Corn‐expressed dietary phytase augments vertebral and scale mineral content in juvenile rainbow trout (Oncorhynchus mykiss)     

S.W. FOX  S.J. DAVIES 《Aquaculture Nutrition》2011,17(4):e840-e852

Fishmeal (FM) is increasingly being replaced by plant proteins which are a relatively poor phosphorous source for mineralized tissues. To promote P availability plant‐based feedstuffs are supplemented with exogenous phytase. However, the effect of phytase on skeletal development in juvenile rainbow trout (Oncorhynchus mykiss) which have distinct mineral requirements is poorly understood. To address this juvenile trout were fed FM diet, a replacement feed (soybean meal, SBM) in which 50% (460 g kg^?1) of crude protein (from FM) was substituted with soybean‐meal or SBM supplemented with microbial or corn‐expressed phytase. Vertebral and scale morphology, remodelling and mineralization were then assessed by histomorphometric and colorimetric assays. Body weight and SGR of trout fed SBM was lower than FM fed fish with no improvement noted with any phytase supplement. Vertebral mineral content and autocentrum morphology were similar in trout fed SBM or FM and supplementation with microbial‐phytase did not enhance these parameters at any concentration. However, scale and vertebral mineral content were significantly enhanced in trout fed SBM supplemented with corn‐expressed phytase 1500 FTU kg^?1 (vertebral phosphorus P = 0.014, Ca P = 0.026; scale phosphorus P = 0.012). Thus, SBM feeds supplemented with corn‐expressed phytase could help reduce FM usage and generate a more robust skeleton less prone to deformity.  相似文献   

U/Pb zircon geochronology and tempo of the end-permian mass extinction     

SA Bowring  DH Erwin  Jin M W Martin YG  K Davidek  W Wang 《Science (New York, N.Y.)》1998,280(5366):1039-1045

The mass extinction at the end of the Permian was the most profound in the history of life. Fundamental to understanding its cause is determining the tempo and duration of the extinction. Uranium/lead zircon data from Late Permian and Early Triassic rocks from south China place the Permian-Triassic boundary at 251.4 +/- 0.3 million years ago. Biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the Changhsingian pulse of the end-Permian extinction, corresponding to the disappearance of about 85 percent of marine species, lasted less than 1 million years. At Meishan, a negative excursion in delta13C at the boundary had a duration of 165,000 years or less, suggesting a catastrophic addition of light carbon.  相似文献   

Silviculture of the Spruces in West Scotland     

DAVIES  E. J. M. 《Forestry》1967,40(1):37-46

An account of the silviculture of Norway and Sitka spruce (Piceaabies and P. sitchensis) practiced in the West (Scotland) Conservancyof the Forestry Commission in the past 50 years. Present methodsare summarized and future developments forecast. A more intensiveform of silviculture is advocated for Sitka spruce.  相似文献   

Improving the upstream passage of two galaxiid fish species through a pipe culvert     

J. I. MACDONALD  & P. E. DAVIES 《Fisheries Management and Ecology》2007,14(3):221-230

Abstract  Movement between habitats in river fish assemblages is often restricted by instream structures such as culverts. The ability of diadromous common jollytail, Galaxias maculatus (Jenyns), and spotted galaxias, Galaxias truttaceus (Val.), to pass upstream through an in situ pipe culvert modified through the installation of baffles was assessed. Spoiler baffles (100 × 70 × 28 or 56 mm) were installed in three spatial arrangements along a 5.5-m section of the pipe, and individual fish passage assessed at three flow velocities (0.35, 0.70 and 1.0 m s⁻¹). Common jollytails (43–169 mm fork length, FL) were 10 times more successful in passing when baffles were present than under control conditions (baffles absent). Baffle size did not influence success, which increased with the spatial complexity of the baffle arrangement. Across all velocities, common jollytails (46–132 mm FL) and spotted galaxias (55–190 mm FL) were, respectively, 86 and 73 times more successful with the most complex baffle arrangement (overall 80% success) compared with control conditions (overall 13.5% success). Success for both species decreased at higher velocities under control conditions; however, when baffles were present, this trend persisted only for common jollytails. Installing small spoiler baffles may provide a simple, cost-effective solution to passage problems at culverts.  相似文献   

Serial Transrectal Ultrasonography for Monitoring the Reproductive Activity of the Asiatic Black Bear (Ursus thibetanus ussuricus)          下载免费PDF全文

HG Kang  DH Jeong  JJ Yang  BK Lee  JY Kong  JW Lee  IH Kim 《Reproduction in domestic animals》2015,50(1):149-158

This study evaluated the structural changes in the reproductive tract of Asiatic black bears using serial transrectal ultrasonography. In addition, the ultrasonographic observations were compared with the results of vaginal cytology and hormonal analyses. The collection of blood for hormonal analysis, vaginal cytology and transrectal ultrasonography was performed in two bears (Bears 1 and 2) from June 2011 to August 2013 without mating and in a third bear (Bear 3) from April to December 2012, allowing natural mating. Serial ultrasonographic observations showed cyclic changes in ovarian structures (e.g. emergence of small follicles, growth and ovulation of dominant follicles and corpus luteum (CL) formation) during the reproductive cycles of the three bears. The diameter of the uterine horns remained similar throughout the reproductive cycle in Bears 1 and 2, and it remained similar from April until October, but an enlargement containing foetuses was observed in Bear 3 in December. The ultrasonographic observations were consistent with the data obtained through vaginal cytology and progesterone analysis during the reproductive cycle. An average of 4.0 (±0.4) dominant follicles was observed during the oestrous stage (May‐August), during which the superficial cells accounted for >90% of the total vaginal cells. In addition, the detection of an average of 2.6 (±0.2) CL was associated with increased plasma progesterone concentrations (3.0 ± 0.4 ng/ml) between June and December (near hibernation). In conclusion, serial transrectal ultrasonography demonstrated yearly oestrous (ovulation) cycles via follicular dynamics and CL formation on ovaries, accordingly with vaginal cytology and hormonal level in the Asiatic black bear.  相似文献   

Trace elements in surface soils from the mineralized area of Madison County, Missouri, U.S.A.     

B. E. DAVIES  B. G. WIXSON 《European Journal of Soil Science》1985,36(4):551-570

Duplicate, bulked surface soil samples, from sites 10m apart, were collected at 97 locations 1000 m apart on a regular grid measuring 8x11 km. Data were obtained for Ag, Ba, Be, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, V and Zn. One field sample was a good predictor of its nearby duplicate for Co, Cu, Ni and Pb, satisfactory for Ba, Be, Cr, Mn and Zn, but poorer for Cr, Li and V. Maps of the variation in precision of the field samples did not reveal any association between abandoned mine sites and high variability. The median coefficient of variation for trace elements in the field duplicates was between 8 and 19.5%. The duplicated field data were averaged to yield a mean soil metal concentration at each sample location. Concentrations of Ba, Be, Cr, Li, Sr and V were comparable with other published values for similar soils in Missouri. Concentrations of Co, Cu, Mn, Ni, Pb and Zn were higher which was explained by pollution from mining activities. A graphical technique was used to calculate background levels for metals in the second group. Samples of forest litter were collected at 12 locations: Ag, Ba, Cd, Mn, Sr and Zn concentrations were higher in the litter whereas Li and V concentrations were higher in the subjacent mineral soil. Computer isoline maps of the distribution of elements revealed an association between areas of high soil Cu, Co, Ni, Pb and Zn and abandoned mines or mineralized rocks.  相似文献   

Fate of fertilizer nitrogen applied to grassland. I. Field leaching results     

D. BARRACLOUGH  M. J. HYDEN  G. P. DAVIES 《European Journal of Soil Science》1983,34(3):483-497

Results are presented from a 3 year investigation into nitrate leaching from isolated 0.4 ha grassland plots fertilized with 250, 500 and 900 kg N ha^?1 a^?1. Cumulative nitrate leaching over the 3 years was equivalent to 1.5%, 5.4% and 16.7% of the fertilizer applied at 250, 500 and 900 kg N ha^?1 rates respectively. Over a whole drainage season, mean nitrate leachate concentrations at 250 kg N ha^?1 did not exceed 4 mgl^?1, although maximum values of 13.3 mgl^?1 were observed. In contrast, at 900 kg N ha^?1, the mean nitrate leachate concentration in two of the years exceeded 90 mgl^?1. Mineral nitrogen balances constructed for the 1979 growing season indicated that leaching at 250 kg N ha^?1 was low because net mineralization of soil organic nitrogen was small, and crop nitrogen uptake almost balanced fertilizer application. Although the pattern of nitrate leaching suggested that by-passing occurred in the movement of water down the soil profile, it was not possible to confirm this using simulation models of leaching. Possible reasons for this, including the occurrence of rapid water flow down gravitationally drained macropores, are discussed.  相似文献   

A SIMPLE AND INEXPENSIVE APPARATUS FOR AUTOMATICALLY CONTROLLING SOLUTION FLOW RATES THROUGH SOIL COLUMNS     

I. J. GRAHAM-BRYCE  R. I. DAVIES  A. A. H. AL-RAWI 《European Journal of Soil Science》1967,18(1):39-41

Accurate control of rate of flow of solution through soil columns is important in laboratory studies of leaching, but is difficult to achieve because of fluctuations in permeability. A simple and inexpensive method of automatically maintaining a constant flow-rate through several columns simultaneously is described. The apparatus comprises (i) a rotating delivery system which distributes the leaching solution equally to eight compartments, (ii) a system for automatically regulating the flow through each column to keep pace with the solution delivered, and (iii) an automatic fraction-collector to collect the effluent from the columns. Using this apparatus the standard deviation of the volumes delivered to the eight individual columns was less than 2 per cent of the mean, provided the flow rate was faster than 10 ml/h.  相似文献   

Comparative sheep production and herbage characteristics on four perennial ryegrass varieties in the uplands     

D. A. DAVIES 《Grass and Forage Science》1987,42(3):233-239

Ewe and lamb performance, herbage production and feed quality components on four late-flowering perennial ryegrass ( Lolium perenne L.) varieties were assessed under a fixed stocking management at an upland site (305 m OD) in mid-Wales. Averaged over four years (1981–84) there was no significant difference (P>0·05) between Aberystwyth S23, Aberystwyth Ajax, Perma and Meltra (tetraploid) in ewe and iamb liveweight gains. There were, however, considerable differences between varieties during individual years and their relative ranking also changed substantially over the four years. Lamb production on Perma was 22% more than on S23 in the first year but by the fourth year it was 21 % less than on the latter variety.
Differences between varieties were observed in herbage production. Net herbage accumulation was 15% more on Meltra than on Ajax whilst the calculated quantity of OM consumed was 19% higher from Meltra than from both Ajax and S23. Net animal liveweight gains were positively correlated with herbage production (r = 0·95, P < 0·05) and DOM consumed (r=0·96. P<0·05).  相似文献   

Comparison of the relative performance of perennial ryegrass varieties under upland and lowland conditions     

D. A. DAVIES  E. L. JONES  T. E. H. MORGAN 《Grass and Forage Science》1985,40(3):323-330

Productivity, seasonal growth and persistence of 10 perennial ryegrass ( Lolium perenne L.) varieties were assessed al an upland (305 m) and lowland (30 m) site in mid-Wales. Averaged over 3 harvest years (1979–81), mean dry matter (DM) production at 8.8 t ha⁻¹ was 22% lower in the upland environment, with spring (April and May) growth showing greatest contrast varying from only 6% of that in the lowland in 1979, after a severe winter, to 113% in 1981.
Relative ranking of varieties differed considerably between the two environments and no correlation was found between DM production at the two sites ( r = 0.5945). Early heading varieties performed better in the spring than late types at the upland site. A comparison of the results with those published from official variety testing trials gave a positive relationship under lowland conditions ( r = 0.7162*) but no correlation with those from the upland centre ( r = 0.1969).
The findings of the study show that relative productivity of varieties, but not persistency, differs between upland and lowland environments.  相似文献