Concentrations of plasma non-esterified fatty acids (NEFA) in sheep were found to be within the range 0.1–0.9 m-equiv/l. Relatively high levels (1.0–2.5 m-equiv/l) occurred in pregnant and non-pregnant sheep when fasted. Intravenous injection of glucose (1.0 g/kg body wt.) depressed KEFA concentrations to levels of about 0.05 m-equiv/l. Insulin, injected intravenously, caused an initial fall in the NEFA level, followed by a sharp rise which was maintained throughout hypoglycaemia. These results suggest that in sheep, as in many other species, NEBA are of major metabolic importance.

The net uptake and oxidation of glucose by leg muscle, pregnant uterus, and lactating mammary gland, together with the rate of irreversible loss and oxidation of glucose in the whole body of Merino ewes are reported. The ewes were fed on either chaffed oaten hay (OR), chaffed lucerne hay (L), or a mixture of chaffed oaten and lucerne hays (OHL). Measurements were made during five different physiological states: dry (nonpregnant), at 94 and 125 days of pregnancy, and at 20 and 50 days after lambing.

Glucose biokinetics of six normal pregnant/lactating ewes during the periparturient period were compared with those of five non-pregnant ewes induced to lactate artificially by treatment with oestrogen and progesterone, followed by a series of infusions of oxytocin. Normal ewes produced large amounts of milk (800-900 g/day) on day 1, and yields remained relatively constant until day 8 post partum. Milk production of induced ewes, however, was negligible on day 1 (30 g/day) but increased progressively until day 8 (540 g/day) after the start of milking. The glucose irreversible loss per minute 2-8 days before (6·4 v. 5·6 mg per kilogram body weight o . 7 5), and 2 days after the onset of lactation (9·1 v. 5·5 mg/min per kgo. 75 ) was significantly greater (P < 0·05) in normal pregnant/lactating ewes than in ewes induced to lactate artificially. By the eighth day of lactation rates of glucose irreversible loss per minute (7·4 v. 6·4 mg per kilogram body weighto. 75 ) were not significantly different (P > 0·05). The data were consistent with the hypothesis that glucose supply is rate limiting for milk production for several days after the initiation of lactation in non-pregnant, hormone-treated ewes.In parturient ewes, the rate of glucose irreversible loss was significantly increased 1-2 days post partum.

The effects of daily administration of 10 mg of highly purified ovine growth hormone (GH) for a period of 4 weeks on wool growth have been measured in 12 Merino ewes fed either a calculated maintenance energy intake or 1·6 times this amount (six on each ration). Concentrations of hormones, glucose, urea, a-amino N and amino acids in the blood were monitored and faeces and urine collected for measurement of nitrogen balance.Wool growth rate decreased by 200/0 during the 4 weeks of GH treatment in sheep fed the high energy diet, largely because of reduced wool fibre diameter. This was followed by restoration of normal growth and then an increase of up to 20% above control levels, a response which persisted for 12 weeks following cessation of GH administration, and which was due to increases in both fibre length and diameter. GH administration caused marked increases in plasma concentrations of GH, insulin and somatomedin C, glucose and free fatty acids, all of which returned to basal levels following cessation of GH administration. No consistent changes in plasma concentration of T 3 , T 4 , cortisol, prolactin or a amino N were detected. Plasma urea and methionine levels decreased during GH treatment and returned to, or were raised above, basal levels after the GH treatment period. GH injection also resulted in a net retention of N during treatment, followed by a transient period of net N loss.The GH-induced changes in wool growth may be caused by a change in the partitioning of amino acids between the muscle mass and the skin. No other contributing factor(s) were identified.