Splanchnic nitrogen metabolism by growing beef steers fed diets containing sorghum grain flaked at different densities

The objective of this study was to determine effects of processing method, dry-rolled (DR) vs steam-flaked (SF), and degree of processing (flake density, FD) of SF sorghum grain on splanchnic (gut and liver) N metabolism by growing steers. Diets contained 77% sorghum grain either DR or SF at densities of 437, 360, and 283 g/L (SF34, SF28, and SF22, respectively). Eight crossbred steers (340 kg initial BW), implanted with indwelling catheters into portal, hepatic, and mesenteric veins and the mesenteric artery, were used in a randomized complete block design. Blood flows and net output or uptake of ammonia N, urea N (UN), and alpha-amino N (AAN) were measured across portal-drained viscera, hepatic, and splanchnic tissues. Plasma arterial, portal, and hepatic concentrations of individual amino acids were also measured. Decreasing FD linearly increased (P = .04) net absorption of AAN (51, 73, and 78 g/d for SF34, SF28, and SF22, respectively) and transfer (cycling) of blood UN to the gut (49, 48 and 64 g/d; P = .02). Net UN cycling averaged 38% of N intake across all diets. Hepatic uptake of AAN or UN synthesis, and splanchnic output of AAN and UN, were not altered by FD. Lowering FD linearly increased (P < or = .02) portal-arterial concentration differences for blood AAN and UN and plasma arterial concentrations for alanine. Steers fed SF compared to DR tended to have greater (P = .11) blood UN cycling (percentage of hepatic synthesis; 64 vs 50%) and decreased (P = .03) net splanchnic UN output (30 vs 50 g/d), but other net fluxes of N were not altered across splanchnic tissues. Steam-flaking compared to dry-rolling tended to decrease (P = .12) portal, but not hepatic, blood flow and increased (P < .01) hepatic-arterial concentration differences for blood UN. Except for a decrease (P = .01) in hepatic-arterial concentration differences of glutamine, plasma amino acid concentrations were not altered by feeding SF vs DR sorghum. Processing method (steam-flaking vs dry-rolling) or increasing the degree of processing (by decreasing FD) of SF sorghum grain resulted in greater transfer of blood UN to the gut. Reducing FD also linearly increased the absorption of AAN by growing steers, which explains (in part) published responses of superior performance by steers fed SF grains.     

非蛋白氮在家禽日粮中的应用

本文综述了家禽日粮中添加非蛋白氮(NPN)的效果,并分析影响使用效果的主要因素。家禽利用非蛋白氮的机理目前尚无定论,本文推测可能存在3种机制:利用非蛋白氮合成非必需氨基酸(NEAA)、代谢产物负反馈抑制原理和微生物转化利用。家禽日粮中添加非蛋白氮效果很不稳定,影响因素复杂,实际生产中难以把握,现阶段不宜推广使用。     

The metabolic profile of growing lambs fed diets rich in unsaturated fatty acids

The effect of two diets enriched with unsaturated fatty acids – one containing the addition of dried distillers grains with solubles (DGS) and the other the addition of false flax – Camelina sativa cake (CS) – on some metabolic parameters and hormone concentration in growing lambs was determined in this experiment. A total of 21 ram lambs of the Polish Whiteheaded mutton sheep were divided into three groups (the control, receiving DGS and CS). The diets were administered to animals for 6 weeks. During the experiment, peripheral blood was collected. Glucose (GL), total cholesterol (CH), triglycerides (TG), free fatty acids (FFA), insulin (IN), leptin (LE), triiodothyronine (T3) and thyroxine (T4) were assayed in serum. The age‐dependent reduction in CH and TG limited by both experimental diets were observed. A significant increase in FFA concentration was observed in samples collected in the last, that is, third, time period. This was most probably caused by a 12‐h pre‐slaughter fasting period. A significantly lower dynamic of FFA increase in that experimental period was found in animals receiving the experimental feed. Insulin concentration in DGS‐receiving lambs was increased, in contrast to the CS‐receiving lambs, in which it was lower when compared to the control. LE concentration was decreased by both experimental diets, more markedly in the DGS‐receiving animals. No differences between the experimental groups and the control were observed in T3 and T4 concentrations. The effect of 12‐h pre‐slaughter fasting was statistically highly significant for the levels of examined blood markers and hormones, except for TG and IN in the group of lambs receiving the experimental diet with CS.     

Nutrient utilization in lambs fed diets high in sodium or potassium

Twenty-four wether lambs averaging 47 kg were used to study the effects of dietary K and Na additions on metabolism of lambs. Lambs were randomly allotted to four treatments and fed 900 g/d of the following: control diet consisting of 50% ground tall fescue hay and 50% concentrate; K diet calculated to contain 4% K with K added as KCl; Na diet calculated to contain 4% Na with Na added as NaCl, and K-Na diet containing 2% K and 2% Na with K and Na added from the same sources as in the K and Na diets. Water intake and urine excretion were highest for lambs fed the Na diet. Dry matter (DM) and crude protein (CP) digestibilities were similar among treatments. The K-Na diet resulted in decreased (P less than .05) acid detergent fiber (ADF) digestibility compared with lambs fed the Na diet. Nitrogen (N) retention was highest (P less than .05) in lambs fed the K diet and lowest in those fed the Na diet. Rumen NH3-N was lower (P less than .05) in lambs fed the Na diet compared with controls. Rumen K at 2 and 6 h postfeeding was highest (P less than .05) and rumen Na at 6 h lowest (P less than .05) for lambs fed the K diet. Plasma K values at both sampling times were highest (P less than .05) in lambs fed the K diet. At 6 h postfeeding, plasma Mg was higher in control lambs compared with those fed the K-Na diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absorption and metabolism of alpha-ketoglutarate in growing pigs

The portal appearance of enteral alpha-ketoglutarate (AKG) and the effect of enteral or parenteral AKG on portal net appearance of glucose, short-chain fatty acids, alanine, aspartate, glutamate, glutamine, proline and insulin were investigated in three growing pigs. During the experimental samplings the pigs were fed hourly with a standard feed mix with 5% glucose (control), 5% AKG (enteral) or no feed additive but continuously infused with AKG into the mesenteric vein in an amount equivalent to 5% of feed intake (parenteral). The arterial plasma concentration of AKG increased (p < 0.05) following both enteral (from 16+/-2 to 22+/-3 micromol/l) and parenteral (from 16+/-2 to 425+/-27 micromol/l) administration of AKG. With the enteral treatment 4+/-1% of the AKG could be accounted for in the portal vein, however, with the parenteral treatment 86+/-5% could be accounted for in the portal vein. The arterial plasma concentration of proline increased (p < 0.05) with the enteral treatment (365 +/- 3 to 443 +/- 39 micromol/l), but was not affected by the parenteral treatment (p > 0.10). The plasma concentration glutamine decreased (p < 0.05) with the parenteral treatment only. The portal net appearance of proline showed a numerical increase with the enteral treatment but no other affects on arterial concentrations or portal net appearance were found. A small accompanying study showed that only small amounts of enteral AKG was present in the small intestine. It was therefore concluded that enteral AKG has a low availability to peripheral tissues either because it is absorbed and metabolized in the stomach and duodenum or because it is metabolized by microbes in the stomach. The study showed that AKG is metabolized differently following enteral and parenteral application in growing pigs.     

Net nutrient flux in visceral tissues of lambs fed diets differing in supplemental nitrogen source.

Eight multicatheterized wethers (35.9 +/- .8 kg BW) were used in a replicated 4 x 4 Latin square design to measure N retention and net uptake and release of plasma metabolites across the portal-drained viscera (PDV), hepatic (HEP), and total splanchnic (TS) tissues in response to changes in supplemental N source. Treatments selected to provide different amounts of undegradable intake protein (UIP) were urea, soybean meal (SBM), poultry by-product meal (PBM), and bloodmeal:corn gluten meal (BMCGM; 50:50 CP basis). Diets (urea, SBM, PBM, and BMCGM) contained 12.9, 13.8, 13.6, and 13.2% CP, respectively. Periods were 10 d, with total feces and urine collected on d 7 to 10 and blood sampled on d 10. Wethers were fed at 2% of BW in 12 daily portions. Nitrogen retention was 2.2, 3.3, 4.1, and 4.4 g/d for urea, SBM, PBM, and BMCGM, respectively. Urea had less (P < .01) N retention than SBM, PBM, and BMCGM; SBM had less N retention (P < .01) than PBM and BMCGM. Arterial, portal, and hepatic plasma flows were greater (P < .09) for SBM than for PBM and BMCGM (21 vs 16, 17; 84 vs 72, 72; 105 vs 87, 88 L/h). Portal plasma flow was greater (P < .10) for urea than for SBM, PBM, and BMCGM (85 vs 84, 72, 72 L/h). Portal-drained viscera and TS alpha-amino N (AAN) fluxes were less (P < .05) for PBM than for BMCGM (20.5 vs 26.6 and 7.2 vs 15.1 mmol/h), but TS AAN flux was less (P < .05) for urea than for SBM, PBM, and BMCGM (6.9 vs 16.9, 7.2, 15.1 mmol/h). Portal-drained viscera flux and HEP removal of NH3 N were greater (P < .001) for SBM than for PBM and BMCGM (27.7 vs 19.4, 20.6; -28.1 vs -20.0, -21.4 mmol/h). Gut use was less (P = .07) and HEP and TS fluxes of urea N were greater (P < .01) for SBM than for PBM and BMCGM (-4.92 vs -8.32, -7.93; 25.87 vs 16.54, 20.00; 20.95 vs 8.22, 12.07 mmol/h). These data suggest that PBM and BMCGM improved efficiency of N use compared with urea and SBM by reducing urinary N loss.     

Optimizing nitrogen utilization in growing steers fed forage diets supplemented with dried citrus pulp

Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.     

Efficacy of laidlomycin propionate in low-protein diets fed to growing beef steers: effects on steer performance and ruminal nitrogen metabolism

We conducted two experiments to evaluate the effect of the ionophore laidlomycin propionate (LP) on steer performance and ruminal N metabolism. Experiment 1 was a 91-d growth study evaluating the growth and ruminal characteristics of steer calves consuming supplemental LP. Steers (n = 96; 255 +/- 3 kg; four steers/pen; six pens/treatment) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments consisting of two levels of dietary CP (formulated to be 10.5 and 12.5% of DM) with and without LP (11 mg/kg diet DM). Ruminal fluid was collected via stomach tube on d 91 from one steer randomly selected from each pen. No CP x LP interactions were observed with performance data (P > .64). Final weight and total gain were greater (P < .07) for 12.5% CP and LP compared with 10.5% CP and control steers, respectively. Also, DMI was increased (P = .08) with 12.5% CP but not with LP supplementation (P = .36). In addition, ADG and gain:feed ratio were greater (P < .03) for both 12.5% CP and supplemental LP. Ruminal NH3 N concentration was greater (P < .09) with 12.5% CP and LP. Total VFA concentration and molar proportion of acetate were not affected by treatment (P > .11). However, propionate concentration was increased (P < .09) with 12.5% CP and LP, and acetate:propionate was lower (P = .02) with LP supplementation. In Exp. 2, six steers were used in a replicated 3 x 3 Latin square design to compare ruminal fermentation and protein degradation in steers without ionophore feeding or adapted to LP or monensin. In vitro deamination of amino acids by adapted ruminal microbes was also assessed. Ionophore supplementation decreased (P = .07) ruminal NH3 N concentration compared with control steers, and LP increased (P = .02) ruminal NH3 N compared with monensin. Molar proportion of acetate was decreased (P = .02) and propionate increased (P = .01) with ionophore treatment. Consequently, ionophore supplementation depressed the acetate:propionate ratio (P = .01). In situ degradation rate of soybean meal (SBM) CP was greater (P = .09) with ionophore treatment, but estimates of SBM undegradable intake protein were not altered by treatment (P > .25). Microbial specific activity of net NH3 N release and alpha-amino N degradation were decreased (P < .04) with ionophores. Based on this study, LP and monensin did not affect the extent of ruminal degradation of SBM CP but decreased amino acid deamination.     

Growth performance and nitrogen metabolism in weaned pigs fed diets containing different sources of starch

This study was conducted to determine the performance and N metabolism in weaned pigs fed diets containing different sources of starch. Pigs were weaned at 28 days of age, and assigned randomly into 4 soybean meal-based diets containing different sources of starch: corn, brown rice, sticky rice, and Hi-Maize 1043 (resistant starch). There were 12 pigs per treatment group in the growth-performance trial. Additionally, a 4 × 4 Latin design was used for a nitrogen (N) balance study, with 5 days for each experimental period (n = 4). Average daily gains were 0.38, 0.34, 0.31, and 0.28 kg/day (P < 0.01), respectively, for pigs fed the corn, brown rice, sticky-rice, and Hi-Maize 1043 diets. Feed:gain ratios were 1.65, 1.78, 1.95, and 1.86 (P < 0.01), for the above 4 diets, respectively. Fecal N and urinary N excretion as well as the apparent fecal digestibility of crude protein in pigs fed the corn, brown rice, and sticky-rice diets were higher (P < 0.01) compared with pigs fed the Hi-Maize 1043 diet. Collectively, our results indicate that dietary sources of starch affected both growth performance and N utilization in weaned pigs.     

Effects of deoxynivalenol in a wheat ration fed to growing lambs

A wheat diet containing deoxynivalenol (vomitoxin) at 15.6 mg/kg was fed to crossbred lambs for 28 days. Feed consumption, weight gain, and feed efficiency of deoxynivalenol-treated lambs did not differ (P less than 0.05) from those values of controls. Group differences were not noted for hematologic or serum biochemical variables, and gross or microscopic lesions were not observed in treated lambs.     

Protein metabolism in growing pigs fed corn or cassava peel based diets containing graded protein levels

Sixty-four Large White cross Landrace weanling pigs were randomly allotted to eight treatments in a two by four factorial arrangement. The two dietary variables were cassava peel (0 and 40 per cent) and crude protein (20, 15, 10 and 5 per cent). Total serum protein concentration was significantly (P less than 0.01) reduced by protein deficiency and by its interaction with cassava peel. The multiple coefficient of determination (R2) showed that protein intake was the primary factor determining changes in serum protein. R2 values for cyanide intake (independent variable) on serum protein (dependent variable) increased from day 30 to 90 of the trial. Serum urea was increased on the 5 per cent protein diets on days 60 and 90 of the trial. The R2 values for cyanide and protein intake on serum urea concentration increased from day 30 to day 90 of the trial. Serum creatinine increased (P less than 0.05) on the 5 per cent protein diet on day 90 of the trial. The R2 value for the effects of protein intake on serum creatinine was higher than for cyanide intake on days 30 and 90. The results confirm the progressive and pronounced effects of long term cyanide intake on serum nitrogenous metabolites in pigs consuming between 110 and 120 ppm hydrocyanic acid, especially in diets containing 10 per cent or less protein.     

Condensed tannins and nutrient utilization by lambs and goats fed low-quality diets.

In the first of two experiments, four wether lambs (BW = 26.8 kg) and four wether Angora goats (BW = 31.7 kg) were used in two simultaneous 4 x 4 Latin squares to study the influence of condensed tannins (CT) on nutrient usage and concentrations of serum urea N, somatotropin (GH), and insulin (INS) when the animals were fed low-quality diets containing mountain mahogany (MM; Cercocarpus montanus) leaves. Diets were 8% CP and contained 25% or 50% MM (with hay or straw, respectively), either untreated or treated with polyethylene glycol (PEG; molecular weight 3,350) to reduce total reactive CT. Diets treated with PEG and 25% MM diets had less (P less than .05) CT than diets without PEG or those with 50% MM. Diets containing 50% MM resulted in greater N balance and lower serum urea N (P less than .01) than 25% MM diets. Concentrations of GH and INS were similar in animals fed the 25% and 50% MM diets. Reducing CT by adding PEG did not affect N balance or improve nutrient digestion by lambs or goats fed low-quality diets. In Exp. 2, four wether lambs (BW = 28.4 kg) were used in a 4 x 4 Latin square and fed the same diets as animals in Exp. 1 to study the influence of CT on ruminal fermentation and digesta kinetics. Dietary PEG treatment did not affect digesta kinetics except for a 30% increase in ruminal volume; 50% MM diets had faster particulate passage rates (P less than .05) than 25% MM diets. Ruminal ammonia N was greater (P less than .01) in lambs fed PEG-containing or 25% MM diets; however, rate of in situ NDF disappearance was not reduced by the lower ammonia N in the latter diets.     

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.     

Muscle metabolism and real-time ultrasound measurement of muscle and subcutaneous adipose tissue growth in lambs fed diets containing a beta-agonist

Rambouillet X Finn crossbred wether lambs were evaluated for differences in longissimus muscle cross-sectional area and overlaying subcutaneous adipose tissue thickness resulting from the use of the beta-agonist clenbuterol. Treatment groups received 0 and 2 ppm clenbuterol in the diet for approximately 40 d prior to slaughter. Longissimus muscle cross-sectional area and fat depth over the 12th-13th rib juncture were measured by real-time ultrasound before and during administration of the compound. At slaughter, muscle metabolism in vitro and carcass characteristics were measured. Based on comparisons with an initial-kill group of sheep, longissimus muscle cross-sectional area increased in control sheep by 12% (P greater than .05) over the 40-d experimental period, and increased in clenbuterol-fed sheep by 48% (P less than .05). Conversely, subcutaneous fat thickness increased significantly in the control sheep (88%) during this period, but was unchanged in the clenbuterol-fed animals. Warner-Bratzler shear force values of cooked longissimus samples from clenbuterol-fed sheep were significantly greater than shear force values in cooked samples from control lambs; this was not correlated with the extractable neutral lipid content of the muscle. Simple linear regression between ultrasound and carcass measurements of longissimus muscle cross-sectional area and subcutaneous fat thickness yielded correlation coefficients of .80 and .64, respectively. A significantly greater amount of net glycogen synthesis from [U-14C]glucose was observed in longissimus muscle strips from clenbuterol-fed animals than in muscle strips from control sheep.(ABSTRACT TRUNCATED AT 250 WORDS)     

Models to quantify excretion of dry matter,nitrogen, phosphorus and carbon in growing pigs fed regional diets

Modern pig production contributes to many environmental problems that relate to manure, especially in areas with highly intensive production systems and in regions like Asia where the regulative control is not effective. Therefore, the objective of this study was to use three different pig diets varying in dietary protein, fibre and fat as representative for Danish （DK）, Thai （TH） and Vietnamese （VN） pig production to develop and evaluate different approaches to predict/calculate excretion from growing pigs in comparison with the experimentally determined values. Nine female growing pigs were used in a digestibility and balance experiment. Excretion of dry matter （DM）, nitrogen （N）, phosphorus （P） and carbon （C） of the experimental diets were determined. Due to the highest dietary fibre content, VN had the lowest digestibility of N, P and C （73, 49, and 73%, respectively） compared with the DK and TH pig diets. From the known diet composition using standard table values on chemical and nutrient digestibly, high accuracy （bias） and low variation was found and the results could be used for prediction on chemical composition and excretion in faeces and urine in growing pigs. Calculation based on standard values regarding nutrient retention in the pig body as used in the Danish manure normative system （DMNS） showed likewise to be quite useful for quantifying the total excretion of N and P. Overall, the results demonstrate that simple models that require cheap and normally available information on dietary nutrients can give useful information on nutrient excretion in growing pigs.