Identification of traits to improve the nitrogen-use efficiency of wheat genotypes

Nitrogen (N) fertilizer represents a significant cost for the grower and may also have environmental impacts through nitrate leaching and N₂O (a greenhouse gas) emissions associated with denitrification. The objectives of this study were to analyze the genetic variability in N-use efficiency (grain dry matter (DM) yield per unit N available from soil and fertilizer; NUE) in winter wheat and identify traits for improved NUE for application in breeding. Fourteen UK and French cultivars and two French advanced breeding lines were tested in a 2 year/four site network comprising different locations in France and in the UK. Detailed growth analysis was conducted at anthesis and harvest in experiments including DM and N partitioning. Senescence of either the flag leaf or the whole leaf canopy was assessed from a visual score every 3-4 days from anthesis to complete canopy senescence. The senescence score was fitted against thermal time using a five parameters monomolecular-logistic equation allowing the estimation of the timing of the onset and the rate of post-anthesis senescence. In each experiment, grain yield was reduced under low N (LN), with an average reduction of 2.2 t ha⁻¹ (29%). Significant N × genotype level interaction was observed for NUE. Crop N uptake at harvest on average was reduced from 227 kg N ha⁻¹ under high N (HN) to 109 kg N ha⁻¹ under LN conditions while N-utilization efficiency (grain DM yield per unit crop N uptake at harvest; NUtE) increased from 34.0 to 52.1 kg DM kg⁻¹ N. Overall genetic variability in NUE under LN related mainly to differences in NUtE rather than N-uptake efficiency (crop N uptake at harvest per unit N available from soil and fertilizer; NUpE). However, at one site there was also a positive correlation between NUpE and NUE at LN in both years. Moreover, across the 2 year/four site network, the N × genotype effect for NUpE partly explained the N × genotype effect for grain yield and NUE. Averaging across the 16 genotypes, the timing of onset of senescence explained 86% of the variation in NUtE amongst site-season-N treatment combinations. The linear regression of onset of senescence on NutE amongst genoytpes was not significant under HN, but at three of the four sites was significant under LN explaining 32-70% of the phenotypic variation amongst genotypes in NutE. Onset of senescence amongst genotypes was negatively correlated with the efficiency with which above-ground N at anthesis was remobilized to the grain under LN. It is concluded that delaying the onset of post-anthesis senescence may be an important trait for increasing grain yield of wheat grown under low N supply.     

Long-bone fractures in llamas and alpacas: 28 cases (1998–2008)

Treatment and outcome of camelids with long-bone fractures are described. Medical records (1998–2008) of camelids (n = 28) with long-bone fractures were reviewed for signalment, time to presentation, fracture type, method of repair, duration of hospitalization, and post-operative complications. Follow-up information was obtained via telephone interviews with owners. Mean age and weight at presentation were 3.4 years and 56.3 kg, respectively. Twenty-six fractures were treated with internal fixation (n = 11), external fixation (n = 10), combination of internal and external fixation (n = 3), amputation (n = 1), and external fixation followed by amputation (n = 1). Long-term follow-up information was obtained for 19 of the 26 animals. The post-operative complication rate was 23% and owner satisfaction was high. Animals with open fractures were more likely to experience complications. Internal fixation was associated with superior alignment and outcome. Internal fixation techniques should be recommended for camelids.     

Modulation of sheep lymphocyte responses by Fasciola hepatica excretory-secretory products

The effect of Fasciola hepatica excretory-secretory products (FhESPs) on mitogen-induced proliferation of sheep peripheral blood mononuclear cells (PBMCs) and PBMC subsets (CD2(+), CD4(+), CD8(+), gammadeltaTCR(+) or CD21(+) cells) were studied. PBMCs were incubated with Concanavalin A (ConA) or phytohemagglutinin (PHA) at optimal (1 microg per well) or suboptimal (0.25 microg per well) doses and with FhESPs at several doses (1.25-20 microg per well). PBMC subsets were incubated with ConA at a suboptimal dose and with FhESPs at 5 microg per well. These cells were incubated with or without monocytes (CD14(+) cell). FhESPs slightly increased the proliferation of PBMCs stimulated with optimal doses of PHA. FhESPs (10 and 20 microg per well) inhibited the PBMCs stimulated with optimal doses of ConA. FhESP dose-dependent inhibition was observed on PBMCs stimulated with suboptimal doses of ConA. CD21(+) lymphocytes (B lymphocytes), CD14(+) cells (monocytes) and gammadeltaTCR(+) cells were not stimulated by ConA. T lymphocyte subsets (CD2(+), CD4(+) or CD8(+) cells) proliferation was decreased by FhESPs at 5 microg per well. FhESPs inhibits the ConA-induced stimulation of sheep PBMCs and sheep T lymphocyte subsets. Further studies should be done to investigate the mechanism of this FhESP immunomodulatory effect.     

Transmission of a pestivirus infection in a population of Pyrenean chamois

Outbreaks of a previously unrecorded disease have recently affected Pyrenean chamois (Rupicapra pyrenaica pyrenaica) populations across the mountain range. A pestivirus was hypothesized to be the cause of this emerging disease and this type of virus can cross the species barrier and be transmitted to or from wildlife. Using an epidemiological survey conducted from 1995 to 2004 at Orlu, France, we characterized the virus and analyzed its transmission. A phylogenetic analysis of viral sequences and virus neutralization tests showed that the virus belonged to the newly described border disease virus-4 group. The increase of seroprevalence with age indicated that infection can occur at any age and resulted in lifelong immunity. Overall, 70.3% of 323 samples were positive for anti-p80 antibodies and 10.2% of 167 samples showed viremia, as demonstrated by either positive ELISA antigen test or RT-PCR. Infection has thus been widespread in this population since 1995, whereas no mass mortality or clinical signs have been observed. Incidence and seroprevalence varied seasonally and according to number of individuals aged less than 2 years old in the population, so viral transmission was dependent on host population age structure. We propose that the virus is now endemic in this population and is likely detrimental for reproduction and juveniles. Further investigation is needed to estimate the impact of pestivirus on host population dynamics and the risk of cross-transmission to farm animals.     

Effect of Various Acids and Sulfites in Steep Solution on Yields and Composition of Corn Fiber and Corn Fiber Oil

The addition of six acids (organic and inorganic) and four sulfite compounds (including gaseous SO₂) during the conventional corn wet‐milling steeping process of two yellow dent corn hybrids were evaluated for the effect on corn fiber yield, corn fiber oil yield, and the composition of three phytosterol compounds (ferulate phytosterol esters [FPE], free phytosterols [St], and phytosterol fatty acyl esters [St:E]) in the corn fiber oil. No significant effect of different sulfite compounds and acids were observed on corn fiber yields. However, a significant effect was observed on corn fiber oil yield and the composition of corn fiber oil for phytosterol compounds. Three of the sulfite compounds (including gaseous SO₂) caused very little effect on the levels of phytosterol compounds compared with the control sample (corn steeped with sodium metabisulfite and lactic acid). However, for one hybrid, ammonium sulfite gave a significantly higher yield of FPE and St:E and had no effect on the yield of St. For the other hybrid, it gave a significantly higher yield of FPE and had no effect on the yield of St and St:E compared with the control sample. This indicates that the effect of these sulfite compounds on yields of these phytosterol compounds in corn fiber oil is probably hybrid‐dependent. No significant effect of acids was observed on corn fiber yields, but significant effects were observed on corn fiber oil yields and yields of phytosterol compounds in the corn fiber oil. The effect also seems to be hybrid‐dependent because different acids affected the two hybrids differently. Overall, it seems that weak acids have a positive effect on increasing the individual phytosterol compounds in the corn fiber. When comparing the effect of experimental acids and sulfites on the two hybrids, acids have a more positive effect than sulfites in increasing the yield of phytosterol compounds in corn fiber oil.     

Comparative growth and welfare in rainbow trout reared in recirculating and flow through rearing systems

The objective of this study was to compare fish performance and welfare at different stocking densities in a recirculating system (RS) and a flow through system (FTS) under field conditions. During the 77 days experiment, the fish survival rate was high (99.3%) and stocking density increased from 57 to 98–108 kg m^?3. No significant differences in growth were observed between RS and FTS until day 56. Later, growth decreased in the FTS, while it remained similar to the farm reference at 50 kg m^?3 in the RS. Final weight was 17% higher in RS than in FTS. The maximum carrying capacity of the RS was near 100 kg m^?3, limited by NO₂ increase up to safe level at the end of the experiment, the maximum carrying capacity of the FTS was near 85 kg m^?3, probably limited by CO₂ concentration (17.8 ± 5.7 mg l^?1). In the RS, the relative length index of pectoral and dorsal fins was lower than in the FTS, which may be attributed to the tank hydrodynamics. In both systems, an improvement of the pectoral and dorsal profile was observed at the end of the experiment, attributed to a swimming activity reduction that may have decreased contact between individuals. In the RS, high caudal fin deterioration (50% versus 20% in FTS) was observed irrespective of stocking density, that could be linked to the highest water velocity modifying the fish swimming activity. The results confirm that when water quality is maintained in safe level ranges, high densities can be used in trout RS without fish performance and pectoral or dorsal fin deterioration, but with a major caudal impairment.     

Towards environmentally sustainable aquaculture: Comparison between two trout farming systems using Life Cycle Assessment

Life Cycle Assessment (LCA) was applied to evaluate the global environmental impact of two scenarios of trout production systems based on the operational information from an operational farm using a flow through system (FTF) and an experimental pilot low head recirculating system (RSF) located on the same site. The main differences between the environmental balances of the two systems were relative to water use, eutrophication potential and energy use. Independently of the system used, feed is the key indicator in determining the environmental balance (notwithstanding eutrophication potential and water dependence) monitored by fish production, chemical products, buildings and energy consumption.Consequently, when considering the RSF with a lower feed conversion ratio (0.8 versus 1.1 for FTF), the environmental balance of the RSF is more favourable at both global and regional levels, except with regards to energy use. RSF water dependence is 93% lower than the FTF and its eutrophication potential is 26–38% lower due to reduced waste release. On the other hand, at 57,659 MJ per ton of fish produced (16 kWh per kg), the RSF consumes 24–40% more energy than the FTF, especially for aeration and water treatment. Nevertheless, the RSF has significant potential for energy reduction through improvements to airlift and biofilter designs which would reduce RSF energy use to a level similar to that of the FTF (34,869–43,841 MJ per ton of fish produced, corresponding to 10 and 12 kWh respectively). LCA is therefore a powerful tool which can be used on fish farms to define and prioritise the most promising potential improvements to the system.