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71.
J. Cabaret H. M. Baudet J. Devos J. Hubert J. Cortet C. Sauv 《Veterinary parasitology》1995,60(3-4):331-337
Multispecific resistance to benzimidazoles was studied in three selected farms. These farms had bred dairy goats for more than 15 years. The helminths were introduced with the goats at the establishment of the farms which afterwards remained isolated. Nematode resistance could then be related to their own management practices. Faecal egg count tests and egg hatch assays were performed to assess intensity of resistance. The generic (infective larvae in faecal cultures) and specific richness (adult worms) were assessed. The resistant species were Trichostrongylus colubriformis, Teladorsagia circumcincta, Haemonchus contortus and Oesophagostomum venulosum. Faecal egg count reduction tests and egg-hatch assays did not match exactly. Faecal larval counts after treatments gave a distorted picture of multispecific resistance: Haemonchus and Oesophagostomum were very largely over represented. The number of species found in the three farms was relatively low compared with other reports in goat farms of the area. This reduction of diversity might also be due in part to characteristics of breeding management and history (use of permanent pasture and introduction of goats at the establishment of farm). 相似文献
72.
This study presents the estimates of heritability for spondylosis deformans in the boxer based on 353 offspring from 24 randomly selected sires, each with at least three radiographically investigated offspring. The estimated heritability (h2) for maximum degree of osteophyte development was high, both when estimated by paternal half-sib correlation (0·42) and by the regression of offspring based on the parents (0·62). The heritability for the number of affected discs estimated by paternal half-sib correlation was also high (0·47). The estimate of heritability for the number of affected discs based on regression of offspring on the parents was lower at 0·13. All heritabilities had large standard errors. A positive phenotypic correlation between spondylosis deformans and hip dysplasia was observed. Assuming a significant portion of the correlation is genetic, this fact may permit selection against spondylosis deformans without negatively influencing the incidence of hip dysplasia. Since the incidence of spondylosis deformans is high even in young dogs, it should be possible to detect a large proportion of genetically predisposed animals by radiographic examination of the spine at one year of age; at the same time that dogs are presented for a routine test for hip dysplasia. 相似文献
73.
The anthelmintic efficacy of abamectin (avermectin B1) was evaluated against gastrointestinal nematodes, including Ostertagia ostertagi inhibited larvae and lungworm, in yearling crossbred beef heifers during late spring. The calves were grazed on contaminated pasture for 10 weeks and then held under conditions free of nematode infection for 3 weeks prior to allotment and treatment on 5 June. Thirteen calves were randomly assigned to two groups of six by restricted randomization on body weights; the extra lightest calf was assigned to the non-treated control group. Group 1 calves were treated with abamectin at 200 micrograms kg-1 body weight by s.c. injection and Group 2 calves were not treated; all were killed at 14 days after treatment. Ostertagia ostertagi was present in all controls; arithmetic mean numbers of adults, developing fourth stage larvae (L4) and inhibited EL4 were 7683, 605 and 36,102, respectively. Other nematode genera present in controls in sufficient numbers for the experiment were Haemonchus placei adults, Trichostrongylus axei adults, Cooperia spp. adults, Oesophagostomum radiatum adults, Bunostomum phlebotomum adults, Dictyocaulus viviparus adults and E5 (immature adults). Abamectin was highly effective (consistently greater than 99% efficacy and P less than 0.05) in removing all nematodes present in treated calves as represented in non-treated controls, including the primary target of Ostertagia ostertagi inhibited EL4. The lowest efficacy was 93.8%, against D. viviparus E5. 相似文献
74.
B. W. HERBERT 《Journal of fish diseases》1988,11(4):301-308
Abstract The microsporidian parasite Thelohania sp. was present in a population of Cherax quadriearinatus in the Mitchell River, north Queensland. An infection rate of 7--8% was recorded for the population sampled. Cohabitation, passage of spores through fish, ingestion of spores and injection of blood from an infected individual failed to elicit infection in laboratory held animals. Injection of spores elicited a host responseconsisting of encapsulation and melanization of spores. Further studies are necessary to clarify the taxonomic position and mode of transmission of this parasite. 相似文献
75.
S. Leibovitch B. L. Ma Wanga E. Maloba D. L. Smith 《Journal of Agronomy and Crop Science》1992,169(3):209-215
Aspects of intensive management practices such as high-yielding cultivars, narrow-row spacings and fungicide treatments could potentially increase cereal yields in regions with a short crop-growing season and occasionally dry and hot weather. A field experiment was carried out at McGill University, Canada for three years (1987 to 1989) to test the effects of triadimefon (1-[4-chlorophenoxy]-3,3-dimethyl-1-[1H-1,2,4-triazol-1-yl]-2-butanone, or Bayleton, a trade name) fungicide (0 vs. 140 g a.i. ha−1 ) and row spacing (10 vs. 20 cm) on the yield components, yield and other agronomic traits (spike emergence, days to maturity, leaf disease and plant height) of spring barley ( Hordeum vulgare L.) cv. Cadette, Laurier and Leger. A cultivar by row spacing interaction resulted in a 11 to 13.5 % increase in grain yield due to narrow rows for Laurier in two out of the three years and up to 16 % for Leger in one year. Over the three years grain yields were on average increased 6 to 12 % due to use of the narrower row spacing. Fungicide application to barley at the early heading stage effectively controlled leaf diseases without influence on yield components or grain yield. Our results indicate that some components of intensive management such as narrow row spacing can be applicable in regions with a short crop-growing season. 相似文献
76.
The results of cerebrospinal fluid (CSF) cytology of 9 dogs with brain tumors and 50 dogs with spinal cord compression are discussed. Of the 50 dogs with spinal cord compression, disc protrusion was diagnosed in 31, myelomalacia in 7, discospondylitis in 3 and spinal cord tumors in 9 dogs. In 4 of 9 dogs with brain tumors, tumor cells could be found by the sedimentation apparatus of K?lmel. Pleocytosis existed in 6 patients. In about 70% (29 of 41) of cases with disc protrusion, more than 200 cells could be evaluated in the CSF sediment, consisting mostly of transformed lymphocytes and activated monocytes. As the neurologic deficits increased, the amount of cells and especially cell complexes increased. This was especially evident in cases with myelomalacia of the spinal cord. Only in cases with discospondylitis or spinal cord neoplasia was the CSF cytology unchanged. 相似文献
77.
Abstract – Foraging juvenile fish with relatively high food demands are usually vulnerable to various aquatic and avian predators. To compromise between foraging and antipredator activity, they need exact and reliable information about current predation risk. Among direct predator-induced cues, visual and olfactory signals are considered to be most important. Food intake rates and prey-size selectivity of laboratory-reared, naive young-of-the-year (YOY) perch, Perca fluviatilis , were studied in experiments with Daphnia magna of two size classes: 2.8 and 1.3 mm as prey and northern pike, Esox lucius , as predator. Neither total intake rate nor prey-size selectivity was modified by predator kairomones alone (water from an aquarium with a pike was pumped into the test aquaria) under daylight conditions. Visual presentation of pike reduced total food intake by perch. This effect was significantly more pronounced (synergistic) when visual and olfactory cues were presented simultaneously to foraging perch. Moreover, the combination of cues caused a significant shift in prey-size selection, expressed as a reduced proportion of large prey in the diet. Our observations demonstrate that predator-induced olfactory cues alone are less important modifiers of the feeding behaviour of naive YOY perch than visual cues under daylight conditions. However, pike odour acts as a modulatory stimulus enhancing the effects of visual cues, which trigger an innate response in perch. 相似文献
78.
79.
80.
Louis R. D'Abramo Cortney L. Ohs Kathleen C. E. Elgarico 《Journal of the World Aquaculture Society》2006,37(3):307-312
The effects of addition of substrate consisting of plastic mesh fencing to experimental earthen ponds were evaluated for the culture of the red swamp crawfish, Procambarus clarkii, without planted forage. Mean daily yield (kg/ha/d), number of crawfish harvested (number/ha/d), and mean individual harvest weight were compared for ponds with and without substrate during a 2‐yr period. The surface area of added substrate was equivalent to 50% of the bottom surface area of the pond. Mean daily yield in the ponds containing substrate, based on a comparison with that of the previous year, increased by 80.2% and was principally attributed to a 66.7% increase in the number of crawfish harvested. Comparative values for the ponds without substrate were ?13.1 and ?11.7%. For the second year, the treatment‐dependent response was consistent. Mean daily yield for the substrate ponds increased by 48.8% compared to 15.0% for the ponds lacking substrate. The primary benefit of the substrate appears to be provision of refuge and three‐dimensional distribution of crawfish in the pond, thereby reducing the incidence of cannibalism and increasing the total number of crawfish harvested per hectare per day. The benefit of the substrate in a commercial production setting must be weighed against its cost and longevity as well as the conditions of the particular management scenario into which it may be incorporated. 相似文献