Migratory birds have higher prevalence and richness of avian haemosporidian parasites than residents

Individuals of migratory species may be more likely to become infected by parasites because they cross different regions along their route, thereby being exposed to a wider range of parasites during their annual cycle. Conversely, migration may have a protective effect since migratory behaviour allows hosts to escape environments presenting a high risk of infection. Haemosporidians are one of the best studied, most prevalent and diverse groups of avian parasites, however the impact of avian host migration on infection by these parasites remains controversial. We tested whether migratory behaviour influenced the prevalence and richness of avian haemosporidian parasites among South American birds. We used a dataset comprising ~ 11,000 bird blood samples representing 260 bird species from 63 localities and Bayesian multi-level models to test the impact of migratory behaviour on prevalence and lineage richness of two avian haemosporidian genera (Plasmodium and Haemoproteus). We found that fully migratory species present higher parasite prevalence and higher richness of haemosporidian lineages. However, we found no difference between migratory and non-migratory species when evaluating prevalence separately for Plasmodium and Haemoproteus, or for the richness of Plasmodium lineages. Nevertheless, our results indicate that migratory behaviour is associated with an infection cost, namely a higher prevalence and greater variety of haemosporidian parasites.     

The role of <Emphasis Type="Italic">Dlx</Emphasis> homeogenes in early development of the olfactory pathway

Development of the olfactory pathway requires interaction between cells and signals of different origin. Olfactory receptor neurons (ORN) in the olfactory placodes (OP) extend axons towards the forebrain (FB); with innervation taking place at a later time following degradation of the basement membrane. Cells from the OP migrate along ORN axons and differentiate into various elements, including ensheathing and Gonadotropin Releasing Hormone (GnRH)+ cells. The importance of the olfactory connection and migration is highlighted by the severe endocrine phenotype in Kallmann’s patients who lack this migratory pathway. Little is known about the genetic control of intrinsic ORN properties. Inactivation of the distalless-related Dlx5 prevents connections between ORNs and FB. Using a grafting approach we show that misguidance and lack of connectivity is due to intrinsic defects in ORN neurites and migratory cells (MgC), and not to environmental factors. These data point to a cell-autonomous function of Dlx5 in providing ORN axons with their connectivity properties. Dlx5 also marks a population of early MgC that partly overlaps with the GnRH+ population. In the absence of Dlx5 MgCs of the Dlx5+ lineage migrate, associated with PSA-NCAM+ axons, but fail to reach the FB as a consequence of the lack of axonal connection and not an inability to migrate. These data suggests that Dlx5 is not required to initiate migration and differentiation of MgCs. An erratum to this article can be found at     

Knockdown of the corazonin gene reveals its critical role in the control of gregarious characteristics in the desert locust

The two plague locusts, Schistocerca gregaria and Locusta migratoria, exhibit density-dependent phase polyphenism. Nymphs occurring at low population densities (solitarious forms) are uniformly colored and match their body color to the background color of their habitat, whereas those occurring at high population densities (gregarious) develop black patterns. An injection of the neuropeptide, corazonin (Crz) has been shown to induce black patterns in locusts and affect the classical morphometric ratio, F/C (F, hind femur length; C, maximum head width). We herein identified and cloned the CRZ genes from S. gregaria (SgCRZ) and L. migratoria. A comparative analysis of prepro-Crz sequences among insects showed that the functional peptide was well conserved; its conservation was limited to the peptide region. Silencing of the identified SgCRZ gene in gregarious S. gregaria nymphs markedly lightened their body color and shifted the adult F/C ratio toward the value typical of solitarious forms. In addition, knockdown of the gene in solitarious nymphs strongly inhibited darkening even after a transfer to crowded conditions; however, these individuals developed black patterns after being injected with the Crz as a rescue treatment. SgCRZ was constitutively expressed in the brains of S. gregaria during nymphal development in both phases. This gene was highly expressed not only in the brain in both phases, but also in the corpora allata in the gregarious phase. This conspicuous phase-dependent difference in SgCRZ gene expression may indicate a functional role in the control of phase polyphenism in this locust.     

Effects of feed withdrawal duration on animal behaviour,rumen microbiota and blood chemistry in feedlot cattle: implications for rumen acidosis

Feed withdrawal (FW) is a frequent issue in open outdoor feedlot systems, where unexpected circumstances can limit the animals’ access to food. The relationship among fasting period, animal behaviour during feed reintroduction (FR) and acidosis occurrence has not been completely elucidated. Twenty steers fitted with rumen catheters were fed a high-concentrate diet (concentrate : forage ratio 85 : 15) and were challenged by a protocol of FW followed by FR. The animals were randomly assigned to one of the four treatments: FW for 12 h (T12), 24 h (T24), 36 h (T36) or no FW (control group) followed by FR. The steers’ behaviour, ruminal chemistry, structure of the ruminal microbial community, blood enzymes and metabolites and ruminal acidosis status were assessed. Animal behaviour was affected by the FW–FR challenge ( P < 0.05). Steers from the T12, T24 and T36 treatments showed a higher ingestion rate and a lower frequency of rumination. Although all animals were suspected to have sub-acute ruminal acidosis (SARA) prior to treatment, a severe case of transient SARA arose after FR in the T12, T24 and T36 groups. The ruminal pH remained below the threshold adopted for SARA diagnosis ( pH value = 5.6) for more than three consecutive hours (24, 7 and 19 h in the T12, T24 and T36 treatments, respectively). The FW–FR challenge did not induce clinical acute ruminal acidosis even though steers from the T36 treatment presented ruminal pH values that were consistent with this metabolic disorder (pH threshold for acute acidosis = 5.2). Total mixed ration reintroduction after the withdrawal period reactivated ruminal fermentation as reflected by changes in the fermentation end-products. Ruminal lactic acid accumulation in steers from the T24 and T36 treatments probably led to the reduction of pH in these groups. Both the FW and the FR phases may have altered the structure of the ruminal microbiota community. Whereas fibrolytic bacterial groups decreased relative abundance in the restricted animals, both lactic acid producer and utiliser bacterial groups increased ( P < 0.05). The results demonstrated a synchronisation between Streptococcus (lactate producer) and Megasphaera (lactate utiliser), as the relative abundance of both groups increased, suggesting that bacterial resilience may be central for preventing the onset of metabolic disturbances such as ruminal acidosis. A long-FW period (36 h) produced rumen pH reductions well below and lactic acid concentration increased well above the accepted thresholds for acute acidosis without any perceptible clinical signs.     

Increased juvenile hormone levels after long-duration flight in the grasshopper, Melanoplus sanguinipes

Although, in many insects, migration imposes a cost in terms of timing or amount of reproduction, in the migratory grasshopper Melanoplus sanguinipes performance of long-duration flight to voluntary cessation or exhaustion accelerates the onset of first reproduction and enhances reproductive success over the entire lifetime of the insect. Since juvenile hormone (JH) is involved in the control of reproduction in most species, we examined JH titer after long flight using a chiral selective radioimmunoassay. JH levels increased on days 5 and 8 in animals flown to exhaustion on day 4 but not in 1-h or non-flier controls. No difference was seen in the diel pattern of JH titer, but hemolymph samples were taken between 5 and 7 h after lights on. Treatment of grasshoppers with JH-III mimicked the effect of long-duration flight in the induction of early reproduction. The increased JH titer induced by performance of long-duration flight is thus at least one component of flight-enhanced reproduction. To test the possibility that post-flight JH titer increases are caused by adipokinetic hormone (AKH) released during long flights, a series of injections of physiological doses of Lom-AKH I were given to unflown animals to simulate AKH release during long flight. This treatment had no effect on JH titers. Thus, although AKH is released during flight and controls lipid mobilization, it is not the factor responsible for increased JH titers after long-duration flight.     

Phenology and climate change: a long-term study in a Mediterranean locality

It is well documented that plant and animal phenology is changing in response to recent climate warming in the Palaearctic. However, few long-term data sets are currently available in the Mediterranean basin. The present study reports long-term temporal trends of several phenophases of 45 plants, 4 insects and 6 migratory insectivorous birds. Dynamic factor analyses performed with plant phenophases showed that most of those events occurring at spring and summer had common trends toward the advancement, especially since mid-1970s. However, during these last decades, insect phenology showed a steeper advance than plant phenology, suggesting an increase of decoupling of some plant–insect interactions, such as those between pollinators and flowers or herbivorous insects and their plant resources. All trans-Saharan bird species showed highly significant temporal trends in all studied phenophases (some of them covering most of the last century). In two species, the duration of stay is increasing due to both earlier arrivals and later departures. On the other hand, two wintering species showed a significant advancement in their arrival dates, while an opposite pattern were found for departures of each one. Only one of these species increased significantly its wintering stay. Bird departures were not related to local climate in any species. Our results demonstrate a key role of local temperatures behind interannual variability of most plant and insects phenophases, with especial emphasis in those occurring in spring and summer. Therefore, the common signal towards the advancement recorded since mid-1970s resulted from the recent rise in temperatures.     

The influence of climate on the timing and rate of spring bird migration

Ecological processes are changing in response to climatic warming. Birds, in particular, have been documented to arrive and breed earlier in spring and this has been attributed to elevated spring temperatures. It is not clear, however, how long-distance migratory birds that overwinter thousands of kilometers to the south in the tropics cue into changes in temperature or plant phenology on northern breeding areas. We explored the relationships between the timing and rate of spring migration of long-distance migratory birds, and variables such as temperature, the North Atlantic Oscillation (NAO) and plant phenology, using mist net capture data from three ringing stations in North America over a 40-year period. Mean April/May temperatures in eastern North America varied over a 5°C range, but with no significant trend during this period. Similarly, we found few significant trends toward earlier median capture dates of birds. Median capture dates were not related to the NAO, but were inversely correlated to spring temperatures for almost all species. For every 1°C increase in spring temperature, median capture dates of migratory birds averaged, across species, one day earlier. Lilac (Syringa vulgaris) budburst, however, averaged 3 days earlier for every 1°C increase in spring temperature, suggesting that the impact of temperature on plant phenology is three times greater than on bird phenology. To address whether migratory birds adjust their rate of northward migration to changes in temperature, we compared median capture dates for 15 species between a ringing station on the Gulf Coast of Louisiana in the southern USA with two stations approximately 2,500 km to the north. The interval between median capture dates in Louisiana and at the other two ringing stations was inversely correlated with temperature, with an average interval of 22 days, that decreased by 0.8 days per 1°C increase in temperature. Our results suggest that, although the onset of migration may be determined endogenously, the timing of migration is flexible and can be adjusted in response to variation in weather and/or phenology along migration routes.     

Effect of dietary nitrogen level and source on mRNA expression of urea transporters in the rumen epithelium of fattening bulls

This paper aims to study the effect of the dietary treatments on mRNA expression of urea transporter B (UT-B) and some aquaporins (AQP) in rumen epithelium of Italian Simmental young bulls. Eighty animals allocated to 16 pens were fed from about 500 to 650 kg body weight with four experimental diets, which resulted from the combination of two crude protein levels (125 and 110 g/kg dry matter, diets M and L, respectively) and two nitrogen sources (soybean meal (SBM) or SBM partly replaced by an isonitrogenous mixture of corn and urea; diets ?U and +U, respectively). At slaughtering samples of blood and rumen epithelium were collected from six bulls for each diet. Blood samples were analysed for haematological parameters and quantitative PCR was carried out on the mRNA extracted from the rumen epithelium samples. The bulls fed diets M had lower plasma concentrations of aspartate aminotransferase than those receiving diets L (78.9 vs. 88.3 U/l, p = 0.04). Plasma urea was higher (p = 0.03) for diets M and lower for diets +U (2.0 vs. 2.5 and 1.73 vs. 2.00 mmol/l, respectively, in M and L diets, p = 0.04). The effect of dietary treatments on rumen UT expression were limited to AQP3, which was down regulated (p = 0.01) in diets +U. Finally, a high positive correlation (R² = 0.871) between the expressions of AQP7 and AQP10 was found. In conclusion, the AQP3 appears very responsive to dietary treatments and therefore it is a candidate to be further studied in rumen metabolism experiments. The close relationship between mRNA expression of AQP7 and AQP10 indicates a similar function of these two proteins.     

Eco-evolutionary drivers of avian migratory connectivity

Migratory connectivity, reflecting the extent by which migrants tend to maintain their reciprocal positions in seasonal ranges, can assist in the conservation and management of mobile species, yet relevant drivers remain unclear. Taking advantage of an exceptionally large (~150,000 individuals, 83 species) and more-than-a-century-long dataset of bird ringing encounters, we investigated eco-evolutionary drivers of migratory connectivity in both short- and long-distance Afro-Palearctic migratory birds. Connectivity was strongly associated with geographical proxies of migration costs and was weakly influenced by biological traits and phylogeny, suggesting the evolutionary lability of migratory behaviour. The large intraspecific variability in avian migration strategies, through which most species geographically split into distinct migratory populations, explained why most of them were significantly connected. By unravelling key determinants of migratory connectivity, our study improves knowledge about the resilience of avian migrants to ecological perturbations, providing a critical tool to inform transboundary conservation and management strategies at the population level.     

Effects of diets differing in protein source and technical treatment on digestibility,performance and visceral and biochemical parameters of fattening pigs

The aim of the experiment on 100 cross-bred barrows was to compare commercial diets for fattening pigs based on either soya bean meal (SBM) imported from non-European countries with diets based on a mixture of locally produced rape seed meal, distillers’ dried grains with solubles and soya beans as main protein sources. In addition, these both types of diets were processed by two different technical feed treatments, i.e. coarse grinding without hydrothermal treatment or fine grinding and pelleting. With only few exceptions, nutrients of the diet without SBM were more digestible (p < 0.05) resulting in a higher metabolisable energy (ME) content. Fine grinding and pelleting increased also the ME content and the nutrient digestibility with the exception of crude fibre. Higher feed intake of animals that fed diets without SBM (p < 0.01) resulted in higher average daily gain (p < 0.01). However feeding this diet, the higher digestibility was not reflected in a decreased feed-to-gain ratio (FGR), but fine grinding and pelleting reduced FGR (p < 0.001). A higher pH value and a lower DM content of caecal chymus were detected in animals that received coarsely ground feed (p < 0.05). Animals that fed finely ground and pelleted feed had higher slaughter and relative liver weights and higher blood cholesterol concentrations (p = 0.040). The urea concentrations of blood were lower (p = 0.019) after feeding diets without SBM. In conclusion, SBM imported from non-European countries can be replaced by alternative local protein sources without compromising digestibility or performances of animals. Although fine grinding and thermal treatment particularly seemed to be advantageous for digestibility and performance, the possible risk of development of stomach lesions should be considered.