Feed efficiency of mid-lactation dairy cows fed yeast culture during summer

Thirty-eight Holstein cows (26 multiparous and 12 primiparous), that averaged 105 d postpartum at the start of the experiment, were used to evaluate the feeding of yeast culture (60 g/cow daily of Diamond V XP) on production efficiency during hot summer weather. From early June until early September and after a 2-wk covariate period, cows were fed a control diet without or with 60 g of yeast culture/cow daily for 12 wk. Weekly daytime high temperatures in the free-stall barn during the 12-wk period averaged 33 degrees C (28 to 39 degrees C). Total mixed diets on a dry matter (DM) basis consisted of corn silage (28%), alfalfa hay (21%), and a concentrate mix (51%) without or with the yeast culture added to the total mixed ration at the time of feeding. Milk production (34.9 and 35.4 kg/d, for control and yeast culture treatment, respectively), 4% fat-corrected milk (31.2 and 32.0 kg/d), energy-corrected milk (ECM; 33.4 and 34.2 kg/d), and DM intake (23.1 and 22.1 kg/d) were similar for cows fed control and yeast culture diets. Percentages of milk fat (3.34 and 3.41) and true protein (2.85 and 2.87) were similar for both diets. Feed efficiency defined as kilogram of ECM/kilogram of DM intake was improved by 7% for cows fed the yeast culture. Body weights and body condition scores were similar for both groups. The results suggest that the yeast culture can improve feed efficiency of heat stressed dairy cows in midlactation.     

Effect of level of metabolizable protein on milk production and nitrogen utilization in lactating dairy cows

The objective of this study was to investigate the effects of the level of metabolizable protein (MP) on milk production and nitrogen utilization in Chinese Holstein dairy cows. Forty multiparous dairy cows (body weight = 590 kg; days in milk = 135; average milk yield = 30.2 kg/d) were assigned to treatments randomly within groups based on days in milk and milk production. Animals were offered diets with different levels of MP: 8.3% (diet A), 8.9% (diet B), 9.7% (diet C), and 10.4% (diet D) of dry matter. The MP level in diet A was designed to meet the current Chinese National Station of Animal Production and Health guidelines, whereas that in diet D was based on the National Research Council (2001) model. The experiment lasted for 7 wk. Milk yield and milk composition (fat, protein, and lactose) were recorded, and urea nitrogen concentrations in serum, urine, and milk were measured during the experiment. Milk yield and milk protein percentage increased as the MP increased up to 9.7% of dry matter, and then leveled off. Concentrations of nitrogen in urine, serum, and milk increased linearly as the amount of MP was increased, indicating decreased efficiency of nitrogen utilization. Milk lactose percentage and total solids percentage showed no significant differences among the 4 diets. We concluded that the optimal dietary MP level was at 9.6% of dry matter for Chinese Holstein dairy cows producing 30 kg of milk per day.     

Effect of a direct-fed fibrolytic enzyme formulation on nutrient intake,partitioning, and excretion in early and late lactation Holstein cows

The effect of a fibrolytic enzyme formulation on N and P intake, partitioning, and excretion was evaluated in dairy cows in early and late lactation. Twelve lactating Holstein cows (6 early lactation, 6 late lactation) were fed diets with or without the enzyme formulation in a switchback design with three, 4-wk periods. Diets for the early lactation group contained 45% forage, and late lactation diets contained 61% forage. Cows fed diets containing the enzyme formulation gained more weight than those on the control diet; this weight gain with enzyme addition was greater in early lactation cows than in late lactation cows. The main effect of enzyme treatment did not significantly affect apparent digestibility or excretion of N and P, or retention of these nutrients in body tissue. Interactions observed between the effects of group (stage of lactation) and treatment indicated differences in the nature of the milk yield and manure excretion responses to enzyme treatment between early and late lactation cows. These interactions were due to numerical increases in milk yield, feces excretion, and N excretion in early lactation cows fed diets containing the enzyme formulation compared to control, and slight decreases in these measures in late lactation cows with enzyme addition. Cows fed diets containing a direct-fed fibrolytic enzyme formulation had increased body weight gain, but the effect of addition of the enzyme formulation on milk yield and manure nutrient excretion differed for early and late lactation cows.     

Exogenous β-mannanase improves feed conversion efficiency and reduces somatic cell count in dairy cattle

Exogenous fibrolytic enzymes have been shown to be a promising way to improve feed conversion efficiency (FCE). β-Mannanase is an important enzyme digesting the polysaccharide β-mannan in hemicellulose. Supplementation of diets with β-mannanase to improve FCE has been more extensively studied in nonruminants than in ruminants. The objective of this study was to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and nitrogen utilization in lactating Holstein dairy cows. Twelve post-peak-lactation multiparous Holstein cows producing 45.5 ± 6.6 kg/d of milk at 116 ± 19.0 d in milk were randomly allotted to 1 of 3 treatments in a 3 × 3 Latin square design with 3 periods of 18 d (15 d for adaptation plus 3 d for sample collection). All cows were fed the same basal diet and the 3 treatments differed only by the β-mannanase dose: 0% dry matter (DM; control), 0.1% of DM (low supplement, LS), and 0.2% of DM (high supplement, HS) supplemented to the basal diet. Supplementation of β-mannanase enzyme at the LS dose reduced dry matter intake (DMI) but did not affect milk yield or milk composition. Cows receiving LS produced 90 g more milk per kg of DMI compared with control cows. Somatic cell count (SCC) in milk was lower for cows fed the LS diet compared with cows fed control diets. Cows fed LS diet had lower DM, organic matter and crude protein digestibility compared with cows fed control diets. Starch, neutral detergent fiber, and acid detergent fiber digestibility were not affected by LS. Milk yield, DMI, SCC, and nutrient digestibility did not change for HS. Despite the reduced crude protein digestibility, reduced N intake led to similar fecal N excretions in LS cows and control cows (234 vs. 235 g/cow per day). Urinary N excretions remained similar between enzyme-fed and control cows (~190 g/cow per day), although the percentage of N intake partitioned to urinary N tended to be greater in LS than in control cows (31 vs. 27%). Cows fed LS significantly improved the percentage of apparently absorbed N partitioned to milk protein N (42 vs. 38%). When supplemented at 0.1% of dietary DM, β-mannanase can improve FCE and lower the SCC of dairy cows without affecting milk yield, milk composition, or total manure N excretions of dairy cows.     

In vitro methionine supplementation during lipopolysaccharide stimulation modulates immunometabolic gene network expression in isolated polymorphonuclear cells from lactating Holstein cows

Methionine (Met) is one of the 2 most limiting amino acids for milk production in dairy cow diets. The accepted “ideal” ratio of lysine (Lys) to Met (L:M) when formulating diets is 3:1. However, blood from cows fed corn silage-based diets without supplemental rumen-protected Met averages approximately 3.6:1 L:M. Recent in vivo research on cattle immunonutrition has revealed that the immune system could benefit from greater Met supply. To study more closely the effects of different L:M ratios, blood polymorphonuclear cells (PMN) were isolated from 5 Holstein cows in mid-lactation (238 ± 20 d postpartum, 33.8 ± 3.8 kg of milk/d; mean ± SD). The PMN were incubated at 3 different levels of L:M (3.6:1, 2.9:1, or 2.4:1) and stimulated with lipopolysaccharide (LPS) at either 0 or 50 μg/mL for 2 h at 37°C. Target genes were associated with cytokines, pathogen recognition, nuclear receptors, killing mechanisms, and Met and glutathione metabolism. Data were subjected to ANOVA using PROC MIXED in SAS, with L:M, LPS, and their interaction as fixed effects. Stimulation with LPS upregulated genes related to cytokines (IL1B, TNF, IL10 and IL6) and nuclear receptors, including nuclear factor kappa B (NFKB1) and glucocorticoid receptor (NR3C1), and downregulated the mRNA abundance of chemokine receptor 1 (CXCR1), lysozyme (LYZ) and glutathione reductase (GSR). A linear decrease was observed in the mRNA abundance of TNF when L:M was decreased. A similar response was observed for interleukin-1 receptor-associated kinase 1 (IRAK1) and NFKB1 abundance in cells stimulated with LPS (linear effect). A linear increase of LYZ mRNA expression as L:M decreased was detected in unstimulated cells. Furthermore, a decrease in L:M led to a linear decrease of superoxide dismutase 1 (SOD1) mRNA abundance in cells challenged with LPS. Overall, LPS challenge triggered the activation of isolated PMN from mid-lactation cows. However, data suggest the use of a shorter incubation time to capture the peak response and not the resolution of the inflammatory response as in the present study. Our results indicate a possible involvement of Met in modulating PMN inflammatory and oxidative stress status and in helping the resolution of inflammation after initial stimulation.     

In Sacco法评定玉米的不同加工处理方式对泌乳奶牛瘤胃干物质和淀粉降解规律的影响

以3头安装有永久性瘤胃瘘管的泌乳前期荷斯坦奶牛为试验动物,在精粗比为55：45的日粮条件下,采用In sacco法测定了不同加工处理的玉米在奶牛瘤胃内干物质和淀粉的降解规律.试验结果表明,不同加工处理方法可以程度不同的影响干物质和淀粉在瘤胃中的降解,与未处理玉米相比,挤压膨化和制粒加工处理能明显的提高玉米中淀粉在瘤胃中的降解率（P＜0.05）,压扁处理对干物质降解率无明显影响（P＞0.05）,但使淀粉瘤胃降解率明显提高（P＜0.05）,烘烤与焙炒加工处理能明显的降低玉米中干物质和淀粉在瘤胃中的降解率（P＜0.01）.淀粉瘤胃降解率由高到低顺序依次为膨化玉米＞颗粒玉米＞压扁玉米＞未处理玉米＞焙炒玉米＞140℃/35min烘烤玉米.淀粉在瘤胃中的降解的影响因素最主要是淀粉的快速可溶部分和降解速率.     

Digestibility in lactating cows of diets containing whole Pima treated with sodium hydroxide versus Akala or Pima cottonseed

This study examines the effect of NaOH treatment on the nutritive value of Pima cottonseed for lactating cows. Treatment of Pima cottonseed with NaOH increased the extent of dry matter (DM) and neutral detergent fiber in vitro digestibility. Three groups of cows were fed 3 similar total mixed rations (TMR) differing only in the type of cottonseed fed, either whole linted Akala, whole unlinted Pima, or whole Pima treated with 4% NaOH (T-Pima). Dry matter and organic matter (OM) intakes of Akala and Pima TMR were similar and tended to be lower compared with cows fed T-Pima. This was reflected in similar intake of crude protein and lipids by cows fed the 3 TMR. Digestibility of DM, OM, and crude protein were similar in cows fed Pima and T-Pima diets, and slightly higher in cows fed the Akala TMR. Lipid digestibility was highest in cows fed Akala TMR, whereas cellulose and NDF digestibility were lowest in Pima TMR. In the 3 TMR, there was a large gap between the high values of "digestibility of intact seeds" and actual in vivo digestion of DM and OM. Similar yields of milk and milk protein were obtained in cows fed the Akala and Pima TMR, whereas higher yields of milk, milk protein, milk fat, and 4% fat-corrected milk were found in the T-Pima cows. Similar efficiency of DM intake for fat-corrected milk production was achieved by cows fed the 3 TMR.     

热应激时奶牛血液中游离氨基酸流向与乳蛋白下降的关系研究

目的:探讨热应激时奶牛血液中氨基酸与乳蛋白的相互关系。方法:选取6头相同泌乳期奶牛,正常饲喂和饮水,实验期35 d(6月29日—8月5日)。每日10:00和18:00记录气温,统计产奶量,每周取全天奶样,Foss乳成分分析仪检测乳蛋白含量。于实验开始第1周和最后1周采集颈静脉血液,反相高效液相色谱法检测血液中游离氨基酸含量。结果:随着气温的升高(由26℃升高至最高38℃),实验奶牛日均产奶量由15.2 kg/d下降至10 kg/d,乳蛋白产量由0.47 kg/d下降至0.31 kg/d。血液中Glu、Asp、Gly和Val等主要的生糖氨基酸(参与糖异生作用)以及Leu、Ile等生酮氨基酸均升高或显著升高(0.01P0.05);总支链氨基酸(Val、Ile、Leu,主要参加免疫反应)含量显著增加(P0.05),在必需氨基酸中所占的比例由54.75%增至67.89%。结论:在夏季高温高湿条件下,奶牛可发生热应激,产奶量和乳蛋白含量均降低,但血液中游离氨基酸,特别是支链氨基酸含量显著升高。提示热应激时奶牛血液中高水平的游离氨基酸并未完全用于乳蛋白的合成,还发挥了除此之外的其他作用,而后者的作用优先于参与乳蛋白的合成,即可能优先作为功能性氨基酸参与了机体的其他活动。     

Cefoperazone sodium preparation behavior after intramammary administration in healthy and infected cows

Selection of the antimicrobial agent and maintenance of adequate drug concentrations at the site of infection are the most relevant problems in mastitis antibiotic therapy. Intramammary drug efficacy can be maximized by keeping drug concentrations at the site of infection above the minimum inhibitory concentration (MIC) as long as possible; the most important pharmacokinetic and pharmacodynamic (PK/PD) measure for efficacy evaluation is time during which drug concentrations exceed the MIC (t > MIC). To evaluate this measure, the PK profile of cefoperazone (CFP) after single intramammary administration in healthy and subclinical infected Staphylococcus aureus cows and the MIC of Staph. aureus field strains were assessed. In addition, the degree of drug passage from udder to bloodstream was investigated by measuring systemic drug absorption in healthy and infected animals. Cefoperazone concentrations were quantified by HPLC in quarter milk samples and blood serum samples. Systemic drug absorption was negligible in healthy animals (0.020 ± 0.006 μg/mL serum at 4 h), whereas it was higher in infected animals (0.102 ± 0.079 μg/mL at 4 h and 0.025 μg/mL at 24 h), probably due to the damage of epithelial cell junctions caused by subclinical infections. The MIC₉₀ value for CFP in Staph. aureus field strains (n = 24) was 0.64 μg/mL. The PK/PD evaluation, determined by t > MIC, showed a longer persistence of CFP in infected quarters than in healthy ones (mean residence time was 8.37 ± 1.51 vs. 11.42 ± 5.74 h in September and 2.07 ± 0.43 vs. 3.31 ± 0.91 h in October), with a t > MIC of 45 ± 6 h for infected quarters versus 38 ± 5 h for healthy quarters different only in October. This could mean a prolonged time in which microorganisms are exposed to drug activity and thus, a greater efficacy of the drug.     

ICP—AES测定卷烟烟气中钾、钠金属离子

建立了全谱直读电感耦合等离子发射光谱法(ICP–AES),同时测定了其中卷烟烟气中钾钠离子的含量。研究了元素分析标准曲线、精准度、回收率以及不同种类烟草样品中两种离子的含量差别。结果表明,在选定的波长下测定,元素间也没有干扰.该方法快速,准确可靠,加标回收率为95~98%,相对标准偏差RSD均小于4%,适用于对卷烟主流烟气的检测。     

X射线能谱在卷烟纸钾和钠元素含量快速检测中的应用

快速分析卷烟纸中钾（K）和钠（Na）元素含量对于卷烟纸生产的工艺控制起着重要的作用,本课题探讨了一种采用X射线能谱（EDS）法快速无损检测卷烟纸中K和Na元素实际总含量的方法。利用EDS和传统的原子吸收光谱（AAS）法分别对卷烟纸表面K和Na元素含量（c）和实际总含量（C）进行了定量检测,探寻EDS法和AAS法定量检测结果间的关联。结果表明,这两种方法获得的数据之间具有如下关系:C_K=27.28c_K+0.4805和C_Na=1.7926c_Na+0.5763,其相关系数R²分别为0. 958和0. 959。鉴于EDS具有快速、无损检测的优点,该方法通过快速的EDS表面分析可以实现对卷烟纸中K和Na元素总含量的检测,可有效提高测定卷烟纸中K和Na元素助剂添加量的实验效率。     

Formulation and shelf-life of a bottled pawpaw juice beverage

A simple procedure was developed for production of bottled pawpaw beverage juice by peeling and macerating peeled tissue in 25% water, straining through a 0.8-mm sieve, adjustment of juice pH with citric acid and flavour adjustment with sucrose. Fresh juice was optimized for acceptability at pH 3.9 and 10% (w/w) sucrose. Heating for 6 min at 72.2°C was required to achieve commercial pasteurization. Samples of juice were prepared with no preservative, and containing sodium benzoate (125mg/100ml), sodium metabisulphite (50mg/100ml) and sodium metabisulphite/sodium benzoate combination (25mg and 60mg/100ml) for trials in which acceptability, pH, specific gravity, brix, total acidity, vitamin C and biomass concentrations were measured over 90 weeks storage at 10°C and 30.2°C. Sodium benzoate alone extended the shelf-life at 30°C up to 80 weeks but the other preservatives were not effective after 20 weeks. The control juice was already deteriorating by 10 weeks at 30°C. At 10°C all preserved samples were stable up to 80 weeks, although the control deteriorated rapidly after 20 weeks.     

盐硝联产工艺生产高品质无水硫酸钠研究

通过研究盐硝联产工艺特点,利用母液淘洗,后工序加酸,柱磨机研磨,达到了生产高品质无水硫酸钠的目的。     

萃取法（t—BAMBP）提取卤水中铷、铯及其影响因素分析

研究以t-BAMBP为萃取剂,萃取分离Rb、Cs,同时考察料液中碱金属元素Na、K对铷、铯萃取效果的影响。研究得出：碱金属元素Na对实验体系中铷、铯的萃取没有影响：碱金属元素K对体系中铷的萃取影响较大,随着溶液中K浓度的增大,铷的萃取率逐渐减小;碱金属元素K对铯的萃取率影响较小,可忽略。该研究主要针对江陵凹陷富钾卤水中铷、铯的提取技术进行探索。     

t-BAMBP萃取法提取卤水中铷、铯及影响因素分析

铷、铯在地壳中含量颇丰,近年铷铯在新兴应用领域中显示出强劲的生命力。研究以t-BAMBP为萃取剂用于模拟料液萃取分离铷、铯,同时探索碱金属元素钠、钾对铷、铯萃取结果的影响。研究得出:碱金属元素钠对实验体系中铷、铯的萃取没有影响;碱金属元素钾对体系中铷的萃取影响较大,随着溶液中钾浓度的增大,铷的萃取率逐渐减小;碱金属元素钾对铯的萃取率影响较小,可忽略。     

Na+/K+对大豆种皮多糖-黏蛋白体系界面稳定性的影响

黏蛋白和大豆种皮多糖通过空间和静电相互作用在肠界面形成稳定的能量屏障,调节小分子的吸收和运输。然而,能量屏障受到肠道离子的影响。通过粒径、Zeta电位、界面张力、傅里叶变换红外光谱、内源荧光光谱、微观结构和剪切流变学研究不同浓度Na+/K+对MASP与黏蛋白相互作用的影响。结果表明:相互作用12 h后,MASP/黏蛋白混相体系的绝对电位从54.80 mV降到28.70 mV,粒径随相互作用时间的延长而增大,Na+在一定程度上提高混相体系绝对电位到32.45 mV,使混相体系粒径分布范围减小至370~950 nm。12 h后,MASP/黏蛋白混相体系的初始界面张力由56.52 mN/m提高到58.46 mN/m。Na+/K+在不改变化学键的情况下,降低了混相体系的界面张力。值得注意的是,Na+/K+的加入使MASP/黏蛋白混相体系从致密的块状变为疏松的有间隙的碎片状,延缓了混相体系表观黏度的下降速度,提高了混相体系的储能模量。K+对混相体系表观黏度降低率和储能模量增加率的影响大于Na+。这些发现为了解肠道环境对营养传递系统的影响提供了新的思路。