Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length

We describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone-releasing hormone (LHRH) produced viable gametes in 21-24 h, and triploidy was induced using a pressure treatment of 563 kg/cm² on embryos for a 1-min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group-specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N = 25 erythrocytes) for individual fish, which were 14.43-16.66 μ.m for triploids, and 10.23-13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (±) = -196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.     

Sickness, mortality and the buller steer syndrome in a western Canadian feedlot

Objective To determine if an association existed between sickness, mortality and bullers in a western Canadian feedlot.
Design A retrospective epidemiological study.
Animals 78,445 male cattle that entered a 24,000-head feedlot in western Canada from 1991 to 1993.
Procedure Animal health records for bullers were collected and analysed to see if they were at greater risk of sickness and mortality than other steers, and to see if pens with a high prevalence of bullers also had a high prevalence of sickness and mortality.
Results The prevalence of bullers increased with increasing age of cattle on arrival at the feedlot (R = 0.36; P < 0.001). Sickness and mortality decreased with increasing age of cattle on arrival. However, sickness and mortality in bullers relative to other steers actually increased with increasing age on arrival suggesting an interaction existed between sickness and bullers. Bullers were significantly (P < 0.05) more likely to get sick and to die than other steers. In all cases, there was a strong temporal association between sickness and bullers, with sickness and bullers mostly occurring within the first 30 days of the feeding period. On average, pens of cattle with a high prevalence of bullers did not have a correspondingly high prevalence of sickness or mortality.
Conclusion This study suggests that sickness is an effect modifier of dominance behaviour and therefore bullers in feedlot steers. Bullers should always be checked for signs of sickness and treated accordingly. Further research is needed to investigate the effects of sickness on dominance behaviour in pens of feedlot cattle.     

α‐Tocopherol absorption and polyunsaturated fatty acid metabolism in the developing chick embryo

1. A study has been made relating α‐tocopherol uptake from the yolk and yolk sac membrane to the polyunsaturated fatty acid status of the liver during incubation.

2. Whereas at day 15 of incubation lipid in the liver showed an exceedingly high degree of unsaturation and potential for oxidation because of accumulation of C20 and C22 polyunsaturated fatty acids, α‐tocopherol concentrations were exceedingly low.

3. In contrast, very high concentrations of α‐tocopherol occurred within the liver just before hatching by which time amounts of polyunsaturates and the need for oxidation protection had reduced considerably.     

Aspects of nasal, oropharyngeal and anal carriage of Staphylococcus intermedius in normal dogs and dogs with pyoderma

Aspects of carriage of Staphylococcus intermedius were studied in three groups of dogs. In 150 normal dogs presenting for annual booster inoculations, carriage rates for S . intermedius in the anterior nares (36%) and on the anal ring (36%) were recorded. In 44 dogs presented for routine elective surgery, carriage of S . intermedius was higher on the caudal nares (41%) than on the anterior nares (34%), oropharynx (25%) or anal ring (30%) allowing an assessment of the accuracy of basing nasal carriage rates on swabbing the anterior nares alone. A new finding was that animals from multidog households had significantly higher ( P < 0.005) nasal and anal carriage rates than dogs from single-dog households. In 33 dogs with superficial pyoderma, carrier rates were similar to those reported by others and significantly higher than in the other two groups with regard to both nasal and anal carriage ( P < 0.05 and P < 0.005, respectively).     

Identification of the causal agent of pistachio dieback in Australia

Symptoms associated with pistachio dieback in Australia include decline (little or no current season growth), xylem staining in shoots two or more years old, trunk and limb lesions (often covered by black, superficial fungal growth), excessive exudation of resin, dieback and death of the tree. Bacteria belonging to the genus Xanthomonas have been suggested as the causal agent. To confirm the constant association between these bacteria and the disease syndrome, the absence of other pathogens and the identity of the pathogen, we performed a series of isolations and pathogenicity tests. The only microorganism consistently isolated from diseased tissue was a bacterium that produced yellow, mucoid colonies and displayed morphological and cultural characteristics typical of the genus Xanthomonas. Database comparisons of the fatty acid and whole-cell protein profiles of five representative pistachio isolates indicated that they all belonged to X. translucens, but it was not possible to allocate the isolates to pathovar. Pathogenicity tests on cereals and grasses supported this identification. However, Kochs postulates have been only partially fulfilled because not all symptoms associated with pistachio dieback were reproduced on inoculated two-year-old pistachio trees. While discolouration was observed, dieback, excessive resinous exudate and trunk and limb lesions were not produced; expression of these symptoms may be delayed, and long-term monitoring of a small number of inoculated trees is in progress.     

Contributions of visual cues to cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), resistance in novel host genotypes

Herbivorous insects can demonstrate great selectivity among visual cues. The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) (syn. Ceutorhynchus assimilis (Paykull)) is also influenced by visual cues. Here, we present results of a study examining the attractiveness of flowers and foliage of Sinapis alba (a suboptimal host for larval development), Brassica napus (an excellent host for larval development) and novel lines derived from S. alba x B. napus; several of these have been demonstrated to be resistant in field and laboratory tests. Attractiveness, reflectance properties and resistance demonstrated in field trials were related. Responses to host plants differed among plant genotypes and were related to the amounts of UV and yellow reflected from flowers. Moderate UV reflectance greatly increased the attractive effects of yellow. Fewer weevils responded to test plants with greater or lesser floral UV reflectance.     

A cation exchange index for assessing degradation of acid soil by further acidification under permanent agriculture in the tropics

Soil acidification and related land degradation are becoming more important worldwide and are challenging the concept of sustainability of current land management systems. We have studied the impact on soil properties of two management systems, one in a tropical savanna, the other in a humid subtropical environment, particularly in relation to their cation chemistry. In Northeast Thailand the properties of an Acrisol cleared of dipterocarp forest some 37 years previously and used for continuous crop production are compared with adjacent undisturbed forest. In southern Queensland, Australia, the properties of a Luvisol used for intensive pasture production for 36 years are compared with those prior to introduction of the management system. Under both regimes, the soil pH fell by about 1 unit, with an increase in aluminium saturation of the cation exchange complex. Organic carbon in the Acrisol greatly decreased, but in the Luvisol it increased significantly. Consequently, the effects on surface charge characteristics were strikingly different, in that the Acrisol had been almost irreversibly degraded, whereas acidification and base diminution in the Luvisol can be easily reversed through conventional management. The amount of degradation caused by each management system has been quantified in terms of a Saturation Index, S_u: S _u = 100 × (C_u5.5 ? Σ)/C_u5.5, where C_u5.5 refers to the cation exchange capacity on the undisturbed (forested) site and Σ is the sum of the base cations at field pH. This index encompasses an assessment of the degree of degradation taking into account the previous land use, in this case forest, and that due to anthropogenic disturbance. For the Queensland Luvisol S_u does not change, because the pasture management has not appreciably altered the CEC at pH 5.5. However, for the Thailand site S_u increased from 0 to 86%. Consequently in its present state, the surface horizon of this cultivated soil can retain only about 15% of the basic cations it could ideally hold under undisturbed conditions.