M. Boval et al., EVALUATION OF FECAL INDICATORS TO PREDICT DIGESTIBILITY AND VOLUNTARYINTAKE OF DICHANTHIUM SP BY CATTLE, Annales de zootechnie, 45(2), 1996, pp. 121-134
In vivo digestibility trials involving creole bull calves were carried
out in order to evaluate the potential of faecal indicators for asses
sing organic matter digestibility (dMO) and organic matter intake (MOI
). The evaluated faecal indicators were crude protein (MATf), neutral
detergent fiber (NDR), acid detergent fiber (ADFf), residual nitrogen
in ADF (NADFf) and in vitro dry matter digestibility (DIV). A continuo
us digestibility trial lasting 53 days was conducted with Dichanthium
sp harvested from 20 to 73 days of regrowth. Six creole bull calves (2
56 +/- 32 kg) housed in metabolism cages were led ad libitum twice dai
ly. Refusals and faeces were collected and weighed every day for each
animal. Dry matter (MS), MAT, NDF, ADF, NADF content and DIV were dete
rmined by standard procedures from forage and faeces dried samples. Me
an values were calculated per week (5 days) period for each animal. MO
I was 4,88 kg/day and dMO ranged from 0.68 to 0.55. In our conditions,
the best predictor of dMO was MA Tf content. Linear quadratic and hyp
erbolic functions were of similar accuracy (rsd = 0.025). NDRf ADPf an
d NADFf were less accurate. Faecal MAT output (g/day) was the best pre
dictor of Mal (rsd = 240 g). The best accurate regressions predicting
dMO or MOI were used to estimate digestibility and intake of tethered
creole heifers grazing Dichanthium sp pastures during three trials whe
re daily body live-weight gain were different (740, 430 and 140 g). On
ly the hyperbolic model predicting dMO (dMO = 0.983 - 4.002/MATf, ETR
= 0.023) allowed estimates of MOI and energy intake consistent with th
e average daily gain and energy requirements of the grazing heifers in
all trials. This model should be preferred.