Evidence has been provided for important morphophysiological variations of the digestive system of the different species of ruminants (Hofmann, 1989). These variations are a consequence of the ecophysiologycal adaptation and diversification of ruminants, and are related to feeding behaviour and digestive physiology. Ruminants of different feeding types have gained ecological advantage, which determines that some species are better adapted than others for each specific situation. Some recent studies have shown that important variations may also occur between breeds within each ruminant specie (Carro et al., 1993; Silanikove et al., 1993). The present work was conducted to study differences between Churra (CHR) and Merino (MER) sheep in digestibility and rumen degradation characteristics of fresh herbage harvested at different maturity stages.

The experiment comprised two digestion trials. Each trial was conducted with twelve mature CHR sheep (mean live-weight (LW)= 48 kg (SE 1.8)) and twelve mature MER sheep (LW = 46 kg (SE 1.2)). Animals were fed on fresh herbage harvested from a sward which consisted of a mixture of grasses and clover. Herbage for the first trial was harvested in early June (early cut EC), whereas the herbage used in the second trial was cut in late July (late cut LC). After cutting, the herbage was chopped (5-10 cm) before feeding to the animals. Within each trial, animals of each breed were randomly allocated to six feeding levels (ranging from 8.1 to 24.7 g forage DM/kg LW/day).