An economic comparison of several models fitted to nutritional response data

Nutritional requirements are typically estimated based on feeding trials with animals or birds offered several amounts of the critical nutrient(s). A nutrient response function is then fitted to data from the feeding trials. Modern computer techniques allow for a variety of functional forms to be used as nutrient response functions. However, the performance of these models is almost undistinguishable from a purely statistical perspective. This paper approaches the issue of determining nutrient requirements from an economic prospective. Crude protein amounts that would maximize profits were calculated for combinations of corn, soybean meal, and live broilers prices using several nutrient response models fitted to technical data from a trial with several balanced CP amounts fed to broiler chickens. Under certain combinations of input prices, differences between the models were between 1.5 and 3.0% CP. No model consistently predicted the greatest or least CP amounts or net profits, emphasizing that the (tangential) slopes of the models change at different rates over the range of nutrient (CP) amounts studied. Models providing adequate statistical fits to research data do not necessarily provide functions that are clearly most appropriate for maximizing producer profits.     

4种画回模型估计鱼营养物质需要量

比较了几种不同的回归模型对营养物质需要量的估计效果.其中包括2种不同的折线回归模型、多项式模型、4参数的Saturation Kinetics模型和5参数的Saturation Kinetics模型.模型拟合采用SAS 9.2 software package的NLIN过程,并给出了相应的SAS代码.     

A comparison of three data mining time series models in prediction of monthly brucellosis surveillance data

The early and accurately detection of brucellosis incidence change is of great importance for implementing brucellosis prevention strategic health planning. The present study investigated and compared the performance of the three data mining techniques, random forest (RF), support vector machine (SVM) and multivariate adaptive regression splines (MARSs), in time series modelling and predicting of monthly brucellosis data from 2005 (March/April) to 2017 (February/March) extracted from a national public health surveillance system in Hamadan located in west of Iran. The performances were compared based on the root mean square errors, mean absolute errors, determination coefficient (R²) and intraclass correlation coefficient criteria. Results indicated that the RF model outperformed the SVM and MARS models in modeling used data and it can be utilized successfully utilized to diagnose the behaviour of brucellosis over time. Further research with application of such novel time series models in practice provides the most appropriate method in the control and prevention of future outbreaks for the epidemiologist.     

A preliminary trial comparison of several anesthetic techniques in cats

The aim of this study was to investigate the effect of several drug combinations (atropine, xylazine, romifidine, methotrimeprazine, midazolam, or fentanyl) with ketamine for short term anesthesia in cats. Twelve cats were anesthetized 6 times by using a cross-over Latin square protocol: methotrimeprazine was combined with midazolam, ketamine, and fentanyl; midazolam and ketamine; romifidine and ketamine; and xylazine and ketamine. Atropine was combined with romifidine and ketamine, and xylazine and ketamine. Temperature, heart rate, and respiratory rate decreased in all groups. Apnea occurred in 1 cat treated with methotrimeprazine, romifidine, and ketamine, suggesting that ventilatory support may be necessary when this protocol is used. Emesis occurred in some cats treated with alpha 2-adrenoceptor agonists, and this side effect should be considered when these drugs are used.     

A comparison of the potency of several Brucella allergens used to detect brucellosis in cattle

The potency of Brucella allergens prepared from a smooth Brucella abortus strain S-99, mucoid strain Leewarden, rough strain 45/20, and rough Brucella melitensis strain B-115 was assessed. The potency of these allergens was compared with that of a standard allergen prepared from smooth Brucella abortus S-99 that efficiently detected bovine brucellosis in other studies. Eight cattle experimentally inoculated with Brucella abortus 544 were tested with the allergens 4 and 10 weeks after infection, and again 8 months after infection. All the allergens effectively detected infection but there was a clear distinction in the mean skin reactions 48 and 72 h after injection of the allergens. The skin reactions provoked by the allergens prepared from smooth or mucoid strains of Brucella were most pronounced 48 h after injection. Skin reactions provoked by allergens prepared from rough strains of Brucella were strongest 72 h after injection. Allergens prepared from smooth or mucoid Brucella strains were more potent in detecting brucellosis than those prepared from rough strains of Brucella.Abbreviations Bruc/OCB Brucellergen OCB - cfu colony-forming units - CFT complement fixation test - ID-DLO Institute voor Dierhouderij en Diergezondheid-Dienst Landbouwkundig Onderzoek - ICFTU international complement fixation units - IU international units - LPS lipopolysaccharide - SAT serum agglutination test - SDTH skin delayed-type hypersensitivity     

4种方法去除血浆纤维蛋白原的效果比较

为筛选大规模制备品质优良、性状稳定的血清抗体产品最适方法,采用自然沉析、凝血酶、冻融、冷乙醇4种方法制备血清,比较4种方法制备的血清在剂量、品质、稳定性上的差异。结果表明,相同剂量的新鲜猪血浆经凝血酶法获得血清剂量最多,自然沉析法最少,冻融法及冷乙醇法介于其间;自然沉析法制备的血清品质最好,总蛋白丢失最少,其次是凝血酶法;统计分析表明,4种方法对制备的血清(猪瘟)抗体效价影响差异均不显著,P=0.620.05;凝血酶法适于大规模制备血清抗体液,长时间保存的最适温度为-20℃,短期保存最适温度为4℃;5℃~15℃的室温环境保存最长不超过14 d。     

Two methods for parameter estimation using multiple-trait models and beef cattle field data

Two methods are presented for estimating variances and covariances from beef cattle field data using multiple-trait sire models. Both methods require that the first trait have no missing records and that the contemporary groups for the second trait be subsets of the contemporary groups for the first trait; however, the second trait may have missing records. One method uses pseudo expectations involving quadratics composed of the solutions and the right-hand sides of the mixed model equations. The other method is an extension of Henderson's Simple Method to the multiple trait case. Neither of these methods requires any inversions of large matrices in the computation of the parameters; therefore, both methods can handle very large sets of data. Four simulated data sets were generated to evaluate the methods. In general, both methods estimated genetic correlations and heritabilities that were close to the Restricted Maximum Likelihood estimates and the true data set values, even when selection within contemporary groups was practiced. The estimates of residual correlations by both methods, however, were biased by selection. These two methods can be useful in estimating variances and covariances from multiple-trait models in large populations that have undergone a minimal amount of selection within contemporary groups.     

A simulation study to assess statistical methods for binary repeated measures data

Binary repeated measures data are commonly encountered in both experimental and observational veterinary studies. Among the wide range of statistical methods and software applicable to such data one major distinction is between marginal and random effects procedures. The objective of the study was to review and assess the performance of marginal and random effects estimation procedures for the analysis of binary repeated measures data. Two simulation studies were carried out, using relatively small, balanced, two-level (time within subjects) datasets. The first study was based on data generated from a marginal model with first order autocorrelation, the second on a random effects model with autocorrelated random effects within subjects. Three versions of the models were considered in which a dichotomous treatment was modelled additively, either between or within subjects, or modelled by a time interaction. Among the studied statistical procedures were: generalized estimating equations (GEE), Marginal Quasi Likelihood, likelihood based on numerical integration, penalized quasi-likelihood, restricted pseudo likelihood and Bayesian Markov Chain Monte Carlo. Results for data generated by the marginal model showed autoregressive GEE to be highly efficient when treatment was within subjects, even with strongly correlated responses. For treatment between subjects, random effects procedures also performed well in some situations; however, a relatively small number of subjects with a short time series proved a challenge for both marginal and random effects procedures. Results for data generated by the random effects model showed bias in estimates from random effects procedures when autocorrelation was present in the data, while the marginal procedures generally gave estimates close to the marginal parameters.     

几种常绿草坪草对干旱胁迫的生理响应

对几种在华南地区保持常绿的草坪草在干旱胁迫下的生理反映应进行了研究,其土壤含水量随着干旱胁迫天数的延长而急剧下降;游离脯氨酸、叶片可溶性糖、MDA以及SOD等指标的测定以及对草坪草抗旱性的综合评判,结果表明:利用多指标综合评价草坪草的耐旱性更加科学合理,综合评价后各供试草种的耐旱性大小依次为:马尼拉结缕草＞海滨雀稗＞近...     

Maplnfo GIS在几种草地类型图数字化方法中的应用

数字化草地类型图给草地资源的管理及利用带来极大便利,具有重要的地位和作用.在介绍草地类型图数字化意义及MapInfo软件的基础上.分剐阐述基于MapIMo GIS运用手扶跟踪数字化、扫描数字化和直接解译数字化3种方法进行草地类型图数字化的过程,对比分析了这3种方法的显著特点.并以新疆阿克陶县20世纪80年代草地类型图的数字化为例.详细介绍了扫描数字化的操作步骤,同时总结了Map-Info GIS在草地类型图数字化应用中的显著优点.     

A comparison of three methods of feline leukaemia virus diagnosis

Samples of blood from pet cats were examined for evidence of feline leukaemia virus (FeLV) by three techniques: virus isolation, immunofluorescence and an enzyme-linked immunosorbent assay (ELISA) Leukassay F. There was good agreement between the results from virus isolation and immunofluorescence. However, about 30 per cent of cats which were positive for FeLV antigen by ELISA were negative by either of the other tests. The status of most of these cats was unchanged four or 12 weeks later.     

Effects of dietary protein levels on the long-term growth response and fitting growth models of gibel carp(Carassius auratus gibelio)

A 41-wk growth trial was conducted to evaluate the effects of dietary protein levels on the long-term growth response and fitting growth models of gibel carp(Carassius auratus gibelio) with an initial body weight of 1.85 ± 0.17 g. The dietary protein levels were designed at 320(P32), 360(P36). 400(P40).and 440 g/kg(P44), respectively. The growth curves of the gibel carp for each group were fitted and analyzed with four nonlinear regression models(Gompertz. logistic. von Bertalanffy and Richards). The final body weights(mean ± SD) of the fish were 226 ± 6.231 ± 7.242 ± 2, and 236 ± 2 g for P32, P36, P40,and P44. respectively. Feed conversion ratio of P40 and P44 groups was significantly lower than that of P32 and P36 groups(P 0.05). Productive protein value of P44 group was significantly lower than that of P32 and P36 groups, but not different from that of P40 group(P 0.05). The growth response of the gibel carp for each group was the best fitted by Richards model with the lowest Chi~2, residual sum of squares and residual variance, then Gompertz and von Bertalanffy growth models, but the logistic model did not fit the data well justified by Chi~2 values. The optimal protein level(400 g/kg) prolonged the stage of fast growth and predicted the highest asymptotic weight, which was close to the harvest size in practice.     

A comparison of methods to estimate genomic relationships using pedigree and markers in livestock populations

Accurate prediction of breeding values depends on capturing the variability in genome sharing of relatives with the same pedigree relationship. Here, we compare two approaches to set up genomic relationship matrices for precision of genomic relationships (GR) and accuracy of estimated breeding values (GEBV). Real and simulated data (pigs, 60k SNP) were analysed, and GR were estimated using two approaches: (i) identity by state, corrected with either the observed ( G _{VR ‐O} ) or the base population ( G _{VR ‐B} ) allele frequencies and (ii) identity by descent using linkage analysis ( G _{IBD ‐L} ). Estimators were evaluated for precision and empirical bias with respect to true pedigree IBD GR. All three estimators had very low bias. G _{IBD ‐L} displayed the lowest sampling error and the highest correlation with true genome‐shared values. G _{VR ‐B} approximated G _{IBD ‐L} 's correlation and had lower error than G _{VR ‐O} . Accuracy of GEBV for selection candidates was significantly higher when G _{IBD ‐L} was used and identical between G _{VR ‐O} and G _{VR ‐B} . In real data, G _{IBD ‐L} 's sampling standard deviation was the closest to the theoretical value for each pedigree relationship. Use of pedigree to calculate GR improved the precision of estimates and the accuracy of GEBV.     

A comparison of pH determination methods in food animal practice

The accuracy of a portable pH meter in measuring blood pH in neonatal calves, urine pH, and ruminal fluid pH in cows has been assessed. Thirty-five diarrheic and 15 healthy beef calves were used for blood gas analysis; 57 healthy dairy cows provided voided urine samples; and ruminal fluid samples were obtained from 10 dairy cows with ruminal fistulas on 4 separate days. Measurements of blood pH were obtained from an automated blood gas analyzer and the portable pH meter. Measurements of urine and ruminal fluid pH were determined with the benchtop pH meter, urinalysis strips, narrow range pH paper, and the portable pH meter. The portable pH meter was more accurate in measuring urine pH and ruminal fluid pH in cows than blood pH in neonatal calves. The urinalysis strips and the narrow range pH paper were found adequate to evaluate urine and ruminal pH.