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.     

A formal method of determining the dietary amino acid requirements of laying‐type pullets during their growing period

1. The amino acid requirements of laying type pullets during the growing period can be estimated by measuring the growth of different components of the body and making use of nutritional constants that define the amount of each amino acid that is required for the production of the tissues being formed.

2. In this experiment, carcase analyses of each of three breeds of pullets were conducted at weekly intervals throughout the growth of the pullets, to 18 weeks of age. Measurements were made of body weight, gut‐fill and feather weight, and chemical analyses consisted of water, protein, lipid and ash measurements of both the body and the feathers. Each age group comprised 10 birds of each breed.

3. Gompertz functions accurately estimated the growth of both body protein and feather protein, to 18 weeks of age, from which the rate of growth of these two components of the body could be estimated. The mature weight of pullets was overestimated by the Gompertz growth curve, which may indicate that a pullet ceases to increase in body protein content once sexual maturity has been reached.

4. Using allometric relationships between the chemical components of the body and of feathers, all the components of growth could be estimated from the growth of body protein and feather protein. These components were then added together to determine the growth rate of the body as a whole.

5. The daily amino acid requirements for 4 functions were calculated, namely, those for the maintenance of body protein and feather protein, and for the gain in body protein and feather protein. These requirements were then summed to determine the requirement of pullets on each day of the growing period.

6. Using the ‘effective energy’ system, the amount of energy required by these pullets was calculated for each day of the growing period, from which the desired daily food intake of the pullets could be predicted. By dividing the amino acid requirement by this daily food intake it was possible to determine the concentration of amino acids that would be needed in the diet in order to meet the requirements of a pullet.

7. The results indicate that the ratio between the requirement for lysine and for methionine and cysteine changes dramatically during the growing period, negating the concept of a fixed ratio between all the amino acids during growth.

8. The above process is the first step in determining the optimal feeding programme for a population of pullets of a given genotype. The constraining effects, of the diet being offered and of the environment in which the pullets are housed, on the food intake and growth rate of each pullet have to be estimated, and such a theory can then be expanded to include all the individuals in the population. Only by the use: of simulation models can all these constraining effects be considered simultaneously.     

An improved ferritin assay for canine sera

An improved serum ferritin assay for canine serum has been developed. It uses two monoclonal antibodies in a sandwich arrangement. Serum ferritin can be determined on undiluted canine sera with this assay. The recovery of ferritin added to canine serum ranged from 98 to 106%, the within-assay coefficient of variability was 3.3 to 4.5%, and the assay-to-assay variability was 9.8 to 10.2%. Serum ferritin from 61 apparently healthy dogs had a geometric mean of 252 ng/ml, with a range of 80 ng/ml to 800 ng/ml.     

Recognition of sedimentary characteristics in soils by size-shape analysis

Size-shape analysis has been applied to two soils of alluvial origin and to an in-situ soil over granite. Elongation function curves for the granitic soil show that its quartz grains become increasingly equant with increasing size. The coarser particles of the alluvial soils, by contrast, become less equant and more elongated with increasing grain size — a characteristic of the framework population of bed-load sediments.The method appears promising for helping to distinguish transported from in-situ parent materials.     

Comparison between vegetation indices for detecting spatial and temporal variabilities in soybean crop using canopy sensors

Precision Agriculture - Crop monitoring through remote sensing techniques enable greater knowledge of average variability in crop growth. Canopy sensors help provide information on the variability...     

Soil properties and the macrofauna community in abandoned irrigated rice fields of northeastern Argentina

This study compared soil physical, chemical, and biological characteristics between natural grassland and recently abandoned rice fields in order to identify those variables that might explain the observed increase of Camponotus punctulatus anthills in abandoned rice paddy fields from Northern Argentina. Mainly due to a reduction of macropores and mesopores, overall porosity decreased by around 6% and bulk density was about 7% greater, in the 0- to 10- and 10- to 20-cm layers of the abandoned rice fields. Carbon and nitrogen content from organic matter increased (29% and 41% respectively for the 0- to 20-cm horizon) during cultivation but decreased (38% and 24%) 2 years after the last rice harvest. Forty percent of natural grassland-organic matter and 30% of abandoned rice-organic matter mineralized in less than 2 years. There was a different community structure between the abandoned rice fields and the undisturbed natural grassland and only a 20.6% (i.e. only 19 species from a total of 92) overlap in species composition. The abundance of macrofauna was greater in abandoned rice fields (2,208 individuals m^–2) in comparison to natural grasslands (288 ind m^–2) due to higher densities of small earthworms and Camponotus punctulatus ants; however, the Shannon index showed lower values in comparison to natural grasslands. Earthworms and C. punctulatus in the abandoned rice fields showed a change in their ¹³C signature indicating a switch in diet from natural grassland organic matter (C4) to organic matter from rice (C3). Our results indicate that the effects of rice cultivation practices did not seem to produce any physical or trophic limitations to recolonization by the macrofauna. It seems that changes in overall soil conditions have favored a change in the construction behavior of C. punctulatus which, in combination with population increases, could explain the explosion in number of anthills.