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Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) causes fescue toxicosis in cattle grazing the forage, but effects of the endophyte were considered to be abated soon after removal of the animals from pastures. Tasco-Forage, a proprietary extract from the brown seaweed Ascophyllum nodosum, is a known source of cytokinins and has increased antioxidant activity in both plants and the animals that graze the forage. Tasco was applied at 0 and 3.4 kg/ha to infected and uninfected tall fescue pastures in Virginia and Mississippi. Forty-eight steers grazed the pastures at each location during each of 2 yr (n = 192) before being transported to Texas for feedlot finishing. On arrival at the feedlot, steers from Tasco-treated pastures had higher (P [is less than] 0.01) monocyte phagocytic activity and tended (P [is less than] .0.07) to have higher major histocompatibility complex class II expression than steers that grazed the untreated pastures. A depression (P [is less than] 0.05) in monocyte immune cell function due to grazing infected fescue was detected throughout the feedlot finishing period but was reversed by Tasco. Rectal temperatures were elevated (P [is less than] 0.07) in steers that had grazed the infected tall fescue when they arrived in Texas, but by d 14 no difference was detected. However, by d 28 the temperature effects of infected tall fescue were reversed. Steers that had grazed infected fescue had lower (P [is less than] 0.01) rectal temperatures on d 112 of the feedlot period, demonstrating a much longer-lasting effect of the endophyte on thermoregulatory mechanisms than previously thought. Steers that had grazed Tasco-treated pastures had higher (P [is less than] 0.01) rectal temperatures on d 56 than steers that had grazed untreated fescue. Steers that had grazed the Tasco-treated pastures had higher marbling scores (P [is less than] 0.05) regardless of the endophyte, but no effect of Tasco or endophyte on gain was measured. Our data suggest that Tasco application to tall fescue pastures alleviated some of the negative effects of tall fescue toxicity. Key Words: Beef, Carcass Characteristics, Endophytes, Immune Response

Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activity in both plants and animals. Endophyte (Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and uninfected tall fescue (Festuca arundinacea Schreb.) pastures in Virginia and Mississippi during 1997 were treated or not with 3.4 kg Tasco/ha in April and July. There were two replications of each treatment at each location. Forty-eight steers (6/replication) grazed pastures at each location (n = 96) from April to October prior to transportation to Texas Tech, Lubbock, for finishing during a 160-d period in the feedlot. Blood (ante-mortem) and liver (postmortem) samples were collected. After slaughter and chilling, the left strip loins (IMPS #180) were collected from three randomly selected steers from within each pasture replication (n = 48). Strip loins were vacuum-packaged and stored at 2 [degrees] C. At postmortem d 7, 14, 21, and 28, strip loins were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip loins were repackaged and stored at 2 [degrees] C until the following postmortem time. After the prescribed fabrication, steaks were overwrapped with polyvinyl chloride film, subjected to simulated retail display at 2 [degrees] C for up to 3 d, and subjective and objective color were evaluated daily by a trained panel. Steaks from Mississippi steers that had grazed Tasco-treated fescue retained higher (P [is less than] 0.05) CIE a* color scores throughout retail display. Steaks were more uniform and had less discoloration and less browning (P [is less than] 0.05) if they were from steers that had grazed Tasco-treated fescue, and the effect was greatest for steers from Mississippi (location x Tasco interaction; P [is less than] 0.05). The endophyte in tall fescue may decrease uniformity and increase lean discoloration and two-toning of beef steaks when removed from vacuum packaging on or beyond d 21 postmortem (endophyte x Tasco x postmortem day interaction: P [is less than] 0.05). Vitamin E in liver was increased (P [is less than] 0.06) and serum vitamin E was decreased (P [is less than] 0.09) in steers that had grazed the treated pastures. These experiments indicated that Tasco applied to tall fescue during the grazing season can improve color stability and extend beef shelf-life, particularly in cattle grazing infected tall fescue. The mode of action of Tasco is not clear, but antioxidants and specific vitamins may be involved. Key Words: Aquatic Plants, Endophytes, Meat Characteristics, Vitamin E

Effect of preservation method on intake and chewing behavior was examined using a first, late vegetative harvest (mid-June) of Kanlow switchgrass (Panicum virgatum L.). For silage (S), forage was harvested with a commercial field chopper (1.5 to 4 cm average chop length) and ensiled directly in silos 1.2 m in diameter and 3.6 m in height. For hay (H), forage was harvested with a flail-chopper (7 to 15 cm average chop length) and cured as hay in a drier at 77 [degrees] C. Diets of H and S were fed to six Hereford steers (338 [+ or -] 5 kg) in a single crossover experiment. Chewing behavior was monitored for 4 d with a computerized system. At feeding, H was higher in DM and contained greater concentrations (DM basis) of NDF, CP, and hemicellulose, but lower concentrations of ADF and cellulose, and had lower in vitro DM disappearance values. Steers fed S had higher intakes of DM (P [is less than] .02) and NDF (P [is less than] .04) and consumed less water from the water supply (P [is less than] .01) than animals fed H. However, total amount of water (from water supply and feed) consumed per kilogram of DMI did not differ between diets. Crude protein intake was similar between diets. Preservation method had no effect on eating time, number of boli ruminated, bolus duration, and number of rumination chews per bolus. Steers fed S made fewer eating chews (P [is less than] .10) and ruminated for a longer time (P [is less than] .05) while making a greater number of rumination chews (P [is less than] .04) than steers fed H. Rumination intercycle time was slightly shorter in steers fed H (P [is less than] .05) than in steers fed S. When expressed per kilogram of NDF intake, steers fed S spent less time eating (P [is less than] .03) and made fewer eating chews (P [is less than] .02) than steers fed H; however, rumination time, number of rumination chews, and number of boli ruminated were not affected by preservation method. Steers fed S ingested feed at a greater rate (P [is less than] .03), excreted smaller fecal particles (P [is less than] .03), had meals of shorter duration (P [is less than] .06), spent less time eating during main meals (meals following feed distribution: P [is less than] .05), had more rumination periods (P [is less than] .01), and a shorter morning (P [is less than] .06) latency time (interval between end of main meal and onset of rumination) than steers fed H. These results indicate that preservation method with its concomitant differences in chop length affected forage chemical composition and voluntary intake, and that differences in chewing behavior occurred mostly during eating. Key Words: Feeding Behavior, Hay, Panicum virgatum, Silage, Steers

'Carostan' flaccidgrass (Pennisetum flaccidum Griseb.) is a perennial, warm-season grass with potential in forage systems for the mid-Atlantic region. Using established flaccidgrass pastures, we estimated steer (Bos taurus) average daily gain (ADG), stocking rate, and pasture productivity in a 4-yr experiment. Pastures were continuously and variably stocked at a forage mass (FM) of 1895 (Short), 4186 (Medium), and 5297 (Tall) kg ha-1 (linear; P < 0.01). Steer ADG was similar among FM (mean = 0.65 kg d-1). The Short was stocked at 8.3 steers ha-1 and numbers decreased linearly (P < 0.01) to 7.2 steers ha-1 for Tall. Animal days ha-1 decreased linearly (P < 0.01) from 963 (Short) to 756 (Tall). Weight gain ha-1 did not vary significantly (P = 0.14). Effective feed units (kg ha-1) declined linearly (P = 0.02) from 3756 for the Short to 2842 for Tall. Analysis of digesta kinetics revealed no differences among FM in rate of passage, retention time of liquid or solid phases, fill, or fecal output. Diets selected by steers among FM were similar in concentration of in vitro dry matter disappearance (mean = 690 g kg-1); however, CP declined linearly (P = 0.03) while NDF increased (P = 0.01) with increasing FM. Steer ADG was greater (P = 0.03) in Period 1 (0.77 kg d-1 up to early July) compared with Period 2 (0.53 kg d-1 after early July) and attributed to greater forage quality in Period 1. Flaccidgrass is a productive, perennial forage that can provide quality pasture during the summer. [ABSTRACT FROM AUTHOR]

'Carostan' flaccidgrass (Pennisotum flaccidum Griseb.) has potential as a perennial, warm-season grass for pastures. This 2-yr study examined digesta kinetics, dry matter intake (DM1), and diet of steers as related to canopy charactéristics. Steers (Bos taurus L.) were continuo~usly and variably stocked at canopy heights of Short (15 to 20 cm), Medium (30 to 40 cm), and Tall (45 to 55 cm) with forage mass (FM) of 1245, 2600, and 3585 kg ha-1, respectively (linear; p <0.01). Neither mean retention time nor p~assage rate of either liquid or digesta phases were altered by FM. Fecal output increased linearly (p = 0.04) from Short to Tall (0.643 to 0.739 kg 100 1 kg body weight [BW]) indicating a possible variation in DM1. However, DM1 and digestible DM1 (based on leaf in vitro dry matter disappearance [IVDMD]) were similar among FM (mean = 1.99 and 1.29 kg 100-1 kg BW). Leaf imposed 24.3% of the three canopies and was not altered by FM. Stem increased linearly (p = 0.01) from 40.1 to 53.1% with height whereas dead tissue declined linearly (p = 0.06) from 34.8 to 23.4%. Steers selected diets (1 yr data), regardless of FM, similar in IVDMD (mean = 713 g kg-1) and neutral detergent fiber (NDF) (mean 486 g kg-1). In general, steer digesta kibetics were not influenced by FM as animals adjusted grazing behavior to result in similar responses. Flaccidgrass canopies were flexible aipd no particular optimum FM was detecting for an optimum diet. The influence of FM on pasture productivity (regrowth after defoliation) requires additional study. [ABSTRACT FROM AUTHOR]

Tall fescue (Festuca arundinacea Schreb.) is a well-adapted perennial pasture species utilized across the north-south transition zone of the United States. This 3-yr trial evaluated the influence of three forage masses (FM) on steer and pasture responses for spring (April to July) and fall (October) growths. Spring FM averaged 1450 kg ha-1 (Short), 3032 kg ha-1 (Medium), and 3812 kg ha-1 (Tall) for the three treatments. Canopy in vitro true organic matter disappearance (ITOD) decreased linearly from Short (797 g kg-1) to Tall (771 g kg-1). Steer daily gains (0.88 kg) and gains per hectare (392 kg ha-1 yr-1) were not altered by FM, but the mean number of steers per hectare decreased linearly from Short (8.2 steers ha-1) to Tall (6.1 steers ha-1) as did effective feed units per hectare (2256 to 1712 kg ha-1 yr-1). Canopies were predominately leaf (53%) and averaged 847 g kg-1 ITOD with estimates similar among FM treatments. Diet ITOD declined linearly from Short (870 g kg-1) to Tall (839 g kg-1) as did crude protein (CP) (from 235 to 192 g kg-1). In the fall, FM averaged 1556, 3228, and 3494 kg ha-1 for the three FM treatments. Canopy ITOD averaged 774 g kg and was not altered by FM. Canopy leaves averaged 60% with an ITOD of 864 g kg-1 and were similar among FM treatments. Diets selected averaged 834 g kg-1 ITOD and 233 g kg-1 CP and were not altered by FM. Tall fescue pasture free of toxic endophyte needs to be effectively utilized to enhance production and can be managed flexibly in grazing systems. [ABSTRACT FROM AUTHOR]

Management strategies to accommodate switchgrass (Panicum virgatum L.) in production systems have been reported but impact of variation in forage mass (FM) on animal responses and pasture stands are lacking. This 4-yr study assessed canopy and stand characteristic and steer (Bos taurus) responses when 'Kanlow' switchgrass was continuously and variably stocked to produce Short (S) (10-16 cm), Medium (M) (20-26 cm), and Tall (T) (35-41 cm) canopy heights. From April to mid-July (Period 1) FM for S, M, and T average 818, 2164, and 3294 kg ha-1, respectively. Canopies had similar in vitro organic matter disappearance (IVOMD) (626 g kg-1), but increased in neutral detergent fiber (NDF) from S (645 g kg-1) to T (665 g kg-1). Diets decreased in IVOMD from S (744 g kg-1) to T (706 g kg-1). Digesta kinetics data were not altered and average daily gain was similar among FM (1.11 kg d-1). From mid-July to late September (Period 2), FM averaged 465, 1282, and 2388 kg ha-1, respectively, for 5, M, and T. Whole canopy IVOMD increased from S (484 g kg-1) to T (538 g kg-1), whereas NDF was not altered (696 g kg-1). Steers selected a diet similar in IVOMD (685 g kg-1) and NDF (667 g kg-1) among FM. Estimates of dry matter intake (kg 100-1 kg body weight) increased from S (1.75) to T (2.54). Tiller density decreased from T to S. Continuously stocked switchgrass at 20 to 40 cm remained vegetative with 1279 tillers m-2 after 3 yr of grazing. [ABSTRACT FROM AUTHOR]

Ascophyllum nodosum (Tasco-14) decreased the prevalence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in animals fed prior to harvest. Tasco-14 was supplemented on a 2% dry matter basis 14 days prior to harvest to determine its effects on EHEC and Salmonella spp. prevalence. Two hundred mixed crossbred steers and heifers (Bos indicus × Bos taurus), in a large commercial finishing facility, served as experimental units. Treatment (TRT, n = 100) animals received a steamrolled corn-based diet containing 2% Tasco-14 on a dry matter basis, and control (CON, n = 100) animals received only the steam-rolled corn-based diet. Hide swabs and fecal samples were obtained for EHEC and Salmonella spp. evaluations. Animals were sampled 1 day prior to (d - 1) the feeding of Tasco-14 and immediately following exsanguinations. The prevalence of EHEC O157 on hide swabs and in fecal samples (P = 0.0001 and P < 0.0001, respectively) and the prevalence of EHEC O157:H7 on hide swabs and in fecal samples (P < 0.0001 and P < 0.0001, respectively) was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of EHEC O157 and EHEC O157: H7 was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of Salmonella spp. on hide swabs did not change for TRT animals (P = 0.64). CON animals showed an increase in Salmonella spp. prevalence (P < 0.0001) from d - 1 feeding levels on hide swabs. The prevalence of Salmonella spp. increased in both TRT and CON fecal samples when compared to d - 1 levels (P = 0.002). However, TRT samples exhibited a lower (P < 0.05) postfeeding prevalence of Salmonella spp. in fecal samples than did CON samples. Results from this study indicate that 2% Tasco-14 supplementation in feedlot cattle diets reduces EHEC O157 and EHEC O157:H7 prevalence on hide swabs and in fecal samples and may suppress increases in Salmonella spp. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to assess the use of an animal-in-motion-optical-sensor (AIMOS) system allowing for rapid, real-time assessment of variable biomechanical patterns in live cattle. Biomechanical patterns were categorized into groups of gait type and any variations (jump, trot, walk, slip, kick, and run). Biomechanical patterns were measured (0 to 5 V) using a commercial, standard platform containing 1 AIMOS system. Fifty crossbred and purebred (n = 20 Angus, n = 10 Hereford, and n = 10 Angus × Hereford) steers and heifers (n = 50; 292.5 kg average BW) were used in completely randomized design. Over a 2-d period, objective kinetics and subjective kinematics were collected and analyzed. Cattle were run multiple times per test day for a total of 6 runs. Individual cattle exited through a hydraulic chute from which they were guided down a walkway over the AIMOS platform. A signal base unit and computer were placed by the chute to collect near real-time data through integrated fiber optic cabling. Kinetic analog measurements (ratio and amplitude of hoof impacts and ground reaction forces [GRF]) and kinematics (estimated speed and stride length) were recorded from each steer and heifer. Selection variables based on steer and heifer physiological characterizations (breed, sex, and age) were used in linear mixed regression of repeated runs. Visual observations and video analysis were used for categorizing and classifying variable gait patterns after the 2-d period. Temperament traits (excitable, calm, and hesitant) were visually evaluated. Temperature was recorded for each test day (minimum -6°C and maximum 4°C). Individual cattle AIMOS measurements were analyzed for each run, compared with video data, and categorized into pattern groups. The AIMOS system demonstrated differences between and within cattle total vertical GRF (P < 0.05) for variable gait types. No differences were noted for temperature effect. Overall, data suggest the AIMOS system could assess variable gait measurements in a repeated study for detecting cattle biomechanical patterns. [ABSTRACT FROM AUTHOR]

Ascophyllum nodosum (Tasco-14) decreased the prevalence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in animals fed prior to harvest. Tasco-14 was supplemented on a 2% dry matter basis 14 days prior to harvest to determine its effects on EHEC and Salmonella spp. prevalence. Two hundred mixed crossbred steers and heifers (Bos indicus x Bos taurus), in a large commercial finishing facility, served as experimental units. Treatment (TRT, n = 100) animals received a steam-rolled corn-based diet containing 2% Tasco-14 on a dry matter basis, and control (CON, n = 100) animals received only the steam-rolled corn-based diet. Hide swabs and fecal samples were obtained for EHEC and Salmonella spp. evaluations. Animals were sampled 1 day prior to (d - 1) the feeding of Tasco-14 and immediately following exsanguinations. The prevalence of EHEC O157 on hide swabs and in fecal samples (P = 0.0001 and P < 0.0001, respectively) and the prevalence of EHEC O157:H7 on hide swabs and in fecal samples (P < 0.0001 and P < 0.0001, respectively) was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of EHEC O157 and EHEC O157:H7 was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of Salmonella spp. on hide swabs did not change for TRT animals (P = 0.64). CON animals showed an increase in Salmonella spp. prevalence (P < 0.0001) from d - 1 feeding levels on hide swabs. The prevalence of Salmonella spp. increased in both TRT and CON fecal samples when compared to d - 1 levels (P = 0.002). However, TRT samples exhibited a lower (P < 0.05) postfeeding prevalence of Salmonella spp. in fecal samples than did CON samples. Results from this study indicate that 2% Tasco-14 supplementation in feedlot cattle diets reduces EHEC O157 and EHEC O157:H7 prevalence on hide swabs and in fecal samples and may suppress increases in Salmonella spp.

Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2- to 12-yr-old gravid mares (mean BW = 553 kg, SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed alfalfa hay contained less (P < 0.03) CP than milk from mares fed Matua hay. Milk CP decreased (P < 0.01) in all mares over time. In a separate experiment, voluntary intake and rate of passage of Matua (CP = 15.5%), alfalfa (CP = 24.9%), and Timothy (Phleum pratense L.) (CP = 4.1%) hays were determined in nine 2-yr-old pregnant mares (mean BW = 447 kg; SD = 21). Diets were 100% forage. Timothy hay did not meet CP requirements for mares. Voluntary intake of alfalfa hay was higher (P < 0.01) than Matua hay. Intake of Timothy hay was lower (P < 0.01) than the mean of alfalfa and Matua hay. Rate of passage offorage was measured by passage of Cr-mordanted fiber. Passage rate and retention time did not differ between Matua and alfalfa hay; however, the retention times of Matua and alfalfa hays were shorter (P < 0.01) than for Timothy hay. Our results indicate that Matua hay is a forage that can be used safely for mares during gestation and early lactation and for their young foals.

Matua bromegrass (Bromus willdenowii Kunth. cv. Grasslands Matua) was introduced in 1973, but little information exists concerning its potential as a hay for horses. Thus, voluntary intake and apparent digestibility of OM, CP, and fiber components of Matua by 18 Quarter Horse yearlings (mean initial BW 354 kg; SE 5.8) were compared with alfalfa (Medicago sativa L.) and coastal bermudagrass (Cynodon dactylon L.) as hays in a randomized block design. A 15-d adjustment period was followed by a 5-d collection period during which the hays were consumed ad libitum. Voluntary intake of DM was greater (P<.01) for alfalfa (10.9 kg/d) than for the mean of the grasses, and intake of Matua (10.0 kg/d) was greater (P<.001) than that of bermudagrass (7.4 kg/d). Apparent digestibility of OM was greater (P<.001) for alfalfa (74%) than for the mean of the grasses but did not differ between Matua (64%) and bermudagrass (60%). At the end of the digestion trial, each yearling was offered each of the three forage hays during an 11-d period to determine subsequent preference and effect of previous hay experience. Yearlings preferred alfalfa over the grass hays and generally selected more Matua than bermudagrass. All yearlings consumed less of the forage species to which they had been previously exposed compared with unadapted yearlings. The Matua hay fed in this trial was palatable and met most of the nutritional needs for yearling horses.

Forage preference is difficult to assess but is likely an important factor in determining DM intake. In two experiments, six sheep (wethers, Exp. 1; ewes, Exp. 2) were used to obtain preference ratings on nine hays (Exp. 1) or nine fresh forages (Exp. 2). The statistical procedure of multidimensional scaling was used to develop orthogonal dimensions to account for the observed variation in preference for hays and fresh forages. This analysis produced three dimensions that accounted for 54% of the variation in mean 3-d preference for hays (Exp. 1). The three dimensions were subsequently associated by regression analysis with seven compositional variables. These were IVDMD and concentrations of monosaccharides, short-chain polysaccharides (SCP), and disaccharides in dimension 1(R2 = .99); acid detergent insoluble ash (ADIA) concentration, monosaccharide and SCP concentrations, and masticate NDF in dimension 2 (R2 = .99); and disaccharide and starch concentrations in dimension 3 (R2 = .65). Three dimensions accounting for 51% of the variation in fresh forage preference were found and related to four variables by regression analysis. These were disaccharide concentration and median particle size in dimension 1 (R2 = .76) and starch and monosaccharide + disaccharide concentrations in dimension 3 (R2 = .97). No physicochemical variables analyzed in this study were found to be significantly associated with the coordinates for the forages in dimension 2. Multidimensional scaling accounted for more than half the observed variation in animal preference and, in all but one case, these dimensions could be associated with physicochemical characteristics of the forages.

Five maturities of switchgrass hay harvested at 14-d intervals (vegetative through 20% heading) were fed to Hereford steers (297 kg) in a 5 x 5 Latin square. Relationships with switchgrass maturity were negative and quadratic (P < .05) for DMI and cubic (P < .05) for digestible DMI. Declines in apparent digestibilities of DM, ADF, and cellulose were cubic (P < .05), whereas these were quadratic (P < .05) for NDF, hemicellulose, and CP. Whole masticates from the least, mid, and most mature hays showed linear (P < .05) declines in DM concentration and IVDMD with increasing maturity, whereas NDF concentrations increased linearly (P < .05). Mean retention time of gastrointestinal DM increased linearly (P < .01) from 64 to 94 h from the least to the most mature hay, and the associated rate of passage declined linearly (P < .01) from 3.3 to 2.1%/h. Sieving of masticate DM showed a reduced proportion of large particles (> or = 2.8 mm) and an increased proportion of small particles (< or = .5 mm) with advancing forage maturity. More than 94% of the sieved fecal DM passed a 1.0-mm sieve, but particle sizes showed the same relationship with forage maturity as noted for masticate DM. This occurred despite the comminution from the rumination and digestive processes.

One pen feeding study was conducted with 24 wether lambs to compared fecal output (FO) determined by total fecal collection with FO estimated by dosing lambs with chromic oxide controlled-release capsules. Lambs (39 +/- 1.5 kg BW) were fed either alfalfa hay (ALF), Coastal bermudagrass hay (CBG), or a commercially available pelleted (PEL) sheep diet (eight lambs/diet). After dosing, rectal grab samples and total collection of feces were taken daily for 31 d. Constant fecal excretion of Cr was achieved approximately on d 8 (range = d 5 to 13) after dosing. Capsule expiration was accompanied by a sharp peak in Cr excretion approximately on d 27 (range = d 24 to 30). Complete excretion of Cr by d 31 occurred in only seven lambs. Agreement between actual and predicted FO was examined by linear regression from d 8 to 22. Best parameter estimates and highest R2 were observed when sampling a) every other day from d 11 to 19 (five samplings), b) daily from d 8 to 17, c) daily during the entire period, and d) daily from d 13 to 22. Sampling for 5 d chosen at random consistently gave poor results. Sampling every 3rd d gave the poorest results. Controlled-release capsules predicted FO very accurately in lambs fed ALF. Reliable estimates were obtained in 67% of cases investigated with CBG, whereas only 25% of estimates were reliable with PEL. The controlled-release capsules always overestimated FO of wethers fed CBG and PEL, implying that in those lambs the actual release rate of Cr was less than that specified by the manufacturer.

Coastal bermudagrass (Cynodon dactylon [L.] Pers) hay was fed to four ruminally cannulated steers (380 +/- 14 kg BW) of evaluate the effects of intake level on digesta flow kinetics in a 4 x 4 Latin square design. Forage intakes represented 50, 70, 88, and 99% of feed voluntarily consumed per animal during a pre-experimental period. Masticated boli and wet-sieved masticated leaves (ML) and stems (MS) retained by a 4.0-mm sieve and feces retained by a .063-mm sieve were mordanted with chromium or marked with erbium, ytterbium, or dysprosium, respectively. Particle markers and a solution of Co-EDTA were pulse-dosed via the ruminal cannula. A continuous infusion of Co-EDTA was later delivered with peristaltic pumps. Intake level had no effect (P > .10) on fluid and particle passage rate (PR; percentage/hour) of any fractions marked. For all particle fractions, increasing intake level caused linear decreases in mean retention time (MRT; P < .03 to P < .07) and linear increases in gastrointestinal tract fill (FILL; P < .003 to P < .02) and fecal output (FO; P < .001). Estimates of FO and DM digestibility from the pulse dose of Cr mordant and continuous infusion of Co-EDTA did not differ. Kinetic estimates differed in magnitude according to the characteristics of the particle fractions marked. Marked feces gave the shortest estimate of MRT and the smallest estimate of FILL and FO. Kinetics of ML and MS also differed (P < .001), the former having faster PR, shorter MRT, and smaller FILL and FO. Use of representative samples of ingested feed should give more realistic estimates of digesta kinetics than estimates derived from ingesta fractions because kinetics of separated leaf and stem fractions differed.

Several models and markers are available for digesta kinetic studies. In this study, kinetic estimates derived from chromium-mordanted hay or pellets were compared to estimates derived from rare earth markers (Yb, Dy, or Er) applied individually to samples. Twelve yearling rams (52 kg) were given ad libitum access to either hay or a commercial pelleted diet in a crossover experiment. Digesta kinetic estimates were obtained both by nonlinear analysis with two age-independent rates (G1G1) or with gamma time dependency in the fast compartment (G2G1 to G4G1) and by linear regression of natural log transformed fecal marker concentrations (LN method of estimate). Model did not influence total tract (P > .21) or ruminal mean retention times (P > .87). Partitioning of total retention time was similar (P > .21) for the LN, G3G1, and G4G1 models, but the G1G1 and G2G1 models did not adequately fit these data. Nonlinear models overestimated, and LN underestimated, fecal DM output by 9% (SEM = 4.7) for the hay diet. All the nonlinear models provided fecal DM output estimates that were within 5% of actual fecal DM output, but the LN model underestimated it by 18% (SEM = 3.3) for the pelleted diet. Ruminal outflow rate was slower (P < .01) and both ruminal and total mean retention time estimates were longer (P < .01) for Cr than for the rare earths. Despite the marker chosen, relative diet effects were similar. The three rare earth markers gave identical results for digesta kinetic estimates, indicating that they are useful for simultaneous study of more than one ingredient or particle, but direct comparison of rare earth and Cr-mordant passage rates is not advisable.

Three grazing experiments were conducted to compare actual fecal output (FO) by sheep, determined with fecal collection bags, to fecal output predicted using Captec chromic oxide (Cr2O3) controlled-release capsules. In Exp. 1, 14 crossbred wethers dosed with controlled-release Cr2O3 capsules rotationally grazed four paddocks of alfalfa (Medicago sativa L.) for 18 d. Total fecal collection and grab samples were taken daily from each animal; feces were dried and assayed for Cr. From d 5 to 12 after dosing, mean actual FO (429 +/- 9.6 g of DM/d) differed (P less than .001) from FO predicted by the capsule (463 +/- 12.8 g of DM/d). The correlation between actual and predicted FO was r = .59. When data were averaged by day, the correlation increased to .82. In Exp. 2, Tifton 44 bermudagrass (Cynodon dactylon [L.] Pers.) was strip-grazed for 30 d by the same 14 wethers used in Exp. 1. Mean actual FO (369 +/- 5.1 g of DM/d) differed (P less than .0001) from predicted FO (415 +/- 9.3 g of DM/d), with a correlation of .60. In Exp. 3, 72 crossbred lambs were blocked by weight (light and heavy) and assigned to six groups of eight wethers (four with fecal bags) and four ewes, allotted randomly to three stocking rates (74, 99, and 148 sheep/ha). Sampling occurred from d 6 to 10 after dosing (Period 1) and d 20 to 24 after dosing (Period 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Two methods to preserve gastrointestinal tract (GIT) organs and tissues, plastic coating (PC) and plastination (PN), were investigated and compared. Specimens to be preserved were removed from animals within 2 h of death and immediately cleaned with water. Digesta contents were removed by flushing desired portions of GIT with water until the exiting water was clear. In the PC method, cleaned specimens were dehydrated by immersion in an isopropanol solution, dried with forced air after positioning and orientation as in situ, and finally coated on the outer and inner surfaces with a clear plastic material. In the PN procedure, specimens were filled with, and submerged in, a low-formaldehyde fixative, then dehydrated by immersion in a cold acetone solution. Dehydrated specimens were immersed in silicone and placed in a freeze drier for impregnation under low vacuum, followed by overnight gas curing with a silicone crosslinker. Finally, viewing windows were cut out with a scalpel in GIT preserved by both methods. Preserved GIT and tissues had an appearance similar to their appearance in vivo. The PC method was simple and inexpensive. Plastinated specimens were more flexible, durable, and lifelike than those preserved by the PC method. In addition, many body parts, such as muscles, nerves, bones, ligaments, and central nervous system specimens, were preserved by PN. Both methods were found to be useful tools for postmortem studies of tissues and GIT organs.

Eastern gamagrass (Tripsacum dactyloides [L.] L.) has attracted attention as a forage crop, but information on its use is lacking. This 2-yr study compared diet quality, ingestive mastication, and ADG by steers grazing eastern gamagrass (GG), flaccidgrass (Pennisetum flaccidum Griseb.), and Tifton 44 bermudagrass (Cynodon dactylon [L.] Pers.). The design was a randomized complete block with two agronomic replicates. The diet selected by steers from GG in May did not differ from the diet selected by steers from flaccidgrass (FG) for IVDMD (77.3%), NDF (44.0%), CP (19.5%), and mean and median particle sizes of the ingesta (1.8 and 1.4 mm). In July, GG diets had three percentage units less IVDMD (P less than .05), 8.4 percentage units more NDF (P less than .05), and 4.5 percentage units less CP (P = .07) than the mean of FG and bermudagrass (BG). The canopy (July) of GG had the greatest proportion of its DM as leaf (59 vs 26% for FG and 22% for BG) and the least proportion as stem (25 vs 40% for FG and 59% for BG). Mean particle size (millimeters) of masticates differed (P = .05) among forages with GG greatest (2.2), followed by FG (1.6), and BG particles were smallest (1.2). Proportion of large (greater than or equal to 2.8 mm), medium (less than 2.8 greater than or equal to .5 mm), and small (less than .5 mm) particles of the masticate DM, and their IVDMD and NDF concentration, interacted with species (P less than .05). Gamagrass masticate had the greatest proportion (28%) of large particles and BG the greatest proportion (23%) of small particles. The least IVDMD occurred for large particles of BG (62.5%) and small particles of GG (63.8%). Digesta kinetics did not differ among species. Characteristics of GG yielded steer ADG of .82 vs .67 kg for FG and .30 kg for BG (P = .05).

In traditional grazing trials, per animal and per hectare productivity are determined, but pasture and animal measurements are generally inadequate to address reasons for different treatment responses. This 2-yr study examined the diet and diet characteristics of steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.) pastures. A randomized complete block design was used with two agronomic replicates. In vitro DM disappearance (IVDMD) of masticates from tall fescue (TF), switchgrass (SG), and flaccidgrass (FG) generally were similar; all exceeded 70% (70.3 to 79.9%), except for bermudagrass (BG), which was lowest (63.5 to 65.0%). Sieving the masticate DM showed BG to contain the highest proportion (20 to 29%) of particles passing a .5-mm sieve and the lowest proportion (6 to 8%) of particles retained on a 2.8-mm sieve. This resulted in BG having the smallest mean (1.29 mm) and median (1.08 mm) particle sizes in yr 1 and a mean (1.10 mm) and median (.91 mm) particle size smaller than SG in yr 2. Except for BG, the IVDMD of the masticate DM was lowest for small particles. Canopies showed BG and SG to have the highest proportion of stem (47 and 52%, respectively); the BG canopy was composed of fractions that were consistently lowest in IVDMD. In general, BG offered the grazing animal a canopy inferior in IVDMD concentration and had canopy characteristics that limited the animals' selection of a diet with quality as high as that of TF, SG, or FG.

Animal responses to treatments in grazing experiments frequently remain unexplained because of inadequate pasture and(or) animal measurements. This 2-yr study examined DMI, gastrointestinal tract fill of undigested DM (FILL), rate of digesta passage (ROP), and digesta mean retention time (MRT) for steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.). A randomized complete block design was used with two agronomic replicates. Comparisons in June (yr 1) among continuously grazed switchgrass (SG), flaccidgrass (FG), and bermudagrass (BG) or in May (yr 2) among tall fescue (TF), SG, and FG showed similar digesta kinetics, but different DMI (kg.d-1.100 kg BW-1), among these forages within each sampling. In the June evaluation, the DMI of SG and FG were similar (means = 3.09), DMI of bermudagrass (BG) was lowest (2.23), and fecal DM output (FO) was similar among forages. In the May evaluation, DMI by steers grazing SG (3.90) was higher than that by steers grazing FG (2.97); DMI of tall fescue (TF) was intermediate (3.41) but similar to DMI of FG. Differences in DMI were due to differences in diet in vitro DM disappearance (IVDMD) rather than to differences in digesta kinetics. In July (yr 2), the MRT was highest for BG (84 h) and similar for SG and FG (57 h). Steers grazing different forages exhibited similar ROP and FILL, but FO (kg.d-1.100 kg BW-1) among steers varied (.37 for steers fed BG; .74 for steers fed SG and FG).(ABSTRACT TRUNCATED AT 250 WORDS)

In an experiment to determine the effects of mastication and microbial contamination on in situ forage disappearance, samples of masticated (M) or nonmasticated alfalfa hay (AH), orchardgrass hay (OGH) and bermudagrass hay (BGH) were incubated in the rumen of two steers for 6, 12, 24, 48 and 96 h. Using diaminopimelic acid as a marker, microbial DM and CP contamination ranged from 10.3 to 22.3% and 46.3 to 95.3% of residual DM and CP, respectively. Percentage contamination was influenced by both time of incubation and forage treatment (P less than .001). Corrected DM and CP disappearances (DMD and CPD) were higher than apparent disappearances (P less than .001). Maximal NDF and ADF disappearances (NDFD and ADFD) obtained at 96 h were 58.2, 52.4; 62.7, 62.3 and 56.7, 52.6% for AH, OGH and BGH, respectively. Lag times (h) for corrected DMD and CPD were shorter (at least P less than .05) than for apparent disappearances, except for corrected CPD of AH. There were no differences (P greater than .10) in lag time of NDFD or ADFD among forages. Rates of disappearance (%/h) of corrected DMD and CPD were faster (at least P less than .01) than for apparent disappearances. The total quantity of microbial CP (mg CP/g DM) associated with residues varied with time depending on forage type (P less than .001). There was a significant relationship between the quantity of microbial CP contamination and the extent of disappearance. Masticated forages followed trends similar to those of nonmasticated forages, but the effect of mastication was not consistent. Results support the need for microbial correction of in situ forage residues.

Eating and ruminating behavior and associated ruminal motility of six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) given ad libitum access to corn silage with or without 100 mg monensin X head-1 X d-1 were examined according to a two-period crossover design. There was no effect (P greater than .05) of monensin on level of intake, daily and unitary eating, ruminating and masticating times [min X g dry matter-1 X (kg body weight X 75)-1], duration or number of these activity periods, duration of main meals or latency time for onset of rumination following cessation of main eating activities. With the monensin treatment, daily numbers of normal boli and total boli were decreased (P less than .05) and mean duration of one rumination bolus cycle was longer (P less than .05). Analysis of covariance indicated relationships between intake of corn silage and duration of the main morning meal, duration or number of rumination boli and total ruminal contractions were affected (P less than .01) by monensin. Frequency and unitary number of strong cranio-dorsal ruminal contractions were similar for both treatments. During eating, number of contractions per minute was about twice (2.55/min) that during idling and rumination activity (1.43/min and 1.22/min, respectively). The unitary daily number of contractions was negatively (P less than .05) related to level of intake. Total daily ruminal contractions were slightly reduced (-3.96%, P greater than .05) by monensin. Results are interpreted to suggest that monensin indirectly affects rumination through a lowered motility and thereby affects turnover, gut fill and intake.

Effects of time of day and dietary monensin in the distribution of size of digesta particles in different digestive tract sites and their intersite relationships were examined in six heifers (290 kg BW) with ruminal, duodenal and ileal cannulas given ad libitum access to corn silage, with or without 100 mg monensin.head-1.d-1, in a two-period crossover design. Ingestive masticate and digesta of corn silage were collected via esophageal, ruminal or intestinal cannulas. The distribution of particulate matter retained on sieves with apertures larger than 20 microm was determined by wet-sieving. The cumulative distribution of particulate matter on a series of sieves was regressed on retaining sieve aperture to estimate the sieve aperture that would retain 50% weight of the particulate matter (median retaining aperture, MRA). The MRA of masticate was 6,494 microm. The MRA of digesta particles decreased (P less than .05) from ventral rumen (1,847 microm) to dorsal rumen (1,797 microm) to duodenum (346 microm), but increased to the rectum (359 microm). The MRA was lower (P = .044) for the monensin treatment only in feces. The MRA of particulate matter in the dorsal and ventral rumen, duodenum and rectum all changed (P less than .05) over 24 h. An inverse pattern between the MRA of ruminal and duodenal digesta occurred, presumably the result of a nycterohemeral pattern of eating and ruminating activity. Across sampling times, an inverse relationship existed between MRA of ventral rumen and duodenal digesta. This relationship suggests that a ruminal digesta raft composed of larger particles (immediately following major meals) is more effective than a raft of smaller particles (prior to such meals) in preventing flux of large particles to the duodenum.

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Two forms of corn, whole (WC) and ground (GC), were fed with hay (WH; 900) or 4 h after hay (AH; 1300) feeding to evaluate their effects on growth, starch utilization and digesta passage characteristics in growing steers. Twenty-four Angus steers with ad libitum access to fescue hay were individually limit-fed ground or whole corn (2.27 kg/d) in a 2 x 2 factorial arrangement of treatments: GC- WH, GC-AH, WC-WH and WC-AH. Average daily gain was improved with feeding GC (P less than .08), especially when fed at the same time as hay. Fecal starch (%) was less (P less than .001) for GC (7.07) than for WC (15.68). No difference was observed in rate of liquid or solid (hay) passage. Mean retention time (MRT) of whole corn (stained with neutral red and crystal violet) was decreased (P less than .07), and rate of corn passage tended to be faster for steers fed WC-AH than for those fed WC-WH. Although time of corn feeding had no effect on performance, steers fed WC-AH had more whole corn particles recovered from the feces and the MRT for whole corn particles was reduced, indicating that time of supplementation may affect passage characteristics. Altering time of supplement feeding may have applications in other feeding situations, such as with protein supplementation where ruminal escape would be advantageous.

An alternative exponential equation with a parameter as an exponent was compared to a recently published exponential procedure for estimating mean and median particle size. Both equations were fit to literature values for particle size distributions of esophageal extrusa, rumen digesta, and feces. In addition, 112 observations of particle-size distributions of esophageal extrusa were fit to both equations for comparison. Both equations gave adequate fits of rumen digesta and feces, but the earlier model was biased by regular deviations from observed data for esophageal extrusa. Use of the previously published model overestimated mean particle size in esophageal extrusa from 4.5 to 10.3%. Median particle size was underestimated from 4.9 to 5.6%. Analytic solutions exist for mean and median particle sizes for the earlier model, but it is necessary to estimate numerically the mean and median particle sizes when using the proposed equation. Even though the solution for the proposed equation must be determined numerically, it will prevent bias between experimental treatments, give more accurate estimates of mean and median particle size, and result in a lower residual sums of squares. In addition, a single equation can be used to model particle size reduction throughout the digestive tract.

Six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) with ruminal, duodenal and ileal cannulae given ad libitum access to corn silage with or without 100 mg monensin X head-1 were used to determine interrelationships among behavior, ruminal motility and intake. Voluntary intake was positively related (P less than .001) to eating time, duration of the main morning meal and daily mastication time. Intake was negatively related to unitary times [min X g dry matter-1 X (kg body weight X 75)-1] of eating (P less than .05), rumination (P less than .001), mastication (P less than .001), unitary number of rumination boli (P less than .001), and latency time between termination of morning meal and onset of rumination (P less than .05). Both daily and unitary eating and ruminating time were positively related (P less than .001) to daily and unitary mastication time and unitary number of strong cranio-dorsal ruminal contractions. Positive relationships (P less than .01) were found between mean duration of daily meals, main evening meal and unitary eating time, and between mean duration of rumination periods and unitary ruminating time. Daily and unitary number of rumination boli and mean duration of one bolus were positively related (P less than .01) to unitary ruminating time. Interrelationships between intake, eating and ruminating activities and associated cranio-dorsal ruminal motility were all influenced (P less than .01) by individual heifer, which indicates potential in identifying individuals with better than average mastication behavior and ruminal motility.(ABSTRACT TRUNCATED AT 250 WORDS)