1. Two series of half-brother-sister lambs of balanced sexes have been reared on widely different (High and Low) planes of nutrition from the end of the third month of foetal life to 41 weeks of age. The effect of this on the growth in live weight and relative development of the body proportions has been studied.

2. The feeding of the mothers of the experimental lambs during the last 2 months of pregnancy was such that the High-Plane mothers gained 39·5 lb. live weight during pregnancy as compared with a gain of 1 lb. only in the Low-Plane group. The single lambs from both groups were of equal weight at birth, while on the average each individual twin was 47% heavier in the High-Plane than in the Low-Plane group.

3. In post-natal life the High-Plane lambs were fed so as to allow them to grow at their maximum rate and the feeding of the Low-Plane ones was controlled so as to allow them to grow at a slow but uniform rate. Lambs from both groups were killed at birth, at 9 weeks old and at 41 weeks old. At 9 weeks old the Low-Plane lambs killed had an average live weight of 14·3 lb. and the High-Plane ones 61·5 lb.; at 41 weeks old the respective weights were 69·5 and 180 lb.

4. The study of the age changes in the High-Plane lambs further proved the theory put forward by Hammond (1932) that in the sheep in post-natal life the different anatomical regions and tissues of the body grow differentially and in a definite order of development. The dressed carcass is later maturing than the organs and offal parts as a whole.

5. Of all the organs in the body the brain is the earliest developing, followed closely by the eyes. The thoracic organs as a whole are earlier maturing than the abdominal organs. Of the former, the thyroids, lungs and trachea and the heart are the earliest maturing in that order, while the thymus glands are later maturing. Of the alimentary tract, the oesophagus and the abomasum are the earliest developing parts, while the rumen and reticulum are much later maturing, growing at nearly twice the rate of muscle in the carcass from birth to 41 weeks. Of the other abdominal organs, the kidneys are earliest maturing, growing at approximately similar rate as the lungs and trachea, and slower than the heart in post-natal life. The abdominal fats are the latest maturing of all the organs, and of these kidney fat is the earliest maturing and the caul fat the latest.

6. The marked heterogonic growth of the organs appears to be related to their function. Those organs of most vital function to the life of the animal like the brain, eyes, lungs, kidneys, heart, oesophagus, abomasum and small intestines, are relatively well developed at birth, and consequently grow proportionately less in post-natal life than organs like the rumen and reticulum, which have an unimportant function until after the lamb begins to consume fibrous foods, or those whose function is largely that of storage of nutrients, which develop mainly in the later stages of growth.

7. The development of the different joints or body regions exhibits a marked gradient of increasing growth rate from the head and feet to the loin region, the feet and head growing least and the loin most in post-natal life, while the legs, neck and shoulders are in an intermediate position, the legs being earlier maturing than the shoulders.

8. The major tissues of the body exhibit marked differential growth rates in post-natal life. The order of increasing growth rate with age follows an outward trend from the central nervous system to bone, tendon, muscle, intermuscular fat and subcutaneous fat. Consequently, the early maturing nervous tissue and the skeleton make a greater proportion of their growth earlier in life than does muscle and fat; the latter, particularly subcutaneous fat, does not develop to any great extent until late in the growing period.

9. Within any of the major tissues, bone, muscle and fat, well-defined growth gradients are observed. Within the skeleton, in post-natal life, waves of increasing growth intensity pass from centres of early (even foetal) maximum rate of growth near the extremities, towards the central region of the body. As regards the axial skeleton, the skull, or rather the cranium, is the earliest part to develop, and from it waves of increasing growth intensity pass backwards to the lumbar region and downwards to the nose and lower jaw. In each limb, similar growth waves pass with age from the early developing metacarpals and metatarsals (cannon bones) down to the distal bones and up towards the lumbar region of the body, the pelvis and scapula being later developing than the femur and the humerus. The ribs appear to be the latest developing bones of the body, while the sternum situated further down in the body, though late maturing, is, however, earlier maturing than the scapula and the ribs. The bones of the fore-limb appear somewhat later maturing than those of the hind-limb.

10. As regards growth in length and thickness of the long bones of the limbs, a similar wave of increasing growth intensity passes from the cannons up the limbs. The upper bones increase relatively more both in length and thickness than the cannons after birth, and growth rate in length is at its maximum at an earlier age than growth rate in thickness.

11. In the case of muscle and fat, gradients have been demonstrated in their order of development from the head and neck backwards, and from the lower parts of the limbs (arms and legs) upwards to the loin region.

12. Changes in carcass measurements are of the same order as the changes in weight and/or shape of the tissues and parts measured, thus confirming their values as indices of carcass composition as well as conformation.

13. Marked differences between the sexes are apparent. The High-Plane males were on the average 15% heavier at birth than the females, which was found to be significant at the 5% level. At 41 weeks the wethers weighed 215·5 lb. and the ewes only 144·75 lb. This great difference appears to be principally caused by a longer span of growth in the wethers and by their higher rate of growth during the latter part of the growing period, rather than being due to their higher birth weight, for the females grow at a faster rate immediately after birth, and at 2 weeks of age have reached a greater average live weight than the males.

14. At 9 weeks of age the ewes were in a more advanced stage of development in respect of all characteristics than the wethers. The latter were proportionally less developed in all the late maturing characters such as dressed carcass percentage, had less fat and more bone, and each tissue was proportionately less developed in the late maturing joints in the wethers than in the ewes.

15. At 41 weeks the picture was completely reversed in every respect. The wethers at that age had not only reached 50% greater weight than the ewes but all their tissues and body proportions were in a more advanced stage of development, i.e. the later maturing tissues and anatomical regions were proportionately better developed in the wethers than in the ewes. At both ages these differences were reflected in photographs of the carcasses and the limb bones as well as in the carcass measurements.

16. The vastly different quantitative planes of nutrition of the High- and the Low-Plane lambs did not affect all the parts and tissues of the body equally, so that the Low-Plane lambs were not miniature images of the High-Plane lambs at the same age. On the contrary, the restricted nutrition of the Low- Plane lambs affected the different anatomical regions, organs and tissues of the body differentially and in an orderly manner. With but few minor exceptions, the different organs, tissues and anatomical regions of the body have been retarded in development by the restricted nutrition, in the direct order of their growth intensity. At any stage, an organ, part or tissue of high natural growth intensity at that stage was proportionately more retarded in development than organs, parts or tissues of lower growth intensity at that age. Over the whole experimental period the later developing parts or tissues were proportionately more affected than the earlier developing ones, which can only be explained in the same way as McMeekan (1940,1941) did in the pig, that the earlier maturing parts or tissues have a priority claim for the limited nutrients available in the blood stream when the growing animal is insufficiently fed to provide all parts or tissues of the body with an adequate nutritive supply for normal (maximum) growth. This holds at any stage of development, but at birth the differential effects of the restricted nutrition were much less pronounced than at 9 and 41 weeks.

17. The dressed carcass is more affected by the restricted nutrition in post-natal life than the organs and offal parts with the exception of the abdominal fats.

18. Of all the organs, the earliest developing brain and eyes are least affected in the Low-Plane lambs. At 41 weeks the brain is only 5% heavier in the Highthan the Low-Plane lambs, which is statistically insignificant for the available degrees of freedom; as the difference was proportionately greater at birth, poor nutrition in post-natal life appears to have no effect on the brain weight, while it may do so to some extent in foetal life. The ewes have a significantly lighter brain than the wethers (corresponding to their smaller live weight at birth). The eyes, though but slightly affected compared with other organs and body parts, are significantly lighter in the Low-Plane series at 41 weeks.

19. The restricted nutrition in foetal life did not have any effect on the weight of the lungs at birth and but little on the weight of the heart, while it greatly depressed the development of the thymus glands and that of the oesophagus, abomasum, spleen and somewhat less that of the liver, pancreas and kidneys. The development of the digestive tract and the abdominal organs was more retarded than that of the thoracic organs at birth in the Low-Plane lambs. In post-natal life the earlier maturing organs are in general less affected by the restricted nutrition than the later developing ones, the only important exception being the alimentary tract, which though growing at a relatively faster rate in post-natal life than the thoracic organs as a group, is less depressed by the low level of nutrition.

20. An organ of great growth intensity at any particular age interval is much more affected by the restricted nutrition during that interval than at other ages, i.e. the abomasum before birth, the rumen and the thymus glands from birth to 9 weeks, and the caul and kidney fat from 9 to 41 weeks old.

21. At birth the restricted nutrition in foetal life has had but small effect on proportional development of the different body regions. The head, however, is least and the legs most affected. In post-natal life the various joints are affected by the poor nutrition to a very different extent, and at each age interval they are, with minor exceptions, affected in the direct order of their growth intensity. At 41 weeks the head is 1·6 and the feet 1·8 times as compared with the thorax 4 and loin 4·4 times heavier in the High- than the Low-Plane lambs.

22. At birth the major tissues of the carcass are differentially affected by the restricted nutrition, the brain being least affected followed by the skeleton, muscle, tendon and fat. In post-natal life these tissues are affected in the order of increasing growth intensity, with age; the brain is least affected, followed by the skeleton, muscle, intermuscular fat, kidney fat and subcutaneous fat.

23. Restricted nutrition produces also differential effects on the relative development of the different anatomical units within each of the three major tissues, bone, muscle and fat. As regards the skeleton, individual bones or skeletal parts are retarded in development in direct relation to their growth intensity at each age interval. At birth the earliest maturing bones, i.e. those with high growth rate in foetal life, are relatively less developed than the other bones in the Low-Plane lambs, while at later ages the development of the late maturing bones is proportionately much more affected.

24. Not only does the plane of nutrition affect the weight of the individual skeletal units differentially, but it also affects the form of the bones in a comparable way. The late developing growth in thickness is retarded by poor nutrition to a much greater extent than the earlier developing length growth in postnatal life, while in foetal life the length growth of the early maturing cannon is more affected than its late maturing growth in thickness, the latter having very low growth intensity in foetal life as compared with the length growth. The differential effect on the form of the metacarpals over the whole experimental period is so great that those of the Low-Plane lambs at 41 weeks resemble bones of semi-wild or unimproved late maturing breeds, being very thin and round, while the cannon bones of the High-Plane lambs at 9 weeks and much more so at 41 weeks, have the thick flattened shaft characteristic of early maturing improved breeds.

25. The effect of the Low Plane of nutrition on the development of muscle, intermuscular fat and subcutaneous fat, as in the skeleton, exhibits a gradient from the early to the late maturing regions of the body in each case, i.e. the latest maturing parts are most and the earliest developing least affected.

26. Marbling or intermuscular fat as measured by chemical analysis of a sample of the longissimus dorsi muscle is affected by the Low Plane of nutrition to a greater extent than intermuscular fat, but less than subcutaneous fat. The plane of nutrition also affects the water content of the muscle, it being 3% higher at 9 weeks and 2% higher at 41 weeks in the Lowthan the High-Plane lambs.

27. The resultant effects of the plane of nutrition upon the body conformation and composition in terms of its major tissues is clearly reflected by the various carcass measurements taken.

28. The wethers appear to be more sensitive to restricted nutrition than the ewes and more so in the late maturing tissues and anatomical regions of the body. The proportionately more advanced development of the High-Plane wethers at 41 weeks as compared with the ewes is more than completely suppressed by the restricted nutrition of the Low-Plane wethers, the latter being in a less advanced stage of development than the ewes of the same treatment group at the same age.

29. Though an animal which has been retarded in its development by restricted nutrition retains more of the juvenile form than another of the same age which has been growing to its full inherent capacity, it is, however, not merely anatomically younger, corresponding to the weight difference, because of the differential effects of the restricted nutrition on the different organs, parts and tissues of the body. That even within a tissue some parts are penalized proportionately more than others by restricted nutrition during a period of active growth, has been tested statistically in the skeleton and found to be true.

30. Practical applications of some of the results are discussed.

A knowledge of the exact length of the breeding season for improved breeds under different environmental conditions in this country is lacking. Such knowledge is of importance so that the lambing season can be arranged according to farm conditions. Such knowledge, apart from providing the necessary background for the successful application of artificial insemination and administration of hormones, helps to explain certain problems of infertility. By selection it should be possible to build up strains, by extending the breeding season at one or both ends, so as to get lambing at any required time. As the results below show, crossbreeding and selection could lead to early sexual maturity, prolonged breeding season or restricted lactation anoestrus, which would undoubtedly increase the reproductive potentiality of the ewe.

The present method of estimating preliminary results in artificial insemination practice bears a definite relation to calving percentages, and, with few exceptions, may be generally adopted as a true measure of fertility.

Single factors, such as an individual bull with a low conception rate, a new and less efficient inseminator, or variations in the results obtained at the Sub-Centres, etc., do not noticeably affect the average monthly conception rate in a large A.I. Centre. The most important influencing factors have been found to be the choice of diluent, and in some cases the elimination of the use of stored semen.

No significant variation in fertility occurs with the season of the year, the age of the bull or the area of operation; but, for a bull to work satisfactorily at a centre and at the same time achieve good results, it is necessary that he should be treated as an individual and his psychology closely studied.

In view of results obtained, one is able to conclude that methods of evaluation at present in use (estimating initial motility, density, percentage of abnormals and a test of viability by storage of diluted and undiluted samples) are up to a point satisfactory.

A dilutor or buffer may influence the conception rate considerably, and it is felt that the diluent in use at present has its own fertility level.

With the Centre's team of forty-eight bulls it is obvious that there must be some variation in fertility levels between individuals; but it is seen that, whereas bulls in natural service fall obviously into categories of ‘high fertility’ or ‘low fertility’, this division tends to disappear in A.I. with the application of the various techniques.

During the course of three breeding seasons, daily observations of oestrus were undertaken on the following groups of ewes, all of which were running with ochred rams. One hundred and twenty ewes (pure bred and first-cross) of different breeds and ages, running with vasectomized rams under natural conditions. Twenty-eight grade Suffolk ewes fed on a submaintenance diet. Eighteen grade Suffolk ewes running with a fertile ram. Twenty ewes of several breeds exposed to artificial light.

The effects of heredity (breed and individual), environment (season, year and nutrition), age and artificial light on the breeding season and related phenomena have been investigated. The results and conclusions were as follows:

1. (a) There are breed differences in the extent of the breeding season, cycle length, incidence of silent heat and duration of heat (Table 29). (b) The duration of the breeding season is related to the geographical origin (latitude and altitude) of the breed, (c) The duration of the breeding season of the first-cross is intermediate between that of the two parents, (d) Individual differences in the number of oestrous cycles per ewe per season were more marked in the mountain breeds.

2. (a) Of the ewe lambs, 79% exhibited oestrus during the shortest days only of the first breeding season. Their breeding season is not spread evenly about the shortest day as it is with adults. (b) The occurrence and length of the breeding season in ewe lambs is associated with early birth dates or with higher growth rates.

3. (a) Significant differences exist between breeds in the age at first oestrus. (b) Ewe lambs born early in the season showed their first oestrus at later age and heavier weight than those born late.

4. Annual differences in the duration of the breeding season, cycle length, incidence of silent heat and occurrence of first oestrus were negligible.

5. (a) Submaintenance diet had no effect on the onset of the breeding season, but it converted oestrus into silent heat. Conception occurred less frequently after periods of underfeeding. (b) At high latitudes nutrition has only a minor effect on the breeding season of the ewe.

6. (a) A constant high ratio of artificial darkness (8 hr. light: 16 hr. darkness) hastened the onset of the breeding season some 57 and 27 days in the two experimental groups. (b) A constant high ratio of artificial light (16 hr. light: 8 hr. darkness) hastened the end of the breeding season some 104 days on an average (in one experimental group), (c) There were breed differences in the latency of initiation and of cessation of the induced breeding season, (d) In the induced breeding season cycles of ovulation preceded the first oestrus, (e) Two thresholds of pituitary activity are suggested, one for the onset of ovulation, and the other for the manifestation of oestrus.

7. (a) A high frequency of cycles outside the normal range (14–19 days) was observed in the mountain breeds and in ewe lambs. (b) The shortest average cycle length coincided with the shortest days of the year.

8. A high frequency of silent heats (during the breeding season) was observed in the mountain breeds, in ewe lambs and during the second half of the breeding season.

9. Oestrus was of longer duration in adults and yearlings than in ewe lambs.

10. (a) Post-partum heat occurred in 56% of Suffolk ewes with an average lactation anoestrus of 35 days. (b) There is a relationship between the early onset of the breeding season and the incidence of post-partum heat, (c) Conception post-partum is partly inhibited by lactation.

11. Mating behaviour was observed in animals of several breeds and ages (three patterns were recorded for ewes and eight patterns for rams).

12. Irregular columnar cells in the vaginal smear of the ewe characterized late pregnancy.

In addition, the breeding season of wild and domestic sheep was reviewed in relation to the environment with special reference to the length of daylight.

1. Four groups of half-brother-sister lambs of eight individuals, each of balanced sexes, have been reared on quantitatively different planes of nutrition so as to grow along predetermined growth curves until they reached 30 lb. dressed carcass weight when killed. Treatment differences started at the end of the third month of foetal life. One group was reared on a High Plane of nutrition throughout (High – High), another on a High Plane up to 6 weeks of post-natal life followed by a Low Plane (High-Low), the third on a Low Plane up to 6 weeks after birth, followed by a High Plane (Low-High), and the fourth on a Low Plane throughout (Low-Low). The High-High lambs were killed at 9 weeks old, the High-Low and Low-High at 15 weeks and the Low-Low at 41 weeks old. This allowed for comparison of animals of the same carcass weight but different age and of animals of the same age and carcass weight, but having differently shaped growth curves. The relative effects of the treatments on the development of the body proportions and carcass quality have been studied.

2. The proportion of dressed carcass to organs and offals was highest (48·9% of live weight) in the High-High group, lowest (42·9%) in the Low-Low, and intermediate in the High-Low (45·6%) and Low-High (46·3%). Variation in carcass percentage due to sex was not significant, though 4·8% higher in the females than in the wethers of the High-High group.

3. The weight of the head is more affected by the age of the animal than by the plane of nutrition or the carcass weight, it being of the same weight in the Low-High and High-Low lambs, but significantly lighter in the High-High and significantly heavier in the Low-Low groups. The skin, with wool, was much heavier in the Low-Low than in the other groups, while the weight of the blood was directly affected by the plane of nutrition prior to slaughter, it being significantly heavier in the High-High and Low-High groups than in the High-Low and Low-Low ones.

4. The development of the brain and the eyes was found to be primarily a function of age, these organs being lightest in the High-High and heaviest in the Low-Low group. The brain (as in Part I) appeared to be earlier maturing than the eyes, the differences between the age groups all being significant in the case of the latter, but only the High-High lambs had significantly lighter brain than the other groups.

5. Marked differential effects due to the plane of nutrition and/or age on some of the internal organs were observed, though others like the heart appear to be a function of body weight, being equally well developed in all treatment groups.

6. Organs like the thymus glands, the liver, the spleen, the kidneys and the small intestines are for their development, like the blood, found to be more dependent on the level of nutrition at the time of slaughter than on age or carcass weight, being heavier in the High-High and the Low-High groups than in either the High-Low or the Low-Low. These differences are in most cases highly significant.

7. The development of organs like the oesophagus, the rumen, the reticulum, the omasum and the genital organs, appears to be more influenced by age than the plane of nutrition, while that of the abomasum, the caecum, the large intestines, the rectum and the pancreas is influenced by the plane of nutrition as well as age.

8. Apart from the urinogenital organs, the pancreas is the only organ which exhibits a significant difference due to sex, being 14% heavier in the males.

9. In general, the organs appear to have priority claim for the available nutrients in the blood stream to allow them to develop to such an extent, which enables them to cope with their function at any age. When the nutritive supply is low, organs, whose function is directly associated with growth, suffer proportionately more than those which are of primary importance for life, like the brain, the eyes and the heart.

10. The four treatments produced two distinct types of carcasses. The High-High and the Low-High carcasses were of very similar conformation, short in the leg, blocky and well covered with subcutaneous fat, with the late maturing trunk joints proportionately better developed compared with the HighLow and Low-Low carcasses, which in conformation resembled each other, and were leggy, lank and badly covered with subcutaneous fat. In the latter two groups the early developing legs and neck were proportionately better developed than the later maturing trunk joints.

11. Marked differential effects were produced on the carcass composition. Bone in the dressed carcass was significantly lighter in the Low-Low than in the other groups, due to the inhibiting effects of continuous undernutrition on growth in thickness of bone. The difference in bone weight between the other groups was insignificant, though the High-Low had the heaviest bone in the carcass. Muscle was better developed in the High-Low and the Low-Low groups than in the Low-High and High-High groups, while fat, especially the subcutaneous fat, was better developed in the two latter groups.

12. A High Plane of nutrition prior to slaughter appears to be essential for good development of the latest maturing tissue, the subcutaneous fat. Under limited food supply the earlier maturing tissues, muscle and bone, especially for growth in length, have priority claim for the available nutrients.

13. The ewes had significantly lighter bone, slightly lighter muscle, though insignificantly so, and significantly heavier fat than the wethers.

14. As between the tissues, so within the anatomical units of each, marked differential effects were produced. Limited nutritive supply at any age causes greatest inhibiting effects on the tissues or those parts of any one tissue, which have the highest growth intensity at that age. Similarly, good nutrition at any age benefits most the parts of highest growth intensity at that time.

15. All tissues show great recuperative capacity if provided with adequate food supply after restricted nutrition, unless at that time they have passed their age of high growth intensity.

16. A Low Plane of nutrition from 6 to 15 weeks following high feeding, in the High-Low lambs, had the effect that not only was the subcutaneous fat, the tissue of highest growth intensity at that age, more retarded in development than the other earlier maturing tissues, but all the tissues were relatively more affected in the later maturing regions of the body than in the earlier maturing parts. On the contrary, a High Plane of nutrition from 6 to 15 weeks following severe undernutrition, in the Low-High lambs, resulted in proportionately better development of the subcutaneous fat than the other tissues, and within each tissue a proportionately better development in the late maturing regions of the body, as compared with the earlier developing parts. This is because of the relatively greater effect of the poor nutrition earlier on, on the parts of highest growth intensity during that period, and greater beneficial effects of the good nutrition afterwards on the parts which then had relatively higher growth intensity. Thus the bones of the leg (early maturing) were heavier in the High-Low than in the Low-High, while the ribs (late maturing) were heavier in the Low-High group. Muscle in the Low-High was heavier in the loin but lighter in the limbs and neck than in the High-Low, and the difference in fat in favour of the Low-High was much greater in the trunk joints than in the limbs, while the High-Low had even more fat in the neck.

17. Comparison of the development of the different anatomical units of the major tissues in the High-High and Low-Low carcasses showed that within each tissue the latest maturing parts suffered proportionately more from the continuous undernutrition, with the exception of the ribs, which, though the latest maturing part of the skeleton, were of the same weight in the Low-Low as the High-High, though total bone in the carcass was heavier in the latter. This is accounted for by the so late onset of high growth intensity in the ribs that the High-High lambs were killed before the ribs could benefit from the good nutrition as much as earlier maturing parts of the skeleton, while in the Low-Low, the ribs, having high growth intensity for a long time after the growth rate of earlier developing parts of the skeleton had declined, could compete for nutrients with considerable success with still later maturing tissues, muscle and fat.

18. In the skeleton the shape of individual bones was much more affected by the different treatments than their weight. This accounted for the great treatment differences in carcass conformation. The earlier maturing growth in length is much less affected than the later maturing growth in thickness, and the earlier maturing bones like the cannons are less affected than the later maturing femur or the pelvis.

19. The percentage of marbling fat in the longissimus dorsi muscle appeared to be more dependent on age of the animal than on the plane of nutrition or the state of fatness of the animal, being lowest in the High-High and highest in the Low-Low carcasses.

20. The iodine number of the marbling fat was also found to be more affected by the age of the animal than by the state of fatness or the plane of nutrition, it being highest in the High-High and lowest in the Low-Low carcasses.

21. The water content of the muscle was highest 78%) in the High-High lambs, but lowest in the Low-Low ones (74·9%).

22. The four treatments caused great and highly significant differential effects on the various carcass measurements. As some of these measurements have been found by previous workers to be even more important indices of meat quality than is the actual composition of the carcass, it may be claimed that the different treatments have affected carcass quality even more than carcass composition.

23. The treatment differences were proportionately much smaller in the external measurements, which are primarily indices of skeletal development, than in the internal muscle measurements and by far greatest in the fat measurements.

24. External measurements which should be small for desirable conformation like the leg length, F, the tibia plus tarsus, T, and the length of the cannon, M, were significantly greater in the Low-Low and the High-Low than in the other groups, being smallest in the High-High.

25. The most important muscle measurements, such as the depth of the eye muscle, B, and the shape index, B/A × 100, were best developed in the High-High, followed in a downward order by Low-High, High-Low and Low-Low groups.

26. The fat measurements were much better developed in the High-High and the Low-High groups than in the Low-Low and the High-Low ones.

27. The females had significantly better developed fat measurement than the wethers, while no significant sex differences were observed in the other measurements.

28. Considering the several factors studied which affect carcass quality, the High-High lambs yielded carcasses of the best quality, especially the females, closely followed by the Low-High ones, while the Low-Low carcasses were of much inferior quality and the High-Low still poorer. Those of the latter two groups were more typical of an unimproved late maturing breed than being of the same breed as the High-High and Low-High carcasses.

The mean body weights and standard deviations of body weights at monthly intervals of female Jersey and Friesian cattle on the Massey Agricultural College and Dairy Research Institute farms at Palmerston North, New Zealand, are presented in graphs.

A summary of some of these mean weights is presented in the following table:

1. A survey of bean crops was carried out in the Oxford area in the years 1947–9 with the object of studying farmers' methods, and the factors affecting establishment and development of the crop in the field.

2. The season and the fertility status of the soil have a profound influence on the development of the crop, while plant density affects the growth of the individual plant.

3. Hard winters cause crop losses which may amount to more than 50% of the plants. Mortality continues throughout the season.

4. A warm dry spring and an equable summer temperature favour pod production more than hot, dry seasons.

5. High plant densities cause: (1) a reduced rate of pod formation on each plant over a wide range of conditions, but a greater reduction on poor land than under good conditions; (2) a reduction in stem formation on low fertility fields (but not on high fertility land); (3) a significant increase in pod production per acre on high quality fields.

6. A high level of fertility leads to significantly more pods/acre, owing to better plant survival and increased branching and podding.

7. Under conditions favouring vegetative growth, there appears to be some competition between stem production and pod production, for the correlation between stems/plant and pods/plant found on low fertility land and in dry seasons no longer holds under good growing conditions.

8. In an average crop, there is a very serious loss of flowers and partly matured pods, which may amount to 85% of the flowers formed.

9. This wastage may be due to (1) unsatisfactory pollination or self-infertility, (2) inadequate availability of certain plant nutrients, (3) unsuitable environmental conditions, particularly low light intensity in dense crops.

10. Botrytis cinerea can cause a high wastage of crop, but it did not figure prominently during the 3 years of the survey, and appeared to be associated with deficiency of potash and/or phosphate in the only two severe outbreaks that occurred.

Permanent buildings of a variety of designs have been in widespread use for many years as potato stores on the Continent of Europe and in the United States of America. (For a summary of recent literature, with references, see Rose & Cook, 1949.) There are examples of buildings being used as potato stores in this country (e.g. Keith, 1941), but the bulk of the crop is stored in clamps. Because the climates of the U.S.A. and the Continent of Europe differ markedly from that of Great Britain, it is not possible to use the types of store developed in those regions as models for British stores. Over much North America and the Continent of Europe the stores are designed to withstand severe winter frosts, and the main problem is to keep the temperature of the tubers high enough to prevent freezing, the metabolic heat being readily removed if necessary by a small amount of controlled ventilation. Under British conditions the mean daily temperature for most of the storage season, above the optimum for potato storage (40·42° F.), and therefore the main problem is that of keeping the tubers cool. This could, of course, be achieved by using a cold store, but cold storage is considered too expensive. To design a store, information is required about the temperatures attained by stacks of potatoes at different times of the year, the effectiveness ventilation in controlling the temperature, the relation of temperature in different parts of the stack to dimensions of the stack, and to the insulation both of the bin and of the building. To obtain this data a programme of work was initiated, and the results of the first year's work in a building of very low insulating capacity are described in this paper. The climatic conditions during this year, i.e. 1946–7, were very abnormal, a very cold winter followed by a hot spell in the spring which provided an abnormally severe test of an uninsulated store. Later papers will consider storage in an insulated building with adequate ventilation.

In three groups of field experiments totalling fiftysix observations phosphate responses were found to be very significantly and inversely related both to the percentage saturation of the b.e.c. and exchangeable calcium as a percentage of exchangeable calcium plus hydrogen. The availability of the native soil phosphate was significantly and directly related to these values. The relationships between phosphate response or availability and the amounts of acid-soluble, adsorbed and water-soluble phosphate in the soils were much less conclusive.

In acid soils considerable amounts of phosphate can be retained in a plant-available form associated with exchangeable bases, mainly calcium. Since practically all the soils from the field experiments lay within the range pH 4·7–6·3, it is believed that this form of phosphate is operative in these soils. The presence of such phosphate in the soil is, however, a function of the degree of base saturation in so far as this governs (probably through its influence on soil pH) the equilibrium distribution of the native soil phosphate between the available base-linked (saloid-bound) form and the less available colloid-bound form. With decreasing pH and base saturation increasing amounts of colloid-bound phosphate are formed at the expense of the saloid-bound phosphate. The degree of base saturation is therefore directly related to phosphate availability and, consequently, inversely related to phosphate response.

In view of the significant regressions obtained, and the association of the exchangeable bases with a specific form of available phosphate, it is suggested that until methods are worked out for determining the amount of saloid-bound phosphate exchangeable base data may be used for assessing phosphato availability and response in acid soils. This method is contrasted with the more conventional methods of determining acid-soluble and adsorbed phosphates which are not always specific regarding tho form of phosphate extracted and the values for which, since they may represent the sum of a number of forms of different availabilities, aro difficult to interpret.

To amplify published information on the size of errors in annual egg records, results are presented for fourteen laying experiments and one flock under uniform management at the Agricultural Research Institute of Northern Ireland, Hillsborough. It is concluded that in laying experiments on a semi-intensive plant the egg records are seldom affected to any serious extent by differences between pens that are treated similarly. Non-random allocation of pullets to the laying pens does not appear to have seriously affected the results on which this conclusion is based. It is pointed out that the distribution of egg records from a high producing flock is likely to be extremely skew and leptokurtic.

1. Histochemical tests have been applied to the socalled sweat glands and their secretions of Zebu and Ayrshire cattle, the former to only a limited extent.

2. For skin specimens of Ayrshire cattle positive reactions were obtained for ribonucleoprotein, arginine and alkaline phosphatase. Negative reactions were obtained for desoxyribonucleoprotein and acid glycerophosphatase.

3. Neither the sweat glands of Ayrshire cattle nor those of Zebu cattle gave positive reactions for fats, lipids or cholesterol and its esters, although these were all present in the sebaceous glands of both breeds. Detectable amounts of phospholipid were not found in the sweat glands of the Ayrshire cattle and their secretions.

4. The chemical composition of the secretion of bovine sweat glands differs markedly from that of human eccrine or apocrine sweat glands in not containing detectable amounts of glycogen, lipids and associated compounds or iron.

1. Spindle-shaped myoepithelial cells with longitudinal myofibrils have been demonstrated in the sweat glands of Ayrshire and Zebu cattle.

2. The cells in both breeds are similar in structure, location and arrangement.

3. Under the polarizing microscope they are birefringent as is characteristic of other fibrillar structures.

It is assumed that maximum growth requires maximum transpiration, and that maximum transpiration can be maintained by keeping the soil near to field capacity throughout the growing season. Transpiration rates can be calculated from weather data (the basic principles are outlined and an example of the calculation given), and the paper describes four field experiments in which attempts were made to control the water content of the soil throughout the growing season, by irrigation from overhead spray-lines.

In spite of differences in season and soil, the four sets of data are consistent in showing that maximum sugar yield is obtained when the soil-moisture deficit (amount of rain or irrigation needed restore the soil to field capacity) does not exceed about 2 in. in mid-July, or about 4 in. in mid-September.

Four soils, sterilized by steam at 100° C, with unsteamed controls for three soils, were examined at intervals up to 62 days to study the microbiology in relation to the abundance of ammonia, nitrites and nitrates of all the soils, the C/N ratios of two, and the pH and moisture content of three. After steaming, the soils were flooded with sterilized tap water equivalent in amount to 3 in. of rainfall at intervals varying with the particular soil. The soil of the first trial remained under water until very near the end of the experiment. In all the soils, the production of ammonia up to 14 days after steaming was associated with increased biological activity, generally a multiplication of bacteria associated with multiplication of Protozoa. The production of nitrites and nitrates was associated with a similar biological activity. Those bacteria that survived steaming had simple growth requirements as compared with those of the subsequent microflora. The Protozoa showed a series of ‘pulses’ of maximum and minimum abundance and there was also a succession of species in all the soils. A predilection of Protozoa for certain bacteria was shown by the association of certain species with particular groups of bacteria identified by Gram's staining. In two of the soils, there were ‘pulses’ of maximum and minimum abundance of diatoms, and in one soil diatoms possibly affected soil texture. The investigation showed that despite the contrasting characters of the soils, the major chemical changes were almost wholly attributable to biological activity, and that after steaming the same general reactions occurred in all. The investigation proved the importance of considering the microbiology of steamed soils as a problem in ecology.

The effects, on induction and maintenance of oestrus and on pelt changes, were compared for various schedules of entirely artificial light of constant intensity.

A period of exposure to low environmental temperature was without effect on subsequent response to light treatment.

In one experiment, after periods on 6 hr. artificial light or on daylight, groups were put upon, daily, (i) 7 hr. light as 6 hr. + 5 hr. dark + 1 hr. light, (ii) the same total amount of light but divided as 6 hr. + 1 hr. separated by darkness increasing by 5 min. each day, and (iii) light increasing from 7 hr. by 5 min. daily. Groups (ii) and (iii) became oestrous together, later than group (i).

Subsequently all were placed on 7 hr. total light daily, applied in various ways. If given as a single continuous period daily, oestrus ended and moult into winter coat occurred. The latent period depended upon the treatment previously imposed. The duration of oestrus on treatment (i) was greater than normal.

In another experiment females were put on, daily, (iv) 24 hr. light, (v) 14 hr. light, and (vi) 4 hr. light as 2 hr. + 10 hr. dark + 2 hr. light. First response was seen on (vi), but on the average the quickest was on (v) and slowest on (iv). Thus darkness contributes to the induction of oestrus.

Possible interpretations are discussed.

1. The results are presented of a survey of early cut hays, by the tripod and ground-cured methods, from fifteen ryegrass swards and six ryegrass-clover swards in Northern Ireland.

2. The effect of date of cutting on quality is discussed.

3. The losses in conservation at two centres included in this survey are presented. Losses of 15·9 and 13·3% are recorded for the tripod method.

4. A trial designed to produce high-quality hays from specially managed swards by these two methods is described. The results obtained in relation to conservation losses and the digestibilities of these hays are considered. Field losses of dry matter ranged from 3 to 16·5% for the tripod method and 9–27% for the ground-cured. The tripod hays had starch equivalents of 47, 48·2 and 51·5; those of the corresponding ground-cured hays were 41·5, 38·2 and 51·8.

5. It is suggested that the tripod method as applied to swards of the type used in the second experiment offers a means of securing a high degree of conservation.

1. The chemical changes which take place in a urine patch have been studied using urine from wethers and to a small extent from cows.

2. The sizes of individual urine patches vary considerably, depending mainly on the volume of the urination. The average from wethers is about 45 sq.in.

3. The volume of urine per wether per day averages 2880 ml. with a nitrogen content of 0·92%, of which about 75% was in the form of urea; 4·1% as allantoin; 2·6% as hippuric acid; 1·5% as creatine-creatinine; and 12·4% as amino-nitrogen.

4. Improved herbage growth results in twice the area actually wetted with urine. The total area affected averaged 100 sq.in.

5. The probable area wetted with urine from cow urinations was about 650 sq.in. with a further 200 sq.in. affected indirectly.

6. With wethers the average rate of nitrogen application on a urine patch amounts to 432 lb. of nitrogen per acre.

7. The rate of hydrolysis of urea in laboratory experiments is affected by temperature and is increased by small amounts of hippuric acid but not by the other urinary constituents tried. The hydrolysis rate is greater at soil moisture content of 24% than at higher moisture levels.

8. Urea hydrolysis in soil (both in laboratory and in the field) is accompanied by pronounced increase in pH (up to pH 9·2 with urea equivalent to that applied to a urine patch).

9. The rate of nitrification is greatly affected by the pH changes. At pH values in excess of 8 nitrites accumulate and nitrate formation is retarded.

10. Heteroauxin and allantoin were both found to stimulate nitrification in laboratory experiments when used at levels found in urine. Other urinary constituents were without effect.

11. The hold up of urine on leaf surfaces of pastures was shown to amount to as much as 12·5% of the green weight of herbage.

12. Ammonia in considerable amounts may be lost to the air both from herbage and from soil.

13. Field experiments are in complete agreement with laboratory experiments and no essential difference of wether and cow urine was noticed.

14. The fate of the nitrogenous constituents is briefly considered and shown schematically.

1. In continuation of experiments made in 1949 (Holmes et al. 1950) an experiment was carried out from 7 May until 23 September 1950, to compare close-folding and rotational grazing of cows on pastures which were liberally treated with nitrogenous fertilizer. With close-folding the cows were moved daily to an area of fresh pasture calculated to supply the day's feed requirements; the rate of stocking for the day ranged from thirty to sixty-five cows per acre. With rotational grazing the cows were stocked on pasture at the rate of seven to eight cows per acre and moved from one pasture to the other at intervals of 3–4 days. Two uniform groups of six Ayrshire cows were used in a double reversal layout with four periods each of 5 weeks. The same pastures as in 1949—a permanent pasture and a cocksfoot ley—suitably divided by electric fences were used. No supplementary feeding was given.

2. The average yield per acre from close-folding was 241 cow-days, 732 gal. of milk and 320 lb. live-weight gain—equivalent to 632 lb. digestible crude protein and 4316 lb. starch equivalent. Rotational grazing on similar adjoining paddocks gave 181 cow-days, 557 gal. of milk and 285 lb. liveweight gain per acre, equivalent to 486 lb. digestible crude protein and 3371 lb. starch equivalent.

3. The average daily milk yield per cow was 29·5 lb. for one group and 30·2 lb. for the other. For close-folding it was 29·6 lb. and for rotational grazing it was 30·1 lb., none of the differences being significant. Nor were any differences in the average live weight of the groups or in their live-weight gains significant.

4. The increased production per acre from closefolding compared with rotational grazing—amounting to 20–40%—could be related to the increased efficiency with which the available pasture was consumed.

5. Close-folding had no harmful effect on the pastures. Although the season was exceptionally wet, poaching occurred only in the gates and alleyways. 6. The frequent applications of nitrogenous fertilizer throughout the season maintained regular production of good herbage. In June and July, however, despite the fertilizer applied, the crudeprotein content dropped on some paddocks to 13% of the dry matter, a figure barely sufficient to maintain high milk yields.

7. Comparison of the production per acre in 1950 with that in 1949 where close-folding was used, showed an increase of 34% in starch equivalent utilized on the permanent pasture. For each extra cwt. ‘Nitro-Chalk’ applied in 1950 over that in 1949, 190 lb. starch equivalent were produced. On the cocksfoot the response to additional nitrogen was reduced because of potash deficiency induced by cropping for grass-drying in 1948.

8. The factors affecting the increased production from close-folding and the fertilizer requirements of pasture are discussed.

An account is given of the relationship between the decrease in pH on incubation of bull semen and fertility. It is shown that, in general, a high pH change tends to be associated with a good conception rate and vice versa. There are, however, exceptions to this general correlation, and it is believed that the pH change test, while giving an indirect measure of sperm metabolism, does not provide the clue to the problem of fertilization.