Peppermint (Mentha piperita Huds.) and basil (Ocimum basilicum L.) etheric-oil by-products as roughages for sheep feeding

Abstract

Whole plants of peppermint and basil after etheric oil distillation were tested for in situ degradability (in the rumen of sheep) and in vitro gas production. Digestibility of these byproducts was also determined in in vivo trials with 9 wethers in a 3 × 3 Latin square design. Three diets were tested: 900 g DM meadow hay (diet H), 450 g DM meadow hay plus 450 g DM peppermint (diet P), and 450 g DM meadow hay plus 450 g DM basil (diet B). Peppermint, after etheric oil distillation, contained more CP (130 vs. 72 g/kg DM), and less NDF (583 vs. 828 g/kg DM) and ADF (425 vs. 680 g/kg DM) than basil. High acid detergent insoluble nitrogen concentration was obtained in peppermint and basil (19.7 and 23.4% of total N, respectively) which resulted in low rumen CP degradability (42 and 36%, respectively). Results of in vitro gas production indicated less extensive and slower fermentation of basil than peppermint. Organic matter digestibility (OMD) of basil was 0.51, while OMD of peppermint (0.54) was slightly less than that of meadow hay (0.56). No differences between the treatments were found in pH, ammonia and volatile fatty acid concentrations of rumen liquor sampled 3 h after the morning meal. Feeding diet B led to the highest proportion (75%) of acetic acid in the rumen liquor which corresponded to the highest intake of structural carbohydrates (NDF: 683 g/day and ADF: 504 g/day) when the diet contained basil. The lowest total protozoal number was in rumen liquor of sheep fed diet B: 151 × 10³ vs. 195-197 × 10³/ml for diets H and P.