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1.
An intake and digestibility study was conducted with three groups (six animals per group) of yearling wether dairy goats (four Toggenburg, two Alpine), wool sheep (Targhee X Dorset) and hair sheep (St. Croix). Body weight (BW) ranged from 42 to 52 kg, averaging 47 kg. All animals were penned individually and given ad libitum access to a mixture of alfalfa-smooth bromegrass hay in pelleted, chopped or long form. Each group contained three ruminally cannulated animals. There were no apparent differences in the composition of feed consumed among goats, wool sheep and hair sheep, and no significant animal type X forage form interactions for any of the variables evaluated. Significant differences were observed in dry matter intake (DMI) between wool sheep, hair sheep and goats: 3.17%, 2.66% and 2.23% of BW, respectively (P less than .05). Daily water intake (WI) was greatest for wool sheep (P less than .05), but not different between hair sheep and goats. Total digestibility of dry matter (DM) and all fiber fractions were similar among animal types. For the cannulated animals, ruminal content weight and total ruminal volume were greatest for wool sheep (P less than .05). Ruminal acid detergent lignin (ADL) turnover was greater in wool and hair sheep than goats (P less than .05), but no differences were apparent for dry matter or neutral detergent fiber (NDF) turnover. For all animals, DMI, DMI/BW, digestible DMI and WI were greater for pelleted than chopped and long hay (P less than .05). Total ruminal volume, contents weight (on an absolute or BW basis) and fluid volume were lower in the cannulated animals consuming pelleted hay (P less than .05). Ruminal DM turnover rate was faster on pelleted than long hay, while DM turnover rate on chopped hay was intermediate. Turnover of ADL was faster on pelleted than chopped or long hay (P less than .05), but there were no differences among forage forms in NDF turnover rate. Fluid turnover rate was faster on pelleted and chopped than on long hay (P less than .05). Under the conditions of this study, no apparent differences were observed among animal types in the nutrient composition of feed consumed, ruminal or total tract digestibilities or rate of passage for dry matter. However, feeding behavior or selectivity differences under natural grazing conditions may deviate from what has been observed in confinement.  相似文献   

2.
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).  相似文献   

3.
The preference exhibited by animals in selecting one feed over another is important only if the preferred diet is consumed daily in larger quantities, digested to a greater extent, or both. Six alfalfa (Medicago sativa L.) hays were harvested in pairs at sunset (PM) and sunrise (AM) on consecutive days at three harvest dates. A previous study of these hays demonstrated differences in ruminant preference favoring PM harvests. This study evaluated the effects of time of cutting and harvest date on voluntary DMI and nutrient digestibility. The hays were field-cured, baled, and chopped before evaluation for intake and digestibility. Studies were conducted for sheep (Ovis aries), goats (Capra hircus), and cattle (Bos taurus). Goats, but not steers or sheep, demonstrated differences in nutrient digestibility between PM- and AM-cut hays. Goats consumed more PM than AM hay (2.97 vs. 2.83 kg/100 kg of BW; P = 0.07) and digested it to a greater extent (0.710 vs. 0.696; P = 0.03), resulting in greater digestible DMI (2.11 vs. 1.97 kg/100 kg of BW; P = 0.03). Sheep consumed (mean = 2.52 kg/100 kg of BW; P = 0.59) and digested (mean = 0.681; P = 0.25) PM- and AM-cut hays similarly. Steers consumed larger quantities of PM-than AM-cut hay (2.90 vs. 2.62 kg/100 kg of BW; P = 0.11), but digestion did not differ with cutting time (mean = 0.660; P = 0.75). Difference values (composition of fed hay minus composition of orts) indicated that sheep and goats selected from the feed offered similarly, whereas steers selected differently. Difference values for CP averaged 94 and 101 g/kg for goats and sheep and 32 g/kg for steers (P < 0.01), and difference values for NDF averaged 185 and 196 g/kg for goats and sheep and 73 g/kg for steers (P 相似文献   

4.
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   

5.
This study examined how different methods of applying a fibrolytic enzyme or ammonia affect the nutritive value of Bermudagrass hay and the performance of beef cattle. Fifty Angus x Brangus crossbred steers (mean initial BW 244 +/- 26 kg) were individually fed for ad libitum intake of a 5-wk regrowth of a mixture of Florakirk and Tifton 44 Bermudagrass [Cynodon dactylon (L.) Pers] hay for 84 d with a concentrate supplement (77% soybean hull pellets, 23% cottonseed meal (DM basis) fed at 1% of BW daily. The Bermudagrass was conserved as hay without treatment (control), with NH(3) (30 g/kg of DM), or with a fibrolytic enzyme (16.5 g/t, air-dry basis) that was applied immediately after cutting (Ec), at baling (Eb), or at feeding. Chromic oxide was dosed to steers for 10 consecutive days, and fecal Cr concentrations from the last 5 d were used to estimate apparent total tract digestibility. In situ ruminal DM degradability was measured by incubating ground (4-mm) hay samples in duplicate in each of 2 ruminally cannulated cows having ad libitum access to Bermudagrass hay and 500 g/d of soybean meal. Unlike the enzyme treatment, ammoniation increased (P < 0.001) the CP concentration and reduced (P < 0.001) NDF, hemicellulose, and lignin concentrations of hay. Total DMI was greater (P < 0.05) for steers fed hays treated with Ec or NH(3) than for those fed control hays. All additive treatments increased (P < 0.05) DM digestibility, and NH(3), Ec, and Eb treatments also increased (P < 0.01) NDF digestibility. The initial and final BW, ADG, BCS, G:F, and hip height of the steers were not affected (P > 0.05) by treatment. The wash loss fractions in hays treated with Ec and Eb were lower than that in the control hay, but the potentially degradable fraction, total degradable fraction, and the effective degradability were increased (P < 0.01) by NH(3) treatment. Application at cutting was the most promising method of enzyme treatment, and this treatment was almost as effective as ammonia for enhancing forage quality.  相似文献   

6.
Intake and digestion in cattle fed warm- or cool-season grass hay with or without low-level grain supplementation were studied with a 2 x 2 factorial arrangement of treatments in two 4 x 4 Latin square experiments. In Exp. 1, four cannulated beef cows (396 kg) were given Bermuda grass (B) or orchard grass (OG) hay at 1.5% body weight (BW) with 0 or .3% BW of ground corn (C; dry matter). Bermuda grass contained 12.1% crude protein, 79.3% neutral detergent fiber (NDF) and 5.5% acid detergent lignin (ADL); OG contained 10.6% crude protein, 82.4% NDF and 8.1% ADL. An interaction (P less than .07) between forage type and C supplementation was noted for microbial N entering the duodenum; C supplementation had a positive effect with B (30% increase) and little effect with OG. Corn supplementation did not affect ruminal NDF digestion with B, but it elicited an increase with OG (interaction, P less than .05; means were 60.7, 60.1, 61.5 and 66.3%). In the second experiment, growing dairy steers (196 kg) were given ad libitum access to similar B or OG hays and were fed 0 or .5% BW of C. Dry matter (DM) intake was lower for OG than for B (P less than .05) and was lower with than without C (P less than .06; means were 2.76, 2.56, 2.53 and 2.30% BW for B, BC, OG and OGC, respectively). Total tract organic matter digestion (%) was higher for OG than for B (P less than .10) and was higher with than without C (means were 54.7, 61.5, 60.4 and 65.3%). In conclusion, chemical constituents such as NDF may govern differences in intake between warm- and cool-season grasses, but physical attributes of the forages appear more important to digestion.  相似文献   

7.
Southern crabgrass (Digitaria ciliaris [Retz.] Koel.) is often viewed as an undesirable weed, largely because it encroaches upon field and forage crops, gardens, and lawns. However, visual observations of livestock grazing mixed-species pastures suggest that cattle seem to prefer crabgrass to many other summer forages. The objectives of this study were to assess the nutritive value of crabgrass sampled weekly between July 11, and August 22, 2001, and then to determine ruminal in situ disappearance kinetics of DM and NDF for these crabgrass forages. A secondary objective was to compare these kinetic estimates with those of alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon [L.] Pers.), and orchardgrass (Dactylis glomerata L.) control hays. All forages were evaluated in situ using five (383 +/- 22.7 kg) ruminally cannulated crossbred (Gelbvieh x Angus x Brangus) steers. Whole-plant crabgrass exhibited more rapid (P < or = 0.002) ruminal disappearance rates of DM (overall range = 0.069 to 0.084 h(-1)) than did bermudagrass (0.054 h(-1)) and orchardgrass (0.060 h(-1)) hays, but disappearance rates were slower (P < 0.001) for crabgrass than for alfalfa hay (0.143 h(-1)). Effective ruminal disappearance of DM was greater (P < 0.001) for crabgrass (overall range = 69.3 to 75.4%) than for all the control hays. Similarly, disappearance rates of NDF for crabgrass (overall range = 0.069 to 0.086 h(-1)) were more rapid (P < 0.001) than observed for bermudagrass and orchardgrass hays; however, NDF in alfalfa disappeared at a faster (P < 0.001) rate (0.107 h(-1)) than crabgrass. These results indicate that crabgrass offers greater effective ruminal degradability of DM and NDF than orchardgrass or alfalfa of moderate quality. More importantly, it potentially offers faster and more extensive ruminal disappearance than perennial warm-season grasses typically found throughout the southeastern United States, and it should likely support improved performance by ruminant livestock in this region.  相似文献   

8.
Feeding and palatability trials were conducted with four cultivars (cv) of switchgrass (Panicum virgatum L.), fertilized at three levels of N (0, 75, or 150 kg of N/ha) in 2 yr. Wether sheep had ad libitum access to chopped hays, and intake, apparent digestibility, particle passage rates, and concentrations of blood metabolites were determined. Palatability was measured with mature sheep in cafeteria trials. Nitrogen fertilization did not affect (P > .05) DM digestibility (DMD) or DMI, but there was a year x N interaction (P < .01) for NDF digestibility. Dry matter digestibility values for combined years and N levels were 56.9, 54.4, 56.6, and 57.9% (P < .01) for Pathfinder, New Jersey 50, Kentucky 1625, and Trailblazer cv, respectively; mean DMI values were 60.4, 60.8, 57.7, and 64.0 g/kg BW.75 (year x cv, P < .01). An apparently greater quality of Trailblazer was masked by weed invasion of N-fertilized stands of this cv in yr 2, with changes in hay composition. Lambs adapted to hay diets with time; mean DMI for cv and N levels combined increased (P < .001) from 50.5 to 71.4 g/kg BW.75 between wk 2 and 3 and wk 10 and 11, with no change in DMD. Intakes of NDF increased from 37.6 to 55.6 g/kg BW.75, an increase of 48%. Marker (Yb) measurements indicated little change in particle passage rates with treatment. There were no major differences in blood composition, apart from increases in blood urea N, as a result of N fertilization. Cafeteria trials showed preference by sheep for Trailblazer and KY 1625 compared with NJ 50 and Pathfinder, with a N x cv interaction (P < .01). Trailblazer was preferred to KY 1625 in a two-choice situation (P < .01). Results show relatively small effects of cv and N fertilization on quality of switchgrass and indicate the need for a lengthy period of adaptation by sheep to the feeding of a warm-season grass.  相似文献   

9.
Formaldehyde- and formic acid-treated alfalfa or orchardgrass silage were fed at 65 and 90 g DM/kg BW.75.d) to growing Holstein steers (209 +/- SE = 35 kg) fitted with permanent ruminal and duodenal cannulas in a 4 x 4 latin square. Alfalfa had higher (P less than .01) concentrations of cell solubles, total N and rumen-soluble N than did orchardgrass. Digestible energy (Mcal/d), total N and soluble N intake (g/d) were higher (P less than .05) for steers fed alfalfa than for those fed orchardgrass. Total duodenal OM, DM, NDF, N and non-NH3-N flows were greater (P less than .001) for steers fed alfalfa than for those fed orchardgrass and were greater (P less than .001) at high vs low intake. Duodenal bacterial N flow (g/d) was greater (P less than .001) for steers fed alfalfa than for those fed orchardgrass, and bacterial N synthesis (g/kg DM truly digested in the rumen) was 58 and 32, respectively (P less than .001). Ruminal concentrations of NH3-N (P less than .001) and VFA (P less than .05) were greater for steers fed alfalfa than for those fed orchardgrass. Total tract DM, energy and N digestibilities were higher (P less than .05) for steers fed alfalfa vs orchardgrass, whereas total tract NDF digestibility was lower (P less than .01). Tissue N retention tended to be greater (P less than .1) for steers fed alfalfa than for those fed orchardgrass. Regression analysis indicated that duodenal non-NH3-N flow was related to intake of metabolizable energy and soluble N (R2 = .939). Improved performance and higher efficiency of use of ME for tissue gain by steers fed alfalfa rather than orchardgrass is related to lower ruminal acetate:propionate, higher microbial efficiency and greater duodenal DM and N flows.  相似文献   

10.
A database was compiled to determine the nutrient composition, variability, and nutrient deficiencies of 11,592 forage samples (10,246 hay, 1,001 pasture, and 345 silage) collected from 1985 to 1999. Samples were analyzed for 1 to 15 nutrients: DM, N, ADF, NDF, P, K, Ca, Mg, Na, S, Fe, Mn, Zn, Cu, and Se. Mean (±SD) CP and TDN levels (% DM) of bermudagrass, fescue, and mixed grass (blends of bermudagrass, fescue, orchardgrass, ryegrass, and cheat) hays were 12.4 ± 3.5, 60.0± 6.2; 11.2± 3.0, 53.8± 4.7; and 11.1 ± 3.1, 52.9± 4.7, respectively. For beef cows and calves, TDN was deficient in a greater percentage of hays (P < 0.05) than was CP. Bermudagrass hays contained greater levels of CP and TDN than fescue or mixed grass hays (P < 0.05). Fescue and mixed grass hays did not differ (P > 0.05) in CP, ADF, NDF, or TDN concentrations. Only 6 to 10% of the hays analyzed for Na contained adequate levels for beef cows and calves. Selenium, Cu, and Zn were deficient in 62, 52, and 41% of the hay samples, respectively. For lactating beef cows, a lesser percentage of the hays were deficient in P (16%), Ca (7%), Mg (30%), and S (8%). Iron, Mn, and K were deficient in 2% or less of the hays. Bermudagrass, corn, and sorghum-sudan silages contained greater (P < 0.05) levels of TDN than silages composed of fescue, mixed grass, ryegrass, sorghum silage types, or wheat. With the exception of bluestems and orchardgrass, the pasture samples contained greater concentrations of CP and TDN than the same forage species harvested as hay. In general, forages were highly variable in nutrient content, and most hays were deficient in one or more nutrients for beef cattle.  相似文献   

11.
Holstein steers (112 to 258 kg BW) were fed diets high in endophyte-infected fescue (80 to 100%) in 15 latin square experiments to determine the relationships among BW, forage composition, voluntary consumption and digestion. Fescue DM intake (kg/d) increased linearly (P less than .05) with increasing BW (-.513 + .0275 BW; R2 = .69). Regressing log fescue intake (DM) on log BW resulted in a BW exponent of 1.1034 (R2 = .66) but did not account for any more variation in intake than the simple regression did. The percentage NDF in fescue was not related (P greater than .10) to fescue intake (kg/d) and was correlated only slightly with fescue intake as a percentage of BW (r = -.13; P less than .10). Adding the percentage of fescue in the diet or NDF in the fescue to the regression of DM intake on BW did not increase explained variation. Organic matter intake (kg) and digestibility (%) were not related (P greater than .10). Based on standardized partial regression coefficients, differences in voluntary intake accounted for 60% of the variation in the total quantity of OM digested, whereas differences in digestibility accounted for 40%. In conclusion, ingestibility of endophyte-infected fescue hay in relation to changing BW did not vary greatly. Concentrations of chemical constituents such as NDF and ADL in fescue were poorly correlated with feed consumption and digestibility.  相似文献   

12.
Thirty-two wethers were used to compare the nutritive value of Climax timothy (Phleum pratense L.) and quackgrass (Agropyron repens L. Beauv.) harvested at two stages of maturity, joint and early heading, and fed as hay. Crude protein was higher for quackgrass than for timothy (P less than .01). As maturity advanced, CP decreased (P less than .01), but NDF and ADL increased (P less than .01). Dry matter intake was similar between species but decreased by 8% with increasing maturity (P less than .01). Intake of NDF (g/kg.75) was similar for all hays. With increasing plant maturity, apparent digestibility decreased, the effect being more pronounced for quackgrass. Apparent digestibilities of DM and energy were slightly higher (P less than .06) for timothy, and those of CP and hemicellulose were higher for quackgrass (P less than .01). Apparent digestibilities of NDF, ADF, ADL, crude fiber and cellulose were similar between species. Dry matter intake and digestibility were correlated negatively with the ADL/ADF ratio of the hay (r = -.99, P less than .01), whereas CP intake and CP digestibility were correlated with CP of the hay (r = .99, P less than .01). The Lucas test estimated true protein digestibility at 88.1% and metabolic fecal protein at 29.4 g per kg of DM intake. During the growth trial, DM intake was similar between hays, but ADG of sheep was lower (P less than .01) for those fed hays at early heading vs those receiving hays at the joint stage of maturity. The feed to gain ratio was slightly lower for hays at joint (P less than .08). Under the climatic conditions of the 1988 growing season, the nutritive value of quackgrass was similar to that of Climax timothy.  相似文献   

13.
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)  相似文献   

14.
This experiment was carried out to study the effect of a directly fed exogenous fibrolytic enzyme on intake and digestion of DM, OM, protein, NDF, ADF, and hemicellulose of alfalfa and ryegrass hay by sheep. Four diets were randomly assigned to four ruminally cannulated lambs using a 4 x 4 Latin square design, repeated in time, with a factorial arrangement (2 x 2) of diets: 1) alfalfa hay; 2) alfalfa hay + exogenous fibrolytic enzymes (enzyme); 3) ryegrass hay; and 4) ryegrass hay + enzyme. Lambs consumed more DM and OM from alfalfa than from ryegrass hay (P < 0.001). The ADF intake was not different between the hays, but NDF intake was lower for alfalfa (P < 0.001). For both hays, the enzyme increased intake of DM (P < 0.01), as well as OM and CP (P < 0.05); however, NDF and ADF intake were not changed. Alfalfa hay had higher apparent digestibility of DM, OM, and CP (P < 0.001), but lower digestibility for NDF, ADF, and hemicellulose. The enzyme increased apparent digestibility of CP, hemicellulose (P < 0.05), and NDF (P < 0.10) for alfalfa. Also, for both hays, the enzyme improved N balance because lambs retained more N (P < 0.05). The enzyme increased (P < 0.05) total VFA concentration (3 and 6 h) for both hays. Results from this trial indicate that directly fed exogenous fibrolytic enzymes may change ruminal fermentation, intake, and digestibility of forages with different nutritive value.  相似文献   

15.
Six year-round, all-forage, three-paddock systems for beef cow-calf production were used to produce five calf crops during a 6-yr period. Forages grazed by cows during spring, summer, and early fall consisted of one paddock of 1) tall fescue (Festuca arundinacea Schreb.)-ladino clover (Trifolium repens L.) or 2) Kentucky blue-grass (Poa pratensis L.)-white clover (Trifolium repens L.). Each of these forage mixtures was combined in a factorial arrangement with two paddocks of either 1) fescue-red clover (Trifolium pratense L.), 2) orchardgrass (Dactylis glomerata L.)-red clover, or 3) orchardgrass-alfalfa (Medicago sativa L.), which were used for hay, creep grazing by calves, and stockpiling for grazing by cows in late fall and winter. Each of the six systems included two replications; each replicate contained 5.8 ha and was grazed by eight Angus cow-calf pairs for a total of 480 cow-calf pairs. Fescue was less than 5% infected with Acremonium coenophialum. Pregnancy rate was 94%. Cows grazing fescue-ladino clover maintained greater (P less than .05) BW than those grazing bluegrass-white clover, and their calves tended (P less than .09) to have slightly greater weaning weights (250 vs 243 kg, respectively). Stockpiled fescue-red clover provided more (P less than .05) grazing days and required less (P less than .05) hay fed to cows than stockpiled orchardgrass plus either red clover or alfalfa. Digestibilities of DM, CP, and ADF, determined with steers, were greater (P less than .05) for the orchardgrass-legume hays than for the fescue-red clover hay. All systems produced satisfactory cattle performance, but fescue-ladino clover combined with fescue-red clover required minimum inputs of harvested feed and maintained excellent stands during 6 yr.  相似文献   

16.
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.  相似文献   

17.
Two experiments were conducted to determine some of the factors that led to hypomagnesemic tetany associated with the feeding of two orchardgrass hays. Sixteen mature Columbia and Suffolk wethers (62 to 72 kg), four of which were fitted with ruminal and abomasal cannulae, were fed one of two tetany-prone orchardgrass hays or a non-tetany-prone bromegrass hay. In Exp. 1, 12 wethers were used in a completely random design metabolism experiment to measure apparent absorption and retention of macrominerals. In Exp. 2, four wethers with ruminal and abomasal cannulae were used in a completely random design experiment to monitor pre-intestinal mineral absorption and ruminal characteristics. This experiment was replicated once, with wethers remaining on their diets for 16 d in each replication. In the metabolism experiment, apparent absorption and retention of Mg as a percentage of intake were lower (P less than .01 and P less than .05) for one tetany-prone orchardgrass hay compared with the other orchardgrass hay. Pre-intestinal absorption of Mg in the cannulated wethers was greater (P less than .01) for the orchardgrass hays than for the bromegrass hay. Pre-intestinal Mg absorption was higher (P less than .01), both in terms of grams per day and a percentage of intake for the orchardgrass hay with the highest Mg content. In the noncannulated wethers, the percentage of water-soluble Mg in the feces was lower (P less than .01) for the tetany-prone hays, indicating that a decrease in Mg solubility in the intestine may have influenced Mg apparent absorption.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.
Plants vary diurnally in concentrations of nonstructural carbohydrates. If ruminants prefer forages with higher total nonstructural carbohydrates (TNC), then the preference for hays harvested within the same 24-h period may vary. An established field of tall fescue (Festuca arundinacea Schreb.) was harvested six times in the vegetative stage. Harvests were paired such that each cutting at sundown (PM) was followed by a cutting the next morning at sunup (AM). We harvested in this manner three times, resulting in six hays. The hays were field-dried, baled, and passed through a hydraulic bale processor prior to feeding. Experiments were conducted with sheep, goats, and cattle, using six animals in each case. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (15 pairs) was presented for a meal. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on a single criterion. Preference for PM hays was greater than for AM hays (P < .01) in all experiments. Increased preference was associated with increased TNC (P < .01) and in vitro true DM disappearance (P < .01) and decreased fiber concentration (P < .01; NDF, ADF, cellulose, and ADL). Mowing hay late in the day was effective in increasing forage preference.  相似文献   

19.
Four rumen fistulated wether and beef steers were used to evaluate differences in dry matter digestibility (DMD) between cattle and sheep. They were fed either perennial ryegrass or switchgrass hay at an ad libitum or restricted level for four experimental periods. Significant ruminant species X forage and ruminant species X level of intake (P less than .05) interactions were observed for digestible dry matter. The steers digested the switchgrass 7 percentage units greater than the wethers while ryegrass was digested equally. Digestibility differences between the steers and wethers were 6 percentage units at the ad libitum level of intake and 1 unit at the restricted level of intake. Crude protein digestibility tended to be greater (P less than .10) for sheep with a 7 unit difference for switchgrass and a 3 unit difference for ryegrass. The mean ruminal solids retention time of the digesta was approximately (P less than .01) 50% greater (26.0 vs 17.4 h) in cattle, with no difference in ruminal liquid dilution rate (LD) between animal species. Total ruminal volatile fatty acid concentration differed (P less than .01) with level of intake; however, no influence due to intake on the molar proportion of acetate (P greater than .10) or propionate (P greater than .10) was evident in spite of a difference (P less than .01) in LD. Rumen pH (P less than .05) and osmolality (P less than .01) were affected by both level of intake and forage, with the ryegrass and high level of intake decreasing pH and increasing osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
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.  相似文献   

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