1. A large-scale grazing management study comparing rotational grazing and continuous grazing with dairy cows at two stocking rates over four complete production seasons is described.

2. The four treatments were: (i) controlled grazing, light stocking rate; (ii) controlled grazing, heavy stocking rate; (iii) uncontrolled grazing, light stocking rate; (iv) uncontrolled grazing, heavy stocking rate.

Each treatment involved 40 cows for a first 2-year phase and 42 cows for the following 2 years. Each herd had a normal age distribution pattern and seven 2-year-old first lactation heifers (17% of total herd) were introduced each year to maintain this pattern.

3. Stocking rate was the more important factor affecting the efficiency of pasture utilization as measured by per acre output of milk and butterfat. In general, high stocking was associated with higher outputs per acre despite lower yields per animal.

4. Grazing method was of less importance. In general, controlled rotational grazing was superior to uncontrolled continuous grazing, both per animal and per acre, but the average influence even of these extremes of management was only half that of stocking rate.

5. Significant interactions between stocking rate and grazing method existed. Under continuous grazing a point was reached where production per acre declined to the vanishing point with increased stocking rate due to excessive depression of per cow yield: this point was not reached under rotational grazing at the same high stocking levels.

6. The results suggest that optimum stocking rate under rotational grazing occurs at a level some 5–10% higher than under continuous grazing. A depression of 10–12% in per cow yield, compared with more lenient grazing, corresponds with optimum stocking level irrespective of the grazing system. This estimate is suggested as a guide line in applying the principles involved.

1. An artificial diet low in magnesium (0·01–0·02% of the dry matter), and providing about 0·5 g. magnesium daily, was prepared from paper pulp, maize gluten, magnesium-free minerals and vitamins A and D and used in experimental studies with two non-lactating cows.

2. The omission of a dietary supplement of magnesium oxide (5 g./day) caused a rapid fall in the excretion of magnesium in the urine, from values of 1–2 g./day to virtually zero within about 4 days. There was a similar rapid fall in the concentration of magnesium in the serum, from about 2·7 to 2·0 mg./lOO ml., and then a slow fall to between 1·0 and 1·5 mg./lOO ml. after 12 days. Faecal excretion of magnesium was also reduced but the faecal loss continued at about 1·0 g./day after 2–3 days on the low magnesium diet.

3. The availability of the magnesium of various salts was determined by giving them as supplements to the basal diet and measuring the increase in the excretion of magnesium in the urine. The mean value was 26·2% in one cow and 34·5% in the other, a highly significant difference (P < 0·01). The availabilities of the oxide, nitrate, acetate and lactate were similar, but the citrate gave a higher value and the sulphate, silicate and, in one cow, the chloride a lower value.

A long-term experiment designed to study the effects on crop yields of different basic methods of cultivation used in the preparation of seedbeds is described and the results of the first completed cycle of 4 years are discussed. Four basic methods of cultivation were compared, namely, ploughing, rotary cultivating, cultivating and discing. Each one of these was done, early and late, for each crop in two four-course rotations which differed only in the cropping of 1 of the 4 years when potatoes were used in one case and a 1-year ley in the other. Each crop in the rotation (winter wheat, sugar beet, barley, ley or potatoes) was grown at two levels of fertilizer application and provision was made in the design of the experiment for two different weed control régimes. The soil was fairly easy to work, being of the Milton series of river gravels.

As a result of the work described, the following conclusions have been drawn:

1. Ploughing was the most consistent method of providing a satisfactory basis for the final seedbed preparation but in some circumstances other methods were equally good. On average, ploughing led to the highest yields and discing the lowest, with rotary cultivating second and cultivating third in order of merit.

2. The yields of cereals grown after root crops were not dependent on the method of basic cultivation used.

3. The effects of the cultivations on the yield of winter wheat after the ley appeared to be due to the extent to which the regrowth of rye-grass was controlled, the plough being most effective in this respect.

1. Two trials are described in which the live weights of sheep grazing four different pastures were compared. The four pastures comprised perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S), short-rotation rye-grass plus white clover (S + C).

2. Large and highly significant differences existed between the mean live weight of the sheep on the various pastures in each trial. Thus the P sheep had a mean live weight of 107 and 102 lb. in trials I and II, respectively, at the end of each investigation, the P + C sheep 123 and 122 lb., the S sheep 125 and 126 lb., and the S + C sheep 140 and 137 lb.

3. The differences in live-weight growth on the four pastures contain two major effects; an effect due to the difference between P and S and an effect which can be attributed to the presence of white clover in the pasture treatment.

1. The results of two trials with Romney ewes grazed on perennial rye-grass (P), perennial rye-grass with white clover (P + C), short-rotation rye-grass (S) and short-rotation rye-grass with white clover (S + C) are reported. Chemical and dissection analyses of their carcasses were made and the weights of certain internal organs were obtained.

2. It was found that the sheep grazed on the P plots had the lightest carcasses (56·2 and 40·9 lb. in trials I and II, respectively), followed by those on the P + C (70·2 and 59·2 lb.), by those on S (74·7 and 61·2 lb.) and the heaviest carcasses were yielded by sheep from the S + C plots (81·5 and 69·1 lb., respectively).

3. The weights of dissectible fatty tissue and chemical fat of the carcasses were related to the carcass weights of the different groups of sheep; the group with the lightest carcass weight had the least fat. The other components of the carcass (protein, water and ash) followed the order for group mean carcass weights except that the S carcasses in trial II had slightly less water, protein and ash than the P + C carcasses. The percentage chemical fat of the S carcasses in trial I was also lower than the P + C carcasses.

4. In general, the non-carcass components of live weight (head, feet, skin, liver, mesenteric fat, omental fat, kidneys, stomach empty, and intestines empty) all followed the same pattern of increasing weight (P < P + C < S < S + C).

1. The mean thyroid weights of ewes grazed on the different pastures (perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S), short-rotation rye-grass plus white clover (S + C)) did not differ significantly, but those injected with iodinated poppy-seed oil had lighter (P < 0·01) thyroids than the non-injected ewes grazed on the same pastures.

2. Neither the live weights of the ewes nor their lambing performances were affected significantly by treatment with iodine.

3. Lambs from ewes grazed on pastures containing white clover had thyroid glands significantly heavier than those of ewes grazed on rye-grass pastures. The largest thyroids were from the lambs of ewes not treated with iodine and grazed on S.

4. The iodine contents of the thyroids of the lambs at slaughter, measured as percentage dry weight, did not differ significantly. It seems likely that the differences in thyroid weights were caused by factors operating early in the lives of the lambs.

5. The lambs of ewes injected with iodine grew faster after weaning than those of non-injected ewes on the same pastures. The interpretation that this difference was in fact caused by the iodine treatment of the ewes was not wholly acceptable, because the differences in growth rate were not greatest in those groups of lambs showing greatest differences in thyroid weight.

1. A preliminary study has been made of some aspects of rumen development and fermentation patterns in groups of ewes and lambs fed perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S) and short-rotation rye-grass plus white clover (S + C).

(2) For ewes there was a significant effect on the weight of the rumen contents from the grass species. The treatment (P) which caused the lowest live weight gave the highest rumen contents weight. There were also significant pasture effects on empty live weight both from grass species differences and from the addition of clover.

3. No difference in rumen dry-matter percentages was found between the four groups.

4. There was no significant difference in the concentration of volatile fatty acids in the rumens of the P and S fed ewes but the addition of white clover had a significant effect.

5. The S + C sheep had a lower proportion of acetic acid, a greater proportion of propionic and butyric acids and greater development of the rumen papillae than the P animals.

6. With the lambs there were no significant differences in rumen characteristics caused by grasses but the addition of white clover caused a greater live weight and a reduction in the weight of the rumen contents.

7. These results are discussed in relation to present knowledge of ruminant metabolism.

1. A co-ordinated trial has been carried out at eight centres to compare the performance of group-fed pigs slaughtered at about 200 lb. live weight (bacon weight) with that of litter-mates slaughtered at 260 lb. (heavy pigs).

2. The bacon pigs were fed either ad lib. or restricted according to live weight, while the heavy pigs were all fed ad lib. with one group having the protein supplement withdrawn from the ration after the pigs had reached 140 lb. live weight.

3. Growth rate, efficiency of food conversion and carcass quality (based on dissection) data are summarized in Table 5.

4. In general, the results indicated that under the conditions that prevailed, and when the leanness of the carcass is the major consideration, the slaughter weight around 200 lb. was preferable to the heavier weight (about 260 lb.) both from the production and economic aspect.

1. A 36-day continuous digestibility trial with three steers and three sheep fed fresh pasture herbage was carried out during May and June, 1960. For all animals the digestibilities of herbage organic matter (O.m.) were estimated both by collection of faeces and by administering standard quantities of chromium sesquioxide (Cr203) twice daily and determining concentrations of Cr203 in faeces. In a further 36-day trial during August and September 1960, three steers and three cows were used; with the steers, digestibilities were estimated by both methods but with the cows by the Cr203 method only.

2. Regression equations were obtained relating O.m. digestibility to the percentage of nitrogen (N) in faecal O.m. When digestibilities were estimated by the same method the same regression coefficients could be fitted to the data from each of the steers and sheep in the spring trial. A similar result was found with the data from each of the steers and cows in the summer trial.

3. In each equation different constant terms were required for each animal, which differed significantly between individuals but not between species or class of animal. Data obtained from an examination of the relationship of g. N excreted per 100 g. feed dry matter to g. N intake per 100 g. feed dry matter indicated that differences between the constant terms could be linked with variations between animals in the excretion of metabolic faecal N.

1. ‘Wet’ soil plants had greater tiller and leaf number, and were also taller than ‘dry’ soil plants.

2. The straw and grain dry weight, and grain weight as percentage of straw weight, were greater in ‘wet’ soil plants than in ‘dry’ soil ones.

3. Wet soil hastened the time of ear emergence.

4. Increasing the phosphate supply, on the whole, tended to increase the tiller and leaf number, weight of straw and grain and also hastened time of ear emergence.

5. Under ‘wet’ soil conditions high phosphate application is not necessary.

6. The yield of grain at high phosphate level of plants grown on ‘dry’ soil is significantly lower than the yield from those grown on ‘wet’ soil with low phosphate application. This suggested that under ‘dry’ soil conditions availability of nitrogen, as well as of phosphorus, is a limiting factor.

1. A comparison was made of the carcass composition at 56 days of age of early-weaned pigs grown along predetermined growth curves to 30, 40 and 50 lb. live weight and of suckled pigs grown to 50 lb. live weight at 56 days of age.

Eight blocks of four pigs were slaughtered when 56 days old and comprehensive carcass dissections undertaken.

2. There were no differences in the proportionate weight of the joints or of individual bones between the suckled and early-weaned pigs weighing 50 lb. at 56 days of age.

The difference in the proportionate weights of the joints between the three groups of early-weaned pigs reflected the change in development which took place with increasing live weight. There was, however, no clear gradient of development along the bones of the limbs with increasing weight at 56 days of age.

3. The dissected joints (hams, shoulders, neck, pelvis and loin) from the early-weaned pigs which weighed 50 lb. live weight contained 0·5% less bone, 1·5% less muscle and 1·7% more fat than the carcasses of suckled pigs reared to 50 lb. at 56 days of age.

The dissected joints of the early-weaned pigs reared to 30 lb. at 56 days of age contained 1·4% more bone, 2·7% more muscle and 5·3% less fat than the joints of the early-weaned pigs reared to 40 lb. and 2·6% more bone, 5·2% more muscle and 8·8% less fat than the joints of early-weaned pigs reared to 50 lb.

1. Twenty blocks of four litter-mates were individually fed under standard conditions from 56 days of age to 200 lb. Each block consisted of three early-weaned pigs reared to 50, 40 and 30 lb. live weight, respectively, at 56 days of age and a suckled pig reared to 50 lb. live weight at 56 days of age.

2. There was no difference in the growth rate and feed conversion from 56 days of age to 200 lb. of the early-weaned and suckled pigs reared to 50 lb. at 56 days of age.

The age at 200 lb. of the 30, 40 and 50 lb. early-weaned pigs were 169·8, 176·8 and 182·7 days and the lb. of meal per lb. live-weight gain 3·3, 3·2 and 3·1 lb., respectively. A reduction in 56-day weight led to an increase in growth rate and feed conversion from 50 to 200 lb. live weight.

3. The conformation and composition of the bacon carcasses of the 50 lb. early-weaned pigs were not significantly different from the carcasses of the suckled pigs which also weighed 50 lb. at 56 days of age.

An extensive examination of the carcasses of early-weaned pigs showed that an increase in 56-day weight from 30 to 50 lb. live weight signifieantly reduced the weight of muscle present and significantly increased the amount of subcutaneous fat. The conformation of the carcasses was not affected.

During the last 5–6 years, many visitors to this Institute have expressed interest in the apparatus used in the Nutrition Department to collect the total urine excreted by male cattle and sheep. The apparatus has now been in continuous routine use for over 6 years and can be regarded as very reliable. This note describes the equipment, shown diagrammatically in Fig. 1.

1. The direct and indirect effects of low rainfall on the problems of cattle husbandry in East Africa are discussed, and an example of what these problems mean in practice is described.

2. A co-operative experiment is described that was planned to assess the water requirements of Bos indicus type cattle in a semi-arid region of Tanganyika, and to determine the effect of water deprivation on cattle productivity.

3. Ten sets of identical twin zebu (Bos indicus) or part-zebu cattle were used in this experiment. The basic layout consisted of two treatments, an ‘experimental’ and a ‘control’, one twin from each set being placed on one or other of the treatments. Twins in the ‘experimental’ group were used to determine the effect of watering at 24-, 48- and 72-hr. intervals and of forced walking of 3, 6 and 10 miles per day in addition to normal grazing exercise. The experiment lasted 2 years from 16 April 1960 to 11 May 1962.

4. Climate at the experimental site, the experimental layout, the experimental animals and grazings, management of animals and grazings and experimental observations are described in detail.

5. Data on seasonal changes in the nutrient content of forage on the grazings is given, and the effect of these changes on the nutrition of the experimental cattle is discussed briefly.

The problems involved in estimating the food intake of the grazing animal are considered and an account is given of studies made on eighteen Clun ewes and six Hampshire × Clun wethers. Results are given from sixty-eight observations on the relationship between food intake and a fraction dissolved in the faeces when a milled sample is left to stand in 0·2N-HCl for 18 hr. Using, in addition, data from grazing ewes subjected to total faeces collection during winter and spring 1959–60 it is concluded that 4 consecutive days of collection give a reasonable estimate of faecal output, and that where similar groups of sheep are grazing on the same pasture at the same time it is unnecessary to convert faeces output data to intake figures in order to compare intake-production relationships between individuals within a group. Where, however, comparisons are to be made between individuals or groups of sheep grazing different pastures at different times then it becomes necessary to allow for differences in food-faeces ratios; for this purpose the dissolved fraction discussed here is likely to prove a useful faecal indicator eliminating many disadvantages of earlier methods and some of the seasonal bias inherent in other indicators at present in use.

1. Nine Ayrshire calves were subjected in a climatic room to temperatures in the range 15–41° C., and moisture vaporization rates were measured, by means of ventilated capsules, from various skin regions.

2. The rise in moisture vaporization rate, during the early part of exposures to high temperatures, occurred in a series of steps. This was attributed to bursts in sweat gland activity.

3. At low environmental temperatures the moisture vaporization rate was small and similar in all regions. At high temperatures evaporation differed widely between regions. The regional distribution was similar for all animals and agreed broadly with results that have been reported for other breeds.

4. The regional distribution of moisture vaporization was not appreciably altered as animals aged from 10 to 34 weeks, but the evaporation from all regions increased during this period.

Three sowings of marrowfat peas were made at about 20-day intervals at forty-seven centres in eastern England over 4 years. The sowing period ranged from late February to late April, varying with seasonal conditions. Bird damage caused considerable loss of sowings but satisfactory yield data were obtained from forty-one of the trials.

Highest yields were obtained from drillings made in the last 10 days of February. After mid-March each week's delay in sowing resulted in a yield loss of about 3/4 cwt. per acre. Quality fell off slightly from February onwards.

Early sowings suffered some loss of plant in tractor wheelings but were negligibly affected by cold weather.

Early sowings appear likely to encounter better harvest weather than late sowings and the chances of good harvest weather seem appreciably better in the centre and south of the pea-growing area than in the north. Early sowings mature before the cereal crop, enabling better attention to be given to the pea harvest.

It was concluded that the crop should be sown as soon after the middle of February as soil conditions allow.