A study has been made of some of the nitrogen fractions of the pegasse soils of British Guiana in virgin and exhausted conditions, that is, before and after cropping.

1. Preliminary field experiments on the virgin and exhausted soils adduced strong evidence in support of the complaints made by farmers that the productivity in yields of the pegasse soils after continuous cropping for a comparatively short period is considerably impaired.

2. The virgin soil showed an appreciable amount of nitrate nitrogen, while the exhausted sample indicated no nitrate. The latter soil, on the other hand, contained a higher amount of ammonia nitrogen measured by KCl extraction than the former soil.

3. Nitrification studies with added ammonium salts indicated that under optimum conditions the nitrifying power of the exhausted soil was extremely low. Additions of sodium nitrate indicated that the nitrate was partially reduced to ammonia by the worn-out pegasse soil. The virgin pegasse, on the other hand, showed an appreciable rate of nitrification.

The investigation shows that when water-logged soils were treated with nitrogenous manures and fertilizers like oil cake, water hyacinth, ammonium sulphate and sodium nitrate, a large volume of nitrogen evolved as gas. This loss began 7–12 days after application of different treatments and was quicker from inorganic fertilizers than from organic manures. Besides loss as gas, a large amount of nitrogen was also lost in the drainage. The results suggest that if fertilizers like ammonium sulphate and sodium nitrate are applied to rice-fields by top dressing during the active vegetative growth of the crop, the loss nitrogen as gas will probably be greatly minimized.

1. A method of perfusing the skin of the flanks and the backs of Ayrshire calves and embryos with indian ink is described.

2. The distribution of blood vessels in the perfused skins has been studied.

3. Three plexuses of blood vessels have been observed in the skins. The first lies below the corium; the second is at a level between that of the ‘sweat glands’ and the sebaceous glands; and the third extends from beneath the epidermis to above the second plexus and is a deep network of many fine blood vessels.

4. The presence of venae comites in the skin is discussed.

5. The ‘sweat glands’ appear to have a very poor blood supply, while the hair follicles and papillae are richly supplied.

6. Both the ‘sweat glands’ and the hair follicles are supplied with blood from the second plexus.

7. The vessels of the third plexus appear to enmesh the individual hair follicles at different levels.

8. Blood vessels supplying the skin in the back and flanks of the animals originate from the intercostal arteries and so pass through the heat generating intercostal muscles.

Short columns of air-dry soil crumbs were wetted at different rates and, after draining to a standard suction, the amount of water taken up by each column determined. It was found that this in the other under continuous grass. The extrapolated value of the cohesion of the grassland crumbs at zero rate of wetting was twice that of the arable, indicating an additional cohesive force in the grassland crumbs. The cohesion of the arable soil fell much more rapidly with increased rate of wetting than that of the grassland, probably because the roots in the grassland crumbs provide easy escape passages for the air.

The increase, with rate of wetting, of the amount of water held by a soil sample against a given suction is important, at least up to 200 cm. of water. This dependence of the pF curve on rate of wetting is of particular significance for laboratory studies of water movement in soils.

1. Nitrogen-balance experiments showed that casein supplements fed to hill ewes on a low plane of nutrition in the later stages of pregnancy were used very ineffectively, despite the animals' need for protein.

2. In confirmation of McDonald (1948a, b, 1952) extensive conversion of casein to ammonia was found to occur in the rumen, with absorption of ammonia into the blood stream.

3. Casein administered to sheep by duodenal fistual was better utilized than when administered by ruminal fistula.

4. The course of dissolution in the rumen of casein in the form of tough lumps was observed by a staining procedure.

5. It was found possible to process casein in a way that led to better utilization as shown by nitrogenbalance experiments. This processed casein gave less ammonia in the rumen.

6. It is concluded that the formation in the rumen of ammonia from proteins may be an important factor determining their usefulness to the animal. Processing may have effects on the value of a protein for ruminants quite different from those on the value for non-ruminants. The tendency to value proteins for ruminants solely in terms of their digestibility is criticized, and it is suggested that casein has disadvantages as a ‘standard protein’ in nutrition experiments with ruminants.

1. During the period May 1948 to May 1952, a study was made of the influence of seasonal fluctuations in the nutritive value of the natural pastures in the Bankenveld region of the Transvaal, on the growth, reproduction and production of cattle. The paired method of investigation was adopted, each heifer maintained on grazing alone having a related counterpart of the same age which received supplementary feeding during the winter months. The former treatment was termed ‘Low plane’, and the latter referred to as the ‘High plane’. Four breeds were included in the investigation, viz. Friesians and Jerseys, and Shorthorns and Afrikaners, thus representative of both dairy and beef types. The latter breed also represented the stock indigenous to South Africa. Initially five pairs per breed were studied, but deaths and other causes depleted the numbers to twenty-eight head after 4 years of investigation.

2. Since the investigation formed part of a series of studies which have been in progress at the University of Pretoria and Agricultural Research Institute during the past two decades, the results of which hitherto remained unpublished, a review is provided in the early chapters. To furnish some indication of the natural conditions ruling in the Bankenveld region, the agro-ecological background is discussed, particular attention being paid to physical and nutritional factors. It is shown that for at least 6 months of the year the climate tends to be subtropical, whilst the results of digestion trials on pasture samples, indicated serious nutritional depressions in the natural grazing during winter.

1. A feeding trial is described including four groups of cattle fed on silage only, two mixtures of silage and roots, and roots, straw, hay and oats.

2. The live-weight gains made are recorded together with the rate of dry-matter intake.

3. The efficiency of the dry matter of the diets was calculated.

4. Silage fed alone produced a significantly greater rate of fattening than the other three diets.

5. Cattle receiving roots in the morning and silage at night consumed 10·78% more dry matter and made greater live-weight gains than cattle fed on silage in the morning and roots at night.

6. Calculation of the starch values of the roots and silage showed that these are higher when fed together than when silage is fed alone or when roots are fed with straw, hay and oats.

7. An experiment is described designed to determine the effect of the dry-matter percentage of the diet on dry-matter intake in ruminants and of sudden changes in dry-matter content on digestibility.

8. Sheep receiving 19·46% dry-matter silage consumed 16·7% more dry matter and 19·8% more starch equivalent than sheep eating 15·85% dry-matter silage.

9. When the dry-matter percentage of the silage fell from 19·46 to 15·77 the digestibility of the dry matter fell by over 10%.

10. The starch equivalent of the silage when fed alone was determined from the results of a digestibility trial and according to the performance of the cattle in the feeding trial. The values found were 65·88 and 66·15% respectively.

11. The losses suffered in silage-making in twentyfive silos are recorded and discussed. The loss of dry matter and crude protein both average approximately 40% of that ensiled. The need for finding methods of reducing these losses is again stressed.

1. A study has been made of the cause of urine burn in pasture.

2. It has been shown that urine burn could occur under dry soil conditions due to the osmotic pressure effects of the urine.

3. All seeds present in the urine-affected soil are killed.

4. An inhibitor of root growth, to which clover roots are especially sensitive, is present in the urine of cows and sheep.

5. This inhibitor, which is not heteroauxin, is acid in character and is destroyed in soil in a few days.

6. It is suggested that the inhibitor is an inhibitor-auxin complex, of which the auxin portion might be heteroauxin. The possibility that the inhibitor is an auxin precursor is discussed.

7. It is contended that the reduction of clover growth relative to grass growth in a urine patch is not simply the result of shading due to increased grass growth.

8. The root inhibitor, the temporarily high pH, the presence of free ammonia, and the high concentration of ammonium ions may be important factors in the reduction of clover growth.

1. Herring-meal supplements fed to sheep on a basal diet low in protein were more effective than casein supplements in promoting nitrogen retention and growth.

2. The herring-meal supplements caused less extensive formation of ammonia in the rumen than did the casein supplements. This is considered responsible for the differences found in the value of the proteins.

3. Meat from the sheep fed herring meal was not tainted in flavour.

4. The use of formaldehyde to preserve herring before making them into meal had no deleterious effects when the meal was fed to sheep.

1. Studies were made during the 1951 and 1952 seasons of the oxalate contents of the leaves of mangolds, sugar mangolds and fodder sugar beet.

2. In all varieties greater concentrations of total oxalates were found during the summer months, the amounts diminishing gradually as the season advanced. Up to 12% was found in the dry-matter of mangold leaves and 9% in fodder sugar-beet leaves in July, these levels falling to 3% by mid-winter. There is some evidence that these changes are due in part to loss of outer leaves.

3. Roughly one-third of the oxalates are present in water-soluble form. The addition of 1 part of chalk to 1000 parts of leaves, as has been generally recommended, is theoretically sufficient to render unavailable the soluble oxalates present during winter, but insufficient for leaves fed earlier hi the season.

4. A number of observations showed small reductions in the soluble oxalate contents of the leaves due to wilting, but there were exceptions to this, and these appear to be related to sampling periods rather than to varieties.

5. Insoluble oxalates appear to be unaffected by wilting and may show apparent increases in amount due to respiration losses of labile leaf constituents. The insoluble/soluble oxalate ratio is thus changed by wilting.

6. It is suggested that the undesirable effects sometimes resulting from the feeding of beet leaves to livestock may not be due to oxalates, but that other factors present, which are labile during wilting, may be involved.

1. Two sample cockerels from each plane of nutrition treatment were killed and dissected at 0, 4, 10, 15 and 24 weeks of age. Details of the dissection technique are given.

2. All organs and tissues were weighed both wet and oven-dried. The total dry-matter content of the birds increased from 21% at hatching to 32% at 24 weeks.

3. The chief age changes in the proportions of the major joints of the bird consist of a marked increase in relative mass of wing, and a lesser increase in the leg joints. The early maturing head and neck joints decrease in relative mass by approximately onehalf. There are no treatment differences in the gross proportions of the birds calculated on the basis of weights of the major joints.

4. The advantages and disadvantages of the various methods of presenting quantitative growth analysis data are discussed. Reasons are given for employing several different methods in this work.

5. The amount of fat in the carcasses analysed varies considerably between individual birds. There are no consistent age or treatment effects on the fat contents of the cockerels. The interpretation of McMeekan's dissection analysis data is discussed, and reasons are advanced for conducting future experiments of similar nature on the basis of a fatfree carcass. It is argued that adipose deposits should not be considered in the same category as body organs and tissues.

1. Examination of the composition of hay grown in the east of Scotland during the 4-year period 1948–51 has confirmed earlier work indicating the low protein content of this material. In addition, the digestibility of the protein was found to be low, particularly in the case of the seeds-hays, most of which contained insufficient digestible protein to balance the starch equivalent in meeting the maintenance requirements of cattle.

2. In nutritive value the seeds -hays were markedly inferior to samples from England and Wales examined by other workers, but very similar to mature ryegrass hay grown in Northern Ireland. The meadow hays examined were of similar starch equivalent but somewhat richer in protein, and this was associated with a higher digestibility of the protein; in consequence the ratio between digestible protein and starch equivalent was more nearly balanced for the maintenance feeding of cattle.

3. Applications of sodium nitrate or ‘Nitrochalk’ about 10–20 days before mowing produced very variable responses in the unusually dry season of 1949, but in other years significant increases in protein content were almost invariably obtained. Low protein seeds-hays of the type commonly found in the Lothians were more responsive to this fertilizer treatment than timothy meadow hay, and while increases in protein content of 20–30% were commonly obtained, when relatively heavy dressings of fertilizer (3 cwt. or more per acre) were used, increases in the region of 50% were sometimes recorded. In most years treatment about 10 days before mowing was fully effective in improving the protein content of the hay. Earlier treatment may be preferable in a very dry season, but in more normal years this may increase the yield of the hay and so diminish the effect on protein percentage.

Observations were made on four Suffolk lambs from birth to 14 months of age, wool and skin samples being taken periodically. The lambs were on a high nutritional plane and grew well throughout the experiment.

1. There is good agreement between estimates of growth based on body weight, calculated surface area, and expansion of tattooed squares.

2. Fibre Type Arrays were Valley or Plain.

3. Benzene tests showed considerable medullation in the fleeces of all the lambs, mainly in the posterior parts. There were practically none on the shoulder.

4. The weight of keratin produced daily per unit area of skin reached or exceeded the figure given as maximal by Galpin (1948) in only six samples, of which four were grown prior to 1 month old.

5. The follicle population completes its development early, only a few secondary follicles being added after birth. The definitive S/P ratio is 5/, which is similar to the Leicester, and lower than in the Romney breed. The follicle density, although high at birth, is lower than in the Romney or Leicester, after 9 months old. Both S/P ratio and follicle density are higher than in the Blackface breed.

6. The transitory black colour of the birth-coat of Suffolk lambs is due to pigmentation of the tips of many fibres; this may affect any type of fibre from haloes and sickles to histerotrichs. With very few exceptions all follicles cease to produce pigmented fibre at or shortly after birth of the lamb. Large amoebic melanoblasts are present in the skin.

1. Ruminal ammonia concentrations were measured in sheep receiving basal diets of hay and meals with various supplementary sources of protein. Ammonia production from groundnut meal was great and from maize products slight. Herring meal behaved in an intermediate way.

2. The extent of ammonia production from a given amount of protein-rich material was decreased when the amount of starch or cereal meal fed at the same time was increased.

1. The amounts of amino sugar-N present in acid hydrolysates of six soils with nitrogen contents ranging from 0·17 to 2·82% have been estimated by colorimetric and alkaline decomposition methods.

2. Recovery of amino sugar-N after hydrolysis of chitin or glucosamine was found to be unaffected by the presence of soil during hydrolysis.

3. Substances known to interfere with the methods of amino sugar analysis employed were not detectable in the soil hydrolysates.

4. From the amounts of amino sugar-N liberated by acid hydrolysis it is deduced that 5·10% of the total-nitrogen of the soils examined was in the form of amino sugars.

5. The decomposition of amino sugars in soil has been studied by comparing the rates of decomposition of chitin, glucosamine, casein and yeast nucleic acid when incubated with soil under conditions found to produce rapid nitrification of ammonium sulphate.

6. Glucosamine and chitin are readily decomposed by soil micro-organisms but not so rapidly as casein or yeast nucleic acid.

1. Experiments were carried out to test the effects of the three main mineral fertilizers on the secretion of nectar by apple, mustard and buckwheat. Factorial designs were used, and data on plant growth were collected in order to attempt to relate growth to nectar production. Apart from the apple trees the plants were cultivated in clean sand to which known quantities of pure minerals were added.

2. Apple. The mean quantity of sugar per flower was significantly increased by extra potash; phosphate also tended to increase it. At the higher level of potash, nitrogen had significantly increased the crop of apples the previous year; it decreased the nectar yield. Potash increased nectar yield most when its effect on the crop had been small, and vice versa.

3. Mustard. In this experiment the quantity of water supplied to the plants was varied as well as the fertilizers. On the last sampling occasion nectar was more frequently obtained from plants with the lower dose of nitrate than from those with the higher dose. At the high level of water, and with low nitrate, extra potash consistently increased the mean quantity of sugar per flower but with the high level of nitrate it consistently decreased it. The phosphate level had no significant or consistent influence on nectar yield.

Treatments increasing nectar production tended (a) to decrease stem weight and total number of flowers; (b) to retard flower production, probably as a consequence of relatively slower growth; (c) to increase petal length, and (d) to increase the proportion of plants with orange or red pigment in the withering leaves.

4. Buckwheat. Nectar was obtained significantly more frequently from those plants which had received extra nitrate and extra potash. It is suggested that the nitrate effect was due primarily to the senescent condition at the time of sampling of some of the plants with the lower dose, especially those which also had the high level of phosphate, and to the interactions of nitrate with phosphate and potash in respect to nectar production. Such explanations do not account for the effect of extra potash. Extra nitrate and potash always increased the stem weight and number of flower sprays; phosphate had little effect.

1. The1951 clover experiment. No significant effects on the mean yield of nectar were obtained, but the higher dose of phosphate significantly increased the frequency of zero samples during August, the main flowering and sampling period; so also did the higher dose of potash in the presence of high nitrate. In general those treatments which depressed nectar secretion resulted in a larger proportion of flowers opening before mid-August. Accelerated flower production appeared to result from more rapid growth during August.

2. The 1952 clover experiment. The treatment effects on quantity of sugar per floret were compared with those on final stem weight. Treatment effects on sugar/floret on particular sampling occasions were compared with the effects on relative ‘growth rate’ during the preceding period. Additional phosphate always resulted in greater and more rapid growth, but it only reduced the nectar yield in the presence of the highest level of potash. In the presence of low doses of potash nectar secretion was consistently poor. Additional potash did not increase the nectar yield if it resulted in greater or more rapid growth; if it did not affect size or growth rate it increased the nectar yield. Clonal differences in nectar production were greater than treatment ones.

3. The responses of the four species used in this series of experiments are compared. The results of other workers on the effects of fertilizer treatments on nectar production are discussed in relation to those reported here. If the balance between different fertilizers and their effects on growth are considered, as well as nectar yields, contradictions between the results of various workers can be explained. It is suggested that when potash tends to limit growth nectar secretion is likely to be consistently poor, but that when growth tends to be limited by nitrogen or phosphate a relative surplus of potash will promote good secretion.

Reference is made to work on the relation of the sugar supply in plants to nectar secretion and on the relation of fertilizers to the sugar supply. Tentative recommendations are made which require confirmation in field tests.

A total of fifty buffaloes, thirty-five Shorthorn and Shorthorn grades and twenty-nine Egyptian (Baladi) cows of different ages were used to study the thermal reaction mechanism by exposing the animals to direct solar radiation followed by shade. The thickness of the skin was also measured in all animals as it is one of the main factors in heat regulation. The results were as follows:

1. There were species and breed differences in the thermal reactions. Buffaloes were more hyperthermic when exposed to direct solar radiation than either Shorthorn or Egyptian cattle. The Shorthorns were more affected by ambient heat than Egyptian cattle.

2. The skin thickness of the buffalo was double that of the cattle. In all animals the thickness of the skin increased with age.

3. It is suggested that the adaptability of farm animals to tropical and subtropical zones is better assessed under shade and under normal husbandry conditions than by exposing them to direct sunlight.

1. The seasonal variation of farm sales of milk was measured for each year from 1937– 8 to 1951– 2 for England and Wales, and for each of the eleven marketing regions into which the country is divided.

2. The effect of changes between years in the amount of seasonal variation in milk values on the amount of seasonal variation in sales was examined and little direct connexion found.

3. Despite the fact that high milk prices in winter do not make production at that time more profitable, farmers get their cows to calve when prices are rising or are at their highest.

4. An inverse correlation was found between the number of calves born alive and sales of milk in the same month, but a positive correlation between the total number of cows in milk and the volume of sales in the same month.

5. That part of seasonal variation in sales which cannot be explained by variations in the number of animals in milk was shown to be mainly due to variations in the shape of lactation curves of animals calving in different months.

6. The importance of feeding, particularly the availability and condition of grass, in affecting the shape of the lactation curve is discussed.

Investigations have been carried out in this department in recent years with the object of establishing the minimum protein requirements of the bacon pig. The results were recently summarized in this Journal (Woodman & Evans, 1948). The minimum protein standards recorded in that communication are consistent with the attainment of the maximum rate of growth compatible with the net energy content of the diet. The basal foods employed consisted throughout of 2 parts of barley meal and 1 part of middlings (fine bran), together with a little lucerne meal and minerals. Briefly, it was found that such a diet, when supplemented with 7% of white-fish meal, supplied the minimum amount of digestible protein required for the quickest possible rate of growth between weaning and 90 lb. live weight, when the level of feeding was such as is shown in the feeding chart (see Table 7). It was also found unnecessary to include any protein concentrate in the diet beyond 90 lb. live weight to ensure the maximum rate of growth over this later period. The requirements were based on the results of statistically designed growth trials, and were confirmed by nitrogen-balance determinations carried out in metabolism crates. It was found that nitrogen retention was just as favourable on the basal diet supplemented with 7% of white-fish meal as when the protein level was increased by feeding higher amounts offish meal.