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PubMed1993

The effects of different methods of estimating fecal output on plasma cortisol, fecal output, forage intake, and weight change in free-ranging and confined wethers.

Thirty-four white-face wethers (avg BW 56 kg) were used in two experiments to investigate differences in plasma cortisol, forage intake, fecal output, and BW change associated with two methods of estimating fecal output. The methods were fecal collection bags (B) and marker estimates of fecal output (U). A control treatment (C) was included in each experiment in which wethers were not bagged or dosed with the marker. Experiment 1 was conducted with wethers grazing dormant sagebrush-bunchgrass range. Experiment 2 was conducted with wethers housed in metabolism crates. In Exp. 1, the following differences were detected: 1) basal and mean integrated (following ACTH challenge) plasma cortisol levels were higher (P < .05) for U wethers than for C wethers, 2) no differences (P > .05) between B and C wethers were detected for basal or mean integrated plasma cortisol, 3) both B and U wethers gained (P < .05) weight, whereas C wethers lost weight, and 4) no differences (P > .05) between B and U wethers were detected for cortisol measurements, weight change, or fecal output. No differences (P > .05) were noted for any of the variables tested in Exp. 2. When treatments were combined within experiment to test Exp. 1 vs 2, time to peak cortisol levels was longer (P < .05) and mean integrated cortisol levels and weight change were lower (P < .05) for wethers in confinement than for wethers on range. No difference (P > .05) was detected for basal cortisol levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Technical note: labeling of forages with 13C for nutrition and metabolism studies.

Alfalfa was labeled in the field with 99 atom % 13CO2 and cut either the same day (C1) or 30 d after labeling (C30). The C1 alfalfa contained 84% of the 13C label in cell contents, whereas C30 alfalfa contained 47% of the 13C label in cell contents. In two separate trials, C1 and C30 alfalfa were dosed to two or four Suffolk ewes fed natural abundance alfalfa diets. Carbon isotope ratios (13C/12C, expressed as delta 13C/1000 [parts per thousand] vs Pee Dee Belemnite standard) were determined for breath, feces, blood, and blood serum from ewes fed C1 alfalfa and blood and feces from ewes fed C30 alfalfa. In the C1 trial, carbon isotope ratios of respired CO2 peaked 4 h after feeding, then declined to baseline levels by 40 h after the dose. Fecal samples increased in 13C only slightly from 12 to 40 h after the meal. Blood serum values increased by approximately .5/1000 from 0 to 4 h after the dose and remained relatively constant thereafter. In both trials, carbon isotope values from whole blood were constant. In the C30 trial, fecal samples peaked in carbon isotope value approximately 30 to 36 h after dosing, then declined; the time of this peak corresponded closely to that from a concurrent study that used a pulse dose of Yb-labeled alfalfa hay. Thus, when incorporated into cell wall material, the excretion pattern of 13C in feces was similar to that of Yb-labeled hay, but little 13C enrichment in feces was found when 13C was primarily in cell contents of the labeled forage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1993

Steers grazing endophyte-free tall fescue: seasonal changes in nutrient quality, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites.

Six ruminally cannulated Holstein steers (average BW 514 kg) grazed a 33-ha, unirrigated, endophyte-free, tall fescue (Festuca arundinacea Schreb.) pasture from April 10 through December 7, 1989. Samples were collected in May, June, September, and November 1989. Total masticate N was relatively constant (P > .10) throughout the year. Masticate in vitro OM disappearance was less (P < .05) in September (48.4%) and November (50%) than in May (60.6%) and June (56%). Ruminal NH3N concentrations (milligrams/deciliter) were greater (P < .05) during May (20.5) and June (17.8) than during September (9.4) and November (5.9). Organic matter intake (grams/kilogram of BW) and particulate passage rate (percentage/hour) were least (P < .05) in November (15.3; 2.6) and not different (P > .10) during May (23.7; 3.1), June (20.7; 3.1), and September (21.0; 3.0). Extent and rate of NDF digestion and ruminal total VFA did not differ (P > .10) across sampling dates. Serum glucose concentrations were not affected (P > .10) by sampling date, but serum urea N was greater (P < .05) during May and November than during June and September. Nonesterified fatty acid concentrations increased (P < .05) with advancing plant maturity. Serum insulin concentrations were greater (P < .05) during May than during other sampling periods; however, growth hormone concentrations were not altered (P > .10) by advancing plant maturity. Unirrigated fescue pasture maintained a high nutrient level throughout the grazing season, and masticate samples did not display the decrease in nutrient content often noted with other types of pasture forage.

Ammonia↗
PubMed1994

Effects of mesenteric vein L-alanine infusion on liver metabolism of organic acids by beef heifers fed diets differing in forage: concentrate ratio.

Effects of diet forage:concentrate ratio and mesenteric vein L-alanine infusion on net VFA metabolism by portal-drained viscera (PDV) and liver were determined in four multicatheterized Hereford x Angus heifers (443 kg BW) fed in equal meals every 2 h pelleted, isonitrogenous diets containing 75% alfalfa or 75% corn:soybean meal (SBM) in a balanced single reversal of diets with 6 wk for adaptation. In addition, effects of L-alanine infusion on net metabolism of individual amino acids (AA) by PDV and liver was determined when heifers were fed 75% corn:SBM. Four measurements of blood flow (p-aminohippurate dilution) and net flux of VFA and AA (venous-arterial difference times blood flow) were obtained at 30-min intervals immediately before beginning and ending a 24-h mesenteric vein infusion of L-alanine at 75 mmol/h. Net PDV absorption of acetate (P < .02), propionate (P < .02), and total VFA (P < .02) was lower when 75% corn:SBM was fed, reflecting increased carbohydrate digestion postruminally and only partially balanced by increases in net PDV glucose absorption reported previously. In addition, net PDV absorption of n-butyrate was lower when 75% alfalfa was fed. Excluding acetate, net liver removal of VFA was 83 to 108% of their net PDV release. L-Alanine infusion did not affect net PDV or liver flux of VFA but decreased net total splanchnic (PDV plus liver) release of propionate (P < .07) and n-butyrate (P < .03) and decreased (P < .10) net PDV release and liver removal of glycine. In spite of the increase in liver L-alanine removal, the ratio of glucose release to precursor removal remained remarkably constant across the liver when L-alanine was infused, emphasizing the tight control of liver glucose release and the dynamic interplay of precursor supply and removal in the maintenance of liver carbon balance.

Alanine↗
PubMed1994

Supplemental protein for beef cattle grazing dormant intermediate wheatgrass pasture: effects on nutrient quality, forage intake, digesta kinetics, grazing behavior, ruminal fermentation, and digestion.

Sixteen ruminally cannulated yearling beef cattle (British x British; average BW = 295 +/- 25 kg; three steers and one heifer per treatment) grazing dormant intermediate wheatgrass (Thinopyrum intermedium Host) were allotted to four treatments: 1) no supplement (CON); 2) alfalfa hay (ALF; .52% of BW); 3) cottonseed meal (CSM; .22% of BW); and 4) corn gluten meal-wheat bran feed (CGMWBF; .36% of BW). Supplements were formulated (DM basis) so that intakes were isonitrogenous and were provided once daily (0700). Sampling periods were in February (FEB; .96% N in masticate), March (MAR; 1.06% N in masticate), and April (APR; 1.12% N in masticate) following an initial 21-d adaptation period. Daily grazing time was 1.1 to 1.5 h longer (P < .05) for CON cattle than for supplemented cattle. Forage OM intake (OMI) was not altered (P > .15) by supplemental protein; however, total OMI was greater (P < .04) for supplemented than for unsupplemented cattle. Harvesting efficiency (grams of OM intake-kilogram of BW-1.minute spent grazing-1) was greater (P < .05) for cattle fed CSM than for those fed CGF or CON; cattle fed ALF were intermediate in harvesting efficiency. Ruminal fluid kinetics, in situ rate and extent of NDF digestion, and total VFA concentration were not influenced (P > .10) by type of supplemental protein. Ruminal NH3 N concentration exhibited a treatment x sampling time interaction (P < .05). Type of protein supplement did not seem to affect most digestion measures; however, harvesting efficiency was influenced by supplement type.

Animal Feed↗
PubMed1995

Value of feather meal in a molasses-based liquid supplement fed to yearling cattle consuming a forage diet.

Hydrolyzed feather meal (FM) was compared to other sources of CP to determine its value as a protein source in a molasses-based liquid supplement. Ruminal N escape values (measured in situ) for FM, ring-dried blood meal, cottonseed meal, and soybean meal approximated reported values. Ruminal N escape value for catfish meal was lower than values reported for other fish meals. In two trials (194 d), 84 yearling heifers were allotted to 12 pastures (3 pastures/treatment) and fed one of four supplements (1.7 kg of DM.heifer-1.d-1) containing either molasses and urea; molasses, urea,and FM; molasses, urea, FM, and catfish meal; or molasses, urea, FM, and catfish oil. Heifers were exposed to bulls for 60 d. In two trials, 112 steers were allotted to 16 pastures (4 Pastures/treatment) and fed one of four supplements (1.7 kg of DM.steer-1.d-1) containing molasses and urea; molasses, urea and FM; molasses, urea, FM and ring-dried poultry blood meal; or molasses, urea, and poultry feathers and blood hydrolyzed together. In all trials, cattle fed molasses containing FM had faster gains (P < .05) and heifers had heavier live weights at breeding (P < .05) and higher pregnancy rates (P < .05) than cattle fed molasses and urea. Combining poultry blood with molasses, urea, and FM improved (P < .05) steer gains in one of two trials. Combining catfish meal with molasses, urea, and FM did not improve (P > .05) ADG of pregnancy rate of heifers. Combining catfish oil with molasses, urea, and FM increased (P < .05) ADG in one trial and blood cholesterol and live weight of heifers at breeding in both trials. It is concluded that protein feeds, such as FM, that contain a large portion of ruminally undegradable protein may provide much of the CP in liquid supplements fed to growing cattle consuming moderate-quality forage. Adding catfish oil to a liquid supplement may improve ADG and live weight of yearling heifers at breeding.

Aging↗
PubMed1996

In vivo and in situ measurements of forage protein degradation in beef cattle.

In vivo and in situ protein degradation measurements were compared using alfalfa (2.62% N) and prairie hay (.88% N) fed to six cannulated cows in a two-period crossover experiment. Additionally, two in situ procedures were evaluated: in P1 samples were ruminally incubated in cows fed the same forage as incubated; in P2 samples were incubated in the rumens of two steers fed a "standard" brome hay (1.38% N). Duplicate bags were incubated for 0, 2, 6, 10, 16, 24, 48, and 72 h. Protein degradability was estimated using residual N from all incubation times fit to a nonlinear, least squares model (full time-series), from the 16-h incubation alone (single-point) and from a combination of the 0-h and 16-h values (double-point). Protein degradability estimates from in vivo, in situ P1, in situ P2, single-point P1 and P2, and double-point P1 and P2 were 83.4 +/- 4.3, 91.5 +/- .6, 87.2 +/- .6, 94.0 +/- .2, 92.4 +/- .8, 90.4 +/- .4, and 88.3 +/- .5, respectively, for alfalfa, and 55.5 +/- 3.5, 58.3 +/- 1.3, 57.2 +/- .4, 50.0 +/- 1.7, 52.0 +/- 2.2, 55.5 +/- 2.1, and 60.0 +/- 2.3, respectively, for prairie hay. Although relatively large differences in rates of degradation and sizes of protein fractions were measured between P1 and P2, differences between procedures for protein degradability estimates were small relative to errors of in vivo measurement. Furthermore, differences in protein degradation using single-point values as compared with full time-series analysis were overcome with the double-point approach.

Animal Feed↗
PubMed1996

Integration of regulatory signals controlling forage intake in ruminants.

Numerous factors have the potential to affect the amount of forage or pasture eaten by ruminant animals, including gut capacity, ability of tissues to metabolize nutrients, ruminal acidity, and osmolality. Much research into the control of food intake has tested one particular theory, often by applying greater degrees of stimulation than occur naturally, and is then unable to explain how physiological changes in that stimulus can be responsible for controlling intake. We have found that the effects of two or three stimuli (sodium acetate, sodium propionate, ruminal distension) applied together were additive. As to the site of this integration, receptors in the rumen wall are sensitive to both mechanical stimulation and acids, with transmission of impulses in vagal afferent fibers probably modulated by the osmolality of ruminal fluid. Thus, a certain degree of integration ("polymodal") is likely to have occurred at the level of the transceiving organ. A second level of integration is "polytopic." In this level stimulation of one visceral site modifies the effects of the same type of stimulus at another site. A third level of integration occurs in the central nervous system, whereby the effects of visceral stimulation might be balanced with signals from other stimuli (e.g., the special senses) to determine whether feeding should take place at any given moment. The thesis presented is that the central nervous system receives a nonspecific signal from the viscera; the animal might then learn to eat that amount of food that minimizes the competing discomforts of excessive abdominal visceral stimulation and shortage or imbalance of nutrients.

Animals↗
PubMed1996

Physical constraints on voluntary intake of forages by ruminants.

Voluntary dry matter intake (VDMI) of forages by ruminants may be limited by distention resulting from restricted flow of digesta through the gastrointestinal tract. An animal's capacity for fill depends on the weight and volume of digesta that causes distention and the flow rate of digesta from the organ in which distention occurs. The reticulorumen is generally regarded as the site in the gastrointestinal tract for which distention limits VDMI with high-fill diets, although evidence suggests that distention of the abomasum may also limit VDMI. Linear decreases in VDMI have been noted with increasing amounts of inert fill inserted into the reticulorumen, but results have not been consistent across several experiments. Reduction in VDMI depends on the extent to which intake is limited by fill before insertion of inert fill; hence animals with high energy requirements consuming relatively low-energy, high-fill diets are affected to the greatest extent. Because NDF generally ferments and passes from the reticulorumen more slowly than other dietary constituents, it has a greater filling effect over time than non-fibrous feed components and has been found to be the best single chemical predictor of VDMI. However, many other factors affect fill, including particle size, chewing frequency and effectiveness, particle fragility, indigestible NDF fraction, rate of fermentation of the potentially digestible NDF, and characteristics of reticular contractions. These factors are only partially accounted for in models that have been developed to predict VDMI. Increased accuracy of prediction of VDMI is expected as models continue to evolve.

Animals↗
PubMed1996

Acquired aversions as the basis for varied diets of ruminants foraging on rangelands.

Ruminants eat an array of plant species that vary in nutrients and toxins. This selection makes intuitive sense, but no theories adequately explain this diversity. Some maintain it reduces the likelihood of overingesting toxins, whereas others contend it meets nutritional needs. Nevertheless, herbivores seek variety even when toxins are not a concern and nutritional needs are met. I offer another explanation for this behavior, one which encompasses the avoidance of toxins and the acquisition of nutrients. A key concept in this theory is aversion, the decrease in preference for food just eaten as a result of sensory input (a food's taste, odor, texture, i.e., its flavor) and postingestive effects (effects of nutrients and toxins on chemo-, osmo-, and mechano-receptors) unique to each food. Aversions are pronounced when foods contain toxins or high levels of rapidly digestible nutrients; they also occur when foods are deficient in specific nutrients. Aversions occur even when animals eat nutritionally adequate foods because satiety (satisfied to the full) and surfeit (filled to nauseating excess) represent points along a continuum, and there is a fine line between satiety and aversion. Thus, eating any food is likely to cause a mild aversion, and eating a food too frequently or in excess is likely to cause a strong aversion. Aversions are involuntary and are not the result of conscious decisions by an animal. Aversions yield benefits (e.g., obtain a balanced diet, reduce ingestion of toxic foods, optimize foraging and rumination times, sample foods, maintain a diverse microflora in the rumen) that are often mistaken as the cause of varied diets. In this article, I discuss the subtle ways in which aversions diminish preference and cause animals to eat a variety of foods.

Animal Feed↗
PubMed1997

Effects of supplemental energy source and amount on forage intake and performance by steers and intake and diet digestibility by sheep.

Two levels of concentrate supplements containing different types of carbohydrates (corn-soybean meal, CSBM; wheat middlings, WM; and soybean hulls, SBH) were evaluated for effects on forage intake and performance in growing steers and total diet digestibility in sheep. In Exp. 1, 63 crossbred yearling cattle (298 and 377 kg initial BW for yr 1 and 2, respectively) were given ad libitum access to chopped bermudagrass (Cynodon dactylon [L.]) hay with no supplementation (CONTROL) or with 25 or 50% of projected total TDN intake from CSBM, WM, or SBH. In Exp. 2, digestibilities of organic matter (OMD) and neutral detergent fiber (NDFD) were determined with sheep fed levels of hay and concentrates similar to those used in the growth trials. Hay intake was 1.99% of BW for steers fed hay alone and averaged 1.93% of BW in steers fed supplements at the low level. At the high level of concentrate supplementation, hay intake was depressed (P < .001) to a similar extent (1.63% of BW) in steers supplemented with CSBM, WM, or SBH. AT the low concentrate level, shrunk ADG was similar (.63 kg/d) among supplements, but at the high concentrate level steers fed SBH had higher (P = .06) shrunk ADG (.95 kg/d) than steers fed CSBM (.76 kg/d). Body condition score (BCS) increased more (P = .06) for CSBM- and SBH- than for WM-supplemented steers. Total tract OMD was lower (P < .001) in sheep fed WM (54.8% for low and 56.9% for high supplementation levels) than in sheep fed CSBM (57.4 and 62.6%) or SBH (57.2 and 62.5%). Total tract NDFD was higher (P < .001) for the SBH (58.9% for low and 63.3% for high levels) diets than for CSBM (54.6 and 51.0%) or WM (54.6 and 51.8%) diets. Supplements containing highly digestible fiber (SBH) produced less negative associative effects than high-starch supplements (CSBM) when fed with bermudagrass hay at the high level (.8 to 1% of BW), but no differences were found at the low feeding level (.4 to .5% of BW).

Animal Feed↗
PubMed1999

Low- and high-quality forage utilization by heifers and mature beef cows.

Eight cows (7 to 9 yr old, 522 kg) and six heifers (10 mo old, 169 kg) were fed either alfalfa hay (18.7% CP) or mature brome hay (5.1% CP) to determine the effect of cattle age on apparent forage utilization. Cattle were fitted with ruminal and duodenal cannulas and were individually fed once daily (ad libitum intake, 1000). The split-plot design consisted of age (whole-plot) and two sampling periods feeding alfalfa or brome hay (subplot). Each period consisted of 28 d: d 1 to 13 for adaptation, d 13 to 20 for feed intake determination, and d 20 to 28 for sampling. Nylon bags containing NDF substrate from alfalfa or brome hay were incubated ruminally for 0, 3, 6, 12, 24, 48, 96, and 192 h to determine the rate and extent of fiber degradation. Ruminal liquid dilution rate and fermentation characteristics were conducted on d 27. Ruminal fill was determined by total evacuation at 0800 on d 28. Cows consumed more feed (BW.75; P<.01) and had greater ruminal OM fill (P = .04) but had similar fluid fill (P = .88) compared with heifers. Ruminal liquid dilution rate was greater in cows than in heifers (P<.01). The rate of in situ NDF degradation was 3 and .5% per hour greater in cows than in heifers when alfalfa and brome hay were fed, respectively (age x hay, P<.01). Ruminal NDF digestibility as a percentage of intake was greater in cows than in heifers (P<.01). Numbers of ruminal cellulolytic bacteria were not affected by treatment (P>.21). These data indicate that mature cows have a smaller ruminal fluid fill that turns over more rapidly, and this may be responsible for a faster rate of ruminal fiber degradation in cows than in young heifers.

Aging↗
PubMed1999

Influence of mass and volume of ruminal contents on voluntary intake and digesta passage of a forage diet in steers.

To assess the influence of volume and mass of ruminal contents on voluntary intake and related variables, five ruminally cannulated steers (550 kg) were fed a low-quality forage diet (43.1% ADF, 8.1% CP) in a 5 x 5 Latin square experiment. Mass and volume of ruminal contents were altered by adding varying numbers and weights of filled tennis balls (6.7-cm diameter) to the rumen immediately before the initiation of each experimental period. Treatments consisted of 0 balls (control), 50 balls with a 1.1 specific gravity (SG), 100 balls with a 1.1 SG, 50 balls with a 1.3 SG, and 100 balls with a SG of 1.3. The total volume of balls was 7.25 and 14.5 L for 50 and 100 balls, respectively. The total weight of balls was 8.5 and 17 kg for 50 and 100 balls with a 1.1 SG and 10.75 and 21.5 kg for 50 and 100 balls with a 1.3 SG, respectively. Daily DMI was 8.3, 7.3, 7.0, 6.5, and 6.0 kg for control; 50, 1.1 SG; 50, 1.3 SG; 100, 1.1 SG; and 100, 1.3 SG, respectively. Addition of balls to the rumen reduced (P < .01) DMI. Increasing the number (P < .01) and SG (P <. 01) of the balls decreased DMI further. However, digestibilities of DM, NDF, ADF, and CP were not influenced by treatment. Increasing the number of balls in the rumen increased (P < .05) rate of passage of digesta from the rumen, but increasing SG of the balls did not alter rate of passage. There was a treatment x hour interaction (P < .05) in the proportion of ruminal digesta with a functional specific gravity (FSG) less than 1.1, which decreased with time after feeding for the control but increased with time after feeding for other treatments. Ruminal passage rate of inert particles added in the rumen of different SG (1.1 and 1.3) and length (1 and 3 mm) decreased (P < .05) as SG of the balls increased. Mean fecal particle size was greater for those treatments with the heavier balls. Both the number and SG of balls (P < .10) influenced total VFA, and total concentrations were greater for the control and for the 1.1 SG than for the 1.3 SG treatments.

Ammonia↗
PubMed2001

Soybean hulls as a primary ingredient in forage-free diets for limit-fed growing cattle.

In Exp. 1, 300 heifers (260 kg initial BW) were used to compare growth performance of cattle fed forage-free diets containing predominantly soybean hulls with that of cattle receiving roughage- and corn-based diets and to determine whether cattle fed soybean hull-based diets would respond to supplementation with methionine hydroxy analogue (MHA), lipid-coated betaine, or concentrated separator by-product (CSB; a source of betaine). Treatments included 1) a roughage-based diet fed at 2.75% of BW, 2) a corn-based diet fed at 1.5% of BW, 3) a corn-based diet fed at 2.25% of BW, 4) a soybean hull-based diet fed at 1.5% of BW (SH1.5), 5) a soybean hull-based diet fed at 2.25% of BW (SH2.25), 6) SH1.5 top-dressed with 11.4 g/d Alimet (10 g/d MHA), 7) SH2.25 top-dressed with 11.4 g/d Alimet, 8) SH2.25 top-dressed with 7 g/d of a lipid-coated betaine product (4.2 g/d betaine), and 9) SH2.25 top-dressed with 250 g/d CSB (15.5 g/d betaine). Supplemental MHA, betaine, and CSB did not change DMI, ADG, or gain:feed ratio for cattle fed soybean hulls. Heifers fed soybean hull-based diets gained 29% slower (P < 0.05) and had 27% lower gain:feed ratios than heifers fed the corn-based diets. Cattle fed soybean hull-based diets had gains that were lower (P < 0.05) than those of cattle fed the roughage-based diets, but gain:feed ratios were similar because cattle were fed less of the soybean hull-based diets. Roughage-fed cattle had similar gains but 25% lower (P < 0.05) gain:feed ratios than cattle fed the corn-based diets. In Exp. 2, degradation by ruminal microbes of betaine in anhydrous betaine, betaine-HCl, feed-grade betaine, lipid-coated betaine, and CSB was evaluated in vitro using ruminal inocula collected from steers fed a high-grain or high-roughage diet. The roughage diet led to less betaine disappearance than the grain diet. More betaine was degraded from CSB than from other sources, perhaps because sugars provided by CSB stimulated fermentation, but no large differences occurred among the other four sources. Betaine from all sources was extensively degraded, although some betaine may escape ruminal degradation.

Animal Feed↗
PubMed2001

Tasco-Forage: II. Monocyte immune cell response and performance of beef steers grazing tall fescue treated with a seaweed extract.

Effects of applying Tasco-Forage, an Ascophyllum nodosum seaweed-based product prepared by a proprietary process, to endophyte (Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and endophyte-free tall fescue (Festuca arundinacea Schreb.) were studied in each of 3 yr (1995, 1996, and 1997) in Virginia and in 1996 and 1997 in Mississippi. There were 48 steers at each location in each year (n = 240) in a 2 x 2 x 2 factorial arrangement with two replications at each location. Steers in Virginia were Angus and Angus x Hereford with initial weights of 245 kg (SD = 20), 234 kg (SD = 9), and 265 kg (SD = 5) in yr 1, 2, and 3, respectively. Steers in Mississippi were 3/4 Angus and 1/4 Brahman and weighed 230 kg (SD = 8) and 250 kg (SD = 2) in yr 2 and 3, respectively. Tasco (3.4 kg/ha) was dissolved in water and applied to pastures in April before grazing was begun and again in July at the same rate. The grazing period was from mid-April to late September or mid-October. Total gains were higher (P < 0.05) for steers grazing uninfected than for those grazing endophyte-infected tall fescue. Rectal temperatures were increased (P < 0.05) due to endophyte infection at both locations; Tasco application decreased temperature of steers grazing infected fescue in Virginia (interaction, P < 0.07) but increased temperatures of steers grazing infected fescue in Mississippi (interaction, P < 0.05). Presence of the endophyte resulted in rough hair coats and loss of hair color, but the effect was partially offset (P < 0.05) by Tasco application in Virginia in 1995. Both monocyte phagocytic activity (all years and locations) and major histocompatibility complex class II expression (1995 only) were decreased (P < 0.05) in steers due to endophyte infection, but this effect was reversed (P < 0.05) by application of Tasco to pastures. Application of the extract from A. nodosum seems to have use in alleviating adverse effects of endophyte on immune function and may improve hair coat condition in cattle grazing infected fescue, but effects on rectal temperature varied due to location.

Animal Feed↗
PubMed2001

Tasco-Forage: IV. Influence of a seaweed extract applied to tall fescue pastures on sensory characteristics, shelf-life, and vitamin E status in feedlot-finished steers.

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 (antemortem) 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 < 0.05) CIE a* color scores throughout retail display. Steaks were more uniform and had less discoloration and less browning (P < 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 < 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 < 0.05). Vitamin E in liver was increased (P < 0.06) and serum vitamin E was decreased (P < 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.

Aging↗
PubMed2001

A comparison of native tallgrass prairie and plains bluestem forage systems for cow-calf production in the southern great plains.

The objective of this study was to compare an introduced warm-season perennial grass (plains bluestem, Bothriochloa ischaemum) to native tallgrass prairie for cow-calf production. Three systems were used, two based on tallgrass prairie with two different forms of protein supplementation and one based on plains bluestem as the primary forage. The systems were as follows: 1) native tallgrass prairie with pelleted oilseed meal as the winter protein supplement (native-control); 2) native tallgrass prairie with limited access to wheat pasture as the winter protein supplement (native-wheat); and 3) plains bluestem with limited access to wheat pasture as the protein supplement (bluestem-wheat). Oilseed meal protein supplements were fed twice weekly. Cows grazing wheat pasture were allowed 6 h of grazing twice weekly. Ninety-nine cows per year were used over the 3-yr study. Cows were sired by either Charolais, Gelbvieh, Angus, or Hereford bulls out of commercial Angus-Hereford dams. Calves were sired by Simmental bulls. Calving and weaning rate increased over time but did not differ among systems or breed types. System did not influence the size or body condition score of cows or the performance of calves, but changes in the weight and condition scores of cows were greater on either native system than on the bluestem-wheat system. Cows from Charolais and Gelbvieh bulls were taller (P < 0.05), and heavier (P < 0.05), and weaned heavier (P < 0.05) calves than cows from Angus or Hereford bulls. The weight of cows on the bluestem-wheat system tended to decrease over time, whereas cows grazing on the native systems tended to gain weight over time. The native-control system was the most profitable system based on cow production. If excess hay produced from the bluestem-wheat system was sold as a cash crop, then this system was the most profitable. In general, we conclude that limit-grazing wheat pasture is a viable alternative to oilseed meal as protein supplement for wintering dry cows. Although the bluestem system had 2.5 times the carrying capacity of the native prairie systems, increased productivity was offset by increased production costs. All systems were equal on a cow basis for providing nutrients for the cow-calf production system.

Animal Feed↗
PubMed2002

Energy requirement for maintenance and growth of Nellore bulls and steers fed high-forage diets.

Data from three comparative slaughter experiments with individually fed Nellore bulls (n = 31) and steers (n = 66) were utilized to determine their NEm and NEg requirements when fed high-forage diets. The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict NEm and NEg requirements. The Nellore bulls (Trial 1) were divided into two intake levels (ad libitum and 65% of the ad libitum). The steers (Trials 2 and 3) were allocated to three intake levels (ad libitum and 55 and 70% of the ad libitum). In both trials, there were three slaughter groups within each intake level. The three end points for the bulls were different days on treatment (100, 150, and 190 d and 130, 180, and 200 d, respectively, for older and younger animal subgroups). The steers were slaughtered when animals of the ad libitum treatment reached 400, 440, and 480 kg shrunk BW (SBW) on average for the first, second, and third group, respectively. For all body composition determinations, whole empty body components were weighed, ground, and subsampled for chemical analysis. In each of the trials, initial body composition was determined with equations developed from a baseline slaughter group, using SBW and empty BW (EBW), fat (EBF), and protein (EBP) as variables. The NEm was similar for bulls and steers; NEm averaged 77.2 kcal/ kg0.75 EBW. However, the efficiency of conversion of ME to net energy for maintenance was greater for steers than for bulls (68.8 and 65.6%, respectively), indicating that bulls had a greater ME requirement for maintenance than steers (5.4%; P < 0.05). Our analyses do not support the NRC (2000) conclusion that Nellore, a Bos indicus breed, has a lower net energy requirement for maintenance than Bos taurus breeds. An equation developed with the pooled data to predict retained energy (RE) was similar to the NRC (2000) equation. A second equation was developed to predict RE adjusted for degree of maturity (u): RE = (6.45 - 2.58/u) x EWG x e(0.469) x u), where u = current EBW/final EBW in which final EBW was 365 kg for steers and younger bulls and 456 kg for older bulls at 22% EBF, respectively.

Animals↗