Relationship between corn vitreousness and ruminal in situ starch degradability

The objective of this experiment was to determine the relationship between corn kernel vitreousness and ruminal in situ starch degradation. Fourteen U.S. and five Brazilian corn hybrids cultivated in their respective countries were evaluated. The U.S. dent hybrids were harvested at one-half milk line, black layer, and 21 d after black layer stages of maturity. Brazilian flint hybrids were harvested only at the latest stage of maturity. Vitreousness was determined by manual dissection of the kernels. Ruminal in situ degradation of starch was determined in three lactating Holstein cows fitted with ruminal cannulae. Vitreousness of the five mature Brazilian hybrids averaged 73.1% (range of 64.2% to 80.0%), while vitreousness of the 14 mature U.S. hybrids averaged 48.2% (range of 34.9% to 62.3%). Within the 14 U.S. hybrids, average vitreousness increased from 42.8% to 48.2% as stage of maturity progressed from one-half milk line to 21 d after black layer. The correlation between kernel density and vitreousness was 0.87. The correlations between kernel vitreousness or density and ruminal starch availability were -0.93 and -0.87, respectively. With advancing maturity, kernel vitreousness and density increased while ruminal starch availability decreased. Kernel vitreousness and density may be useful parameters for which to select corn hybrids for high ruminal starch availability. Density may be a more practical measurement than vitreousness for screening large corn data sets.     

Ruminal degradability and intestinal digestibility of protein and amino acids in soybean and corn distillers grains products

New fractionation and fermentation technologies in the ethanol industry have resulted in the production of different forms of distillers grains (DG). Such products are reduced-fat, high-protein, and “modified” wet feeds. Characterization of protein fractions of these co-products and other commonly used feedstuffs is important for the formulation of dairy cattle diets. In situ and in vitro techniques were conducted to compare crude protein (CP) availability in 4 DG products with commonly used soybean proteins. Soybean protein products included solvent-extracted soybean meal (SBM; 44% CP), expeller soybean meal (ESBM), and extruded soybeans (ES). The DG products were conventional distillers dried grains with solubles, reduced-fat distillers dried grains with solubles (RFDGS), high-protein distillers dried grains, and modified wet distillers grains with solubles (MWDGS). Nylon bags containing 5 g of each feed were incubated in the rumen of 3 cannulated lactating cows for 2, 4, 8, 16, 24, and 48 h. The rapidly degradable CP fraction varied from 8.1 to 37.2% for SBM and MWDGS, respectively. The slowly degradable CP fraction was greatest for SBM, ES, and high-protein distillers dried grains (88.0% ± 3.7), followed by ESBM, distillers dried grains with solubles, and RFDGS (76.8 ± 4.1%). The MWDGS had the lowest slowly degradable CP fraction (61.1%). The rate of degradation of the slowly degradable CP fraction ranged from 11.8 for SBM to 2.7%/h for RFDGS. Rumen-undegradable protein varied widely (32.3 to 60.4%), with RFDGS having the greatest and SBM the lowest concentrations. Intestinal digestibility of rumen-undegradable protein (IDP) was estimated by pepsin-pancreatin digestion of ruminally preincubated (16 h) samples. The IDP was greatest for SBM, ESBM, and ES (97.7% ± 0.75), whereas IDP of DG products was 92.4% ± 0.87. Similarly, total digestible protein was greatest (99.0%) for soybean products, whereas DG products had a total digestible protein of 96.0%. Intestinal digestibility of most AA in DG products exceeded 92% and was slightly lower than for soybean products, except for Lys, where the digestibility was 84.6% for DG compared with 97.3% for soybean products. Absorbable Lys was lower for DG (7.0 g/kg of CP) compared with ESBM and ES (average of 23.8 g/kg of CP). Dried DG, ESBM, and ES provided more absorbable AA compared with SBM and MWDGS. These results suggest that the AA availability from DG products is comparable with that from soybean products.     

Nutrient contents,rumen protein degradability and antinutritional factors in some colour- and white-flowering cultivars of Vicia faba beans

Six colour-flowering (Scirocco, Alfred, Carola, Condor, Tina and Herz Freya) and six white-flowering (Caspar, Albatros, Gloria, Tyrol, Vasco and Cresta) cultivars of Vicia faba were studied. The crude protein contents of colour- and white-flowering cultivars were 267±13·6 and 283±18·8 g kg⁻¹, respectively, which did not differ significantly at P<0·05. The levels of lipids, crude fibre, starch and ash varied from 14 to 22 g kg⁻¹, 88 to 143 g kg⁻¹, 407 to 485 g kg⁻¹ and 32 to 42 g kg⁻¹, respectively. The calculated organic matter digestibility (OMD) and metabolisable energy (ME) of the white-flowering cultivars were significantly higher (P<0·001) than those of the colour-flowering cultivars (OMD: 889·1±26·6 g kg⁻¹ vs 797·5±17·1 g kg⁻¹; ME: 13·97±0·49 vs 12·30±0·34 MJ kg⁻¹). In all cultivars, sulphur amino acids were lower than adequate concentration when compared with recommended amino acid pattern of FAO/WHO/UNO reference protein for a 2–5-year-old child. The in vitro rumen nitrogen degradability of colour-flowering cultivars was significantly lower (P<0·01) compared to that of white-flowering cultivars (71·4±9·3% vs 88·0±11·1%). Amongst colour-flowering varieties, the contents of total phenols (TP), tannins (T) and condensed tannins (CT) were highest in Alfred (28·3, 21·0 and 35·4 g kg⁻¹, respectively). The contents of TP and T were similar (about 15 and 10 g kg⁻¹, respectively) in Carola, Tina and Herz Freya, and the CT were in the order: Condor>Herz Freya>Carola. The CT were not detected in white-flowering varieties, T were virtually absent and TP were extremely low (4·0–4·9 g kg⁻¹). The activities of other antinutritional factors (white- and colour-flowering cultivars, respectively: trypsin inhibitor activity 3·05±0·34 and 1·85±0·09 mg trypsin inhibited g⁻¹; lectin 27·2±9·4 and 27·1±5·1 mg ml⁻¹ assay medium producing haemagglutination; phytate 15·0±2·7 and 16·6±2·3 g kg⁻¹) were very low. A strong negative correlation (r=-0·92, P<0·001) between tannins and in vitro rumen protein degradability was observed which suggested that tannins have adverse effect on protein degradability. Similarly negative correlations between tannin levels and metabolisable energy (r=-0·89; P<0·001) and organic matter digestibility (r=-0·89; P<0·001) were observed. The correlation coefficient between trypsin inhibitor activity and tannins was negative and highly significant (r=-0·88, P<0·001), whereas between tannins and saponins it was significantly positive (r=0·96, P<0·001). ©1997 SCI     

Effect of inoculated corn silage enriched with sunflower oil on rumen fermentation and lipid metabolism in an artificial rumen (RUSITEC)

BACKGROUND: Some rumen isolates are able to produce conjugated linoleic acid (CLA) from linoleic acid (LA) in vitro. Effects of providing diets containing corn silage (CS) and lucerne hay to an artificial rumen (RUSITEC) in which the corn was not inoculated (CS), or inoculated with Lactobacillus plantarum CCM 4000 (CS + LP), Lactobacillus fermentum LF2 (CS + LF) or Enterococcus faecium CCM 4231 (CS + EF) and supplied with sunflower oil (SO; 30 g kg^?1; w/w) on rumen metabolism were examined. RESULTS: The SO affected the outputs of all fatty acids. TVA output of uninoculated CS with SO was lower as compared to inoculated CS. The interaction of the CS × SO in the daily output of TVA was detected (P < 0.001). The biohydrogenation of oleic, linoleic, α‐linolenic and total fatty acids was influenced by SO (P < 0.05 and P < 0.001). CONCLUSION: Inoculated silage induces changes in the rumen metabolism which might be related to differences observed in the extent of rumen BH of PUFA in RUSITEC. SO supplementation might positively enhances the production of some rumen intermediates; however, relationships between inoculated silages and oil supplementation can be presumed in the daily production of trans‐vaccenic acid. Copyright © 2009 Society of Chemical Industry     

Milk from forage as affected by rumen degradable protein and corn grinding when feeding corn- and alfalfa silage-based diets

To increase the production of milk from forage (MF), a previous experiment with alfalfa silage showed the importance of a complementary combination of concentrates and forages offered. When corn silage is fed with alfalfa, increasing the rumen degradable protein (RDP) content in the diet should allow a better utilization of forage energy. To evaluate this hypothesis, 8 multiparous Holstein cows in early lactation were used in a replicated 4 × 4 Latin square design with 3-wk periods. Diets were fed as total mixed rations and were formulated to provide similar levels of net energy for lactation and crude protein but differing in RDP. Corn and alfalfa silages were used. Treatments were: 1) cracked corn-based concentrate providing low RDP [level recommended by the NRC (2001); RDP = 11.1% of dry matter (DM)]; 2) cracked corn-based concentrate providing medium RDP (RDP = 12.8% of DM); 3) cracked corn-based concentrate providing high RDP (RDP = 14.5% of DM); and 4) ground corn-based concentrate providing high RDP (RDP = 13.6% of DM). The first 3 treatments, using cracked corn, were compared on the basis of their RDP level. For these treatments, MF, calculated on a protein basis, decreased and the average of MF calculated on an energy basis and MF calculated on a protein basis tended to decrease as RDP increased. There was no difference for MF calculated on an energy basis between treatments. Increasing dietary RDP levels decreased the milk yield (from 32.8 to 30.7 kg/d) and milk protein yield (from 1,094 to 1,005 g/d) but not the milk fat yield. The milk urea N concentration increased as RDP increased. This suggests that there is no advantage of feeding RDP above the NRC recommendations when diets are based on corn and alfalfa silage. At high RDP levels (treatments 3 and 4), ground corn supported higher DM intake and yields of milk and protein than did cracked corn. Milk from forage, calculated on a protein basis, was higher and milk urea N decreased with ground corn. Even with corn silage in the diet, grinding corn grain proved to be beneficial to milk yield and MF production.     

玉米苞叶及其纤维的基本结构与性能

为更好地开发利用玉米苞叶资源,采用数字式织物厚度仪、电子织物强力仪、傅里叶变换红外光谱仪、扫描电子显微镜、Ｘ 射线衍射仪对其进行基本测试。通过测试与分析发现：玉米苞叶厚度及横纵向抗拉强度随苞叶层数由外至内逐渐降低;玉米苞叶主要含有纤维素,半纤维素和木质素;经化学处理后的纤维,其纤维素含量达到４３.７９％,半纤维素和木质素含量有所降低;玉米苞叶表面凹凸不平,有随机分布的孔洞,单纤维横截面形状不规则且内部有大中腔,纵向表面较为光滑平整;玉米苞叶结晶度约为３８.９０％,纤维结晶度为５７.８５％,二者均表现为纤维素Ⅰ的晶体结构。     

Ruminal degradability of dry matter,crude protein,and amino acids in soybean meal,canola meal,corn, and wheat dried distillers grains

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48 h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16 h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074 h⁻¹. The WDDGS and SBM had higher uncorrected ED (DM = 75.0 and 72.6%; CP = 84.8 and 66.0%, respectively) than CM and HPDDG (DM = 57.2 and 55.5%; CP = 59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16 h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.     

Degradation of starch in feed concentrates by enzymes,rumen fluid and rumen enzymes

The degradation of starch from various feedstuffs was investigated with rumen fluid, α-amylase, pancreatin and a freeze-dried, cell-free preparation of rumen fluid. Rumen fluid was taken from either a hay-fed cow or a concentrate-fed cow. It was shown that incubations with rumen fluid at a constant pH of 6·5 gave a higher degradation of starch than those with a decreasing pH. The degree of starch degradation varied widely for the 21 feedstuffs investigated. Sorghum, maize and millet degraded slowly whereas tapioca showed fast degradation. Processed feedstuffs showed a higher level of degradation than unprocessed ones. The use of enzymes did not allow an accurate prediction of starch degradation by rumen fluid. However, this was made possible by the use of a freeze-dried, cell-free preparation of rumen fluid. Scanning electron microscopic observations showed that for the degradation of starch granules additional enzymes, present in rumen fluid, are necessary.     

铁蛋白转基因水稻与亲本的稻米营养成分的比较研究

对3份转Fer基因水稻与亲本的稻米营养成分进行了比较与分析,发现其中2份转Fer基因水稻(F2-5和F10-4)铁含量为野生型亲本秀水11的2.21和2.18倍,由此表明,铁蛋白基因表达与稻米铁含量变化有一定相关性。进一步鉴定表明,转基因稻米其它矿质元素以及粗蛋白、粗脂肪、淀粉、粗纤维、总灰分、氨基酸、维生素等关键性营养成分与亲本差异不显著,转基因未改变原亲本的其他品质性状。并就转Fer基因稻米的食品安全性以及转入的外源基因等问题进行了讨论。     

Determination of rumen degradability and ruminal effects of three sources of methionine in lactating cows

Objectives were to quantify the ruminal effects and flows to the omasum of Met provided as 2-hydroxy-4-(methylthio)-butanoic acid (HMB), the isopropyl ester of HMB (HMBi), and DL-Met. Eight ruminally cannulated cows were used in a replicated 4 x 4 Latin square design. Treatments were 1) no Met (control), 2) HMB at 0.10% of DM, 3) HMBi at 0.13% of DM, and 4) DL-Met at 0.088% of DM. Diets were identical except for type of Met supplement and were based on corn silage and alfalfa hay at 30 and 13% of dietary DM, respectively. Samples of omasal fluid were used to determine the proportion of Met supplements passing out of the reticulorumen. Dry matter intake (20.1 kg/d) was restricted during the week of sampling to a maximum of 95% of ad libitum DMI determined during the first 2 wk of the period. Milk yields (37.7 +/- 0.8 kg/d) and fat concentration (3.42 +/- 0.15%) were not significantly different for control, HMB, HMBi, and DL-Met. Milk protein concentration (2.91, 2.95, 3.02, 2.96 +/- 0.07%, respectively) was significantly increased by the HMBi treatment. Rumen volatile fatty acids profile and NH3 concentrations were similar across treatments. Apparent ruminal digestibility of organic matter and neutral detergent fiber were higher for the three diets supplemented with Met sources than for the control diet. In situ rate of digestibility of CP from alfalfa hay, TMR, and corn silage was affected by Met sources. Passage rates of small particles (0.071/h) and fluid (0.167/h) were not affected by treatments. Protozoal counts in the rumen and omasum were not significantly affected by Met sources. Proportion of omasal N from bacterial N was not different (0.54 +/- 0.03), and bacterial N flow (305 +/- 24.4 g/d) was similar across treatments. The proportion of HMB that passed into the omasum was 5.3 +/- 1.5% of the amount consumed. Only a small amount (2.3%) of HMBi was found as HMB in the omasum. These results indicate that little HMB escapes ruminal degradation through passage to the omasum and that the site of HMBi absorption must be preomasal.     

Estimation of feed crude protein concentration and rumen degradability by Fourier-transform infrared spectroscopy

Currently, rapid methods are needed for feed analysis. This study examined the potential of Fourier-transform infrared (FTIR) spectroscopy to predict the nutritional value of a wide range of feeds for ruminants, as an alternative to the in situ technique. Moreover, we investigated whether universal equations could be developed that would allow the low-cost determination of crude protein (CP) concentrations and their kinetics of degradation into the rumen. Protein nutritional values of 663 samples comprising 80 different feed types were determined in terms of concentrations of CP, water-soluble CP (CP_WS), total-tract mobile bag CP digestibility (CP_TTD), and in situ CP degradability, including the rumen soluble fraction (CP_A), the degradable but not soluble fraction (CP_B), rate of CP_B degradation (CP_C), effective degradability (CP_ED), and potential degradability (CP_PD). Infrared spectra of dry samples were collected by attenuated total reflectance from 4000 to 600 cm⁻¹. Models were developed by partial least squares (PLS) regression in a randomly selected subset of samples, and the precision of the equations was confirmed by using an external validation set. Analysis by FTIR spectroscopy was sufficiently sensitive to allow the accurate prediction of sample CP concentration (R² = 0.92) and to classify feeds according to their CP_WS concentrations using universal models (R² = 0.78) that included all sample types. Moreover, substantial improvements in predictions were observed when samples were subdivided in groups. Models for forages led to accurate predictions of CP_WS and fractions CP_A and CP_B (R² > 0.83), whereas models for CP_TTD and CP_ED could be used for screening purposes (R² > 0.67). This study showed that models for protein-rich concentrates alone could also be used for screening according to the feed concentrations of CP_WS, CP_TTD, CP_ED, CP_A, and CP_B, but models for energy-rich concentrates gave relatively poor predictions. The general difficulty observed in predicting CP_C is because of a low correlation between FTIR spectra and the kinetics of CP degradation, which may be the result of large variation in the reference method (i.e., in situ degradation studies) and perhaps also because of the presence of compounds that can modify the CP degradation pattern in the rumen. In conclusion, FTIR spectroscopy should be considered as a low-cost alternative in the feed evaluation industry.     

Shifts in bacterial community composition in the rumen of lactating dairy cows under milk fat-depressing conditions

Eighteen ruminally cannulated dairy cattle were fed a series of diets (in 28-d periods) designed to elicit different degrees of milk fat depression (MFD) for the purpose of relating MFD to ruminal bacterial populations. Cows were fed a TMR containing 25% starch (DM basis) supplied as corn silage, a slowly fermented starch (SFS treatment, period 1), then switched to a TMR containing 27% starch, much of it supplied as ground high-moisture corn, a rapidly fermented starch (RFS treatment, period 2). In period 3, the RFS diet was amended with 13.6 mg of monensin/kg of DM (RFS/Mon treatment), and in period 4, the cows were returned to the RFS diet without monensin (RFS/Post treatment). Effect of both starch source and monensin on milk fat percentage varied by cow, and cluster analysis identified 4 pairs of cows having distinct milk fat patterns. Archived ruminal liquors and solids from the 4 pairs were processed to isolate bacterial DNA, which was subjected to automated ribosomal intergenic spacer analysis followed by correspondence analysis to visualize bacterial community composition (BCC). One pair of cows (S-responsive) showed MFD on RFS feeding, but displayed no additional MFD upon monensin feeding and a fat rebound upon monensin withdrawal. The second pair of cows (M-responsive) showed no MFD upon switch from the SFS diet to the RFS diet, but displayed strong MFD upon monensin feeding and no recovery after monensin withdrawal. Both groups displayed major shifts in BCC upon dietary shifts, including dietary shifts that both did and did not change milk fat production. The third pair of cows (SM-responsive) displayed reduction of milk fat on both RFS and RFS/Mon diets, and fat returned to the levels on the RFS diet upon monensin withdrawal; these cows showed a more gradual shift in BCC in response to both starch source and monensin. The fourth pair of cows (nonresponsive) did not display changes in milk fat percentage with dietary treatment and showed only minor shifts in BCC with dietary treatment. Regardless of milk fat response, BCC did not reassemble its original state upon monensin withdrawal, though the difference was strongest in M-responsive cows. One amplicon length (representing a single bacterial species) was elevated in most, but not all, MFD-susceptible (S-, M-, or SM-responsive) cows relative to milk fat-nonresponsive cows, whereas 2 amplicon lengths displayed reduced abundance under MFD conditions. Overall, this study demonstrates an association between MFD and wholesale shifts of microbial communities in the rumen.     

Effects of including NaOH-treated corn straw as a substitute for wheat hay in the ration of lactating cows on performance,digestibility, and rumen microbial profile

This study measured the effects of including 5% NaOH-treated corn straw (T-CS) as a substitute for 15% wheat hay in the control total mixed ration (TMR) of lactating cows on performance, digestibility, and rumen microbial profile. Two groups of 21 cows each, similar in initial performance, were fed individually 1 of the 2 TMR examined. Voluntary dry matter intake of cows fed the control TMR was 4.3% higher than that of the T-CS cows, but in vivo dry matter and organic matter digestibilities of both groups were similar. Crude protein digestibility was higher in the control cows but digestibility of neutral detergent fiber polysaccharides (cellulose and hemicelluloses) was higher in the T-CS TMR. This was followed by 4.6% reduction in rumination time of the T-CS group. A slightly higher milk yield was observed in the control cows compared with the T-CS group; however, milk fat and milk protein content were higher in cows fed the T-CS TMR. This was reflected in 1.3% increase in energy-corrected milk yield and 5.34% increase in production efficiency (energy-corrected milk yield/intake) of the T-CS cows compared with the control. Welfare of the cows, as assessed by length of daily recumbence time, was improved by feeding the T-CS TMR relative to the control group. As a whole, the rumen bacterial community was significantly modulated in the T-CS group in the experimental period compared with the preexperimental period, whereas the bacterial community of the control group remained unchanged during this period. Out of the 8 bacterial species that were quantified using real-time PCR, a notable decrease in cellulolytic bacteria was observed in the T-CS group, as well as an increase in lactic acid-utilizing bacteria. These results illustrate the effect of T-CS on the composition of rumen microbiota, which may play a role in improving the performance of the lactating cow.     

黑玉米穗轴色素的分离及组成初探

采用纸层析、紫外可见光谱、红外光谱等技术对黑玉米穗轴色素进行分析研究,纸层析分离出三种主要成分,经纸层析、紫外可见光谱、红外光谱法初步确定分别是矢车菊-3-葡萄糖苷、芍药定-3-葡萄糖苷和天竺葵-3-葡萄糖苷。该黑玉米穗轴色素为花色苷类色素。     

Degradation of condensed tannins by rumen microbes exposed to quebracho tannins (QT) in rumen simulation technique (RUSITEC) and effects of QT on fermentative processes in the RUSITEC

In an earlier study it was observed that the rumen microbes from cattle which had never consumed tannin-containing diets do not have enzymes for degrading condensed tannins. In this study, rumen microbes were exposed to small amounts of quebracho tannins for 8 days using a rumen simulation technique (RUSITEC). The levels maintained in the RUSITEC were 0.1, 0.2 and 0.4 mg of the spray-dried quebracho powder (SDQT) per ml of the medium. After 8 days of tannin exposure, the liquor containing ‘exposed/adapted’ microbes from RUSITEC was incubated for 40 h without and with purified tannins of quebracho and Dichostachys cinerea leaves in in vitro gas method. There was no degradation of condensed tannins. The enzymes for degradation of condensed tannins were not induced in rumen microbes by exposure to different concentrations of tannins for 8 days in the RUSITEC. In the RUSITEC, SDQT significantly reduced the number of total protozoa, entodiniomorphs and holotrichs; effect was higher on holotrichs. There was no significant change in the levels of short chain fatty acid but the molar proportion of propionate was significantly higher and of butyrate significantly lower at 0.4 mg SDQT ml^?1. Significantly lower levels of ammonia in the medium was also observed on injection of tannins. Microbial mass production, calculated using ¹⁵N incorporation, was similar at 0.1 and 0.2 mg SDQT ml^?1 but significantly lower (13%) at 0.4 mg SDQT ml^?1. The dry matter digestibility of the feed (80% hay and 20% barley) was not significantly affected by SDQT.     

体外产气法评定青贮玉米秸与豆秸组合的瘤胃发酵特性

探讨青贮玉米秸与豆秸组合对瘤胃发酵参数的影响,以确定适宜的饲料组合比例。本试验将青贮玉米秸与豆秸分别按0∶100、20∶80、40∶60、60∶40、80∶20、100∶0的比例进行组合,利用体外瘤胃发酵技术,分析不同比例组合对产气量、pH值、氨态氮、菌体蛋白和瘤胃干物质、中性洗涤纤维和酸性洗涤纤维的影响,并计算出各组合的单项组合效应值和综合组合效应值,进而筛选出两种饲料组合的适宜比例。结果表明：青贮玉米秸-豆秸不同比例组合后在产气量上差异显著（P〈0.05）,以80∶20时最大;各比例对体外瘤胃液pH值影响差异不显著（P〉0.05）;氨态氮质量浓度随青贮玉米秸比例的增加而增加,在40~50mg/dl变化;菌体蛋白质量浓度在两者比例为80∶20时最高;青贮玉米秸-豆秸不同比例组合的干物质、中性洗涤纤维和酸性洗涤纤维的瘤胃有效降解率均以80∶20时最大。在本试验条件下,以多项组合效应评定指数评定组合效应,青贮玉米秸与豆秸比例为80∶20时较为适宜,综合组合效应指数达到最大。     

Effects of cultivars on ensiling characteristics,chemical composition,and ruminal degradability of pea silage

A study was conducted to determine the effects of cultivar on ensiling characteristics, chemical composition and ruminal nutrient degradability of pea (Pisum sativum L.) silage. The cultivars evaluated were Lenca (L), Carneval (C), and Delta (D). Peas were field-grown and forage was harvested and ensiled in mini-silos for 0, 2, 4, 8, 16, and 70 d. The ensiled forage of all cultivars went through a rapid fermentation with a sharp reduction in pH during the first 2 days of ensiling. Extensive proteolysis took place between 0 and 2 d as indicated by a reduction in true protein and neutral detergent insoluble protein (NDICP) and an increase in nonprotein nitrogen. Chemical analysis of the 70 d silage showed that cultivar L contained higher neutral detergent fiber (NDF) and acid detergent fiber and lower starch levels than C and D. Crude protein was highest for C (20.5% DM), intermediate for D (19.0% DM) and lowest for L (17.9% DM). Distribution of protein fractions showed that L contains lower soluble protein and higher NDICP levels than the other two pea cultivars. However, no difference in acid detergent insoluble protein levels was observed between the three cultivars. Results of the in situ incubation experiment indicated that L had lower ruminal DM (69.2 vs 74.0%) and CP (84.1 vs 90.6%) degradabilities than C or D. However, ruminal degradability of NDF was similar among the three cultivars (average of 32.9%). It was concluded that chemical composition and ruminal nutrient degradability of pea silage are significantly influenced by cultivars.     

Effects of the percentage of concentrate on rumen fermentation, nutrient digestibility, plasma metabolites, and milk composition in mid-lactation goats

The aim of this work was to study the effects of the dietary percentage of concentrate on patterns of intake, the evolution of rumen fermentation characteristics and plasma metabolites after a meal, nutrient digestibility, and milk production and composition in a medium-term trial in dairy goats. These effects have been well studied in dairy cattle but seldom in goats. Thirteen ruminally and duodenally cannulated dairy goats (95 ± 4 d in milk) fed ad libitum were used in this study. Goats were assigned to 1 of 2 dietary treatments: high-concentrate (70% concentrate on dry matter basis) or a low-concentrate (35%) total mixed rations. The experiment was conducted over a period of 10 wk, including 3 wk of adaption to the diets. Patterns of intake, rumen fermentation characteristics, and plasma metabolites after a meal and fatty acids profile of milk fat were compared at the onset and at the end of the experiment. The increase in dietary percentage of concentrate decreased rumen pH, acetate to propionate ratio, ammonia-N concentration, and plasma urea concentration. The percentage of concentrate did not affect total volatile fatty acid concentrations. The high-concentrate diet increased the rate of intake during the morning meal at the onset of the experiment, whereas it decreased total dry matter intake and the rate of intake during the morning meal at the end of the experiment. The high-concentrate diet resulted in greater organic matter digestibility. Raw milk yield and protein yield were greater in goats fed the high-concentrate diet, whereas fat yield was not affected by dietary treatments. The milk fat content was lower in goats fed the high-concentrate diet. Proportions of the trans-C18:1 isomer relative to total fatty acids in milk were higher with the high-concentrate diet, but no modification of the proportion of total trans-C18:1 was detected, in particular no shift from trans-11 C18:1 to trans-10 C18:1 was observed. Further, the isomer trans-10,cis-12 C18:2 was not detected. Data from this study could be used for a new modeling approach or to improve existing models.     

响应面试验优化碱提酸沉法提取微胚乳玉米蛋白工艺及其组成分析

对碱提酸沉法提取微胚乳玉米蛋白的工艺条件进行优化,并分析其分子质量分布和氨基酸组成。以微胚乳玉米为原料,采用碱提酸沉法提取其中的蛋白质,以玉米蛋白得率为指标,采用单因素试验考察了料液比、提取pH、提取温度和提取时间的影响,采用响应面试验进一步对微胚乳玉米蛋白提取的工艺条件进行了优化。采用SDS-PAGE和氨基酸组成分析比较了最优条件下提取的微胚乳玉米蛋白与普通玉米蛋白的差异。结果表明：微胚乳玉米蛋白的最优提取工艺条件为料液比1∶15、提取pH 11.5、提取温度50℃、提取时间60 min,在此条件下微胚乳玉米蛋白得率为20.40%;微胚乳玉米蛋白与普通玉米蛋白的分子质量均小于60 kDa,但在15～20 kDa之间二者出现的条带略有不同,两种蛋白中氨基酸种类齐全,谷氨酸、亮氨酸、精氨酸、天门冬氨酸含量较高,微胚乳玉米蛋白的必需氨基酸含量占氨基酸总量的36.15%,略高于普通玉米蛋白的35.44%。该研究可为微胚乳玉米蛋白精深加工及其应用提供一定科学依据。