Food waste as feed in dairy systems of Greater Bengaluru, India: Assessing the impacts on production, milk safety, and enteric methane emissions

Abstract

Due to rapid urbanisation in India, many farmers have resorted to incorporating food waste (FW) into their cattle rations. However, the effect of feeding these FWs on milk yield, milk composition, fatty acid (FA) profile, the presence of heavy metals in feeds and milk, and on enteric methane emissions remains unclear. Therefore, a study was carried out with dairy farmers in the southern Indian megacity of Bengaluru. The study comprised 39 farmers who in total reared 75 cows on diets incorporating on average 23% of FW, and 164 cows fed without FW inclusion, with repeated observations of some cows across seasons. During three visits in winter 2020 - 2021 (n=74 records), monsoon 2021 (n=61), and summer 2022 (n=104), feed intake, milk yield and quality were determined on a per-cow basis. Cows receiving FW-based diets showed higher dry matter intake and milk yield compared to non-FW-fed cows. Heavy metal concentrations in FW feeds were similar to or lower than those in conventional diets, and most milk samples remained within safe limits, except for Pb, which exceeded WHO thresholds in 20% of samples from the FW group. Milk from FW-fed cows contained a higher proportion of unsaturated FA, while dry matter intake-based enteric methane emission estimations were similar between feeding groups. In conclusion, the higher milk yield and elevated levels of unsaturated FAs in milk from FW-fed cows suggest that FW can be a valuable alternative feed resource for dairy production. Although heavy metal concentrations in milk were generally low, Pb levels exceeded the safety threshold in some of the samples, which calls for close monitoring.