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101.
Afshin Raoofi Farhid Hemmatzadeh Amir Mansoor Ghanaei 《Tropical animal health and production》2010,42(3):411-414
This serological survey was carried out to detect antibodies in dromedary camels against BVD virus in Iran. A total of 137
serum samples, were collected from camels at Khorein abattoir in suburbs of Tehran and examined for BVDV, using the serum
neutralization test (SNT). Twenty seven of the 137 camels (19.7%) were positive for BVDV antibodies. It was found that the
rate of seropositive camels in Iran is substantially higher compared to figures published in most other countries. This study
indicated an increased frequency of infection rate with increasing age of camels. The frequency of positive cases was not
significantly different between male and female camels. 相似文献
102.
Krishna Mohan Vijay Kumar Mihir Sarkar B. S. Prakash 《Tropical animal health and production》2010,42(1):21-26
The objective of this study were (1) to establish the duration of behavioral estrus signs and timing of ovulation in Murrah
buffaloes (n = 10) and (2) to determine relationship between behavioral estrus signs with change in plasma estrogen concentrations.
Estrus and its behavioral signs were detected at hourly intervals by visual observations, per recta examination of genitalia
and bull parading four times in a day for 30 minutes each. Among the behavioral signs of estrus, swollen vulva (80%) was the
best indicator of estrus followed by excitement (70%). Among the duration of behavioral estrus signs the first and longest
duration of estrus signs was swollen vulva which was seen upto 19.8 ± 0.8 h after onset of estrus. The mean total duration
of estrus symptoms from appearance to disappearance of all the behavioral estrus symptoms was 23.5 ± 1.7 h. All the behavioral
estrus symptoms were observed during the period of estrogen surge. Endocrine profile during the periestrus period showed that
the mean peak concentrations of total estrogen 23.9 ± 3.9 pg/ml occurred at 8.8 ± 1.7 h after onset of estrus. The average
number of estrus symptoms observed per animal during onset of spontaneous estrus was 5.7. Ovulation occurred after 37.4 ± 1.7 h
after onset of estrus and 13.4 ± 1.0 h after end of total estrogen surge respectively. In conclusion, our results suggest
that all signs of behavioral estrus occurred during the preovulatory rise in estrogens. The first sign of estrus to be observed
was a swollen vulva and this symptom persisted the longest. 相似文献
103.
Ryan B. Mounce Susan A. O’Shaughnessy Brock C. Blaser Paul D. Colaizzi Steven R. Evett 《Irrigation Science》2016,34(3):231-244
In the High Plains, corn (Zea mays L.) is an important commodity for livestock feed. However, limited water resources and drought conditions continue to hinder corn production. Drought-tolerant (DT) corn hybrids could help maintain high yields under water-limited conditions, though consistent response of such hybrids is unverified. In this two-year study, the effects of three irrigation treatments were investigated for a DT and conventional maize hybrid, Pioneer AQUAMax P0876HR and Pioneer 33Y75, respectively. In 2013, the drier of the 2 years, irrigation amounts and crop water use (ETc) were greater for the conventional hybrid, but grain water use efficiency (WUE) and harvest index were significantly greater for the DT hybrid. In 2014, grain yields and WUE were not significantly different between hybrids. However, irrigation amounts, ETc and biomass yields were greater for the conventional hybrid. Results from both years indicate that the DT hybrid required less water to maximize grain yield as compared to the conventional hybrid. Producing relatively high yields with reduced amounts of water may provide a means for producers to continue corn production in a semiarid environment with declining water supplies. 相似文献
104.
José AlvesJr Marcos V. Folegatti Larry R. Parsons Wije Bandaranayake Claudio R. da Silva Tonny J. A. da Silva Luís F. S. M. Campeche 《Irrigation Science》2007,25(4):419-428
The expansion of permanent trickle irrigation systems in Sao Paulo (Brazil) citrus has changed the focus of irrigation scheduling
from determining irrigation timing to quantifying irrigation amounts. The water requirements of citrus orchards are difficult
to estimate, since they are influenced by heterogeneous factors such as age, planting density and irrigation system. In this
study, we estimated the water requirements of young ‘Tahiti’ lime orchards, considering the independent contributions from
soil evaporation and crop transpiration by splitting the crop coefficient (Kc = ETc/ETo) into two separate coefficients; Ke,
a soil evaporation coefficient and Kcb, a crop transpiration coefficient. Hence, the water requirement in young ‘Tahiti’ lime
(ETy) is ETy = (Ke + Kcb) · ETo, where ETo is the reference crop evapotranspiration. Mature tree water requirement (ETm) is ETm = Kcb · ETo, assuming no soil water evaporation. Two lysimeters were used; one was 1.6 m in diameter and 0.7 m deep, and
the other was 2.7 m in diameter and 0.8-m deep. The first one was used to calculate evaporation and the second one was used
for transpiration. ETo was estimated by the Penman–Monteith method (FAO-56). The measurements were conducted during a period
between August 2002 and April 2005 in Piracicaba, Sao Paulo state, Brazil. The lysimeters were installed at the center of
a 1.0-ha plot planted with ‘Tahiti’ lime trees grafted on ‘Swingle’ citrumelo rootstock. The trees were 1-year old at planting,
spaced 7 × 4 m, and were irrigated by a drip irrigation system. During the study period, Kc varied between 0.6 and 1.22, and
Kcb varied between 0.4 and 1.0. The results suggested that for young lime trees, the volume of water per tree calculated by
Ke + Kcb is about 80% higher than the volume calculated using Kc. For mature trees, the volume of water per tree calculated
using just Kcb can be 10% less than using Kc. The independent influence of soil evaporation and transpiration is important to better understand the water consumption of
young lime trees during growth compared to mature lime trees. 相似文献
105.
A systematic and quantitative approach to improve water use efficiency in agriculture 总被引:4,自引:2,他引:4
As the competition for the finite water resources on earth increases due to growth in population and affluence, agriculture
is faced with intensifying pressure to improve the efficiency of water used for food production. The causes for the relatively
low water use efficiency in agriculture are numerous and complex, including environmental, biological, engineering, management,
social, and economic facets. The complexity of the problem, with its myriads of local variations, requires a comprehensive
conceptual framework of the underlying physical and biological processes as the basis to analyze the existing situation and
quantify the efficiencies, and to plan and execute improvements. This paper proposes such a framework, based on the simple
fact that the overall efficiency of any process consisting of a chain of sequential step is the product of the efficiency
(i.e., output/input ratio) of its individual component steps. In most cases of water use, a number of process chains, both
branching and merging, are involved. Means to integrate the diverging and converging chains are developed and presented as
equations. Upscaling from fields to regions and beyond are discussed. This chain of efficiencies approach is general and can
be applied to any process composed of chains of sequential steps. Here the framework is used to analyze the systems of irrigated
and dryland crop production, and animal production on rangeland. Range of plausible efficiencies of each step is presented
as tables, with values separately for the poor and for the good situation of circumstances, management and technology. Causes
of the differences in efficiency of each step, going from water delivery to soil water extraction, transpiration, photosynthesis,
and conversion to crop biomass and yield, and to animal product are briefly discussed. Sample calculations are made to demonstrate
how modest differences in the efficiencies of the component steps are manifested as large to huge differences in the overall
efficiency. Based on an equation quantifying the impact of changes in efficiency of component steps on the overall efficiency,
it is concluded that generally, it is more effective to made modest improvements in several or more steps than to concentrate
efforts to improve one or two steps. Hence, improvement efforts should be systematic and not overly concentrated on one or
two components. The potential use of the same equation as the point of departure to optimize the allocation of economic resource
among the component steps to maximize the improvement in the overall water use efficiency is elaborated on. The chain of efficiencies
framework provides the means to examine the current levels of efficiency along the pathways of agricultural water use, to
analyze where inefficiencies lie by comparing with the range of known efficiency values in the tables presented, to assess
the potential improvements that may be achieved in various parts and their impact on the overall efficiency, and to aid in
the optimal allocation of resources for improvements.
相似文献
Theodore C. HsiaoEmail: |
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