Potential for mitigating atmospheric ammonia in Canada

Most ammonia (NH₃) emissions (85%) in Canada come from agricultural sources (400 kt/yr). There are international conventions that require countries to mitigate NH₃ emissions but there are no federal or provincial guidelines in Canada stipulating emission targets or best practices for agriculture. This study examines the potential for mitigating atmospheric NH₃ using a range of approaches. Taking current farm practices into account, employing proven low‐cost measures (low‐emission slurry application and slurry storage covers) would reduce annual emissions from livestock operations by 16 kt NH₃‐N, while using all available low‐cost measures would reduce emissions by 79 kt NH₃‐N or 26% of livestock emissions. Another 36 kt/yr could be avoided by improving fertilizer practices, so that the total potential reduction would be about 29% of all agricultural emissions. Emissions from beef cattle and pig production could be reduced by 18% if consumption was cut by 50%, with greater mitigation if production for export was reduced, although the economic and social consequences need to be considered. Mitigation practices must be viewed in the context of possible pollution swapping especially in surplus nitrogen situations. Emissions must also be considered in terms of atmospheric NH₃ transport to and from the USA, therefore bi‐national agreements to jointly reduce emissions might be needed. It may be more cost‐effective in Canada to strategically reduce emissions to minimize risks to health (from particulate matter) and the environment rather than to reduce annual national emission targets.     

Anthropogenic Vanadium-Chromium-Iron and Cerium-Lanthanum-Iron Particles in Settled Urban House Dust: CCSEM Identification and Analysis

There is continuing concern over the health threat posed by theinhalation of ambient, transition-metal-containing particulatematter. Here, we report on the collection of two types ofanthropogenic, airborne particles, composed of iron with vanadiumand chromium (FeVCr) and iron with the rare earth metals ceriumand lanthanum (FeCeLa), respectively. Bi-weekly deposition platesamples were collected on indoor window sills of residentiallocations in inner-city Syracuse, NY. Sampling was continuous ateach location for two months during the spring of 1999. Themetal-bearing particles were identified, analyzed, and sizedin situ on each deposition plate using computer controlledscanning electron microscopy (CCSEM). Approximately 17% of thoseanalyzed by CCSEM fell into the inhalable size fraction. Particle loading varied between locations and changed over time.This was probably a function of various factors affectingparticle deposition rates. Notwithstanding, the plate loadingsfor the FeVCr-bearing particles tended to peak during the middleof the sampling period, suggesting that a single source/processwas operating to produce the FeVCr particles. The large sizeattained by some of these particles (greater than 50 μm inaggregates) suggest that long range transport was probably notinvolved.     

Complete heart block associated with lupus in a dog

A 5-year-old Poodle-cross was initially presented for exercise intolerance and difficulty in chewing and yawning. Some months later it acutely developed lethargy referable to complete heart block. Further investigations before and after permanent pacemaker implantation demonstrated Coombs-positive immune-mediated haemolytic anaemia, presumptive masticatory myositis and hypoadrenocorticism, suggesting the possibility of multisystem auto-immune disease. A diagnosis of systemic lupus erythematosus (SLE) was made based on these findings and a positive anti-nuclear antibody titre. It was thought that immune-mediated destruction of cardiac conduction tissues was responsible for the development of atrioventricular conduction block. Glucocorticoid deficiency was corrected using cortisone replacement therapy. SLE was controlled successfully for 10 months using azathioprine monotherapy until signs, subsequently shown to be due to subacute bacterial endocarditis, resulted in the death of the patient. Lupus should be considered as a potential underlying aetiology in dogs that develop heart block.     

2002: Hiatal hernia in a puppy

A sliding hiatal hernia (where the terminal oesophagus, oesophagogastric junction and part of the stomach move cranially through a diaphragmatic defect) was diagnosed in a 4-month-old, Shar-Pei puppy presented for evaluation of regurgitation. The diagnosis was confirmed using radiography. Herniorraphy consisted of repositioning the stomach within the abdomen, plicating the diaphragmatic hiatus and performing a tube gastropexy to the left abdominal wall. Veterinary practitioners should have a high index of suspicion of hiatal hernia in young puppies, particularly Shar-Peis and British Bull Dogs, that present with persistent vomiting or regurgitation.     

Systemic blastomycosis in a horse.

Progressive multisystemic disease caused by Blastomyces dermatitidis was diagnosed in a 17-year-old Quarter horse broodmare. The mare had been treated unsuccessfully with antibiotics for mastitis 3 months postpartum. The disease progressed to exudative cutaneous lesions affecting the ventrum, pectoral region, and limbs accompanied by weight loss across several months. Yeast bodies were observed in swabs of the cutaneous exudate, suggesting a clinical diagnosis of blastomycosis. Following referral, pleural effusion, cavitated lung lesions, and hyperproteinemia were identified, and the mare was euthanized because of poor prognosis. Necropsy revealed extensive pyogranulomas in the mammary gland, skin, subcutaneous tissues, and lungs, accompanied by thrombi in major blood vessels of the lungs and hind limbs. Histologically, pyogranulomatous inflammation was evident in many tissues, and fungal organisms were seen in sections of mammary gland, skin, subcutis, pericardium, and lung. Blastomyces dermatitidis was cultured from mammary tissue, lungs, lymph node, and an inguinal abscess. Although blastomycosis is endemic in the area of origin of the mare in northwestern Wisconsin, the disease is extremely rare in horses and hence easily misdiagnosed. Unique features of this case included the extent of mammary gland involvement and the presence of thrombi in multiple sites.     

Tailoring codend mesh size to improve the size selectivity of undifferentiated trawl species

Tiger flathead, Neoplatycephalus richardsoni (Castelnau), and sand flathead, Platycephalus bassensis Cuvier, are undifferentiated and managed with a common legal minimum length (LML). The Commonwealth Trawl Sector (CTS) and the Tasmanian Danish‐seine fishery (TDSF) use a minimum codend mesh sizes of 90 and 70 mm, respectively. The codend mesh size should be tailored to the LML, which is based on the length of first maturity of females (M₅₀). This study found the length–girth relationship of N. richardsoni and P. bassensis was not significantly different. Using the covered codend method, these two species had 50% retention lengths (L₅₀) of 294 ± 2 and 307 ± 3 mm, in 70‐mm and 90‐mm codends, respectively. L₅₀ estimates for mesh sizes from this study and others produced a curvilinear relationship: y = 120 ln(x) ? 214, with an r² of 0.8504. The size at maturity (M₅₀) for female N. richardsoni was 337 mm, which is larger than the estimate for female P. bassensis (247 mm). There is a mismatch between the estimates of L_50, the estimates of M₅₀ and the LMLs in each fishery, leading to suboptimal exploitation of female Platycephalus. The model produced in this paper recommends a codend mesh size of 98 mm for both fisheries to exploit Platycephalus species sustainably.     

Effects of feeding high-oil corn to beef steers on carcass characteristics and meat quality

To assess the effects of feeding high-oil corn on carcass characteristics and meat quality, 60 yearling steers were fed high concentrate diets containing either control corn (82% of diet), high-oil corn (82% of diet), or high-oil corn at a concentration that was isocaloric with the control diet (74% of diet). After being fed for 84 d, steers were slaughtered. At 72 h postmortem, carcass data were collected and rib sections from five steers grading U.S. Choice and five steers grading U.S. Select from each treatment were collected, vacuum packaged, and aged for 14 d. Three steaks (2.54 cm thick) were removed from each rib for Warner-Bratzler shear force measurement, sensory appraisal, and fatty acid composition analyses. Data were analyzed with treatment as the main effect for the carcass data and treatment, quality grade, and two-way interaction in the model for the longissimus data. The two-way interaction was nonsignificant (P > 0.05) for all variables tested. No differences were detected (P > 0.05) in carcass measurements except for marbling scores and quality grades, both of which were greater (P < 0.05) for carcasses from steers fed the high-oil corn. Overall, 78% of steers fed the high-oil corn graded U.S. Choice compared with 47% for the control and 67% for isocaloric group. Shear force and sensory properties of the longissimus were not different (P > 0.05) among treatments. Steaks from U.S. Choice carcasses rated higher (P < 0.05) for tenderness and tended to rate higher (P < 0.10) for juiciness. Feeding the isocaloric and high-oil diets increased (P < 0.05) linoleic acid, arachidonic acid, and the total PUFA content of lipid extracted from the longissimus. Saturated fatty acid percentage was lowest (P < 0.05) for high-oil corn and highest (P < 0.05) for control, with isocaloric being intermediate. Feeding high-oil corn increased (P < 0.05) pentadecyclic acid, margaric acid, and total odd-chain fatty acid content. Feeding high-oil corn in finishing beef cattle diets enhanced intramuscular lipid deposition and increased unsaturation of fatty acids of the longissimus.     

INTER-VARIETAL COMPETITION IN PERENNIAL RYEGRASS SWARDS

Pure cultures and mixtures of equal numbers of plants of Irish. New Zealand and S23 perennial ryegrass were grown in artificially constructed swards under field conditions. They were cut every time they reached grazing height for three successive years. Counts of plant numbers and tiller numbers per plant made each November show that S23 suppressed both plant number and tiller number per plant of Irish ryegrass and to a lesser extent of New Zealand perennial ryegrass. Its own plant number and tiller number per plant were improved in these combinations. New Zealand perennial ryegrass suppressed plant and tiller numbers of Irish perennial ryegrass.
Varying the method of cutting to match the growth of each variety resulted in improved plant survival and tiller number per unit area of Irish perennial ryegrass when cut according to the growth of S23, i.e. late in the spring. The importance of the effect of experimental technique is discussed.     

Clinical and pathological responses of weaned pigs to atmospheric ammonia and dust

Nine hundred and sixty weaned pigs were exposed for five weeks to controlled concentrations of atmospheric ammonia and dust in a single, multifactorial experiment. The treatments were a mean dust concentration of either 1.2, 2.7, 5.1 or 9.9 mg/m3 (inhalable fraction) and a mean ammonia concentration of either 0.6, 10.0, 18.8 or 37.0 ppm, concentrations representative of commercial conditions. The experiment was carried out over two years and the pigs were used in eight batches, each consisting of five lots of 24 pigs. Each treatment combination was replicated once, and an additional control lot (nominally 0 mg/m3 dust and 0 ppm ammonia) was included in each batch. The dust concentration was the same in the other four lots in each batch in which the four concentrations of ammonia were used; thus, the split-plot design was more sensitive to the effects of ammonia than dust. The groups of pigs were kept separately in five rooms in a purpose-built facility, and the pollutants were injected continuously into the air supply. Ammonia was supplied from a pressurised cylinder, and the endogenous dust in each room was supplemented by an artificial dust manufactured from feed, barley straw and faeces, mixed by weight in the proportions 5:1:4; its ingredients were oven-dried, milled and mixed, and then resuspended in the air supply. The health of the pigs was assessed in terms of general pathology, respiratory tract pathology, and the microbiology of the nasal cavity, trachea and lung. In each batch, postmortem examinations were carried out on 40 pigs after five weeks' exposure to the pollutants and on 30 pigs two weeks later to test for carryover and recovery--a total of 560 pigs. These examinations revealed minimal gross pathology and widespread minor pathological changes of little significance. The pigs' turbinate and lung scores were low and unaffected by exposure to pollutants. All the putative bacterial pathogens, with the exception of toxigenic Pasteurella multocida type D, were isolated from the respiratory tract of the pigs of both ages, but there were no differences between the effects of the different concentrations of pollutants.