Milk sustainability in specialized farms as affected by farm size and culling rates: A new perspective for allocation.

Several studies investigated the sustainability of dairy cattle systems. Global warming potential (GWP) is a "touchstone impact category" of LCA, whereas fossil depletion (FD) remains a scarcely studied environmental indicator. This study aims to help fill the gap of knowledge on FD in dairy cattle systems. We compared two highly specialized dairy cattle farms equipped with precision technologies: a large (L) and a small (S) farm. The discriminants were the number of lactating cows and the agricultural area, with L having approximately twice the heads and three times the area of S. In LCA we used the main product (FPCM, i.e., 1 kg of milk normalized for fat and protein), as the functional unit (FU). A second FU was used, i.e., hectare of occupied area. By changing the FU, the study showed different results, because S performed better when FPCM was used while L performed better when the agricultural area was used. Allocation of culled cows affected the environmental impacts of both farms improving their sustainability. A high culling rate provides information on herd management, and it can result in lost income. We proposed the allocation as helpful to quantify the culled cows, a potentially undesirable product, showing a significant difference between farms, i.e., 30 and 38 % of culling rate in the L S, respectively. In S, this rate led to a higher income percentage provided by culled cows (6.3 vs. 4.2 % of L). Allocation decreased the equivalents of some LCA environmental indicators, showing an oversized replacement of cows.