Influence of climatic disturbances on the lactation curve in dairy goats
Résumé
In the context of climate change, intensification of temperature and humidity fluctuations are inducing unquantified impacts on animal performance. The goat is described as adapted to harsh environments, however the limits of its adaptability to climatic stress are not clearly defined. The aim of this study was to investigate the relationship between lactation dynamics and climatic disturbances. This study used the daily milk production data related to 1,174 lactations from 585 goats of the experimental goat farm of INRAE MoSAR, between 2006 and 2021. The data were fitted with the Perturbed Lactation Model, which provides a theoretical-unperturbed lactation curve and characterizes the detected perturbations in the milk production time-series. Daily temperature and hygrometry data were collected at the nearest meteorological station. To explore the impact of climatic conditions, each perturbation detected was confronted with the climate conditions at the date of the perturbation and seven days prior to it. Climatic stress, cold or hot, was estimated using three indicators: a temperature accumulation and two equations of temperature humidity index. Statistical analyses were performed to evaluate if goat lactation curve perturbations were related to climatic stress indicators or to major herd management events. The results showed that for 1,174 lactations 9,010 perturbations were detected. 5.7% of these perturbations in milk production occurred on the period of reproduction (synchronization followed by artificial insemination). The climatic environment study indicated that about 25% of the perturbations occurred during cold stress periods. These results highlight the benefit of combining mathematical models with timeseries data to explore animal responses to the environment, especially climatic stress. They would help to precise the thermal tolerance threshold of goats in temperate zones. Furthermore, they allow to unravel the relative effects of thermal fluctuations and other environmental factors that may alter goat metabolism, and therefore to better understand the conditions necessary to rear goats in an environment more respectful of their well-being.