Effect of feed and manure management on nitrogen footprints of commercial dairy farms: A survey study of Central Punjab

Abstract

Dairy farming is vital for global food security and economic stability. However, inefficient nitrogen (N) utilization in dairy farms contributes to ammonia volatilization, nitrate leaching, and greenhouse gas emissions, posing serious environmental challenges. Although developed countries have made substantial investment in nitrogen management, many developing regions of the world, including Pakistan, are still using high-protein feed coupled with manure management practices with substantial nitrogen losses and overall low nitrogen use efficiency (NUE). Nitrogen sources, utilization, and excretion in Punjab commercial dairy farms are subject to strong influences from both the feed composition and the manure management employed in these systems. Farm surveys were complemented by direct observations on the 15 commercial dairy farms using a mixed-methods approach and feed and manure samples were collected for analysis. Pearson’s correlation and regression model were used to assess relationships between nitrogen intake, excretion, and manure retention. Results revealed a bimodal herd size distribution, with most farms operating within 175–225 animals. A strong correlation (r = 0.87) was observed between dry matter intake (DMI) and manure generation. Lactating cows had the highest DMI (23.5 kg day-1) with efficient nitrogen utilization, while calves exhibited the lowest nitrogen efficiency. Flush Systems had the highest nitrogen losses (3.8–5.5 g kg-1, p < 0.05) due to higher ammonia volatilization and nitrogen runoff, whereas slatted floor and drylot systems retained the most nitrogen (>12 g kg-1) by minimizing surface exposure and volatilization. These findings emphasize the urgent need for precision feeding, improved manure management, and policy-driven interventions.