Heifers receiving no supplement had lower PUN (6.7 mg d[L.sup.-1]) than those fed CU (16.1 mg d[L.sup.-1]) or CUUP (17.2 mg d[L.sup.-1]).
Heifers receiving the CUUP supplement averaged 90 kg [ha.sup.-1] greater live weight gain than those receiving CU (Table 5).
The N fertilizer by supplement rate interaction for ADG occurred because the increase in weight gain due to supplementation (either CU or CUUP) was very large at the low N fertilizer rate and much smaller (CUUP vs.
In the current study, addition of undegradable intake protein (CUUP) increased ADG 37% over that observed for heifers receiving CU on pastures fertilized at the low N rate.
One exception was that gain per hectare of heifers supplemented with CUUP was superior to CU at low and high N fertilizer rates.
On pastures fertilized with 50 kg N [ha.sup.-1], heifer gain increased by 0.35 to 0.50 kg [d.sup.-1] when N supplements were fed, but when pastures received 150 kg N [ha.sup.-1], there was no increase in ADG for CU (compared to NONE) and the response to CUUP (relative to NONE) was 0.11 kg [d.sup.-1] Heifers receiving CUUP supplement had greater ADG than those receiving CU when fertilization rate was 50 kg N [ha.sup.-1] and tended (P = 0.275) to have greater ADG when fertilization rate was 150 kg N [ha.sup.-1].