Digestibility and voluntary intake of vine leaves (Vitis vinifera L.) by sheep

Twelve castrated adult male (62+/-3 kg body weight) Manchego sheep were used in a digestion trial. Diets consisted of vine leaves or vetch-oat hay alone, and vetch-oat hay and vine leaves in a ratio of 1:1, Voluntary intake of vine by-products by eight females Manchego sheep was also measured. The CP level was greater in vetch-oat hay (73 g kg(-1) DM) than vine leaves (68 g kg(-1) DM) and the vine leaves had a higher level of neutral-detergent insoluble crude protein (NDF-CP, 38 g kg(-1) DM) than vetch-oat hay (17 g kg(-1) DM). NDF was less in vine leaves (319 g kg(-1) DM) than in vetch-oat hay (566 g kg(-1) DM). However, the lignin content of cell walls in vine leaves (146 g kg(-1) NDF) was higher than hay (127 g kg(-1) NDF), The content of condensed tannins of the vine leaves (50 g kg(-1) DM) was 10 times higher than that of the vetch-oat hay. DMD and OMD of vine leaves was 42.2 and 47.2%, respectively. Apparent digestibility of CP in vine leaves was negative (-25.8%) and was lower (P<0.001) than CP digestibility of vetch-oat hay (48.9%). Digestibilities of NDF and ADF of vine leaves were 3.8 and -0.6%, respectively. These values were lower (P<0.001) than those obtained for vetch-oat hay (53.9 and 54.7%, respectively), DM and DOM intake of vine leaves was 1010.7 and 415.3 g per day, respectively. With the exception of urea, there were no differences (P>0.05) between sheep fed leaves and those fed vetch-oat hay in measured plasma metabolites. These results suggest that the low digestibility of the vine leaves is due to several factors, such as the high level of condensed tannin content and low protein digestibility. (C) 2000 Elsevier Science B.V. All rights reserved.