Influence of single applications of nitrogen on white clover nitrogen fixation in autumn and winter dairy pastures in south‐west Victoria,Australia

Abstract

Effects of nitrogen (N) (0, 15, 30, 45 and 60 kg N ha^?1) applied at five different times during autumn and early winter on the N fixation of Trifolium repens L. (white clover) in Lolium perenne L. (perennial ryegrass) / white clover pastures were examined (Experiment 1). Effects of applying different N fertilisers (e.g. urea and ammonium nitrate) at 45 kg N ha^?1 in autumn, with and without phosphorus (P), potassium (K) and sulphur (S) on N fixation were also tested (Experiment 2). In Experiment 1, percentage N derived from the atmosphere (percent Ndfa) by white clover varied between 87% and 91% in the period after (24 to 36 days) N application. Increasing rates of N and time of application did not influence percent Ndfa. The amount of N fixed by white clover ranged from 0.8 to 3.7 kg N ha^?1 in the period after N application. Increasing rates of applied N produced a significant (P<0.05) linear increase in the amount of N fixed. In Experiment 2, percent Ndfa and amount of N fixed (1.9 to 4.1 kg N ha^?1) were unaffected by different N fertilisers, with and without P, K and S, in the period after (37 days) fertiliser application. For both experiments, fertiliser N increased dry matter yield while having no effect on white clover composition. It is concluded that single applications of N during the autumn and early winter benefit pasture growth without adversely affecting white clover N fixation or clover composition. This finding, however, will require further investigation.     

硼、钼、锌与大量元素配施对紫花苜蓿草产量和品质的影响

在氮磷钾肥料基础上,研究硼、钼、锌配施对紫花苜蓿草产量和品质的影响.结果表明:施氮磷钾肥可以提高苜蓿干草产量,降低叶茎比,但对其粗蛋白质含量的影响不大;在氮磷钾肥适量的基础上,硼、钼、锌合理配施可以增加苜蓿干草产量,其中单施硼(2.0 kg/hm2)或锌(1.5 kg/hm2)增产显著(P＜0.05),分别较对照增产29.0%和25.9%;硼、钼、锌配施对各茬次粗蛋白质含量的影响不同;单施锌苜蓿粗蛋白质含量呈降低趋势,单施钼粗蛋白质含量呈增加的趋势.     

Effects of drying methods on nitrogen and energy concentrations in pig feces and urine, and poultry excreta

Accurate estimations of nutrient digestion and retention are critical in nutrient balance and feed evaluation studies because errors that occur are often additive. However, there is no standard universal method for drying feces, urine, or excreta before laboratory analysis. The objective of this study was to evaluate the impact of 4 different drying methods on nutrient concentrations in feces, urine, and excreta. Twelve individually penned growing pigs were fed 1 of 3 diets and 16 pens of 10 growing broilers were fed 1 of 4 diets that differed in NDF and CP. Feces, urine, and excreta that varied in nutrient composition were collected after 7 d of diet adaptation. Samples were dried using 1 of 4 methods: undried (UD), freeze-dried (FD), oven-dried at 55 °C for 48 h (OD55), or oven-dried at 100 °C for 48 h (OD100), after which DM, GE, N, C, and S were determined. In swine feces, drying resulted in a loss of GE (P < 0.10) and S (P < 0.01) by 5 and 58%, respectively, compared with UD feces. There was no difference (P ≥ 0.36) among drying method on DM, GE, N, C, or S concentrations. There were no differences (P ≥ 0.12) in urinary GE due to drying or between drying methods; however, urinary DM was greatest by FD compared with OD (P < 0.05) and greater for OD55 compared with OD100 (P < 0.01). In poultry excreta, GE (P < 0.05), N (P < 0.10), and S (P < 0.01) were reduced by drying by an average of 6, 10, and 66%, respectively. There were no differences (P ≥ 0.50) among drying methods except FD excreta had a greater S concentration than OD (P < 0.10). Regardless of drying method, some GE and N loss appears to be inevitable, but there is no apparent advantage between FD and OD. The apparent greater S losses warrant further investigation.     

施氮水平对甜高粱主要农艺性状及其与干物质产量相关关系的影响

为探求甜高粱干物质产量与主要农艺性状的关系以及不同施氮水平对两者相互关系的影响,本研究以大力士甜高粱为材料,采用完全随机区组设计进行两年田间试验,测定不同施氮水平(0,100,200,300,400,500 kg N/hm²)下甜高粱的株高、茎粗、绿叶数、茎叶比、鲜干比、叶面积指数和干物质产量7个参数,并对上述参数进行了相关性分析、多元回归分析和通径分析。试验结果表明,株高,叶面积指数和茎粗均与干物质产量呈极显著正相关关系(P<0.01),相关系数分别为r=0.921^**,r=0.865^**,r=0.758^**。通径分析表明,株高是决定干物质产量的主要农艺性状,茎叶比和叶面积指数与干物质产量的关系对不同施氮水平有不同响应。较低施氮水平(0,100 kg N/hm²)下,茎叶比对干物质产量的直接作用最大(P=0.925),叶面积指数对干物质产量的直接作用最小(P=0.162)。中等施氮水平(200,300 kg N/hm²)下,茎叶比对干物质产量的影响降低(P=0.073),叶面积指数对干物质产量的直接作用增加(P=0.797)。较高施氮水平(400,500 kg N/hm²)下,茎叶比和叶面积指数对干物质产量的直接作用均为负值(P=-0.125,P=-0.040)。施氮量为200~400 kg N/hm²时,干物质产量较高。综上可知,在较高施氮条件下,合理密植是获得较高干物质产量的关键。当供氮水平较低时,应注意收获时间的选择,以便更好地兼顾干物质产量和饲草营养价值。     

Effect of plant height at cutting,source and level of fertiliser on yield and nutritional quality of Napier grass (Pennisetum purpureum (L.) Schumach.)

Napier grass (Pennisetum purpureum (L.) Schumach.) was studied using a 5 x 3 factorial experiment arranged in a randomised complete block design with three replications. The treatments were five fertiliser applications (0kg ha^-1 N, 46kg ha^-1 N and 92kg ha^-1 N, 1t ha^-1 and 2t ha^-1 cattle manure) and three plant heights at cutting (0.5m, 1m and 1.5m). The mean dry matter (DM) yield was 8.21t ha^-1 per cut but increased when the plant height at cutting increased and when the level of N fertilisation increased (P<0.05). Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), cellulose, calcium, in vitro dry matter digestibility (IVDMD) and metabolisable energy were significantly (P<0.05) affected by plant height at cutting while total ash, crude protein (CP), ADF-ash, hemicelluose and phosphorus were affected by both plant height at cutting and fertiliser level. As plant height at cutting increased from 0.5m to 1.5m, IVDMD declined from 71.74% to 61.03% (P<0.05). Correlations between IVDMD versus CP, NDF, ADF, ADL, cellulose and hemicellulose were high with r = 0.92, -0.94, -0.96, -0.98, -0.83 and 0.74, respectively. CP yield per hectare per day of growth was highest for the 0.5m height at cutting, whereas the digestible DM yield was highest at both the 0.5m and 1.0m cutting height. The results of the present study suggest that Napier grass could be categorised under medium to high quality forage if cut at 0.5m or 1.0m height.     

氮磷钾配施对百喜草干物质积累及其动态变化的影响

在1999年N、P、K单施的基础上,于2000年进行了N、P、K的4种配比施肥对百喜草干物质积累动态变化的研究,结果表明,N P K、N P、N K三个组合增产效果显著,干物质积累量分别达到14.61,14.34,13.80 t/hm2,比单施N、P、K和P K的效果好.所有处理的干物质积累量增长与生长时间的关系曲线皆呈"S"型,干物质积累量增长最佳时间为萌动生长后的125 d左右,含N组合在该时间段增长明显快于P K组,N素对百喜草的增产具有主导作用.在百喜草生长期内,N、P、K配比施用中,百喜草干物质积累量(Y)与生长时间(X)的回归方程可用Logistic 生长曲线拟合,相关系数呈极显著水平,可用于施肥对百喜草干物质积累的动态预测.通过对Logistic 生长曲线的分析表明,N的主导效应主要通过显著地增加线性期历时、缩短指数期和衰减期的历时来实现.     

磷、钾、硫肥对贝斯莉斯克俯仰臂形草生产性能的影响

试验表明,磷肥和钾肥对俯仰臂形草种子产量、干物质产量无显著影响,但能有效提高种子的质量,种子净度平均分别提高16.7%和23.7%。施硫酸钙(0-100kg/hm2)能显著提高臂形草的种子产量,对种子质量和干物质产量无显著影响。     

Sulfate supplementation of Angora goats: metabolic and mohair responses.

Eight castrated male Angora goats were used in a repeated, simultaneous 4 x 4 Latin square designed experiment to evaluate metabolic and mohair responses of Angora goats to sulfate supplementation. Goats had ad libitum access to isonitrogenous diets containing a .16 (basal), .23, .29, or .34% S (DM basis), which yielded N:S ratios of 12.7, 8.3, 6.8, or 5.5:1. Feed intakes were not affected (P greater than .20) by dietary S level. Quadratic increases (P less than .05) to S supplementation were observed in grease and clean mohair production, grease and clean staple strength, and staple length. Mohair diameter, med fiber, kemp fiber, S, and cysteine contents were not affected (P greater than .05) by supplemental S. Averaged across the prefeeding, 2, 4, and 6 h postprandial sampling times, ruminal pH, ammonia N, total S, organic S, protein S, and plasma urea N and organic S concentrations were quadratically increased (P less than .05) by supplemental S. Ruminal sulfate S, total sulfide S, and plasma sulfate S were linearly increased (P less than .05) by supplemental S. Retention of N and mohair S yield exhibited quadratic increases (P less than .05), but S retention exhibited a linear increase (P less than .001) with increased S intake. Calculated by regression, the optimum dietary S concentration for maximum clean mohair production was .267% of dietary DM for a N:S ratio of 7.2:1, suggesting that the National Research Council N:S ratio of 10:1 is inadequate for Angora goats. The optimum level of digestible S was calculated to be .18% of the diet DM.     

Sulfate supplementation of alpine goats: effects on milk yield and composition, metabolites, nutrient digestibilities, and acid-base balance.

Effects of sulfate supplementation on milk yield and composition, ruminal and blood metabolites, acid-base status, and nutrient digestibilities were determined using 30 multiparous, lactating Alpine does. Goats were fed isonitrogenous diets containing .16 (basal), .26, or .36% S (DM basis) during a 13-wk lactation trial that coincided with wk 3 to 15 of lactation. During wk 16 to 17, four does from each treatment were placed in a metabolism crate to measure nutrient digestibility and balance. Feed intake, yield of 4% fat-corrected milk, and milk S content were not affected by added S, but the goats fed the .26% S diet had a trend of higher persistency of lactation (P < .20). During wk 10 and 15 of lactation, milk solids-not-fat percentage was higher (P < .10) for does fed the .26% S diet. Sulfur supplementation resulted in quadratic decreases in ruminal ammonia N (P < .05) in wk 15 and in plasma urea N in wk 10 and 15 (P < .05) but in linear increases (P < .05) in ruminal protein S concentrations throughout the experiment. Added S had little effect on blood acid-base status. Apparent digestibilities of DM, OM, ash, ADF, and GE were increased linearly (P < .10) by added S. The milk N:S ratio remained constant. Increasing S from .16 to .26% of diet DM was beneficial to lactating Alpine goats during early lactation.     

Relative bio-availability and utilisation of phosphatic fertilisers as sources of phosphorus in broilers and layers

1. Different concentrations of non-phytate phosphorus (NPP, 2.5, 3.0, 3.5, 4.0 and 4.5 g/kg diet) were given to broilers (8 to 42 d of age) to establish regressions between dietary NPP concentration and body weight gain and tibia ash content. Second and third experiments were conducted to study the feasibility of utilisation of different phosphatic fertilisers [ammonium phosphate (AP), ammonium polyphosphate (APP), single super phosphate (SSP), NPK (17:17:17, NPK) and NP (28:28:0, NPK)] in commercial broilers (8 to 42 d) and White Leghorn layers (252 to 364 d). 2. Phosphatic fertilisers were incorporated both in broiler (10 g calcium and 4.5 g NPP/kg) and layer (35 g calcium and 3.5 g NPP/kg) diets by replacing dicalcium phosphate (DCP) in toto. 3. The logarithmic curves obtained for predicting the body weight gain and tibia ash content at different levels of NPP used in experiment 1 were Y = 156.27 + 2,468.8 logX (r2= 0.958) and Y = 530.82 + 144.26 log X (r2 = 0.916), respectively. 4. Body weight gain and food intake in broilers given APP- or NP-supplemented diets were comparable to these in the DCP-fed group. Feeding of NPK, AP or SSP resulted in significant depression in weight gain and food intake and high excreta moisture content. Food/gain, Ca and P contents in tibia ash and serum were not influenced by the use of phosphatic fertilisers as P sources in broiler diets. 5. Tibia ash content in broilers fed on diets containing fertilisers was either similar to or significantly higher than that in the DCP-fed group. Broilers on AP or SSP retained more P and had higher tibia ash content than those on DCP. AP, SSP or NPK caused degenerative and necrotic changes in liver, kidney and intestine of broilers. 6. Relative bio-availability of P from APP or NP was better for body weight gain than AP, SSP or NPK, while the reverse was true for bone calcification. 7. APP and NP gave hen-d egg production similar to that of DCP-fed layers. Food intake was significantly reduced in layers fed on diets containing fertilisers. However, food/egg mass, egg weight and serum Ca and inorganic P contents were not influenced by inclusion of fertilisers in layer diets. 8. Except for AP, inclusion of fertilisers in layer diets reduced shell weight and shell thickness compared with the DCP-fed group. However, no apparent eggshell defects were found which could be attributable to diet. 9. Results of these experiments suggest that APP and NP can be used as the sole source of P both in broiler and layer diets, replacing DCP in toto. However, when utilising these P sources in layers, due attention should be given to shell quality. Fertilisers containing high F (AP and SSP) or K (NPK) reduced performance in broilers and layers and caused microscopic changes in liver, kidney and intestine in broilers.     

刈割后氮肥施用对饲料油菜地上部产量及品质的影响

为进一步在湖北地区冬闲田推广饲料油菜(Brassica campestris)的种植,以饲料油菜1315为试验材料,在湖北省冬闲田研究刈割后氮肥施用对饲料油菜地上部产量及品质的影响。结果表明,第1次刈割后,施用氮肥能显著增加饲料油菜地上部产量(P0.05),与不施氮肥处理(N_0)相比,施用17.25kg·hm~(-2)(N_1)和34.5kg·hm~(-2)(N_2)饲料油菜干草产量分别增加了50.0%和75.0%,粗灰分产量分别提高了45.7%和53.2%,粗纤维产量分别提高了50.7%和90.4%,粗蛋白产量分别提高了84.5%和159.3%,粗脂肪产量分别提高了53.9%和83.8%,可溶性糖产量分别提高了64.7%和68.5%,提升了饲料油菜的生产水平。综合考虑,在湖北地区冬闲田种植饲料油菜,为了提高油菜产量和品质,建议在第1次刈割后追施30kg·hm~(-2)。     

德宏象草氮、磷、钾优化施肥组合试验

采用正交试验设计,以单次干物质产量、年总干物质产量、株高、分蘖数为指标,测定了氮、磷、钾不同组合对德宏象草Pennisetum purpureum生长的影响.分别采用极差分析法和方差分析法对试验结果进行了分析,结果表明,氮、磷、钾最佳组合为尿素(900 kg/hm2) 钙镁磷(600 kg/hm2) 硫酸钾(150 kg/hm2),各因素对产量的贡献大小顺序为氮＞钾＞磷.刈割5次时,干物质年均产量可达40.41 t/hm2.不同施肥组合之间株高、单次产量、年总干物质产量差异显著,但分蘖数差异不显著.回归分析说明,单次产量与株高之间存在显著的相关性,但分蘖数与产量之间相关性不显著.     

Nitrogen, phosphorus and potassium utilization and their cycling in a beef-forage production system

The objective of this study was to quantify nitrogen (N), phosphorus (P) and potassium (K) utilization and their cycling in a beef-forage production system. A survey was conducted at the Kyoto University experimental farm in Kyoto Prefecture, Japan, and included 9.5 ha of meadow and about 160 head of beef cattle. Forages cultivated on the meadow were ensiled and offered to breeding cows. The whole farm was regarded as a beef-forage production system. The system consisted of three components: animals, manure and soil/crop. Nutrient inputs, flows through the soil-plant-animal pathway and outputs were quantified for 2 periods for the whole farm. Nutrient utilization was evaluated by nutrient balances, utilization efficiencies (ratio of nutrient export to nutrient input) and cycling index. The average nutrient balances of N, P and K for the whole farm (kg/year/ha) were 435.7, 136.3, and 262.8, and the average nutrient utilization efficiencies were 0.08, 0.06, and 0.01, respectively. The characteristics of nutrient balances and utilization efficiencies for each component differed among the nutrients. The average cycling indices for N, P and K were 0.19, 0.17 and 0.49, respectively. This study illustrates the importance of internal nutrient cycling for improving nutrient utilization in beef production systems.     

Voedings‐ en produksiestudies op Cenchrus ciliaris L. cv. Molopo 1

Die waarskynlike optimum makrovoedingselementpeile vir Cenchrus ciliaris cv. Molopo, in dpm, deur middel van sandkultuurstudies bepaal, is: N‐140, P‐31, K‐130, S‐6, Ca‐20 en Mg‐5. Die cultivar is die gevoeligste vir tekorte aan N, P, K en S. Hoë Ca‐ (600 dpm) en Na‐konsentrasies (500 dpm by opkomende saailinge en 1 000 dpn. na die 4‐blaarstadium) het verlaagde produksie (in die geval van Ca en Na) en hoë saailingverliese (in die geval van Na) tot gevolg gehad. N, P en moontlik ook S, is die beperkende elemente tot verhoogde produksie op ‘n grond van die Bontbergserie (Huttonvorm). In die Vivo‐Dendron‐omgewing is DM‐opbrengs betekenisvol verhoog deur N, maar nie deur P nie. Grondbewerking tussen die rye het DM‐opbrengs betekenisvol vanaf die tweede groeiseisoen op droëland verhoog, maar nie onder besproeiing nie.     

Feed intake,digestibility, nitrogen utilization,ruminal condition and blood metabolites in wethers fed ground bamboo pellets cultured with white‐rot fungus (Ceriporiopsis subvermispora) and mixed with soybean curd residue and soy sauce cake

Three types of bamboo pellets as a ruminant feed: P1 (ground bamboo (GB) cultured with the fungus Ceriporiopsis subvermispora (CGB) : soybean curd residue (T) : soy sauce cake (S) in a 5:4:1 ratio on a dry matter (DM) basis); P2 (GB : T : S = 5:4:1 on a DM basis); and P3 (CGB : T : S = 5.5:0.8:3.7 on a DM basis) were prepared. Four wethers were assigned in a 4 × 4 Latin square design experiment to evaluate the applicability of the bamboo pellets. The experimental treatments were C (control): fed alfalfa hay cubes (AC) only, and T1, T2 and T3: fed P1, P2, and P3 with AC by 1:1 on a DM basis, respectively. The digestibility of the DM, organic matter and acid detergent fiber of P1 were significantly higher than those of P2 and P3 (P < 0.05). The total digestible nutrient (TDN) contents of AC, P1, P2 and P3 were 56.5%, 60.2%, 53.2% and 47.0%, respectively. No significant differences in nitrogen retention or ruminal pH and NH₃ were observed among the treatment groups. The results indicate that bamboo pellets cultured with C. subvermispora and mainly mixed with soybean curd residue improved nutritional quality of ground bamboo because of its high digestibility and TDN content.     

Effects of copper supplementation on feedlot performance, carcass characteristics, and rumen sulfur metabolism of growing cattle fed diets containing 60% dried distillers grains

The effects of 3 supplemental Cu concentrations on feedlot performance, mineral absorption, carcass characteristics, and ruminal S metabolism of cattle fed diets containing 60% dried distillers grains with solubles (DDGS) were evaluated in 2 experiments. Experiment 1 was conducted with 84 Angus-cross yearling steers and heifers (initial BW = 238 ± 36 kg), which were blocked by gender and allocated to 12 pens. Supplemental dietary Cu (tribasic copper chloride) treatments were: 1) 0 mg Cu/kg diet DM, 2) 100 mg Cu/kg diet DM, 3) 200 mg Cu/kg diet DM. The remainder of the diet was DDGS (60%), grass hay (10%), pelleted soy hulls (15%), and a vitamin-mineral supplement (15%). Diets were offered ad libitum throughout the finishing phase (168 d). Three cattle from each pen (n = 36) were harvested on d 168 and carcass data and liver samples were collected. Copper supplementation did not affect ADG (P = 0.22). However, the nonsignificant trend for increased ADG and decreased DMI led to a linear increase (P = 0.02) feed efficiency (G:F = 0.167, 0.177, and 0.177 for 0, 100, and 200 mg Cu/kg diet DM, respectively). The apparent absorption of Cu decreased quadratically (P = 0.07) and the apparent absorption of Mn and Zn were decreased linearly (P = 0.03 and P = 0.05, respectively) with increased Cu supplementation. Cattle supplemented with 100 or 200 mg Cu/kg diet DM had greater liver Cu concentrations (P < 0.01) than cattle that were not supplemented with Cu. There were no treatment effects (P > 0.10) on HCW, LM area, USDA yield grade, backfat, or marbling score. Experiment 2 was conducted with 6 ruminally fistulated steers that were fed the same diets as in Exp 1 in a replicated 3 × 3 Latin Square design. Copper supplementation did not affect (P > 0.10) ruminal pH or liquid S(2-) concentrations in steers consuming 60% DDGS diets (total dietary S = 0.55%). From 3 to 9 h after feeding, H(2)S gas concentration was decreased in those cattle supplemented with 100 mg Cu/kg diet. Concentration of H(2)S gas did not differ among cattle supplemented with 0 or 200 mg Cu/kg diet DM on 60% DDGS diets. Supplemental Cu improved feed efficiency in cattle consuming diets containing 60% DDGS; however, effects of Cu on rumen S metabolism were minimal even when supplemented at twice the maximum tolerable limit for beef cattle (NRC, 2000).     

聚谷氨酸硫基复合肥在甜高粱和多花黑麦草上的肥效

为了评价聚谷氨酸硫基复合肥(S-based γ-PGA fertilizer)在甜高粱(Sorghum bicolor)和多花黑麦草(Lolium multiflorum)上的肥效,以尿素和硫基复合肥(S-based fertilizer)为对照,采用盆栽试验,研究了不同施氮水平(75、150、225 kg·hm-2)下聚谷氨酸硫基复合肥对甜高粱和多花黑麦草生产性能及氮素利用效率的影响.结果表明,聚谷氨酸硫基复合肥处理的甜高粱产量、粗蛋白含量及氮素利用效率在1 50和225 kg·hm-2两个施氮水平下均优于对照(P＜0.05);多花黑麦草生产性能与对照相比差异不显著(P＞0.05),但氮素利用效率在75和150 kg·hm-2两个施氮水平下均优于对照(P＜0.05).分析结果说明,聚谷氨酸硫基复合肥肥效优于尿素和硫基复合肥,且甜高粱和多花黑麦草能够获得较高的产量、品质,且氮素利用效率高.     

垄作免耕对水稻根系特性和氮磷钾养分累积的影响

依托稻田免耕长期定位试验,研究了垄作免耕对Y两优6号水稻根系特性、氮、磷、钾养分累积和产量的变化。研究主要涉及冬水田(中稻-冬水田)、垄作免耕(中稻-油菜)和水旱平作(中稻-油菜)对水稻4个生育时期(分蘖期、拔节期、抽穗期和成熟期)和根系特性,以及水稻根、茎、叶和穗的氮、磷、钾浓度及累积量的影响。结果表明,垄作免耕的实际产量达8750.8 kg·hm^-2,显著高于水旱平作与冬水田(P<0.05)。在拔节期,垄作免耕水稻根系的根长密度和根表面积及比根长均显著高于水旱平作(P<0.05)。在抽穗期,垄作免耕根表面积最高达1.74 cm²·cm^-3,分别比冬水田和水旱平作提高了3.37%和6.71%;且垄作免耕水稻茎秆氮、磷、钾累积量分别较水旱平作提高了49.26%、33.20%和59.70%。相较于常规平作,垄作免耕水稻抽穗期茎叶的磷含量没有显著差异,而茎叶中氮、磷、钾累积量显著增加(P<0.05);氮、磷、钾养分累积速率显著提高(P<0.05),说明在养分累积的关键时期,垄作免耕能显著提高氮、磷、钾的吸收、分配和累积。在成熟期,垄作免耕水稻籽粒中氮累积量比冬水田和水旱平作显著提高了24.80%和14.30%。在分蘖-抽穗期,垄作免耕水稻的 N:K最低、K:P最高,表明垄作免耕能显著提高水稻生长前中期对钾的吸收利用和分配。综上,垄作免耕不仅可以增加水稻的根长密度和根表面积,在抽穗期显著提高水稻对氮、磷、钾的累积,整个生育期对钾的吸收利用明显优于水旱平作和冬水田,为水稻高产提供可参考的依据。     

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.     

Prediction of nutritive values in grass silages: II. Degradability of nitrogen and dry matter using digestibility, chemical composition, and fermentation data

One hundred thirty-six perennial rye-grass silages with wide variations in quality were evaluated for N and DM degradability in three beef steers offered grass silage of medium quality ad libitum. The silages were incubated in the rumen of each animal in triplicate for 0, 6, 12, 24, 48, and 72 h, respectively. The disappearance rates of N or DM were used to calculate the readily soluble fraction ("a" value), potentially degradable fraction ("b" value), and the fractional degradation rate of"b" ("c" value). The effective degradability (P) of N or DM was then estimated assuming a ruminal outflow rate of 0.02, 0.05, or 0.08/h (P0.02, P0.05, or P0.08). The objective was to use these data to develop prediction equations for N and DM degradability in grass silages. There were considerable variations in "a," "b," and "c" values and the P0.02, P0.05, or P0.08 of N and DM (e.g., the P0.02 of N ranged from 75.0 to 93.4% and the P0.02 of DM from 51.5 to 82.5%). The P0.02, P0.05, or P0.08 of N and DM were negatively related (P < 0.001) to ADF, NDF, and lignin concentrations but positively related (P < 0.001) to protein fractions (CP, soluble CP, and true protein concentrations) and digestibility of DM, OM, GE, CP, and NDF and digestible OM in the total DM (measured with sheep). The N and DM degradability data were also positively related to silage lactic acid concentration, but the relationships between DM degradability data and pH, ammonia N/total N, and VFA concentration in silages were negative (P < 0.05). Several sets of prediction equations (linear and multiple) were thus developed for N and DM degradability using CP or NDF concentration, "a" value or digestibility data as primary predictors, together with or without other nutrient concentration and silage fermentation variables. All these relationships were highly significant (P < 0.001), and each predictor had a significant effect on the relationship (P < 0.05). The R2 values in multiple regression for N and DM degradability were generally over 0.70 and higher than in linear regression equations. Four equations were also developed to convert N and DM degradability at a given ruminal outflow rate, predicted using the above-mentioned equations, to their counterparts at any ruminal outflow rate (0.02 to 0.10/h), respectively.