Economic drivers of the optimal productive lifespan of dairy cows in two different Swiss milk production systems

The short lifespan of dairy cows not only raises ethical questions but is also the subject of economic debates. Determining the economically optimal productive lifespan (OPL) is a complex issue because a large share of cows is culled during the first 2 lactations. The objective of this study was to estimate the OPL, taking into account relevant influencing factors, such as milk loss risks, heifer costs, and breeding progress (BP). We developed a bioeconomic cow model for 2 production systems with different milk-yield levels (C_low = 6,194 kg/yr, C_high = 9,338 kg/yr) based on the net revenue approach. The model used accounting data from 189 family farms and herd-specific data from 9,858 cows with 10 completed lactations, as well as culling statistics from different breeds based on herdbook data. To estimate the impact of different risk scenarios on OPL, culled cows were assigned a milk loss of 10% to 50%. The theoretical OPL excluding milk loss risks was over 9 yr of productive lifespan, with marginal income declining significantly from the fourth year of production onwards. With an effective productive lifespan of 3.6 yr (C_low) or 2.9 yr (C_high), the milk loss rate expected by the farm was estimated to be around 25% if the cows remained in production for longer. Heifer costs had a significant influence on OPL: with heifer costs between $2,700 and $5,000 and considering 25% risk, OPL varied between 3 and 7 yr. For the baseline scenario for heifer costs ($3,423), the OPL was found to be between the fourth and fifth years of production. The effect of BP in milk yield on OPL was weak: Assuming 2% BP per generation reduced OPL by 6 mo, compared with the baseline assumption of identical replacement. To fully exploit income potential, it is more important to improve production reliability by reducing risk, which is particularly relevant for higher-yielding cows. This requires a stronger focus on fitness-related traits, such as fertility and health. The realistic economic potential of higher longevity was found between 10% and 15% higher income per cow, which would be achieved for C_high with an average productive lifespan of 4 years and for C_low at 6 years.