Effects of animal and plant protein diets on growth of Indian major carp (Labeo rohita Ham.) fingerlings

An experiment was conducted with Labeo rohita fingerlings in an indoor static fish rearing water system of glass made aquaria. Five experimental diets A, B, C, D and E were formulated containing 33% dietary protein level in five treatments each having two replicates containing 12 fingerlings of mean total initial weight of 13.00±0.2g. Sixty days of feeding trial in this experiment showed that fish fed on diet 'A' containing fish meal and diet 'E' containing mixed plant sources protein had significantly highest and lowest growth respectively. However, no significant difference of growth was found in fish fed on diets C and D containing meat and bone meal, and mix of animal protein source diets respectively. The result showed that the apparent protein digestibility (APD) of diets 'A' and 'E' had significantly best and least values respectively. Food conversion ratio (FCR) and protein efficiency ratio (PER) ranged between 1.37 to 2.17 and 1.38 to 2.18 respectively. On the basis of observed FCR and PER diets 'A' and 'E' produced significantly highest and lowest growth respectively.

Effects of animal-plant protein ratio in extruded and expanded diets on nitrogen and energy budgets of juvenile Chinese soft-shelled turtle (Pelodiscus sinensis Wiegmann)

In this study, we investigated the effects of animal-plant protein ratio in extruded and expanded diets on nutrient digestibility, nitrogen and energy budgets of juvenile soft-shelled turtle (Pelodiscus sinensis). Four extruded and expanded feeds (diets 1-4) were formulated with different animal-plant protein ratios (diet 1, 1.50:1; diet 2, 2.95:1; diet 3, 4.92:1; diet 4, 7.29:1). The apparent digestibility coefficients (ADCs) of dry matter and crude lipid for diet 1 were significantly lower than those for diets 2-4. There was no significant difference in crude protein digestibility among diets 1-4. The ADC of carbohydrate was significantly increased with the increase in animal-plant protein. Although nitrogen intake rate, faecal nitrogen loss rate and excretory nitrogen loss rate of turtles fed diet 1 were significantly higher than those fed diets 2-4, nitrogen retention rate, net protein utilization and biological value of protein in these turtles were significantly lower than those fed diets 2-4. In addition, energy intake rate, excretory energy loss rate and heat production rate of turtles fed diet 1 were also significantly higher than those fed diets 2-4. Faecal energy loss was significantly reduced with the increase in the animal-plant protein ratio. The ADC of energy and assimilation efficiency of energy significantly increased with a higher animal-plant protein ratio. The growth efficiency of energy in the group fed diet 1 was significantly lower than those in the groups fed diets 2-4. Together, our results suggest that the optimum animal-plant protein ratio in extruded and expanded diets is around 3:1.

Effects of the stocking density and body size of the mitten crab (Eriocheir sinensis) on aquatic plant biomass

Experiments in tanks and cages were conducted to examine the effects of stocking density and body size of the Mitten crab (Eriocheir sinensis) on transplanted submersed macrophyte biomass. The early juvenile crab with 7.0 +/-0.6 mm. carapace width (CW) had little effect on plant biomass, regardless of the stocking densities. However, larger crabs (CW: 18.0 +/-2.2,35.0 +/-3.6, and 60.0 +/-5.7 mm) significantly influenced plant biomass, especially at large stocking densities. Predictive models, using crab body size and stocking density, were generated to demonstrate effect of the mitten crab on the changes Of plant biomass. The results indicate that dense mitten crab populations may adversely affect aquatic plant communities, particularly when its animal food resources are scarce.

Defoliation, nitrogen, and competition: effects on plant growth and resource allocation of Cleistogenes squarrosa and Artemisia frigida

Two species, Artemisia frigida Willd. (C-3, semishrub, and dominant on overgrazed sites) and Cleistogenes squarrosa (Trin.) Keng (C-4, perennial bunchgrass, and dominant or codominant on moderately grazed sites) were studied to determine the effects of defoliation, nitrogen (N) availability, competition, and their interactions on growth, biomass, and N allocation in a greenhouse experiment. The main treatments were: two nitrogen levels (NO = 0 mg N pot(-1), N1 = 60 mg N pot(-1)), two defoliation intensities (removing 60% of total aboveground biomass and no defoliation), and three competitive replacement series (monocultures of each species and mixtures at 0.5:0.5). Our results were inconsistent with our hypothesis on the adaptive mechanisms of A. frigida regarding the interactive effects of herbivory, N, and competition in determining its dominant position on overgrazed sites. Cleistogenes squarrosa will be replaced by A. frigida on over-grazed sites, although C. squarrosa had higher tolerance to defoliation than did A. frigida. Total biomass and N yield and N-15 recovery of C. squarrosa in mixed culture were consistently lower than in monocultures, whereas those of A. frigida grown in mixtures were consistently higher than in monocultures, suggesting higher competitive ability of A. frigida. Our results suggest that interspecific competitive ability may be of equal or greater importance than herbivory tolerance in determining herbivore-induced species replacement in semi-arid Inner Mongolian steppe. In addition, the dominance of A. frigida on overgrazed sites has been attributed to its ability to shift plant-plant interactions through (lap colonization, root niche differentiation, and higher resistance to water stress.

Effects of altitude on plant-species diversity and productivity in an alpine meadow, Qinghai-Tibetan plateau

During the growing seasons of 2002 and 2003, biomass productivity and diversity were examined along an altitudinal transect on the south-western slope of Beishan Mountain, Maqin County (33 degrees 43'-35 degrees 16'N, 98 degrees 48'-100 degrees 55'E), Qinghai-Tibetan Plateau. Six altitudes were selected, between 3840 and 4435 m. Soil organic matter, soil available N and P and environmental factors significantly affected plant-species diversity and productivity of the alpine meadows. Aboveground biomass declined significantly with increasing altitude (P < 0.05) and it was positively and linearly related to late summer soil-surface temperature. Belowground biomass (0 - 10-cm depth) was significantly greater at the lowest and highest altitudes than at intermediate locations, associated with water and nutrient availabilities. At each site, the maximum belowground biomass values occurred at the beginning and the end of the growing seasons (P < 0.05). Soil organic matter content, and available N and P were negatively and closely related to plant diversity (species richness, Shannon-Wiener diversity index, and Pielou evenness index).