A cluster analysis of the stratigraphic distribution of all Ordovician trilobite families, based on a comprehensive taxonomic database, identified two major faunas with disjunct temporal diversity trends. The Ibex Fauna behaved as a cohort, declining through the Ordovician and disappearing at the end-Ordovician mass extinction. In contrast, the Whiterock Fauna radiated rapidly during the Middle Ordovician and gave rise to all post-Ordovician trilobite diversity. Its pattern of diversification matches that of the Paleozoic Evolutionary Fauna; hence, trilobites were active participants in the great Ordovician radiations. Extinction patterns at the end of the Ordovician are related to clade size: Surviving trilobite families show higher genus diversity than extinguished families. 相似文献
Summary The relative efficacy of 6 shower dip chemicals most frequently used for the treatment of sheep lice (Bovicola ovis) in Western Australia was examined. Groups of 20 sheep infested with lice were treated with products containing either alphamethrin, cyhalothrin, diazinon or diazinon plus piperonyl butoxide and rotenone, formulated as emulsifiable concentrates, and with products containing either coumaphos or magnesium fluorosilicate, formulated as wettable powders. All treatments were applied through a shower dip (Sunbeam model SSD). Inspections for lice were conducted until 9 months after dipping. No lice were found on sheep treated with the 4 emulsifiable concentrate products. In contrast, treatment with the wettable powders, which contained either coumaphos or magnesium fluorosilicate as the active ingredient, did not eradicate the lice infestations. The degree to which the fleece was wetted was assessed 20 minutes after dipping and showed that the wettable powder dips penetrated the fleece less than the emulsifiable concentrate dips. Less fluid was retained by wool staples in an in-vitro test when dip wash was made with the wettable powders. It was concluded that the degree of wetting attained at dipping was an important factor in achieving eradication of sheep lice. 相似文献
This study investigated the effects on embryo growth and survival rate of feeding heavily‐fertilised spring grass, containing high levels of quickly‐degradable nitrogen, to pregnant cows. Forty‐eight lactating Holstein cows between 2 and 8 weeks pregnant were turned‐out, after a one‐week transition period onto high‐ or low‐nitrate pasture and fed a high‐ or low‐concentrate supplement. Cows grazing the High nitrate pasture had significantly higher milk and plasma urea concentrations than cows grazing the Control pasture, while cows which were fed less concentrate had a notably higher plasma ammonia. However, there was no evidence that an increased quickly‐degradable nitrogen (QDN) intake from pasture affected embryo survival or growth from 20 days onwards. This suggests that the impact of turnout on fertility mainly affects ovulation, fertilisation and/or the early embryo. 相似文献
Conventional somatic cell nuclear transfer (SCNT) technique of in vitro production of cloned embryos involves use of costly and complicated micromanipulators. Handmade cloning (HMC) technique has been applied as efficient and cost‐effective alternative in many livestock species. The aim of the present study was to compare the efficiency of in vitro production and in vitro development of cloned sheep embryos by the two techniques. Cloned embryos were produced by conventional SCNT using micromanipulator apparatus and by HMC technique. Enucleation efficiency and efficiency of fusion with somatic cell (nucleus donor) were compared. Cleavage percentage was observed on day 2 of in vitro culture (IVC), and morula and blastocyst percentages were calculated on day 7 of IVC. Higher enucleation efficiency (96.98 ± 1.01 vs. 93.62 ± 1.03; p > .05) as well as fusion efficiency was obtained with HMC technique than with conventional SCNT (96.26 ± 1.34 vs. 92.63 ± 0.70, p < .05); 181 cloned sheep embryos were produced in vitro by conventional SCNT and 92 by HMC. Cleavage percentage observed on day 2 of in vitro culture was higher in HMC than SCNT (66.92 ± 3.72 vs. 55.97 ± 2.5, respectively, p < .05). Morula percentage obtained was higher in SCNT than HMC (44.12 ± 2.93 vs. 30.43 ± 6.79, respectively, p < .05), whereas blastocyst percentage obtained by HMC was higher (12.46 ± 4.96) than SCNT (5.31 ± 2.25; p > .05). It was inferred that HMC technique provides a cost‐effective and efficient method of in vitro production of cloned sheep embryos with a comparatively simpler technique with a possibility of automation. Efficiency of cloned embryo production could be improved further by propagating and standardizing this technique. 相似文献
This study was carried out to examine the changes in plasma concentrations of the Ca‐binding antimicrobial proteins S100A7 and S100A8 during pregnancy in dairy cows. Holstein Friesian cows (n = 19) were inseminated with Holstein Friesian semen. Blood was collected at days 30, 60, 90, 120, 150, 180, 210, 240 and 270 after insemination. Plasma was used for measuring the concentrations of S100A7 and S100A8. Both S100A7 and S100A8 concentrations showed similar patterns during gestation; they increased during the midgestation, between days 90 and 180, and then declined before calving. The findings indicated that plasma concentrations of S100A7 and S100A8 did not change significantly during pregnancy in cows. Further studies are required to determine the roles of S100A7 and S100A8 in physiological function during pregnancy in dairy cows. 相似文献
AIMS: To investigate the effect of targeted resynchronisation of cows treated for non-observed oestrus before the planned start of mating (PSM), that were not detected in oestrus or pregnant 23 days after treatment (phantom cows), on the proportion pregnant at 42 days after PSM and the end of mating.
METHODS: Farm staff from eight herds in two regions of the South Island of New Zealand identified 1,819 cows not showing oestrus by 10 days before PSM. These cows were treated with intravaginal progesterone for 7 days, and I/M gonadorelin 10 days and 1 day before PSM. Three days before PSM they were injected with cloprostenol and equine chorionic gonadotrophin, with fixed time artificial insemination (FTAI) at PSM. By 23 days after PSM, 1,218 cows had not returned to oestrus. Of these, 161 cows confirmed not pregnant by transrectal ultrasonography were randomly assigned to no treatment (control group; n=74) or were resynchronised 25 days after PSM using the same treatment programme as above, with FTAI 35 days after PSM (n=87). All cows that returned to oestrus were artificially inseminated until 42 days after PSM, when natural mating was used. All cows were examined using transrectal ultrasonography 80 to 90 days after PSM to confirm conception dates.
RESULTS: Of the 1,819 anoestrous cows treated before PSM, 526 (29 (95% CI=23.1–34.0)%) had not been observed in oestrus by 23 days after PSM and had not conceived, so were diagnosed as phantoms cows. For resynchronised cows, 42/87 (48 (95% CI=37.8–58.8)%) were pregnant by 42 days after PSM compared to 21/74 (28 (95% CI=18.1–38.7)%) control cows (p=0.009). At the end of mating 58/87 (67 (95% CI=56.6–76.7)%) cows in the resynchronised group were pregnant and 46/74 (62 (95% CI=50.9–73.2)%) in the control group (p=0.554). The hazard of conception from 21 to 42 days after PSM was 1.9 (95% CI=1.07–3.12) times greater for resynchronised than control cows (p=0.026).
CONCLUSION: In cows not observed in oestrus and treated before PSM, resynchronisation increased the proportion pregnant by 42 days after PSM.
CLINICAL RELEVANCE: The benefit of resynchronisation depends on the number of anoestrous cows before PSM and the number of phantom cows after PSM. However at the herd-level it is likely that providing advice to reduce the known risk factors for cows not being observed in oestrus before the PSM may well be more cost effective than identifying and treating a sub-population of phantom cows. 相似文献
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