Nutrient utilization by sheep fed forage grown on soil treated with fluidized-bed combustion residue.

A mineral balance trial was conducted with 18 wether lambs fed sun-cured hay harvested from pastures located on a reclaimed strip-mined site. The following soil applications were made during each of 3 yr: 1) none, 2) dolomitic limestone and 3) fluidized-bed combustion residue (FBCR). Because FBCR had half the buffering capacity of limestone, it was applied at twice the rate of limestone. Apparent digestibility of hemicellulose was higher (P less than .05) for limestone-amended forage than for FBCR-amended forage (70.2 vs 67.0%), and apparent digestibility of cellulose was higher (P less than .05) for amended forages (66.7%) than for the control (63.9%). Apparent absorption and retention of N were similar among treatments, when expressed as a percentage of intake. Lambs fed control forage were in negative Ca balance, lower (P less than .01) than with amended forages. Apparent absorption and retention of Mg and Fe (g/d basis) were higher (P less than .05) for lambs on the limestone treatment than for lambs on the FBCR treatment. Apparent absorption of S was higher (P less than .01) for lambs on the FBCR treatment than for those on the limestone treatment. These differences were related to differences in mineral concentrations of the forages. Serum P was lower (P less than .05) for lambs fed FBCR-treated forage than for lambs fed limestone-treated forage (10.1 vs 12.9 mg/dl). Soil amendment with FBCR did not have deleterious effects on digestibility or mineral metabolism; in fact, it may have enhanced utilization of Ca and S and improved digestibility of some fiber components by lambs.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 1. Fescue and clover hays

Five crossbred beef cows (Hereford X Angus, 422 kg) with ruminal and duodenal cannulae were used in a Latin square experiment to determine the effects of dietary proportions of fescue and clover hays (0:1, .25: .75, .5:.5, .75:.25 and 1:0) on digestive function. Feed intake was 85% of ad libitum intake of fescue alone (1.03% of body weight). Fescue contained 1.26% nitrogen (N), 71.0% neutral detergent fibre (NDF) and 7.6% acid detergent lignin (ADL), and clover contained 2.43% N 50.0% NDF and 5.8% ADL in DM. Ruminal fluid ammonia-N concentration increased linearly (P less than .05) with declining dietary fescue level. Total concentration of volatile fatty acids in ruminal fluid and duodenal and rectal digesta mean particle size were not affected by fescue level. Ruminal fluid volume and flow rate increased linearly (P less than .05) with increasing dietary fescue, but fluid and particulate digesta passage rates were unchanged. Apparent ruminal organic matter (OM) digestion decreased quadratically (P less than .05) as fescue increased (74.5, 54.3, 49.8, 46.2 and 42.4% for 0, 25, 50, 75 and 100% fescue, respectively). Postruminal OM digestion as a percentage of intake was partially compensatory, increasing linearly (P less than .05) as dietary fescue level rose (2.3, 3.5, 5.1, 8.6 and 11.1% of intake). Thus, total tract OM digestion declined less as fescue replaced clover (76.8, 57.8, 55.0, 54.8 and 53.5%; linear and quadratic, P less than .05) than did apparent ruminal OM disappearance. Changes in ruminal NDF, acid detergent fibre and cellulose digestibilities were similar to those for OM. Microbial growth efficiency increased quadratically (P less than .10) as fescue intake increased. These results indicate that with low feed intake, ruminal and total tract digestion of an all-legume hay diet is greater than that of a grass hay diet. Little or no digestive advantage was achieved by substituting clover for fescue, except in the case of total replacement of fescue with clover, because of concurrent decreases in microbial growth efficiency, microbial N flow to the intestines and OM digestion in the postruminal tract. Negative associative effects in digestion observed between clover and fescue hays in this experiment deserve further study.     

Nitrogen balance in lambs fed low-quality brome hay and infused with differing proportions of casein in the rumen and abomasum

Twenty wether lambs (46 +/- 2 kg) fitted with ruminal and abomasal infusion catheters were used in a completely randomized design to determine the effects of differing proportions of ruminal and abomasal casein infusion on N balance in lambs fed low-quality brome hay (0.8% N, DM basis) for ad libitum intake. Wethers were infused with 0 (control) or 10.7 g/d of N from casein with ratios of ruminal:abomasal infusion of 100:0 (100R:0A), 67:33 (67R:33A), 33:67 (33R:67A), or 0:100% (0R:100A), respectively, over a 12-d period. Total N supply (hay N intake + N from casein infusion) was greater (P = 0.001) in lambs receiving casein infusion than in controls. Urinary N excretion (g/d) was greater (P = 0.001) in lambs receiving casein infusion than in controls. Urinary N excretion decreased as casein infusion was shifted from 100R:0A to 33R:67A and then slightly increased in lambs receiving 0R:100A (quadratic, P = 0.02). Total N excretion was greater (P = 0.001) in lambs receiving casein infusion than in controls and decreased linearly (P = 0.005) as casein infusion was shifted to the abomasum. Retained N (g/d, % of N intake, and % of digested N) was greater (P = 0.001) in lambs receiving casein than in controls. Retained N increased as infusion was shifted from 100R:0A to 33R:67A and then slightly decreased in lambs receiving 0R: 100A (quadratic, P < 0.07). Based on regression analysis, the predicted optimum proportion of casein infusion to maximize N retention was 68% into the abomasum. The regression suggests that supplementation with undegradable intake protein had an additional benefit over supplementation with ruminally degradable intake protein (100R:0A) and that changing the percentage of ruminally undegradable intake protein in supplemental protein from 33 to 100% resulted in minimal differences in N retention. Apparent N, DM, OM, and energy digestibility (% of intake) was greater (P < 0.03) in lambs infused with casein than controls but did not differ among casein infusion groups. These data suggest that feeding protein supplements containing a portion (greater than 0%) of the crude protein as ruminally undegradable intake protein, as compared to 100% ruminally degradable intake protein, to lambs consuming low-quality forage increases N retention and the efficiency of N utilization without influencing total-tract nutrient digestion.     

Effects of increasing crude protein level on nitrogen retention and intestinal supply of amino acids in lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw.

The effects of increasing dietary CP level on N retention (Exp. 1) and intestinal supply of amino acids (AA; Exp. 2) were studied in lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw (AHPWS). Soybean meal (SBM) was substituted for corn to increase CP level in both experiments. In Exp. 1, an incomplete design for the two-way elimination of error was used to allot 24 ram lambs (mean BW = 25 kg) within breed to six CP levels (6, 8, 10, 12, 14, and 16% of DM). Neutral detergent fiber digestibility and N retention increased quadratically (P = .06 and P less than .01, respectively) with increasing CP level. Nitrogen retention, expressed as a percentage of N intake, was greatest for lambs fed 12% CP (20.7%) but was greatest for lambs fed 14% CP when expressed as grams per day (4.0 g/d). In Exp. 2, five multicannulated St. Croix lambs (34 kg) were used in a 5 x 5 Latin square design. Treatments were 8.5, 11, 13.5, 16, and 18.5% dietary CP. Chromic oxide was used as a digesta flow marker and purines were used as a bacterial marker. Protein level had no effect on extent of dietary CP degradation in the rumen (69 +/- 3.2%). True ruminal OM digestibility increased (P less than .01) linearly and ruminal fluid NH3 N concentration increased (P less than .01) quadratically with increasing CP level. Total, bacterial, and nonbacterial N and AA flows to the duodenum increased (P less than .05) linearly with increasing CP level. Duodenal AA profile (g/100 g total AA) was altered slightly. The essential AA valine, isoleucine, phenylalanine, lysine, and arginine increased (P less than .05) and methionine decreased (P less than .05) in proportion to other AA with increasing CP level. Flows of all essential AA increased with increasing CP level. Apparent small intestinal N and AA disappearance increased linearly (P less than .05) and apparent total tract N digestibility increased (P less than .01) quadratically with increasing CP level. These data are interpreted to indicate that maximal N retention and fiber digestibility in diets based on AHPWS are obtained at 12% CP, even though the intestinal supply of AA continues to increase with increasing CP level. Supplementation of diets based on AHPWS with an extensively degraded protein source (SBM) does not substantially alter the profile of AA entering the duodenum compared to the AA profile of bacterial protein.     

Digesta flows in sheep fed poor-quality hay supplemented with urea and carbohydrates

Two metabolism trials were conducted with 12 yearling crossbred wethers per trial (34 and 38 kg for trials 1 and 2, respectively). The wethers, equipped with ruminal, abomasal and ileal cannulae, were randomly allotted for each trial to the following treatments: 1) hay alone or hay supplemented with 2) .9% urea, 3) 1% urea and 6.5% molasses or 4) 1% urea and 5.2% corn. Two digestive flow markers were used: Cr2O3 powder and Co-ethylenediaminetetraacetic acid (Co-EDTA). Urea and Co-EDTA were infused continuously into the rumen via cannula. Daily dry matter (DM) intake averaged 517 g. Urea supplementation improved N retention (P less than .01). Apparent digestibility of DM, acid detergent fiber (ADF) and energy was not affected by treatment. Urea and carbohydrate supplementation increased ruminal propionic acid molar proportions (P less than .05). Apparent ruminal DM digestion accounted for 41% of the total DM degraded, whereas 77.4% of the digestible ADF was degraded in the rumen. Urea supplementation increased ADF digestion in the large intestine (P less than .01). Urea and carbohydrate supplementation resulted in a stepwise increase in N flowing with the liquid phase at the abomasum. Mean retention times of the solid and liquid phases of digestive contents were similar across treatments. Overall, benefits of supplementation of poor-quality fescue hay diets by small amounts of urea and readily available carbohydrates remain questionable for sheep fed at a fixed level of intake below maintenance.     

Influence of limestone level in high concentrate and high roughage diets on site and extent of digestion in lambs

Two digestion and slaughter trials were conducted to evaluate the influence of limestone level on site and extent of digestion and rumen fermentation in lambs. In trial 1, 11 wether lambs (avg wt 40.7 kg) were fed 75% concentrate diets supplemented with .6, 1.5 or 3.0% limestone (.6,1.2,1.7% dietary Ca, respectively) in a completely randomized design. Dry matter intake increased linearly (P less than .10) with limestone level; therefore, other data were analyzed with dry matter intake as a covariate. Total tract organic matter digestion decreased linearly (P less than .05) with increasing limestone but dry matter and fiber digestion were not affected by limestone. Ruminal digestion of dry matter and organic matter declined linearly (P less than .05) with increasing limestone. Ruminal neutral detergent fiber (NDF) digestion was higher with the 1.5 than the .6 and 3.0% limestone diets (quadratic effect, P less than .05) but ruminal digestion of other fiber components was not affected by limestone. Ruminal volatile fatty acids were not affected by limestone level; however, rumen ammonia concentrations decreased linearly (P less than .05) with increasing limestone level. In trial 2, 12 wether lambs (avg wt 43.3 kg) were fed a 35% concentrate diet with .1, 1.5 or 3.0% limestone (.5, 1.2 and 1.6% dietary Ca, respectively) in a completely randomized design. Dry matter intake was not affected by limestone level, but digestibility of dry matter, organic matter and starch (P less than .10), energy, crude protein, acid detergent fiber (ADF) and cellulose (P less than .05) responded quadratically to limestone level, with increases at the 1.5% limestone level. Ruminal dry and organic matter (P less than .05), NDF (P less than .10), ADF (P less than .01), cellulose (P less than .05) and starch (P less than .05) digestion responded quadratically to limestone level with higher values at the 1.5% limestone level. Proportions of ruminal propionate increased linearly (P less than .01) with increasing limestone level and acetate: propionate ratio declined linearly (P less than .01) with limestone level.     

Physiological effects of feeding high levels of magnesium to sheep

The effects of feeding high levels of Mg to sheep on animal health, nutrient digestibility, metabolism of macro-minerals, blood and tissue mineral concentrations and hematological and histological tissue changes were evaluated. Six lambs were allotted to each of four diets supplemented with MgO to attain .2, .6, 1.2 or 2.4% Mg. Total fecal and urinary collections were made for the initial 20 d and last 10 d of a 50 d study. Diarrhea was noted in lambs fed the two highest Mg levels. Apparent digestibility of DM, ADF and CP decreased linearly (P less than .01) with increasing Mg levels. Dietary Mg levels did not affect (P greater than .05) rectal temperature, respiration rate or pulse rate. Apparent absorption and retention of Mg (g/d) were lowest in lambs fed 2.4% Mg until 15 d on trial, after which values increased linearly (P less than .01) with dietary Mg. Phosphorus absorption and retention decreased linearly (P less than .01) with increasing Mg levels. Increasing dietary Mg resulted in a linear increase (P less than .01) in serum Mg and variable increases (P less than .05) in erythrocyte Mg. Serum Ca was decreased linearly (P less than .05) and quadratically (P less than .05) by added Mg during the d 1 to 30 and 40 to 50 periods, respectively. Serum inorganic P was elevated consistently in lambs fed 2.4% Mg. A linear response to increasing dietary Mg (P less than .05) occurred in the Mg content of liver, kidney, rib bone and femur bone. Dietary Mg did not alter (P greater than .05) other criteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of propionate level in a volatile fatty acid salt mixture fed to lambs on weight gain, body composition and plasma metabolites

Chopped hay supplemented with a volatile fatty acid salt mixture at 20% of metabolizable energy (ME) was fed to 30 Suffolk X Corriedale lambs (mean wt 29.6 kg) to determine the effects of dietary propionate on weight gain, body composition and plasma metabolites. Propionate accounted for 0, 25, 50, 75 or 100% of the salt mixture energy, and acetate accounted for the remainder. Each diet was fed at two levels of daily intake (158.7 and 130.6 kcal ME/W.75). Lambs on the high level of intake lost more (P less than .05) energy in feces, lost less (P less than .05) energy in CH4 and had carcasses with more (P less than .10) water and fat than lambs on the low intake level. Percentage of propionate in the salt mixture had no effect on ME or body composition of lambs. Increasing the percentage of propionate in the salt mixture increased plasma propionate in blood samples taken at 1 and 2 h after feeding (linear, P less than .05). Empty body weight gain per megacalorie of ME above maintenance increased as the percentage of propionate in the salt mixture increased, but not until propionate reached 75% of the salt mixture (linear, P less than .05; cubic, P less than .05). These results show that propionate in the blood has a positive, but nonlinear, effect on weight gain, even when energy intake is held constant.     

Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism of nitrogen and energy as affected by dietary fiber concentration

Two trials were conducted to evaluate effects of, and interactions between, level and source of fiber in the diet on ruminal environment, microbial protein synthesis, nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-fistulated sheep (trial 1; 4 X 4 Latin square design) and on ruminal, digestive and metabolic characteristics of early-weaned lambs (trial 2; randomized complete block design; 3 periods). All diets tested were pelleted and were formulated to contain either 39% or 25% neutral detergent fiber (NDF), with corncobs or cottonseed hulls (CSH) as the major NDF (roughage) sources. In trial 1, dry-matter (DM) and organic-matter (OM) digestibilities were not different (P greater than .05) among treatments. Digestibility of NDF was higher (P less than .05) with high-fiber. Bacterial N synthesis (g N/kg OM truly digested) was not different (P greater than .05) among treatments. Molar proportion acetate was higher (P less than .05) and molar proportion propionate lower (P less than .05) when sheep were fed high-fiber diets. In trial 2, apparent DM digestibility was higher (P less than .05) for lambs fed diets containing corncobs. Energy digestibility was higher (P less than .05) at the low-fiber level and for lambs fed diets containing corncobs. Apparent NDF digestibility by lambs was higher (P less than .05) at the high-fiber level and for lambs fed diets containing corncobs. Nitrogen retained (percentage of N intake) was higher (P less than .05) for lambs fed diets containing CSH. Ruminal pH and molar proportion acetate were higher (P less than .05) and molar proportion propionate lower (P less than .05) for lambs fed high-fiber diets. Although responses to corncob vs CSH inclusion in high-energy pelleted diets differ, both roughages are effective as fiber sources in sheep diets.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 3. Bermudagrass and clover hays

Five crossbred beef cows (Hereford X Angus, 438 kg), cannulated in the rumen and duodenum, were used in a Latin square experiment to determine the effects of dietary proportions of bermudagrass (B) and clover (C) hays (0: 1, .25: .75, .5: .5, .75: .25 and 1: 0) on digestive function. Feed intake was 85% of ad libitum intake of B alone (1.35% of body weight). Bermudagrass contained 1.88% nitrogen (N), 79.6% neutral detergent fibre (NDF) and 5.2% acid detergent lignin (ADL), and C contained 2.30% N, 55.3% NDF and 6.3% ADL. Molar proportion of acetic increased linearly while propionic acid moved in the opposite direction as B replaced C (P less than .05). Mean particle size of duodenal digesta increased linearly (P less than .05) as B increased, but specific gravity of particles was constant (P greater than .10). Fluid passage rate decreased while volume increased linearly with increasing B (P less than .05) so that ruminal fluid outflow rate increased quadratically (P less than .10). Particulate passage rate ranged from 3.0 to 3.4% h. Apparent ruminal organic matter (OM) digestion was 69.0, 54.0, 53.0, 49.1 and 49.7% for 0, 25, 50, 75 and 100% B, respectively, decreasing quadratically as B rose (P less than .05). Postruminal OM digestibilities as percentages of intake and available OM changed quadratically (P less than .05) as dietary B increased, causing total tract OM digestion to decrease linearly (P less than .05; 73.8, 66.4, 63.1, 60.3 and 58.2% for 0, 25, 50, 75 and 100% B diets, respectively). Duodenal microbial-N flow increased quadratically with increasing B (P less than .05), being 45, 108, 103, 105 and 101 g/d, and microbial growth efficiency increased quadratically as well (P less than .05). True ruminal N disappearance ranged from 69.0 to 79.4% and was not affected by diet (P greater than .10). Ruminal digestibilities of fibre fractions were similar to OM. Little digestive function benefit was achieved by mixing warm season grass and legume hays in diets of maintenance-fed beef cows.     

Influence of alfalfa maturity on feed intake and site of nutrient digestion in sheep

Four wethers fitted with ruminal, duodenal and ileal cannulas were used to study effects of maturity of alfalfa hay on intake, digestion and rate of passage of nutrients in various sites of the digestive tract. Pre-, early-, and mid-bloom hays were harvested from the same field; full-bloom hay was acquired from elsewhere due to wether conditions. Dry matter intake decreased (P less than .05) as intakes of NDF and ADF increased. This was attributed to decreased digestibility and increased retention time of undigested residues. Digestion of OM in the stomach (% of intake) was 44.2, 47.4, 38.8 and 35.1 for pre-, early-, mid- and full-bloom hay, respectively. Digestion of ADF in the stomach was lower for mid-bloom than for pre-and early-bloom hay (P less than .05). Degradation of alfalfa protein in the rumen was 94, 88, 81 and 78% for pre-, early-, mid- and full-bloom hay, respectively. Concentration of ruminal NH3 N, flow of N at the duodenum, fecal N and urinary N decreased of the hay and to N intake. Digestion of N in the small intestine (g/d) decreased as maturity advanced (P less than .05). Duodenal flow of total amino acids was greater (P less than .05) when animals consumed pre-bloom hay than when they consumed more mature hays. Relative feed value calculated from the detergent fiber analysis correlated with actual value determined biologically (r = +.81). Intake and site of nutrient digestion of alfalfa hay were influenced by the stage of maturity at harvest.     

Comparison of the effects of three methods of harvesting and storing alfalfa on nutrient digestibility by lambs and feedlot performance of steers

Two lamb digestion and three steer growth experiments were conducted to study the feeding value of alfalfa harvested as direct-cut silage (DCS) with grain added prior to ensiling or as low-moisture silage (LMS) or hay with grain added at feeding. In all experiments, alfalfa-grain mixtures contained approximately 50% alfalfa and 50% concentrate (dry matter [DM] basis). In Exp. 1, lambs fed DCS alone consumed less DM than lambs fed LMS or hay alone or any of the alfalfa-grain mixtures. Apparent digestibilities of DM and fiber components were higher (P less than .05) for DCS than for LMS or hay. Lambs that were fed LMS digested more (P less than .05) DM and fiber components than lambs fed hay. Addition of grain resulted in increased (P less than .05) DM digestibility and decreased (P less than .05) digestibilities of neutral detergent fiber and acid detergent fiber. In Exp. 2, growing steers (271 kg) fed DCS-grain had increased (P less than .05) weight gains compared with steers fed hay-grain. Steers fed any of the alfalfa-grain mixtures gained weight more rapidly (P less than .05) than steers fed corn silage (CS)-based diets. In a third experiment, finishing steers (283 kg) fed DCS-grain, LMS-grain, hay-grain or CS-based diets performed similarly (P greater than .05), although steers fed DCS-grain had higher (P less than .05) dressing percentages and yield grades than steers that were fed the other three diets and were fatter (P less than .05) than those fed LMS-grain or CS. In Exp. 4, lambs fed DCS-grain or LMS-grain had higher (P less than .05) apparent DM and organic matter digestibilities than lambs fed CS-based diets with similar forage:grain proportions. In Exp. 5, finishing steers (326 kg) fed DCS-grain gained similarly (P greater than .05) to steers fed LMS-grain or an 85% concentrate diet based on high-moisture corn. Steers fed CS diets had lower (P less than .05) gains and increased (P less than .05) feed per gain compared with steers fed DCS-grain, LMS-grain or high-moisture corn.     

Growth performance, serum hormones, and metabolite responses before and after weaning in lambs weaned at 42 days of age: effect of preweaning milk and postweaning alfalfa or grass hay diets.

Fourteen fall-born lambs were used to determine the effects of diet before and after weaning on intake, growth, serum hormones, and metabolite profiles. Before weaning, lambs were intensively sampled for 6 h at 35 and 42 d of age. Before sample collection, lambs were allowed to suckle, and milk intake was recorded. At 42 d of age, lambs were weaned and randomly allotted to ad libitum access to either alfalfa or grass hay. Blood samples were collected at 49 and 56 d of age for 6 h. Milk intake did not differ (P greater than .10) between groups. After weaning, lambs fed alfalfa hay consumed more (P less than .05) hay and had greater (P less than .05) ADG than lambs fed grass hay. Postweaning diet had no effect (P greater than .10) on serum insulin, growth hormone (GH), insulin:GH ratio, prolactin, cortisol, glucose, or nonesterified fatty acids (NE-FA) concentrations. Lambs consuming alfalfa had higher (P less than .05) serum urea nitrogen (SUN) at 49 and 56 d of age than lambs consuming grass. At 35 and 42 d of age, (P less than .05) serum insulin and insulin:GH ratio were higher (P less than .05) after milk intake than at 49 and 56 d of age after hay intake. Serum GH was higher (P less than .05) in lambs at 35 and 42 d of age for 2 h postfeeding, but by h 3 through 5, lambs consuming milk had lower (P less than .05) values than lambs consuming hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

The nutritive value for sheep of quackgrass and timothy hays harvested at two stages of growth

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

Evaluation of alfalfa-corn cob associative action. II. Comparative tests of alfalfa hay as a source of ruminal degradable protein

The effect of ruminal degradable protein source in roughage diets on nutrient digestibility and animal growth was evaluated in two trials using lambs. In trial 1, two qualities of alfalfa and smooth brome hays replaced 0, 15, 30 or 100% of an ammonia (NH3)-treated corn cob negative control diet in a digestion trial using 26 mixed breed wethers (31.8 kg). Fifteen or 30% inclusion of hay increased (P less than .01) dry matter (DM) intake, regardless of hay type or quality. Cell wall intake was highest for 100% high quality brome hay. Positive associative action on digestibility of DM and cell walls occurred with 30% of each hay tested when diets were fed ad libitum. Measured at equal intakes, DM and cell wall digestibilities were affected by forage type X level and forage quality X level interactions (P less than .01), which showed that the magnitude of associative action was greater for 30% of high vs low quality and alfalfa vs brome hay, respectively. Magnitude of associative response on cell wall digestibility was more highly correlated to degradable N (r = .88) than cell solubles (r = .64) content of hay. In trial 2, 72 young growing lambs were allotted to three sources of supplemental ruminal degradable N (NH3, casein, corn steep liquor) superimposed upon two levels of alfalfa hay (0 or 30% of diet DM). Diets containing 0% alfalfa were supplemented with ruminal escape protein equivalent to that supplied by 30% alfalfa hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of protein and energy supplementation of wheat straw-based diets on site of nutrient digestion and nitrogen metabolism of lambs.

A 4 x 4 Latin square metabolism trial with 2 x 2 factorial arrangement of treatments was conducted with lambs to determine effects of energy and CP supplementation of wheat straw-based (WS) diets on apparent N digestion, retention, and flow to the abomasum. Four wether lambs (average weight, 32 kg) fitted with ruminal and abomasal cannulas were fed 70 vs 42% WS (remainder of the diet was concentrate) and 9.5 vs 12.5% CP. Ruminal and total tract DM and OM digestion was 41 and 33% greater (P less than .03) for high-energy than for low-energy diets. Apparent N digestibility was greater (P less than .05) for 12.5% CP than for 9.5% CP diets (69.2 vs 62.0%, respectively) and also greater (P less than .03) for high-energy than for low-energy diets (67.4 vs 63.7%, respectively). High-energy diets resulted in a 23% greater (P less than .03) N retention (percentage of N intake) than did low-energy diets; 12.5% CP diets resulted in a 9% greater N retention (P less than .10) than did 9.5% CP diets. Nitrogen retention (percentage of N digested) was 15% higher (P less than .03) for high-energy than for low-energy diets. Protein level had no effect (P greater than .10). Nitrogen retention (grams/day) was 5.65, 6.97, 5.28, and 7.43 for low-energy, high-energy, low-protein, and high-protein diets, respectively; there were responses to energy level (P less than .03) and protein level (P less than .05). Total N flow (grams/day) to the abomasum did not differ (P greater than .10) due to treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of supplemental ruminally degradable protein versus increasing amounts of supplemental ruminally undegradable protein on nitrogen retention, apparent digestibility, and nutrient flux across visceral tissues in lambs fed low-quality forage

Two experiments were conducted to determine effects of supplemental ruminally degradable protein (RDP) vs. increasing amounts of supplemental ruminally undegradable protein (RUP) on intake, apparent digestibility, N retention, and nutrient flux across visceral tissues in lambs fed low-quality forage. Lambs were fed a basal diet of crested wheatgrass hay (4.2% CP) for ad libitum consumption, plus 1 of 4 protein supplements: isolated soy protein (RDP source) fed to meet estimated RDP requirements (CON), or corn gluten meal (RUP source) fed at 50, 100, or 150% of the supplemental N provided by CON (C50, C100, and C150, respectively). In Exp. 1, 12 lambs (29.9 +/- 2.7 kg) were used. Forage OM intake was not affected (P = 0.46) by protein degradability or by increasing RUP (P >/= 0.31). Apparent total tract OM digestibility was not affected (P = 0.10) by protein degradability, but increased (P /= 0.40) by protein degradability or level of RUP. In Exp. 2, 16 catheterized lambs (32 +/- 5 kg) were used. Net release of ammonia-N from the portal-drained viscera (PDV) was greater (P = 0.02) for CON than for C100 and increased linearly (P = 0.002) as RUP increased. Net uptake of ammonia-N by liver was not affected (P = 0.23) by protein degradability, but increased linearly (P = 0.04) as RUP increased. Net urea-N release from liver was not affected (P >/= 0.49) by protein degradability or level of RUP. Net uptake of urea-N by PDV was greater (P = 0.02) for C100 compared with CON and increased (P = 0.04) with increasing RUP. Neither net release from PDV nor hepatic uptake of alpha-amino N were affected (P >/= 0.12) by protein degradability or level of RUP. Hepatic ammonia-N uptake accounted for 82, 38, 98, and 79% of net urea-N release from the liver for CON, C50, C100, and C150, respectively. Hepatic alpha-amino N uptake for all treatments greatly exceeded that required for the remaining urea-N release by the liver, suggesting that alpha-amino N may serve as a temporary means of storing excess N by liver between supplementation events. The pattern of net release or uptake of N metabolites between supplementation events requires further investigation.     

Effects of varying zinc concentrations on quality of alfalfa for lambs

Zinc concentrations in alfalfa hay were varied using a N-Zn liquid fertilizer as a foliar applicant (.34 or .68 kg Zn/ha) or as a soil fertilizer (4.07 kg Zn/ha). Mean concentrations of Zn across five cuttings of alfalfa in 2 yr were 18, 27, 41 and 21 mg Zn/kg DM for control, low foliar, high foliar and soil treatments, respectively. Each treatment was fed in ad libitum amounts to eight crossbred wether lambs (20 to 35 kg) in 6-wk growth and intake trials, followed by 2-wk digestibility and balance trials with individual lambs. For one cutting, hays were also fed in an 81-d trial to four ram lambs (30 to 35 kg) and live weight gain and testicular development were measured. Average daily gain (ADG) and intake over 6 wk differed (P less than .01) with cutting but not with Zn treatment. Average daily gain and testes weight of ram lambs also were not affected by treatment. In the metabolism trials, Zn treatment did not alter (P greater than .05) intake or dry matter digestibility (DMD) of alfalfa, but did influence digestibility of neutral detergent fiber (NDF). Digestible NDF (%) was higher (P less than .05) for high foliar than for low foliar treatments. Apparent absorption and retention of Zn was significantly greater for control than for Zn-treated alfalfas and did not differ with cutting. Mean serum Zn concentrations for control, low and high foliar, and soil treatments were .79, .81, .78 and .75 micrograms Zn/ml, respectively, for all cuttings, with no differences due to treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth, nutrient utilization and intestinal morphology of pigs fed high-fiber diets

Two trials (24 and 48 pigs; 9.7 kg initial body weight) were conducted to determine the effects of dietary fiber on growth, nutrient utilization and intestinal morphology of young pigs. The four diets fed were: basal corn-soybean meal (B), 15% oat hulls (OH), 15% soybean hulls (SH), and 20% alfalfa meal (AM). Fiber source did not have major effects on performance in a 35-d feeding trial. Balance trials (7-d duration) were conducted 32 d (Trial 1) or 6 d (Trial 2) after completion of the feeding trials. Feed intakes were equalized at 8.7% (Trial 1) or 10.3% (Trial 2) of initial body weight (kg.75). All fiber sources decreased apparent digestibilities of N, energy and dry matter (P less than .05) with no effect on N retention. Apparent digestibilities of neutral and acid detergent fiber, cellulose, and hemicellulose were reduced by OH and AM (P less than .01), but not by SH. Fiber sources did not affect apparent Ca, P, Zn or Mn absorption or retention, or Mg absorption, but decrease Mg retention (P less than .05). Apparent Na absorption was decreased by OH and increased by AM (P less than .05) but was unaffected by SH. All fiber sources increased K intake, but only SH and AM increased apparent K absorption (P less than .05). Fiber sources did not affect Na or K retention. The OH increased Cu intake and balance (P less than .05). All fiber sources increased Fe intake, but only SH and AM increased (P less than .05) Fe balance. Villus shape and surface morphology in jejunum and ileum examined by scanning electron microscopy (Trial 1 only) appeared to be independent of diet. However, jejunum villus morphologies of two pigs fed AM were characterized by loss of epithelial cells and microvilli at the villus apex, and ileum villi were blunted and frequently folded in one pig fed SH. Fiber sources at the levels included in a corn-soybean meal diet fed in this study had only a minimal impact on performance and utilization of minerals and N and intestinal structure, although apparent energy utilization was decreased.     

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

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