Quantification by simulation of the effect of herd management practices and cow fertility on the reproductive and economic performance of Holstein dairy herds

摘要

The performance of dairy herds is affected mainlyby factors related to cows’ characteristics and herdmanagement practices. However, these factors areinterrelated, and as such, the estimation of their individualeffect on the performance of dairy herds remainsdifficult. The aim of this study was to estimate theweight of these factors as well the interactions betweenthem on the reproductive and economic performance ofdairy farms. A stochastic dynamic model was used tosimulate most physiological and management processesoccurring on a dairy farm. A herd of 60 Holstein cows,with a milk yield of 8,000 L/cow-year, representative ofFrench Holstein dairy herds, was simulated. A total of216 scenarios were run by combining 2 levels of postpartumcyclicity resumption (average: 45 d, high: 75 d),3 levels of 21-d conception rate of the herd (i.e., proportionof cows pregnant 21 d after insemination; low:25%, average: 45%, high: 70%), 3 levels of probabilityof pregnancy loss until 120 d (low: 3%, average: 15%,high: 43%), 3 levels of sensitivity of estrus detectionby the farmer (low: 20%, average: 50%, high: 90%), 2alternative managerial goals (constant number of cowsor constant volume of milk sold), and 2 types of managementfor the sale and purchase of animals (closed oropen herd). The effect of each factor was estimated bysensitivity analysis. The parameter that had the greatesteffect on reproductive performance was the sensitivityof estrus detection: a 10-percentage-point increasebetween the low and average levels and between theaverage and high levels reduced the calving interval by16 and 5.7 d, respectively. However, the factor that hadthe greatest effect on economic performance was the21-d conception rate: a 10-percentage-point increasebetween the low and average levels and between theaverage and high levels increased the gross margin by€62.2 and €22.3/cow-year, respectively. The pregnancyloss until 120 d had an effect on economic performance:an increase of 1 percentage point of this parameterdecreased the gross margin by €2/cow-year. The otherfactors studied, and their interactions, did not have amajor effect (low value of sensitivity indices). Closedherds or farms with a constant number of cows hadeconomic losses of €58/cow-year compared with openherds or to farms with constant volume of milk sold.Altogether, our data suggest that, in a typical Frenchdairy farm, farmers’ efforts on estrus detection will bemore profitable when associated with improvement ofthe conception rate of the cows.