Economic Assessment of Alternative Aquaculture Aeration Strategies

Oxygen depletion is a serious problem for the catfish industry, especially as producers attempt to increase their production intensity. Aeration, either emergency or continuous, is the most common method used to address oxygen depletion.
A risk-programming model using Target MOTAD methodology was developed to study the aquacultural producer's aeration decision-making process. Effects of stocking rate, aeration yield response and availability of labor, capital and electricity on the selection of aeration strategy were analyzed.
Continuous aeration with electric paddlewheels was most often selected as the best aeration strategy. However, as farmers become increasingly concerned with financial risk, they apply continuous aeration with pump sprayers first, then no aeration and lastly emergency aeration with tractor-powered paddlewheels. Emergency aeration was only used when: 1) electricity was not available and the producer desired a highly conservative financial strategy, and 2) the relative efficiency of continuous aeration in the field was dramatically reduced from experimental results.     

Ergovaline does not alter the severity of ryegrass staggers induced by lolitrem B

AIM: To investigate a possible interaction between lolitrem B and ergovaline by comparing the incidence and severity of ryegrass staggers in sheep grazing ryegrass (Lolium perenne) containing lolitrem B or ryegrass containing both lolitrem B and ergovaline.

METHODS: Ninety lambs, aged approximately 6 months, were grazed on plots of perennial ryegrass infected with either AR98 endophyte (containing lolitrem B), standard endophyte (containing lolitrem B and ergovaline) or no endophyte, for up to 42 days from 2 February 2010. Ten lambs were grazed on three replicate plots per cultivar. Herbage samples were collected for alkaloid analysis and lambs were scored for ryegrass staggers (scores from 0–5) weekly during the study. Any animal which was scored ≥4 was removed from the study.

RESULTS: Concentrations of lolitrem B did not differ between AR98 and standard endophyte-infected pastures during the study period (p=0.26), and ergovaline was present only in standard endophyte pastures. Ryegrass staggers was observed in sheep grazing both the AR98 and standard endophyte plots, with median scores increasing in the third week of the study. Prior to the end of the 42-day grazing period, 22 and 17 animals were removed from the standard endophyte and AR98 plots, respectively, because their staggers scores were ≥4. The cumulative probability of lambs having scores ≥4 did not differ between animals grazing the two pasture types (p=0.41).

CONCLUSIONS AND CLINICAL RELEVANCE: There was no evidence for ergovaline increasing the severity of ryegrass staggers induced by lolitrem B. In situations where the severity of ryegrass staggers appears to be greater than that predicted on the basis of concentrations of lolitrem B, the presence of other tremorgenic alkaloids should be investigated.     

Quantifying the aging response and nutrient composition for muscles of the beef round

The objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. Forty USDA Select and 40 Premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-wk period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: adductor, gastrocnemius, gracilis, pectineus, and superficial digital flexor. Each pair of muscles was cut into 7 steaks and randomly assigned to 1 of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 d, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A 2-way interaction was detected (P < 0.05) between individual muscle and postmortem aging period. The WBSF of all muscles except the superficial digital flexor decreased with increased time of postmortem aging. Quality grade did not affect (P > 0.05) WBSF values for the adductor, gastrocnemius, pectineus, and superficial digital flexor muscles. Exponential decay models were used to predict the change in WBSF from 2 to 28 d postmortem (aging response). The adductor, gastrocnemius, Select gracilis, Premium Choice gracilis, and pectineus required 21, 14, 23, 23, and 25 d, respectively, to complete the majority of the aging response. To determine the nutrient composition of the adductor, gastrocnemius, gracilis, pectineus, semimembranosus, and superficial digital flexor, bottom and inside rounds were collected from 10 USDA Select and 10 Premium USDA Choice carcasses and fabricated into the respective muscles, cut into 2.54-cm cubes, frozen (-20°C), and then homogenized. The adductor, gracilis, pectineus, semimembranosus, and superficial digital flexor were analyzed for DM, moisture, CP, and ash percentages. All muscles were evaluated for total lipid, fatty acid, and cholesterol composition. When quality grades were combined, all muscles fell into the extra lean or lean categories specified by USDA guidelines. Results of this study illustrate the potential for Beef Value Cuts of the round to be sold in food service operations and retail stores with marketing emphasis being placed on the exceptional leanness and acceptable tenderness of these cuts.     

Apoptosis in the Antral Follicles of Swamp Buffalo and Cattle Ovary: TUNEL and Caspase-3 Histochemistry

The present study was carried out to investigate the pattern of apoptosis in the healthy antral and atretic follicles of Philippine swamp buffaloes (BU) in comparison with Holstein-Friesian (HF) cows. Paraffin sections of healthy follicles and various stages of atretic follicles were stained using the terminal deoxynucleotidyl transferase (TdT)-mediated biotinylated deoxyuridine triphosphates (dUTP) nick end-labelling (TUNEL) method to detect DNA fragmentation and cleaved caspase-3 antibody to detect cells committed to undergo apoptosis. Five equidistant areas of a follicle were counted for the presence of TUNEL- and caspase-3-positive cells. Healthy follicles of BU and HF contained no TUNEL-positive cells in the granulosa and theca layer but showed some caspase-3 positivity. The granulosa layer of advanced atretic follicles showed a significantly higher frequency of caspase-3 positivity than the healthy and early atretic follicles in both breeds. The frequency of caspase-3-positive cells of BU was significantly higher than HF in the granulosa layer of healthy, early atretic and advanced atretic follicles. In the theca interna layer, BU and HF showed a significantly lower and higher frequency of TUNEL-positive cells in the late atretic follicles compared with advanced atretic follicle, respectively. However, the frequency of caspase-3-positive cells of both BU and HF in the late atretic follicles was significantly higher than the advanced atretic follicles in the theca interna layer. These results indicate that caspase-3 and DNA fragmentation is involved in the buffalo ovarian apoptotic process.     

A Hierarchical Perspective to Woody Plant Encroachment for Conservation of Prairie-Chickens

Encroachment of Great Plains grasslands by fire-sensitive woody plants is a large-scale, regional process that fragments grassland landscapes. Using prairie grouse (Tympanuchus spp.) of conservation concern, we apply hierarchy theory to demonstrate how regional processes constrain lower-level processes and reduce the success of local management. For example, fire and grazing management may be locally important to conservation, but the application of fire and grazing disturbances rarely cause irreversible fragmentation of grasslands in the Great Plains. These disturbance processes cause short-term alterations in vegetation conditions that can be positive or negative, but from a long-term perspective fire maintains large tracts of continuous rangelands by limiting woody plant encroachment. Conservation efforts for prairie grouse should be focused on landscape processes that contribute to landscape fragmentation, such as increased dominance of trees or conversion to other land uses. In fact, reliance on local management (e.g., maintaining vegetation structure) to alter prairie grouse vital rates is less important to grouse population persistence given contemporary landscape level changes. Changing grass height, litter depth, or increasing the cover of forbs may impact a few remaining prairie-chickens, but it will not create useable space at a scale relevant to the historic conditions that existed before land conversion and fire suppression.