The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses

Background: Plasma α‐melanocyte‐stimulating hormone (α‐MSH) and adrenocorticotropin (ACTH) concentrations in horses vary with season, confounding diagnostic testing for pituitary pars intermedia dysfunction (PPID). Hypothesis: The goals of this study were to determine whether seasonal variation in plasma α‐MSH and ACTH concentrations in horses is influenced by geographic location, breed, or PPID. Animals: Healthy light breed horses residing in Florida, Massachusetts, and Finland (n = 12 per group); healthy Morgan horses (n = 13); healthy ponies (n = 9) and horses with PPID (n = 8). Methods: Monthly plasma α‐MSH and ACTH concentrations were measured by radioimmunoassay. Nonlinear regression analysis was used to estimate the time of peak hormone concentrations. Mean hormone concentrations in fall and nonfall months were compared. Results: The fall peak plasma α‐MSH concentration occurred earlier in horses residing at more northern locations. Mean seasonal α‐MSH concentrations were similar in all healthy groups at all locations, but in the fall, plasma ACTH concentrations were higher in horses living in more southern locations. Plasma ACTH but not α‐MSH concentrations were higher in Morgan horses compared with light breed horses from the same location. Hormone concentrations of ponies did not differ from those of horses during either season. Concentrations of both hormones were high in the fall compared with the spring in horses with PPID. Conclusions and Clinical Importance: These findings suggest geographic location of residence and breed may affect the onset, amplitude, or both of the seasonal peak of pars intermedia (PI) hormones and should be considered when performing diagnostic testing for PPID. Horses with PPID maintain seasonal regulation of PI hormone output.     

Effect of C:N Ratio on Microbial Activity and N Retention: Bench-scale Study Using Pulp and Paper Biosolids

The effect of C:N ratio on the performance of bench-scale composting systems treating pulp and paper biosolids was investigated. The biosolids used were obtained from the Pine Falls Paper Company located in Manitoba. The biosolids, on a wet basis, consisted of 41% primary biosolids, 21% secondary biosolids, and 39% deinking plant sludge. The biosolids were mixed with bark to achieve an initial moisture content of 60%, resulting in a recipe consisting of 1.09 kg of bark per kg of biosolids on a dry basis. Four reactors (treatments) were run with C:N ratios of 107 (control; no N supplement), 55, 29, and 18. Each treatment was replicated three times. Sulfur coated urea was used as the N supplement. Parameters monitored included C:N ratio, N recovery, material compaction, temperature, qualitative odor observations, and volatile solids reduction. The relative microbial activity was observed in-directly using volatile solids removal and the relative heat generation data. The data showed a strong negative linear relationship between C:N ratio and relative heat generation (r²=0.98) and between C:N ratio and volatile solids removal (r²=0.84 for all four treatments; and r²=1.0 for C:N = 29 to 107). The data also showed a strong nonlinear relation between N retention and C:N ratio (% retention = 101(1-0.92C:N); r² = 0.71; n = 12). Qualitative odor observations and N losses suggested that a C:N ratio of 18 was too low, therefore a performance comparison was made between the C:N-107 and the C:N-29 treatments. It was observed that the mean volatile solids removal was 28.6% higher in the C:N-29 treatments as compared to the C:N-107 control. While this difference is significant from a bench-scale perspective, the authors question the practical significance of the difference and recommend further investigation.     

Using a Biocell to Measure Effect of Compressive Settlement on Free Air Space and Microbial Activity In Windrow Composting

This paper describes the first equipment developed to include compressive loads in a physical model of the composting environment. This new type of composting reactor was named a biological load cell, or biocell for short. Our hypothesis was that the exclusion of compressive settlement in existing physical models may lead to errors if the data is used to design full-scale windrow composting facilities. Municipal biosolids were mixed with three organic amendments (wood chips, straw, and leaves) to yield mixture moisture contents of 55%. Compressive settlement analyses were completed by subjecting the mixtures to loads of 0, 4.3, 8.6, and 12.9 kPa using biocells. The effect of compressive settlement on microbial activity was investigated using the biosolids:leaf mixture under loaded (12.9 kPa) and unloaded conditions. The settlement behavior of all three mixtures was found to fit established soil compaction equations and new equations were developed to represent the vertical free air space (FAS) and bulk density profiles in composting systems. The FAS profiles indicated that existing physical models do not simulate the FAS conditions within a composting matrix and significant differences in microbial activity were observed between loaded and unloaded biocells. The microbial activity differences were attributed to the reduced FAS within the loaded biocells, which, in consequence, lead to lower pore space oxygen concentrations. It proved difficult, however, to simulate the air flow regime within a windrow composting matrix. To further develop the biocells, there is a need to investigate the in-situ stress conditions and natural draft ventilation rates of full-scale windrow systems. While further work is required to perfect the biocells as a physical model of the windrow composting environment, it has demonstrated its potential use for FAS analysis and as a standard bulk density apparatus. Using biocells, it is recommended that FAS curves be developed for a wide range of feedstock recipes. The biocell apparatus could also be developed as a standard bulk density test apparatus. Other important conclusions drawn from the work include: leaves should not be used as a bulking agent; wood chips showed superior bulking properties and are recommended for use in very high (3.7 m) windrows; straw showed intermediate bulking properties and should not be used for high windrows without further investigation; for all materials, compaction occurred rapidly after each incremental load, suggesting that windrow turning will do little to alleviate a low FAS problem associated with an incorrect composting recipe.     

Food intake of the laying hen following crop loads of maize oil and other nutrients

The metabolisable energy (ME) of the diet of laying hens at an ambient temperature (Ta) of 20 degrees C was abruptly changed from 10.9 MJ/kg to 12.9 MJ/kg, or vice versa. Food intake during the next 14 d was significantly reduced by the low ME diet and was increased by the high ME diet, that is, the expected compensatory changes in food intake did not occur. Laying hens given the same change of diet as above but kept at 32 degrees C did not show any change in food intake within 14 d. Thus ME intake increased with the high ME diet and decreased with the low ME diet. Daily doses of 10 ml maize oil/kg body weight given directly into the crop of laying hens at a Ta of 20 degrees C, resulted in an immediate, significant, reduction of food intake such that total ME intake remained the same as with normal feeding. Daily doses of 3 ml maize oil/kg, given as before, resulted in an immediate, significant, reduction in food intake at a Ta of 20 degrees C but at a Ta of 32 degrees C food intake remained unchanged; consequently daily ME intake increased. Loading the crop with glucose or sucrose, at Ta 20 degrees C, in quantities which provided a similar ME as 3 ml maize oil/kg, reduced food intake but the adjustment was less precise and daily ME intake increased. Loading with glycerol or protein hydrolysate decreased both food and ME intake. Crop loads of starch were as effective as maize oil in bringing about a significant and compensatory reduction of food intake. Similar volumes of water or liquid paraffin placed in the crop did not affect food or ME intake. A similar weight or cellulose placed in the crop reduced food and ME intake.     

Effect of changes in dietary energy intake and environmental temperature on heat tolerance in the fowl

The improvement in heat tolerance acquired during the acclimatization of laying hens to intermittent heat stress was lost or considerably reduced when energy intake increased following the addition of maize oil to the diet. The oxygen consumption (VO2) of acclimatised hens increased after the addition of maize oil to the diet. Reducing the environmental temperature (Ta) from 30 degrees to 10 degrees C prevented the development of acclimatization if the heat stress commenced soon after the change of Ta; if the heat stress commenced 5 weeks after the change of Ta acclimatization took place normally. Reducing the Ta from 30 degrees to 10 degrees C resulted in an increased VO2 and food intake. The administration of triiodothyronine increased VO2 and reduced the heat tolerance of acclimatised hens. It is concluded that heat tolerance, despite being reinforced by regular exposure to heat stress, remains susceptible to changes in energy metabolism brought about by dietary or environmental means.     

Book reviews

Nomina Anatomica Avium. An Annotated Anatomical Dictionary of Birds, edited by J. J. Baumel. Academic Press Inc. (London) Ltd, 1979. 637 pp., illustrated. Price £28.00. ISBN 0 12 083150 3.

Form and Function in Birds, Volume 1, edited by A. S. King and J. McLelland. Academic Press Inc. (London) Ltd, 1980. 459 pp, illustrated. Price £28.00. ISBN 0 12 407501 0     

Successful Treatment of Disseminated Nocardiosis Caused by Nocardia veterana in a Dog

A 5‐year‐old male castrated Lhasa Apso cross was evaluated for a 1‐month history of inappetence, lethargy, gagging, and progressive right thoracic limb lameness. Synovial fluid analysis revealed nonseptic suppurative inflammation, and a diagnosis of immune‐mediated polyarthritis (IMPA) was made. After 3 months of treatment with prednisone and later cyclosporine, the dog developed multiple firm cutaneous and subcutaneous masses and a focal mass within the jejunum. Cultures of blood, urine, skin lesions, and the jejunal mass identified Nocardia veterana by matrix‐absorption laser desorption ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF MS) and allowed for earlier identification of the organism compared to more traditional secA1 gene sequencing. Immunosuppressive drug treatment was discontinued, and the dog was treated for 3 months by administration of trimethoprim‐sulfamethoxazole (TMS). No recurrence of clinical signs was reported 1 year later. This case report highlights the clinical utility of MALDI‐TOF MS, particularly for the rapid identification of slow‐growing, fastidious organisms.