (66.0, 65.9, 66.3, 68.1 and 69.6%). Ruminal passage rate of particulates changed linearly (P less than .05) and quadratically (P less than .10) as I in the diet increased (3.5, 3.4, 2.6, 2.8 and 2.8%/h), while serum prolactin concentration and rectal temperature decreased linearly (P less than .05). In Exp. 2, four steers (average weight of 137 kg) were given ad libitum amounts of wheat straw (WS) or .73% of BW of clover hay (C) at 0800 and free access to either I or NI at 1600. Total intake as a percentage of BW was greatest for C with NI (3.04), intermediate for WS with NI (2.70) and lowest for C with I (2.30) and WS with I (2.23; P less than .05). Fescue intake (percentage of BW) was lowest (P less than .05) for C with I (1.56) and higher (P less than .05) for WS with NI (2.63) than WS with I (2.12); fescue intake for C with NI (2.33) was intermediate (P greater than .10) to WS with NI and WS with I. The results are interpreted to indicate that increasing the dietary level of I depressed intake linearly and markedly. Intake of diets high in I appears to be lower than can be explained only by ruminal-fill factors. When animals that are consuming basal I diets are provided access to nontoxic, high-quality forage, changes in intake may differ from those with basal diets of nontoxic forage.     

Effects of offering different amounts and types of supplemental feeds to growing dairy steers fed endophyte-infected fescue hay ad libitum on intake, digestion, passage rate and serum prolactin concentration

Ten Holstein steers (141 kg) were used in two 5 X 5 Latin-square experiments conducted simultaneously to determine the effects of offering different levels and types of feeds with endophyte-infected fescue given ad libitum. In Exp. 1, steers were given ad libitum access to infected fescue hay in the afternoon; in the morning fescue was given ad libitum (basal) or bermudagrass or clover hays were fed at .5 or 1.0% of body weight (BW). Supplementation did not affect total dry matter intake (P greater than .10), but supplementation at 1.0% of BW yielded total intake greater than supplementation at .5% of BW (P less than .05). Supplementation did not change digestibilities of dry or organic matter (P greater than .10). Particulate passage rate was greater (P less than .10) with supplementation at 1.0 than at .5% of BW, and increasing the level of supplementation from .5 to 1.0% of BW affected fluid passage rate positively with clover but negatively with bermudagrass (interaction, P less than .05). Serum prolactin increased (P less than .05) with all supplementation treatments, although no differences were observed between supplement type-supplementation level combinations (P greater than .10). Ground corn and wheat hay were supplements in Exp. 2. Total intake of dry matter was greater with supplements provided at 1.0 rather than at .5% of BW and for corn rather than wheat hay (P less than .05). Neutral detergent fiber digestion (percent of intake and grams per day) rose when wheat hay was offered at 1.0 vs .5% of BW but declined when the level of supplemental corn increased from .5 to 1.0% of BW (interaction, P less than .05). There were no differences among diets in particulate and fluid passage rates and serum prolactin concentration. Supplementation with nontoxic forage of a basal diet of infected fescue yielded intake substitution when forage was offered at .5% of BW, although incomplete substitution occurred with 1.0% of BW of supplemental forage such that total intake increased as compared to the lower level of supplementation.     

Intake and digestibility of low-quality meadow hay by cattle receiving various levels of whole shelled corn

Two trials were conducted to evaluate the effects of whole shelled corn supplementation on intake and digestibility of low-quality meadow hay by cattle. In Trial 1, four ruminally cannulated steers (avg BW 418 kg) were used in a latin square design with four treatments (no corn or corn fed at .25%, .50% or .75% of BW). Hay DMI decreased (P = .002) linearly .43 g for each gram of increase in corn intake. In contrast, total diet DMI increased (P = .001) linearly as level of corn supplementation increased. Apparent DM digestibility of the diet increased (P = .026) linearly, whereas hay DM digestibility was not affected (P greater than .05) by supplemental corn, although the DM digestion coefficient for hay alone was 24% higher than for hay fed with corn at .75% of BW. Ruminal ammonia concentration and pH were not affected (P greater than .05) by treatments; however, ratio of acetate:propionate and acetate:butyrate responded (P less than or equal to .097) quadratically to increased corn supplementation. Corn supplementation resulted in a cubic (P less than or equal to .081) decrease in meadow hay NDF disappearance from nylon bags suspended in the rumen at all incubation intervals after 4 h. In Trial 2, 45 crossbred, nonlactating, pregnant cows (avg BW 474 kg) were used in a completely randomized design with three treatments (no corn, .91 and 1.81 kg corn.hd-1.d-1). Cow performance was not altered (P greater than .05) by treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of supplemental alfalfa hay on feed intake and digestion by Holstein steers consuming high-quality bermudagrass or orchardgrass hay

Effects of level and frequency of supplementation with alfalfa (A) on feed intake and digestion by steers fed bermudagrass (B) or orchardgrass (O) were determined in two Latin square experiments. In Exp. 1, six Holstein steers (224 kg) were fed B (2.25% N; 71.4% NDF) or O (2.52% N; 64.3% NDF) with 0, 15 or 30% (DM) A (2.70% N; 44.0% NDF). Total DMI was 2.43, 2.72 and 2.85% BW for B and 2.98, 3.00 and 2.87% BW for O with 0, 15 and 30% A, respectively. Total DMI was affected by forage (P less than .05), A level (linear; P less than .06) and a forage x A level (linear) interaction (P less than .05). Digestible OM intake increased .42 (15%) and .67 kg (24%) with feeding of 15 and 30% A, respectively, for B, but for O, only dietary inclusion of 30% A elevated digestible OM intake (.14 kg and 4% increases). In Exp. 2, five Holstein steers (165 kg) were fed B (1.81% N; 78.6% NDF) alone or with A (2.76% N; 52.8% NDF). Morning meals consisted of ad libitum B (OA), .3% BW of A daily (.3A), .6% BW of A every 2nd d (.6A), .9% BW of A every 3rd d (.9A) or 1.2% BW of A every 4th d (1.2A). All steers received B in the afternoon ad libitum, and B was given in the morning when A was not fed. Total DMI was 2.31, 2.12, 2.12, 2.26 and 2.29% BW for OA, .3A, .6A, .9A and 1.2A, respectively (SE .049). Grass characteristics affected response in feed intake to legume supplementation. Frequency of dietary legume addition may alter feed intake.     

Effects of buffer or DL-methionine with different amounts of supplemental corn on feed intake and nutrient digestion by Holstein steers consuming bermudagrass hay

Two latin squares were conducted to determine the effects on feed intake and nutrient digestion of adding a ruminal buffer or DL-methionine to supplemental ground corn for Holstein steers (avg BW of 286 and 222 kg in Exp. 1 and 2, respectively) with ad libitum access to bermudagrass hay. In Exp. 1, steers were not supplemented (control) or were given .5 (LC) or 1.0% BW/d (HC) of ground corn without or with .021% BW of sodium bicarbonate (B). Total DMI was 2.39, 2.71, 2.79, 2.81 and 2.98% BW (effects of supplementation [P less than .05], level of corn [P less than .05] and buffer [P less than .06]), and OM digested was 3.56, 4.65, 4.65, 4.96 and 5.34 kg/d for control, LC, LCB, HC and HCB, respectively (effects of supplementation and corn level, P less than .05). In Exp. 2, corn levels were .24 and .74% BW/d and .0022% BW of DL-methionine (M) replaced B. Total DMI was 2.85, 3.00, 2.99, 3.22 and 3.34% BW (effects of supplementation and corn level, P less than .05), and digestible OM intake was 3.78, 4.24, 4.30, 4.84 and 5.12 kg/d for control, LC, LCM, HC and HCM, respectively (effects of supplementation and corn level, P less than .05). Overall, changes in feed intake and digestion with additions of a ruminal buffer and DL-methionine to corn supplements were not marked; however, buffer addition increased DMI intake to the greatest degree with 1.0% BW/d of corn.     

Intake, digestion, and N metabolism in steers fed endophyte-free, ergot alkaloid-producing endophyte-infected, or nonergot alkaloid-producing endophyte-infected fescue hay

A digestion and N balance trial was conducted to compare effects of traditional endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte infected (NE; MaxQ; Pennington Seed, Inc., Madison, GA) Jesup tall fescue (Festuca arundinacea Schreb.) hay on digestion and N retention in steers. Hay composition (DM basis) was as follows: E+ (10.8% CP, 59.9% NDF, and 29.4% ADF), E- (11.8% CP, 58.5% NDF, and 28.4% ADF), and NE (11.6% CP, 58.6% NDF, and 28.3% ADF). Eight Polled Hereford steers (initial BW 240 +/- 9 kg) were used in a replicated, 3 x 3 Latin square design, with an extra steer allotted to each square. Steers were fed ad libitum for 14 d, followed by a 9-d adaptation to restricted intake (based on the animal with the lowest ad libitum intake for the square) and a 5-d fecal and urine collection. Water intake (20.2 L/d) and urine output (7.40 L/d) did not differ (P > 0.10) during the collection period. Plasma prolactin concentration was less (P < 0.05) for steers on the E+ hay (8.83 ng/mL) than for those on the E- hay (18.03 ng/mL) and intermediate for steers on the NE hay (12.65 ng/mL). Endophyte-infected hay differed (P < 0.05) from E- and NE in ad libitum DMI (5.02 vs. 5.62 and 5.61 kg/d, respectively) and ad libitum DMI as a percentage of BW (1.86 vs. 2.06 and 2.06%, respectively). Restricted DMI during the fecal and urine collection was lower (P < 0.05) for E+ hay than for E- (5.04 vs. 5.24 kg/d), and NE was intermediate (5.19 kg/d). Dry matter digestibility was lower (P < 0.05) for E+ compared with E- and NE (62.3 vs. 67.0 and 65.9%, respectively). Digestibility of ADF was lower (P < 0.05) for E+ than for E-, and was intermediate for NE (61.5, 66.0, and 63.9%, respectively). There were no differences for NDF, cellulose, or hemicellulose digestibilities among hay types. Crude protein digestibility was higher (P < 0.05) for E- and NE than for E+ (54.3 and 52.5 vs. 48.1%, respectively). Nitrogen retention was lower (P < 0.01) for E+ than for E- or NE (15.6 vs. 22.7 or 23.0 g/d, respectively). Hay type did not influence plasma urea N, urine urea N output, or urine urea N as a percentage of urinary N. Results from this study indicate that E+ tall fescue hay was lower in ad libitum DMI, DM digestibility, and N retention than NE or E- hays with similar chemical composition. Hay from NE and E- fescue had nearly identical composition, and did not differ for any variable measured.     

Effect of ruminal vs postruminal administration of degradable protein on utilization of low-quality forage by beef steers

An experiment was designed to determine the effects of ruminal and postruminal infusions of ruminally degradable protein (casein) on intake and digestion of low-quality hay by beef steers. Twelve ruminally fistulated Angus x Hereford steers (initial BW = 563 kg) were blocked by weight and assigned to one of three treatments: control (C; hay only) or hay plus ruminal (R) or postruminal (P) infusion of 400 g/d of sodium caseinate. The trial consisted of five periods: 1) 10-d adaptation to the hay diet; 2) 7-d measurement of hay intake (without infusions); 3) 10-d adaptation to protein infusion treatments (intake measurements continued); 4) 7-d measurement of hay intake and digestibility (infusions continued); and 5) 3-d ruminal sampling period (infusions continued). Steers were given ad libitum access to tallgrass-prairie hay (3.4% CP, 76.6% NDF) throughout the study. Casein was administered once daily before feeding, either directly into the rumen or via anchored infusion lines into the abomasum. Hay intake was increased by supplementation (P < 0.01). Ruminal infusion elicited a greater (P = 0.04) increase in hay intake than postruminal infusion. Intake tended (P = 0.11) to be lower in period 4 than in period 2 for control steers but was greater in period 4 than in period 2 (P < or = 0.03) for both R and P steers. The increase in intake between periods 2 and 4 was greater for R than for P steers (P = 0.03). Supplementation improved diet OM digestion (P = 0.04) but not NDF digestion (P = 0.18); however, greater relative error for NDF digestion may have limited the ability to elucidate significant treatment effects. There were no differences in either OM digestion (P = 0.42) or NDF digestion (P = 0.35) between R and P steers. Plasma urea N at 0 and 3 h after feeding on the last day of the experiment was lower (P = 0.05) for C than for R and P steers, but no difference (P = 0.48) was evident between R and P steers. Ruminal ammonia N levels also were increased by supplementation (P < 0.01), with a much larger increase for R than for P steers (P < 0.01). Total VFA concentrations were not affected (P = 0.21) by treatment, but R steers exhibited lower proportions of acetate and higher proportions of isobutyrate, valerate, and isovalerate than P steers (P < 0.01). In conclusion, ruminal and postruminal infusion of a degradable protein source improved forage utilization, although the response in forage OM intake and total digestible OM intake was greater for ruminal infusion than for postruminal infusion.     

Effect of intake level and alfalfa substitution for grass hay on ruminal kinetics of fiber digestion and particle passage in beef cattle

Two experiments were conducted to evaluate digestion kinetics of alfalfa (Medicago sativa L.) substitution for grass hay in beef cattle. In Exp. 1, forage combinations evaluated in situ consisted of 0% alfalfa-100% big bluestem (Andropogon gerardi Vitman), 25% alfalfa-75% big bluestem, 50% alfalfa-50% big bluestem, and 100% alfalfa-0% big bluestem. Nonlinear regression was used to determine the immediately soluble fraction A, the potentially degradable fraction B, the undegraded fraction C, and the disappearance rate of DM and NDF. Dry matter fraction A increased linearly (P = 0.03), and DM and NDF fraction B decreased linearly (P = 0.01) with increasing alfalfa substitution. Rate of DM and NDF disappearance increased linearly (P /= 0.23) on total tract apparent digestibility of all nutrients except CP. Steers fed orchardgrass plus alfalfa had 33% greater (P = 0.01) total tract apparent digestibility for CP than those fed orchardgrass alone. Lag time of DM and NDF disappearance was not affected (P >/= 0.20) by alfalfa supplementation or intake level. Rate of DM and NDF disappearance of orchardgrass was faster (P 相似文献   

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.     

Relationship between body weight and level of fat supplementation on fatty acid digestion in feedlot cattle

Eight Holstein steers with cannulas in the rumen and proximal duodenum were used in a split-plot design experiment to evaluate the interaction of body weight (175 vs. 370 kg) and level of fat supplementation (0, 3, 6, and 9% yellow grease) on characteristics of digestion and feeding value of fat in finishing diets. Dry matter intake was restricted to 2% of BW. There were no interactions between BW and level of fat supplementation (P > 0.10) on ruminal or total-tract digestion. Level of supplemental fat decreased (linear, P < 0.01) ruminal digestion of OM and NDF, and increased (linear, P < 0.05) ruminal N efficiency. There were no treatment effects (P > 0.10) on postruminal digestion of OM, NDF, and N. There tended to be an interaction (P < 0.10) between BW and level of fat supplementation on postruminal starch digestion. Increasing level of fat supplementation increased postruminal digestion of starch in heavier steers but did not affect starch digestion in lighter steers. There were no interactions (P > 0.10) between BW and level of fat supplementation on postruminal fatty acid digestion. Increasing level of fat supplementation decreased (linear, P < 0.01) postruminal fatty acid digestion, which was due to a decreased (linear, P < 0.01) postruminal digestion of C16:0 and C18:0. Supplemental fat decreased (linear, P < 0.01) total-tract digestion of OM and NDF. The estimated NEm (Mcal/kg) of yellow grease averaged (linear, P < 0.01) 6.02, 5.70, and 5.06 for the 3, 6, and 9% of level supplementation, respectively. We conclude that intestinal fatty acid digestion (FAD, %) is a predictable function (r2 = 0.89; P < 0.01) of total fatty acid intake per unit body weight (FAI, g/kg BW): FAD = 87.560 - 8.591FAI. Depressions in fatty acid digestion with increasing level of intake were due primarily to decreased intestinal absorption of palmitic and stearic acid. Level of fatty acids intake did not appreciably affect intestinal absorption of unsaturated fatty acid. Changes in intestinal fatty acid digestion accounted for most of the variation in the NE value of supplemental fat.     

Intake of direct cut or wilted grass silage as related to chewing behavior, ruminal characteristics and site and extent of digestion by heifers

Six nonpregnant Friesian heifers (516 kg avg BW) with ruminal and duodenal cannulas were used to examine intake of direct cut (DC) or wilted (W) grass silage in relation to chewing behavior, ruminal characteristics and site and extent of digestion. Dry matter content of the silages was 20.3% and 40.3%, and feed intake averaged 1.88% and 2.17% of BW (P less than .01), respectively. Mean ruminal osmolality was 291 mosm/liter for the DC and 318 mosm/liter for the W silage (P less than .05), with extreme values exceeding 350 mosm/liter for the W silage at 1 h to 2 h postfeeding. There was a shift from eating to ruminating on W silage associated with a longer duration of the average rumination bolus cycle (P less than .01). Duration of chewing time per kilogram of DM intake was 103.5 min and 91.7 min (P less than .05) for the DC and W silages, respectively. Fecal mean particle length was 2.2 times greater (P less than .01), accompanied by higher spread coefficients (P less than .001), for the W silage. No differences occurred between silages in ruminal digestibility of OM and NDF. In the total digestive tract, apparent digestibilities of OM and NDF were depressed after wilting grass prior to ensiling (P less than .01), but the proportion of digestible OM apparently digested in the rumen was .74 for both silages.(ABSTRACT TRUNCATED AT 250 WORDS)     

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)     

Effects of source and level of dietary neutral detergent fiber on feed intake, ruminal fermentation, ruminal digestion in situ, and total tract digestion in beef cattle fed pelleted concentrates with or without supplemental roughage.

The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.