In-herd diversity of lifetime performances: a key for the sustainability of livestock farming system based on grassland
Résumé
Sustainability of livestock farming systems (LFS) based on grassland depends on their abilities to buffer environmental variations while maintaining targeted production project. These abilities come from the regulating properties of LFS. On one side, regulations can arise from adaptive grazing management in order to take advantage of resource diversity under climatic hazard (Andrieu et al., 2007). On the other side, regulations can also arise from female adaptive abilities driven by farmer practices. At the herd level, variable female responses generate a diversity of lifetime performances. The objective of this study was to assess the contribution of lifetime performance diversity to the sustainability of LFS based on grassland. We relied on the example of dairy goat herd. Total milk production in year 1 was similar for both cases (Case 1: 120 601 kg; Case 2: 119 016 kg). The decline in fertility led to a decrease of production in both cases. However, in case 1 this decline was around 17% of herd production in year 1 and around 8% in case 2. In case 2, the perturbation due to low fertility was buffered at herd level due to an increase in the number of females maintained in extended lactation. These females contributed to 14% and 24% of overall production in years 1 and 2 respectively. Both management cases illustrate that herd can have regulating properties arising from the diversity of female lifetime performances. This aspect can be of great interest for grassland systems where feed supply is highly variable and female regulating properties are strongly solicited.