Modélisation et exploration d'un écosystème à dynamique spatiale par des outils de model-checking

The representation of large ecosystem is problematic, because of necessary needs to model it. New approaches are developed to answer this problem. This report offers à new qualitative approach to represent populations inside a landscape, which is evolving under human actions. The innovation is te modelling of population flows with timed automata, a qualitative modelling method. It has been possible to create a method, which starts from the modelling of a landscape and ends at the creation of its possible development and the analysis of the factors promoting agronomic and ecological criteria. However, the actual tools are still limited and do not permit real applications.La représentation de larges écosystèmes pose le problème des moyens nécessaires pour les modéliser. Pour cela, de nouvelles approches se développent pour pallier à ce problème. Ce rapport propose une nouvelle approche qualitative pour représenter des populations au sein d’un paysagesoumis à l’action humaine. L’innovation vient de la modélisation des flux de population entre différents éléments paysagers en utilisant des automates temporisés, une méthode de modélisation qualitative. Il a ainsi été possible de réaliser une méthode partant de la modélisation du paysage jusqu’à la génération de ses évolutions possibles, et l’analyse des facteurs favorisant les critères agronomiques et écologies étudiés. Cependant, les outils à disposition restent limités et ne permettent pas encore d’application réelle

L'évolution de la teneur en calcium du lait au cours de la lactation peut-elle être un indicateur de l'effet de l'alimentation sur les réserves osseuses des vaches laitières ?

During lactations, dairy cows faces huge calcium requirements due to milk production. Because of the fast increase in those requirements at the beginning of the lactation, the organism of dairy cows can hardly adapt by increasing intake and digestive calcium absorption. The organism must mobilize calcium from its storage pool, bones, which will replenish later in lactation. Those cycles of bone mobilization and reconstitution remain impossible to quantify for important number of dairy cows and the consequences of an incomplete bone reconstitution on following lactation remain unknown. The aim of this PhD was to develop an indicator of the phenomenon of bone mobilization and reconstitution during lactation.Several factors increasing bone mobilization have been identified, such as breed, parity or diet. However, the cycles of bone mobilization and reconstitution could not be related to variation in milk Ca and P content. However, it has been showed that, an insufficient Ca supply in early lactation does not always induce a higher bone mobilization, as it has been described in the literature, but can be compensated by an increase in digestive absorption capacity. The thesis also showed the need to quantify the consequences on insufficient dietary calcium supply on dairy cows’ milk production and health throughout lactation.Au cours de leur lactation, les vaches laitières font face à d’importants besoins en calcium du fait de la production laitière. L'augmentation très rapide de ces besoins en début de lactation fait que l’organisme des vaches peut difficilement s’adapter par une hausse de l’ingestion et de l’absorption digestive de calcium. L’organisme doit puiser dans les réserves osseuses, qui seront reconstituées plus tard en fin de lactation. Ces cycles de mobilisation et reconstitution osseuses restent cependant impossibles à quantifier chez la vache laitière sur de larges effectifs et les conséquences d’une mauvaise reconstitution osseuse sur les lactations suivantes restent inconnues. Cette thèse avait pour objectif de développer un indicateur des phénomènes de mobilisation et reconstitution osseuse au cours de la lactation.Plusieurs facteurs de mobilisation osseuse ont pu être identifiés, comme la race, la parité ou l’alimentation. Cependant, les cycles de mobilisation et de reconstitution osseuse n’ont pas pu être reliés à des variations de la composition du lait en Ca et P. Il a cependant pu être montré, que contrairement à ce qui est décrit dans la littérature, un apport insuffisant en Ca en début de lactation n’est pas toujours accompagné d’une augmentation de la mobilisation osseuse, mais peut être compensé par une augmentation des capacités d’absorption digestive. Cette thèse montre aussi la nécessité de quantifier les conséquences d’un apport insuffisant de calcium alimentaire sur les performances de production et la santé des vaches laitières sur l’ensemble de la lactation

Le calcium du lait de vache : un élément indispensable à la nutrition humaine et peut-être un indicateur du métabolisme osseux de la vache laitière ?

National audienc

Characterization of the nongenetic causes of variation in the calcium content of bovine milk on French farms

International audienceMilk is an important source of Ca in Western diets. Milk Ca is important for the cheesemaking process and could be a useful biomarker of Ca regulation in cows. The objective of this study was to identify and quantify nongenetic factors affecting the variation of Ca content in bovine milk. During the PhénoFinLait program, a survey was performed in 3 major areas of milk production in France. This survey consisted of collecting milk samples, together with information about herd management and cow nutrition, from 924 commercial farms. More than 200,000 individual milk samples were collected, and Ca content was measured by mid-infrared spectroscopy. Each farm was surveyed several times during the year, and 3 to 6 milk samples were collected from each cow. An equation to predict milk Ca content from mid-infrared spectra was developed based on the Ca contents of 292 milk samples, and the milk Ca contents of the 200,000 samples were then predicted. Milk Ca content was lowest in Holstein cows, intermediate in Montbéliarde cows, and highest in Normande cows. For all 3 breeds, milk Ca decreased during the first month of lactation and increased after the fourth month of lactation, with the range between minimum and maximum values largest in Holsteins, intermediate in Montbéliardes, and smallest in Normandes. Milk Ca content also decreased with parity in all 3 breeds. By using multiple factorial analysis, 6 major feeding strategies employed on French dairy farms were characterized based on the data from the survey. Calendar month and cow feeding strategy affected milk Ca content, which dropped in the spring during grazing turnout and was lower when cows were fed fresh and conserved grass rather than corn silage. In conclusion, environmental factors induce variations in milk Ca content in addition to the genetics of the cows, which to date have been identified as a main factor of variation of milk Ca content in dairy cows. In several of the tested conditions, increases in milk production and in the amount of Ca daily secreted in milk were associated with a decrease in milk Ca content as though the mammary gland operated to limit the exportation of Ca when milk production rapidly increased. This result would suggest that milk Ca content could be a biomarker of Ca regulation in dairy cows

Characterization of the non-genetic causes of variation of bovine milk calcium concentrations on French farms

Calcium concentration (CaC) in bovine milk has often been described as independent of feeding strategy and mainly dependent on cow genetics and lactation stage. However, isolated experiments showed that variations in milk CaC could be linked to the diet of cows. Our objective was to identify and quantify non-genetic factors of variation in CaC in milk samples collected from about a thousand French dairy farms with contrasting feeding strategies and cow breeds. This study was based on the PhénoFinlait program that consisted of a survey performed between 2009 and 2010 in 924 dairy farms located in the major French milk production areas. The breeds used in the investigated farms were Holstein, Normande and Montbeliarde. Each farm was visited on average 4 to 6 times during the year. Each time, information about cow diets and production were gathered and individual milk samples were collected to extract their mid-infrared (MIR) spectra. More than 200,000 MIR spectra were measured. Nearly 10,000 milk samples were also frozen and stored in a bank for further analyses. We estimated CaC in milk samples from their MIR spectra using a predictive equation. This equation was established from 300 milk samples extracted from the bank and chosen to represent the diversity of investigated dairy systems. From the composition of the cow diets collected at each survey, we characterized 7 feeding strategies using multiple factorial analyses across 3 periods: winter, early and late summer. For each breed, the variations in milk CaC were quantified by ANOVA with a model including the effects of feeding strategies, stage of lactation, parity, and calendar month as fixed effects and the cow as random effect. The feeding strategy affected milk CaC with the constant fact that the diets based on fresh or conserved grass induced lower milk CaC whatever the month of the year (P < 0.05). The difference in CaC can be up to 100 mg/kg between 2 extreme diets at a given month, which is as important as the drop in CaC observed at the beginning of lactation. This study reinforces the idea that the diet of cows has an influence on milk CaC

Effet d’une restriction des apports en calcium en début de lactation sur la production laitière, la composition du lait et les dynamiques de mobilisation et de reconstitution osseuses au cours de la lactation chez la vache laitière

The objective of this experiment was to evaluate the consequences of an increase of bone mobilization in early lactation, on the milk contents of Ca and P and the bone reconstitution dynamics in late lactation. Fifteen multiparous Holstein cows have been spread between three treatments 5 weeks before the expected calving date. Those treatments consisted in differentiating the cow’s diets between 5 days and 10 weeks of lactation. The control treatment (TEM) consisted in a diet covering 100% of the Ca requirements, the treatments BCa and BCaBE consisted in a diet covering 70% of the Ca requirements, the dietary anion-cation difference was 200 mEq/Kg DM for TEM and BCa and 0 for BCaBE. The treatments BCa and BCaBE induced a small decrease of the body retention of Ca at 3 weeks of lactation compared with the treatment TEM (P< 0.09) but did not affect either the dynamics of blood biomarkers of bone accretion and resorption during the 32 weeks of lactation or the body retention of Ca at 17 weeks of lactation. Cows almost entirely compensated the decrease of Ca supply in BCa and BCaBE treatments by an increase of the apparent absorption of Ca at 3 weeks of lactation (P = 0.03). Treatments did not clearly affect either the milk composition. Nevertheless, milk yield tended (P = 0.09) to be lower throughout the lactation with treatments BCa and BCaBE compared with TEM with a mean difference of 2 kg/d between TEM treatment and BCa and BCaBE treatments.Les objectifs de cet essai étaient d’évaluer les conséquences d’une augmentation de la mobilisation osseuse de vache laitière en début de lactation sur les teneurs en Ca et en P du lait et la dynamique dereconstitution osseuse en fin de lactation. Quinze vaches laitières Holstein multipares ont été réparties en trois lots différents 5 semaines avant la date planifiée de vêlage. Chaque lot recevait un traitement différent, consistant àdifférentier l’alimentation des vaches entre 5 jours et 10 semaines de lactation. Le traitement témoin (TEM) consistait en une ration couvrant 100 % des besoins en Ca, les traitements BCa et BCaBE consistaient en desrations couvrant 70% des besoins en Ca, le bilan alimentaire cation-anion étant de 200 mEq/Kg MS pour TEM et BCa, et 0 pour BCaBE. Les traitements BCa et BCaBE ont eu tendance à diminuer légèrement la rétentioncorporelle de Ca à 3 semaines de lactation (P< 0.09) par rapport au traitement TEM mais n’ont eu d’effet ni sur la dynamique des teneurs en biomarqueurs d’accrétion et de résorption osseuse au cours des 32 semaines delactation, ni sur la rétention corporelle du Ca à 17 semaines de lactation. Les vaches ont presque entièrement compensé la baisse des apports en Ca par une élévation de l’absorption apparente du Ca à 3 semaines delactation (P = 0.03). Les traitements n’ont pas eu d’effet sur la composition du lait. Par contre la production laitière a eu tendance (P = 0.09) à être plus faible sur l’ensemble de la lactation avec les régimes BCa et BCaBE parrapport à TEM, avec une différence moyenne de 2 kg/j

Effect of calcium intake and the dietary cation-anion difference during early lactation on the bone mobilization dynamics throughout lactation in dairy cows

This study investigated the consequences of a low supply of dietary Ca with or without a low dietary cation-anion difference (DCAD) during early lactation on bone mobilization and reconstitution during lactation and on the dynamics of milk Ca content. Fifteen multiparous Holstein cows were distributed among 3 treatments 5 weeks before their expected calving date. These treatments differed based on the provision of diets through the first 10 weeks of lactation. During this period, the control treatment (NCa) consisted of a diet providing 100% of the Ca requirement, with a DCAD of 200 mEq/kg dry matter (DM). The LCa (low Ca) and LCaLD (low Ca, low DCAD) treatments consisted of diets providing 70% of the Ca requirement, with a DCAD of 200 and 0 mEq/kg DM, respectively. After 10 weeks, all cows received the same total mixed ration, which was formulated to meet 100% of the Ca requirement. LCa and LCaLD tended to decrease the body retention of Ca at 3 weeks of lactation compared with NCa but affected neither the dynamics of the blood biomarkers of bone formation and resorption during lactation nor the body retention of Ca at 17 weeks of lactation. Cows almost entirely compensated for the decrease in Ca supply caused by LCa and LCaLD by increasing their apparent digestive absorption of Ca at 3 weeks of lactation, whereas their apparent digestive absorption was unaffected by the treatments at 17 weeks of lactation. Milk production tended to be lower throughout lactation with LCa and LCaLD compared with NCa, with a mean difference of 2 kg/d. The results of this study also indicated that measuring the dynamics of milk Ca content during lactation cannot be considered effective for indirectly estimating the dynamics of bone mobilization in cows. The results also suggested that limited Ca intake at the beginning of lactation may have deleterious effects on milk production

Effet d’une restriction des apports en calcium en début de lactation sur la production laitière, la composition du lait et les dynamiques de mobilisation et de reconstitution osseuses au cours de la lactation chez la vache laitière

Les objectifs de cet essai étaient d’évaluer les conséquences d’une augmentation de la mobilisation osseuse de vache laitière en début de lactation sur les teneurs en Ca et en P du lait et la dynamique de reconstitution osseuse en fin de lactation. Quinze vaches laitières Holstein multipares ont été réparties en trois lots différents 5 semaines avant la date planifiée de vêlage. Chaque lot recevait un traitement différent, consistant à différentier l’alimentation des vaches entre 5 jours et 10 semaines de lactation. Le traitement témoin (TEM) consistait en une ration couvrant 100 % des besoins en Ca, les traitements BCa et BCaBE consistaient en des rations couvrant 70% des besoins en Ca, le bilan alimentaire cation-anion étant de 200 mEq/Kg MS pour TEM et BCa, et 0 pour BCaBE. Les traitements BCa et BCaBE ont eu tendance à diminuer légèrement la rétention corporelle de Ca à 3 semaines de lactation (P< 0.09) par rapport au traitement TEM mais n’ont eu d’effet ni sur la dynamique des teneurs en biomarqueurs d’accrétion et de résorption osseuse au cours des 32 semaines de lactation, ni sur la rétention corporelle du Ca à 17 semaines de lactation. Les vaches ont presque entièrement compensé la baisse des apports en Ca par une élévation de l’absorption apparente du Ca à 3 semaines de lactation (P = 0.03). Les traitements n’ont pas eu d’effet sur la composition du lait. Par contre la production laitière a eu tendance (P = 0.09) à être plus faible sur l’ensemble de la lactation avec les régimes BCa et BCaBE par rapport à TEM, avec une différence moyenne de 2 kg/j.The objective of this experiment was to evaluate the consequences of an increase of bone mobilization in early lactation, on the milk contents of Ca and P and the bone reconstitution dynamics in late lactation. Fifteen multiparous Holstein cows have been spread between three treatments 5 weeks before the expected calving date. Those treatments consisted in differentiating the cow’s diets between 5 days and 10 weeks of lactation. The control treatment (TEM) consisted in a diet covering 100% of the Ca requirements, the treatments BCa and BCaBE consisted in a diet covering 70% of the Ca requirements, the dietary anion-cation difference was 200 mEq/Kg DM for TEM and BCa and 0 for BCaBE. The treatments BCa and BCaBE induced a small decrease of the body retention of Ca at 3 weeks of lactation compared with the treatment TEM (P< 0.09) but did not affect either the dynamics of blood biomarkers of bone accretion and resorption during the 32 weeks of lactation or the body retention of Ca at 17 weeks of lactation. Cows almost entirely compensated the decrease of Ca supply in BCa and BCaBE treatments by an increase of the apparent absorption of Ca at 3 weeks of lactation (P = 0.03). Treatments did not clearly affect either the milk composition. Nevertheless, milk yield tended (P = 0.09) to be lower throughout the lactation with treatments BCa and BCaBE compared with TEM with a mean difference of 2 kg/d between TEM treatment and BCa and BCaBE treatments

Effect of parity and age at first calving of dairy cows on dynamics of milk calcium contents and blood biomarkers of bone accretion and resorption throughout lactation

Effect of parity and age at first calving of dairy cows on dynamics of milk calcium contents and blood biomarkers of bone accretion and resorption throughout lactation. 10. International Symposium on the Nutrition of Herbivores (ISNH