Decision support tool for replacement heifer management: a strategy comparison

The objective of this paper is to introduce and illustrate the application EkonMOD milk, the decision support tool concept for dairy farm managements. The purpose of this simple web-based application is to assist dairy farms managers to better understand the dynamics of the dairy herd structure and to improve economically sensible decision-making abilities in Slovak conditions. The application firstly helps dairy farmers to calculate the potential production and economic impact of different scenarios at the farm-level, in the terms of alternative what-if analyses comparison. Secondly, it takes into account the farm specific characteristics, unique limitations or weaknesses. The versatility of the core application offers potential use in numerous areas including optimal replacement heifer management or feeding strategies evaluation. When heifers calve at ages greater than optimum, larger inventories of heifers must be maintained in the young female bovine herd. Increasing the age at calving also increases the generation interval, delaying the introduction of genetically superior replacements in the herd. If the annual replacement rate of first lactation cow in the EkonMOD milk tool is set to 35%, and 25 % for remaining stages of lactations in a 300 head herd, a minimum of 170 heifers are needed in the pool, assuming a 4% attrition factor for stillbirths, 100 % dairy cow natality, 5 % mortality of calves. With selection of calves indicator set to 4 %, 50 % ratio of heifers born, heifer selection at 20 %, culled cows that die before disposal set to the value of 20 %, approximately 64 pregnant heifers are needed. For every one month increase in the age at calving over 24 months, the replacement inventory numbers are increasing at a rate of 4.7% in this model. This figure takes into account the inventory of heifers from birth until calving.