Browsing IJAFR, volume 43, 2004 by Subject "Nitrogen"
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Effect of autumn/spring nitrogen application date and level on dry matter production and nitrogen efficiency in perennial ryegrass swardsThe influence of autumn/spring N-application date and level on grass dry matter (DM) production in spring and on N uptake, recovery and efficiency were examined over 3 years (1998, 1999 and 2000, identified as Year 1, 2 and 3, respectively). Seven N-application dates were investigated in years 2 and 3 while four application dates were investigated in Year 1. The application dates were 21 October (T1), 11 November (T2), 2 December (T3), 23 December (T4), 12 January (T5), 3 February (T6) and 23 February (T7). Three N-application rates (kg N/ha) were used: 30 (N30), 60 (N60) and 90 (N90) plus a zero-N control (N0). Herbage DM yields were determined on: 18 March (H1) and 8 April (H2). Two herbage masses (HM) (40 mm above ground level) at initial Napplication date were investigated: a high HM (HHM) of 500 kg DM/ha and a low HM (LHM) of 100 kg DM/ha. The HM at initial N-application date in Year 1 was HHM, in Year 2 LHM and in Year 3 both HHM and LHM. There was a significant effect of Year (P<0.001), HM (P<0.001), N-application date (P<0.001) and N level (P<0.001) on DM production at both H1 and H2. At H1 there was a significant interaction between N-application date and level for DM production. N-application date had a significant (P<0.001) effect on N recovery at both H1 and H2. The highest N recovery rate at the two harvest dates was at T5, while the lowest was at T1 and T2. At H1 and H2 there was a significant effect (P<0.001) of application date on response to applied N. The responses were 7.5, 8.0, 8.3, 12.0, 15.7, 7.3 and 5.6 (kg DM/kg N) (s.e. 1.88) for T1 to T7,respectively, at H1, while the corresponding values at H2 were 10.3, 8.7, 6.1, 15.2, 17.6,11.4 and 15.1 (s.e. 1.88). At H2 the response to applied N was 15.6, 11.5 and 9.1 (kg DM/kg N) for N30, N60 and N90, respectively (P<0.05). Regression analysis indicated that highest DM production was achieved with T5 for both H1 and H2 harvest dates, while the lowest responses were associated with T1, T2 and T3 application dates.
The effect of dietary crude protein concentration on growth performance, carcass composition and nitrogen excretion in entire grower-finisher pigsTwo experiments, a performance experiment (n = 72) and a nitrogen balance (n = 16) experiment were conducted to evaluate the effects of dietary crude protein (CP) concentration on growth performance, carcass characteristics and nitrogen excretion of pigs. Dietary CP concentrations in experimental diets (g/kg) were 207.5, 170, 150 and 122.5 for treatments 1, 2, 3 and 4, respectively, and were offered to individually-fed entire-male grower-finisher pigs (45 to 95 kg). The diets were formulated to contain 13.7 MJ digestible energy and 11 g total lysine/per kg. Synthetic lysine, methionine, threonine and tryptophan were added to achieve ideal protein status. There was a linear increase in food intake as CP concentration decreased (P < 0.05). There was a quadratic response in daily live-weight gain and food conversion ratio (P < 0.05) to the change in CP concentration (P < 0.05), with an improvement in daily gain and food conversion ratio occurring as CP concentration declined to 150 g/kg and a deterioration in these parameters thereafter. There was a linear decrease (P < 0.05) in lean meat proportion as CP concentration decreased. There was a linear decrease in urinary output (P < 0.05), urinary pH (P < 0.01) and slurry pH (P < 0.05) as dietary CP concentration decreased. There was a quadratic response in urinary nitrogen output (P < 0.05), total nitrogen output (P < 0.05) and N utilization as dietary CP decreased. In conclusion, a dietary CP level of 150 g/kg was optimal in terms of growth performance and reduced nitrogen excretion.