Seven different experiments over 3 years and involving a total of 1750 ewes have been designed to study the effects of high and low levels of nutrition during pregnancy and during lactation on grazing sheep. The trials were run as nearly as possible under typical fat-lamb producing conditions. Commencing with breeding ewes in average store condition before tupping, a live-weight gain of 25–40 lb. from tupping to lambing was adopted as a standard of a high level of feeding and a gain of ± 5 lb. was considered to be a low level of feeding. Differential feeding was obtained by keeping the ewes on high-quality pasture as a high level of nutrition, and by stocking heavily on poor pasture as a low level. Under these conditions the following results were obtained:

(1) Level of nutrition during pregnancy. The high level of nutrition during pregnancy increased birth weight by about 0.5 lb., but had little if any influence on the rate of growth and the weaning weight of the lambs, irrespective of the subsequent level of nutrition. The high level did not reduce ewe and lamb mortality and there was some evidence to the contrary when the high plane was applied early, leading to large live-weight gain.

1. The changes in the sheep population and in the sales of fat sheep have been examined for the West Wales region for the period 1940–8. These changes consist of a gradual annual decline in sales, whilst the severity of the 1947 winter conditions brought about a rapid drop in both sales and population by nearly 33% from 1946 to 1947.

2. Analyses of sales of the four categories of fat sheep—rams, ewes, sheep and lambs—throughout the twenty-five collecting centres have been completed for the 4 years, 1943–6. These showed that lambs accounted for 85% of the fat sheep sales in this region.

3. It was found that the average estimated dressed carcass weight (e.d.w.) of the four categories of sheep (rams, ewes, sheep and lambs) declined gradually from the collecting centres of west Pembrokeshire to the inland centres on the eastern boundaries of the region. This cline is also found in the case of the summer suckling lamb, the autumn wether lamb and the winter-fed fat lamb.

1. The myoglobin contents of selected muscles in horse, pig, domestic fowl and pigeon, and in the foetuses of horse, pig, sheep and cattle, have been determined.

2. The order of increasing concentration of myoglobin in the adult animal (4 years) is given by the series heart, longissimus dorsi, diaphragm and psoas, the figures for draught horse being, respectively, 0·325, 0·465, 0·610 and 0·705% and for pig, 0·203, 0·280, 0·350 and 0·435%, and the ratios of these concentrations being the same in each animal.

3. In both draught horse and pig, it is shown that the concentration of the pigment rises rapidly from birth, and that, after 2 years in the horse, and 1 year in the pig, it remains fairly constant, except in the case of horse psoas and diaphragm where there is a slow, but significant, rise throughout life.

4. This relationship of myoglobin with age has been shown to be significant at a probability level of 0·1%.

1. Three experiments confirmed the view that losses, poor weight gains and low food consumption were always problems among pigs reared in an open pen in a large uninsulated building in comparison with the better results for pigs reared in wooden ark huts. Pigs in an ark hut with an outdoor run did better than those in one with an indoor run.

2. The effective temperature of the different types of housing was estimated. The differences found were not large but the environment which produced the best pigs had the highest effective temperature.

3. The provision of an insulated, dry floor to sleep on made it possible to rear good pigs in a pen where before they had failed. Woollen jackets did not provide sufficient insulation to affect the growth or health of pigs in a hut or pen.

The analysis of simple change-over trials based on Latin squares is considered. It is shown that several difficulties are encountered when estimates of residual effects are required. In particular, there may be biased error variances.

In certain circumstances the amount of bias in the error variance can be estimated in a proportion of the experiments based on a given design. If this bias is sufficiently large to be of importance an average correction can be calculated for use with further experiments of the same type.

The problems arising in the analysis of changeover trials based on complete Latin squares have been independently investigated by Dr H. L. Lucas, of the Institute of Statistics, University of North Carolina, who is preparing a book on the subject of animal experimentation. Dr Lucas has obtained similar results to those presented in this paper. He has also conducted a more extensive investigation of the magnitude of the bias in the error variance, and has come to the conclusion that in experiments on dairy cows it is not of sufficient magnitude to be of practical importance. These results will shortly be published.

1. An experiment was carried out from 3 May to 10 October 1949 to compare close-folding with rotational grazing of dairy cows. With close-folding the cows were moved daily to an area of fresh pasture which was calculated to supply the day's feed requirements; the rate of stocking ranged from 50 to 80 cows per acre. With rotational grazing the cows were stocked on pasture at the rate of 6–8 cows per acre and moved from one pasture to another at intervals of 5–14 days. Two uniform groups of Ayrshire cows were used, and each group spent a period on each system of grazing. Two pastures, a ryegrass-dominant old pasture and a cocksfoot-dominant ley, were used, and as far as possible the pasture grazed by both groups of cows was similar. Nitrogenous top dressings up to 104 Ib. nitrogen per acre in the season were applied uniformly to both the close-folding and rotational areas. No supplementary feeding was given to the cows.

2. The best methods of close-folding practised gave 215 and 201 cow-days of grazing per acre with 550 gal. milk per acre from the cocksfoot ley and 582 gal. from the permanent pasture. Rotational grazing on the same two pastures gave 181 and 138 cow-days and 450 and 351 gal. milk per acre respectively.

1. An attempt has been made to measure the amount of herbage eaten by groups of milking Ayr shire cows when grazing under two different systems, (a) close-folding and (b) rotational.

2. Under close-folding the daily consumption of dry matter varied from 18 to 27 lb. per cow. Long herbage reduced the amount eaten. Considerable increases in the weight of herbage offered resulted in only slightly increased consumption. On good leafy pasture the dry-matter intake was about 24 lb. per cow per day.

3. Under the rotational system the intake was more constant at about 28 lb. dry matter per cow per day. Some abnormally low results were obtained which were associated with the difficulty of obtaining a representative sample of herbage, particularly after grazing.

4. Frequent chemical analysis of the pasture before and after grazing on the close-folding system were made, and the intake of the major grass constituents calculated. A comparison of nutrient intake as calculated from these results with that theoretically required has been made.

The investigations carried out refer to the relative degree of accuracy obtained when weighing grazing bullocks at different times during the day. An endeavour was made to find a time when animals could be weighed with the minimum of disturbance in their grazing habits and when the weights recorded had the minimum day-to-day variation.

It is suggested that weights recorded early in the day when the animals are generally of a constant habit have day-to -day variations comparable to those obtained after overnight fasting.

Alternatively, it is suggested that cattle at grass should be weighed after fasting overnight. In this case the fast should follow ‘the-end-of-evening’ grazing and water should be provided in the fasting yard.