Impact of summer cooling management on milk water footprint in dairy cows

Abstract

The Water footprint (WF) is an indicator of the amount of direct and indirect freshwater used to make a product available, measured over its entire supply chain. Dairy cows are cooled using sprinklers and fans to mitigate heat stress (HS) in summer. Although several studies have already evaluated cows’ milk WF, little information is available on the impact of water sprayed to cool cows on milk WF and fans related energy consumption. The study enrolled six Holstein-Friesian farms equipped with cooling systems, including sprinklers and fans. Based on the volume of water sprayed to cool cows, farms were classified as Low User Spraying Water (Low-USW) and Large-User Spraying Water (Large- USW). For each farm, an alternative no-cooling scenario was modelled considering the water and energy saved, the increment of the drinking water needed from no-cooled cows, and the reduction of milk yield caused by HS. The mean annual WF of the farms involved in the study accounted for 805 ± 225 L water per kg of Fat and Protein Corrected Milk (FPCM) with the following distribution among the green, blue and grey fractions: 67.9%, 21.1%, and 11%, respectively. Cooling operations had a low incidence (0.04%) on the overall milk WF, which was 1.1% lower (8.6 L water kg−1 FPCM−1) than that modelled for the alternative no-cooling scenarios. Although both investigated cooling protocols (Large vs Low) showed a similar capacity to contain milk losses during summer, the study has highlighted differences in their resource use. Compared to the Large-USW, the Low-USW cooling management reduces water use by about 0.4 L water kg−1 FPCM−1 and increases energy consumption by about 0.13 kWh kg−1 FPCM−1. Cooling systems help farmers to mitigate HS in dairy cows during summer. The extra water needed for cooling is compensated by the effects of cooling in limiting the HS-related decline in milk yield. Therefore, the water used to cool cattle does not impact milk's WF. However, further research is needed to find the best solution for sprinklers and fans utilization, optimizing the preservation of animal welfare and environmental sustainability of milk production under climate change scenarios.