Modelling land use strategies to optimise crop production and protection of ecologically important weed species

There is a need to develop farming systems that enable both a satisfactory level of crop production and suitable environmental conditions for natural species. Wildlife‐friendly cropping techniques, such as a reduced amount of applied herbicide or a lower crop density, might be adopted in order to maintain populations of weed species of biological interest. An alternative might be to adopt an intensive cropping system in a part of the field and spare the other part as set‐aside or field margins, available for the natural development of plant species. The objective of this study was to present a method to compare two strategies for maintaining a desirable level of abundance of a given species of interest in agricultural areas, specifically (i) a strategy based on a wildlife‐friendly cropping system in a large cultivated area and (ii) a strategy based on a more intensive cropping system in a reduced area of cultivation, i.e. with land‐sparing. The principle is to calculate the ratio of crop production obtained with strategy (i) to the production obtained with strategy (ii) for a given target density of natural species. We show that the value of this ratio, and thus the relative performance of the two strategies, depends on the density of the weed species that can be maintained in an uncultivated ecological area. The method is applied in case studies of two plant species with contrasting ecology and conservation goals. The numerical results show that the strategy based on a wildlife‐friendly cropping system is more profitable in most situations.     

Progress in the development of tuberculosis vaccines for cattle and wildlife

Vaccination against bovine tuberculosis is likely to become an important disease control strategy in developing countries, which cannot afford a test and slaughter control programme, or in countries which have a wildlife reservoir of Mycobacterium bovis infection. In the past decade, considerable progress has been made in the development and evaluation of tuberculosis vaccines for cattle and for a range of wildlife maintenance hosts including possums, badgers, deer and African buffaloes. Experimental challenge systems have been established for the different target species and the resulting disease process has mimicked that seen in the field. In cattle, neonatal vaccination with BCG appeared to be more effective than vaccination of 6-month-old calves and in most situations no other vaccine has been shown to be better than BCG. However, prime-boost strategies involving combinations of BCG with a protein or DNA vaccine, to improve on BCG vaccination alone, have produced very encouraging results. Differential diagnostic tests have been developed using mycobacterial antigens that are only present in virulent M. bovis to differentiate between BCG-vaccinated and M. bovis-infected cattle. BCG vaccine has been shown to reduce the spread of tuberculous lesions in a range of wildlife species and a prototype oral bait delivery system has been developed. Prospects for the development of improved vaccines against bovine tuberculosis are promising and vaccination approaches could become very valuable in the control and eradication of bovine tuberculosis.     

Alcohol diluent provides the optimal formulation for calcium chloride non-surgical sterilization in dogs

Background

Surgical castration is widely used to sterilize male dogs, but has significant impacts on time to perform the operation, recovery of the animals as well as cost, which can limit population control programs. Previous research has shown intratesticular injection of calcium chloride dihydrate (CaCl₂) in saline to be a promising alternative to surgery. However, long-term azoospermia was not maintained at dosages low enough to avoid side effects. In the search for an optimized formulation, the current investigation is the first study on long-term sterilization effects of intratesticular injection of CaCl₂ in either lidocaine solution or alcohol in dogs. CaCl₂ at 20% concentration in lidocaine solution or alcohol was administered via intratesticular injection to groups of 21 dogs each. The treated animals were examined at 2, 6, and 12 months for sperm production, blood levels of testosterone, and side effects; at time zero and 12 months for testicular size and semen volume. The experimentally treated animals were compared to a control group receiving saline injection only.

Results

Testicles of dogs treated with CaCl₂ in either diluent significantly decreased in size. After administration of CaCl₂ in lidocaine solution, sterility was achieved for at least 12 months in 75% of treated dogs. However, optimal long-term contraceptive effectiveness was achieved with CaCl₂ in alcohol, which resulted in azoospermia over the 12-month study period. Testosterone levels significantly decreased following treatment with CaCl₂, and sexual activity disappeared. Although testosterone returned to baseline levels by 12 months for the group treated with CaCl₂ in lidocaine, dogs injected with CaCl₂ in alcohol had a 63.6% drop in testosterone level, which remained at the low end of physiological range throughout the study. No adverse effects were noted.

Conclusions

A single, bilateral intratesticular injection of 20% CaCl₂ in 95% ethanol was a reliable method for induction of sterilization in 18–28 kg male dogs in this study. The approach showed long-term efficacy and reduced sexual behavior. This chemical method of sterilization might provide an effective, efficient alternative to surgical castration that can have positive impacts on dog welfare.     

Effects of chicken thymic stromal cells on the growth and differentiation of thymocytes in vitro

We examined contact-mediated effects of chicken thymic stromal cells (TSC) on thymocyte differentiation by co-cultivation of these cell populations. The primary cultures of TSC isolated from thymus mainly have consisted of epithelial cells which were polygonal in shape, possessed long processes and expressed MHC class II antigen. When thymocytes were co-cultured with TSC, 60% to 70% of thymocytes attached to TSC and some of them engulfed underneath TSC. These attached thymocytes were CD4-CD8- and CD4+CD8+ subsets and expressed alpha/beta TCRhigh or gamma/delta TCRlow. Some of the thymocytes attaching to TSC showed an increase of intracellular and nuclear density, fragmentation of cytoplasm and nuclei, and DNA fragmentation. And also, thymocytes attaching to TSC contained a higher percentage of cycling (S and G2 + M phase) cells than nonattaching cells. These results indicate that specific subsets in thymocytes selectively bind to TSC and undergo apoptotic death or proliferation because of interaction with TSC. Chicken TSC may play an important role in thymic differentiation by direct contact within the thymus as in mammals.     

Characterization of age- and location-associated variations in the composition of articular cartilage from the equine metacarpophalangeal joint

Objective: To characterize the impact of age, gender, location and individual animal variation on the composition of articular cartilage from the metacarpophalangeal joint of horses. Design: Cartilage specimens were obtained from the metacarpophalangeal joints of 28 male, female and castrated male horses ranging in age from one day to 27 years of age. Cartilage samples from the distal metacarpus, proximal first phalanx and proximal sesamoids were analyzed separately. Chondrocyte number, DNA content, proteoglycan concentration and total collagen content were determined for each animal and joint location. Results: Age and joint location had a significant effect on chondrocyte number and DNA content with higher cell counts and DNA content detected in cartilage from the youngest age groups and in cartilage from the metacarpus and proximal sesamoids. The influence of age on chondrocyte numbers was not significant in horses over two years of age. Both age and joint location also influenced total proteoglycan and collagen content. Lower proteoglycan and collagen concentrations were detected in younger horses, and cartilage from the metacarpus had lower proteoglycan and collagen concentrations than that from other joint locations. Gender did not appear to influence chondrocyte number or matrix content of equine articular cartilage. However, there was significant residual variation in cellularity, proteoglycan levels and collagen content between individual animals that could not be explained by the signalment factors considered in this study. Conclusions: Future studies examining equine articular cartilage should avoid direct morphologic comparisons between animals of different ages, and any comparisons made between individuals should be interpreted cautiously. In addition, in vitro tissue culture models should avoid the use of cartilage pooled from different animals or from different locations within the same joint.     

Assessment of in vitro interferon-gamma responses from peripheral blood mononuclear cells of cattle infected with Mycoplasma mycoides ssp. mycoides small colony type

Contagious bovine pleuropneumonia (CBPP) is a lung disease caused by the bacterial pathogen Mycoplasma mycoides ssp. mycoides small colony type (MmmSC). It has been spreading due to a number of factors including poor vaccine efficacy and poor sensitivity of current diagnostic tests. The purpose of this study was to assess interferon gamma (IFN-gamma) release after stimulation of peripheral blood mononuclear cells (PBMC) from experimentally infected cattle. PBMC collected from 15 artificially infected animals were incubated with different concentrations of total MmmSC antigen. After 72h of incubation the IFN-gamma release was measured and found to be elevated in 11 animals. We did not observe a correlation between IFN-gamma release of animals with and without pathomorphological gross lesions. Therefore, our data do not confirm a role for CD4 T-lymphocytes in protection, since there is no correlation between IFN-g secretion (supposed to be mainly derived from CD4 T-cells) and disease severity. Additionally, we applied immunocytochemistry on affected lung tissue and detected no build up of T-lymphocytes (CD4 T-cells, CD8 T-cells) but a high presence of myeloid cells.     

The effect of biological isolation and a molt-inducing regimen on the recovery of Mycoplasma gallisepticum from commercial Leghorn hens

Two trials were conducted to determine the effect of induced molt on the reisolation of Mycoplasma gallisepticum (MG) from commercial leghorn hens that had been eyedrop-inoculated with MG at 10 weeks of age. Chickens were maintained in a conventional floored chicken house on dry litter through 100 weeks of age. At age 64 weeks, 4 days (Trial 1), and at 100 weeks (Trial 2), hens were swabbed and cultured for MG and then molted in biological isolation units. Swabs were again taken at the end of each molt. No difference was observed in the number of MG isolations between molted hens and controls that did not undergo molting. However, a significant decrease in MG isolations was observed in both trials from swabs obtained when hens were housed on dry litter floors as compared with swabs taken from the same hens after 18 days (Trial 1) or 21 days (Trial 2) of confinement in isolation units.     

Pharmacokinetics of oral ivabradine in healthy cats

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical method for the measurement of the novel heart rate-lowering drug ivabradine and its major metabolite, S-18982, was cross-validated in the plasma of eight healthy cats. Plasma concentrations were then determined after single and repeated oral administration of ivabradine. Individual plasma concentrations versus time from each cat were used in compartmental analysis using the commercially available software WinNonlin. Both ivabradine and S-18982 reached their maximum concentrations of 103.33 and 3.86 ng/mL within 1 h. Following repeated administration, areas under the plasma concentration-time curves for ivabradine and S-18982 did not significantly increase. Two-compartmental and one-compartmental models with first-order input and elimination provided the best fit to the data for ivabradine and S-18982, respectively. Both models were combined to produce a single 4-compartment model characterizing ivabradine and S-18982 pharmacokinetics. The results of this study indicate that repeated oral doses of ivabradine produced plasma drug concentrations suitable for 12-h dosing intervals in healthy cats. Furthermore, the analytical assay and combined ivabradine/S-18982 model provide tools for further evaluation of ivabradine pharmacokinetics and pharmacodynamics in future studies in cats.     

Conception rates in early postpartum ewes bred naturally or by intrauterine insemination

Ewes were treated with a medroxyprogesterone acetate (MAP) sponge for 8 d followed, at sponge removal, with 500 IU pregnant mare serum gonadotropin (PMSG) at d 30, 40 or 50 (d 0 = lambing) to induce estrus. Dry and lactating ewes were divided into equal numbers at each postpartum day and bred at estrus. Conception rates and number of accessory sperm were determined by flushing the oviducts 3 d after mating and examining the recovered ova. There was no effect (P greater than .05) of lactational status on conception rates. Conception rates increased (P less than .05) from d 30 (10%) to d 40 (45%) and from d 40 to d 50 (80%). There were fewer (P less than .05) ova with accessory sperm (5/26) in d-30 ewes compared with d-40 (10/27) or d-50 (12/24) ewes. In Exp. 2, ewes were assigned to two groups after receiving PMSG on d 30: 1) mated naturally or 2) inseminated during laparotomy near the uterotubal junction (UTJ). Dry and lactating ewes were divided evenly within each of the two treatments. Oviducts were flushed and ova were examined for cleavage. The conception rate was 60% in ewes that were inseminated in the UTJ vs 10% in ewes mated to rams (P less than .05). Lactational status had no effect on results. In conclusion, conception rates in postpartum ewes treated with MAP sponge and PMSG increased from postpartum d 30 to d 50 with natural breeding, and d-30 conception rates were increased over natural mating by insemination into the uterine horn near the UTJ.