In a feeding experiment β-hydroxybutyrate (BHB), glucose, albumin, total protein, globulin and urea concentrations in the plasma of twin-bearing ewes were analysed. Mature Suffolk cross ewes were given either formic acid (FA)-treated grass silage or grasslmolassed sugar-beet pulp (MSBP) silage in late pregnancy. The experiment commenced on day 91 of pregnancy and the dietary treatments were FA-treated silage (Tl), FA-treated silage + soya-bean meal (SBM) (T2), MSBP silage (T3), MSBP silage + SBM (T4), FA-treated silage + MSBP (T5), FA-treated silage + MSBP + SBM (T6) or FA-treated silage + 150 g crude protein (CP) per kg concentrate (T7). SBM was given only in the last 22 days of pregnancy aiming for a total CP intake of 220 g per ewe per day. Blood samples were collected by jugular venipuncture from each ewe 3 h following consumption of the morning dietary allowance on days 121, 128, 135 and 142 of pregnancy. Daily metabolizable energy (ME) intakes of 6·8, 11·4, 9·6, 12·8, 10·5, 13·7 and 14·7 (s.e. 0·58) MJ per ewe were recorded for Tl to T7 respectively over the last 3 weeks of pregnancy. Respective CP intakes of 72, 213, 110, 225, 109, 215 and 175 (s.e. 5·64) g per ewe were recorded for Tl to T7 respectively over the last 3 weeks of pregnancy. BHB concentrations (mmol/l) on day 121 of pregnancy of 1·18, 1·25, 0·52, 0·52, 0·56, 0·39 and 0·45 (s.e. 0·17), on day 128 of pregnancy of 1·17, 0·94, 0·52, 0·51, 0·72, 0·62 and 0·39 (s.e. 0·20), on day 135 of pregnancy of 1·53, 0·68, 0·68, 0·66, 0·71, 0·62 and 0·46 (s.e. 0·20) and on day 142 of pregnancy of 1·43, 0·60, 0·62, 0·56, 0·62, 0·56 and 0·63 (s.e. 0·20) were recorded for Tl to T7 respectively. There was a quadratic relationship between plasma BHB concentration and ME intake on days 121 (R2 = 0·538, P < 0·001), 128 (R2 = 0·324, P < 0·001), 135 (R2 = 0·429, P < 0·001)) and 142 (R2 = 0·344, P < 0·002) of pregnancy. There was a positive relationship between plasma glucose concentration and ME intake on day 222 (R2 = 0·208, P < 0·002), 228 (R2 = 0·203, P < 0·05), and 135 (R2 = 0·160, P < 0·02) of pregnancy. Albumin concentrations (gll) on day 128 of pregnancy of 21·8, 21·7, 23·6, 22·9, 22·5, 22·9 and 24·3 (s.e. 0-75), on day 135 of 20·9, 23·6, 24·2, 24·1, 22·4, 24·1 and 23·8 (s.e. 0·75), and on day 142 of 16·9, 22·6, 20·7, 22·2, 20·4, 22·7 and 21·1 (s.e. 1·05) were recorded for Tl to T7 respectively. Plasma albumin concentrations were significantly affected by SBM supplementation (P < 0·05). Despite the lower than generally recommended energy concentrations in T2 to T7, the concentrations of plasma BHB were within the normal range for healthy sheep.

An initial experiment was conducted to investigate the variability of selected metabolites in the plasma from guanacos. A second experiment directly compared plasma biochemical values for guanacos with those for sheep. During the first experiment, jugular blood samples were collected from five mature castrated guanacos using an embedded experimental design. Weekly blood samples were collected at the same time (09.00 h) on the same day each week for 7 weeks. Daily blood samples were collected at the same time each day (09.00 h) during week 5. On day 2 of week 5, blood samples were collected every 3 h from 09.00 h for a 24-h period. No evidence of a cyclical pattern of plasma parameters was observed on a weekly, daily or 3-h basis. During the second experiment, the metabolic profiles of 11 mature castrated guanacos and 11 mature barren ewes (Merino × Welsh Mountain) were compared. Significant differences in plasma concentrations of all metabolites except urea-nitrogen (guanacos -15·42 mmolll, sheep - 15·60 (s.e.d. 1·506) mmolll) were found with values for guanacos v. sheep as follows: glucose (7·63 v. 3·63 (s.e.d. 0·268) mmolll); acetate (0·26 v. 0·48 (s.e.d. 0·035) mmol/l); β hydroxybutyrate (0·06 v. 0·50 (s.e.d. 0·019) mmol/l); albumin (33·4 v. 29·5 (s.e.d. 0·93) g/l); and total protein (53·8 v. 65·6 (s.e.d. 2·12) g/l); (P < 0·001 for all previous variables); non-esterified fatty acids (0·48 v. 0·29 (s.e.d. 0·048) meq per 1; P < 0·01) and a-amino N (2·44 v. 2·66 (s.e.d. 0·088) mmolll; P < 0·05). This study indicates that the reference plasma metabolite concentrations of sheep are not suitable alternatives for use for nutritional or veterinary purposes with guanacos, but those of llamas or alpacas are. The results also suggest that energy capture and transport in camelids may be markedly different from that in conventional ruminants.