An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows

To simulate the consequences of management in dairy herds, the use of individual-based herd models is very useful and has become common. Reproduction is a key driver of milk production and herd dynamics, whose influence has been magnified by the decrease in reproductive performance over the last decades. Moreover, feeding management influences milk yield (MY) and body reserves, which in turn influence reproductive performance. Therefore, our objective was to build an up-to-date animal reproduction model sensitive to both MY and body condition score (BCS). A dynamic and stochastic individual reproduction model was built mainly from data of a single recent long-term experiment. This model covers the whole reproductive process and is composed of a succession of discrete stochastic events, mainly calving, ovulations, conception and embryonic loss. Each reproductive step is sensitive to MY or BCS levels or changes. The model takes into account recent evolutions of reproductive performance, particularly concerning calving-to-first ovulation interval, cyclicity (normal cycle length, prevalence of prolonged luteal phase), oestrus expression and pregnancy (conception, early and late embryonic loss). A sensitivity analysis of the model to MY and BCS at calving was performed. The simulated performance was compared with observed data from the database used to build the model and from the bibliography to validate the model. Despite comprising a whole series of reproductive steps, the model made it possible to simulate realistic global reproduction outputs. It was able to well simulate the overall reproductive performance observed in farms in terms of both success rate (recalving rate) and reproduction delays (calving interval). This model has the purpose to be integrated in herd simulation models to usefully test the impact of management strategies on herd reproductive performance, and thus on calving patterns and culling rate

A milk urea model to better assess nitrogen excretion and feeding practice in dairy systems

A milk urea model to better assess nitrogen excretion and feeding practice in dairy systems. 20. Nitrogen Worksho

Variation in the inter-service intervals of UK dairy cows

An understanding of the normal estrous cycle length of the cow is important when managing and monitoring dairy herd fertility. Whilst the normal inter-ovulatory interval is widely considered to be 21 days, some studies have found alternative intervals to be more prevalent; previously most of the variation in interval length was expected to be between cows. The aim of this study was to assess the time between inseminations (inter-service interval, ISI), in a large number of dairy cows and to explore possible associations between cow factors and estrous cycle length. The study used ISI data from 42,252 cows in 159 herds across England and Wales. Univariate analysis of the subset of 114,572 intervals between 15 and 30 days (a range covering the increased frequency of ISIs occurring at the expected time of the first return to estrus) following an insemination revealed a modal ISI of 22 days. Primiparous heifers had a modal ISI of 21 days. There were significant differences between the distribution of ISIs for different yield groups, parity numbers and the number of inseminations. Multilevel regression modelling was used to evaluate the associations between cow factors and ISI, whilst accounting for clustering at the herd and cow level. This revealed significant associations between predicted ISI and insemination number, days in milk, lactation 305 day milk yield, and month and year of insemination. Variance partition coefficients indicated that only 1% of variation in ISIs was at the herd level, 12% at the animal level and 87% at the insemination level, indicating that cycle length varies substantially more between cycles within a cow than between cows or herds. These findings suggest the “normal” range of ISI for modern UK dairy cows is longer than expected and that there is a large amount of unexplained variation in cycle length within individual animals over time

Modélisation du fonctionnement d'un troupeau laitier pour anticiper les conséquences de son pilotage

Avec la fin programmée des quotas et la volatilité des prix du lait et des intrants, les éleveurs ont besoin d'outils pour anticiper les conséquences de leurs décisions sur les performances du troupeau. Cette thèse a permis l'élaboration d'un modèle de fonctionnement du troupeau individu-centré, dynamique et stochastique, sensible à la conduite : SITEL. Ce modèle comporte trois systèmes en interaction : le système biotechnique, composé des vaches et des génisses, le système décisionnel, qui simule les décisions et actions de l'éleveur, et le système d'information, qui représente la connaissance qu'a l'éleveur de son troupeau. Un modèle dynamique de la lactation capable de simuler la partition d'énergie et de protéines au cours de la lactation en fonction des rations consommées a été conçu, notamment par l'analyse d'une expérimentation étudiant les interactions entre énergie et protéines. De plus, un modèle individuel de la reproduction sensible à l'état physiologique et nutritionnel de l'animal a été développé à partir de données issues d'une expérimentation long terme comparant plusieurs systèmes d'alimentation. Enfin, la modélisation explicite du système d'information a permis de montrer que l'effet de la qualité de l'information sur les performances du troupeau variait en fonction du système d'élevage. Le modèle troupeau SITEL est ainsi un des premiers modèles simulant l'impact des différents leviers de conduite sur la dynamique du troupeau et ses productions en considérant de nombreuses interactions liées à l'alimentation et la reproduction en particulierGiven the planned end of milk production quotas and the volatility of milk and inputs prices, farmers need tools to preempt the effects of their decisions on herd performance. The present work made it possible to build a dynamic, stochastic and management-sensitive individual-based dairy herd model : SITEL. This model is composed of three interacting systems : the biotechnical system composed of both cows and heifers, the decisional system, simulating the farmer's decisions and actions, and the information system, representing the farmer's information level about his herd. A dynamic diet-sensitive lactation model able to simulate the partition of energy and protein during lactation was conceived, notably from the analysis of an experiment studying the energy x protein interactions. Moreover, an individual reproduction model sensitive to the physiological and nutritional state of the animal was developed from data of a long term experiment that compared several feeding systems. Finally, the explicit representation of the information system enabled to show that the effect of the quality of information on herd performance was different according to the breeding system. The SITEL herd model is therefore one of the first to simulate the impact of the various technical levers on herd dynamics and productions, taking into consideration numerous interactions particularly related to feeding and reproduction.RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF

Predicting energy x protein interaction on milk yield and milk composition in dairy cows

Feed management is one of the principal levers by which the production and composition of milk by dairy cows can be modulated in the short term. The response of milk yield and milk composition to variations in either energy or protein supplies is well known. However, in practice, dietary supplies of energy and protein vary simultaneously, and their interaction is still not well understood. The objective of this trial was to determine whether energy and protein interacted in their effects on milk production and milk composition and whether the response to changes in the diets depended on the parity and potential production of cows. From the results, a model was built to predict the response of milk yield and milk composition to simultaneous variations in energy and protein supplies relative to requirements of cows. Nine treatments, defined by their energy and protein supplies, were applied to 48 cows divided into 4 homogeneous groups (primiparous or multiparous x high or low milk potential) over three 4-wk periods. The control treatment was calculated to cover the predicted requirements of the group of cows in the middle of the trial and was applied to each cow. The other 8 treatments corresponded to fixed supplies of energy and protein, higher or lower than those of the control treatment. The results highlighted a significant energy x protein interaction not only on milk yield but also on protein content and yield. The response of milk yield to energy supply was zero with a negative protein balance and increased with protein supply equal to or higher than requirements. The response of milk yield to changes in the diet was greater for cows with high production potential than for those with low production potential, and the response of milk protein content was higher for primiparous cows than for multiparous cows. The model for the response of milk yield, protein yield, and protein content obtained in this trial made it possible to predict more accurately the variations in production and composition of milk relative to the potential of the cow because of changes in diet composition. In addition, the interaction obtained was in line with a response corresponding to the more limiting of 2 factors: energy or protein

Modélisation individuelle de la reproduction des vaches Holstein intégrant les effets de la production laitière et des réserves corporelles

La reproduction est un élément déterminant de la productivité et de la démographie des troupeaux. La dégradation des performances de reproduction au cours des dernières décennies a réduit la longévité des vaches et allongé les lactations. Ces performances sont sensibles à la production laitière et à l’état corporel, eux-mêmes influencés par la conduite du troupeau, notamment son alimentation. Les modèles de simulation individu-centrés permettent de simuler les conséquences des pratiques d’élevage sur les performances des troupeaux laitiers et d’estimer leur variabilité. Un modèle individuel dynamique et stochastique de la reproduction a donc été développé pour la race Holstein à partir de données issues d’une expérimentation récente. Ce modèle couvre le processus de reproduction dans sa globalité et est composé d’une succession d’événements tels que le vêlage, les ovulations, la fécondation et l’éventuelle interruption de gestation. Chaque étape est sensible à la production laitière, à la note d’état corporel ou à leurs variations. Le modèle prend en considération les évolutions récentes des caractéristiques reproductives des vaches, notamment concernant la cyclicité (fréquence des anomalies, durée des cycles), l’expression des chaleurs et les composantes de la fertilité (non-fécondation ou mortalité embryonnaire précoce, mortalité embryonnaire tardive). Une analyse de sensibilité du modèle à la production laitière et à la note d’état corporel au vêlage a été réalisée. L'intervalle entre vêlages et le taux de vêlage simulés sont cohérents avec les résultats observés dans les troupeaux français de race Holstein. Ce modèle pourrait être utilisé dans les modèles de fonctionnement du troupeau pour tester l’effet sur la démographie et la production du troupeau de différentes stratégies d’élevage, notamment la conduite de l’alimentation et de la reproduction.Reproduction is a key-driver of milk productivity and herd demography. The decline in reproductive performance over the last decades has decreased the life span of cows and increased the length of lactation. This performance is affected by variations in milk yield and body condition score, which in turn are influenced by herd management, in particular feeding management. Individual-based herd simulation models enable the simulation of the consequences of different management strategies on dairy herd performance and the assessment of its variability. A dynamic and stochastic individual reproduction model was developed for the Holstein breed from data from a recent experiment. This model covered the whole reproductive process and was composed of a succession of discrete events, namely calving, ovulations, conception and possible pregnancy interruption. Each stage in reproduction was affected by milk yield, body condition or their changes. The model takes into account recent evolutions in reproductive performance, in particular concerning cyclicity (frequency of abnormalities, cycle length), poor oestrous expression and fertility parameters (fertilisation failure or early embryonic loss, late embryonic loss). The sensitivity of the model to milk yield and body condition score at calving was tested. The simulated calving interval and re-calving rate were consistent with the reproductive performance observed in French Holstein herds. This model could be used in herd simulation models to test the effects of management strategies (feeding and reproductive management) on herd production and demography

Effect of spring grazing on milk somatic cell counts and intramammary infection of dairy goats milked once daily

National audienc

CarSolEl, a user-friendly tool to predict carbon stocks evolution in grassland-based farms

International audienceMaintaining or increasing soil organic carbon (SOC) stocks is crucial to meet the 2050 carbon neutrality target. The contribution of crop and grassland to SOC stocks was shown to be variable in France according to the soil, climate, and management situations. To assist farmers assessing how their land use and management modifies SOC stocks, a user-friendly interactive tool was developed. This tool is based on random decision forests built on fine gridded model simulations of SOC changes over France, carried out within the framework of the ‘4p1000’ INRAE study. The tool estimates a 30-year SOC evolution (0-30cm layer) for three land use types: permanent grasslands, and crop rotations with and without temporary grassland. The tool inputs are 26 easily available information sources related to soil, climate, and length of the rotation (including the share of grassland and cover crops), fertilization and irrigation practices and grass management. The tool is a good approximation of complex process-based crop and grassland models. It is therefore a promising tool for estimating in situ SOC evolution of livestock farms