Diurnal pattern of excretion in grazing cattle

Redistribution of nutrients by large herbivores in grazing systems depends largely on the diurnal pattern of excretion by the animals. This study investigated diurnal pattern of excretion in cattle in two grazing systems; an intensive system where heifers and steers grazed a sown grass pasture during the daytime with supplementation in a barn at night, and an extensive system where heifers and cows continuously grazed native plants as an understory of a young tree plantation in a mountainous area. The daily defecation and urination frequencies per animal ranged from 6-24 and from 2-16 times, respectively, producing mean values of 12.0-17.7 and 5.9-9.3 times for 8 cases based on the sites, seasons and animal groups. The diurnal distribution of excretion was always non-uniform in all excretion variables measured, i.e. frequencies of defecation and urination, fecal output and fecal output per defecation. The defecation and urination frequencies and fecal output tended to be high during the day and low at night, and the reverse occurred for the fecal output per defecation. The animals defecated and urinated more frequently and produced greater amounts of feces when they spent more time grazing and moving and less time resting and ruminating. On the contrary, the fecal output per defecation was greater when the animals were engaged longer in resting and ruminating and shorter in grazing and moving. Regression analysis suggested that the use of defecation frequency as a substitution for fecal output may underestimate fecal nutrient deposition and accumulation for an area where animals spend < 23 min grazing per hour, while the substitution may overestimate fecal nutrient deposition and underestimate nutrient depletion for an area where animals spend > 23 min grazing per hour.