Economic impact of calving interval on dairy cattle herds

The aim of this study was to quantify and evaluate the economic impact of calving interval on dairy herd. A simulation using a Dimensioning and Evolution of Bovine Herd software was conducted on three dairy herds from a hypothetical production system composed by 25 females of Holstein breed, having an average of 15 kg daily milk production, at an age of 30 months after the first calving, kept in a 200 ha Brachiaria decumbens Stapf. pasture presenting an 1AU/ha/year support capacity. The equivalence among the tested animal categories were: dam cows 1.30; females of 0-1 year 0.30; females of 1-2 years 0.71; females of 2-3 years 1.01n AU/ha. The three herds showed the same culling rates (20%) and mortality rates (3% for 0 to 1 year; 2% for 1 to 2 years and 1% for 2 to 3 years), only the birth rates differed, namely 100; 80 and 60% for the cases 1; 2 and 3, respectively as reflecting in calving intervals of 365, 510 and 657 days. The simulation of the economic impact was done by the MS Excel(r) applicative. Calving interval not only directly affected the herd composition and evolution but also influenced dairy business profitability, the most efficient birth rate was that of 100%, in other words, calving interval of 12 months.