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排序方式: 共有110条查询结果,搜索用时 31 毫秒
1.
Abstract. In field and laboratory experiments the conditioner‘Agri-SC’has shown improvements in the structure of loamy sand soils in east Shropshire, UK. It resulted in statistically significant decreases in soil bulk density values and increases in soil porosity and aggregate stability. Further experiments are in progress on both loamy sand and silt loam soils. 相似文献
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An economically based evaluation index for perennial and short‐term ryegrasses in New Zealand dairy farm systems
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D. F. Chapman J. R. Bryant M. E. Olayemi G. R. Edwards B. S. Thorrold W. H. McMillan G. A. Kerr G. Judson T. Cookson A. Moorhead M. Norriss 《Grass and Forage Science》2017,72(1):1-21
Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha?1 to $863 ha?1 year?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha?1 year?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha?1 year?1 (depending on region) operating profit on dairy farms since the mid‐1960s. 相似文献
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Pearson GR Bazeley KJ Jones JR Gunning RF Green MJ Cookson A Woodward MJ 《The Veterinary record》1999,145(13):370-373
Escherichia coli O26:K60, with genetic attributes consistent with a potentially human enterohaemorrhagic E. coli was isolated from the faeces of an eight-month-old heifer with dysentery. Attaching and effacing lesions were identified in the colon of a similarly affected heifer examined postmortem, and shown to be associated with E. coli O26 by specific immunolabelling. 相似文献
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L. J. Cookson 《Wood Science and Technology》1987,21(1):11-25
Summary The termites Nasutitermes exitiosus (Hill), Coptotermes acinaciformis (Froggatt), and Mastotermes darwiniensis Froggatt were examined for their ability to degrade lignin. Several 14C-(lignin)-lignocelluloses labelled in the 3 side chain position were prepared by infusing plant stems for seven days with the lignin precursor, 14C-cinnamic acid. Based on acid and alkali solubilites, the lignin precursor was more deeply incorporated into the lignin polymer than usually reported for 14C-(lignin)-lignocellulose preparations. N. exitiosus was able to degrade a 14C-(U-ring)-synthetic lignin (5% breakdown) and the lignin component of certain hardwood 14C-(lignin)-lignocelluloses (about 4–6.5% breakdown), but not the lignin component of softwood 14C-(lignin)-lignocellulose. Both C. acinaciformis and M. darwiniensis were less able to degrade any of the 14C-lignins than N. exitiosus. The difference may be due to their possessing different types of gut symbionts. Most of the degradation by N. exitiosus took place during the first week of the 14 day bioassays. Very low amounts (0.03–0.21%) were degraded in the faeces.The author wishes to thank Dr. J. R. J. French and Dr. G. Ettershank for their helpful advice during the work, Dr. T. K. Kirk for his generous gift of synthetic lignin, and J. W. Creffield for collecting the lower termites. E. Longmore and P. J. Pahl provided advice on statistical analysis 相似文献
6.
JI Yun HJ Park MH Park MS Kim JH Choi E Lee SP Gong JM Lim ST Lee 《Reproduction in domestic animals》2014,49(5):705-710
Recently, isolation and in vitro culture of putative spermatogonial stem cells (SSCs) in the domestic cat have been conducted. However, the cellular niche conditions that facilitate the establishment and long‐term maintenance of feline SSCs (FSSCs) have not been described. Therefore, we investigated the type of feeder cells used to stimulate colony formation and growth of FSSCs among the various factors in the FSSC niche. Spermatogonial stem cells isolated from feline testes were cultured on mitotically inactivated testicular stromal cells (TSCs) derived from cats, dogs and mice, and mouse embryonic fibroblasts (MEFs). The formation and growth of colonies derived from SSCs cultured on each type of feeder cell were identified at passage 0, and the morphology, alkaline phosphatase (AP) activity and expression of SSC‐specific genes in surviving colonies were investigated at passage 4. Among these diverse feeder cells, TSCs from cat showed the greatest colony formation, growth and maintenance of FSSCs, and SSC colonies cultured by passage 4 showed a typical dome‐shaped morphology, AP activity and expression of SSC‐specific genes (NANOG, OCT4, SOX2 and CD9). Accordingly, these results demonstrate that feline TSCs could be used as feeder cells to support the establishment and maintenance of SSCs from domestic cats. 相似文献
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