Prediction of in vivo digestibility of pasture-based diets in dairy goats from faecal indicators

For estimating quality and intake of pasture herbage by grazing goats, estimation of herbage digestibilityis often required. The aim of this work was to predict in vivo organic matter digestibility (OMD) of dietsbased on temperate pasture forage from faecal composition (CP mainly). A series of indoor experimentswas carried out with goats fed on grass hay or with fresh herbage cut daily and given either ad libitum or inrestricted amounts, to mimic the effect of pasture herbage availability. Concentrate supplementation leveland regrowth age of the herbage were also studied in order to achieve a wide range of diets compositionand quality. Intake of each feed, and of faecal output (total collection), were measured precisely during 5consecutive days in each experimental period. For each dataset (fresh pasture herbage only or fresh pastureherbage + 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 theprediction. The proposed equations, relevant for good quality pastures, show a good continuum withprevious published equations on goats fed on much less digestible tropical, Mediterranean or Sahelianforages.