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161.
Munir Iqbal Tahir Yaqub Nadia Mukhtar Muhammad Z Shabbir John W McCauley 《Veterinary research》2013,44(1):100
Genetic changes in avian influenza viruses influence their infectivity, virulence and transmission. Recently we identified a novel genotype of H9N2 viruses in widespread circulation in poultry in Pakistan that contained polymerases (PB2, PB1 and PA) and non-structural (NS) gene segments identical to highly pathogenic H7N3 viruses. Here, we investigated the potential of these viruses to cause disease and assessed the transmission capability of the virus within and between poultry and wild terrestrial avian species. Groups of broilers, layers, jungle fowl, quail, sparrows or crows were infected with a representative strain (A/chicken/UDL-01/08) of this H9N2 virus and then mixed with naïve birds of the same breed or species, or different species to examine transmission. With the exception of crows, all directly inoculated and contact birds showed clinical signs, varying in severity with quail showing the most pronounced clinical signs. Virus shedding was detected in all infected birds, with quail showing the greatest levels of virus secretion, but only very low levels of virus were found in directly infected crow samples. Efficient virus intra-species transmission was observed within each group with the exception of crows in which no evidence of transmission was seen. Interspecies transmission was examined between chickens and sparrows and vice versa and efficient transmission was seen in either direction. These results highlight the ease of spread of this group of H9N2 viruses between domesticated poultry and sparrows and show that sparrows need to be considered as a high risk species for transmitting H9N2 viruses between premises. 相似文献
162.
Sadrollah Molaei Moghbeli Arsalan Barazandeh Mahmood Vatankhah Mohammadreza Mohammadabadi 《Tropical animal health and production》2013,45(7):1519-1524
Genetic parameters were estimated for 6-month weight (W6), 9-month weight (W9), 12-month weight (W12), average daily gain from birth to 6 months old (ADG6), and Kleiber ratio at 6 months (KL6) traits using 6,442 records obtained from a Raini Cashmere goat flock. The parameters were estimated using the restricted maximum likelihood procedure and applying four animal models excluding or including maternal additive genetic and permanent environmental effects. Heritability estimates for W6, W9, W12, ADG6, and KL6, under the most appropriate model were 0.028, 0.26, 0.29, 0.02, and 0.25, respectively. The estimates of genetic and phenotypic correlations among W6, W9, W12, and ADG6 were high and ranged from 0.73 to 0.99. The estimates of genetic and phenotypic correlations among KL6 and others traits were negative and low. Thus, these estimates of genetic parameters may provide a basis for deriving selection indices for postweaning growth traits also low genetic correlation between growth traits with KL6, it is possible to increase efficiency in Raini kids by multitrait selection. 相似文献
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165.
Faisal Mahmood Jacques Wery Sabir Hussain Tanvir Shahzad Muhammed Arslan Ashraf Olivier Therond 《Archives of Agronomy and Soil Science》2016,62(2):217-234
Cropping system models are widely used tools for simulating the growth and development of crops at field scale. However, it is often difficult to satisfy their detailed input and output data requirements for a proper evaluation of model. In this study, expert knowledge data were used as alternative source to fulfil these data requirements. The model was first calibrated for major crops of the studied area and then evaluated for the same crops by using expert knowledge data. Results showed that the model accurately simulated above-ground biomass and grain yield with a relative root mean square error (RRMSE) of 20% and 17%, respectively. On the other hand, simulated results were less satisfactory for N uptake and cumulated evapotranspiration with RRMSE of 27% and 31%, respectively. The model simulated cumulative variables more accurately than dynamic variables. The results of this study suggest that expert knowledge can be used to get data for intermediate variables rarely measured in experiments used for calibration (green leaf area index, actual evapotranspiration, rooting depth) in typical crop management conditions in the region. This approach enables a global and dynamic evaluation of cropping system models when experimental data is unavailable for large heterogeneous areas in a region. 相似文献
166.
Bhatti SA Ahmed MF Wynn PC McGill D Sarwar M Afzal M Ullah E Khan MA Khan MS Bush R Warriach HM Khan A 《Tropical animal health and production》2012,44(4):819-826
The objective was to study the growth potential of Sahiwal calves given milk or milk replacer with or without concentrates. For this purpose, forty-eight Sahiwal calves were divided into four groups of 12 animals each with equal sex ratio. In each group, the calves were offered either milk or a milk replacer (MR) at a rate of 10% of their body weight adjusted weekly. In addition to this, calves were fed either a starter ration plus Egyptian clover hay (SR + H) or hay only (H) until the end of trial. The milk or MR was withdrawn gradually from day 56 until animals were weaned completely by day 84. Calves offered milk grew faster than those offered MR (357 ± 9 vs. 162 ± 9 g/day; p < 0.05) and displayed higher weaning weights (51.6 ± 0.8 vs. 35.2 ± 0.8 kg; p < 0.05). The calves offered SR + H grew faster (311 ± 9 vs. 208 ± 9 g/day; p < 0.05) and displayed higher weaning weights (48.7 ± 0.8 vs. 38.1 ± 0.8 kg; p < 0.05) than those fed H alone. Calves offered milk plus SR + H showed the highest growth rate and weaning weights (401 ± 13 g/day and 56.3 ± 1 kg, respectively). The lowest growth rate and weaning weights were observed in calves offered MR and H only (115 ± 13 g/day and 30.3 ± 1 kg, respectively). Calves offered the MR had higher number of scour days than those offered milk (13.5 vs. 3.3). The feeding of whole milk in combination with the starter ration and hay resulted in superior growth rates, higher weaning weights, and healthier calves than the other feeding regimens. 相似文献
167.
Barazandeh A Moghbeli SM Vatankhah M Mohammadabadi M 《Tropical animal health and production》2012,44(4):811-817
Data and pedigree information used in the present study were 3,022 records of kids obtained from the breeding station of Raini
goat. The studied traits were birth weight (BW), weaning weight (WW), average daily gain from birth to weaning (ADG) and Kleiber
ratio at weaning (KR). The model included the fixed effects of sex of kid, type of birth, age of dam, year of birth, month
of birth, and age of kid (days) as covariate that had significant effects, and random effects direct additive genetic, maternal
additive genetic, maternal permanent environmental effects and residual. (Co) variance components were estimated using univariate
and multivariate analysis by WOMBAT software applying four animal models including and ignoring maternal effects. Likelihood
ratio test used to determine the most appropriate models. Heritability
( \texth\texta2 ) \left( {{\text{h}}_{\text{a}}^2} \right) estimates for BW, WW, ADG, and KR according to suitable model were 0.12 ± 0.05, 0.08 ± 0.06, 0.10 ± 0.06, and 0.06 ± 0.05,
respectively. Estimates of the proportion of maternal permanent environmental effect to phenotypic variance (c
2) were 0.17 ± 0.03, 0.07 ± 0.03, and 0.07 ± 0.03 for BW, WW, and ADG, respectively. Genetic correlations among traits were
positive and ranged from 0.53 (BW-ADG) to 1.00 (WW-ADG, WW-KR, and ADG-KR). The maternal permanent environmental correlations
between BW-WW, BW-ADG, and WW-ADG were 0.54, 0.48, and 0.99, respectively. Results indicated that maternal effects, especially
maternal permanent environmental effects are an important source of variation in pre-weaning growth trait and ignoring those
in the model redound incorrect genetic evaluation of kids. 相似文献
168.
169.
秸秆还田深松旋埋联合耕整机设计与试验 总被引:4,自引:3,他引:1
深松作业能有效打破犁底层,提高土壤蓄水保墒能力。秸秆还田是秸秆资源利用最为直接有效的方式,将2种保护性耕作方式结合在一起可大大提高作业效率。为了满足深松和秸秆还田同时作业的需求,设计了集土壤深松、破茬碎土、秸秆旋埋、平地等多功能于一体的深松旋埋联合耕整机。该机主要由自激振动深松装置和秸秆还田旋埋刀辊组成,自激振动深松装置可调节预紧力,不仅可以在一定程度上减少深松耕作阻力,还可以在遇到障碍物时有效保护深松铲,深松铲柄的设计利用了滑切原理,可有效切断秸秆和杂草,防止缠绕和堵塞深松铲,对旋埋刀辊进行了重新布置和优化,提高了工作稳定性和破土能力。田间试验表明深松作业可有效减小旋埋刀辊功率;在拖拉机1挡和2挡速度下深松旋埋组合作业总功率分别为单独深松和单独旋埋2项作业之和的85.0%和82.2%;深松旋埋组合作业下深松和旋埋的平均耕深分别为28.9和17.5 cm,耕深稳定性分别为93.5%和87.4%,秸秆埋覆率为92.0%,耕后地表平整度为1.0 cm,深松旋埋联合作业后的各项性能参数均超过质量评定指标,满足农艺要求。 相似文献
170.
Muhammad Asif Naeem Muhammad Khalid Muhammad Aon Ghulam Abbas Muhammad Tahir Muhammad Amjad 《Archives of Agronomy and Soil Science》2017,63(14):2048-2061
The objective of this work was to study the effect of different biochar on alkaline calcareous soil, inherently low in soil organic carbon and fertility. Experiments were conducted in laboratory and greenhouse. Biochar was produced from wheat and rice straws at pyrolysis temperatures of 300°C, 400°C and 500°C (denoted as WSB300, WSB400, WSB500, RSB300, RSB400 and RSB500, respectively). In the first experiment, soil was incubated with biochar (1.0 % w/w) for up to 50 weeks. The results indicate that, WSB300 caused a significant decrease in soil pH and increased the CEC and nutrients (N, P and K) after 50 weeks of incubation. In the second experiment, maize plants were grown in pots containing calcareous soil amended with WSB and RSB for 60 days the results revealed that the application of WSB300 caused a significant increase in shoot (36%) and root (38%) dry matters over the respective control. Moreover, the highest nutrient concentrations (N and P) in shoot and root were observed with the WSB300 compared to other treatments. Therefore, it is concluded that application of wheat straw biochar produced at low temperature (WSB300) could be successfully used to improve soil properties and growth of plants in calcareous soils. 相似文献