Effectiveness of precision feeding in reducing N excretion in dairy cattle

Two periods enrolling 56 (milk yield 36.2 ± 7.91 kg/d) and 58 32.4 4.99 grouped-fed dairy cows were performed to evaluate nutrient adjustment N emissions of a precision feeding strategy. Pens blocked by parity randomly assigned conventional (CONV) or scheme (PREC) for 21-d period. The CONV group was offered total mixed ration (TMR, 6.82 6.65 MJ NEl/kg DM, in period 1 2, respectively, 165 g CP/kg DM both periods; whereas PREC fed partial (PMR, 6.40 135 137 respectively) concentrate feed supplemented twice daily the milking parlour, which contained different quantities soybean meal, corn wheat middling’s according estimated nutritional needs each cow above those supplied consumption PMR. Individual nutrients consumed from PMR calculated using 10-d rolling average performance data concentration its components, BW recorded periods). A balance urine fecal spot sampling during last 3 d study 1, stored manure gaseous (ammonia, methane, nitrous oxide, carbon dioxide) measured 2 wk 2. After adaptation diet, 82 homogeneously distributed 4 DIM categories: early (< 81), mid-early (81 150), mid-late (151 220), late (> 220) used assess how energy protein requirements adjusted system. Dairy systems energetically overfed, tended be more CP overfed than cows. Total excretion, milk urea greater There no differences ammonia oxide storage between cows; however, methane dioxide increased 55 15%, respectively Precision system based on preceding composition can reduce excretion without affecting short-term but increasing C manure.