caa a22 4500 388061219 CHVBK 20180307125121.0 cr unu---uuuuu 161130e199802 xx s 000 0 eng 10.1017/S1357729800008936 doi S1357729800008936 pii (NATIONALLICENCE)cambridge-10.1017/S1357729800008936 The prediction of rumen fermentation characteristics in sheep given grass silage diets [Elektronische Daten] Eight change-over design experiments (each a duplicated 3 × 3 Latin square design using six rumen-fistulated wether sheep, live weight 50 to 60 kg) measured rumen fermentation patterns for 24 perennial ryegrass silages. Sheep were offered 800 g dry matter (DM) per day of each silage in two equal meals at 09.00 and 17.00 h. Samples of rumen liquor were taken on days 19 and 21 of each 21-day period, at 08.50 h and at 1·5-h intervals until 16.30 h. Rumen samples were analysed by gas chromatography; silages by high-performance liquid chromatography and by near infra-red reflectance spectroscopy (NIRS) using samples scanned after drying at 100°C (NIRSdry) or in the fresh state (NIRSwet). Mean intake of DM was 737 g/day. The range of silage composition was as follows (mean, range, s.d., g/kg DM unless specified): metabolizable energy (ME MJ/kg DM) 11·1, 8·8 to 12·6, 0·81; pH 4·0, 3·6 to 5·0, 0·34; lactic acid 86, 4 to 139, 42·6; butyric acid 4·7, 0·1 to 46·7,10·2. Rumen measurements varied substantially both diurnally and between silages. Mean diurnal rumen values for the 24 silages (mean, range, s.d.) were: pH 6·76, 6·55 to 7·09, 0·155; ammonia (mg/l) 132, 70 to 247, 47·7; total volatile fatty acids (TVFA mmol/l) 58·2, 45·8 to 72·0, 8·97; (acetate+butyrate)/propionate (ABP) 3·2, 2·2 to 4·8, 0·56. Partial least-square models were developed to predict rumen fermentation (means for six sampling times) using either the silage chemical composition (CHEM g/kg DM unless specified: DM, ME (MJ/kg DM), crude protein (CP), ammonia (NH3, g N per kg total N), neutralizingvalue (meq per kg DM), sugar, lactic, formic, acetic, propionic and butyric acids and ethanol) or silage NIRSdry or NIRSwet. Prediction performance was assessed comparing values for R2, standard error of cross validation (SECV) and SD/SECV (s.d. of reference population! SECV) obtained by the ‘leave one out' cross validation method. NIRSwet gave slightly better prediction accuracy overall than NIRSdry but both were superior to prediction from chemical composition. Values for R2, SECV and SD/SECV for pH were 0·23, 0·14, 1·09; 0·76, 0·08, 2·01 and 0·72, 0·08, 1·89 for CHEM, NIRSdry and NIRSwet respectively. Corresponding values for rumen ammonia (mg/l) were 0·48, 35·2, 1·35; 0·69, 27·1, 1·76 and 0·70, 26·3, 1·81; for TVFA 0·52, 6·73, 1·33; 0·80, 4·06, 2·21 and 0·93, 2·47, 3·63; for rumen ABP ratio 0·69, 0·32, 1·78; 0·76, 0·30,1·88; 0·72, 0·30,1·85. The silage predictors with greatest influence in the CHEM model for rumen ABP ratio were sugar, CP and lactic acid (negative) and butyrate and ethanol (positive). NIRS shows considerable promise as a means of predicting rumen fermentation of animals given grass silage diets. Copyright © British Society of Animal Science 1998 grass silage nationallicence near infra-red reflectance spectroscopy nationallicence rumen fermentation nationallicence sheep nationallicence Offer N. W. Grassland and Ruminant Science Department, Scottish Agricultural College, Auchincruive, Ayr KA6 5HW Percival D. S. Grassland and Ruminant Science Department, Scottish Agricultural College, Auchincruive, Ayr KA6 5HW Animal Science Cambridge University Press 66/1(1998-02), 163-173 1357-7298 66:1<163 1998 66 ASC https://doi.org/10.1017/S1357729800008936 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S1357729800008936 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Offer N. W. Grassland and Ruminant Science Department, Scottish Agricultural College, Auchincruive, Ayr KA6 5HW NATIONALLICENCE 700 1- Percival D. S. Grassland and Ruminant Science Department, Scottish Agricultural College, Auchincruive, Ayr KA6 5HW NATIONALLICENCE 773 0- Animal Science Cambridge University Press 66/1(1998-02), 163-173 1357-7298 66:1<163 1998 66 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge