Long-Term Response Patterns of Tallgrass Prairie to Frequent Summer Burning

Knowledge of how tallgrass prairie vegetation responds to fire in the late growing season is relatively sparse and is based upon studies that are either spatially or temporally limited. To gain a more robust perspective of vegetation response to summer burning and to determine if repeated summer fire can drive vegetational changes in native tallgrass prairie, we evaluated species cover and richness over a 14-yr period on different topographic positions from ungrazed watersheds that were burned biennially in the growing season. We found that annual forbs were the primary beneficiaries of summer burning, but their fluctuations varied inconsistently among years. Concomitantly, species richness and diversity increased significantly with summer burning but remained stable through time with annual spring burning. After 14 yr, species richness was 28% higher in prairie that was burned in the summer than in prairie burned in the spring. Canopy cover of big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans [L.] Nash) increased significantly over time with both summer and spring burning, whereas heath aster (Symphyotrichum ericoides [L.] Nesom), aromatic aster (Symphyotrichum oblongifolium [Nutt.] Nesom), and sedges (Carex spp.) increased in response to only summer burning. Kentucky bluegrass (Poa pratensis L.) cover declined in both spring-burned and summer-burned watersheds. Repeated burning in either spring or summer did not reduce the cover or frequency of any woody species. Most perennial species were neutral in their reaction to summer fire, but a few species responded with large and inconsistent temporal fluctuations that overwhelmed any clear patterns of change. Although summer burning did not preferentially encourage spring-flowering forbs or suppress dominance of the warm-season grasses, it is a potentially useful tool to increase community heterogeneity in ungrazed prairie.     

Tick Abundance and Levels of Infestation on Cattle in Response to Patch Burning

Patch burning (PB) uses frequent, spatially discrete fires throughout a pasture to create variation in the composition and structure of the plant community. The complex vegetation changes incurred from this type of burning regimen in addition to the focal grazing of cattle induced by PB should reduce tick populations by creating less favorable microhabitats. To determine if a reduction in tick populations occurred on PB pastures, three PB-treated pastures and three control pastures were used. PB pastures were divided into six subplots with one burned rotationally each spring and summer. Control pastures and each PB subplot had a burn interval of 3 yr. Pastures were dragged with 1-m² flannel cloth panels to estimate tick abundance for 4 yr. (2006, 2007, 2009, and 2010). Infestation levels with ticks (i.e., tick burden) and weight for five calves and three cows per pasture were recorded once a month from April to October in 2009, 2010, and 2011. Differences in tick abundance between PB pastures and control pastures were not significant except in 2006 when fewer adult ticks were detected in PB pastures. A total of 13 609 ticks were observed on cattle. Animals on PB pastures had 4 028 (29.6%) ticks whereas 9 581 (70.4%) ticks were on cattle from control pastures. Tick burden was significantly reduced on animals in PB pastures compared to animals in control pastures in 4 out of 6 mo. Significant differences in average daily weight gain of calves in PB and control pastures were not detected. Although differences were not detected in questing tick abundance on pastures, significant reductions of tick burden on cattle in PB-treated pastures indicates that PB can be used to help control ticks in pastures.     

重复超排处理对绵羊卵巢的影响

<正> 重复超数排卵处理是家畜胚胎移植中提高供体母畜利用率的重要措施。据报道,使用同一种促性腺激素重复处理会引起兔(Manrer等,1968;Reel等,1976)、绵羊(Paulsson,1962)青年牛(Howe等,1962)和母牛(Turman等,1977;Turman和Wetteman,1978)等超数排卵反应的下降。认为这种现象是由于形成外源促性腺激素抗体所发生的抗药性所致(Willett等1953;Juinudeen等,1966;Onuma等,1969)。但也有些研究并未证实使用同一种促性腺激素重复处理牛(Dziuk等1958;Scanlon,1972)或羊(Gordon,1975)会造成其卵巢反应的下降。本试验的目的是观察在一定时期内,使用同一种促性腺激素(FSH与LH)进行重复超排处理,对母羊卵巢的排卵(排卵反应)以及受精后发情周期等的影响。     

Reduced Response to Intravenous Endotoxin Injections Following Repeated Oral Administration of Endotoxin in the Pig

Three prepubertal gilts were each given 100 mg of endotoxin (ET) in their ordinary feed rations, twice daily for 6 days; 3 other gilts received standard feed. Following ET feeding, all animals were injected intravenously (i.v.) with ET (1.0 µg/kg b.w.) once daily for 5 days. Blood samples were collected and analysed for hematology and total serum bile acids (S-BA), glutamate dehydrogenase (S-GLDH), calcium (S-Ca), iron (S-Fe), zinc (S-Zn) and a blood plasma metabolite (15-ketodihy-dro-PGF2a; P-PG) of prostaglandin F2a. The animals showed no apparent clinical symptoms following ET-feeding, neither did the blood analyses reveal effects of oral ET. However, when iv ET injections were given, the ET-fed animals showed fewer clinical signs of endotoxemia following the 2nd to 5th injection. S-BA and S-GLDH increased markedly in the standard-fed group following the first injection, while the ET-fed animals showed a much smaller increase in S-BA and no change in S-GLDH on that day. The difference in response may be explained by a direct uptake of ET from the gastrointestinal tract in the ET-fed pigs, making them less sensitive to the injected ET     

Development of Immune Response to Experimental Bovine Trichophyton vervucosum Infection

Abstract— Cell mediated and humoral immune responses to experimental Trichophyton verrucosum infection were assessed by sequential cutaneous biopsies, antibody assessments and microscopic monitoring of fungal presence. Histopathologic examination showed the accrual of lymphocytes and other inflammatory cells in the dermis of infected sites. Immunoperoxidase staining of frozen sections with monoclonal antibody preparations revealed an influx of macrophages, BoCD4+ and B0CD8+ lymphocytes and γδ T cells from the 5th day to the 33rd day of infection. A moderate influx of B cells was observed. Protein G-colloidal gold staining revealed the presence of immunoglobulins in the dermis and superficial epidermal layers. Trichophyton specific serum antibodies appeared between days 33 and 55. Microscopic assessment of infected tissues revealed an increase in T, verrucosum elements (mycelium and ectothrix spores) from days 19 to 55. Fungal elements in infected areas did not decrease until after both humoral and cell mediated elements of the immune response were established. These responses imply a combination of cell mediated and humoral events were associated with T. verrucosum immunity and clearance in the calf. Résumé— Le réponse immunitaire humorale et cellulaire a une infection expérimentale àT. verrucosum a été appréciée par des biospsies cutanées successives, des dosages d'anticorps et la recherche microscopique de champignons. L'examen histopathologique a montré un afflux de lymphocytes et d'autres cellules inflammatoires dane le derme des sites infectés. Les marquages en immunopéroxydase par un anticorps monoclonal de coupes congelées a montré un influx de macrophages, lymphocytes BoCD4+ et BoCD8+ et des cellules T γδ, du 5e au 33e jour de l'infection. Un marquage par une protéine G—or colloidal a révélé d'immunogolglobulines dans le derme et les couches supéerficielles de l'épiderme. Les anticorps spécifiques de Trichophyton sont apparus entre 33 et 55 jours. L'examen microscopique des tissus infectés a révélé une augmentation du nombre d'éléments de T. verrucosum (mycelium et spores ectothrix) du 19e au 55e jours. Les éléments fongiques dans les zones infectées n'ont pas diminué avant que les réponses humorales et cellulaires ne solent établies. Ces résponses impliquent qu'une coopération des réponses humorales et cellulaires étaient associées dans l'immunité et la défense contre T. verrucosum. Zusammenfassung— Die zellvermittelten und humoralen Immunantworten auf die experimentelle Infektion mit T. verrucosum wurden durch eine Serie von Hautbiopsien, Antikörperuntersuchungen und mikroskopischer Untersuchung auf das Vorhandensein von Pilzen ausgewertet. Die histopathologische Untersuchung zeigte eine Ansammlung von Lymphozyten und anderen Entzündungszellen in der Dermis der infizierten Stellen. Die Immunperoxidasefärbung der Gefrierschnitte mit monoklonalen Antikörperzubereitungen zeigte einen Influx von Makrophagen, BoCd4-und BoCD8-Lymphozyten und gamma-delta-T-Zellen vom 5. bis zum 33. Tag der Infektion. Es wurde auch ein mäßiger Influx von B-Zellen beobachtet. Die Protein-G-kolloidale Goldfärbung zeigte die Anwesenheit von Immunglobulinen in der Dermis und den oberflächlichen epidermalen Schichten. Trichophyton-spezifische Serumantikörper traten zwischen Tag 33 und 55 auf. Die mikroskopische Untersuchung infizierter Gewebe zeigte eine Zunahme von T. verrucosum-Bestandteilen (Myzel und exktothrixe Sporen) vom Tag 19 bis 55. Pilzteile in infizierten Bereichen verminderten sich weder, nachdem humorale, noch nachdem zellvermittelte Elemente der Immunantwort auftraten. Diese Reaktionen deuten an, daß eine Kombination von zellvermittelten und humoralen Vorgängen im Zusammenhang mit T. verrucosum-Immumtät und Abheilung beim Kalb vorliegt. Resumen Por medio de biposias cutáneas secuenciales, medida de anticuerpos y exámen microscópico de presencia de hongos, se estudió la respuesta inmunitaria de tipo humoral y celular producida por la infección experimental con T. verrucosum. El exámen histopatológico reveló la presencia de agregación de linfocitos y otras células inflamatorias procedentes de la dermis de los puntos infectados. La tintura por medio de inmunoperoxidasa de las secciones congeladas, con preparaciones monoclonales de anticuerpos, demostró un aflujo de macrófagos BoCD4 + y BoCD8 + linfocitos y linfocitos, Tαδ, desde el quinto hasta el día 33 la infección. También se observó un aflugo moderado de linfocitos B. La tintura aúrica de proteina coloidal G reveló la presencia de inmunoglobulinas en al dermis y capas superficiales de la epidermis. Los anticuerpos específicos para la especie Trichophyton aparecieron entre los días 33 y 55. El exámen microscópico de los tejidos afectados demostró un incremento, de los elementos füngicos T. verrucosum (micelio y esporas exótricas) desde los días 19 al 55. Los elementos fúngicos en áreas infectadas no disminuyeron hasta después del establecimiento de ambos tipos de respuesta inmunitaria, humoral y celular. Estas respuestas implican que la combinación de ciertos fenómenos de inmunidad celular y humoral, están relacionados con la desaparición y la inmunidad de la infección producia por T. verrucosum en el ternero.     

Vegetation Responses to Prescribed Burning of Grazed Shortgrass Steppe

Over the past century, fire has been widely suppressed in the western Great Plains, in part because of the potential negative effects on forage production for livestock. More recently, interest in the use of prescribed fire in shortgrass steppe has increased because of the potential applications for wildlife management, control of unpalatable plant species, and restoration of historic disturbance regimes. We studied the effects of prescribed burns conducted during late winter on herbaceous production, forage nitrogen content, and plant species composition of shortgrass steppe on the Pawnee National Grassland in northeastern Colorado. Late-winter burns conducted in moderately grazed sites under a wide range of precipitation conditions during 1997–2001 did not negatively affect herbaceous production in either the first or the second postburn growing season. Burning followed by a severe drought in 2002 reduced production by 19% in the second postburn growing season of 2003. Burns temporarily suppressed the abundance of broom snakeweed (Gutierrezia sarothrae) and prickly pear cactus (Opuntia polyacantha) and enhanced forage nitrogen content during May and June of the first postburn growing season. These findings suggest that, except following severe drought, prescribed burns conducted during late winter in grazed shortgrass steppe for objectives unrelated to livestock production can also have neutral or positive consequences for livestock.     

Effects of Acacia nilotica and Acacia karoo diets on Haemonchus contortus infection in goats

This study was carried out to determine the effects of Acacia karoo and Acacia nilotica diets on Haemonchus contortus infections in goats. Twenty-four Boer goats of mixed sex (live weight 17-22 kg) were randomly assigned to four treatment groups, namely: A. nilotica (AN) group, A. karoo (AK) group, control infected with H. contortus (HC) group and the non-infected control (NHC) group. Animals in the AN, AK and HC groups were orally infected with a single dose of 3000 HC third stage larvae. The AN and AK groups had dried leaves of AN and AK, respectively, included in their basal diet at a rate of 40% dry matter (DM) while the HC and NHC groups had the basal diet throughout the experiment. All animals received a total feed allowance of 500 g DM per day and Katambora Rhodes grass hay ad libitum for roughage. Parameters measured included faecal egg counts and live weight. At the end of the experiment, three animals from each group were slaughtered and abomasal worm burdens were determined. A significant decrease in the faecal egg counts was recorded in animals in the AK group (P<0.05) relative to those in the AN and HC groups. The worm burdens were reduced by 34% in the AK group (P<0.05) and by 10% in the AN group (non-significant) relative to the infected control group. The study indicates that the difference in the effects of the two forages on HC infections may be related to type and concentration of tannins.     

内蒙古荒漠草原土壤呼吸对模拟增温和氮素添加的响应

以内蒙古荒漠草原为研究对象,采用Li-8100土壤碳通量测量系统测定法,研究了控制性增温和氮素添加对荒漠草原土壤呼吸的影响.研究表明:红外辐射加热器在2年间显著提升了试验样地的土壤温度,0~30 cm土壤温度的增幅达0.4~1.0℃;但增温未能显著改变0~30 cm土壤湿度,也未能促进土壤呼吸;施氮、增温＋施氮的交互作用都未显著改变试验样地的土壤呼吸值.试验期间,土壤呼吸存在明显的季节变化,其变化幅度为0.15~3.66 μmol CO₂·m^-2·s^-1.土壤呼吸与降水量和10 cm土壤含水量存在较强的相关性,相关系数分别达0.67和0.70.内蒙古荒漠草原存在明显的水分胁迫,这使得土壤湿度取代土壤温度成为控制土壤碳通量的主要环境因子,而施加矿质氮肥对土壤呼吸的影响不显著.     

Humoral Antibody Response to Experimental Sarcoptes scabiei var. vulpes Infection in the Dog

Abstract— Humoral antibody responses to experimental Sarcoptes scabiei var. vulpes infection in 10 beagle dogs were demonstrated by an ELISA in three experiments. In the first experiment, four dogs, infected with a relatively high dose of S. scabiei, seroconverted 2 weeks post infection. All four animals showed clinical signs of sarcoptic mange. In the second experiment, six dogs were infected with a relatively low dose of S. scabiei. Three of the dogs developed clinical signs of sarcoptic mange and only in these three were antibodies to S. scabiei demonstrated. Seroconversion occurred 4–5 weeks post infection. The six dogs infected with a low dose of Sarcoptes were re-infected with a relatively low dose of mites 7 weeks after the spontaneous clinical recovery of the three dogs that had exhibited mange following the primary infection. The later three dogs showed a specific antibody response within 1 week and the other three dogs within 2 weeks following the re-infection. Resumen En tres experimentos se demostraron las respuestas humorales de anticuerpos a la infección con Sarcoptes scabiei var. vulpes en 10 perros de la raza Beagle por medio de pruebas ELISA. En el primer experimento cuatro de los perros infectados con una dosis relativamente alta de Sarcoptes, seroconvirtieron 2 semanas despues de la infección. Estos cuatro animales mostraban cuadro clínico de infección. En un segundo experimento seis de los perros se sometieron a una dosis relativamente baja del ácaro. Solo tres de estos perros demostraron cuadro clínico de la infección, y en éstos animales exclusivamente se encontraron anticuerpos de S. scabiei. Cinco o seis semanas después de la infección se produjo la seroconversión de los mismos. Los seis perros infectados con una dosis baja se volvieron a re-infectar con otra dosis relativamente baja siete semanas después de la recuperatión clínica espontánea de los tres perros que habían padecido el cuadro clínico de la sarna, después de la infección previa. Los últimos tres perros produjeron una respuesta de anticuerpos específica en una semana, y los otros tres perros en dos semanas después de la infección.     

The response of Acacia karroo plants to defoliation by hand compared to defoliation by goats

Abstract

The leaf and shoot growth of Acacia karroo plants defoliated by goats was compared to that of plants in which leaf only or leaf plus shoot‐tips were removed by hand, to simulate goat browsing.

There were no differences in leaf or shoot production between plants whose leaf only was removed compared to those that had both leaf and shoot‐tips removed. Leaf growth on the plants defoliated by goats at moderate levels was approximately three‐fold that on plants defoliated moderately by hand. The plants defoliated by hand produced approximately twice the amount of leaf that the undefoliated plants produced. Heavy defoliation by both hand and goat, produced approximately half the leaf growth that moderately defoliated plants produced, following equivalent defoliation. Shoot production of all plants defoliated by hand was no different to that of the undefoliated control plants and was considerably less than that of the plants defoliated by goats.     

浅析赛鸽复路

赛鸽复路是指信鸽反复多次参加比赛或训放．如周赛、月赛、季赛、年赛或各种距离的训放等。复路在国外鸽界是相当普遍的比赛和训放形式。名目繁多的比赛或训飞既练出了许多优秀的选手鸽,也为培养信鸽优良品种奠定了坚实的基础。国内也有不少养鸽爱好者乐于此道．但是与国外相比我国的赛事略少,     

The response of Acacia karroo plants to defoliation of the upper or lower canopy

The response of Acacia karroo trees to defoliation of either the upper or lower canopy only, was compared experimentally with that of plants whose whole canopies had been defoliated at a range of defoliation levels. These plants were very sensitive to defoliation of the upper canopy. A 100% defoliation of the upper canopy only, resulted in the same amount of growth as 100% defoliation of the whole canopy. This was considerably less than the growth of plants defoliated overall, at 25% and 50% leaf removal. In contrast, defoliating the bottom half of the canopy only, stimulated growth in the whole canopy to the same degree as defoliation of the whole canopy at 25–50%. The increases of growth were due largely to increased growth in the top half of the canopy. Plants were very sensitive to defoliation in the early‐flush phenophase. This probably masked the positive effects of the partial defoliations applied at this phenophase.     

Diet Quality Modifies Germination of Dichrostachys cinerea and Acacia nilotica Seeds Fed to Ruminants

The pods of many woody plants form an important part of the diet of livestock during the dry season due to their high nutritive value. However, the dispersal of seeds that remain intact and can potentially germinate after excretion is of particular concern when animals consume seeds of encroaching or invasive woody plants. The objectives of this study were to determine the effects of animal species in two experiments (experiment 1: goats, sheep; experiment 2: goats, cattle), diet quality (Medicago sativa hay, Digitaria eriantha hay) and seed characteristics (size, hardness) on the effectiveness of animal seed dispersal and germination of Dichrostachys cinerea and Acacia nilotica seeds. Owing to a limitation on the availability of seeds, the two experiments were done separately at different times. Each animal in both experiments received 1 000 A. nilotica seeds and 1 000 D. cinerea seeds mixed with either a low-quality diet (D. eriantha hay) or a high-quality diet (M. sativa hay). In experiment 1, we found a significant interaction effect of animal species (goats, sheep), diet (high-quality hay, low-quality hay), and seed species (A. nilotica seeds, D. cinerea seeds) on germination (P < 0.0001). There was also a higher seed recovery (P < 0.009) when animals were offered high-quality hay (47.4% ± 4.65) compared to low-quality hay (30.2% ± 3.24). In experiment 2, animal species affected seed recovery (P < 0.0325; goats 32.0% ± 6.44; cattle 50.3% ± 4.27) and germination percentage (P < 0.055; goats 14.1% ± 1.48; cattle 9.3% ± 0.94). The diet quality fed to the animals may affect dispersal and germination. However, animal species and seed characteristics also had important effects on germination of D. cinerea and A. nilotica seeds. Thus, all three of these factors play a major role in dissemination of viable seeds.