Comparing responses of dairy cows to short-term and long-term heat stress in climate-controlled chambers

Heat stress (HS) in dairy cows can be classified into short-term heat stress (STHS) and long-term heat stress (LTHS) according to the number of consecutive days in HS. The comparative study of these 2 types of HS is limited in terms of their effects on the production and energy metabolism of cows. In this study, 4 lactating Holstein cows (102.5 ± 12 days in milk, 605 ± 22 kg of body weight, second parity) fitted with rumen fistulae were randomly assigned to 1 of 2 groups in a 2 × 2 crossover design and allocated to 1 of 2 climate-controlled chambers. This study contained 2 periods, each with a control phase and a HS phase. There was a recovery phase between 2 periods. The HS phase comprised either STHS (3 d) or LTHS (7 d) treatments. Data collected from the 3 d of STHS and the last 3 d of LTHS were compared. The chambers were set at thermal neutral conditions (20°C, 50% humidity) during the control and recovery phases or cyclical HS conditions (26–38°C, 50% humidity) during the HS phase. Compared with STHS, LTHS decreased milk yield by 17.2% and dry matter intake by 12.6%, indicating that LTHS caused a more severe decline in milk production and feed intake. In addition, LTHS decreased milk protein concentration by 6.8% and milk protein yield by 22.4%. In comparison with STHS, LTHS decreased rumen liquor volatile fatty acid (29.7%), blood glucose (11.6%), and nonesterified fatty acid (13.6%) concentrations, but increased milk urea nitrogen by 15.1%, blood urea nitrogen by 8.6%, and creatine concentrations by 15.4%. Our results suggest that although reduced feed intake may be mainly responsible for reduced milk production during STHS, impaired rumen metabolism and suppressed mobilization of adipose tissue could be the main reasons for further reduction in milk yield during LTHS.     

Effects of dairy cow genotype with two planes of nutrition on energy partitioning between milk and body tissue

The data used in the present study were derived from a 2 (genotype) × 2 (plane of nutrition) factorial design production study using Holstein-Friesian (n = 32) and Norwegian (n = 32) first-lactation dairy cattle offered grass silage-based diets from 1 to 44 wk of lactation. The high nutrition diet had concentrate inclusions (g/kg of dry matter) of 600, 500, and 400 for lactation days of <101, 101 to 200, and >200, respectively, and the low nutrition diet included concentrates at 300, 200, and 100 for the same periods. Dietary metabolizable energy (ME) concentrations were measured in calorimetric chambers at lactation d 80, 160, and 240 respectively, and then applied to production data to calculate ME intake. From wk 1 to 44 of lactation, Holstein-Friesian cows had a consistently lower accumulated live weight gain and body condition score, and a consistently higher ME intake and milk energy output than Norwegian cows, irrespective of the plane of nutrition. Compared with Norwegian cows using mean data derived from the 2 planes of nutrition, Holstein-Friesian cows produced a significantly higher proportion of milk energy output over ME intake in early and mid lactation, although this increase was not significant in late lactation. In contrast, Holstein-Friesian cows partitioned a significantly lower proportion of ME intake into body tissue than Norwegian cows in early lactation, although the differences were not significant in mid or late lactation. When ME intake and energy used for maintenance, milk, and body tissue were taken into account, the efficiency of ME use for lactation was similar between the 2 genotypes offered the high or low concentrate diet during the whole lactation. It is concluded that Holstein-Friesian cows can produce more milk energy than Norwegian cows, mainly as a result of higher ME intake and because of a greater ability to partition more energy into milk and less into body tissue. The effect on energy partitioning mainly occurs in early and midlactation and is particularly evident with high concentrate diets.     

Differences in net fat oxidation,heat production,and liver mitochondrial DNA copy numbers between high and low feed-efficient dairy cows

Improving feed utilization efficiency in dairy cattle could have positive economic and environmental effects that would support the sustainability of the dairy industry. Identifying key differences in metabolism between high and low feed-efficient animals is vital to enhancing feed conversion efficiency. Therefore, our objectives were (1) to determine whether cows grouped by either high or low feed efficiency have measurable differences in net fat and carbohydrate metabolism that account for differences in heat production (HP), and if so, whether these differences also exists under conditions of feed withdrawal when the effect of feeding on HP is minimized, and (2) to determine whether the abundance of mitochondria in the liver can be related to the high or low feed-efficient groups. Ten dairy cows from a herd of 15 (parity = 2) were retrospectively grouped into either a high (H) or a low (L) feed-efficient group (n = 5 per group) based on weekly energy-corrected milk (ECM) divided by dry mater intake (DMI) from wk 4 through 30 of lactation. Livers were biopsied at wk ?4, 2, and 12, and blood was sampled weekly from wk ?3 to 12 relative to parturition. Blood was subset to be analyzed for the transition period (wk ?3 to 3) and from wk 4 to 12. In wk 5.70 ± 0.82 (mean ± SD) postpartum (PP), cows spent 2 d in respiration chambers (RC), in which CO₂, O₂, and CH₄ gases were measured every 6 min for 24 h. Fatty acid oxidation (FOX), carbohydrate oxidation (COX), metabolic respiratory quotient (RQ), and HP were calculated from gas measurements for 23 h. Cows were fed ad libitum (AD-LIB) on d 1 and had feed withdrawn (RES, restricted diet) on d 2. Additional blood samples were taken at the end of the AD-LIB and RES feeding periods in the RC. During wk 4 to 30 PP, H had greater DMI/kg of metabolic body weight (BW^0.75), ECM per kilogram of BW^0.75 yield, and ECM/DMI ratio, compared with L, but a lower body condition score between wk 4 and 12 PP. In the RC period, we detected no differences in BW, DMI, or milk yield between groups. We also detected no significant group or group by feeding period interactions for plasma metabolites except for Revised Quantitative Insulin Sensitivity Check Index, which tended to have a group by feeding period interaction. The H group had lower HP and HP per kilogram of BW^0.75 compared with L. Additionally, H had lower FOX and FOX per kilogram of BW^0.75 compared with L during the AD-LIB period. Methane, CH₄ per kilogram of BW^0.75, and CH₄ per kilogram of milk yield were lower in H compared with L, but, when adjusted for DMI, CH₄/DMI did not differ between groups, nor did HP/DMI. Relative mitochondrial DNA copy numbers in the liver were lower in the L than in the H group. These results suggest that lower feed efficiency in dairy cows may result from fewer mitochondria per liver cell as well as a greater whole-body HP, which likely partially results from higher net fat oxidation.     

一种高效管壳式换热器的应用

换热器的结构型式不同,其换热效率差别很大。对管壳式换热器结构做出局部改动,可以提高换热效率。     

印染蒸汽凝结水回收与节能

提出了充分回收印染蒸汽供热系统产生的大量凝结水及余汽余热资源的新理念和可行性分析,从理论和实际应用两方面叙述了印染企业实验节能技术改造的基本途径。     

芦苇置换蒸煮中的热能回收及循环利用

通过对芦苇置换蒸煮生产过程的描述,分析了热能的主要来源,重点介绍了在此过程中热能存在的不同形式,并逐一阐明了热能回收方式以及整体过程中热能循环利用的特点。     

Mitigation of enteric methane emissions through improving efficiency of energy utilization and productivity in lactating dairy cows

The data set used in the present study was obtained from 20 energy metabolism studies involving 579 lactating dairy cows (511 Holstein-Friesian, 36 Norwegian Red, and 32 Jersey-Holstein crossbreds) varying in genetic merit, lactation number, stage of lactation, and live weight. These cows were offered diets based on grass silage (n = 550) or fresh grass (n = 29), and their energy intake and outputs, including methane energy (CH₄-E), were measured in indirect open-circuit respiration calorimeter chambers. The objective was to use these data to evaluate relationships between CH₄-E output and a range of factors in animal production and energetic efficiency in lactating dairy cows under normal feeding regimens. The CH₄-E as a proportion of milk energy output (E_l), E_l adjusted to zero energy balance (E_l(0)), or intakes of gross energy (GE), digestible energy (DE), or metabolizable energy (ME) was significantly related to a wide range of variables associated with milk production (E_l and E_l(0)) and energy parameters (energy intake, metabolizability, partitioning, and utilization efficiencies). Three sets of linear relationships were developed with experimental effects removed. The CH₄-E/GE intake (r² = 0.50-0.62) and CH₄-E/E_l (r² = 0.41-0.68) were reduced with increasing feeding level, E_l/metabolic body weight (MBW; kg^0.75), E_l(0)/MBW, GE intake/MBW, DE intake/MBW, and ME intake/MBW. Increasing dietary ME/DE decreased CH₄-E/E_l (r² = 0.46) and CH₄-E/GE intake (r² = 0.72). Dietary ME concentration and ME/GE were also negatively related to CH₄-E/GE intake (r² = 0.47). However, increasing heat production/ME intake increased CH₄-E as a proportion of E_l (r² = 0.41), E_l(0) (r² = 0.67) and energy intake (GE, DE, and ME; r² = 0.62 and 0.70). These proportional CH₄-E variables were reduced with increasing ratios of E_l/ME intake and E_l(0)/ME intake and efficiency of ME use for lactation (r² = 0.49-0.70). Fitting CH₄-E/E_l or CH₄-E/E_l(0) against these energetic efficiencies in quadratic rather than linear relationships significantly increased r² values (0.49-0.67 vs. 0.59-0.87). In conclusion, CH₄-E as a proportion of energy intake (GE, DE, and ME) and milk production (E_l and E_l(0)) can be reduced by increasing milk yield and energetic efficiency of milk production or by reducing energy expenditure for maintenance. The selection of dairy cows with high energy utilization efficiencies and milk productivity offers an effective approach to reducing enteric CH₄ emission rates.     

综合利用余热促进节能减排

文章对我公司Ⅰ、Ⅱ效冷凝回水综合利用情况进行了总结,借助其自动控制过程的实施,一点带面,阐述企业充分利用各种资源,实现节能减排的途径.     

应用网络计划技术提高原盐生产效率

网络计划技术是目前比较盛行的一种现代生产管理的科学方法。在各行业生产中应用广泛。文章以扒盐操作为例，把网络计划技术的应用引入到原盐生产中来。     

热泵供热及烘缸干燥强度的研究

通过典型的纸机运行实例研究,证明采用自行研制的可调节式热泵供热系统用于造纸机干燥部,可明显提高纸机烘缸有效面积干燥强度、纸机车速和产量。     

纺织行业节能减排技术应用

高能耗、高水耗和高排放是纺织生产急需解决的问题,简述了革新染整工艺技术,增加高效、连续、短流程的节能减排染整设备,提高能源效率和资源利用率,研发新型多功能衬衣等几方面的改革、调整措施。实践证明这一系列措施在提高产品质量、降低成本、节能减排方面有显著的成效,实现了清洁、绿色生产。     

纺织印染企业污水热能回收与利用的探讨

运用技术分析及经济效益测算的方式,对纺织印染企业采用污水热能回收技术进行了可行性研究。通过对印染企业使用污水热能回收技术的经济及社会效益的综合测算,认为污水热能回收技术不仅可以减少企业的成本支出,而且可以减少废热、废水的任意排放,具有良好的社会效益。其主要目的是通过对污水热能回收项目的可行性分析,旨在促进各印染企业进一步的加强节能减排,强化技术改造和技术创新,将污水回收与利用技术及光伏太阳能再加热技术充分应用到生产中,真正做到为企业增效,为社会增利的效果。     

浅谈国产热能中心

介绍以木竹可燃废料和砂光粉等为燃料的国产热能中心的主要形式、主要系统和主要设计参数。热能中心在绝热炉膛中产生高温烟气,一路用于加热导热油炉中的热油供热压机,同时利用部分导热油加热软水,产生蒸汽用于热磨和制胶;另一路烟气经混合室,除尘后用于干燥。     

油菜不同氮素籽粒生产效率类型品种干物质生产及农艺性状差异

2007～2008年度以98个甘蓝型常规油菜品种（系）为材料,通过测定初花期和成熟期不同器官干重和氮素含量以及成熟期植株农艺性状,采用组内最小平方和动态聚类方法将供试品种（系）按氮素籽粒生产效率（NUEg）从低到高依次分为6类,并研究不同类型材料间干物质生产和农艺性状差异。结果表明,成熟期总生物量、果壳干重和籽粒产量、一次分枝数和角果数可以作为NUEg的初步筛选指标。多元回归和通径分析结果表明,在干物质生产方面,成熟期籽粒和果壳干重对NUEg有显著影响,提高NUEg重点是提高花后角果干物质积累,尤其是籽粒干物质积累;在农艺性状方面,角果数、每角粒数和千粒重对NUEg有显著影响,提高NUEg首先应提高角果数,其次是每角粒数。     

Varying protein and starch in the diet of dairy cows. II. Effects on performance and nitrogen utilization for milk production

The main objective of this experiment was to examine the effects of the percentage and source of crude protein (CP) and the amount of starch in the diet of dairy cows on the lactational performance and use of N for milk production. Sixty multiparous Holstein cows were used in a 210-d lactational trial with a completely randomized design with a 2 × 3 factorial arrangement of treatments. Two sources of CP [solvent-extracted soybean meal (SBM) and a mixture of SBM and a blend of animal-marine protein supplements plus ruminally protected Met (AMB)] and 3 levels of dietary CP (means = 14.8, 16.8, and 18.7%) were combined into 6 treatments. On a dry matter (DM) basis, diets contained 25.0% corn silage, 20.0% alfalfa silage, 10.0% cottonseed, 26.7 to 37.0% corn grain, and 4.8 to 13.5% protein supplement, plus minerals and vitamins. Across the 210 d of lactation, the productive response of dairy cows to the source of supplemental CP depended on the concentration of CP in the diet. At 18.7% CP, cows fed SBM consumed more DM and produced more milk, 3.5% fat-corrected milk, fat, and true protein, but had lower efficiency of feed use and body condition score than cows fed AMB. At 16.8% CP, cows fed AMB produced more 3.5% fat-corrected milk, fat, and true protein than cows fed SBM. At 14.8% CP, cows fed SBM consumed more DM but produced less true protein and had lower feed efficiency than cows fed AMB. Across CP sources, cows fed 14.8% CP produced less fat-corrected milk and true protein than cows fed 16.8 and 18.7% CP. Across CP percentages, cows fed AMB produced more fat-corrected milk per kilogram of DM consumed than cows fed SBM. Despite these interactions, improvements in the gross efficiency of N use for milk production were achieved through reductions in the intake of N independently of the source of CP. Data suggest that the intake of N by high-producing dairy cows that consume sufficient energy and other nutrients to meet their requirements can be decreased to about 600 to 650 g daily if the source of RDP and RUP are properly matched with the source and amount of carbohydrate in the diet.     

Effect of grain- or by-product-based concentrate fed with early- or late-harvested first-cut grass silage on dairy cow performance

This study compared the effects of a grain-based conventional concentrate (GC) and a concentrate based on agro-industrial by-products (BC), fed with grass silage harvested at early (ES) or late (LS) maturity stage, on dairy performance, CH₄ and CO₂ emissions, and metabolic status of dairy cows. Twenty lactating Nordic Red cows averaging 81 d in milk and 31.9 kg of milk/d pre-trial were assigned to a replicated 4 × 4 Latin square design. Dietary treatments were in a 2 × 2 factorial arrangement. The silages were harvested 2 wk apart from the same primary growth grass ley. The GC was made from oats, barley and wheat, and soybean meal, whereas the BC contained sugar beet pulp, wheat bran, canola meal, distillers dried grains, palm kernel expeller, and molasses. The diets were fed ad libitum as total mixed rations and were formulated from 661 g/kg of silage, 326 g/kg of concentrate, and 13 g/kg of minerals on a dry matter basis. The BC supplied the cows with less energy. Despite this, milk yield and composition were unaffected by concentrate type, except that milk protein was 0.7 g/kg lower in cows fed BC than in those fed GC. These results were accompanied by a 44 g/kg decrease in total-tract digestibility of crude protein and a 54 g/kg increase in neutral detergent fiber digestibility for cows fed BC. Cows fed ES on average consumed 2 kg/d more dry matter and yielded 3.5 kg/d more milk, 149 g/d more protein, and 141 g/d more fat than cows fed LS. There were few interaction effects between concentrate and silage sources on daily intake and dairy performance. However, edible feed conversion ratio (human-edible output in animal/potentially human-edible feed) showed greater improvements with ES than LS when replacing GC with BC. Feeding diets with late-cut silage generally reduced digestibility and energy utilization efficiency, but improved N utilization efficiency. Feeding LS also led to greater CH₄ yield and CH₄/CO₂ ratio, and higher plasma concentration of nonesterified fatty acids. Plasma parameters reflecting energy metabolism and inflammation were all within the normal ranges, indicating that the cows were in good health during the experiment. In conclusion, a conventional concentrate can be replaced by agro-industrial by-products without compromising production in early lactation dairy cows. However, silage maturity has a stronger effect on the production traits of dairy cows than type of concentrate.     

Improved energy efficiency of farmers' cooperative litchi drying operation in Northern Thailand

In 2007, Hmong farmers growing litchi in the mountainous region of Northern Thailand started to dry the fruit in response to its declining market price. However, the locally available dryer, although affordable and of a size appropriate for smallholder farmers' cooperatives, showed excessive gas consumption, and this, along with rising fuel costs, imposed a threat to the drying operation. The objective of this study was to test low‐cost, easy‐to‐implement modifications to a locally available convection dryer, to improve its energy efficiency. Experiments were conducted in cooperation with a Hmong farmers' cooperative in Northern Thailand. Insulation of the air ducts and control of the air recirculation rate led to energy cost savings of US$2.45 per dryer‐load. With the modifications required being simple, the investment needed was recovered after only approximately 20 loads, while the energy efficiency of the dryer increased from 33% to 39%.     

硫酸盐浆厂节能技术改造实践

介绍了我国造纸行业主要的耗能设备、国家支持的节能项目及硫酸盐浆厂碱回收溶解槽尾气余热利用原理、方案、案例及效果。