Pyric–Herbivory and Cattle Performance in Grassland Ecosystems

Achieving economically optimum livestock production on rangelands can conflict with conservation strategies that require lower stocking rate to maintain wildlife habitat. Combining the spatial and temporal interaction of fire and grazing (pyric–herbivory) is a conservation-based approach to management that increases rangeland biodiversity by creating heterogeneous vegetation structure and composition. However, livestock production under pyric–herbivory has not been reported. In both mixed-grass prairie and tallgrass prairie, we compared livestock production in pastures with traditional fire and grazing management (continuous grazing, with periodic fire on tallgrass prairie and without fire on mixed-grass prairie) and conservation-based management (pyric–herbivory applied through patch burning) at a moderate stocking rate. Stocker cattle weight gain, calf weight gain, and cow body condition score did not differ (P > 0.05) between traditional and conservation-based management at the tallgrass prairie site for the duration of the 8-yr study. At the mixed-grass prairie site, stocker cattle gain did not differ in the first 4 yr, but stocker cattle gained more (P ≤ 0.05) on conservation-based management and remained 27% greater for the duration of the 11-yr study. Moreover, variation among years in cattle performance was less on pastures under conservation management. Traditional management in mixed-grass prairie did not include fire, the process that likely was associated with increased stocker cattle performance under conservation management. We conclude that pyric–herbivory is a conservation-based rangeland management strategy that returns fire to the landscape without reduced stocking rate, deferment, or rest.     

Response of weed emergence to rate of Vicia villosa Roth and Secale cereale L. residue

Vicia villosa Roth (hairy vetch) or Secale cereale L. (rye) residue at 2 to 4 times the natural field rate reduced seedling emergence of a wide variety of weed species. However, the natural rate of residue was insufficient for control of most weed species. The form of the response of weed emergence to increasing rates of residue varied among species: emergence of some species showed a monotonic decline in response to increasing rates of residue whereas emergence of others increased at low rates before declining at higher rates. In addition to reducing number of seedlings, high rates of residue delayed the date of emergence. Seed size was generally not a good indicator of a species' ability to emerge through residue, although one very large seeded weed, Abutilon theophrasti. was especially insensitive to residue. V. villosa and 5. cereale did not differ greatly in their effect on weeds early in the growing season, but V. villosa decomposed more rapidly and allowed greater emergence later in the season. Effet de résidus de Vicia villosa Roth et de Secale cereale L. sur la levée des mauvaises herbes Des résidus de Vicia villosa Roth (Vesce velue) et de Secale cereale L. (seigle) à 2–4 fois la quan-tité normale réduisaient la levée d'un large spectre de mauvaises herbes. Cependant la quantité normale de résidus était insuffisante pour lutter contre la plupart d'entre elles. La réponse de la levée des mauvaises herbes à des quantités crois-santes de rVsidus différait selon les espèces. Pour certaines, la levée subissait un déclin monotone; pour d'autres, elle augmentait en présence de faible quantités de reésidus puis décroissait pour des quantités plus importantes. Ces dernières réduisaient la levée et la retardaient également. La taille des graines n'était généralement pas un bon indicateur de la capacité des espèces à lever au travers des résidus, bien qu'une trèAs grosse grains, Abutilon theophrasti Medic., était particu-lièrement insensible aux résidus. V. villosa et 5. cereale ne différaient pas beaucoup dans leur effet sur les mauvaises herbes en début de saison, mais V. villosa se décomposait plus rapidement et permettait des levees plus importantes en fin de saison. Wirkung von Emterückständen von Vicia villosa Roth und Secale cereale L. aufdie Keimung von Unkräutern Durch 2- bis 4 fache Ernteräckstände der Be-haarten Wicke (Vicia villosa) und des Roggens (Secale cereale) wurde die Keimung einer großen Zahl von Unkrautarten herabgesetzt. Normale Ernterückstandsmengen behinderten jedoch die Keimung nur unzureichen. Die Art und Weise der Reaktion der Keimung auf höhere Riick-stände war von Art zu Art verschieden: Die Keimung einiger Arten nahm mit zunehmender Menge an Ernterückständen gleichmäßig ab, während sie bei anderen bei niedrigen Mengen anstieg, urn dann bei höheren Mengen abzunehmen. Zusätzlich zur Verringerung der Keimpflanzendichte wurde bei hohen Rück-standsmengen die Keimung verzögert. Die Samengröße war im allgemeinen kein guter Indikator für die Fähigkeit einer Art, durch das Rückstandsmaterial zu keimen, obwohl eine Art mit großen Samen, Abutilon theophrasti, gegenüber diesen Rückständen besonders unempfindlich war. Die Rückstände der beiden Kulturpflanzen zeigten zu Beginn der Vegetationsperiode keine großen Wirkungsunterschiede, aber die Rückstände von Vicia villosa zerfielen schneller und ließen später eine stärkere Keimung zu.     

Hybrid catfish (♂Ictalurus punctatus X ♀Ictalurus furcatus) production: Does mixed-size production make economic sense?

Alternative management strategies will be required to produce hybrid catfish (♂Ictalurus punctatus X ♀Ictalurus furcatus) year-round to provide continuous market supply. Hybrid catfish fingerlings were stocked at 9,880 head/ha singly or in co-culture with sub-marketable (mean weight = 454 ± 16 g) hybrid catfish carried over the winter from a previous year’s multi-size trial. Economic analyses compared cost of production ($/kg of market-size fish produced) and cash flow of single- and multiple-batch production of hybrid catfish for a single- and two-year period. Gross total and marketable yields were significantly greater in the mixed-size treatment as compared to the single-size treatment, in spite of the significantly greater percentage of market-size fish (84%) in the single-size treatment than in the mixed-size treatment (71%). Cost of production ($/kg) was 4% to 10% lower in the multi-size treatment in the single-year analysis, but 18% to 20% lower when the full two-year cycle was assessed. Cash flow and cash flow risk were improved substantially with the multi-size treatment primarily because the overwintered sub-market-size fish from the previous year reached market size three to four months earlier than in the single-size treatment.     

Effect of Processing,Formula and Measurement Variables on Alkaline Noodle Color—Toward An Optimized Laboratory System

A standardized laboratory method for assessing the color potential of flours for yellow alkaline (Cantonese) noodles is needed, especially for evaluating large numbers of small‐scale samples such as found in wheat breeding populations. To develop such a method, a number of processing and formula parameters were varied and judged for optimum level based on 1) discrimination and mean separation of flours, 2) sensitivity to minor variation in the protocol parameter, 3) practicality and simplicity for the technician, and 4) time efficiency. Four flours milled from single‐cultivar grain lots representing two with good and two with poor color potential were made into alkaline noodle sheets varying in thickness of 0.75–2.00 mm, water absorption of 33.0–39.0%, mixing time of 2–6 min, and NaCl levels of 0–4% (all flour weight basis). Commission Internationale de l'Eclairage (CIE) tristimulus color space (L*, a*, b*) values were measured at 0–24 hr using white, yellow, and black background tiles. Noodle sheet side and a dough resting period were examined. The flours themselves were a consistently large, significant source of variation for color, especially lightness (L*). Based on the optimization criteria, a noodle sheet thickness of 1.5–2.0 mm, an optimum to slightly over optimum water absorption (36% for the flours in this study) with some adjustment for protein content and dough handling properties, a mixing time of 4 min, no dough resting period, and 2% NaCl were selected. Color measurement at 24 hr on a white or otherwise light‐colored background tile was judged best using a consistent side of the noodle sheet. Resting doughs for 1 hr slightly improved handling and sheeting characteristics but was not included for time efficiencies.     

Optimizing Tilapia, Oreochromis sp., Marketing Strategies in Nicaragua: A Mixed-integer Transshipment Model Analysis

Tilapia, Oreochromis sp., production has increased in the Central American region in recent years. Yet, commercial tilapia aquaculture has not developed in Nicaragua on the scale that it has in other neighboring countries. Although demand for tilapia products exists, lack of thorough understanding of domestic markets and coordinated production and marketing efforts have hampered the development of a domestic market. The objectives of this study were to quantify domestic marketing costs for tilapia produced in Nicaragua and develop a mixed-integer transshipment mathematical programming model to identify the most profitable marketing alternatives for tilapia farmers. Results suggested targeting primarily outlets with higher sales prices such as restaurants with supplemental production delivered to local supermarkets. The model chooses cities with weekly restaurant demand capable of absorbing the farm's production with excess product sold to alternative outlets. Supply of farm-raised tilapia production in most regions of Nicaragua was insufficient and created problems associated with frequent and dependable deliveries required by higher paying outlets (restaurants and supermarkets). Larger farms will generate greater returns with regular consistent deliveries to higher priced restaurant outlets. Smaller farms with limited production volumes were not able to meet weekly delivery requirements. Biannual deliveries reduced transportation cost and sales price and were not profitable. However, sustaining markets with infrequent deliveries may not be feasible. This analysis provides guidelines for targeting those specific markets that optimize returns to specific farm sizes in specific regions.     

Precambrian sponges with cellular structures

Sponge remains have been identified in the Early Vendian Doushantuo phosphate deposit in central Guizhou (South China), which has an age of approximately 580 million years ago. Their skeletons consist of siliceous, monaxonal spicules. All are referred to as the Porifera, class Demospongiae. Preserved soft tissues include the epidermis, porocytes, amoebocytes, sclerocytes, and spongocoel. Among thousands of metazoan embryos is a parenchymella-type of sponge larvae having a shoe-shaped morphology and dense peripheral flagella. The presence of possible amphiblastula larva suggests that the calcareous sponges may have an extended history in the Late Precambrian. The fauna indicates that animals lived 40 to 50 million years before the Cambrian Explosion.     

Certain physiochemical properties of uterine tubal fluid, follicular fluid, and blood plasma in the mare.

Uterine tubal fluids were collected twice a day from mares for 5 consecutive estrous cycles between March 15 and September 1. Follicular fluids were aspirated from the follicles of exteriorized ovaries of 3 mares between days 2 and 5 of estrus. Uterine tubal fluid and follicular fluid were analyzed for osmolarity, dry matter, total lipids, total free fatty acids, glucose, fructose, and lactic acid. Blood samples were collected (jugular venipuncture) throughout the estrous cycle, and the same physical and biochemical analyses were made on blood plasma. A difference (P less than 0.01) was found for osmolarity between uterine tubal fluids collected during estrus and those collected during anestrus. The osmolarity of uterine tubal fluid during anestrus was greater than that of blood plasma; follicular fluid was similar in osmolarity to blood plasma. The dry matter in blood plasma was greater (P less than 0.01) than that in either uterine tubal fluid or follicular fluid. Cyclic variations in dry matter content were not observed in uterine tubal fluid. Total lipids in blood plasma and follicular were greater (P less than 0.01) than those in uterine tubal bluid. The concentration of total lipid in uterine tubal fluid was similar during estrus and anestrus. Myristic acid (C14:0) in blood plasma and myristoleic acid (C14:1) in uterine tubal fluid were the only free fatty acids that had cyclic variation. The fatty acids in the greatest concentration in uterine tubal fluid and blood plasma were palmitic acid (C16:0) and linoleic acid (C18:2). Concentrations of linoleic acid and stearic acid (C18:0) were greater (P less 0.01) in follicular fluid than in uterine tubal fluid or blood plasma. Only trace amounts of glucose were detected in uterine tubal fluid, whereas a considerable amount of glucose was found in follicular fluid. Fructose was not detected in any of the fluids. Lactic acid concentrations did not differ between estrus and anestrus. Lactic acid concentration was significantly greater (P less than 0.01) in uterine tubal fluids and follicular fluids than in blood plasma.     

Analysis of Catfish Pricing and Market Dynamics: The Role of Imported Catfish

The producer price of catfish is becoming relatively unstable compared to the trend in previous years, necessitating the need for a complete analysis of catfish pricing and market dynamics. An understanding of the price determination mechanisms in the catfish market and the relationships between producer price, domestic processed price, and import price are important because price variability can result in significant financial losses to the domestic catfish industry. This study used a cointegration procedure to examine the long-run relationships between domestic prices of catfish and imported price. Results from unit root and cointegration tests suggest that there is a long-run equilibrium relationship between pairs of these prices. Results from Granger causality tests and error-correction model estimations suggest that the market for domestic frozen fillets plays a significant role in the price determination of imported catfish. A similar relationship is found between producer price and frozen fillet price. Some significant measures that were estimated include a frozen fillet-producer long-run price transmission elasticity of 0.162, a frozen fillet-imported fillet long-run price transmission elasticity of 3.56, and a producer-frozen fillet short-run price transmission elasticity of 0.322. High levels of fillet prices appear to have influenced the level of catfish imports. As long as distributors and restauranteurs do not see a basis for paying a premium for U.S. catfish products, they will continue to purchase the lower-priced imported catfish and consequently imports will continue to increase.