Nondestructive Estimation of Standing Crop and Fuel Moisture Content in Tallgrass Prairie

Accurate estimation of standing crop and herbaceous fuel moisture content (FMC) are important for grazing management and wildfire preparedness. Destructive sampling techniques have been used to accurately estimate standing crop and FMC, but those techniques are laborious and time consuming. Existing nondestructive methods for estimating standing crop in tallgrass prairie have limitations, and few studies have examined nondestructive estimation techniques for FMC in this environment. Therefore, our objective was to develop robust models for nondestructive estimation of standing crop and FMC in tallgrass prairie. We calibrated and validated stepwise multiple linear regression (SMLR) and artificial neural network (ANN) models for standing crop and FMC using data collected in tallgrass prairies near Stillwater, Oklahoma. Day of year (DOY), canopy height (CH), Normalized Difference Vegetation Index (NDVI), and percent reflectance in five wavelength bands were candidate input variables for the models. The study spanned two growing seasons and nine patches located within three pastures under patch burn management, and the resulting data set with > 3 000 observations was split randomly with 85% for model calibration and 15% withheld for validation. Standing crop ranged from 0 to 852 g m^? 2, and FMC ranged from 0% to 204%. With DOY, CH, and NDVI as predictors, the SMLR model for standing crop produced a root mean squared error (RMSE) of 119 g m^? 2 on the validation data, while the RMSE of the corresponding ANN model was 116 g m^? 2. With the same predictors, the SMLR model for FMC produced an RMSE of 26.7% compared with 23.8% for the corresponding ANN model. Thus, the ANN models provided better prediction accuracy but at the cost of added computational complexity. Given the large variability in the underlying datasets, the models developed here may prove useful for nondestructive estimation of standing crop and FMC in other similar grassland environments.     

Economics of Intensively Aerated Catfish Ponds

The US catfish industry is evolving by adopting production‐intensifying practices that enhance productivity. Catfish producers have increased aeration rates over time, and some now use intensive rates of aeration (>9.33 kW/ha). Costs and production performance were monitored at commercial catfish farms using high levels of aeration (11.2–18.7 kW/ha) in Alabama, Arkansas, and Mississippi. A multivariate‐cluster analysis was used to identify four different management clusters of intensively aerated commercial catfish farms based on stocking density, size of fingerlings at stocking, and feed conversion ratios (FCR). Breakeven prices of hybrid catfish raised in intensively aerated pond systems were estimated to range from $1.86/kg to $2.17/kg, with the lowest costs associated with the second greatest level of production intensity. The two medium‐intensity clusters generated sufficiently high revenues for long‐term profitability. However, the least‐intensive and the most‐intensive clusters were economically feasible only when catfish and feed prices were closer to less probable market prices. Feed price, FCR, and yield contributed the most to downside risk. Intensive aeration in catfish ponds, up to the levels analyzed in this study, appears to be economically feasible under the medium‐intensity management strategies identified in this analysis.     

Performance of Alternative Diets Containing Solvent‐Extracted Distillers Dried Grains with Solubles Compared to Traditional Diets for Pond‐Raised Channel Catfish,Ictalurus punctatus,and Hybrid Catfish,Ictalurus punctatus × Ictalurus furcatus

Two concurrent pond studies were initiated in April 2011 to evaluate feeds containing solvent‐extracted distillers dried grains with solubles (SE‐DDGS) in both 28 and 32% protein catfish feeds. Channel catfish, Ictalurus punctatus, were stocked in multiple‐batch production ponds at the University of Arkansas at Pine Bluff (UAPB) and hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus, in single‐batch production ponds at the National Warmwater Aquaculture Center (NWAC), Mississippi State University, Stoneville, Mississippi, USA. The experimental design was a 2 × 2 factorial with two protein levels (32 and 28% protein), with and without 20% SE‐DDGS. Fish were fed once daily to apparent satiation, and managed similarly to a commercial farm for 186 d at UAPB and 172 d at NWAC. For channel catfish, two‐way ANOVA showed significant effects of both protein level (28% being better than 32%) and protein source (20% SE‐DDGS diets being better than traditional diets) on yield, survival, total diet fed, and feed conversion ratio (FCR), due primarily to effects on the understocked fingerlings. Partial budget analysis suggested that the 28% protein diet with the 20% SE‐DDGS was preferred economically for the prevailing feed costs. For hybrid catfish, two‐way ANOVA did not show significant differences in total diet fed, yield, survival, and processing yields, but use of SE‐DDGS resulted in a lower FCR. Results showed that both channel and hybrid catfish can utilize 20% SE‐DDGS in the diet without adversely affecting production or processing characteristics.     

Estrogen sex-reversal of Tilapia aurea

Chemical treatments were used to produce sex-reversed female (genetic male) Tilapia aurea, which can be bred to produce monosex offspring. Various combinations of estrogens, two synthetic and one natural, an antiandrogen, and a ‘pituitary blocking agent’ were orally administered to sexually undifferentiated fry. Treatment periods were 4, 5, 6 and 8 weeks. Seven of the 36 treatments produced more than 50% females (α = 0.05). Two treatments were more successful than the others: (1) 17-α-ethynylestradiol (EE) at 100 mg kg^?1 diet in combination with methallibure (ME) at 100 mg kg^?1 for 6 weeks and (2) EE-100 with ME-100 and cyproterone acetate (CA) at 100 mg kg^?1 for 6 weeks. These treatments produced fish that were 90% female. Comparisons of the treatments with and without CA indicated that CA may lessen the hormone effectiveness of the treatments. Diethylstilbestrol was as potent as EE in comparable CA treatments.     

Surface Fuel Sampling Strategies: Linking Fuel Measurements and Fire Effects

We assessed the effectiveness of different sampling strategies in linking fine fuel load and crown scorch of ashe (Juniperus ashei) and redberry juniper (J. pinchotii) for prescribed fires conducted in wet and dry periods of the growing season on the Edwards Plateau, Texas, USA. Our aim was to determine if spatial and temporal variation in crown scorch was best predicted by estimates of fuel load sampled with spatially explicit, multiscale sampling strategies or with traditional, simple random sampling of fuel load. We found that multiscale sampling of fuel load underneath and adjacent to juniper crowns was more effective than simple random sampling in predicting crown scorch for the 14 fires conducted in the wet period and the five conducted in the dry period. The type of sampling strategy employed was critical in relating fuel load to crown scorch during the wet period. Percent crown volume scorched ranged from 0% to 100% in these conditions. In contrast, the type of sampling strategy was less important in the dry period when crown scorch was &spigt;90% for all juniper trees. We use these findings to illustrate how a multiscale sampling design can increase prediction power, thereby improving our ability to provide resource professionals with critical values to target in management. Using such a strategy in this study revealed that fine fuel loading of 2 670 kg · ha^–1 were needed to scorch juniper trees 100% for the conditions present in the wet period, whereas only 1 280 kg · ha^–1 were needed in the dry period. To provide managers with this type of information, we suggest that researchers shift from simple, random sampling of fuels to alternate sampling designs where randomization is maintained in the designation of treatments or selection of observations (i.e., individual juniper trees) but where fuel is systematically sampled at the location of the observation of interest.     

Effect of copper status, supplementation, and source on pituitary responsiveness to exogenous gonadotropin-releasing hormone in ovariectomized beef cows

The effect of Cu status, supplementation, and source on pituitary responsiveness to exogenous GnRH was evaluated using nine multiparous, nonpregnant, nonsuckling, ovariectomized Angus cows (7.1 +/- 3.3 yr; 622.9 +/- 49.8 kg; BCS = 6.0 +/- 0.5). Cows were considered Cu-deficient based on liver Cu concentrations (< 30 mg of Cu/kg of DM) after receiving a low-Cu, forage-based diet supplemented (DM basis) with 5 mg of Mo/kg and 0.3% S for 216 d. Copper-deficient cows were stratified based on age, BW, BCS, and liver Cu concentration and assigned randomly to repletion-phase treatments. Treatments included 1) control (no supplemental Cu); 2) organic (ORG; 100% organic Cu); and 3) inorganic (ING; 100% inorganic CuSO4). Treatments were formulated to meet all NRC recommendations, except for Cu, which was supplemented to ORG and ING cows at 10 mg of Cu/kg of dietary DM. During the 159-d repletion phase, Cu status was monitored via liver biopsy samples, and all cows received exogenous progesterone. A controlled intravaginal drug-release device (replaced every 14 d) was used to maintain luteal phase progesterone as a means to provide negative feedback on the hypothalamic-pituitary axis. During the repletion phase, liver Cu concentrations did not differ between ORG and ING cows at any time. By d 77 of the repletion phase, all supplemented cows were considered adequate in Cu, and liver Cu concentrations were greater in supplemented than in nonsupplemented control cows on d 77 (P < 0.05) and throughout (P < 0.01) the repletion phase. Beginning on d 99, exogenous GnRH was administered to all cows at low (0, 3, and 9 microg; Exp. 1) and high doses (0, 27, and 81 microg; Exp. 2) at six different times. Cows were catheterized every fifth day, and blood samples were collected every 15 min for 1 h before and 4 h after GnRH administration and analyzed for LH concentration. In Exp. 1, Cu status and supplementation did not affect basal or peak LH concentrations, but total LH released tended (P < 0.07) to be greater in Cu-supplemented vs. control cows when 3 microg of GnRH was administered. In Exp. 2, there was no effect of Cu supplementation or source on basal, peak, or total LH released, regardless of GnRH dose. Pituitary LH concentrations did not differ across treatments. In conclusion, Cu status, supplementation, and source did not affect GnRH-induced LH secretion or pituitary LH stores in ovariectomized, progesterone-supplemented cows in this experiment.