Assessing fresh urine puddle chemistry in commercial dairy cow houses

Ammonia emission mainly originates from urea in urine puddles on floors in dairy cow houses. This emission process can be modelled. However, required model inputs have not been updated recently. In addition, values for the model variables pH, Urinary Urea Nitrogen concentration (UUN), and their relation with farm and feed management are unknown for commercial dairy cow houses. Moreover, their effect on ammonia emission is unknown. Therefore, the objective of this paper was to investigate the pH and UUN in livestock practice. Sixteen commercial farms were measured in a factorial design of four Floor-Management types (FMTypes). Each farm was measured in two seasons and a Diet factor was defined, based on the amount of grass in total roughage. Overall mean values were 4.27 kg m-3 for UUN, an initial pH of 8.3, both in fresh puddles, and a pH(ξ) of 9.0 for random puddles at a random time. For UUN both the variation within and between farms was large, whereas the variation for pH was small. The Diet was the only factor that resulted in a significant effect, with a 0.1 difference in pH(ξ). Compared to the reference values, both the mean UUN and pH showed smaller values. The calculated potential ammonia in kg puddle-1, however, showed a huge range and was considerably larger than the commonly used reference values in the Netherlands