Study On Simulation Of Variable Patterns Of Blood Metabolites And Production Performance Of Holstein Cows

Models are representations of reality. Mathematical models have been used in the researches fieldsof nutrition, metabolism and biomedicine very early. As a kind of tools for simulating real situations,many models can link theoretical knowledge and practical work experience together, and be used topredict nutrient requirement, improve performance, increase feed utilization and finally reduce cost ofproduction. Because of the complexity of physiological conversion and regulating processes from feednutrient to dairy production, mathematical modeling technology can be used to explain and simulatethese processes, when we are studying on milk quality. Mathematical modeling technology is becomingone of the most important methods in animal nutrition research.Based on the changes of blood metabolites concentrations and production performances indifferent diets, different weeks of lactation, or different months and parities, this paper established acurve-fitting method for the study on changes of blood metabolites concentrations and productionperformances.The first trial was conducted to investigate the effect of corn straw (CS) and qualified mixed forage(MF) as basal diets on dry matter intake (DMI), milk yield (MY) and milk composition in Holsteincows. The result showed that the effects of CS and MF on DMI, MY and milk composition wereinsignificant (P>0.05), but the interaction between diets and weeks of lactation could influence DMIand MY significantly (P <0.01). Dijkstra model could be used to fit the curves of DMI and MY, andWood model was more appropriate for milk composition.In the second trial, the changes of blood metabolites concentrations in Holstein cows wereinvestigated. The results showed that weeks of lactation affected blood concentrations of glucose (GLU),non-esterified fatty acid (NEFA) and β-hydroxybutyrate (B-HB) significantly (P <0.01), except oftriacylglycerol (TG)(P>0.05). For blood collecting location, concentrations of TG and NEFA in thejugular vein are significantly higher than in the tail head. Compared with Dijkstra model and Gompertzmodel, Wood model are more suitable for fitting the concentrations curves of blood GLU, NEFA andB-HB, varying with weeks of lactation.The third trial was to investigate the effects of seasonal change and parity on milk yield (MY),milk composition and related indexes. Data analysis showed that MY, milk composition and relatedindexes were significantly affected by both month and parity (P <0.05). High temperature seasonsignificantly affected the production, components, sanitary state of milk. Wood model was appropriatefor a quantitative description of seasonal variation in milk yield and milk composition.