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1.
M. J. GIBB 《Grass and Forage Science》1991,46(3):339-342
A mosaic of short, frequently grazed areas and tall, infrequently grazed areas is a characteristic of swards continuously stocked with cattle. Inclined point quadrat measurements were used to compare sward structure on the frequently and infrequently grazed areas in an experiment on mixed grass/clover swards with beef cattle, in which the swards were maintained at overall mean rising-plate target heights of 3·0, 5·5 or 7·0 cm. The results demonstrate large within treatment differences in the vertical distribution of plant parts between the frequently and infrequently grazed areas, and smaller differences within these areas between treatments. The consequences of these observations and the need for greater effort in recording the detailed structure within these areas in grazing experiments is noted. 相似文献
2.
MICHAEL GIBB 《Journal of veterinary pharmacology and therapeutics》1988,11(2):227-229
DISEASES OF THE THORAX – RADIOGRAPHIC DIAGNOSIS. Peter F. Suter, Juan A. Gomez
RADIOLOGY OF SKELETAL DISEASE – PRINCIPLES OF DIAGNOSIS IN THE DOG. J. P. Morgan 相似文献
RADIOLOGY OF SKELETAL DISEASE – PRINCIPLES OF DIAGNOSIS IN THE DOG. J. P. Morgan 相似文献
3.
Herbage height was measured in ryegrass/white clover ( Lolium perenne/Trifolium repens ) swards grazed by cattle using the rising plate meter or the sward stick. Ordinary single normal and double normal distributions were fitted to the data obtained. After the first 6 weeks of continuous grazing the double normal distributions fitted data for the taller swards better than the single normal distribution did, but for a short sward there was no improvement. There was no improvement due to the use of the double normal distribution with data for swards grazed by sheep. 相似文献
4.
Zamira Golubenko Alik Akhunov Nigora Khashimova Yuliana Beresneva Elmira Mustakimova Fazil Ibragimov Nigora Abdurashidova Robert Stipanovic 《Phytoparasitica》2007,35(4):401-413
The pathogen-induced biosynthesis of peroxidase (PO) in resistant and susceptible wild species of Malvaceae was studied. Specifically,Hibiscus trionum was found to be resistant to the wilt pathogenVerticillium dahliae, andAlthea armeniaca was susceptible. After inoculation withV. dahliae, PO activity increased more rapidly in the resistant plant: increased activity inH. trionum was noted within 1 h after inoculation, remained high for 5 h, and decreased after 18 h. After 5 days, the levels did not
differ from the control. In the susceptibleA. armeniaca, PO activity did not differ statistically from the control even after 18 h, but was significantly higher after 5 days. Electrophoretic
analysis of inoculated tissue extracts showed the occurrence of two new isoforms inh. trionum after inoculation; new isoforms did not occur inA. armeniaca. A chitin affinity chromatography column showed the presence of a chitin-binding peroxidase isozyme in healthyH. trionum that increased dramatically after inoculation. Two chitin-binding peroxidase isozymes were observed in healthyA. armeniaca: one (R
f
0.26) did not increase and the other (R
f
0.89) evinced only a small increase after inoculation. 相似文献
5.
Lactation performance of spring-calving dairy cows grazing mixed perennial ryegrass/white clover swards of differing composition and height 总被引：1，自引：0，他引：1
An experiment was designed to examine the changes in clover content of three mixed perennial ryegrass/white cover swards of differing initial clover contents subjected to different grazing height management regimes and their effect on lactation performance of 48 Friesian dairy cows and heifers. Two paddocks were established for each treatment and grazed on alternate days. Treatments T17 and Tl3 consisted of swards with initial clover contents of 0·17 and 0·13 of the dry matter (DM) mass, respectively, grazed to maintain compressed sward heights of 6 cm throughout the season. A third treatment, SI5, consisted of a sward with an initial clover content of 0·15 grazed to maintain a compressed sward height of 4·5 cm for the first 78 days of the grazing season (period 1). Throughout period 1, half the animals on each treatment each received 4 kg of a concentrate supplement daily, while the others remained unsupplemented. From days 79 to 90, the cattle on treatment S15 grazed a similar sward, while the compressed sward height of the S15 paddocks was allowed to increase to 6 cm before re introduction of the animals. The three swards were then grazed for a further 47 days (period 2) before the animals were housed and milk yield recorded for a further 63 days (period 3). While sward T17 showed little change in clover content over the first 29 days of grazing, remaining at just below 0·18 of DM mass, swards T13 and S15 showed a marked decline in clover content to 0·05 and 0·07 of DM mass respectively. However, by the end of period 1 the clover content of all three swards had increased markedly (0·25, 0·15 and 0·15 of DM mass respectively). By the end of period 2, clover proportions were slightly higher than initial values (0·19. 0·15 and 0·15 of DM mass for treatments T17, T13 and S15, respectively). Owing to the relatively small differences in clover content of swards TI7 and T13, there were no significant effects of these two treatments on milk yield or composition in any period. Supplementation had no effect on milk composition and had little effect on milk yield, except when sward height was maintained at 4·5 cm. There was no carryover effect of supplementation on milk yield or composition in periods 2 or 3. 相似文献
6.
Spermatozoa are vulnerable to oxidative attack because they contain an abundance of polyunsaturated fatty acids that are susceptible to lipid peroxidation. In addition, functionally important proteins and DNA are also subject to oxidative modification and adduction by aldehydes, such as 4-hydroxynonenal (4HNE), generated as a consequence of the peroxidative process. The proteins adducted by 4HNE include elements of the mitochondrial electron transport chain, such as succinic acid dehydrogenase. The net result of such electrophilic attack is to stimulate generation of mitochondrial reactive oxygen species (ROS) in a self-perpetuating lipid peroxidation–ROS generation cycle that ultimately triggers the intrinsic apoptotic pathway, leading to a rapid loss of motility and cell death. A major point of difference between apoptosis in spermatozoa and somatic cells is that in the former, nuclear DNA is located in a compartment (the head) separate from the mitochondria and most of the cytoplasm (the midpiece). As a result, nucleases activated and released in the midpiece during apoptosis cannot gain access to the DNA in the sperm head in order to cleave the DNA. However, the ROS generated during apoptosis can readily gain access to the sperm nucleus and generate oxidative base adducts, typically 8-hydroxy, 2′-deoxyguanosine (8OHdG), which are converted into abasic sites by 8-oxoguanine glycosylase (OGG1), the only enzyme of the base excision repair pathway possessed by spermatozoa. These abasic sites subsequently become the foci of DNA fragmentation. Because defective sperm function and DNA damage are frequently associated with oxidative stress, there is a great deal of interest in the use of antioxidants in a therapeutic context. This presentation examines the fundamental relationships between oxidative stress and sperm function and considers the implications of recent findings for the management of sperm function and fertility in stallions. 相似文献
7.
Herbage heights were measured with a rising plate meter in mixed perennial ryegrass/white clover ( Lolium perenne/Trifolium repens ) swards maintained under five different systems of management. Double normal distributions fitted to the height frequencies were used to interpret changes over the grazing season in the mean heights of the shorter 'frequently' and the taller 'infrequently' grazed components of the sward, the variability of height within the two components, and the proportions of the two components in the sward. An attempt was also made to demonstrate that the overlap of these components, implicit in fitting double normal distributions, is a true reflection of the height distributions of frequently and infrequently grazed areas of the sward, and that the fitting of such a distribution provides a useful estimate of the proportion of a sward which is infrequently grazed. 相似文献
8.
During an experiment in which the height of mixed perennial ryegrass/while clover swards was maintained throughout the season at 3 or 7 cm (S and T, respectively), or were maintained al those heights until 30 June then changed (ST and TS), a limited study was made of the effects on the population densities and masses of the two species. During the earlier part of the season the short swards (S and ST) developed higher tiller and stolon growing point (sgp) densities, but with a reduced mass of ryegrass, principally of the pseudostem fraction, than the tail swards (T and TS). Thiere was little effect of sward height on the mass of clover. Whilst there was a general tendency for tiller and sgp densities to increase during the latter part of the season, tiller density increased greatly where sward height was reduced (TS) and both tiller and sgp densities were reduced where sward height was allowed to increase (ST). Changing sward height, whilst limiting the accumulation of dead grass material (TS), allowed grass leaf and dead masses to increase (ST), and adversely affected the increase in the clover component, principally of stolon material, in both ST and TS. 相似文献
9.
应用危险确认模型评估土地管理的可持续发展 总被引：4，自引：1，他引：4
New Zealand is highly dependent on its soil resource for continued agricultural production.To avoid depleting this resource,there is a need to identify soils and associated land management practices where there is a risk of soil degradation.Environmental integraity and ecosystem services also need to be maintoained.Accordingly,to ensure sustainable production,The on -and off-site environmental impacts of aldn management need to be identified and managed.We developed a structural vulnerability index for New Zealand soils.This index ranks solis according to their inherent susceptibility to physical degradation when used for agricultural (pasture,forestry and cropping) Purposes.We also developed a rule-based model to assess soil sompaction vulnerability by characterising the combined effects of resistance and resilience,Other soil attributes have been approatised using seven chemical,physical and biological indicators of soil quality.These indicators have been applied in a nation -wide project involving data collection from over 500 sites for a range of land uses.These soil quality data can be interpreted via the World Wide Web -through the in teractive decisionsupport tool SINDI,The land-use impact model is a framework to assess agricultural land management and environmental sustainability,and may be applied to land units at any scale.Using land resource data and information the model explicitly identifies hazards to land productivity and environmental integrity,It utilises qualitative expert and local knowledge and quantitative model-based evaluations to assess the potential environmental impacts of land-management pratices.The model is linked to a geographic information system(GIS),allowing model outputs.such at the environmental impacts of site-specific best management practices,to be identified in a spatially explicit manner,The model has been tested in New Zealand in an area of pastoral land use.Advantages of this risk identification model include:utilising current knowledege of the causes and effects of land-management practices on soil degradation;linking land management practice to both on-and off-site environmental consequences;identifying important gaps in local knowledge,and providing spatially explicit information on the environmental impact of land-management practices. 相似文献
10.
Charley-Lea POLLARD Ashleigh YOUNAN Aleona SWEGEN Zamira GIBB Christopher G. GRUPEN 《The Journal of reproduction and development》2022,68(3):216
Treatments that elevate NAD+ levels have been found to improve oocyte quality in mice, cattle, and pigs, suggesting that NAD+ is vital during oocyte maturation. This study aimed to examine the influence of different NAD+ biosynthetic pathways on oocyte quality by inhibiting key enzymes. Porcine oocytes from small antral follicles were matured for 44 h in a defined maturation system supplemented with 2-hydroxynicotinic acid [2-HNA, nicotinic acid phosphoribosyltransferase (NAPRT) inhibitor], FK866 [nicotinamide phosphoribosyltransferase (NAMPT) inhibitor], or gallotannin [nicotinamide mononucleotide adenylyltransferase (NMNAT) inhibitor] and their respective NAD+ pathway modulators (nicotinic acid, nicotinamide, and nicotinamide mononucleotide, respectively). Cumulus expansion was assessed after 22 h of maturation. At 44 h, maturation rates were determined and mature oocytes were fixed and stained to assess spindle formation. Each enzyme inhibitor reduced oocyte maturation rate and adversely affected spindle formation, indicating that NAD+ is required for meiotic spindle assembly. Furthermore, NAMPT and NMNAT inhibition reduced cumulus expansion, whereas NAPRT inhibition affected chromosomal segregation. Treating oocytes with gallotannin and nicotinamide mononucleotide together showed improvements in spindle width, while treating oocytes with 2-HNA and nicotinic acid combined showed an improvement in both spindle length and width. These results indicate that the salvage pathway plays a vital role in promoting oocyte meiotic progression, while the Preiss-Handler pathway is essential for spindle assembly. 相似文献