1. The ‘big’ insulin content of the serums from ten children with protein–energy malnutrition was estimated before, during and after 3–6 weeks of treatment. The values for immunoreactive insulin (IRI) after intravenous injections of glucose were almost normal, with one exception, although tolerance was impaired. In addition, total body potassium content (TBK) was measured for three of the children on each test day.

2. In nine of twenty-three estimations ‘big’ insulin content was slightly more than 20% of the total IRI. However, there was a wide fluctuation in the values and no change was noted after treatment.

3. The amount of ‘big’ insulin did not correlate with either the magnitude of insulin secretion, the insulin:glucose ratio or TBK. There was a barely significant negative correlation between ‘big’ insulin content and degree of glucose intolerance, with some individual exceptions.

1. Proteolytic activity in the stomachs and pancreases of infant doe- and hand-reared rabbits was studied to the age of 3–4 weeks.

2. In the stomachs of both the doe- and hand-fed animals total proteolytic activity at birth was low, rising slowly during the first 2 weeks and then rapidly, until at 3 weeks of age the level was similar to that of the adult.

3. In the pancreases of the doe-suckled pups the level of proteolytic activity was highest during the 1st week of life, falling steadily after that to a minimum at 3 weeks of age. In contrast in the hand-reared rabbits, it fell sharply during the 1st week and then rose, reaching at 2 weeks of age a level slightly higher than that found in the doe-suckled pups.

4. Growth and survival of hand-reared rabbits during the first 12 d of life were improved by predigestion of the diet with trypsin and α-chymotrypsin.

1. Two experiments were conducted with young early-weaned lambs to measure the voluntary intake of dry concentrates when additional protein or lactose was given as a fluid preparation from a bottle.

2. The voluntary intake of a barley–urea diet (130 g crude protein/kg) was increased by 10–15% as a result of giving 2·3 g nitrogen/d as a fish-protein concentrate in fluid suspension. Amounts greater than 2·3 g N/d did not further increase voluntary intake but increased growth rate and food conversion ratio. Urea given as a solution in water in the same way in amounts equivalent to 4·6 N/d had no effect on voluntary intake.

3. The voluntary intake of a high-protein barley–fish-meal diet was decreased by giving 10 or 20% of the estimated intake as lactose by bottle. The results indicated that maximum energy intake was achieved with the basal diet, since the decrease in energy intake was about equal to the amount given in the solution bypassing the rumen.

1. The fermentation in the presence of four known methane inhibitors was investigated in rumen contents from sheep given molasses ad lib. and showing two different fermentation patterns.

2. The average hydrogen recoveries obtained with the high butyrate and high propionate patterns were 93 ± 2 and 95 ± 2% respectively.

3. Sodium sulphite, chloral hydrate and a hemiacetal of chloral and starch (HCS) all inhibited methane production, and were associated with an accumulation of hydrogen and lactate in rumen contents showing the high butyrate fermentation pattern. Propionate production was slightly stimulated.

4. In rumen contents showing the high propionate fermentation pattern, linseed-oil hydrolysate depressed methane production at high levels only, increased hydrogen and lactate production but depressed all other products, and HCS depressed methane production and slightly increased propionate production.

5. Low hydrogen recoveries in the presence of the inhibitors were probably associated with the utilization of metabolic hydrogen in reactions not accounted for in the scheme under investigation.

1. Sheep were given 800 g lucerne chaff/d and the mean half-times of cerium-144 – praseodymium-144 and the complex of chromium-51 with EDTA were 811 and 604 min in the reticulo-rumen, 37 and 17 min in the abomasum and 413 and 406 min in the caecum and proximal colon respectively. The average time available for digestion and absorption in the abomasum was therefore very short relative to that in the other two organs.

2. The half-times of the markers also indicated that particulate matter and water had different rates of turn over in the reticulo-rumen and abomasum but not in the caecum and proximal colon.

3. Evidence is presented which suggests imperfect mixing of the digesta in the caecum and proximal colon.