Two feeding trials were conducted to quantify the effects of dietary strategies
on NH3 emissions of growing-finishing pigs. In Exp 1, nine growing pigs were fed cornsoybean
meal diets fortified with no amino acids (17.4% CP), Lys (17.0% CP), or Lys,
Met, Thr, and Trp (14.5% CP). In Exp 2, nine growing pigs were fed the Lys diet with 0,
62.5 or 125 ppm of yucca extract (Alltech®). Two gilts and one barrow were allocated to
each of three indirect calorimeters. Four 1-wk feeding periods, with new diets assigned
weekly, consisted of a 4-d dietary adjustment followed by 72 h of continuous NH3
measurement from chamber exhaust. Pigs and feed refusals were weighed, urine and
fecal samples collected, and manure pits cleaned after each period. Feed intake (FI)
and gain (ADG) were measured each period. Diets, urine, and fecal samples were
analyzed for TKN and NH3-N concentration. In Exp 1 and 2, diet had no effect on FI,
ADG, or feed efficiency (P > 0.05). In Exp 1, TKN in feces (3.97, 3.93, 3.72%; P <
0.001) and urine (1.10, 0.94, 0.93%, P = 0.04) decreased with decreasing dietary CP.
Fecal NH3-N decreased with decreasing dietary CP (0.47, 0.47, 0.42%, P = 0.01) while
urine NH3-N increased (0.10, 0.10, 0.20%, P < 0.001). Weekly NH3-N emissions were
22.25, 19.22, and 11.85 g (± 8.87 SEM; P > 0.05). The fraction of excreted TKN emitted
as NH3 during the week was 1.68, 1.52, and 0.91% (± 0.60 SEM; P >0.05). In Exp 2,
there was a significant linear response to increasing yucca content for urine NH3-N
(0.14, 0.13, 0.11%, P = 0.05). Fecal TKN (3.59% ± 0.06 SEM), fecal NH3-N (0.48% ±
0.03 SEM), urine TKN (0.94% ± 0.07 SEM), NH3-N emissions (12.02 g ± 2.81 SEM) and
the fraction of excreted TKN emitted as NH3 during the week (1.20% ± 0.24 SEM) were
not affected by diet (P>0.05). Reducing diet CP and including NH3-binding agents can
be effective in reducing N content of excretions and NH3 emissions. Less than 2% of
excreted N was volatilized as NH3 during the collection period.