Einfluß von nutritiven Faktoren während einer Lernphase auf die Entstehung eines spezifischen Lysinhungers bei Legehennen

Bei 72 einzeln gehaltenen Legehennen wurde die Fähigkeit zur selektiven Lysinaufnahme überprüft. 2 unterschiedliche Alleinfutter auf der Basis von Federmehl (A) oder Maiskleber (B), aber mit dem gleichen defizitären Lysingehalt (0,36%), wurden während einer zweiwöchigen Lernphase jeweils an eine Hälfte der Tiere verfuttert. Anschließend wurden beide Vorbehandlungen in je 4 Gruppen geteilt, und eine der Mangelrationen und eine mit Lysin bedarfsgerecht supplementierte Ration (A+ bzw. B+, 0,64%) in folgenden Kombinationen zur Selbstauswahl über 14 Tage angeboten: A/A+, A/B+, B/A+ und B/B+. Über den prozentualen Rationsanteil am Gesamtfutterverzehr wurde die selektierte Lysinaufnahme ermittelt. Mit beiden Mangelrationen wurde eine Anorexie und in Folge eine Leistungsdepression ausgelöst, die jedoch bei B stärker ausgeprägt war. Die lysinangereicherte Ration wurde in fast allen Fällen innerhalb weniger Tage signifikant und stetig zunehmend bevorzugt, was für einen erlernten Lysinappetit bzw. -hunger spricht. Gleichzeitig wurde eine deutlichere Präferenz für die Federmehlration beobachtet, die bei Gruppe A/B+ nach B sogar zu einer Ablehnung der ergänzten Maiskleberration führte. Vertrautheit bzw. Neuartigkeit und sensorische Qualitäten einer Ration spielten neben den physiologischen Effekten eine bedeutende Rolle bei der Selbstauswahl. Die komplexen Wechselbeziehungen zwischen Futter, hedonistischen Komponenten und Erfahrung für die Entwicklung eines spezifischen Hungers wurden diskutiert.     

Cortisol and corticosterone plasma levels in different Psittaciformes]

Plasma cortisol and corticosterone levels were measured in macaws, African Grey Parrots, Amazon Parrots and budgerigars using a RIA after preliminary cleaning. As in other avian species, the plasma contains predominantly corticosterone.     

Effects of Carbon Dioxide Exposure on Intensively Cultured Rainbow Trout Oncorhynchus mykiss: Physiological Responses and Fillet Attributes

Rainbow trout Oncorhynchus mykiss (261.6 × 24.7 g initial weight, mean × SEM) at 13.1 × 0.2 C were exposed for 94 d to one of three CO₂ treatments: control (22.1 × 2.8 mg/L), medium (34.5 × 3.8 mg/L), or high (48.7 × 4.4 mg/L). Trout were checked daily for survival, and fish were sampled at 0, 28, 56, and 84 d for physiological responses, growth, and fillet quality assessments. Trout were also challenged to a 15-min crowding stress at 93 d to assess their ability to initiate a stress response during hypercapnia. Chronically exposed trout showed nearly 100% survival through 84 d exposure (1 of 1,500 fish died). Growth and physiological results showed that increasing elevated CO₂, concentrations result in corresponding decreased growth rates and CO₂specific physiological parameters: The medium and high CO₂ treatments had significantly slower growth and subsequently smaller fish by 84 d. Exposed trout also showed significantly ( P < 0.05) decreased plasma chloride for medium and high CO₂ treatments compared to the control from 28 through 84 d. Decreased growth and smaller fish in the medium and high CO₂ treatments resulted in correspondingly smaller fresh and smoked fillet weights. Chronic CO₂ exposure did not result in notable changes in ultimate muscle pH. Exposure to 15-min crowding stress at 93 d resulted in significant changes in hematocrit, plasma cortisoI, glucose, and chloride for all treatment groups. CO₂-specific changes were detected in hematocrit, plasma cortisoI, and plasma chloride responses following the 15-min crowding stress.     

Pilot Production of Hatchery-Reared Summer Flounder Paralichthys dentatus in a Marine Recirculating Aquaculture System: The Effects of Ration Level on Growth, Feed Conversion, and Survival

Pilot‐scale trials were conducted to evaluate growout performance of hatchery‐reared summer flounder fingerlings in a state‐of‐the‐art recirculating aquaculture system (RAS). The outdoor RAS consisted of four 4.57‐m dia × 0.69‐m deep (vol. =11.3 m³) covered, insulated tanks and associated water treatment components. Fingerlings (85.1 g mean initial weight) supplied by a commercial hatchery were stocked into two tanks at a density of 1,014 fish/tank (7.63 kg/m³). Fish were fed an extruded dry floating diet consisting of 50% protein and 12% lipid. The temperature was maintained between 20 C and 23 C and the salinity was 34 ppt. Under these conditions, growth, growth variation (CV_wt), feed utilization, and survival of fish fed to 100% and 82% of a satiation rate were compared. Due to clear changes in growth patterns during the study, data was analyzed in three phases. During phase 1 (d 1–d 196), fish showed rapid growth, reaching a mean weight of 288 g ± 105 and 316 g ± 102, with a CV_wt of 0.36 and 0.32 and FCR's of 1.38 and 1.36 in the subsatiation and satiation groups, respectively. During phase 2 (d 196–d 454), fish displayed slower growth reaching mean weights of 392 g ± 144 and 436 g ± 121, with a CV_wt of 0.37 and 0.28, and increasing FCR's of 3.45 and 3.12 in the subsatiation and satiation groups, respectively. During phase 3 (d 454–d 614), fish showed little growth reaching mean weights of 399 g ± 153 and 440 g ± 129, with a CV_wt of 0.38 and 0.29 in the subsatiation and satiation groups, respectively. Over the entire growout period (d 1–d 614), feed conversion ratios were 2.39 and 2.37 and survival was 75% and 81 % in the subsatiation and satiation treatments, respectively. The maximum biomass density reached during the study was 32.3 kg/m³. The satiation feed rate was superior to the 82% satiation rate, since it maximized growth rates, with no effect on FCR. The higher CV_wt in the subsatiation group suggests increased competition for a restricted ration led to a slower growth with more growth variation. The decrease in growth in phases 2 and 3 was probably related to a high percentage of slower growing male fish in the population and the onset of sexual maturity. This study demonstrated that under commercial scale conditions, summer flounder can be successfully grown to a marketable size in a recirculating aquaculture system. Based on these results, it is recommended that a farmer feed at a satiation rate to minimize growout time. More research is needed to maintain high growth rates through marketable sizes through all‐female production and/or inhibition of sexual maturity.     

Heterologous Radioimmunoassay for Llama and Alpaca Luteinizing Hormone with a Monoclonal Antibody,an Equine Standard and a Human Tracer

A radioimmunoassay for llama and alpaca LH was developed using a human I¹²⁵LH tracer from a commercial kit, equine LH diluted in human LH free serum as standard, and a monoclonal antibody (518B7) specific for LH but with low species specificity. A 60-min delay in the addition of the tracer and overnight incubation gave a sensitivity of 0.8 μg L⁻¹. The intra-assay coefficient of variation was 37% at 1 μg L⁻¹, declined to 15% at 4 pg L⁻¹ and was below 6% for concentrations up to 32 μg L⁻¹. The inter-assay coefficients of variation for 3 control samples were 20% (2.8 μg L⁻¹), 16% (7.1 μg L⁻¹) and 9.8% (19 μg L⁻¹). In an attempt to increase sensitivity, all tubes were preincubated for 4 h at room temperature before adding the tracer, and the sample volume was increased from 50 μL to 100 μL· (in the standard curve the increased volume was compensated for by human LH free serum). With this protocol, the assay sensitivity was 0.5 μg L⁻¹. The assay was validated clinically and demonstrated increased concentrations of LH after mating in llamas and alpacas. Furthermore, the assay was used to monitor LH responses to a single dose of GnRH in llamas (adult males and females at different ages).