Prediction of in vivo digestibility of pasture-based diets in dairy goats from faecal indicators
Résumé
For estimating quality and intake of pasture herbage by grazing goats, estimation of herbage digestibility
is often required. The aim of this work was to predict in vivo organic matter digestibility (OMD) of diets
based on temperate pasture forage from faecal composition (CP mainly). A series of indoor experiments
was carried out with goats fed on grass hay or with fresh herbage cut daily and given either ad libitum or in
restricted amounts, to mimic the effect of pasture herbage availability. Concentrate supplementation level
and regrowth age of the herbage were also studied in order to achieve a wide range of diets composition
and quality. Intake of each feed, and of faecal output (total collection), were measured precisely during 5
consecutive days in each experimental period. For each dataset (fresh pasture herbage only or fresh pasture
herbage + hay), there was a strong and inverse relationship between OMD and faecal crude protein (CP)
concentration. Including dietary CP concentration in the regression allowed increased accuracy of the
prediction. The proposed equations, relevant for good quality pastures, show a good continuum with
previous published equations on goats fed on much less digestible tropical, Mediterranean or Sahelian
forages.
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