Comparative regeneration ecology of three leguminous timber species in a Bolivian tropical dry forest

A comparative study of the regeneration ecology ofthree lesser-known leguminous timber species wasconducted in the seasonally dry forests of SantaCruz, Bolivia to determine species regenerationstrategies and make silvicultural recommendationsfor these species. The study included arepresentative from each subfamily of Leguminosae:Anadenanthera colubrina (Vell. Conc.) Benth.(Mimosaceae), Copaifera chodatiana Kunth.(Caesalpinaceae), and Centrolobium microchaeteC. Martius (Fabaceae). After production in themid-late dry season, seeds of all species sufferedhigh (>30%) rates of predation. For seedssurviving predation, Anadenanthera germinatedwithin three days after the first rains and a highgermination capacity (82%), but most seedlings diedfrom inadequate light or during subsequent periodsof drought. Copaifera germinated more slowlybut had high germination capacity (85%). Centrolobium had very low germination capacity(4%) and germinative energy. Most successfulregeneration of Centrolobium occurred viasprouting from damaged roots on or near loggingroads where it had a density of 261 root sprouts/ha.Anadenanthera regenerated best from seedin areas with soil disturbance or burning. Theregeneration of these species will likely increaseunder more intensive logging and/or post-harvestcompetition control treatments in logging gaps. Themore shade-tolerant Copaifera is most suitedto the current regime of light selective logging,but all three species are likely to be responsive topost-harvest competition control treatments. Impacts of controlled and natural fire were mixed,but generally seedling regeneration and growth wereeither not significantly affected or were increasedby fire.     

Ionoregulatory responses to temperature change in two species of freshwater fish

We examined the ionoregulatory responses to temperature changes in two species of freshwater fish that differ in thermal preferences; the stenothermal, cold-water rainbow trout (Oncorhynchus mykiss) and the more eurythermal, warm-water common shiner (Notropis cornutus). We found that rainbow trout maintained constant plasma Na⁺ levels over the entire temperature regime (5–20 °C). Upon transfer from 15 °C (holding temperature) to 5 and 10 °C, rainbow trout experienced a significant drop in Na⁺ uptake (J_in ^Na), but after two weeks J_in ^Na had upregulated to warm temperature levels. Further, Na⁺ efflux (J_out ^Na) fell significantly at the colder temperatures. As a result, trout at the lowest temperatures were still in ion balance. When trout were exercised to exhaustion both O₂ consumption (MO₂) and J_out ^Na rose significantly at all temperatures, but while MO₂ continued to be dependent upon temperature, J_out ^Na was high and constant. In contrast to the trout, common shiners experienced a 20% drop in plasma Na⁺ at 5 °C. Upon exposure to cold temperatures they experienced a reduced J_in ^Na, and showed no signs of acclimation during the subsequent two weeks. Likewise J_out ^Na was constant at all temperatures. These findings raise questions regarding the degree to which fish employ homeostatic mechanisms designed to defend a set- point (i.e., steady-state) osmolarity and ionic composition.     

Plasma and serum concentrations of phenylbutazone and oxyphenbutazone in racing Thoroughbreds 24 hours after treatment with various dosage regimens

The plasma and serum concentrations of phenylbutazone (PBZ) and oxyphenbutazone were measured in 158 Thoroughbred horses after various doses of PBZ wer given. All horses were competing or training at racetracks in various parts of the country. All horses used in the study had not been given PBZ 24 hours before they were placed on a specific dosage schedule. Samples were collected 24 hours after the last PBZ administration. Four grams of PBZ were given daily by stomach tube, paste, or tablet for 3 days. On day 4, 24 hours before sample collection, an IV dose of 2 g of PBZ was given, regardless of the dose and method of administration. The 24-hour PBZ plasma concentrations were 3.51, 6.13, and 6.40 micrograms/ml, respectively. After 2 g of PBZ was administered IV daily for 4 days, the plasma PBZ concentration was 4.16 g/ml; after a single 2-g IV administration, the serum concentration was 0.87 g/ml. Concentrations of oxyphenbutazone were 3.35 (stomach tube), 4.29 (paste), 3.60 (tablet), 3.65 (4-day IV), and 1.11 g/ml (single IV). A significant relationship was not found between the serum and the urinary concentrations at this 24-hour measurement. Split samples sent to various laboratories confirmed the stability of high-performance liquid chromatography as a method of analysis.     

Infectious bovine keratoconjunctivitis: evidence for genetic modulation of resistance in purebred Hereford cattle

A vaccination study was conducted in a herd of purebred Hereford cattle representing 4 selection (genetic) lines. For each of 2 years, half of the cattle were vaccinated with a pilus-enriched Moraxella bovis bacterin. Cows were vaccinated before parturition, and calves were vaccinated at 2 to 3 months of age. None of the cattle was vaccinated for 1 year preceding and 1 year after the 2 years in which cattle were vaccinated. There was a significantly (P less than 0.05) lower percentage of infectious bovine keratoconjunctivitis (IBK) in calves during years cattle were vaccinated than during years cattle were not vaccinated. During years cattle were vaccinated, there were lower percentages of IBK in vaccinated calves when compared with the percentages of IBK in nonvaccinated calves. When calves were compared on the basis of selection lines, regardless of the vaccination group, there were consistent differences in the percentages that developed IBK. Although calves with pigmented and nonpigmented eyes (representing all 4 genetic lines) developed IBK, the genetic line of calves with the most pigmented eyes had the lowest (P less than 0.05) percentage of IBK. Also, across all genetic lines, there was less IBK in pigmented eyes than in nonpigmented eyes. Seemingly, vaccination of dams, before parturition, and young calves reduced the occurrence of severe IBK in a herd situation under natural exposure conditions. The resistance or susceptibility in cattle under good management may be influenced by genetic factors.     

Attenuation of Eimeria species: further characterisation of two lines of Eimeria mitis

The immunogenicity of a 'precocious' and attenuated line (HP10) of Eimeria mitis was studied and the stability of attenuation of two precocious lines was compared with that of an embryo-adapted line. Chicks housed in wire-floored cages and given 1 X 10(5) oocysts of the HP10 line were protected against challenge with the parent Houghton strain and two field strains, but remained partially susceptible to the Durham and one other field strain. However, when chicks were kept in litter pens so that reinfection could occur freely, inoculation with as few as 1 X 10(3) oocysts of the precocious line resulted in complete immunity to both the Houghton and Durham strains for at least five weeks afterwards. The stability of attenuation of the precocious and embyro-adapted lines was examined by relaxing the selection pressures used to produce attenuation and then testing the virulence of the resulting lines. The precocious lines remained attenuated after several consecutive relaxed passages, in contrast to the embyro-adapted line which showed a marked reversion to virulence after six passages in chickens.     

The effect of dietary calcium upon growth rate, food utilisation and plasma constituents in lines of chickens selected for aspects of growth or body composition

1. The effect of increasing dietary calcium from 10.3 to 20 g/kg on 5- to 17-day growth performance and plasma minerals, electrolytes, total protein, albumin and glucose in chickens from 4 lines selected for: high 8-week body weight (W), low abdominal fat (L), high abdominal fat (F) or at random (C) was studied in two experiments. 2. High dietary calcium significantly reduced weight gain and plasma phosphate and potassium but increased food:gain ratio, plasma total calcium, glucose and albumin. 3. Significant correlations were found between plasma total calcium and plasma phosphate (r = -0.5, P less than 0.01), plasma total calcium and protein (r = 0.4, P less than 0.01) and between plasma total protein and albumin (r = 0.55, P less than 0.01). 4. Genotypes differed in their response to dietary calcium content. There was a substantial response in line F but little effect in line L. 5. In contrast to the three other lines, in line F high dietary calcium significantly increased plasma ionised calcium without altering plasma phosphate or total calcium concentration. 6. It was concluded that genetic selection has produced lines which vary in their tolerance to high dietary concentrations of calcium. Birds selected for increased fatness were less tolerant to high dietary calcium than their lean-selected counterparts.     

Suspected lead poisoning in an Amazon parrot

A double yellow headed Amazon parrot (Amazona ochrocephala tresmariae) of unknown age and sex was examined for an acute onset of anorexia, listlessness, central nervous system signs and diarrhea. A tentative diagnosis of lead toxicosis was achieved based on radiographs, clinical pathology and response to therapy. Chelation therapy (Calcium EDTA) and supportive measures resulted in an uneventful recovery.     

A comparison of the oral application and injection routes using the onderstepoort biological products fowl typhoid vaccine, its safety, efficacy and duration of protection in commercial laying hens

This study was undertaken to establish whether the Onderstepoort Biological Products Fowl Typhoid (OBPft) vaccine registered as an injectable vaccine was effective and safe when administered orally to commercial layers. Its efficacy and duration of protection were compared with application by intramuscular injection. Commercial brown layer hens were used as they were found to be highly susceptible to Salmonella gallinarum infections. In the vaccine safety trial birds were euthanased at timed intervals spanning 4 weeks postvaccination. Necropsies were performed and samples were taken and tested. No clinical signs or mortalities could be attributed to the OBPft vaccine nor could active shedding of the vaccine strain be detected. Slight pathological changes were noted with both routes of vaccination; however, these changes were transient, returning to normal within the observation period. The injected groups showed a better serological response with the rapid serum plate agglutination (RSPA) test than the orally vaccinated groups. In the duration of protection trial, birds were challenged at 3-8-week intervals post-vaccination. All unvaccinated birds died. Protection 8 and 16 weeks after vaccination was above 60 %,by 24 weeks after challenge, the vaccine protection was below 30 %. It was found that there was no significant difference (P < 0.05) in the protection offered by either the oral or injected route of vaccination with the OBPft vaccine.