Effect of cattle age, forage level, and corn processing on diet digestibility and feedlot performance

Three experiments were conducted to determine the effects of cattle age and dietary forage level on the utilization of corn fed whole or ground to feedlot cattle. In Exp. 1, 16 steers were used to investigate the effects of cattle age and corn processing on diet digestibility. Two cattle age categories were evaluated (weanling [254 +/- 20 kg BW] and yearling [477 +/- 29 kg BW]; eight steers per group), and corn was fed either ground or whole to each cattle age category. Cattle age and corn processing did not affect (P > 0.10) diet digestibility of DM, OM, starch, CP, NDF or ADF, and no interactions (P > 0.10) between these two factors were detected. In Exp. 2, the effects of forage level and corn processing on feedlot performance and carcass characteristics were evaluated. One hundred eighty steers (310 +/- 40 kg BW) were allotted to 24 pens, and were fed one of the following diets: high-forage (18.2% corn silage) cracked corn (HFCC); high-forage shifting corn (whole corn for the first half of the trial, then cracked corn until harvest; HFSC); high-forage whole corn (HFWC); low-forage (5.2% corn silage) cracked corn (LFCC); low-forage shifting corn (LFSC); and low-forage whole corn (LFWC). For the high-forage diets, steers fed cracked corn had 7% greater DMI than those fed whole corn, whereas for the low-forage diets, grain processing did not affect DMI (interaction; P = 0.02). No interactions (P > 0.10) between forage level and corn processing were found for ADG and G:F. Total trial ADG and G:F, and percentage of carcasses grading USDA Choice, and carcass yield grade were not affected (P > 0.10) by corn processing. Cattle with fewer days on feed grew faster and more efficiently when cracked corn was fed, whereas cattle with longer days on feed had greater ADG and G:F when corn was fed whole (interaction; P < 0.10). In Exp. 3, the effects of forage level and corn processing on diet digestibility were evaluated. The high-forage cracked corn, high-forage whole corn, low-forage cracked corn, and low-forage whole corn diets used in Exp. 2 were fed to 16 steers (350 +/- 27 kg BW) in a digestion trial. No interactions (P > 0.10) between forage level and corn processing were detected for starch digestibility. Forage level and corn processing (grinding) did not affect (P > 0.10) diet DM, OM, starch, CP, and NDF digestibility. Processing corn did not provide additional benefits to feedlot cattle performance under these experimental conditions.     

Effects of dry corn gluten feed on feedlot cattle performance and fiber digestibility

Effects of dry corn gluten feed (DCGF) on feedlot cattle performance and fiber digestibility were investigated. In Trial 1, 120 growing steers were fed corn silage-based diets containing 0, 40, 60 or 80% DCGF. Increasing levels of DCGF resulted in a curvilinear response in gain (P less than .05) and a linear increase in feed/gain (P less than .01). When the same steers subsequently were fed the same levels of DCGF in corn-based diets (Trial 2), increasing the percentage of dietary DCGF resulted in a linear decrease in gain (P less than .01) and a linear increase in feed/gain (P less than .01). In Trial 3, 46 crossbred steers were fed individually in a 2 x 2 factorial design to determine effects of 60 or 80% dietary high-moisture corn (HMC) or DCGF on feedlot cattle performance. Steers fed HMC had faster (P less than .08) and more efficient (P less than .05) gains than those fed DCGF, which had greater feed intakes (P less than .05). In Trial 4, 120 Angus crossbred steers were used to compare effects of 20 or 40% dietary HMC or DCGF on feedlot performance. Steers fed diets containing 40% HMC or DCGF had greater gains (P less than .01) and feed intakes (P less than .01) than those fed 20% diets. Steers fed HMC gained more efficiently than those fed DCGF (P less than .01). In an in situ trial, 0, 40, 60 or 80% dietary DCGF did not affect in situ DCGF DM or NDF disappearance. When DCGF was fermented in vitro in combination with corn silage, increasing the level of DCGF from 0 to 100% resulted in a linear increase (P less than .01) in 24 and 48 h NDF disappearance. These results suggest that at high dietary levels DCGF will support feedlot cattle gains that are nearly equal to those of cattle fed corn silage but somewhat less than those fed corn.     

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism.

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.     

Effects of oscillating dietary protein on nutrient digestibility,nitrogen metabolism,and gastrointestinal organ mass in sheep

Twenty-four wether lambs (BW = 37.5 +/- 0.8 kg) were used in a 64-d randomized complete block design experiment to evaluate the effect of oscillating dietary CP with undegradable intake protein (UIP) on diet digestibility, N retention, and gastrointestinal (GI) organ mass. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) and 35% corn-based supplement, and were formulated to contain the same amount of degradable intake protein (9.6% of dry matter), plus additional UIP (from SoyPLUS) to accomplish CP levels above 13%. Beginning on d 52, N balance collections were conducted for 8 d, after which lambs were killed on d 62 and 64 of the trial for measurement of GI organ mass. Because intake was restricted to 3.0% of initial body weight (dry matter basis), dry matter intake did not differ (P > or = 0.67) and no treatment effects (P > or = 0.36) on ADG, feed efficiency, or total tract DM digestibility were observed. Increasing dietary CP from 13 to 17% linearly increased (P = 0.0001) N digestibility, but lambs fed ACP had lower (P = 0.07) total tract N digestibility than those fed 15% CP daily. Although urinary N excretion increased linearly (P = 0.0001) with increasing CP, a linear increase (P = 0.07) was observed in N retention (g/d) with increasing dietary CP. Although the quantity of N retained by lambs fed ACP was not statistically different (g/d, P = 0.19; % of digested N, P = 0.23) from those fed 15% CP daily, N retention in lambs fed ACP was 42% lower than in those fed 15% CP daily (1.8 vs 3.1 g/d, respectively). Increasing CP linearly decreased (P < or = 0.09) weights of the reticulorumen, abomasum, and small intestine, but did not affect (P > or = 0.16) liver or omasum weights. Length of the small intestine was not affected (P > or = 0.45) by treatment, but lambs fed ACP had greater (P = 0.03) small intestine weights than those fed 15% CP daily. Increasing dietary CP linearly decreased (P = 0.03) total GI organ mass, and lambs fed ACP had a greater (P = 0.03) total GI organ mass than those fed 15% CP daily. Oscillating dietary CP may increase the weights of the GI organs, which may subsequently have negative effects on N and energy metabolism in the animal. Likewise, the potential for decreased GI organ mass in response to increased supply of CP with UIP deserves further investigation.     

Effects of dietary energy level and supplemental protein source on performance of growing steers and nutrient digestibility and nitrogen balance in lambs

Four experiments were conducted to evaluate three crude protein (CP) sources (urea, U; soybean meal, SBM; corn gluten meal, CGM) in diets based on corn silage (high energy) or grass hay (low energy). In Exp. 1 and 2, growing steers were fed all combinations of energy and protein source at 10.5 or 12% CP. Steers fed high energy diets or 12% CP had improved (P less than .05) daily gains and feed:gain over 84 d. Protein source had no effect (P greater than .05) on performance except that steers fed U consumed more (P less than .05) feed than those fed CGM. Steers were fed experimental diets to a common weight and switched to an 85% concentrate diet for finishing. During finishing, steers fed low energy diets in the growing period consumed more (P less than .05) feed and had increased (P less than .05) feed:gain compared with those fed high energy diets. Growing lambs were fed the same diets as steers. At 10.5% CP, lambs fed high energy diets had higher (P less than .05) digestibilities of dry matter (DM), organic matter (OM), nitrogen (N) and fiber components, and retained more (P less than .05) N. For lambs on 12% CP, high energy diets had higher (P less than .05) DM and OM digestibilities and lower (P less than .05) N digestibilities. At 12% CP, energy level had no effect (P greater than .05) on N retained. Protein source had no effect (P greater than .05) on N retention. There appeared to be no advantage in supplementing with ruminally undegradable proteins, i.e. CGM, in these experiments.     

Effects of dietary dried whey and corn oil on weanling pig performance, fat digestibility and nitrogen utilization

Two experiments were conducted to evaluate the effects and interactions of dietary levels of corn oil (0 vs 6%) and dried whey (0 vs 25%) on performance of young pigs during a 4-wk postweaning period. The first experiment, conducted in five replicates as a 2 x 2 factorial in a randomized block design, evaluated gain and feed intakes of 172 pigs weaned at 21 d of age. Pigs were bled at weekly intervals, and samples were assayed for serum triglyceride and urea concentrations. In a second experiment, 36 barrows in three replicates were used to evaluate the same treatments on apparent digestibility and absorption of fat and N retention during each week of a 4-wk postweaning period. The dietary inclusion of dried whey resulted in greater gains and feed intakes and reduced feed-to-gain ratios during each week of the postweaning period, with the largest relative improvement occurring during wk 1. Supplemental corn oil did not enhance pig gains the first 3 wk postweaning, but response improved by wk 4. Feed intakes were slightly (P less than .10) lower when corn oil was provided. The inclusion of corn oil resulted in an improved feed-to-gain ratio (P less than .01), particularly evident during wk 3 and 4 postweaning. Neither gain nor feed utilization were improved by added corn oil during the initial 2-wk postweaning period regardless of dried whey addition. Apparent digestibilities of fat were unaffected at each weekly interval by dietary dried whey inclusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of level and source of dietary selenium on maternal and fetal body weight, visceral organ mass, cellularity estimates, and jejunal vascularity in pregnant ewe lambs

Pregnant Targhee ewe lambs (n = 32; BW = 45.6 +/- 2.2 kg) were allotted randomly to 1 of 4 treatments in a completely randomized design to examine the effects of level and source of dietary Se on maternal and fetal visceral organ mass, cellularity estimates, and maternal jejunal crypt cell proliferation and vascularity. Diets contained (DM basis) either no added Se (control) or supranutritional Se from high-Se wheat at 3.0 ppm Se (SW) or from sodium selenate at 3 (S3) or 15 (S15) ppm Se. Diets were similar in CP (15.5%) and ME (2.68 Mcal/kg of DM) and were fed to meet or exceed requirements. Treatments were initiated at 50 +/- 5 d of gestation. The control, SW, S3, and S15 treatment diets provided 2.5, 75, 75, and 375 microg of Se/kg of BW, respectively. On d 134 +/- 10 of gestation, ewes were necropsied, and tissues were harvested. Contrasts, including control vs. Se treatments (SW, S3, and S15), SW vs. S3, and S3 vs. S15, were used to evaluate differences among Se levels and sources. There were no differences in ewe initial and final BW. Full viscera and liver mass (g/kg of empty BW and g/kg of maternal BW) and maternal liver protein concentration (mg/g) and content (g) were greater (P < 0.04) in Se-treated compared with control ewes. Maternal liver protein concentration was greater (P = 0.01) in SW vs. S3 ewes, and content was greater (P = 0.01) in S15 compared with S3 ewes. Maternal jejunal mucosal DNA concentration (mg/g) was greater (P = 0.08) in SW compared with S3 ewes. Total number of proliferating cells in maternal jejunal mucosa was greater (P = 0.02) in Se-fed compared with control ewes. Capillary number density within maternal jejunal tissue was greater (P = 0.08) in S3 compared with SW ewes. Selenium treatment resulted in reduced fetal heart girth (P = 0.08). Fetal kidney RNA (P = 0.04) and protein concentrations (mg/g; P = 0.03) were greater in Se-treated compared with control ewes. These results indicate that supranutritional dietary Se increases cell numbers in maternal jejunal mucosa through increased crypt cell proliferation. No indications of toxicity were observed in any of the Se treatments.     

纤维源对不同品种生长猪养分消化率和氮平衡的影响

试验旨在研究纤维源对不同品种生长猪养分消化率和氮平衡的影响试验选取体重相近、健康去势的烟台黑、鲁农2号生长猪各6头,饲喂玉米-豆粕型日粮,采用有重复的3×3拉丁方设计,三个处理分别为基础日粮组、10%大豆皮替代基础日粮组、10%地瓜蔓替代基础日粮组。于每期试验的第6、7 d连续收集48 h的粪样和尿样测定日粮养分消化率和氮平衡代谢。结果表明:日粮添加10%地瓜蔓,两品种生长猪养分消化率和氮平衡显著或极显著降低(P0.05或P0.01),添加10%大豆皮对其氮总利用率影响显著(P0.05),对其他则影响不显著(P0.05);除对干物质消化率(P0.01)、氮表观消化率(P0.05)外,猪的品种对养分消化率和氮平衡均有显著影响(P0.05);纤维源对养分消化率和氮平衡均影响极显著(P0.01);但二者的互作关系不明显(P0.05)。与烟台黑生长猪相比,纤维源对鲁农2号生长猪养分消化率及氮平衡代谢的影响更大。     

Effects of barley grain processing and dietary ruminally degradable protein on urea nitrogen recycling and nitrogen metabolism in growing lambs

The objective of this study was to determine how interactions between dietary ruminally degradable protein (RDP) level and ruminally fermentable carbohydrate (RFC) alter urea N transfer to the gastrointestinal tract (GIT) and the utilization of this recycled urea N in rapidly growing lambs fed high-N diets. Four Suffolk ram lambs (34.8 +/- 0.5 kg of BW) were used in a 4 x 4 Latin square design with 21-d periods and a 2 x 2 factorial arrangement of dietary treatments. The dietary factors studied were 1) dry-rolled vs. pelleted barley as the principal source of RFC and 2) dietary levels of RDP of 60 vs. 70% (% of CP). All diets contained 28.8 g of N/kg of DM. Experimental diets were composed of 80% concentrate mixture and 20% barley silage (DM basis) and were fed twice daily at 0900 and 1700 as total mixed rations. Nitrogen balance was measured from d 15 to 20, and urea N kinetics were measured from d 15 to 19 using intrajugular infusions of [(15)N(15)N]-urea. Nitrogen intake (P = 0.001) and fecal (P = 0.002) and urinary (P = 0.03) N excretion increased as dietary RDP level increased, but the method of barley processing had no effect. Feeding dry-rolled compared with pelleted barley (P = 0.04) as well as feeding 60% RDP compared with 70% RDP (P = 0.04) resulted in a greater N digestibility. Whole-body N retention was unaffected (P >/= 0.74) by dietary treatment. Dietary treatment had no effect on endogenous production of urea N and its recycling to the GIT; however, across dietary treatments, endogenous production of urea N (45.8 to 50.9 g/d) exceeded N intake (42.3 to 47.9 g/d). Across dietary treatments, 30.6 to 38.5 g/d of urea N were recycled to the GIT, representing 0.67 to 0.74 of endogenous urea N production; however, 0.64 to 0.76 of urea N recycled to the GIT was returned to the ornithine cycle. In summary, although dietary treatment did not alter urea N kinetics, substantial amounts of hepatic urea N output were recycled to the GIT under the dietary conditions used in this study, and additional research is required to determine how this recycled urea N can be efficiently captured by bacteria within the GIT.     

Effects of increasing dried distillers grains with solubles on performance, carcass characteristics, and digestibility of feedlot lambs

The objectives of this study were to determine the effects of 0, 20, 40, or 60% dietary dried distillers grains with solubles (DDGS) on 1) growing lamb performance, carcass characteristics, and tissue minerals, and 2) nutrient digestibility and retention in growing lambs. In Exp. 1, ninety-six lambs were blocked by sex (ewes, n = 48; wethers, n = 48) and BW, housed in 24 pens (4 lambs per pen), and used in a 92-d feedlot trial (initial BW = 26.4 ± 9.3 kg). Lambs were fed 1 of 4 dietary treatments 1) 0% DDGS, 2) 20% DDGS, 3) 40% DDGS, or 4) 60% DDGS. The DDGS replaced primarily corn, and diets were fed as a complete pellet. There was a quadratic effect of DDGS inclusion on ADG; lambs fed the 20% DDGS diet had the greatest (P = 0.04) gains at 0.358 kg/d. This effect on ADG led to a quadratic (P = 0.03) effect of DDGS on final BW. Increasing dietary DDGS did not affect (P > 0.13) DMI and resulted in a linear (P = 0.02) decrease in G:F. In the liver, S increased linearly (P = 0.05), whereas Cu decreased linearly (P < 0.01) with increasing dietary DDGS; other liver minerals were not affected (P > 0.05). Carcass backfat, yield grade, and marbling score were not affected (P > 0.05) by dietary DDGS. In Exp. 2, twenty-four lambs (initial BW = 43.0 ± 4.4 kg) were used in a metabolism study. Lambs were adapted to the same diets described above for 17 d before a 5-d sampling period during which total feces and urine were collected. Apparent digestibility of dietary DM decreased linearly (P < 0.01) with increasing dietary inclusion of DDGS. Digestibility of fat followed a similar pattern, whereas N, S, and P absorption increased linearly (P < 0.03) with increasing dietary DDGS. The digestibility of NDF was not affected (P > 0.05) by dietary treatment. Apparent retentions (as a percentage of intake) of N, K, Mg, Cu, Fe, and Zn were not affected (P > 0.05) by dietary DDGS inclusion, whereas the retention of S and P decreased (P < 0.04). Daily urine output increased linearly (P < 0.01) and urine pH decreased linearly (P < 0.01) with increasing DDGS (urine pH was 7.46, 5.86, 5.52, and 5.32 for treatments 1 to 4, respectively). These data suggest urine is a major route for excretion of acid when high-S diets containing DDGS are fed. Increases in dietary DDGS resulted in decreased digestion of DM and fat, which may be partially responsible for decreased lamb feedlot performance for 40 and 60% dietary DDGS when compared with 20% DDGS.     

不同能量水平低氮饲粮对藏羊表观消化率、氮代谢和生长性能的影响

试验旨在研究不同能量水平低氮饲粮对藏羊表观消化率、氮代谢和生长性能的影响,为高寒地区反刍家畜冷季补饲提供参考。选取1.5周岁、体重(48.5±1.89) kg和体况相近的健康去势藏羊24只,随机分为低能(LE)、中低能(MLE)、中高能(MHE)和高能(HE)4个处理组,每组6个重复。试验饲粮的粗蛋白质(CP)含量相近[(6.97±0.05)%]而能量不同,其消化能(DE)水平分别为8.21、9.33、10.45和11.57 MJ·kg^-1。经过49 d的饲养和全收粪尿法,结果表明:1)藏羊的干物质(DM)、粗蛋白质(CP)、总能(GE)采食量在各处理组间基本相同(P>0.05),其中DM、GE表观消化率都随着能量水平的提高而线性增加(P<0.05);2)当饲粮能量水平升高时,藏羊血清尿素氮(BUN)浓度线性增加(P<0.05),而游离脂肪酸(FFA)浓度却线性降低(P<0.05);3)随着饲粮能量水平升高,藏羊尿氮排出量线性降低(P<0.05),氮平衡和氮沉积率均线性升高(P<0.05),并且氮沉积率(NDR,%)与饲粮能量水平(DE, MJ·kg^-1)呈显著线性正相关,其关系式为NDR=5.2143DE-39.006(R²=0.9616,n=24);4)藏羊的平均日增重(ADG)随着饲粮能量水平的提高而线性增加(P<0.05),除LE组外,其余ADG都为正值。上述研究结果表明,藏羊的蛋白和能量维持需要量较低,低氮条件下提高能量水平可改善藏羊的饲料营养消化率、氮代谢以及生长性能。     

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth,diet digestibility,intake and carcass characteristics of feedlot lambs

The effects of the β-adrenergic agonists ractopamine hydrochloride (RH; 0.35, 0.70 and 1.05 mg kg^− 1 of BW d^− 1) and zilpaterol hydrochloride (ZH; 0.10, 0.20 and 0.30 mg kg^− 1 of BW d^− 1) on growth performance and carcass characteristics were determined in 84 Dorper × Katahdin lambs (12 lambs per treatment), that were randomly assigned to a complete block design during a 42-day feeding trial. Lambs were fed a corn grain-based diet (18.71% CP and 12.9 MJ/kg ME). Nutrient digestibility of diets and blood serum metabolites were also determined. There were no significant (P > 0.05) differences in growth characteristics by effect of ZH or RH administration. However, lambs final weight, total weight gain and ADG increased linearly (P < 0.05) as levels of both β-adrenergic agonist increased. RH or ZH administration did not affect feed efficiency, diet digestibility or particular blood serum metabolites of lambs. Carcass characteristics of lambs consuming ZH were significantly better (P < 0.01) than RH or control lambs; RH produced significant linear response on carcass weight, dressing percentage, longissimus muscle area, carcass conformation and quality grade, and improved quadratically (P < 0.05) fat thickness and USDA yield grade of lamb carcasses. On the other hand, increasing levels of ZH decreased linearly (P > 0.01) fat thickness and improved (P > 0.05) USDA yield grade and carcass quality grade. Both β-adrenergic agonists improved carcass characteristics; although greater improvements were obtained with ZH than RH for most carcass characteristics.     

Effects of dietary sewage solids on feedlot performance, carcass characteristics, serum constituents and tissue elements of growing lambs

Twenty fine-wool wether lambs were allotted randomly at weaning to be fed a conventional diet (CD) formulated for growing lambs, or the same basal mixture plus dried gamma-irradiated solids from primary sewage sludge (SS) incorporated as 7% of the dry matter. Feedlot performance and chemical elements in whole blood were monitored during 90 d, after which lambs were slaughtered and carcass data were collected. Concentrations of Ag, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb and Zn were measured in livers, kidneys, bones, spleens and muscles. Sewage solids in the diet did not affect performance appreciably, although dressing percentages from lambs fed SS were 4% lower than CD-fed animals (P less than .05). Rib eye areas, fat thicknesses, quality and yield grades were similar (P greater than .05). Element concentrations in whole blood at weaning, after 56 d of the feeding trial and at slaughter did not differ (P greater than .05) between dietary groups. Serum chemistry determinations showed no biologically meaningful patterns related to diets. Lambs fed SS had higher (P less than .05) concentrations of Cu in livers (51.1 vs 34.3 +/- 3.8 micrograms/g, mean +/- SE) and Pb in kidneys (4.0 vs 2.2 +/- .3 micrograms/g) and lower (P less than .05) Mg in kidneys (.69 vs .72 +/- .01 mg/g). None of the elements in spleen and muscle tissue differed (P greater than .05) between diet groups. Lambs fed SS had elevated (P less than .05) bone Co, Cu, Fe, K and Na compared with those of CD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of selenium supply and dietary restriction on maternal and fetal body weight, visceral organ mass and cellularity estimates, and jejunal vascularity in pregnant ewe lambs

To examine effects of nutrient restriction and dietary Se on maternal and fetal visceral tissues, 36 pregnant Targhee-cross ewe lambs were allotted randomly to 1 of 4 treatments in a 2 x 2 factorial arrangement. Treatments were plane of nutrition [control, 100% of requirements vs. restricted, 60% of controls] and dietary Se [adequate Se, ASe (6 microg/kg of BW) vs. high Se, HSe (80 microg/kg of BW)] from Se-enriched yeast. Selenium treatments were initiated 21 d before breeding and dietary restriction began on d 64 of gestation. Diets contained 16% CP and 2.12 Mcal/kg of ME (DM basis) and differing amounts were fed to control and restricted groups. On d 135 +/- 5 (mean +/- range) of gestation, ewes were slaughtered and visceral tissues were harvested. There was a nutrition x Se interaction (P = 0.02) for maternal jejunal RNA:DNA; no other interactions were detected for maternal measurements. Maternal BW, stomach complex, small intestine, large intestine, liver, and kidney mass were less (P < or = 0.01) in restricted than control ewes. Lung mass (g/kg of empty BW) was greater (P = 0.09) in restricted than control ewes and for HSe compared with ASe ewes. Maternal jejunal protein content and protein:DNA were less (P < or = 0.002) in restricted than control ewes. Maternal jejunal DNA and RNA concentrations and total proliferating jejunal cells were not affected (P > or = 0.11) by treatment. Total jejunal and mucosal vascularity (mL) were less (P < or = 0.01) in restricted than control ewes. Fetuses from restricted ewes had less BW (P = 0.06), empty carcass weight (P = 0.06), crown-rump length (P = 0.03), liver (P = 0.01), pancreas (P = 0.07), perirenal fat (P = 0.02), small intestine (P = 0.007), and spleen weights (P = 0.03) compared with controls. Fetuses from HSe ewes had heavier (P < or = 0.09) BW, and empty carcass, heart, lung, spleen, total viscera, and large intestine weights compared with ASe ewes. Nutrient restriction resulted in less protein content (mg, P = 0.01) and protein:DNA (P = 0.06) in fetal jejunum. Fetal muscle DNA (nutrition by Se interaction, P = 0.04) concentration was greater (P < 0.05) in restricted ewes fed HSe compared with other treatments. Fetal muscle RNA concentration (P = 0.01) and heart RNA content (P = 0.04) were greater in HSe vs. ASe ewes. These data indicate that maternal dietary Se may alter fetal responses, as noted by greater fetal heart, lung, spleen, and BW.     

Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: II. Ruminal nitrogen metabolism, diet digestibility, and nitrogen balance in lambs

Three lamb metabolism experiments were conducted to investigate the effects of chronic administration of the novel urease inhibitor N (n-butyl) thiophosphoric triamide (NBPT) on ruminal N metabolism, fermentation, and N balance. In Exp. 1, ruminally cannulated wethers (n = 28; 45.0 +/- .9 kg) were administered one of seven doses of NBPT (0 [control], .125, .25, .5, 1, 2, or 4 g of NBPT daily) and fed a common cracked corn/cottonseed hull-based diet twice daily containing 2% urea at 2.5% of initial BW for the duration of the 15-d experiment. Overall, NBPT decreased (linear P < .0001; quadratic P < .001) ruminal urease activity, resulting in linear increases (P < .0001) in ruminal urea and decreases in ruminal NH3 N concentrations. However, the detection of an NBPT x day interaction (d 2 vs 15; P < .01) indicated that this depression in urea degradation diminished as the experiment progressed. Increasing NBPT linearly decreased (P < .01) total VFA concentrations on d 2 of the experiment, but it had no effect (P > .10) on d 15. Increasing NBPT had no effect (P > .10) on DM or ADF digestibilities, but it linearly decreased (P < .01) N digestibility. Supplementing NBPT produced a linear increase (P < .05) in urinary N excretion and a linear decrease (P < .01) in N retention. In Exp. 2, ruminally cannulated wethers (n = 30; 46.8 +/- .6 kg) were fed one of two basal diets (2.0 vs 1.1% dietary urea) at 2.5% of initial BW and dosed with either 0 (control), .25, or 2 g of NBPT daily for the duration of the 15-d experiment. There were no NBPT x dietary urea interactions (P > .10) for Exp. 2. Increasing NBPT depressed (linear and quadratic P < .0001) ruminal urease activity, producing linear (P < .0001) increases in urea N and linear decreases in NH3 N in the rumen. As in Exp. 1, an NBPT x day interaction (P < .05) was noted for urea, NH3 N, and total VFA concentrations; the maximum response to NBPT occurred on d 2 but diminished by d 15 of the experiment. Administration of NBPT did not influence (P > .10) DM, ADF, or N digestibilities in Exp. 2. In Exp. 3, wether lambs (n = 30; 26.4 +/- .7 kg) were subjected to the same treatment regimen as in Exp. 2 for a 14-d N balance experiment. Although several NBPT x dietary urea interactions (P < .05) were noted, increasing NBPT did not affect (P > .10) N digestibility. Administration of NBPT quadratically increased (P < .10) urinary N excretion, producing a linear decrease (P < .05) in N retention. These results suggest that although NBPT is capable of inhibiting ruminal urease short-term, the ruminal microflora may be capable of adapting to chronic NBPT administration, thereby limiting its practical use in improving the utilization of dietary urea.     

Effects of malate on diet digestibility, microbial protein synthesis, plasma metabolites, and performance of growing lambs fed a high-concentrate diet

The objective of this study was to evaluate the effects of malate supplementation on growth rate, feed efficiency, and diet digestibility in growing lambs. Twenty-four Merino lambs with a mean BW of 15.3 +/- 0.22 kg were divided into 3 homogenous groups. Each group was randomly allocated to 1 of 3 malate (16% disodium malate:84% calcium malate) levels: 0 (control), 4 (MAL-4), or 8 (MAL-8) g/kg of concentrate. Lambs were fed concentrate and barley straw ad libitum for 35 d. After a 20-d period, diet digestibility was determined, and microbial N flow at the duodenum was estimated from the urinary excretion of purine derivatives. Blood samples were taken on d 0, 20, and 35. On d 35, lambs were slaughtered and ruminal fluid samples were collected. There were no effects (P = 0.18 to P = 0.95) of malate on concentrate or straw intake, ADG, carcass yield, and apparent digestibility of OM, CP, NDF, or ADF. Malate supplementation did not influence (P = 0.80) the daily urinary excretion of total purine derivatives, and therefore there were no treatment effects (P = 0.77) on estimated microbial N flow at the duodenum. No differences (P > 0.05) among treatments were observed for plasma concentrations of glucose, cholesterol, triglycerides, urea-N, lactate, or VFA, but malate addition increased (P = 0.003) the molar proportion of butyrate in ruminal fluid (4.29, 6.14, and 5.45% of total VFA for control, MAL-4 and MAL-8, respectively). The use of malate as a feed additive under the conditions of the current study did not influence diet intake or digestion, and consequently did not improve lamb performance.     

Nutrient digestibility and feedlot performance of lambs fed diets varying protein and energy contents

Thirty-six Thalli male growing lambs were used in a completely randomized design with 2 × 2 factorial arrangement of treatments to evaluate the effect of varying levels of energy and protein on nutrient intake, digestibility, weight gain, and gain to feed ratio. Four experimental diets, i.e., low energy–low protein (LE-LP), low energy–high protein (LE-HP), high energy–low protein (HE-LP), and high energy–high protein (HE-HP) were formulated. The low- and high-energy diets contained 2.3 and 2.7 MJ/kg dry matter (DM) with 12% and 14% of crude protein. The lambs were fed ad libitum. Dietary energy and protein levels and their interactions influenced the nutrient intake. Maximum dry matter intake was noted in animals fed LE-HP diet followed by LE-LP, HE-HP, and HE-LP diets. Digestibility of DM and N increased (P < 0.01) and that of neutral detergent fiber decreased (P < 0.01) linearly with increasing levels of dietary energy and protein. Digestibility of N was only affected by protein level and interaction between energy and protein levels. Average daily gain was higher (P < 0.01) in lambs fed HE-HP diet followed by LE-HP, LE-LP, and HE-LP diets. Dietary energy and protein levels and their interaction had significant effect (P < 0.01) on gain to feed ratio.     

Effects of dietary iron on performance and mineral utilization in lambs fed a forage-based diet

Twenty-four lambs, averaging 29 kg, were used to determine the effect of supplemental dietary Fe on performance and Cu, P, Zn and Mn utilization. Treatments consisted of supplemental Fe at 0, 300, 600 or 1,200 mg/kg diet as ferrous carbonate. The basal diet contained 154 mg Fe/kg diet and consisted of 90% Coastal bermudagrass pellets, 9.45% group corn, .5% sodium chloride and .05% vitamin mix. Lambs were slaughtered after having ad libitum access to diets for 98 to 121 d. Dietary Fe did not affect lamb gain or feed intake. Supplemental Fe increased Fe concentrations in liver (P less than .01), spleen (P less than .01) and bone (P less than .10), but not in kidney and muscle. Serum Fe concentrations and percentage transferrin saturation in serum were increased (P less than .01) by supplemental Fe at 28 and 84 d, but not at the termination of the study. Plasma Cu was decreased (P less than .01) at 56 d, whereas serum ceruloplasmin activity was reduced (P less than .01) at 28 d in lambs fed 1,200 mg Fe/kg diet compared with lambs fed 600 mg Fe/kg diet. Lower levels of Fe (300 and 600) reduced (P less than .01) ceruloplasmin by 56 d and plasma Cu by 84 d compared with controls. Liver Cu also was decreased (P less than .05) by supplemental Fe. Plasma P was decreased slightly (P less than .10) by 28 d and significantly (P less than .01) at the other sampling dates by supplemental Fe.(ABSTRACT TRUNCATED AT 250 WORDS)