Ultrasonographic findings in cows with left displacement of abomasum, before and after reposition surgery.

BACKGROUND: The natural incidence of left displacement of abomasum (LDA) in dairy cows was high. The diagnosis of LDA usually relies on characteristic physical exam findings but that transabdominal ultrasound is a useful technique that has been applied to the diagnosis of gastrointestinal diseases of dairy cows in equivocal cases. METHODS: Forty dairy cows with LDA were clinically and ultrasonographically examined to determine the position and the echogenic property of the abomasum. The cows were examined ultrasonographically on the left side, from the 9th intercostal space (ICS) to the 12th ICS as well as the ventral left abdomen before and after reposition surgery. RESULTS: The vital signs were within normal range in most of the cows and the 'pinging' were clearly heard in 37 cows. The abomasal gas cap was visualized from the 9th to 12th ICS in 37 cows and characterized by reverberation artifacts. The abomasal ingesta appeared as homogeneous hypoechoic fluid with scattered hyperechoic foci and were mainly visible in the median region and ventral region of the 9th to 11th ICS in 35 cows. The pyloric canal was detected from the ventral left abdomen wall in 30 cows and appeared as a loop with hypoechogenic wall and echogenic luminal contents in cross section. CONCLUSION: These typical ultrasonograms, including reverberation artifacts, homogenous hypoechoic structures, are important diagnostic feature in ultrasonography of LDA. Furthermore, the circular acoustic image structure of the pyloric canal is an important characteristic of LDA, so it can be used as an important diagnostic basis of LDA.

[Effects of drought stress on performance of photosystem II in maize seedling stage].

Maize cultivar Shandan 609 was used to determine the effects of drought stress on photosystem II, dry matter accumulation, protective enzyme activity and proline content at seedling stage in pot experiment. Two drought treatments (moderate drought and severe drought) were tested. The results showed that dry matter accumulation, leaf area and plant height of cultivar shaandan 609 decreased significantly with the increasing drought stress. The less grouped PS II units (L-band > 0), severely damaged OEC (K-band > 0), and the inhibited acceptor side (ψo significantly decreased) resulted in the overall dropped performance of PS II (PI(ABS)). Under the condition of moderate and severe drought stress, the activities of superoxide, peroxidase, catalase and proline content increased significantly, which were 1.3, 1.1, 1.2, 5.8 and 1.1, 3.3, 1.5, 15.0 times of control (CK), respectively. Those results indicated that damage of PS II acceptor and donor side under drought stress led to the decline of PS II performance, which was likely to cause the decline of dry mater accumulation of maize cultivar Shandan 609, while protective enzymes and proline as protective substance in plant played a positive role in drought resistance.

[Effects of low nitrogen stress on source-sink characters and grain-filling traits of different genotypes summer maize].

This paper studied the source-sink characters and grain-filling traits of six genotype summer maize varieties under 2 years (from 2007 to 2008) application of low dosage (105 kg x hm(-2)) and normal dosage (337.5 kg x hm(-2)) fertilizer nitrogen. Under low nitrogen stress, the population yield, leaf area index (LAI), source-sink characters, and grain-filling traits of test varieties differed significantly. The varieties tolerant to low nitrogen, e.g., Xianyu 335 and Zhengdan 958, had longer active grain-filling stage, higher maximum filling rate, longer duration of maximum LAI, and more harmonious sink-source relation; while less tolerant species, e.g., Shaandan 902 and Yuyu 22, had shorter active grain-filling hours, lower maximum filling rate, lower mass increment and LAI under maximum grain-filling rate after silking, and significantly decreased source supply capacity. Low nitrogen stress increased the yield difference among the test varieties significantly.

[Spatial variability characteristics of soil organic carbon and nitrogen reveal typical alpine meadow degradation on Qinghai-Tibetan Plateau].

The principle of geo-statistics method was used to analyse the spatial heterogeneity of soil organic carbon and total nitrogen (0-10 cm) of alpine meadow of the Qinghai-Tibetan Plateau. The results show that the mean contents of soil organic carbon and total nitrogen at depth 0-10 cm are 11.45 g x kg(-1) and 1.02 g x kg(-1), 0.23 and 0.21 of co-variation coefficient, respectively. As mentioned above all factors reflect oligotrophic condition of soil fertility at this habitat. Organic carbon and entire nitrogen of soil random factor dissociation take up mutant proportion of general space heterogeneity being 44.7% and 49.9% respectively. Mutant dimension is 210.9 m and 200.1 m respectively. The soil organic carbon and the entire nitrogen show on the research territory vacates to oneself the factor to be bigger than machine the factor the different pattern. On space structure dissociation, from inherent attribute of soil, if space such as soil mineral substance, land form is certainly relevance, the factor and the artificial factor play role if the random factors that be trampled on to soil super crust arouses such as grazing and engineering construction is common, Medium memorial level affecting degree.

[Effects of planting date and density on population physiological indices of summer corn (Zea mays L.) in central Shaanxi irrigation area].

By using D-saturation optimum design and the methods of crop population physiology, this paper studied the effects of planting date and density on the population physiological indices of summer maize Shandan 8806 and its yield in central Shaanxi irrigation area. The results showed that in the period from 13 June to 22 July, the delay of planting had negative effects on grain yield, dry matter accumulation (DMA), maximum leaf area index (LAImax), net assimilation rate (NAR), leaf area duration (LAD) and crop growth rate (CGR), with larger effects on LAD and CGR than on LAImax and NAR. Within the range of 45 000-65 918 plants . hm (-2), planting density had positive effects on grain yield, DMA, LAImax, LAD and CGR but negative effect on NAR, with larger effects on LAImax, LAD and CGR than on NAR. The effects of planting date were more significant than those of planting density, and thus, Shandan 8806 should be sowed as early as possible. The regressive model based on the population physiological indices indicated that for the high yield of summer maize Shandan 8806, the optimum planting date was from 10 to 20 June, and the optimum planting density was from 57 767 to 71 706 plants . hm(-2).