Influence of Production and Prices on Optimum Culling Rates and Annualized Net Revenue

Dynamic programming was used to make optimum insemination and culling decisions for a dairy enterprise. Monthly costs and revenues for cows were calculated from milk and fat yields, calf values, feed costs, veterinary costs, housing and equipment costs, and interest. Cows were described in the dynamic programming model by lactation number, month in lactation, milk production during the present and previous lactations, and time of conception. The model considered variation in milk yield, replacement heifer costs, carcass values, involuntary culling, genetic improvement, conception rates, semen costs, and interest. Prices and parameters were chosen to represent the Holstein population in the US. Optimum average yearly culling rate was about 25% (optimum average herd life was 47.8 mo) and the yearly annuity of net revenue for a replacement heifer over a 15-yr planning horizon was $443 in the base situation. Various average mature equivalent yields, replacement heifer prices, milk prices, and feed prices were used in a sensitivity analysis. The yearly annuity of net revenue was sensitive to changes in all these parameters. Milk yield, milk prices, and feed prices had major effects on yearly annuity. Optimum culling decisions were sensitive to changes in replacement heifer prices. Average mature equivalent milk yield, milk price, and feed price had small effects on culling.     

Comparison of Culling Rates,Reasons for Disposal,and Yields for Registered and Grade Holstein Cattle

Survival of cows was investigated using data from the USDA files for daughters of 199 Holstein sires with at least 500 progeny each. Records included cows that first calved from 1965 to 1980 (n = 1,145,616). A smaller subset of data (n = 199,982) was summarized for age at first and last record, termination codes, Modified contemporary deviations of milk yield, and calving intervals. Grade cows leaving the herd were more likely sold for low production and less likely sold for dairy. Modified contemporary deviations in first lactation averaged 339 kg for grade cows and 331 kg for registered cows. Cows with only one record had lower yields in first lactation by 589 kg (grade) and 506 kg (registered). Compared with cows with more than two lactations, cows with two records had lower yields in first lactation by 199 kg (grade) and 259 kg (registered) and longer first calving intervals by 3.5 d (grade) and 5.0 d (registered). Grade and registered daughters of these sires left herds at different rates and for different reasons.     

Dairy Cow Culling Decision. 2. Profitability and Genetic Trend in Herds with Culling on Production Versus Income

A technique has been described for culling cows on a combination of screening the entire herd on short-term income and then culling the cow making the smallest contribution to herd income over probable remaining herd life. The objective of this study was to determine the long-term effects on herd profitability and herd genetic trend of culling on a combination of short-term and long-term cow income instead of culling on age adjusted production. In addition, the effect of timing of the culling decision either prebreeding (to save insemination costs) or postbreeding (when time of next freshening can be predicted) on herd income was evaluated. Culling on projected income increased herd income over 20 yr by 4.3 to 4.8% relative to culling on age adjusted production for complete lactation. Breeding only the highest producing cows and then culling infertile cows at the point of peak income in the lactation increased herd income over 20 yr by 4.3 and 5.7% relative to breeding all cows and then culling the lowest producing cow in the herd when a heifer freshened. Cow culling on income projections decreased the genetic trend to 65.3 to 86.2% of the gain observed with cow selection on age adjusted production. Due to the potential economic benefits from both choosing culls prebreeding and utilizing a profitability criterion for cow culling, income projection techniques that describe the reproductive performance of the open cow need to be developed.     

Dairy Cow Culling Decision. 3. Risk of Culling on Predicted Income (An Application of Bayes Criterion)

Comparison of cows on their potential for income production or cash flow over multiple calving intervals has been utilized for culling. The reliability of income projections several years in the future may be questioned when the economic environment is uncertain. The problem would be apparent when cull candidates differ in age since a mature cow would be selected for immediate productivity whereas the immature cow would be selected for her long-term potential. When an uncertain change in the economic environment (e.g., milk price) results in a difference in ranking of two cull candidates, the Bayes criterion of selecting the animal with the highest expected value for income can be utilized. A sensitivity analysis can then determine the dependence of the decision on variation in milk price or other states of nature. The value of perfect information would assess the financial risk associated with the decision. In an example analyzed with a probable 5% decline in milk prices, information that would reduce the variability in predicting animal performance had more effect on the payoff of the culling decision than more accurate predictions of future milk prices.     

Influence of Specified Farm Management Factors on Dairy Farm Net Income

The association between specified management factors and net income was investigated to determine the amount of variation in net income that could be explained by these factors and their relative importance in explaining this variation. The source of information was 340 Michigan dairy farms, utilizing both D.H.I.A. and mail-in farm account records from 1958 through 1962. A multiple regression analysis was used to study the relationship between 38 management factors and net income.Fourteen factors were significant (P < .05) in explaining variations in net income. The coefficient of determination, R², was .75. Factors related to size, cropping practices, and dairy herd operation accounted for 28, 25, and 29% of the explained variation, respectively. Machinery expense, organization and intensity factors accounted for the remaining 18%. Livestock income per $100 feed expense and crop value per tillable acre accounted for 87% of the variation in net income attributed to all livestock and crop factors. Efforts to determine sources of variation in livestock income per $100 feed expense and crop value per tillable acre resulted in coefficients of determination of .87 and .93, respectively.     

施钾量对烤烟钾积累与分配的影响

研究四川省凉山州主栽烤烟品种云烟85对钾的积累和分配特征,可为当地合理施用钾肥提供理论依据。以云烟85为材料进行土培盆栽和大田试验,分析了不同施钾量下云烟85的产量、含钾量、钾积累量和钾分配率,探讨施钾量对云烟85钾积累与分配的影响。结果表明,云烟85在不同钾肥用量下的钾积累高峰均出现在旺长后期和中部叶成熟期。随着钾肥用量的增加,烟叶产量、含钾量、钾积累量和钾分配率先增大后减小,含钾量和钾积累量差异显著。本试验条件下,种植云烟85的最佳钾肥用量为158kg／hm2。在凉山烟区种植云烟85时,可适当降低钾肥用量,并增加后期钾肥追施比例,在保证产量的同时,有望提高烟叶含钾量。     

Influence of Electrical Stimulation, Cooling Rates and Aging on the Shear Force Values of Chilled Lamb

An investigation using high voltage (800 VRMS, 1140 V peak at 14.3 Hz) electrical stimulation (ES) showed that lambs should be stimulated within 30 min of slaughter for 60–120 sec for maximum effect on Warner-Bratzler shear force values. Shear force values of lamb muscles chilled at different rates were significantly (P<0.001) reduced by ES, compared with nonstimulated controls. However, aging at temperatures between 0° and 9°C, for only 2–3 days, educed shear force values of nonstimulated lamb subjected to moderate chilling rates to those of ES samples at 1 day postmortem. Increasing aging temperature significantly (P<0.001) increased aging rate but duration of aging had the greater effect.     

Influence of Heating and Cooling Rates on Bacillus cereus Spore Survival and Growth in a Broth Medium and in Rice

Survival, spore germination, and growth of emetic and diarrheal type strains of Bacillus cereus were evaluated in broth and rice media during heating and cooling. Samples were heated to 80°C (20C°/hr or 40C°/hr) or 90°C (ca. 900C°/hr), prior to cooling to 10°C (5C°/hr or 10C°/hr). Following heating to 80°C, growth occurred during 5C°/hr cooling. After heating to 90°C, inactivation of three strains occurred during cooling from 90 to 80°C and again from 50 to 40°C. Great variability was observed among the responses of the four strains. Emetic strains exhibited greater survival than diarrheal strains. Rice reduced low temperature inactivation, and did not favor emetic strains. Significant two and three way interactions existed among media, strains, heating and cooling rates.     

Government Policies and Revenue of Dairy Farmers

The impact of obtaining a balance between production and consumption through a production quota, a price support reduction, and an assessment is analyzed. Production quota would have reduced farmers total revenue by 3.51%, price support reduction would have reduced farmers total revenue by 11.44%, and assessment would have reduced farmers’ total revenue by 32.39% if excess production (USDA net removals) had been reduced from 1648 to 480 million pounds during the fourth quarter of 1981. Thus, government expenditures would have been reduced 70.87% by quota and assessment and 74.23% by a price support reduction.     

The Influence of Oxygen Volumetric Mass Transfer Rates on Cyclodextrin Glycosyltransferase Production by Alkaliphilic Bacillus circulans in Batch and Fed-Batch Cultivations

In this work, the influence of oxygen mass transfer rates on the production of cyclodextrin glycosyltransferase (CGTase) by the alkaliphilic bacterium Bacillus circulans ATCC 21783 was investigated. Experimental design and response surface methodology were applied to optimize agitation speed and air flow rate in batch cultivations, in order to identify their significant effects and interactions with the synthesis of CGTase. Results were expressed as the volumetric mass transfer rates of oxygen (k_la, [per hour]). The maximal CGTase productivity of 155 U mL⁻¹ h⁻¹ was achieved with k_la of 48 h⁻¹. CGTase production was also studied in fed-batch cultures using the optimized parameters obtained in the batch experiments. The maximal CGTase productivity on fed-batch cultivations was 137 U mL⁻¹ h⁻¹ with feeding rates of starch at 0.17 g L⁻¹ h⁻¹.     

转谷氨酰胺酶在尼龙网上的固定化及其酶学性质的研究

以硫酸二甲酯活化后的尼龙网为载体,戊二醛为交联剂固定转谷氨酰胺酶,并对固定化条件及固定化酶的酶学性质进行研究。结果表明固定化的最适条件为：1cm2 处理后的尼龙网与20ml 7% 的戊二醛交联5h 后,在4℃条件下固定10ml 1.5mg/ml 的转谷氨酰胺酶溶液6h,此条件下酶活回收率达到46%。固定化转谷氨酰胺酶相对于游离酶具有更好的热稳定性,并具有良好的储存性及操作稳定性。     

羽毛降解的反应条件研究

采用酸解﹑碱水解﹑氧化还原等方法对羽毛进行溶解,通过奥氏黏度仪,分光光度仪等方式测定不同反应条件下水解后的分子量、收率和蛋白质的浓度, 优化出了相对分子量大,蛋白含量高的条件:CH3CH2ONH2-NaOH﹑反应温度90℃、反应时间2h.减轻了分子量和收率之间的矛盾.     

羽毛降解的反应条件研究

采用酸解？碱水解？氧化还原等方法对羽毛进行溶解,通过奥氏黏度仪,分光光度仪等方式测定不同反应条件下水解后的分子量、收率和蛋白质的浓度,优化出了相对分子量大,蛋白含量高的条件：CH3CH2ONH2-NaOH？反应温度90℃、反应时间2 h。减轻了分子量和收率之间的矛盾。     

Dissolved Air and Rates of Wetting

Recent models of the pilling process are discussed with reference to their usefulness as a predictive tool. An alternative approach is suggested in which computer-simulation techniques are used. A simulation model is proposed and exercised with a series of factorial experiments. The results are analysed by using the design matrix.     

数控机床的网络化

电子通讯技术、网络技术及Internet的发展使网络化制造成为可能。设备层是数控机床实现网络化制造的基础,本文阐述了网络化制造给设备层带来的变化,列出了数控机床实现联网的三种类型。     

造纸企业排产模型优化及设计

在基于传统的生产调度模型的基础上,引入激励机制和心理因素,并从多目标优化建模到遗传算法寻优,提出了一种基于遗传算法求解造纸企业优化排产模型。进行了算法设计和仿真研究,验证了该方案的可行性,解决了订单的优化排产问题。     

新型织机网络监测管理系统的研究

通过采用RS-485／CAN现场总线技术构成新型织机计算机网络监测系统，对于节点比较多、现场干扰影响比较大的控制网络，通过采取有效的硬件措施，制定周密的通信协议，可以极大地提高整个系统抗干扰能力。确保了数据通信的准确性和快速性，为纺织企业密集型设备生产进行产质量管理提供数字化、信息化的技术保证。     

大力推广防虫网发展无公害蔬菜栽培

防虫网覆盖栽培是农产品无公害生产的重要措施之一,也是继遮阳网之后的又一项极具生命力的设施栽培新技术.该项技术对不用或少用化学农药减少农药污染,生产出无农药残留、无污染、无公害的蔬菜具有重要意义,已成为当前蔬菜尤其是叶类菜栽培的一种新兴模式.     

不同施肥水平对中烟100产质量的影响

为了确定中烟100合适的施肥水平及烟叶产量,通过1年2地点(山东沂水、费县)的田间试验,研究了高、中、低及零肥量对中烟100产量和质量的影响。结果表明,烟叶产量、均价等随施肥量的增加而提高,当施氮量达到105 kg/666.7m2时,上等烟比例和均价最高;高肥力下施氮75 kg/hm2、中等肥力下施氮142.5 kg/hm2时,烟叶感官质量最佳;中烟100需要较高的营养供应水平,获得较佳质量的产量低限为2250 kg/hm2。     

板粟深加工中淀粉的酶水解研究

试验对比了BAA中温α-淀粉酶和耐高温α-(Termamyl 120L,S型)对板栗浆液中淀粉的液化效果，选择使用耐高温α-淀粉酶(Termamyl 1120L，S型)为液化板栗淀粉的作用酶，单因素研究确定了液化工艺参数为：料水比1：5，液化温度90℃，pH6．0，酶用量7U／g果肉，液化时间60min。然后采用Novozym^TMAG糖化酶对液化后的板粟淀粉进行糖化，以淀粉水解度(DE值)和糖化液中还原糖的含量(g／100m1)为指标，正交试验表明，在糖化温度60℃，pH4．5，Novozym^TMAG使用量为80U／g果肉的条件下糖化90min，可使水解度(DE值)和糖化液中还原糖含量(g／100m1)分别达到48．9％和4．52g／100ml。