Impact of farming systems and welfare indicators on enteric methane emissions calculated from infrared-predicted milk fatty acids in Parmigiano Reggiano Consortium farms

Enteric methane emissions (EME) are the main source of anthropogenic GHG in the dairy industry. Certified food products, such as Parmigiano Reggiano cheese, are particularly interested in monitoring their environmental impact. To achieve this, a rapid, cost-effective method, applicable at the population level, is to estimate EME from predicted milk fatty acids obtained by milk mid-infrared spectroscopy. The aim of this study was to evaluate the variation in EME-derived traits according to dairy system and farm-level animal welfare indicators in farms belonging to the Parmigiano Reggiano Consortium. The final dataset used for the analysis integrated milk test-day records, mid-infrared spectra, and farm animal welfare assessment data, resulting in 1,256,135 records from 174,180 cows on 940 multibreed dairy farms. Dairy systems were identified by clustering farms according to their common characteristics and practices. These included 2 traditional systems (one from the Apennine region and the other prevalent in the Po Plain) and 2 modern systems (both prevalent in the Po Plain, one with and the other without the use of TMR). This study analyzed different EME phenotypes, including methane emissions per day, emissions relative to kilograms of DMI, and emissions per unit of production (corrected milk, fresh cheese, and cheese solids). The effect of animal welfare and dairy systems on individual methane emissions was evaluated using mixed models. Three groups of farm-level welfare indicators were considered: management practices, housing structure and equipment, and animal-based measures. These indicators are part of the national animal welfare evaluation conducted by the Italian National Reference Center for Animal Welfare (CReNBA, Brescia, Italy). The results showed that the dairy system and the interaction between dairy system and breed affected all traits. The general trend was that modern dairy systems produced more grams of methane per day than traditional systems, but their emissions per unit of production were lower. Breed-related EME variations across dairy systems were especially notable in Reggiana cattle. The overall effect of the animal welfare on EME traits was minor compared with the dairy system or breed effects. Across the 5 EME traits analyzed, only 2 showed significant associations with management (methane expressed in g/d and relative to kg of DMI) and one with animal-based measures (methane production in g/d), whereas no effects were observed for structure and equipment. In light of these findings, producers of high-quality foodstuffs, such as Parmigiano Reggiano cheese, may take into account the impact of different sources of variation in EME in the process of selecting a suitable production system. The results of this study could be helpful in improving farm-level management, as well as in the development and implementation of breeding programs aimed at reducing the environmental impact of dairy farming.