Evaluation of on-farm irrigation applications using the simulation model EPIC

An understanding of water needs in agriculture is a critical input in resolving the water resource issues that confront many southeastern and other US states. The objective of this study was to evaluate on-farm irrigation applications for three major crops grown in Georgia, USA using the Environmental Policy Integrated Climate (EPIC) model. For cotton, 16, 58, and 75 farmers fields in 2000, 2001, and 2002, respectively, were selected from among the Agricultural Water Pumping (AWP) program sites across the state of Georgia. For maize, 9, 20, and 28 fields were selected in 2000, 2001, and 2002, respectively, and for peanut, 18, 51, and 54 fields were selected in 2000, 2001, and 2002, respectively. The majority of these fields were located in the southwest region of Georgia, where traditional row-crop agriculture is most dominant. We compared the simulated irrigation requirements with the amount of water that the farmers actually applied during the 2000, 2001, and 2002 growing seasons. For cotton and peanut, the means of farmer-applied irrigation amounts and simulated irrigation requirements agreed very well, with similar values for root mean squared deviation (RMSD) of the two crops. For maize, good agreement between simulated and farmer-applied irrigation amounts were found only in 2001. Farmers applied more water to their maize crop when compared to simulated irrigation requirements, especially when rainfall was very low and potential evapotranspiration was high during the 2000 and 2002 growing seasons. The component of the mean squared deviation (MSD = RMSD²) related to the pattern of variability in seasonal irrigation applications contributed most to MSD. Accurate estimates of the mean and the magnitude of variability in seasonal irrigation applications could be very useful for the estimation of overall water use by agriculture in Georgia and other southeastern states. This study showed that the EPIC model would be an adequate tool for this purpose; potential users could include policy makers, planners and regulators, including the Georgia Department of Natural Resources (DNR).     

Bone morphogenetic protein 15 supplementation enhances cumulus expansion,nuclear maturation and progesterone production of in vitro-matured bovine cumulus-oocyte complexes

In vitro embryo production (IVP) efficiency is reduced when compared to in vivo. The basic knowledge of bovine in vitro oocyte maturation (IVM) mechanisms provides support to improve in vitro embryo production yields. The present study assessed the effects of bone morphogenetic protein 15 (BMP15), fibroblast growth factor 16 (FGF16) and their combined action on cumulus cells (CC) expansion, oocyte and CC DNA fragmentation, oocyte nuclear maturation, energetic metabolism and progesterone production in bovine IVM. Cumulus-oocyte complexes (COC) were matured in control or supplemented media containing BMP15 (100 ng/ml), FGF16 (10 ng/ml) or BMP15 combined with FGF16; and assessed at 0 and 22 hr of IVM. BMP15 alone or its association with FGF16 enhanced cumulus expansion. BMP15 decreased DNA fragmentation in both CC and oocytes, and improved oocyte nuclear maturation rate. In addition, BMP15 increased CC progesterone production, an effect not previously reported. The present study reinforces previous data pointing to a beneficial influence of BMP15 during IVM, while providing novel evidence that the underlying mechanisms involve increased progesterone production.     

Elimination of the associated microbial community and bioencapsulation of bacteria in the rotifer Brachionus plicatilis

The bioencapsulation of live bacteria in the rotifer Brachionus plicatilis was determined under monoxenic conditions. The first objective was to evaluate the microbiota of the rotifer during intensive production and to obtain sterile rotifer cultures starting from adult females or amictic eggs using PVP-Iodine, Hydrogen peroxide or antibiotic mixtures. In the rotifers, the proportion of vibrios increased significantly during the mass production, displacing other unidentified marine bacteria. Rotifers, in the absence of culturable bacteria were obtained starting from amictic eggs and using Trimetroprim-sulfametoxasole (Bactrim Roche®) at 10 ml l^–1. The effect of members of Vibrionaceae on the survival and growth rate of rotifers was determined under monoxenic conditions. The survival of rotifers was not affected in the presence of different isolates, while amictic egg formation occurred and the populations increased when the strains Vibrio proteolyticus C279 and Aeromonas media C226 were tested. All isolates were successfully incorporated in the rotifers, since there was no significant difference between the numbers of bioencapsulated cells of different strains of isolates. The results show that it is possible to replace the microbial community in rotifer cultures, started from disinfected amictic eggs, with selected bacterial strains. This could be used as a tool for future studies to reveal the role of specific bacteria on first larval stages of marine fish species.     

Determining culture strategies in populations of the European flat oyster, Ostrea edulis, affected by bonamiosis

Bonamiosis affects the viability of oyster culture in Galicia (NW Spain). This study shows the effects of the disease on three oyster populations from hatcheries in different culture areas (Cambados and Bueu) and different origin: stock A [F₁]_, stock B [F₂]_, and stock C [F₂]. These stocks were cultured between November 1998 and November 2000 in Cambados and Bueu. In the Cambados area, bonamiosis is considered to be endemic, while the disease does not generally affect Bueu area. Sampling was conducted at 3-month intervals to study prevalence of Bonamia, mortality and growth rates. In the Cambados area, bonamiosis was detected 12 months after beginning culture but in the Bueu area, it was not detected until 24 months after initiating cultures. Our results suggest that there is a relationship between presence of Bonamia ostreae and oyster mortalities, which were observed in the three stocks from Cambados. These mortalities were associated with the culture area (Cambados) and not with stock of oysters. Growth was satisfactory in both areas as oysters reached commercial size (60 mm) 15 months after beginning the cultures. In an area where Bonamia is present, such as Cambados, the oysters should be marketed promptly (after approximately 15–18 months of culture) but in areas where Bonamia is not present, such as Bueu, the oyster farmer can culture oysters over a long period of time, prior to harvest, if necessary.     

Toxoplasma gondii and Neospora caninum seroprevalences in domestic South American camelids of the Peruvian Andes

The objective of this study was to investigate the presence of Toxoplasma gondii- and Neospora caninum-specific antibodies in domestic South American camelids (SAC) (llamas and alpacas) from the Peruvian Andes through a cross-sectional study. A wide panel of serum samples collected from 1,845 llamas and 2,874 alpacas from the two main SAC production areas of Peru was selected. Immunofluorescence antibody technique was employed to detect and titrate specific anti-T. gondii and anti-N. caninum immunoglobulins G in serum samples. The association between T. gondii and N. caninum seroprevalence and the geographical origin (Central and South Peruvian Andes) was evaluated. Anti-T. gondii antibodies were found in 460 (24.9 %) llamas and 706 (24.6 %) alpacas, whereas anti-N. caninum antibodies were detected in 153 (8.3 %) llamas and 425 (14.8 %) alpacas. Toxoplasma gondii infection was strongly associated with the South Peruvian Andes where moderate climate conditions, larger human population, compared to the Central region, and the presence of wildlife definitive hosts could favor horizontal transmission to SAC. In contrast, N. caninum infection was not associated with the geographical region. These results indicate that T. gondii and N. caninum infections are highly and moderately widespread, respectively, in both species of domestic SAC studied in the sampled areas and appropriate control measures should be undertaken to reduce the prevalence of both parasitic infections.     

Effect of colostrum redox balance on the oxidative status of calves during the first 3 months of life and the relationship with passive immune acquisition

New-born calves depend upon colostrum intake for the acquisition of immunoglobulins (Ig) and other beneficial substances. However, colostrum is also a source of reactive oxygen species (ROS). Intrinsic production of ROS also increases after birth, so the combination of colostral and intrinsic ROS could overwhelm the antioxidant capacity of the calf leading to oxidative stress (OS), a condition that has been shown to play a key role in the initiation and development of several pathological conditions.The aim of this observational study was to assess the effects of the redox balance of colostrum on the oxidative status of calves and on passive immune transfer. Serum samples were taken from 20 calves on their day of birth, every week during their first month of life and at 2 and 3 months of age, and the concentrations of ROS and serum antioxidant capacity (SAC) assayed. The oxidative/anti-oxidative profile and IgG content of the colostrum were also assessed.The redox balance of the colostrum had a significant effect on both calf oxidative status and on passive immune transfer (as measured by calf serum IgG concentration), which indicates that the oxidative/antioxidative profile of colostrum should be measured when colostrum quality is assessed. The highest risk of OS during the study period was found to be when the calves were fed artificial milk replacer; this suggests that calves should be supplemented with antioxidants during this period in order to minimize any harmful consequences of high ROS generation.     

Evaluation of different enzyme-linked immunosorbent assays for the diagnosis of brucellosis due to Brucella melitensis in sheep

Six serological assays for the diagnosis of ovine brucellosis, due to Brucella melitensis were evaluated. Reference serum samples from sheep of known B. melitensis infection status (n = 118) were assessed using the Rose Bengal test (RBT), complement fixation test (CFT) and four commercial enzyme-linked immunosorbent assays (ELISAs), including two indirect ELISAs (iELISAs), one competitive ELISA (cELISA) and one blocking ELISA (bELISA).The highest differential positive rates (DPR) were obtained with the cELISA and bELISA, while the lowest DPR was estimated using iELISAs. A latent class analysis was performed to estimate the accuracy of the CFT, RBT and bELISA using 1827 sera from sheep undergoing testing as part of a surveillance and control programme. Lower sensitivity and specificity were obtained for the three serological tests when the field samples were used. A higher DPR was achieved by the CFT, compared to bELISA and RBT. The results suggest that ELISAs, and particularly the bELISA, might be suitable for inclusion in the European Union legislation on intra-community trade for diagnosing B. melitensis infection in sheep, as it has a similar test performance compared to the RBT.     

Stem taper function for sweet chestnut (Castanea sativa Mill.) coppice stands in northwest Spain

? Context

Despite the economic importance of Castanea sativa Mill. in northwest Spain, studies of its growth and yield are practically non-existent.

? Aims

A compatible system formed by a taper function, a total volume equation, and a merchantable volume equation was developed for chestnut (C. sativa Mill.) coppice stands in northwest Spain.

? Methods

Data from 203 destructively sampled trees were used for the adjustment. Outliers were removed with a non-parametric local adjustment, providing a final data set of measurements taken from 3,188 sections which was used to test five taper models (compatible and non-compatible). A second-order continuous autoregressive error structure was used to model the error term and account for autocorrelation. Presence of multicollinearity was evaluated with the condition number. Comparison of the models was carried out using overall goodness-of-fit statistics and graphical analysis.

? Results

Results show that the models developed by Fang et al. in For Sci 46: 1–12, 2000 and Kozak in For Chron 80, N 4: 507–515, 2004 were superior to other equations in predicting diameter for chestnut coppice stands.

? Conclusion

The compatible volume system developed by Fang et al. in For Sci 46: 1–12, 2000 was finally selected as it provided the best compromise between describing stem profile and also estimating merchantable height, merchantable volume, and total volume and therefore provides the first specific tool for more effective management of chestnut coppice stands.     

Response to the interaction of thinning and pruning of pine species in Mediterranean mountains

Pruning allows knot-free timber to be obtained, thereby increasing the value of the highest-value wood products. However, the effect of pruning on growth is under discussion, and knowledge about the tree response to the simultaneous development of thinning and pruning is scarce. The objective of this study was to analyze the effect of the interaction of thinning and pruning on tree and stand level and the annual radial growth of two pine species native to Mediterranean mountains. We used long-term data of three trials installed in pine stands where several combinations of pruning and thinning were developed. Five inventories were carried out for each trial, and the mean dasometric features of the different treatments were compared using linear mixed models including a competition index. In addition, we collected cores from ten trees per plot in order to evaluate the annual response of trees to the thinning and pruning. We analyzed the annual radial growth using a semiparametric approach through a smooth penalized spline including rainfall and temperature covariates. Pruning did not show any effect on growth. However, larger diameter and increased annual radial growth were found in thinned plots, both with and without pruning, as compared to unthinned plots. Also, we found significant effects of climate on annual radial growth. We recommend the application of thinning and pruning in stands of Mediterranean mountains in order to get knot-free timber since growth reduction was not found in thinned stands.     

Genetic changes in durum wheat yield components and associated traits in Italian and Spanish varieties during the 20th century

Twelve field experiments comparing 24 durum wheat varieties from three periods—old (<1945), intermediate (1950–1985) and modern (1988–2000)—were carried out in order to ascertain the advances made in durum wheat yield components and related traits in Italian and Spanish germplasm. Grain yield improvements were based on linear increases in the number of grains per m² and harvest index, while grain weight and biomass remained unchanged. Yield per plant increased at a rate of 0.36 and 0.44% y⁻¹ and the number of grains per m² improved by 39% and 55% in Italian and Spanish varieties, respectively. The mean rate of increase in the number of grains per m² was 0.55% y⁻¹. Plants per m², spikes per plant and grains per spike contributed 20%, 29% and 51%, respectively, to the increase in the number of grains per m². The enhance of the number of grains per m² was due to the greater grain set in the modern varieties, since the number of spikelets per spike remained unchanged. Harvest index increased overall by 0.48% y⁻¹ (0.40 and 0.53% y⁻¹ in Italian and Spanish varieties, respectively). Plant height was the trait that suffered the most dramatic changes (it decreased at a rate of −0.81% y⁻¹, with little difference between the varieties of the two countries), as consequence of the presence of the Rht-B1 dwarfing gene. Harvest index and plant height, which were the traits that most contributed to discriminating between periods, remained unchanged from 1980 to 2000. The higher rates of improvement in Spain are discussed in the context of the contrasting strategies followed to improve durum wheat yield in the two countries.