Modelling the long-term consequences of implementing hormone-free reproductive management on the sustainability of a dairy sheep farm

Abstract

Livestock production systems are strongly influenced by societal constraints which induce changes in their overall chain value organization. In dairy sheep farming, practices such as the male effect (ME) supported by new precision tools (heat detector) can be used to stop the use of hormonal treatments (HT) for heat induction and synchronization. However, the effectiveness of these “hormone-free” (HF) methods for managing ewes’ reproduction remains more uncertain than that of HT. Thus, introduction of HF practices in farms currently managed with HT could imply collateral impacts on the overall functioning of the production system and affect its long-term sustainability. In this work, a new multi-agent model (called REPRIN'OV) was designed to simulate consequences of introducing a HF reproduction management on a series of biotechnical, economic and environmental farm performance indicators, including farmer workload. Three reproduction management scenarios were simulated over five consecutive years for the case study of a French dairy sheep farm considered as conventional (i.e. using HT for reproduction management). They were defined as: use of HTs and insemination (HAI); no use of HTs while preserving insemination practice (HFAI); no use of HTs and direct mating only (i.e., no insemination; HFM). Results confirm that implementing HF reproductive management without accompanying it with further changes in farm management, could negatively impact several indicators of the farm sustainability in the medium and long-term. Indeed, the HF scenarios resulted in overall lower farm biotechnical performances (e.g., −4% for the fertility rate; P < 0.05) due to a more variable heat induction. An increase in farmer's workload during the lambing period (+34% and +33% of h/L of milk in HFAI and HFM, respectively; P < 0.05) was also observed, mainly due to more staggered lambing periods. As for the simulated environmental indicators, they were increased, mostly due to the reduction of the total milk production in HF’s (e.g., +6% of farm methane emissions per L of milk for both HFAI and HFM; P < 0.05). Nevertheless, positive outcomes were also simulated in the HFs as ewes lambing peaks were lower than in HAI suggesting, e.g., a possibility to improve ewes and lamb surveillance during lambing. HF scenarios also led to higher gross margin (GM) per litre of milk produced because no HT was used, reducing the production costs compare to HAI. In addition, implementing insemination in HFAI improved farm milk production and quality (i.e., fat and protein content), which resulted in improved total GM compared to HFM. Still, the reduction in the total milk production in HFs was too important compared with the improvement of the GM per litre, resulting in a reduced total GM in these scenarios (-4% and −5% in HFAI and HFM, respectively; P < 0.05). Overall, simulation results showed that to warrant sustainable introduction of HF strategies (including ME), new frameworks in the organization of key operations at the farm level should be explored (e.g., extending reproduction or milking periods length) and trade-offs should be discussed, considering all involved stakeholders of the dairy sheep industry and the chain’s value requirements. The REPRIN’OV model, may provide an effective tool to simulate the collateral impacts of establishing HF reproductive management and could be used as a decision support system to accompany the ambitious transition towards a HF dairy sheep industry in Europe and beyond.