Emmanuel Tillard

The use of multilevel models to evaluate sources of variation in reproductive performance in dairy cattle in Reunion Island.

Sources of variation in measures of reproductive performance in dairy cattle were evaluated using data collected from 3207 lactations in 1570 cows in 50 herds from five geographic regions of Reunion Island (located off the east coast of Madagascar). Three continuously distributed reproductive parameters (intervals from calving-to-conception, calving-to-first-service and first-service-to-conception) were considered, along with one Binomial outcome (first-service-conception risk). Multilevel models which take into account the hierarchical nature of the data were used to fit all models. For the overall measure of calving-to-conception interval, 86% of the variation resided at the lactation level with only 7, 6 and 2% at the cow, herd and regional levels, respectively. The proportion of variance at the herd and cow levels were slightly higher for the calving-to-first-service interval (12 and 9%, respectively) - but for the other two parameters (first-service-conception risk and first-service-to-conception interval), >90% of the variation resided at the lactation level. For the three continuous dependent variables, comparison of results between models based on log-transformed data and Box-Cox-transformed data suggested that minor departures from the assumption of normality did not have a substantial effect on the variance estimates. For the Binomial dependent variable, five different estimation procedures (penalised quasi-likelihood, Markov-Chain Monte Carlo, parametric and non-parametric bootstrap estimates and maximum-likelihood) yielded substantially different results for the estimate of the cow-level variance.

Economic value of greenhouse gases and nitrogen surpluses: Society vs farmers’ valuation

Livestock supply must challenge the growth of final demand in the developing countries. This challenge has to take into account its ecological effects since the dairy and livestock sectors are clearly pointed out as human activities which contribute significantly to environmental deterioration. Therefore, livestock activity models have to include desirable and undesirable outputs simultaneously. Using this perspective, we implement a Data Envelopment Analysis model to evaluate shadow prices of outputs under contradictory objectives between the society and the farmers. We show that farmers are able to reduce pollution significantly if society accepts to balance farmers’ opportunity cost. Finally, we observe that initial levels of the CO2 tax implemented in European countries are in line with farmers’ valuation while the current level of the CO2 tax tends to reach the value of pollution targeted by the society.

A steady-state approach of benefit–cost analysis with a periodic Leslie-matrix model: Presentation and application to the evaluation of a sheep-diseases preventive scheme in Kolda, Senegal

A seasonal population-dynamics matrix model (periodic Leslie-matrix model) was developed to model short production cycles and high seasonal variations occurring in demographic rates and offtake patterns for small ruminants. The year was split into 24- and 15-day phases. Population-size changes were modelled by the recurrence equation x(j+1)=B(j)x(j), where j was the 15-day phase, x an age-class population size vector and B a fecundity-, mortality-, offtake- and intake-rate matrix. Given an initial vector x(1), annual dynamics were described by x(25)=B(24)...B(1)x(1)=Ax(1), where A was the annual projection matrix.A steady-state hypothesis was used to estimate offtake gains and financial returns from a trial of pasteurellosis vaccination and anthelminthic drench in traditionally managed sheep flocks in Senegal, from July 1987 to June 1988. Nineteen villages and 76 herds were involved in the experiment. Villages were randomly allocated to one of the four treatment combinations in a factorial design, and subsequent demographic rates and net offtake patterns were measured. In the trial, vaccination had a negative effect on offtakes among females. No vaccination effect was observed for males. A positive effect of deworming was found for both sexes. From the trial data, our model calculated that the overall ratio of offtakes (i.e. number of animals) for dewormed over undrenched sheep was 1.2 (95% confidence interval: 1.1, 1.4). The deworming financial benefit-cost ratio was 3.7 (1.9, 5.4).

“Global” and “local” predictions of dairy diet nutritional quality using near infrared reflectance spectroscopy

The objective of the study was to evaluate performance of classic (global) and innovative (local) calibration techniques to monitor cattle diet, based on fecal near infrared reflectance spectroscopy (NIRS). A 3-yr on-farm survey (2005-2008) was carried out in Vietnam and La Reunion Island to collect animal, feed intake, and feces excretion data. Feed and feces were scanned by a Foss NIRsystem 5000 monochromator (Foss, Hillerød, Denmark) to estimate diet characteristics and nutrient digestibility. A data set including 1,322 diet-fecal pairs was built and used to perform global and local calibrations. Global equations gave satisfactory accuracy [coefficient of determination (R(2)) >0.8, 10% ≤ relative standard error of prediction (RSEP) ≤20%], whereas local equations gave good accuracy (R(2) >0.8, RSEP <10%) or excellent accuracy (R(2) >0.9, RSEP <10%) for the prediction of diet intake, quality, and digestibility. When validating the equations using the external individual data, both techniques were robust, with similar RSEP (8%) and R(2) (0.82) values. The predictive performance of global and local equations was improved (RSEP = 5% and R(2)=0.90) when averaged animal data from farm, visit, and similar milk production were used. In particular, local equations reduced RSEP by 43% and increased R(2) by 15%, on average, compared with those obtained from individual data. The low RSEP (4%), high R(2) (0.96), and good ratio performance deviation (RPD=5) illustrated the excellent accuracy and robustness of the local equations. Findings suggest the ability of fecal NIRS to successfully and more accurately predict diet properties (intake, quality, and digestibility) with local calibration techniques compared with classic global techniques, especially on an averaged data set. Local calibration techniques represent an alternative promising method and potentially a decision support tool to decide whether diets meet dairy cattle requirements or need to be modified.

Potential impacts of climate change on stable flies, investigated along an altitudinal gradient

Abstract Adult populations of stable flies were sampled along an altitudinal transect in Reunion Island to determine whether higher temperatures were associated with: (a) higher numbers of flies; (b) a longer season of infestation, and/or (c) different responses to warming in the cosmopolitan Stomoxys calcitrans (L) and the tropical Stomoxys niger niger Macquart (Diptera: Muscidae). Flies of both species were trapped at seven farms situated at four altitudes (100−1600 m a.s.l.) over a 90‐week period. For both species, there were no relationships between the maximum or mean fly abundance and altitude. Only minimum abundance in winter was significantly higher at lower altitudes. Maximum and mean abundances differed significantly between nearby farms under similar climatic conditions. Seasonal fluctuations in fly abundance changed along the gradient. At lower altitudes, population growth started earlier after the winter but abundance declined earlier in summer, which resulted in a shift of the season of infestation. Seasonal fluctuations of both species were strongly related to climate variables at high altitude, mainly temperature. However, climate variables explained a decreasing proportion of the variations in abundance at lower altitudes. Stomoxys calcitrans was the most abundant species overall, but the proportion of S. n. niger increased significantly at lower altitudes and this species became predominant at 100 m a.s.l. It is concluded that stable fly infestations are unlikely to worsen in response to global warming. Maximum abundance is limited by local factors, possibly larval resources, which suggests that adequate husbandry practices could override the impact of climate change. Because S. n. niger tends to be the predominant pest at elevated temperatures, it is recommended that this species should not be introduced in areas where climate is changing.

Genetic Structure and Gene Flow Along an Altitudinal Gradient Among Two Stomoxyine Species (Diptera: Muscidae) on La Réunion Island

Abstract Seasonal variations of insect population sizes are often dramatic, particularly in temperate regions and at altitudes where the climatic conditions are unfavorable to insect development during the winter. Decline of population size (or bottlenecks) and founder events may reduce the genetic variability and may create genetic differentiation between populations by drift and founder effects, but this reduction of genetic diversity is strongly influenced by gene flow between populations. In this study, we determined the population genetic structure for two stomoxyine species (Diptera: Muscidae), Stomoxys calcitrans (L.) and Stomoxys niger niger Macquart, which co-occur in dairy barns along an altitudinal gradient on La Réunion island. Using microsatellite markers, we quantified the genetic variation within and among populations for different altitudes. This study displays that, contrary to expectations, genetic diversity is not correlated with altitude and that genetic differentiation is not larger among high-altitude populations than among low-altitude populations. These results attest to the small drift and founder effects in high-altitude populations despite drastic decreases in population size during the winter. Furthermore, at the island scale, the populations of S. calcitrans were slightly differentiated, but those of S. niger niger were not. Together, the results revealed large levels of gene flow on La Réunion Island despite the dramatic geographic barriers, and they emphasize the importance of considering agricultural practices to restrict the dispersal of stomoxyines.

Graphical approaches to support the analysis of linear-multilevel models of lamb pre-weaning growth in Kolda (Senegal).

Linear-multilevel models (LMM) are mixed-effects models in which several levels of grouping may be specified (village, herd, animal, ellipsis). This study highlighted the usefulness of graphical methods in their analysis through: (1) the choice of the fixed and random effects and their structure, (2) the assessment of goodness-of-fit and (3) distributional assumptions for random effects and residuals. An LMM was developed to study the effect of ewe deworming with morantel on lamb pre-weaning growth in a field experiment involving 182 lambs in 45 herds and 10 villages in Kolda, Senegal. Growth was described as a quadratic polynomial of age. Other covariates were sex, litter-size and treatment. The choice of fixed and random effects relied on three graphs: (1) a trellis display of mean live-weight vs. age, to select main effects and interactions (fixed effects); (2) a trellis display of individual growth curves, to decide which growth-curve terms should be included as random effects and (3) a scatter plot of parameters of lamb-specific regressions (live-weight vs. quadratic polynomial of age) to choose the random-effects covariance structure.Age, litter-size, agexlitter-size, litter-sizextreatment and agexlitter-sizextreatment were selected graphically as fixed effects and were significant (p<0.05) in subsequent statistical models. The selection of random-effect structures was guided by graphical assessment and comparison of the Akaikes information criterion for different models. The final random-effects selected included no random effect at the village level but intercept, age and squared-age at the herd and lamb levels. The structure of the random-effects variance-covariance matrices were blocked-diagonal at the herd level and unstructured at the lamb level. An order-1 autoregressive structure was retained to account for serial correlations of residuals. Smaller residual variance at 90 days than at younger ages was modeled with a dummy variable taking a value of 1 at 90 days and 0 elsewhere.Ewe-deworming with morantel during the rainy season lead to higher lamb live-weights (probably related to a better ewe-nutrition and -health status). A positive correlation was demonstrated between early weight and growth rate at the population level (with important lamb and herd-level random deviations). The persistence of this correlation at older ages should be checked to determine whether early weights are good predictors of mature weights and ewe-reproductive lifetime performance.

Inter-supply Chain Recycling of Residues

The absence of relationships – or, worse, the presence of conflicting ones – between segments of various compartmentalized agri-chains that coexist in territories hinders the sustainable development of these agri-chains, and, more broadly, of the territories concerned. This chapter discusses how creating links to the territory by identifying synergies between these agri-chains or with other supply chains could help overcome this limitation. It also presents a set of analyses and conceptions of relationships between local segments of distinct agri-chains using socio-economic analyses and flow analyses. Although there do exist examples of spontaneous inter-supply chain recycling links, they are usually very short circuits, and are often opportunistic and unstable. Moreover, to this organizational instability can be added a less than optimal extraction of value from agricultural output. The analyses presented here suggest that significant potential for linkages between specialized segments of separate supply chains remains untapped, and this at different geographical scales. They also emphasize the importance of organization and coordination, which partly explains why exchanges at supra-farm scales develop rarely without external intervention. We can, however, use techniques to create or strengthen networks between actors from relatively compartmentalized segments on the basis of discovered mutual interests. It is a matter of encouraging industrial symbiosis. In this case, inter-supply chain relationships are seen as value chains that are short, localized, circular, and transversal. A general rule seems to emerge: the more one endeavours to tailor these relationships to contribute to sustainable development, the more complicated they become and the more difficult to build.

Modelling crop-livestock integration systems at a farm scale in a Highland region of Madagascar: a conceptual model

Introduction Malagasy Highland region of Vakinankaratra (19°51’S; 47°01’E) is the heart of the Madagascar dairy basin and generates 90% of the national dairy production. Farms are based on diverse crop rotations, where rise is the main crop, and livestock activities (dairy cows, zebus, pigs, poultry, etc.). The milk is produced by a multitude of smallholders (with less than five cows in average) which commonly feed animals with crop residues and natural vegetation. This region knows critical erosion problems and soil fertility degradation (Douzet et al., 2008) which increased with cover-crop and land over-using for agriculture and livestock feeding. In these complex traditional farming systems, integrative and interdisciplinary modelling tools are needed for better understanding crop-livestock interactions and identifying a compromise between resources allocation for livestock production and soil fertility improvement. The purpose of this work is to build a biophysical whole-farm computer model (milk and crop yields) for simulating at the farm scale the various flows of biomass occurring between the different compartments (cattle, crops, stocks of organic plant material, soil, organic fertilizers, etc.) in these mixed farming systems.

Agricultural Organic Waste Recycling to Reduce Greenhouse Gas Emissions

Organic waste recycling in agriculture can enhance the efficiency of nutrient cycles and directly or indirectly reduce major and increasing sources of greenhouse gas emissions. It can also boost soil fertility and agricultural resilience to climate change. There is considerable potential for improving recycling that has been studied from the farm to the territorial scale. We present research results concerning the improvement and introduction of recycling practices on several scales and concerning associated biophysical processes allowing more reliable assessment of greenhouse gas emission balances. Whether concerning the resilience of agricultural systems or the mitigation of emissions, the agricultural waste recycling potential is highest on the territorial scale, especially when the spatial concentration of various wastes is high, e.g. in periurban areas around fast-growing megacities in developing countries. CIRAD has developed recycling management methods and support tools and is enhancing knowledge on processes that determine the climate footprint of recycling. The aim is to fill the many knowledge gaps regarding greenhouse gas emission factors and determinants of organic matter bioprocessing in tropical conditions.