Exsheathment of Ostertagia ostertagi infective larvae following exposure to bovine rumen contents derived from low and high roughage diets

The objective of this study was to characterize the exsheathment kinetics of Ostertagia ostertagi infective larvae (L3) following in vivo exposure to bovine rumen contents derived from low and high roughage diets. O. ostertagi L3 were placed in disposable dialysis bags and incubated for various time points between 0 and 360 min in the rumen of a fistulated steer maintained on a 71% grain diet or a 100% grass diet. The maximum percentage of exsheathed L3 was observed 120 min post-exposure to grass-derived rumen contents, while maximum exsheathment for L3 exposed to grain-derived rumen contents did not occur until 360 min. This work provides the first report of the in vivo exsheathment kinetics for O. ostertagi in its bovine host. Results of this study also support earlier reports that rumen pH may affect the exsheathment efficiency of abomasal trichostrongylids.     

Modeling final scores in US Holsteins as a function of year of classification using a random regression model

Conformation final scores in Holsteins were used to assess genetic changes over the years due to various factors such as selection and changes in trait definition. The model included management group, age group, and stage of lactation as fixed effects; additive genetic effects with random regressions on year of classification using Legendre polynomials with order from linear to cubic; and residual effects assuming heterogeneous variances. Two sets of simulated data were used to test the feasibility of variance component estimation in situations where the definition of the trait of interest changes continuously over time. Estimated variances from the simulated data sets were unbiased. Empirical tests involved 30,041 records of cows with single records scored in 1981-1999. Heritability estimates and additive genetic variances from field data decreased while residual variances increased over time. Differences among estimates of variance components from linear, quadratic and cubic random-regression models were small. Genetic correlations among final scores at years of classification estimated with the multiple-trait model that treated different groups of years as separate traits and with linear, quadratic and cubic random-regression models decreased from 1.0 to a minimum of 0.91, as the distance between the years increased. Although there were no significant differences among estimates of variance components from random-regression models, genetic correlations between different years estimated with higher order random-regression models were closer to those with the multiple trait model that treated different group of years as separate traits. Genetic changes in a trait over time can be studied with a random-regression model.     

Long Chain Fatty Acids of Diet as Factors Influencing Reproduction in Cattle

Cattle are fed moderate amounts of long chain fatty acids (FA) with the objective to enhance lactation and growth; however, recent interest on lipid feeding to cows has focused on reproduction, immunity and health. Increasing the caloric density of the ration by fat feeding has generally improved measures of cow reproduction, but when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not always observed. Feeding fat has influenced reproduction by altering the size of the dominant follicle, hastening the interval to first postpartum ovulation in beef cows, increasing progesterone concentrations during the luteal phase of the oestrous cycle, modulating uterine prostaglandin (PG) synthesis, and improving oocyte and embryo quality and developmental competence. Some of these effects were altered by the type of FA fed. The polyunsaturated FA of the n-6 and n-3 families seem to have the most remarkable effects on reproductive responses of cattle, but it is not completely clear whether these effects are mediated only by them or by other potential intermediates produced during rumen biohydrogenation. Generally, feeding fat sources rich in n-6 FA during late gestation and early lactation enhanced follicle growth, uterine PG secretion, embryo quality and pregnancy in cows. Similarly, feeding n-3 FA during lactation suppressed uterine PG release, and improved embryo quality and maintenance of pregnancy. Future research ought to focus on methods to improve the delivery of specific FA and adequately powered studies should be designed to critically evaluate their effects on establishment and maintenance of pregnancy in cattle.     

Seasonal development and survival of equine cyathostome larvae on pasture in south Louisiana

Cyathostome development and survival on pasture in subtropical climates of the US have yet to be completely defined and available data on seasonal transmission are minimal. In an attempt to study this phenomenon, a group of pony mares and their foals was maintained on a naturally contaminated pasture in southern Louisiana. Fecal egg counts (FEC) and numbers of infective third stage larvae (L3) kg(-1) dry herbage were recorded biweekly during two time periods, from January 1986 through December 1988, and September 1996 through October 1997. A FEC rise occurred during the late summer-early autumn which preceded the peak of L3 on pasture during the winter season. The numbers of cyathostome L3 were reduced during the hottest months of the year due mainly to daily minimum temperatures above 18 degrees C, and in winter during short freezing spells when daily minimum temperatures dropped below 0 degrees C. Tilling of the pasture reduced the number of cyathostome L3 during the early winter months but this is an efficacious measure only if horses are given an effective anthelmintic treatment prior to being returned to pasture. The data collected suggest that parasite reduction in southern Louisiana is possible using a treatment program with treatment beginning at the end of September and continuing through the end of March.     

Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana

The effectiveness of Duddingtonia flagrans in reducing the free living third stage larvae (L(3)) of equine cyathostomes on pasture when fed to horses has been demonstrated in cold temperate climates. The objective of this experiment was to assess the efficacy of D. flagrans against equine cyathostomes in the subtropical environment of southern Louisiana. Fecal pats were prepared by mixing feces obtained from a parasite-free horse fed D. flagrans at a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cyathostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fecal pats were placed on pasture in six replicates at 4-week intervals from March 1997 until January 1998. Comparison of recoveries of L(3) from non-treated control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L(3) survival on pasture was reduced during the months of May, June, July, August and September. The efficacy of the fungus was determined by L(3) recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L(3) during the months of April, May, and October 1997 to January 1998 (range 66-99% reduction, p=0.0001), and for the year as a whole (p=0.0001).     

The evolution of agriculture in ants

Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 million years ago. The subsequent evolutionary history of this agricultural symbiosis was inferred from phylogenetic and population-genetic patterns of 553 cultivars isolated from gardens of "primitive" fungus-growing ants. These patterns indicate that fungus-growing ants succeeded at domesticating multiple cultivars, that the ants are capable of switching to novel cultivars, that single ant species farm a diversity of cultivars, and that cultivars are shared occasionally between distantly related ant species, probably by lateral transfer between ant colonies.     

Progressive ataxia and seizures in a Cocker Spaniel: a new type of neurodegenerative disease with novel intra-neuronal inclusions

AIMS: To describe the histopathological lesions of a new canine disease characterised by progressive ataxia, head tremor and seizures, and to deduce the cause of the lesions.

METHODS: Formalin-fixed tissues were processed into paraffin wax and epoxy resin for light and transmission electron microscopy of variously stained tissue sections.

RESULTS: Significant lesions relevant to the disease were found only in the brain. They consisted of hypoplasia of the cerebellum and the presence of large pale inclusions in the perikaryon of neurons in the neocortex and in macrophages. The inclusion material was not compartmentalised and did not stain for carbohydrate, mucopolysaccharide or lipid. This material displaced nuclei to the periphery of the cells where they were seen as basophilic distorted crescent-shaped structures.

CONCLUSIONS: The inclusions were probably made of polymerised protein similar, though not identical, to those of Pick, Lewy and Collins bodies that characterise a variety of chronic neurodegenerative diseases of humans. A genetic basis to this disease was considered probable.     

Identification of thiabendazole-resistant cyathostome species in Louisiana

A critical trial was performed with five ponies 6-9 months of age and raised on a horse farm with demonstrated benzimidazole-resistant cyathostomes. Eleven species of cyathostomes were recovered, seven of which had resistance to thiabendazole. Degrees of resistance varied among ponies and from species to species. Resistant species were Cyathostomum coronatum, Cyathostomum catinatum, Cylicostephanus minutus, Cylicostephanus calicatus, Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicocylus nassatus. This is the first study identifying resistant cyathostome species in the Gulf Coast region of the USA and, although no new resistant species were found, results differed somewhat from those of other authors in that none of the cyathostome populations that have been studied contain the same complement of resistant species.     

Immune responses of pony foals during repeated infections of Strongylus vulgaris and regular ivermectin treatments.

Ten helminth-free pony foals divided into three groups were used in this study. Eight foals were each experimentally infected per os with 50 Strongylus vulgaris infective larvae weekly for 4 weeks, at which time one foal died of acute verminous arteritis. The remaining seven foals subsequently received 50 S. vulgaris infective larvae every 2 weeks for an additional 20 weeks. Four of the infected foals remained untreated (Group 1) and three of the infected foals were given ivermectin at 8, 16 and 24 weeks post initial infection (Group 2). Two foals served as controls (Group 3). Foals in Group 1 developed eosinophilia, which was sustained throughout the course of infection. A mild eosinophilia also developed in Group 2 foals; however, the eosinophil numbers were markedly reduced for 3 weeks after each ivermectin treatment. Only foals in Group 1 developed significant (P less than 0.05) hyperproteinemia, hyperbetaglobulinemia and a reversal of the albumin/globulin (A/G) ratio 4 weeks after initial infection. Significant (P less than 0.05) IgG anti-S. vulgaris ELISA titers developed in foals in Groups 1 and 2 3 weeks after infection and were sustained for the duration of the experiment. Western blot analysis of soluble somatic antigens of S. vulgaris adult female and male worms probed with sera from foals in Groups 1 and 2 revealed only subtle differences between these animals. The blastogenic reactivity of peripheral blood mononuclear cells (PBMC) to phytohemagglutinin and concanavalin A was not significantly different between groups. Peripheral blood mononuclear cells from foals in Groups 1 and 2 developed significant (P less than 0.05) blastogenic reactivity to S. vulgaris soluble adult somatic antigen when examined at 25 weeks after infection. Mesenteric lymph node cells from foals in Group 2, although not statistically significant, were more reactive to antigen than were the mesenteric lymph node cells from foals in Group 1 when examined at 27 weeks after infection. These results suggest that significant alterations in the immune response of ponies to S. vulgaris does not occur after intravascular killing of larvae by ivermectin treatments.