Farrell, Lydia Jane2016-01-142016-01-142015https://hdl.handle.net/10182/6783Prediction of nitrogen (N) leaching from urine events using modelling tools such as OVERSEER is important for regulation of dairy farm outputs and practices. Risk of N leaching is greatest during winter, particularly in systems which adopt high stocking densities such as those grazing fodder beet and kale crops. However large prediction errors for leaching values from OVERSEER are recognised, highlighting the need for more quantitative information on urination behaviour of dairy cows grazing winter forages. The study was conducted at Ashley Dene research farm (-43.65 º North, 172.33 º East) using 24 high producing Friesian x Jersey dairy cows fed two diets representative of industry practice. Diet treatments were 10 kg DM of fodder beet with 5.6 kg DM of ryegrass baleage (FB) or 16.4 kg DM of kale with 6.4kg of oat straw (KA) . All cows were fitted with a urine harness for 24 to 48 hours which collected data on number, volume, and timing of urine events. Urine patch areas were estimated using the urine harness data and a calibration curve of urine volume and wetted area in the paddocks being grazed. Urine volumes were similar (27.6 L/cow/day, p=0.988) though behaviour was affected by diet whereby FB cows urinated less frequently (8.42 vs 10.1 events/cow/day for FB and KA respectively, p=0.128) but with more volume per event than KA (3.58 vs 2.71 L/cow/day for FB and KA respectively, p=0.04). On their own, similarity in total volumes (FB vs. KA) could not be explained by intake of water (55 vs. 69 L/cow/day, p<0.001), N (237 vs. 472 g N/cow/day, p<0.001), DM (13.4 vs. 17.1 kg cow/day, p<0.001), potassium (2.7 vs. 2.9 g/cow/day, p=0.055) or sodium (0.53 vs. 0.40 g/cow/day, p<0.001). The urine patch areas on the FB grazing area were smaller at 0.16m² than the kale patches at 0.23m² which is attributed to differences in paddock surface microtopography. The smaller, more dense deposits of N in urine patches and the stocking rate being three times as great resulted in a higher predicted volume of N leached from the fodder beet paddock at 123 kg/ha compared with 82 kg/ha for the kale paddock. The results of this study provide new information regarding the urination behaviour of the livestock and the N losses from winter grazing in New Zealand systems. There is a need for more confidence in the measurement techniques used for future studies.enCanterburyBrassica oleraceaBeta vulgarisurine depositionsurine paddock coveragedry dairy cowsurine patchesdairy cowsurine nitrogenDissertationANZSRC::070304 Crop and Pasture Biomass and BioproductsANZSRC::070105 Agricultural Systems Analysis and ModellingANZSRC::070204 Animal NutritionQ111964971