AIMS: The principle aim of this study was to examine the association between infection with Theileria orientalis Ikeda type and growth rates of suckled beef calves on four beef farms. In addition, associations between calf sex, sampling time, and individual farm and T. orientalis Ikeda type infection intensity and haematocrit (HCT) were investigated.
METHODS: The study was a prospective longitudinal study in which 240 calves from four purposively selected beef farms in the North Island of New Zealand were blood sampled and weighed in late spring, mid-summer and early autumn. Two farms were from high-risk (A and B) and two from low-risk (C and D) tick areas. Blood samples were analysed to determine HCT, and the number of T. orientalis Ikeda type organisms/µL of blood (infection intensity) using a quantitative PCR assay. A calf was defined as infected if >415 organisms/µL were detected in a blood sample. Linear mixed models were used to examine associations between infection intensity, mean daily liveweight gain (MDG), HCT, calf sex and time of sampling on the four farms.
RESULTS: On Farms A and B nearly all calves were infected at each sampling time, on Farm C <30% were infected at any sampling and on Farm D infection prevalence increased from 32 to 79% between late spring and early autumn. On Farms C and D, from mid-summer to early autumn, mean MDG was 0.127 (95% CI=0.072–0.183) kg/day less for infected than uninfected calves (p<0.001). On all farms MDG was negatively associated with infection intensity for mid-summer and early autumn sampling times (p=0.037). The relationship between time of sampling and infection intensity varied between farms (p<0.001), and between male and female calves (p=0.018). Females had a higher infection intensity than males at the mid-summer and early autumn samplings. The association between HCT and infection intensity varied with sampling time and farm (p=0.018). There was a strong negative association between infection intensity and HCT at the late spring sampling, but in mid-summer there was no association, and in early autumn only a weak association.
CONCLUSIONS AND CLINICAL RELEVANCE: This study has shown that beef farmers in the North Island of New Zealand should be concerned about the welfare effects and economic impacts of T. orientalis Ikeda type infection in suckled beef calves. 相似文献
Des expériences ont été conduites en salle climatisée pour mesurer l'influence de la densité et de la proportion des plantes sur l'envahisse-ment de la luzerne (Medicago sativa L.) établie par le pissenlit (Taraxacum officinale Weber). La durée de l'interférence et la densité de la luzerne ont permis d'expliquer la variation de la biomasse aérienne chez la luzerne cultivée en mélange avec le pissenlit. La densité du pissenlit a été toutefois un facteur important permettant d'expliquer la variation de la biomasse racinaire de la luzerne. La biomasse aérienne et racinaire du pissenlit a varié en fonction de la durée de la compétition, de la densité du pissenlit, de la densité de la luzerne et de la photopériode. Les équations de surface de réponse et hyper-boliques Iinéarisées ont permis de déterminer que la compétition dépendait de la densité plutôt que des proportions de chaque espèce dans le mélange. Effect of plant density and proportion on invasion of lucerne by Taraxacum officinale Weber Experiments were conducted in a growth chamber to establish the effect of plant density and proportion on invasion by dandelion (Taraxacum officinale Weber) of established lucerne (Medicago sativa). Duration of competition and lucerne density accounted for the variation in shoot biomass of lucerne growth in mixture with dandelion. The dandelion density explained a large proportion of the variation in lucerne root biomass. Dandelion root and shoot biomass varied according to duration of competition, dandelion density, lucerne density and photoperiod. Response surface and linearized hyperbolic equations suggested that competition was related more to density than to the proportion of each species in the mixture. Einfluβ der Pflanzendichte und-verteilung auf die Verunkrautung von Lucerne durch Taraxacum officinale Weber In Klimakammerversuchen zum Einfluß der Pflanzendichte und-verteilung auf die Verunkrautung von Luzerne (Medicago sativa L.) durch Löwenzahn (Taraxacum officinale Weber) erwiesen sich die Konkurrenzdauer und die Luzernendichte als wichtige Faktoren für die Bildung der Sproßbiomasse der Luzerne in Mischbeständen mit Löwenzahn, dessen Dichte für die Wurzelbiomasse der Luzerne ausschlaggebend war. Sproß- und Wurzelbiomasse der Löwenzahns variierten mit der Konkurrenzdauer, der Unkraut- sowie der Luzernendichte und der Photoperiode. Die Pflanzendichte erwies sich für die Konkurrenz wichtiger als das Mischungsverhältnis der Arten. 相似文献
Macpherson, M. L., Giguère, S., Hatzel, J. N., Pozor, M., Benson, S., Diaw, M., Sanchez, L. C., Vickroy, T. W., Tell, L., Wetzlich, S., Sims, J. Disposition of desfuroylceftiofur acetamide in serum, placental tissue, fetal fluids, and fetal tissues after administration of ceftiofur crystalline free acid (CCFA) to pony mares with placentitis. J. vet. Pharmacol. Therap. 36 , 59–67. The objective of this study was to determine the pharmacokinetics of CCFA in mares with placentitis and evaluate the disposition of the drug in fetal fluids, fetal membranes, colostrum, and serum of foals. A secondary objective was to obtain pilot data regarding the efficacy of CCFA for improving foal survival in mares with placentitis. Twelve pregnant pony mares were enrolled in the study, inoculated with Streptococcus zooepidemicus, intracervically and assigned to one of three groups: CEFT (n = 3; administered CCFA only; 6.6 mg/kg, IM, q96h); COMBO (n = 6; administered combination therapy of CCFA, altrenogest, and pentoxifylline); UNTREAT (n = 3, no treatment). Treatment was initiated at the onset of clinical signs. Concentrations of desfuroylceftiofur acetamide (DCA), the acetamide derivative of ceftiofur and desfuroylceftiofur metabolites, were measured using high‐performance liquid chromatography. Maximum and minimum serum concentrations of DCA at steady state in treated mares were 2.40 ± 0.40 μg/mL and 1.06 ± 0.29 μg/mL, respectively. Concentration of DCA in colostrum was 1.51 ± 0.60 μg/mL. DCA concentrations in placenta and fetal tissues were very low (median = 0.03 μg/mL) and below the minimum inhibitory concentration of relevant pathogens. DCA was not detected in amniotic fluid or foal serum. Treatment did not appear to improve foal survival (CEFT: 0/3; COMBO: 2/6; UNTREAT: 2/3). Bacteria were recovered from the uterus of most mares postpartum and from blood cultures of most foals regardless of treatment. 相似文献
Donalisio, C., Barbero, R., Cuniberti, B., Vercelli, C., Casalone, M., Re, G. Effects of flunixin meglumine and ketoprofen on mediator production in ex vivo and in vitro models of inflammation in healthy dairy cows. J. vet. Pharmacol. Therap. 36 , 130–139. In this study, ex vivo assays were carried out in dairy cows to evaluate the anti‐inflammatory effects of two nonsteroidal anti‐inflammatory drugs: ketoprofen (KETO) and flunixin meglumine (FM). Twelve healthy Holstein dairy cattle were randomly allocated to two groups (n=6): group 1 received FM and group 2 received KETO at recommended therapeutic dosages. The anti‐inflammatory effects of both drugs were determined by measuring the production of coagulation‐induced thromboxane B2 (TXB2), lipopolysaccharides (LPS) (10 μg/mL)‐induced prostaglandin E2 (PGE2), and calcium ionophore (60 μm )‐induced leukotrien B4 (LTB4). Cytokine production was assessed by measuring tumor necrosis factor‐α (TNF‐α), interferon‐γ (IFN‐γ) and interleukin‐8 (CXCL8) concentrations after incubation in the presence of 10 μg/mL LPS. The IC50 of FM and KETO was determined in vitro by determining the concentration of TXB2 and PGE2 in the presence of scalar drug concentrations (10?9–10?3 m ). Both FM and KETO inhibited the two COX isoforms in vitro, but showed a preference for COX‐1. FM and KETO showed similar anti‐inflammatory effects in the cow. 相似文献