Responses to Pathogen-induced Disturbance: Decomposition, Nutrient Availability, and Tree Vigour

In the Oregon subalpine zone, extensive dieback occurs in relativelypure stands of 150 to 250-year-old mountain hemlock growingon very infertile soils. Tree death is caused by a root-rotfungus, Phellinus weirii. Young trees that become establishedfollowing death of the original forest are apparently not reinfectedby the pathogen until 80–140 years later. whereon mortalityoccurs again. We examined the effects.of this natural disturbanceand subsequent regrowth on a number of ecosystem characteristics. Decomposition rates and nitrogen availability measured by insitu exchange resins increased in the zones of young regrowth,but dropped to values common for old growth as the forest agedand the canopy closed. Phosphorus and potassium accumulationon exchange resins showed trends opposite to nitrogen, and mayhave been associated with changes in biomass. Increased nitrogenconcentrations and decreased lignin concentrations in fine rootsin the zone of young regrowth suggested improved tree nutritionunder conditions of higher N availability and lower leaf areaindex. Tree vigour, estimated as wood production per unit leafarea, also was significantly increased in the zones where youngforests grew. Circumstantial evidence suggests that increasesin nutrient availability and light following death of the matureforest improved photosynthesis leading to increased resistanceof young trees against infection by the pathogen.     

The nutritional evaluation of dried earthworm meal (Eisenia foetida, Savigny, 1826) included at low levels in production diets for rainbow trout, Salmo gairdneri Richardson

Abstract. Dried earthworm meal derived from the species Eisenia foetida was nutritionally evaluated as a replacement for herring meal in production diets from rainbow trout, Salmo gairdneri Richardson. Increasing levels of dried E. foetida meal, from 5 to 30% by weight, were included in the diet and the response of fish fed these diets was compared to fish fed a control diet without earthworm meal inclusion. There was no evidence of any adverse effect on the growth performance or feed utilization efficiency of fish fed diets containing these low levels of dried E. foetida meal. There was. however, a significant increase in the whole carcass lipid content of fish fed diets containing 5. 10 and 20% dried E. foetida meal. Concent rations of iron, zinc, lead, copper and cadmium within the whole fish carcass were not significantly elevated as a result of including these low levels of the dried E. foetida meal in diets for rainbow trout.     

Juvenile growth and survival of heat-shocked triploid hybrid saugeyes, Stizostedion vitreum × S. canadense

Triploid hybrid saugeyes may be a desirable stocking alternative because diploid saugeyes are fertile and can compromise the genetic integrity of parental stocks. Four groups of saugeye eggs were heat-shocked 5 min after fertilization for 15 min at 31 °C, which resulted in an 86.7 ± 9.4% triploidy rate and 57.8 ± 24.3% survival to the eyed-stage. Heat shocked and control saugeyes were stocked in two ponds for 40 days at 395 000 ind. ha^–1. Mean length and weight of triploid and heat-shocked diploid saugeyes were greater ( P  < 0.01) than unshocked diploid saugeyes. Survival of heat-shocked saugeyes (22.4%) was lower than unshocked saugeyes (94.7%). Heat-shocked fish ( n =25 851) harvested from ponds were stocked for 153 days in O'Shaughnessy Reservoir, Ohio, USA. Triploids were 34 mm shorter and weighed 41 g less than heat-shocked diploids ( P  < 0.01). Mean length and weight of triploids were comparable with unshocked diploids elsewhere in Ohio.     

The welfare significance of the castration of cattle: A review

Castration is an ancient husbandry procedure used to produce docile cattle for draught work, to reduce unwanted breeding, and to modify carcass quality. All the physical methods used to castrate cattle have side-effects and cause pain. The plasma cortisol response to castration using Burdizzo clamps and, by inference, the acute pain experienced, is less than that caused by surgical, rubber-ring or latex-band castration. The cortisol response may be influenced by the age of the animal castrated, but this has not been well defined. Local anaesthesia virtually eliminates the cortisol response, and thus the acute pain, caused by rubber-ring or latex-band castration, but needs to be combined with a systemic analgesic such as the non-steroidal anti-inflammatory drug ketoprofen to eliminate the cortisol response to Burdizzo or surgical castration. When used alone, ketoprofen sometimes reduces the cortisol response to Burdizzo or surgical castration but may need to be accompanied by local anaesthesia to eliminate the pain-induced behaviour seen during the castration process itself. Thus, pharmacological methods are available to virtually eliminate the acute pain experienced by calves during the 12 h following castration. The use of these methods is an additional cost for farmers and may be limited by the availability of drugs for farmers to use and the scarcity of veterinarians in farm animal practice.     

Growth Hormone Receptors in the Porcine Testis During Prepuberty

Supplementation of exogenous growth hormone (GH) during prepuberty advances onset of spermatogenesis in boars, but the mechanism of action is unknown. The present study is an investigation of the presence and characteristics of testicular growth hormone receptors (GHR). A total of 36 boars were castrated, three boars every 10 days, between the ages of 10 and 120 days. Testicular membrane preparations of 10, 20, 30, 50, 70, 100 and 120‐day‐old boars were used to determine ¹²⁵I‐bGH binding and Scatchard analysis. Liver from a 60‐kg barrow was used for comparison. Specific ¹²⁵I‐bGH binding to testicular membrane preparations occurred in all age groups with the exception of 20‐day‐old boars at levels of 30–40% of liver binding. At 30 days of age the unlabelled bGH at 1.1 ng/tube achieved half maximal inhibition (ID₅₀). Results of Scatchard analysis indicated a single class of binding sites. Binding affinity was 2.89 × 10⁹m with a binding capacity of 12 fmole/mg membrane protein. The results from this study suggest that GH may act directly on the cells of the prepubertal boar testis.     

Acute cortisol responses of lambs castrated and docked using rubber rings with or without a castration clamp

Objective To measure the plasma cortisol response in lambs castrated and docked by three different methods (ring castration and tail docking, ring and clamp castration and tail docking; ring and clamp castration and ring tail docking) for 4 h after treatment.
Design A physiological study with controls.
Procedure A rubber ring was applied to the scrotum. Then the castration clamp was placed, distal to the ring, on each spermatic cord such that there was no overlap of the crush lines.
Results There were no differences in the cortisol secretion of the lambs castrated and tail docked by the ring only and by the ring plus castration clamp methods. Using the castration clamp in addition to the ring on the tail had no effect on cortisol secretion.
Conclusions Using the castration clamp did not appear to reduce the cortisol response to ring castration and docking, as demonstrated elsewhere, because the areas of uncrushed tissue between the two castration clamp crush lines allowed nociception from ischemic scrotal tissue to be transmitted cranially via undamaged nerve fibers.