The chemical composition and energy of glycerin (SPGV and SPGM) obtained in the digestibility experiment were used to formulate the diet.
So that the economic feasibility for SPGV and SPGM inclusion in the feeding of piglets could be evaluated, prices of raw materials in the market were retrieved and feed costs per kilogram of body weight gain were calculated, according to Bellaver et al.
Analysis of variance was applied to results of the different variables, according to the following statistical model: [Y.sub.ijk] = [mu] + [B.sub.i] + [N.sub.j] + [F.sub.k] + N[F.sub.jk] + [e.sub.ijkl], where [Y.sub.ijk] = observation of animal l, within the block i, inclusion level j and type of semipurified glycerin k; [mu] = constant associated to all observations; [B.sub.i] = block effect, being i = 1, 2, 3, 4 and 5; [N.sub.j] = effect of semipurified levels of glycerin, in which j = 0, 3, 6, 9 and 12%; [F.sub.k] = effect of semipurified glycerin type, in which k = SPGV and SPGM; N[F.sub.jk] = interaction effect of inclusion level j and type of semipurified glycerin k and [e.sub.ijkl] = random error associated with observation.
Dunnett test was applied to compare the results of control diet with each inclusion level of SPGV and SPGM (SAMPAIO, 1998).
Rates for physical, chemical and energy composition and for SPGV and SPGM glycerin (Table 1) were lower than those by Berenchtein et al.
The linear relationship between metabolizable energy (kcal [kg.sup.-1]) associated with the use of glycerin vs semipurified glycerin (kg) (Figure 1) showed that SPGV and SPGM had ME equivalent to 3,373 and 2,932 Kcal [kg.sup.-1], respectively.
Total fatty acids levels in SPGV were higher than those in SPGM, which provided higher energy value than SPGV (3,373 kcal ME [kg.sup.-1]), or rather, 15% above SPGM (2,932 kcal ME [kg.sup.-1]).
The ratio MS: ED for both glycerin (SPGV and SPGM) was similar to that obtained by Lammers et al.
With regard to performance, there was no interaction (p > 0.05) between inclusion levels and types of semipurified glycerin (SPGV and SPGM) for any variable studied (Table 4).