The Effect of Constant and Fluctuating Temperatures on the Confinement-induced Plasma Cortisol Stress Response in Channel Catfish lctalurus punctatus

Abstract.— Initial and confinement-induced changes of plasma cortisol were measured in channel catfish Ictalurus punctatus acclimated to upper and lower constant temperatures for each season, a spring/fall diurnal pattern between 15 and 26 C, and a summer diurnal pattern between 24 and 35 C. In diurnal treatments, temperature changes were achieved in 10 h and held constant for 2 h before reversing the temperature. Fish held in the spring/fall pattern or at a constant temperature of 15 or 26 C revealed no plasma cortisol concentration differences due to acclimation temperature, but hormone concentrations in all groups increased by about 4.5 fold following a 2-h confinement. Fish held on a summer pattern had differences in both the initial cortisol samples and those measured after confinement. Acclimation to a constant 35 C resulted in significantly higher initial cortisol concentrations, but these levels did not increase following confinement. The inability of the fish held at 35 C to respond to the confinement was thought to be due to the constant thermal stress, resulting in an inadequate interrenal reserve. Physiological consequences due to the diurnal physiochemi-cal cycling in ponds needs further attention.     

Evaluation of Various Concentrations of Dietary Protein and Animal Protein for Pond-Raised Channel Catfish Ictalurus punctatus Fed to Satiation or at a Restricted Rate

A factorial experiment was conducted to evaluate effect of dietary protein (28% or 32%), animal protein (0, 3, or 6%), and feeding rate (satiation or >90 kg/ha per d) on production characteristics, processing yield, and body composition of pond-raised channel catfish Ictalurus punctatus . Fingerling channel catfish (average weight: 55 g/fish) were stocked into 60, 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation or no more than 90 kg/ha per d for 147 d. Fish fed at a rate of >90 kg/ha per d consumed about 85% of the amount of feed consumed by fish fed to satiation. Dietary protein did not affect the total amount of feed fed, amount of feed consumed per fish, weight gain, feed conversion efficiency, or fillet protein. Animal protein had no effect on the total amount of feed fed, amount of feed consumed per fish, weight gain, or fillet protein and ash. Fish fed a diet containing 6% animal protein converted feed more efficiently than fish fed diets containing 0% and 3% animal protein. Fish fed to satiation daily consumed more feed, gained more weight, converted the feed less efficiently, and had a higher carcass yield, a higher level of visceral fat as compared to fish fed at a rate of >90 kg/ha per d. Feeding rate had no effect on fillet protein. Results from this study indicated that both a 28% and a 32% protein diet with or without animal protein provided the same growth rate of channel catfish raised in ponds from fingerlings to marketable size if feed is not restricted below a maximum rate of 90 kg/ha per d. Even though there were some interactions among the three factors evaluated, dietary protein levels of 28% to 32% and animal protein levels of 0% to 6% do not appear to markedly affect carcass yield and fillet proximate composition of pond-raised channel catfish.     

Dermatosis associated with Listrophorus gibbus in the rabbit

A dermatosis associated with Listrophorus gibbus, a pelage mite, is described in the rabbit. The case details of four domestic rabbits are described including diagnostic investigations, treatment, and successful recovery.     

Immunohistochemical detection of porcine reproductive and respiratory syndrome virus using colloidal gold.

Two cytopathic agents were isolated on porcine alveolar macrophages following inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine reproductive and respiratory syndrome (PRRS) virus isolates by indirect immunofluorescence using a PRRS virus (PRRSV) specific monoclonal antibody (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold electron microscopy using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral particles. Dark specific cytoplasmic staining of porcine alveolar macrophages infected with both virus isolates could be observed by immunogold silver staining (IGSS) using the specific MAb. This method proved effective in detecting PRRSV antigens in several ethanol-fixed tissues of piglets intranasally inoculated with the supernatants of macrophages infected with each isolate. Immunogold silver staining was also successfully used for the detection of PRRSV antigens on sections of formalin-fixed paraffin-embedded lung tissues and on frozen sections of lungs. The present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.     

Substitution of Soybean Meal with Cottonseed Meal in Pond Feeds for Channel Catfish Reared at Low Densities

Cottonseed meals were evaluted as partial and complete replacements for soybean meal in pond feeds for channel catfish grown at densities of 5,300/ha. The following dietary treatments were used: 1) glanded cottonseed meal (GC) in which ½ of the soybean meal was replaced; 2) glandless cottonseed meal (GLC) in which all of the soybean was replaced, 3) a control feed (C) typical of commercial catfish feeds. The feeding trial was conducted in 0.04 ha earthen ponds for a period of 176 days. Natural prey species were present in all ponds. Final weights and condition factors of fish fed the GC feed were reduced compared to those fed the GLC or C feeds. This response did not appear to be related to dietary gossypol levels. Even though the GLC feed appeared to be deficient in available lysine, final weight and feed conversion of fish fed the GLC feed were equal to those fed the C feed. Possible nutrient contributions of natural food available in the ponds could not be determined. There were no significant differences in feed conversions or dressout percentages of fish regardless of dietary treatment. Fish fed the GLC feed exhibited a higher percentage of fat and lower percentages of moisture, protein and ash (dry weight basis) in edible tissue than fish fed the other feeds. Free gossypol levels in edible fish tissue were below 100 ppm.     

Legg-Calve-Perthes disease in dogs: Genetic aetiology

The incidence of Legg-Calve-Perthes disease among litters with affected individuals is examined for four of the smaller breeds of dog, with special regard to the West Highland white terrier and the Yorkshire terrier. In these two breeds, the incidence is such to indicate monogenic recessive inheritance of the condition. The symbol pd is proposed for the gene. The available evidence suggests a similar aetiology for the miniature poodle and pug.     

Dairy farm wells in Southeastern Minnesota: The relation of water source to milk and milk fat production

Some farmers in Fillmore County, Minnesota, U.S.A., considered that contaminated well water was associated with lowered milk production in their dairy herds. Wells in shallow limestone-dolomite aquifers were easily contaminated by surface water. Fifty Dairy Herd Improvement Association dairies were classified by whether well water originated in deep, protected aquifers or in shallow, easily contaminated aquifers. No statistically significant differences in milk fat production were demonstrated between the two groups before or after the use of linear multiple regression models to control for differences in management practices.