不同尿素水平对氨化秸秆消化率的影响

为了探索不同尿素水平对氨化秸秆品质的影响,试验采用尼龙袋法测定尿素浓度分别为2.0%、4.5%、7.0%DM 的氨化秸秆及未氨化秸秆在山羊瘤胃48 h 的养分消失率。试验结果表明,氨化稻草秸秆在瘤胃48 h的干物质(DM)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)的降解率比未氨化稻草均有不同程度的增加,尤以尿素浓度为4.5%DM 的降解率为最高(p<0.05)。     

含水量对尿素氨化小麦秸秆效果的影响

用袋装法氨化风干小麦秸来探讨尿素比例一定时不同含水量对氨化效果的影响。氨化处理过程以小麦秸含水量的不同设7个处理组,它们分别是：含水量为20％（处理Ⅰ）、25％（处理Ⅱ）、30％（处理Ⅲ）、35％（处理Ⅳ）、40％（处理V）、45％（处理Ⅵ）和50％（处理Ⅶ）。氨化时的温度为20—25℃。经过21d的氨化,调制出7种含水量不同的氨化小麦秸,对其进行感官鉴定和营养成分分析并与未氨化小麦秸作对照。结果表明,尿素氨化风干小麦秸秆时30％～45％的含水量氨化效果好,感官品质好,且CP提高幅度和NDF降低幅度均较大。表明河西地区用尿素（3．5％）氯化风干小麦秸秆最适宜的含水量为30％一45％。     

不同尿素水平对氨化秸秆消化率的影响

为了探索不同尿素水平对氨化秸秆品质的影响,试验采用尼龙袋法,测定尿素浓度分别为2．0％、4．5％、7．0％DM的氨化秸秆及未氨化秸秆在山羊瘤胃48h的养分消失率。试验结果表明,氨化稻草秸秆在瘤胃48h的干物质（DM）、中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）的降解率比未氨化稻草均有不同程度的增加,尤以尿素浓度为4．5％DM的降解率为最高（P〈0．05）。     

小麦秸秆的氨化处理

氨化处理是化学处理的一种，也是迄今为止应用最为广泛的一种秸秆处理方法。现介绍实用秸秆的氨化处理方法，供农民朋友参考：１麦秸氨化的好处１．１可将秸秆有机物消化率提高１０％～１２％，粗蛋白含量由３％～４％提高到８％，甚至更高。１．２处理后的秸秆适口性好，采食时间较不处理时大大缩短。１．３氨可防止饲料霉变，还能杀死野草籽，可很好地保存含水率偏高的粗饲料。２氨化方法２．１尿素（或碳铵）处理法根据秸秆重量，称量出尿素（剂量见下表），将尿素溶于水，拌匀，再用喷壶喷到切短的秸秆上，边喷洒，边搅拌，一层层喷洒，…     

小麦秸秆氨化技术简介

目前小麦秸秆很多直接还田利用,但小麦秸秆直接还田不利于播种和出苗,易造成各种病虫害增多,杂草难根除及土壤过度蓬松等问题。另一方面,小麦秸秆虽然营养价值不高,但经过氨化处理后,蛋白含量、可消化性等均有提升,可以作为牛、羊等草食动物的饲料,特别是在蛋白饲料价格较高时具有重要的经济价值。     

氨化剂和氨化条件对水稻秸秆氨化的影响

试验研究了不同氨化试剂和不同氨化条件对水稻秸秆氨化效果的影响。水稻秸秆经过氨化后,粗蛋白含量显著提高,质地改善;氨水是进行水稻秸秆氨化的适宜试剂,适宜添加量为8%(含氨20%);水稻秸秆氨化的适宜水分含量为30%,切短2 cm,密度为60 kg/m3;高温氨化秸秆不易长期保存,最好立即利用,低温氨化秸秆则可保存较长时间。     

怎样制作氨化秸秆饲料

氨化就是利用液氨、尿素、碳铵、氨水等氨化剂 (可任选一种 )对秸秆进行处理。氨化后的秸秆粗蛋白质可增加 1～ 2倍 ,适口性也大为改善 ,采食量可提高2 0 %左右。氨化还可以防止饲料霉坏。氨化秸秆的制作以尿素处理法最佳 ,因为尿素储存运输方便 ,处理时所用的设备少 ,不象液氨或氨水那样处理不当会对人体有害 ,在农村一家一户利用尿素很方便 ,处理效果仅次于液氨。方法是 :根据秸秆 (如稻草 )的重量 ,计算出尿素用量。每 1 0 0千克干稻草用尿素 4千克 ,加水 3 0～ 40千克。将地面平整后铺上塑料薄膜 ,在上面堆稻草 ,薄膜四周要留出 1米左右…     

不同尿素水平对青山羊血清尿素氮的影响

选用4只体重约18kg的健康青山羊，采用4×4拉丁方设计，结合氮平衡试验研究了不同尿素水平下血清尿素氮(SUN)浓度随时间的变化。结果表明不同尿素水平极显著影响SUN浓度(P＜0.01)，饲喂尿素后SUN的浓度显著高于饲喂前，SUN浓度随时间呈动态变化，出现高峰的时间比瘤胃氨浓度出现高峰的时间平均推迟1～2h。求得尿素水平与SUN浓度的最佳回归方程为     

Effect of different levels of dietary nitrogen supplementation on the relative blood urea nitrogen concentration of beef cows

The objective of this study was to determine if individual beef cows in a herd have an inherent ability to maintain their blood urea nitrogen (BUN) concentration when exposed to different levels of dietary nitrogen supplementation. Ten Hereford and 12 Nguni cows, aged between 2 and 16 years, were utilized in two crossover experiments. In the first experiment, cows were exposed to two diets: a balanced diet with a crude protein (CP) level of 7.9% and a modified diet with a CP level of 14%, formulated by adding 20 kg of feed grade urea per ton of the balanced diet. At the end of the first crossover experiment, cows received the balanced diet for 1 week. The second component utilized the same cows wherein they were fed the balanced diet in addition to another modified diet containing only 4.4% CP. Blood urea nitrogen concentration was measured 22 times (twice weekly) from each cow during both components of the study. A linear mixed-effects model was used to assess whether baseline BUN concentration (measured 1 week before onset of the study) was predictive of subsequent BUN concentration in individual cows. Breed, cow age, body condition score, and body mass were also evaluated for their effects on BUN concentrations. Albumin, beta hydroxybutyric acid (BHBA), glucose, and total serum protein (TSP) were compared between diets within each breed. Baseline BUN concentration was a significant predictor of subsequent BUN concentration in individual cows (P = 0.004) when evaluated over both components of the study. Breed (P = 0.033), the preceding diet (P < 0.001), current diet (P < 0.001), and the week during which sampling was performed (P < 0.001) were also associated with BUN concentration. Results suggest that beef cattle (within a herd) have an inherent ability to maintain their BUN concentration despite fluctuations in levels of available dietary nitrogen.

     

Influence of slow-release urea on nitrogen balance and portal-drained visceral nutrient flux in beef steers

Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on portal-drained visceral (PDV) nutrient flux, nutrient digestibility, and total N balance in beef steers. Multi-catheterized steers were used to determine effects of intraruminal dosing (Exp. 1; n = 4; 319 +/- 5 kg of BW) or feeding (Exp. 2; n = 10; 4 Holstein steers 236 +/- 43 kg of BW and 6 Angus steers 367 +/- 46 kg of BW) SRU or urea on PDV nutrient flux and blood variables for 10 h after dosing. Intraruminal dosing of SRU (Exp. 1) prevented the rapid increase in ruminal ammonia concentrations that occurred with urea dosing (treatment x time P = 0.001). Although apparent total tract digestibilities of DM, OM, NDF, and ADF were not affected by treatment (P > 0.53, Exp. 2), SRU increased fecal N excretion (49.6 vs. 45.6 g/d; P = 0.04) and reduced apparent total tract N digestibility (61.7 vs. 66.0%; P = 0.003). Transfer of urea from the blood to the gastrointestinal tract occurred for both treatments in Exp. 1 and 2 at all time points with the exception for 0.5 h after dosing of urea in Exp. 1, when urea was actually transferred from the gastrointestinal tract to the blood. In both Exp. 1 and 2, both urea and SRU treatments increased arterial urea concentrations from 0.5 to 6 h after feeding, but arterial urea concentrations were consistently less with SRU (treatment x time P < 0.001, Exp. 1; P = 0.007, Exp. 2). Net portal ammonia release remained relatively consistent across the entire sampling period with SRU treatment, whereas urea treatment increased portal ammonia release in Exp. 1 and tended to have a similar effect in Exp. 2 (treatment x time P = 0.003 and P = 0.11, respectively). Urea treatment also increased hepatic ammonia uptake within 0.5 h (treatment x time P = 0.02, Exp. 1); however, increased total splanchnic release of ammonia for the 2 h after urea treatment dosing suggests that PDV ammonia flux may have exceeded hepatic capacity for removal. Slow-release urea reduces the rapidity of ammonia-N release and may reduce shifts in N metabolism associated with disposal of ammonia. However, SRU increased fecal N excretion and increased urea transfer to the gastrointestinal tract, possibly by reduced SRU hydrolysis or effects on digestion patterns. Despite this, the ability of SRU to protect against the negative effects of urea feeding may be efficacious in some feeding applications.     

Effect of nitrogen intake on nitrogen recycling and urea transporter abundance in lambs

Urea recycling in ruminants has been studied extensively in the past, but the mechanisms regulating the amount of urea recycled or excreted remain obscure. To elucidate the role of urea transporters (UT) in N recycling, nine Dorset-Finn ewe lambs (20.8 +/- 0.8 kg) were fed diets containing 15.5, 28.4, and 41.3 g of N/kg of DM for 25 d. Nitrogen balance and urea N kinetics were measured during the last 3 d of the period. Animals were then slaughtered and mucosa samples from the rumen, duodenum, ileum, and cecum, as well as kidney medulla and liver, were collected. Increasing N intake tended to increase N balance quadratically (1.5, 5.1, and 4.4 +/- 0.86 g of N/d, P < 0.09), and linearly increased urinary N excretion (2.4, 10, and 16.5 +/- 0.86 g N/d, P < 0.001) and plasma urea N concentration (4.3, 20.3, and 28.4 +/- 2.62 mg of urea N/dL, P < 0.001), but did not affect fecal N excretion (5.0 +/- 0.5 g of N/d; P < 0.94). Urea N production (2.4, 11.8, and 19.2 +/- 0.83 g of N/d; P < 0.001) and urinary urea N excretion (0.7, 7.0, and 13.4 +/- 0.73 g N/d; P < 0.001) increased linearly with N intake, as well as with the urea N recycled to the gastrointestinal tract (1.8, 4.8, and 5.8 +/- 0.40 g of N/d, P < 0.001). No changes due to N intake were observed for creatinine excretion (518 +/- 82.4 mg/d; P < 0.69) and clearance (46 +/- 10.7 mL/min; P < 0.56), but urea N clearance increased linearly with N intake (14.9, 24.4, and 34.9 +/- 5.9 mL/min; P < 0.04). Urea N reabsorption by the kidney tended to decrease (66.3, 38.5, 29.1 +/- 12.6%; P < 0.06) with increasing N content of the diet. Increasing the level of N intake increased linearly the weight of the liver as a proportion of BW (1.73, 1.88, and 2.22 +/- 0.15%, P < 0.03) but only tended to increase the weight of the kidneys (0.36, 0.37, and 0.50 +/- 0.05%, P < 0.08). Urea transporter B was present in all the tissues analyzed, but UT-A was detected only in kidney medulla, liver, and duodenum. Among animals on the three diets, no differences (P > 0.10) in UT abundance, quantified by densitometry, were found. Ruminal-wall urease activity decreased linearly (P < 0.02) with increasing level of N intake. Urease activity in duodenal, ileal, and cecal mucosa did not differ from zero (P > 0.10) in lambs on the high-protein diet. In the present experiment, urea transporter abundance in the kidney medulla and the gastrointestinal tract did not reflect the increase in urea-N reabsorption by the kidney and transferred into the gut.     

Pre-breeding blood urea nitrogen concentration and reproductive performance of Bonsmara heifers within different management systems

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n?=?369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or palpation was performed 4–8 weeks after a 3-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP, respectively. After stratifying for herd and adjusting for age, heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P?=?0.011). In the herd with the highest estimated nitrogen intake (n?=?143), heifers with relatively higher BUN were less likely to become pregnant (P?=?0.013) and if they did, it was only later during the breeding season (P?=?0.017), after adjusting for body mass. These associations were not present in the herd (n?=?106) with the lowest estimated nitrogen intake (P?>?0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.     

Utilization of urea nitrogen in young calves

The influence of an increasing intake of urea in feed rations for calves on its levels in blood plasma and urine, development of health condition, weight gains and on other biochemical characteristics in the blood of calves was studied. The experimental group (n = 4) received urea in feed ration from the 17th day of age, at the beginning in the preparation Syrur, later on (from the 66th day) in the synthetic form only. The feed ration of the control group (n = 3) differed only in the zero content of urea. Over the period of ten weeks the blood was sampled for biochemical examination twice a week, since the 52nd day of age urine was also taken at the same intervals. Starting the 24th day of age, the levels of urea in the blood plasma of experimental animals were significantly higher (P less than 0.05). The concentrations of urea in the urine of the animals belonging to the experimental group were also higher, however, the differences in the average values were not significant. In both groups of animals under study no significant differences in the content of vitamin A, concentration of total protein, glucose, bilirubin, activities of aspartate aminotransferase (AST), gammaglutamyl transferase (GMT) and lactate dehydrogenase (LD) were observed. The average daily weight gains were higher in the calves of the control group, however, the differences were not significant. Over the whole experimental period the health condition of both groups of calves was good.