However, methodology in the above-mentioned assays with horses for FDNi and FDAi has always been in vitro, with the rumen liquid as inoculum.
Current analysis studies the viability of the internal indigestible markers FDNi and FDAi obtained by in situ techniques in bovines and in vivo techniques in horses by MNG so that apparent nutrient digestibility in horses fed on hay and on hay+corn could be predicted and compared to the total feces collection method.
The five treatments consisted of digestibility evaluation methodologies constituted by the direct method through total feces collection and by the indirect method through internal indigestible markers FDNi and FDAi obtained by in situ techniques in bovines and by in vivo techniques in horses with MNG.
Digestion residues underwent extraction by neutral and acid detergents, with the formation of FDNi and FDAi.
Nutrients' digestibility coefficients from direct and indirect methods by FDNi and FDAi with in situ and in vivo techniques from digestion assays, were processed by variance analysis Statistical Analysis System (SAS, 2000), following the model: Yij = [mu], + [B.sub.i] + Tj + Eij; in which Yij = fecal production and apparent digestibility coefficient of nutrients of horse i fed on treatments j; [mu], = general constant; [B.sub.i] = effect of horse i, in which i = 1,2,3,4; Tj = effect of treatment j, in which j = 1,2,3,4,5; Eij = randomized error associated with each observation Yij.
Table 2 shows concentration, intake and recuperation rate of markers FDNi and FDAi obtained from in situ and in vivo coast-cross hay.
Markers' rates in current assay varied between 23 to 32% for FDNi, very similar to that reported in the literature for forage between 31 and 33% (BERCHIELLI et al., 2005; LIPPKE et al., 1986), whereas FDAi with rates between 14 and 19% was lower than that reported by Berchielli et al.