I . Fifty-one pregnant fine-wool Merino ewes were slaughtered at intervals during pregnancy. The gravid uteri were dissected and were separated into uterus, membrane and fluid, and foetus fractions, which were analysed separately for water, nitrogen, ash, fat, calcium, phosphorus, sodium and potassium content.2. Uteri from twenty-one similar non-pregnant ewes were also analysed for these constituents.3. A number of relationships between the composition of the gravid uterus minus the composition of the uterus taken from non-pregnant sheep, and time from conception were calculated.4. The rate of nutrient deposition was calculated from these relationships and estimates were made of the nutrients utilized for pregnancy.

1966). Comparison by direct animal calorimetry of the net energy values of an early and a late season growth of herbage.

A Phalaris tuberosa and Trifolium repens pasture was grazed continuously at stocking rates varying from 2-5 to 37-1 sheep per h a between 1964 and 1969. During this period herbage availability and composition, basal cover, root weight, water infiltration, soil moisture content, bulk density and chemical composition of the soil were measured at intervals.As stocking rate was increased, herbage availability, root weight, basal cover, soil pore space and the rate of water infiltration declined, and bulk density and the nitrogen and calcium contents of the herbage on offer increased. I n periods of below-average rainfall, soil moisture and nitrate levels were greater when herbage was of low availability.Herbage production was calculated from estimates of herbage consumption and of litter decomposition, and averaged 8-45 t dry matter/ha/year; it was insensitive to changes in stocking rate over the range from 2 to 22 sheep/ha. The ratio, herbage consumption/pasture production increased by 0'045 per unit increase in stocking rate.

Some possible sources of error when sampling oesophageally fistulated sheep at pasture were examined in eleven trials. Samples collected from sheep asted for varying periods of up to 22 hours did not differ significantly in nitrogen content from samples collected from unfasted sheep. There was no significant difference between the nitrogen content of extrusa collected at the start of a 30-minute period and that of extrusa collected at the end of the period. Sheep transferred from a perennial ryegrass/clover pasture to a native pasture for three months ingested herbage containing 3·80% nitrogen when returned to the original pasture. Control sheep which had remained on the ryegrass/clover pasture selected material containing 3·33% nitrogen. In a further trial sheep transferred from a ryegrass/clover pasture to a Phalaris/ clover pasture consumed herbage with an organic matter digestibility of 70·8 % which contained 3·44 % nitrogen. The material consumed by similar sheep which had grazed the Phalaris/clover pasture for 18 months was 71·5% digestible and contained 3·63% nitrogen.Diurnal changes in the digestibility and nitrogen content of the diet of free-grazing sheep were observed in two trials. Diurnal changes in nitrogen content were similar on different days but changes in digestibility were relatively smaller and less repeatable between days.Consistent differences in the composition of the diet selected by individual sheep and selected on different days were observed in a further five trials. Variation between sheep and between days in the nitrogen content of the diet was ±5·6% and ±7·4% respectively, both estimates being expressed as coefficients of variation. Corresponding estimates for digestibility, calculated as standard deviations, were ±1·6 and ±1·3 units. The implications of these results when sampling oesophageally fistulated sheep at pasture are considered.