Closing system-wide yield gaps to increase food production and mitigate GHGs among mixed crop-livestock smallholders in Sub-Saharan Africa.

In this study we estimate yield gaps for mixed crop-livestock smallholder farmers in seven Sub-Saharan African sites covering six countries (Kenya, Tanzania, Uganda, Ethiopia, Senegal and Burkina Faso). We also assess their potential to increase food production and reduce the GHG emission intensity of their products, as a result of closing these yield gaps. We use stochastic frontier analysis to construct separate production frontiers for each site, based on 2012 survey data prepared by the International Livestock Research Institute for the Climate Change, Agriculture and Food Security program. Instead of relying on theoretically optimal yields-a common approach in yield gap assessments-our yield gaps are based on observed differences in technical efficiency among farms within each site. Sizeable yield gaps were estimated to be present in all of the sites. Expressed as potential percentage increases in outputs, the average site-based yield gaps ranged from 28 to 167% for livestock products and from 16 to 209% for crop products. The emission intensities of both livestock and crop products registered substantial falls as a consequence of closing yield gaps. The relationships between farm attributes and technical efficiency were also assessed to help inform policy makers about where best to target capacity building efforts. We found a strong and statistically significant relationship between market participation and performance across most sites. We also identified an efficiency dividend associated with the closer integration of crop and livestock enterprises. Overall, this study reveals that there are large yield gaps and that substantial benefits for food production and environmental performance are possible through closing these gaps, without the need for new technology.

MELODIE: a whole-farm model to study the dynamics of nutrients in dairy and pig farms with crops.

In regions of intensive pig and dairy farming, nutrient losses to the environment at farm level are a source of concern for water and air quality. Dynamic models are useful tools to evaluate the effects of production strategies on nutrient flows and losses to the environment. This paper presents the development of a new whole-farm model upscaling dynamic models developed at the field or animal scale. The model, called MELODIE, is based on an original structure with interacting biotechnical and decisional modules. Indeed, it is supported by an ontology of production systems and the associated programming platform DIESE. The biotechnical module simulates the nutrient flows in the different animal, soil and crops and manure sub-models. The decision module relies on an annual optimization of cropping and spreading allocation plans, and on the flexible execution of activity plans for each simulated year. These plans are examined every day by an operational management sub-model and their application is context dependent. As a result, MELODIE dynamically simulates the flows of carbon, nitrogen, phosphorus, copper, zinc and water within the whole farm over the short and long-term considering both the farming system and its adaptation to climatic conditions. Therefore, it is possible to study both the spatial and temporal heterogeneity of the environmental risks, and to test changes of practices and innovative scenarios. This is illustrated with one example of simulation plan on dairy farms to interpret the Nitrogen farm-gate budget indicator. It shows that this indicator is able to reflect small differences in Nitrogen losses between different systems, but it can only be interpreted using a mobile average, not on a yearly basis. This example illustrates how MELODIE could be used to study the dynamic behaviour of the system and the dynamic of nutrient flows. Finally, MELODIE can also be used for comprehensive multi-criterion assessments, and it also constitutes a generic and evolving framework for virtual experimentation on animal farming systems.

Modelling of manure production by pigs and NH3, N2O and CH4 emissions. Part I: animal excretion and enteric CH4, effect of feeding and performance.

A mathematical model was developed from literature data to predict the volume and composition of pig's excreta (dry and organic matter, C, N, P, K, Cu and Zn contents), and the emission of greenhouse gases (CH4 and CO2) though respiration and from the intestinal tract, for each physiological stage (post-weaning and fattening pigs and lactating and gestating sows). The main sources of variation considered in the model are related to animal performances (feed efficiency, prolificacy, body weight gain, etc.), to water and nutrient intakes and to housing conditions (ambient temperature). Model predictions were validated by using 19 experimental studies, most of them performed in conditions close to those of commercial farms. Validation results showed that the model is precise and robust when predicting slurry volume (R2 = 0.96), slurry N (R2 = 0.91), P (R2 = 0.95) and to a lesser extent dry matter (R2 = 0.75) contents. Faeces and urine composition (minerals and macronutrients) can also be precisely assessed, provided the composition and the digestibility of the feed are well known. Sensitivity analysis showed strong differences in CH4 emission and excretion amounts and composition according to physiological status, animal performance, temperature and diet composition. The model is an efficient tool to calculate nutrient balances at the animal level in commercial conditions, and to simulate the effect of production alternatives, such as feeding strategy or animal performance, on excreta production and composition. This is illustrated by simulations of three feeding strategies, which demonstrates important opportunities to limit environmental risks through diet manipulations.

Modelling of manure production by pigs and NH3, N2O and CH4 emissions. Part II: effect of animal housing, manure storage and treatment practices.

A model has been developed to predict pig manure evolution (mass, dry and organic matter, N, P, K, Cu and Zn contents) and related gaseous emissions (methane (CH4), nitrous oxide (N2O) and ammonia (NH3)) from pig excreta up to manure stored before spreading. This model forms part of a more comprehensive model including the prediction of pig excretion. The model simulates contrasted management systems, including different options for housing (slatted floor or deep litter), outside storage of manure and treatment (anaerobic digestion, biological N removal processes, slurry composting (SC) with straw and solid manure composting). Farmer practices and climatic conditions, which have significant effects on gaseous emissions within each option, have also been identified. The quantification of their effects was based on expert judgement from literature and local experiments, relations from mechanistic models or simple emission factors, depending on existing knowledge. The model helps to identify relative advantages and weaknesses for each system. For example, deep-litter with standard management practices is associated with high-greenhouse gas (GHG) production (+125% compared to slatted floor) and SC on straw is associated with high NH3 emission (+15% compared to slatted floor). Another important result from model building and first simulations is that farmer practices and the climate induce an intra-system (for a given infrastructure) variability of NH3 and GHG emissions nearly as high as inter-system variability. For example, in deep-litter housing systems, NH3 and N2O emissions from animal housing may vary between 6% and 53%, and between 1% and 19% of total N excreted, respectively. Thus, the model could be useful to identify and quantify improvement margins on farms, more precisely or more easily than current methodologies.

Effect of cattle grazing a species-rich mountain pasture under different stocking rates on the dynamics of diet selection and sward structure.

Although stocking rate is a key management variable influencing the structure and composition of pastures, only few studies have simultaneously analysed the seasonal patterns of pasture use by cattle, and the adjustments the animals make to maintain intake of a high-quality diet over the grazing season. Therefore, over a 3-year study, we recorded diet selection, plot use and impact of heifers on sward structure and quality under three different stocking rates (0.6, 1.0 and 1.4 livestock units (LU) per ha) in a species-rich mountain pasture of central France. Measurements were made on three occasions between early June and the end of September each year. Overall, heifers selected for bites dominated by legumes or forbs, and against reproductive grass, whatever the stocking rate or season. Selection for tall mixed (P < 0.05), short mixed (P < 0.05) and short pure grass bites (P < 0.01) was more pronounced in plots grazed at the lowest stocking rate. Although heifers' selection for short patches decreased at the end of the season (P < 0.001), they continued to graze previously grazed areas, thus exhibiting a typical 'patch grazing' pattern, with the animals that grazed at the lowest stocking rate tending to better maintain their selection for short patches in September (treatment × period: P = 0.078). Neither diet quality nor individual animal performance were affected by the different stocking rate treatments despite high variability in the quantity and quality of herbage offered and differences in diet selection. However, at the 1.4 LU per ha stocking rate, the quantity of forage available per animal at the end of the season, 0.79 t dry matter (DM) per ha of green leaves with the median of sward height at 4.6 cm, approached levels limiting cattle's ability to compensate for the effects of increasing stocking rate. In plots grazed at 0.6 LU per ha, the total herbage biomass remained higher than 3 t DM per ha with more than 30% of plot area still covered by reproductive grass patches at the end of the grazing season, which in the medium term should affect the botanical composition of these pastures. Sward heterogeneity was high in plots grazed at 1.0 LU per ha, with sufficient herbage availability (1.1 t DM per ha of green leaves) to maintain animal performance, and more than 15% of plot area was kept at a reproductive stage at the end of the grazing season. Hence, it could represent the optimal balance to satisfy both livestock production and conservation management objectives.

Heterogeneity of alpha-2 adrenoceptors in pregnant rat uterus: identification of subtypes and autoradiographic distribution.

Pharmacological characterization of alpha-2 adrenoceptors of the pregnant rat myometrium was assessed using the ability of various alpha adrenoceptor agonists and antagonists to inhibit [3H]rauwolscine or [3H]idazoxan binding to myometrial 50,000 x g fraction or to slide-mounted sections of the whole pregnant uterus. Saturation binding studies with both radioligands showed that the number of myometrial alpha-2 adrenoceptors is greatly increased on days 10 to 12 of pregnancy vs. cyclic rats. It then decreased from midpregnancy to term (about -75%; P < .01) with no change of the equilibrium dissociation constant (between 7-11 nM). Chemical sympathectomy by 6-hydroxydopamine significantly decreased (P < .01) the density of alpha-2 adrenoceptors at days 8 and 12 of pregnancy. Later, 6-hydroxydopamine administration did not alter Bmax or Kd values suggesting that the pregnancy decrease of alpha-2 adrenoceptors may be related to a loss of presynaptic receptors. In order to identify myometrial postsynaptic alpha-2 adrenoceptor subtypes, the inhibition of [3H]rauwolscine or [3H]idazoxan binding by oxymetazoline, prazosin and chlorpromazine was studied on days 20 and 21 of pregnancy. All inhibition curves were consistent with a model of two classes of binding sites: about 55% of the myometrial alpha-2 adrenoceptors, which had a higher affinity for oxymetazoline, may represent the alpha-2A subtype whereas the other 45% of the sites, which had a higher affinity for prazosin and chlorpromazine, may represent the alpha-2B subtype. Autoradiographic studies using [3H]rauwolscine revealed that both subtypes are colocalized in the longitudinal muscle. A high density of alpha-2A and alpha-2B subtypes was also detected in the chorioallantoic and yolk sac placenta and in the embryonic nervous system.

Selective distribution of alpha-1 and beta adrenoceptors in pregnant rat uterus visualized by autoradiography.

Receptor autoradiography using (-)-3-[125I]cyanopindolol and [3H]prazosin was used to study the distribution of beta and alpha-1 adrenoceptors in the rat uterus at early and midpregnancy. The binding of [3H]prazosin to slide-mounted sections at 25 degrees C was time dependent (K1 = 3.01 x 10(7) M-1 min-1, K2 = -0.0116 min-1) and saturable (1 nM). Competition binding curves with the selective alpha-1 and alpha-2 antagonists (prazosin, yohimbine) or alpha-1 and alpha-2 agonists (phenylephrine, clonidine) showed the presence of alpha-1 adrenoceptors; autoradiographic studies revealed that this subtype is highly localized in the circular layer of the myometrium during pregnancy. (-)-3-[125I]Cyanopindolol binding to slide-mounted sections of the pregnant uterus at 25 degrees C was time dependent (K1 = 4.68 x 10(8) M-1 min-1, K2 = -0.0117 min-1) and saturable (200 pM). Competition binding curves with beta-1 or beta-2 selective agonists (dobutamine, metaproterenol) and antagonists (atenolol, ICI 118,551) revealed the presence of beta adrenoceptors in the proportion of 67% beta-2 to 33% beta-1. Hyperfilm exposed to sections of the whole pregnant uterus incubated with (-)-3-[125I]cyanopindolol with or without ICI 118,551 or atenolol showed a high density of beta-2 adrenoceptors in the longitudinal layer of the myometrium and in the placenta. A small density of beta-2 adrenoceptors was also located in the decidua basalis on day 8 of pregnancy.

Comparative effects of 6-hydroxydopamine and alpha-adrenoceptor antagonists on intrauterine migration and spacing of blastocysts in the rat.

Sympathetic nerve terminals were destroyed by administration of 6-hydroxydopamine (2 x 50 mg/kg) at 10:00 h on Days 4 and 5 of pregnancy in the rat. In the myometrium, this treatment markedly decreased noradrenaline concentrations (by 99%, P less than 0.001), demonstrating that myometrial noradrenaline is mainly originated from sympathetic nerves; therefore after 6-hydroxydopamine, the distribution and spacing of blastocysts remain unaffected throughout the uterus. Administration of phenoxybenzamine (2 x 6 mg/kg) in the morning of Days 4 and 5, or prazosin (4 x 3 mg/kg) from 12:00 h on Day 4 until 12:00 h on Day 5 disorganized the even distribution of blastocysts from the tubal end to the cervical end of the uterine horns. These results provide evidence that a noradrenergic transmission via action on myometrial post-synaptic alpha 1-adrenoceptors is involved as a regulatory mechanism of uterine motility for distribution and spacing of blastocysts in the rat uterus.

Molecules and the body plan: the Hox genes of Cirripedes (Crustacea).

Among arthropods, Cirripedia (barnacles) are remarkable in that they completely lack abdominal segments. This feature prompted us to study the Hox genes of three cirripede species, representing a wide array of the diversity of these organisms, a segmented sessile barnacle, Elminius modestus (Thoracica), the parasite of a crab, Sacculina carcini (Rhizocephala), and the burrowing barnacle Trypetesa lampas (Acrothoracica). Using PCR amplification of genomic DNA and cDNA and library probing, we have found seven clear cirripedian homologues of the eight homeotic Hox genes known in insects, including labial and proboscipedia homologues, that were not previously reported in crustaceans. In addition we have isolated a divergent Antp-like gene, named Diva, that we homologize to the ftz gene of insects. The homeotic gene abdominalA (abdA) was not retrieved from any of these three cirripede species. By contrast, we have found all eight homeotic homologue genes, including abdA, in Ulophysema oeresundense, a crustacean possessing a well-developed abdomen, belonging to the Ascothoracica, generally thought to be the sister group of Cirripedia. Since we have found in barnacles homeobox-containing genes that are more divergent from the Antennapedia type than the typical abdA, we believe that a bona fide abdA gene would not have escaped our search. Hence, the abdA gene has been lost or is profoundly derived in sequence during the evolution leading to the cirripedian lineage. If confirmed, the lack of abdA would represent the first case in which the loss of a homeotic gene is correlated with a change in body plan during the evolution of metazoans.