Roughage Level Research Articles

Digestibilidade (aparente) de dietas com diferentes proporções de volumoso/concentrado fornecidas para ovinos

Avaliou-se a digestibilidade (aparente) de dietas com diferentes proporções de volumoso (feno de coastcross) e concentrado. O ensaio constou de quatro tratamentos: A= 40%, B= 60%, C= 80% e D= 100% de feno nas rações. Foram utilizados 12 carneiros, machos, castrados, que permaneceram em gaiolas metabólicas, arreados com bolsas para colheita total das fezes. O período de colheita durou 5 dias, durante os quais o consumo foi reduzido para 80% do obtido ad libitum. Os coeficientes médios de digestibilidade para os quatro tratamentos (A, B, C e D) foram: matéria seca (MS) - 68,11%, 63,92%, 59,22% e 64,60%; proteína bruta (PB) - 61,01%, 66,04%, 73,60% e 72,92%; fibra bruta (FB) - 52,56%, 53,66%, 56,22% e 57,19%; extrato não nitrogenado (ENN) - 74,40%, 69,63%, 58,56% e 70,40%; extrato etéreo (EE) - 71,49%, 59,21%, 57,90% e 57,98%, respectivamente. Os nutrientes digestíveis totais (NDT) foram: A= 62,15%, B= 57,72%, C= 52,04% e D=55,77%. As digestibilidades da matéria seca (MS) e do extrato não nitrogenado (ENN) apresentaram comportamento quadrático (p < 0,01). Os valores dos nutrientes digestíveis totais (NDT) não apresentaram diferenças significativas. Houve aumento linear (p < 0,01) na digestibilidade da proteína bruta (PB) e da fibra bruta (FB) com o aumento do volumoso na ração.

Performance by Pregnant Beef Cows Consuming Different Levels of Broiler Litter, Grain, and Roughag

Brangus-sired beef cows (100; 511 ± 4.4kg initial BW) were used to determine performance effects of different dietary levels of deep-stacked broiler litter, ground sorghum grain, and bermudagrass hay given in late gestation (63 d; 179 to 242 d of gestation). Treatments were hay consumed ad libitum (Control); 0.2% BW of sorghum grain, 0.1% BW of soybean meal (DM basis), and ad libitum consumption of hay (S); 0.2% BW of hay (DM basis) and ad libitum consumption of a 90% litter (harvested after two 6-wk broiler growing periods, 30% ash, 21% CP, and 49% NDF), 10% sorghum grain mixture (as fed basis; H); 0.2% BW of hay (DM basis) and ad libitum consumption of a 70% litter, 30% sorghum grain mixture (as fed basis; M-S); and 0.6% BW of hay (DM basis) and ad libitum consumption of an 87% litter, 13% sorghum grain mixture (as fed basis; M-B). Total DM intake was less (P<0.05) for H than for M-S and M-B (14.8, 15.9, 12.9, 18.1, and 17.2 kg/d for Control, S, H, M-S, and M-B, respectively). Likewise, cow BW change during the feeding period was less (P<0.05) for H vs M-S and M-B (1.25, 1.34, 0.65, 1.17, and 1.23 kg/d), although BW loss after feeding (43 d before and 62 d after calving) was lower (P=0.06) for H than for M-S and M-B (0.70, 0.71, 0.49, 0.75, and 0.75 kg/d for Control, S, H, M-S, and M-B, respectively). Calf birth weight and BW gain in the 62 d after calving were similar (P>0.10) among treatments. In conclusion, with sources of broiler litter such as this one, very low dietary levels of other feedstuffs can negatively affect cow BW change in late gestation via limited feed intake, although effects may be compensated for thereafter with adequate forage availability and quality. A moderate level of roughage (e.g., 0.6% BW; DM basis) in litter-based diets can support performance comparable to that with a moderate cereal grain level.

Digestibilidade (aparente) do farelo de soja e do feno “Coast-Cross” em dietas com diferentes proporções volumoso/concentrado, fornecidas para bovinos

O presente trabalho teve por objetivo avaliar a digestibilidade (aparente) do farelo de soja e do feno de “coast-cross" em diferentes proporções de volumoso: A = 40%: B = 60%; C = 80%; e D = 100%, de feno nas dietas. Os animais utilizados foram 8 bovinos, com peso médio de 200 kg, que permaneceram em gaiolas metabólicas. O período de coleta de fezes foi de 7 dias. Os coeficientes médios de digestibilidade foram: MS = 71,61%, 71,43%, 60,39% e 62,61%; PB = 73,32%, 78,12%, 73,55% e 74,34%; FB = 59,74%, 66,56%, 63,80 e 65,74%; ENN=75,95% 73,94%, 58,02% e 60,93%; EE = 72,90%, 70,84%, 61,04% e 63,30%, para os tratamentos A, B, C e D, respectivamente. Os valores de NDT foram: A = 63,13%; B = 62,20%; C = 54,96%; e D = 51,28%. As digestibilidades da MS, ENN e os valores de NDT aumentaram à medida que a proporção de concentrado era aumentada na ração (P &lt; 0,01).

Degradabilidade ruminal do farelo de soja e do feno de coast-cross, com bovinos fistulados em dietas com diferentes proporções volumoso/concentrado

Este trabalho teve por objetivo avaliar a degradabilidade ruminai da matéria seca (MS) e proteína bruta (PB) do farelo de soja e da MS e fibra detergente neutro (FDN) do feno de coast-cross, segundo a técnica de sacos de náilon in situ, em tratamentos com diferentes proporções de volumoso: A = 40%, B = 60%, C = 80% e D = 100% de feno. Os animais utilizados eram 16 bovinos machos, dotados de fístulas de rúmen, para os quais foram sorteados os quatro tratamentos, em dietas isonitrogenadas, dentro de um delineamento de blocos ao acaso. Quanto ao farelo de soja, a degradabilidade da MS com 24 horas de incubação no rúmen aumentou linearmente (p&lt; 0,05), à medida que se elevou a quantidade de volumoso na dieta e variou de 77,9% a 88,1%, enquanto a PB não apresentou diferenças significativas nos diversos intervalos de tempo e variou de 81,7% a 90,4%, com 24 horas de incubação. Quanto ao feno, as degradabilidades da MS e FDN apresentaram menores valores (p &lt; 0,01) no tratamento com menor nível de volumoso na ração (40%). O número de protozoários total no fluido do rúmen mostrou uma regressão quadrática (p &lt; 0,01), sendo o menor valor referente ao tratamento com 40% de volumoso.

Roughage Source and Level in Beef Cattle Finishing Diets

Three experiments were conducted to evaluate the effects of roughage level and source in beef cattle finishing diets. In Exp. 1,228 crossbred beef heifers (initial BW=346kg) were fed diets containing 7.5 or 15% roughage (DM basis), with alfalfa hay, sudangrass hay, or cottonseed hulls as roughage sources. Daily gain was not affected (P>0.10) by roughage level, but DMI was increased (P<0.10) with 15 vs 7.5% roughage. Among roughage sources, daily gain was less (P<0.05) with alfalfa than with cottonseed hulls or sudangrass. Dry matter intake was greater (P<0.05) with sudangrass than with alfalfa and intermediate with cottonseed hulls. Feed:gain did not differ (P>0.10)among roughage sources, but heifers fed alfalfa were least efficient. In Exp. 2, 224 crossbred beef steers (initial BW=308kg) were fed 90% concentrate diets with either whole-shelled or steam-flaked com as grain sources and either alfalfa hay or sudangrass hay as roughage sources. Daily gain was not affected by grain source, but DMI and feed:gain were greater (P<0.01) with whole-shelled than with steam-flaked com. Similarly, gain did not differ (P>0.10) between sudangrass and alfalfa, but steers fed sudangrass had greater (P<0.02) DMI and were less efficient (P<0.03) than those fed alfalfa as the roughage source. In Exp. 3, 132 crossbred steers (initial BW=313kg)were used in a randomized block design with different roughage sources and levels, including: alfalfa hay at 10% of dietary DM or sudangrass hay at 5, 7.5, and 10% of dietary DM. Daily gain was greater (P<0.06) with diets containing sudangrass than with the alfalfa diet, but level of sudangrass did not affect (P>0.10) daily gain. Daily DMI was increased (P<0.03) for diets with sudangrass vs alfalfa, and responded quadratically (P<0.11) to sudangrass level, with maximum DMI at 7.5% sudangrass. Feed:gain did not differ between the roughage sources but increased linearly (P<0.11) with increasing level of sudangrass. These results indicate that roughage level and source alter DMI and performance by finishing beef cattle. Sudangrass hay consistently increased DMI relative to alfalfa hay in high-concentrate beef cattle finishing diets, but responses in daily gain and feed efficiency were not consistent between these two roughages. Further research is needed to characterize the relationship between chemical and physical characteristics of roughages and finishing beef cattle performance.

The effect of diet and frequency of watering on the performance of growing cattle given food at maintenance

AbstractAn 18-week experiment investigated the effects of type of diet and frequency of watering on the performance of growing cattle given food at maintenance (metabolizable energy (ME) allowance (MJ) = 8·3 + 0·091 M where M = live weight of the animal). Three diets with 20: 80 (low, L), 50:50 (medium, M) and 80: 20 (high, H) roughage to concentrate ratios (10·2, 7·8 and 5·4 MJME per kg dry matter) were used in combination with free access to water for 2·5 h once daily or once every 3rd day. A completely randomized-block design with a 3 (diets) × 2 (watering frequencies) factorial arrangement of treatments was used. Five animals were allocated per treatment (average weight 245 (s.d. 21·6) kg).Dry-matter intake increased as the roughage content of the diet increased (P &lt; 0·05) but was not affected by the watering regime (P &gt; 0·05). Total water intake was found to be positively correlated with dry-matter intake and increased with dietary roughage level. Animals watered daily drank more (P &lt; 0·05) water (12·6 v. 10·0 kg/day) than those watered every 3rd day. The apparent digestibility of the diets decreased as the amount of roughage increased (diet L 734g/kg, M471 g/kg and H 433 g/kg). Similar apparent digestibilities were observed under the two watering frequencies (546 g/kg and 547 g/kg).Type of diet significantly (P &lt; 0·05) affected the final weights of the steers. Animals given diet H were proportionately 0·07 heavier than those offered diet L corresponding to total weight changes of −0·8 and +18·4 kg respectively. Carcass weight, backfat thickness and eye muscle area were not affected by the treatments. The chemical composition of the 9 to 11th rib joint was only affected by diet H which gave less fat (P &lt; 0·05). Water, fat, protein and ash content averaged 607,118,190 and 84 g/kg respectively.

Effects of the nature of roughage and concentrate and their proportion on ruminal characteristics of non lactating goats, consequences on digestive interactions

The effects on ruminal characteristics of 14 diets differing in nature and level of roughage and concentrate have been studied. The roughages were alfalfa hay (AH) or maize stover silage (MS) distributed alone or in a mixed diet containing 30 or 60% concentrate on a dry matter basis. Three types of concentrate were formulated to be either rich in rapidly degradable starch (RS), slowly degradable starch (SS) or digestible fibre (DF). The post feeding evolutions of pH, volatile fatty acids (VFA) and ammonia (NH 3) concentrations in ruminal fluid were measured. Microbial protein synthesis has been estimated. Ruminal pH was consistently high (pH > 6.3) and VFA concentrations in the rumen were 88.4 mmol L −1. VFA concentrations were higher after AH compared with MS, whereas differences between concentrates were not significant. The proportion of acetate decreased with the concentrate level while that of propionate increased. The NH 3 concentration was always over 50 mg L −1 and varied significantly with the tested diets. The efficiency of microbial nitrogen synthesis (EMS) was 32.7 g per kg of organic matter apparently digested in the rumen without significant differences between roughages or concentrates. No difference ( P < 0.05) was observed between the depressive effect of concentrates on the cellulolysis in the rumen.

Effect of heat stress and dietary roughage level on rumen function, nutrient utilization and water turnover by native Egyptian sheep

Effect of heat stress and dietary roughage level on rumen function, nutrient utilization and water turnover by native Egyptian sheep

Dietary energy source and density: effects of roughage source, roughage equivalent, tallow level, and steer type on feedlot performance and carcass characteristics

The effects of roughage level (10, 20, or 30% roughage equivalent [RE]), roughage source (alfalfa vs cottonseed hulls), roughage regimen (constant RE vs 2% RE during the mid-finishing period), tallow level (1.2 vs 4.6%), and steer type (British crossbred [BRITX] vs Bos indicus crosses [BRX]) were evaluated in three experiments with a common allotment and several overlapping treatments. Steers (n = 432; initial weight = 326 +/- 26 kg) were divided into three BW blocks and allotted randomly to 72 pens and 24 treatments. Steers were fed steam-flaked, sorghum grain-based finishing diets for 124 to 166 d. Diets with 20% RE decreased gain efficiency and 30% RE diets decreased both gain (linear, P < .07) and efficiency (linear, P < .001) compared with 10% RE diets. Reducing roughage level during the mid-finishing period improved overall gain efficiency 2, 7, and 24% (P > .2, < .05, and < .001, respectively) for the 10, 20, and 30% RE diets, respectively. Steers fed cottonseed hulls consumed more feed (9.6 vs 8.8 kg/d, P < .001) but tended to gain less (1.53 vs 1.58 kg/d, P = .11) than steers fed alfalfa, were leaner, and had fewer carcasses grading Choice (62 vs 77%, P < .05). Feeding 4.6% tallow decreased DMI (P < .05) and improved gain efficiency (P < .05) compared with 1.2% tallow. The BRITX steers consumed more feed (6%, P < .001) but were somewhat less efficient (3.5%, P < .05) than BRX steers. Carcasses from BRITX steers tended to be fatter than carcasses from BRX steers and more of them graded Choice (62 vs 37%, P < .01). Commercial BRX steers did not perform as well as BRITX steers on higher-energy-density diets (4.6% tallow or variable roughage regimen). Knowledge of the genetic background of feeder cattle can be important in the selection of dietary energy density and marketing expectations.

Roughage level and corn processing infinishing diets: subacute acidosis (1994)

Roughage level and method of corn processing were evaluated for the propensity to cause subacute acidosis in a controlled acidosis challenge model. Four ruminally fistulated steers were adapted to a high grain diet, randomly allocated within a 4 x 4 Latin square, and fed a corn-based finishing ration at 2% of BW/day (dry basis) in two equal feedings. Chopped alfalfa hay was used as the roughage source and added at 8% of the diet dry matter or not added. Corn was fed either whole (WSC) or dry rolled (DRC). Roughage level and grain processing had no effect on postchallenge molar percentage of acetate or total volatile fatty acid production. An interaction (P<.05) was seen in both percent propionate and acetate:propionate ratio. Eliminating roughage in the WSC diet resulted in increased production of propionate and a lower acetate:propionate ratio. Ruminal pH at 3 hours postchallenge and intake during the recovery period were lower (P<.05) for 0 vs 8% roughage. Ruminal pH at 3 and 6 hours postchallenge was lower (P<.05) for DRC than for WSC. Intake during the recovery period did not differ between DRC and WSC. Hours below pH 5.6 were greater (P<.05) for DRC vs WSC and for 0 vs 8% roughage. Though statistically higher (P<.05), no biologically significant levels of lactate were found for either DRC or WSC. This study indicates that adding roughage or feeding WSC vs DRC reduces the propensity for subacute acidosis.

Roughage levels and comparison of mixed rations vs self-feeders in whole shelled corn finishing programs (1994)

Two trials were conducted to evaluate roughage levels in whole shelled-corn finishing diets and to compare use of self-feeders to a total mixed ration in a whole corn program. In trial 1, steers were fed whole corn diets alone or with 4 or 8% roughage or a rolled corn diet with 8% roughage. Increasing the roughage level increased dry matter in take, feed required per unit of gain, and carcass weight and finish, and reduced the incidence of liver abscesses. Despite better feed efficiency and lower costs of gain, reducing the dietary roughage level reduced profitability because of lighter slaughter weights. In trial 2, feeding 4% vs no roughage in a whole-corn finishing program increased dry matter intake and tended to increase rate of gain by finishing heifers. No performance benefit resulted from feeding a total mixed ration vs using self-feeders and providing chopped hay in a feed bunk. Feeding very little or no roughage in whole corn diets can improve feed efficiency and reduce cost of gain. However, these advantages can be outweighed by potentially lower slaughter weights and increased metabolic problems (acidosis, bloat, liver abscesses).

Effect of dietary roughage levels all the lactation performance of Egyptian goats

Effect of dietary roughage levels all the lactation performance of Egyptian goats

Roughage level and limited maximum intake regimens for feedlot steers.

Hereford steers (n = 280, BW = 371 +/- 29 kg; 40 pens) were used to evaluate two alternatives to ad libitum access to feed and constant roughage levels in finishing diets. The eight treatments were as follows: two treatments in which intake was limited to a multiple of the maintenance (MM) energy requirement (2.1, 2.3, 2.5, and 2.7, [2.7MM] and 2.3, 2.5, 2.7, and 2.9 [2.9MM] times maintenance for wk 1, 2, 3, and 4 and thereafter, respectively) and six roughage regimen and grain source treatments (10% roughage equivalent [RE] fed during the mid- and late-finishing periods [10/10], respectively, 2% RE followed by 10% RE [2/10], and 10% RE followed by 2% RE [10/2] fed with steam-flaked sorghum grain [SFSG] or whole-shelled corn [WSC]). The 2.7MM treatment tended to improve ADG (6%, P = .08) and gain efficiency (4%, P = .15) relative to ad libitum access to feed. The 2.9MM treatment was intermediate. Steers fed WSC diets consumed approximately 12% more DM (9.2 vs 8.2 kg/d) and gained 4% more (1.45 vs 1.39 kg/d, P < .05) but had lower gain efficiency (7%, 159 and 170 g/kg, P < .001) than steers fed SFSG diets. For SFSG diets, the 2/10 regimen resulted in similar gains, a 3.6% decrease (P = .10) in DMI, an 8.6% improvement (P < .01) in gain efficiency, and reduced roughage use (40 kg per steer) compared with the 10/10 regimen. With WSC diets, the 2/10 regimen did not (P > .2) affect gain efficiency but did reduce roughage use (48 kg) compared with the 10/10 regimen. The 10/2 regimen did not differ (P > .2) from the 10/10 regimen. Few differences in carcass characteristics were noted among treatments. Roughage use and cost of gain can be reduced by feeding 2% roughage during the mid-finishing period followed by a return to 10% roughage.

Density of steam-flaked sorghum grain, roughage level, and feeding regimen for feedlot steers.

Two hundred fifty-two steers (366 kg) were assigned to a 3 x 2 x 2 factorial arrangement of three densities of steam-flaked sorghum grain (bulk [flake] density of 437, 360, and 283 g/liter, B34, B28, and B22, respectively), two roughage levels (9 [R9] and 18% [R18]) and two feeding strategies (ad libitum [AD] or multiple of maintenance [MM], 2.3, 2.5, and 2.7 MM for wk 1, 2, and 3, and 2.9 MM thereafter). Steers fed R18-AD gained faster than steers fed R18-MM (1.59 vs 1.52 kg/d, P = .10); for R9 diets, no difference (P greater than .25) was found between steers fed AD and MM (interaction, P = .07). Flake density did not affect ADG (1.53 kg, P greater than .2). Dry matter intake decreased (9.8, 9.3, and 9.0 kg/d, linear, P less than .001) and gain efficiency (G/DMI, kg of gain/100 kg of DMI) increased (15.7, 16.5, and 16.9, linear, P less than .001; quadratic, P = .19) as processing degree increased (B34 to B22). Percentage of choice carcasses for B34 (67.0%) was higher (linear, P = .05) than for B28 (51.9%) and B22 (52.3%). Fecal starch and pH were 10.8, 5.7, and 4.0%, and 6.11, 6.23, and 6.37 for B34, B28, and B22, respectively (linear, P less than .001). The correlation between fecal starch and pH was -.51 (P less than .001, n = 252). Enzymatic glucose release, in vitro 6-h gas production, microbial protein synthesis, and protein degradability were 375, 483, and 559 mg/g; 24.7, 28.2, and 31.1 ml/.2 g; 6.15, 6.88, and 7.84 g/100g; and 61.4, 56.6, and 42.2% for B34, B28, and B22, respectively (linear, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of grain type, roughage level and monensin level on finishing cattle performance.

Interactions among grain type (grain sorghum, corn or wheat), roughage level and monensin level were studied in four feedlot trials using pen-fed crossbred yearling cattle. In Trial 1, cattle fed high-moisture corn (HMC) were more efficient (.1537 vs .1406 for gain/feed; P less than .01) than cattle fed dry-rolled grain sorghum (DRGS). As level (0, 3, 6, 9%) of dietary roughage was increased, feed efficiency (gain/feed) decreased (.1566, .1461, .1479, .1382; linear, P less than .01). In Trial 2, a grain type (DRGS; dry-rolled corn, DRC; dry-rolled wheat, DRW) x roughage level interaction was observed for daily gain and feed efficiency. Feed efficiency (gain/feed) was decreased when roughage was added to diets containing DRC (.1608 vs .1750) or DRGS (.1674 vs .1465), but not to the diet containing DRW (.1664 vs .1607). In trial 3, a grain type x roughage level x monensin level interaction (P less than .08) was observed for feed efficiency. The addition of 27.5 mg of monensin per kilogram of the 0% roughage-DRC diet tended to improve feed efficiency (.1633 vs .1531), but the addition of monensin to the 7.5% roughage-DRC diet tended to depress feed efficiency (.1476 vs .1575). The addition of either roughage (.1493 vs .1420) or monensin (.1500 vs .1413) to the DRW diet improved feed efficiency. In Trial 4, cattle fed a combination of 75% DRW and 25% DRC were more efficient (.1618 vs .1591; P less than .06) than cattle fed DRC. As level of roughage (0, 3.75, 7.5%) increased, feed efficiency decreased linearly (.1645, .1599, .1569; P less than .0001). Monensin had no effect on feed efficiency. The value of feeding roughage and monensin was variable both across grain types and within similar grain types.

The flow of undigested corn residues through the gastrointestinal tract of cattle.

Two experiments were conducted to measure effects of source and level of roughage on the flow of corn residues through the gastrointestinal tract of cattle. In Exp. 1, steers (195 kg) were fed diets of ground corn with 0, 30 or 60% of ground Coastal bermudagrass hay (Cynodon dactylon) [L.] Pers.) at intakes of 1, 1.5 or 2% of BW in a 9 x 9 Latin square. Experiment 2 consisted of two 4 x 4 Latin squares with either rice hulls (square 1) or ground Coastal bermudagrass hay (square 2) providing 0, 7.5, 15 or 30% of the total diet fed at 1.5% of BW. After a 28-d adjustment period, a portion of the corn in one meal was replaced with cracked corn stained with brilliant green. The concentrations of stained corn residues appearing in the feces subsequent to dosing were fitted to a one-compartment, age-dependent model and compartmental mean residence time (CMRT) and time delay (tau) were estimated. In Exp. 1, increasing the level of intake of the ration from 1% to 1.5 or 2.0% of BW increased (P less than .05) CMRT by 52% and reduced (P less than .05) tau by 41%. In Exp. 2, source of roughage had no effect (P = .95) on CMRT or tau. Combined results of the two experiments indicated that increasing proportion (P) of either roughage was associated with an exponential decline in CMRT of stained corn residues (CMRT = 1211 * e-.0315P) from rations consumed at 1.5 and 2.0% of BW. No consistent effect of roughage type or proportion was noted on time delay in the two experiments collectively. These results indicate that increasing the proportion of roughage in the diet exponentially reduces residence time of corn residues in the ruminoreticulum (CMRT) without affecting residence time in the postgastric segments (tau).

HIGH-ROUGHAGE RATIONS WITH OR WITHOUT MONENSIN FOR VEAL PRODUCTION. I. ANIMAL PERFORMANCE

Eighty-four calves 11–12 wk old (88 ± 10 kg BW) were used in a 47-d trial to study the effects of two ground roughages (alfalfa and timothy), their proportions in pelleted rations (20, 40 and 60%) and addition of monensin (0 and 33 ppm) on animal performance. After the trial, the animals continued to consume the rations until they reached a slaughter weight of 185 kg. Calves fed rations containing timothy showed higher dry matter (DM) and digestible energy (DE) intake and higher average daily gains (ADG) than calves fed rations containing alfalfa, which was partially due to the quality of the protein used to supplement the timothy rations. Proportion of roughage did not affect DM intake with the exception of 60% alfalfa rations which had the lowest intake. Increasing the roughage in the rations reduced DE intake and ADG, and increased feed conversion values (FC), particularly at 40 and 60%. Monensin increased DE intake and FC of rations containing 40 and 60% timothy, but had no effect on DM intake or ADG. Monensin increased DE conversion values when roughages were added at levels of 40 and 60%, the effect being greater with timothy. Dressing percentage of carcasses decreased with increasing levels of roughage in the ration, the lower values being obtained with timothy. Carcass classification and color of the meat were unaffected by the treatments. Key words: Alfalfa, timothy, roughage level, monensin, calf

HIGH-ROUGHAGE RATIONS WITH OR WITHOUT MONENSIN FOR VEAL PRODUCTION. II. RATION DIGESTIBILITY

Thirty-six calves 19–20 wk old (149 ± 17 kg) and forty-eight rams (46 ± 4 kg) were used in two experiments to study the effects of two ground roughages (alfalfa and timothy), their proportion in pelleted rations (20, 40 and 60%) and addition of monensin (0 and 33 ppm) on ration digestibility. Calves and rams were fed the test rations ad libitum for a period of 8 and 5 wk, respectively, before the digestibility trial. Dry matter (DM) digestibility in both species and energy digestibility in calves were significantly higher for the rations containing alfalfa than for those containing timothy; however, digestibility of crude protein (CP) in both animal species and of cell walls (NDF) in calves was lower in alfalfa rations. The two trials revealed an increase in digestibility of acid detergent fiber (ADF) and of cell wall (NDF) fractions but a reduction in DM digestibility when the roughage content in the rations increased; the reduction in DM digestibility was larger with timothy than with alfalfa. Addition of monensin did not affect digestion coefficients of DM, ADF and NDF in calves and rams on average. However, a monensin × roughage level interaction indicated a decrease of ADF and NDF digestibility in calves fed 20% roughage and an increase of ADF and NDF digestibility in calves fed 60% roughage. Key words: Alfalfa, timothy roughage level, monensin, calf, sheep

INFLUENCE OF HIGH-MOISTURE BARLEY ON THE PERFORMANCE AND CARCASS CHARACTERISTICS OF FEEDLOT CATTLE

Three factorial experiments were conducted to determine the relative feeding value of dry barley (DB) and high-moisture barley (HMB), and to evaluate the influence of method of ensiling (Pit vs. Harvestore® (HAV) silo), source of roughage (hay vs. silage), and level of concentrate (90 vs. 75%) on the performance and carcass characteristics of feedlot cattle. In exp. 1, 252 steers (initial wt 357 kg) were assigned on the basis of weight to six treatments (two pens × 21 animals per pen). A mixed diet consisting of 85.2% barley grain (dry matter (DM) basis) was offered free choice. The barley portion of the ration consisted of either 0, 25, 50, 75 or 100% DB with the balance being HMB from a pit silo. The sixth treatment consisted of feeding 100% HMB for the first 57 d and 100% DB for the remainder of the trial. Overall average daily gain (ADG) for steers fed 100% DB (1.70 kg d−1) was significantly higher than observed for animals fed 100, 75 or 50% HMB (1.46, 1.49 and 1.56 kg d−1, respectively). The kg of feed DM required per kg gain (FC) varied between 5.76 and 7.13 and was not (P &gt; 0.05) influenced by treatment. No differences (P &gt; 0.05) were observed in carcass characteristics. In exp. 2, 360 steers (initial wt 340 kg) were allotted on the basis of weight to six treatments designed to evaluate the effect of source (Pit vs. HAV) and level of HMB, in diets containing 10.2% silage, on animal performance. Overall ADG (1.11 – 1.17 kg d−1), FC (6.66 – 7.01) and carcass characteristics were similar (P &gt; 0.05) for animals fed Pit HMB, HAV HMB and DB. In exp. 3, 264 weanling calves (initial wt 216 kg) were allotted on the basis of weight to six treatments which differed in type of barley (HMB vs. DB), source of roughage (hay vs. silage) and level of concentrate (75 vs. 90%; DM basis). The feeding period was 127 d. Daily gains varied between 0.78 and 0.91 kg d−1 and FC ranged from 6.40 to 7.10 and were not influenced (P &gt; 0.05) by source of barley or source or level of roughage. While animals fed DB had significantly higher ADG than those fed HMB in exp. 1, the overall results from the three experiments indicate that on a DM basis HMB has similar feeding value to DB, and that there is no major difference between Pit and HAV-stored HMB for feedlot cattle. Key words: High moisture, barley, cattle, gain, feed conversion

INFLUENCE OF IONOPHORE ADDITION TO ROUGHAGE AND HIGH-CONCENTRATE DIETS ON PORTAL BLOOD FLOW AND NET NUTRIENT FLUX IN CATTLE

Two experiments using cattle with chronic hepatic-portal and arterial catheters were conducted to investigate effects of ionophore addition to roughage and high-concentrate diets on net nutrient flux across portal-drained viscera. Monensin and salinomycin added to a high-concentrate diet fed to three beef heifers in a Latin square design (exp. 1) increased the net portal flux of propionate (P &lt; 0.05) and glutamate (P &lt; 0.05) with a tendency for increased portal blood flow. Two beef steers (exp. 2) were fed alfalfa with monensin (300 mg d−1) for 22 d prior to dietary monensin and samples were taken on days −3, 0, 1,2, 4, 9, 16, 32, and 35 relative to monensin removal. Portal blood flow and gut oxygen consumption decreased (P &lt; 0.05) following monensin removal until day 9, then remained relatively constant. Use of glucose by portal-drained viscera decreased (P &lt; 0.05) until day 16, then returned towards initial values, while net appearance of L-lactate decreased linearly (P &lt; 0.05). After monensin removal from the diet, the net portal flux of L-lactate, ammonia-N, acetate, propionate, isobutyrate, and 3-methylbutyrate were reduced (P &lt; 0.05). These reductions were largely the result of decreased portal blood flow. In both experiments, dietary ionophores affected net flux across portal-drained viscera for several metabolites. These changes may differ, however, with roughage level and ionophore fed. Key words: Bovine, ionophore, absorption, blood flow