Comparative study of feeding and rumination behaviour of goats and sheep fed mixed grass hay of different chop length.

Rumination is reported to be more pronounced in sheep compared to goats. This study compared the feeding and rumination behaviour of small ruminants and consisted of two experiments (E1 and E2). In E1, four sheep and four goats were offered low-quality hay (NDFom: 692 g/kg dry matter [DM]), processed to two chop lengths (long hay [LH]: 35 mm; short hay [SH]: 7 mm) in a 2 × 2 factorial (2 species × 2 chop lengths), cross-over design. In E2, the same animals were offered moderate-quality hay (NDFom: 636 g/kg DM) processed as LH and SH. Hay was offered for ad libitum consumption. Feeding and rumination behaviour was evaluated using video recordings. Aspects of rumination like chewing frequency were evaluated for 30 min per day. Faecal samples were analysed for faecal-N and particle size. There was no species effect on feed intake and organic matter digestibility (faecal N as proxy); however, goats consumed more LH than SH in E1 and E2. There was an effect of species on rumination:eating duration (R:E) ratio (higher in sheep) in E1 but not in E2, where there was a tendency for a species effect on rumination duration. In E1 and E2, sheep had a higher R:E ratio for SH than for LH. For rumination behaviour, there was a species effect for number of daily boli, chewing frequency and chews per day (more in sheep) in E1 and E2. No effect of species was found for faecal particle size. Despite much concordance, feed comminution behaviour differed in some aspects between sheep and goats. In an evolutionary context, a shift of significance of rumination could be triggered by a higher amount of abrasives in natural diets of sheep, rendering a shift of chewing towards ruminally prewashed material a rewarding strategy.