The serum protein-bound iodine concentration in the blood of beef steers varied between animals and was not correlated with the daily gain during the fattening period. The data, however, are insufficient to arrive at a definite conclusion.

The average erythrocyte counts of the blood were 7·86 (range: 5·89–8·75), 8·59 (range: 6·55–10·15), and 8·54 (range: 5·23–9·62) million per mm.3 for steers of 14, 26 and 38 months of age. The difference between the counts of the yearlings and that of the other age groups was statistically significant. The red cell fraction increased with live weight over the range 700–1230 lb. Although a significant (P < 0·01) correlation was found between the number of erythrocytes in the blood and the daily gain of the steers, the erythrocyte count cannot be employed to predict the possible gaining ability of single beef animals.

The haemoglobin content of the blood was found to be 14·02 (range: 9·8–17·4) in the case of the yearlings, 14·68 (range: 11·8–18·5)and 14·61 (range: 7·95–16·85) g./100 ml. blood in the case of the 2-year-olds and 3-year-olds respectively. These differences between age groups were not significant.

A correlation of 0·31 was found between the haemoglobin content and live weight of steers within the weight range of 600–1230 lb. The data suggest that for every 100% increase in weight, the haemoglobin in the blood increased by 17%. No correlation was found between the haemoglobin content and the rate of gain of the steers.

The daily live-weight gain of beef steers was not correlated with the weight of the pituitary gland. In the case of the thyroid gland a significant correlation was found between the absolute weight of the gland and the rate of gain. No correlation, however, was found between the relative weight of the thyroid gland and the rate of gain of the steers.

A highly significant correlation was found between the weight of both the pituitary and thyroid glands and the live weight of the steers (r = 0·44 and r = 0·55 respectively), and the slope of the regression lines showed that the weight of the pituitary gland varied with the power of 0·34 of live weight (0·34% increase in the weight of the pituitary for every 1% increase in live weight) whilst the weight of the thyroid gland varied with the power of 0·89 of the live weight.

No correlation was found between the weight of the pituitary and thyroid glands. The average weight of the pituitary was 1·89, 2·11 and 2·19 g. and the average weight of the thyroid was 16·81, 20·24 and 22·65 g. for steers of 14, 26 and 38 months respectively. The average live weights of the steers in the age groups concerned were 791, 893 and 1071 lb. respectively.

1. An investigation has been carried out concerning the percentage of fat in the subcutaneous and intermuscular fatty tissues and in the muscular tissues, and the iodine number of the extracted fat from eight anatomical joints (foreshin, neck, shoulder, thorax, loin, pelvis, leg and hindshin) and from the perinephric fatty tissue and psoas muscles of the carcasses from twenty-four animals. The animals were from three breeds (Hereford, Dairy Shorthorn and Friesian) and were on four levels of nutrition—high-high and medium-high, and high-medium and medium-medium. The first two groups—finished on concentrates—were younger than the second two groups—finished on grass.

2. Using an analysis of variance for the resultant data for percentage of fat and iodine number, it was found that breed had affected the percentage of fat in the tissues of the various joints significantly—on the average the order was Shorthorn (highest), Hereford and Friesian (lowest). This result could be predicted from the fact that this was the order of fatness of the carcasses (as measured by the percentage of fatty tissue in the carcass—see Callow, 1961).

3. The data for iodine number showed no significant effect for breed in either the subcutaneous or intermuscular tissues. The significant effect of breed in the case of muscle could be attributed to significant differences in the overall level of fatness (see Callow, 1961) of the carcasses of the three breeds.

4. A good correlation existed between the average percentage of fat in a joint and the average iodine number of fat extracted when the data for various joints was used to calculate straight lines of best fit. (In the case of muscular tissue, it was necessary to use the inverse of the percentage of fat to calculate the average—because the relation between the percentage of fat in muscular tissue and its iodine number is a rectangular hyperbola.)

5. Using such lines of best fit, it was possible to show that certain joints had tissues which gave abnormal values for iodine number. Thus, deepseated tissues, like psoas muscle and kidney fat, had unexpectedly low values, whilst tissues from the hindshin had unexpectedly high values. This was attributed to the effect of local temperature—a high local temperature in the body giving a lower iodine number and a low temperature a higher iodine number than would otherwise be expected. The special case of subcutaneous fat from the thorax—with a higher iodine number than expected—is explained by the presence of brisket fat (which has a high iodine number).

6. The data were used graphically to show the effect of growth gradients, thus the average percentage of fat in all the tissues is lowest in fore- and hindshins and highest in thorax (muscular and intermuscular tissues) and in the pelvis (subcutaneous tissue). Similar effects, but in the reverse direction, were shown by average values for iodine numbers.

7. There were systematic differences in the percentage of fat in the subcutaneous and intermuscular tissues of joints and in the iodine number of the extracted fat. These too showed marked growth gradients. Although the percentage of fat in the intermuscular tissue was greater than that in the subcutaneous tissue in the fore- and hindshins, it was less in the thorax, loin, pelvis and leg. In spite of this, the iodine number of the subcutaneous fat was always higher than that of the intermuscular fat. This is attributed to the former being a colder tissue than the latter.

8. It was shown that the relation between iodine number and percentage of fat in the various joints was different for the animals finished on grass (highmoderate and moderate-moderate levels of nutrition) as compared with those finished on concentrates (high-high and moderate-high levels). This was attributed to the rate of fattening being greater in the second case and to this giving rise to lower iodine numbers.

9. Beyond this effect of rate of fattening, no reason could be found for the fact that the general level of iodine numbers showed variation from animal to animal.

10. The extreme variation in percentage of fat in the tissues was (a) muscular tissue from 1·3 to 14·5%, (b) intermuscular tissue from 29·5 to 82·7%, and (c) subcutaneous tissue from 25·2 to 89·8%. For iodine number the variation was (a) 50·0 to 73·9, (b) 42·9 to 67·9 and (c) 46·3 to 67·9 It is thus clear that beef can be a very variable foodstuff.

1. Changes in fleece structure produced by crossing the Wiltshire Horn and Scottish Blackface breeds of sheep have been analysed. Skin and fleece samples were available from lambs and adults of both parental breeds, and from the F1 F2 and back-cross genotypes. For the analysis, three types of fibre: kemps, hairs (both primaries) and secondary fibres were distinguished.

2. The frequency of kemp fibres was high in the Wiltshire and relatively low in the Blackface. The frequency of hair fibres was nil in the Wiltshire and fairly high in the Blackface. The crosses were intermediate between the parents. Despite these fibre type changes among the primary fibres there was no difference between the breeds or crosses in follicle population densities or in the relative proportions of primary and secondary follicles.

3. Kemp fibres were shorter and finer in the Wiltshire than in the Blackface. In the crosses they were intermediate. Hairs, when present in the crosses, were shorter and finer than in the Blackface. Secondary fibres were shorter in the Wiltshire than in the Blackface but in some of the crosses they were at least as long as in the Blackface. Wiltshire secondary fibres were remarkably coarse and strongly medullated and this notable characteristic was carried over to some extent in the crosses. Throughout the study comparison in these terms was always complicated by fibre shedding.

4. Fibre shedding was universal for all types of follicle in the Wiltshire. In the Blackface, primary central follicles appeared to shed their kemp fibres two or three times yearly. For hairs and secondary fibres shedding did not occur more than once per year and the frequency of shedding amongst these fibres was low. In the crosses the frequency of shedding in kemps and the incidence of shedding in hairs and secondaries were higher than in the Blackface. Increases in the incidence and frequency of shedding probably had some effect in decreasing the measurable fibre length in the crosses.

5. The mean length and diameters of the different fibre types were usually positively correlated within sheep. In this and other ways there was not much evidence of competition for fibre substrate between the different types of mature follicles, in this material.

6. Birth-coat classifications distinguished between the typically smooth Wiltshire and the hairy Blackface birth-coats. Birth-coats in the crosses were intermediate but showed partial dominance of the hairy type.

7. The most important of the observed changes in fibre and follicle morphology can be briefly summed up by considering how the Blackface phenotype was modified in the crosses by the introduction of the Wiltshire genotype, viz.

(a) The proportion of kemps was increased at the expense of hair fibres. This was brought about by kemp fibres tending to replace hairs in all primary central and in some primary lateral follicles.

(b) All primary fibres were diminished in length and thickness; secondary fibres increased in thickness. The general fibre population therefore became more uniform.

(c) The shedding frequency of kemps and the shedding incidence among hairs and secondaries were both increased.

(d) Follicle population density, follicle group structure and the S/P follicle ratio were unaltered.

(e) The degree to which changes occurred in the different crosses was generally proportional to the percentage of Wiltshire-derived genes present.

8. The fact that the relative frequencies of kemp and hair fibres could be altered without any concomitant changes in the follicle group pattern showed that a particular follicle type was not a priori bound to produce a particular fibre type. It seems clear therefore that the physiological activity of follicles can be altered genetically whilst their organization within the follicle group pattern remains invariant.

A study is made of 46 years' records of rainfall for each of the months April to September. Following the determination of the distribution of monthly rainfall recommendations are made as to the best method of specifying rainfall and of predicting the rainfall to be expected on the basis of previous observations.

1. Eight nitrogen metabolism experiments, each with sixteen steers representing grade Brahman, Brahman x Shorthorn, Africander x Hereford and Herefords, were carried out. The steers were fed according to body weight to the power 0·73, on rations consisting of natural pasture hay alone or in combination with lucerne hay.

2. These experiments showed that the steers with zebu blood were significantly superior to the Herefords with regard to dry-matter digestibility and apparent nitrogen digestibility. The breed difference disappeared when nitrogen digestibility was calculated from the relationship feed nitrogen minus undigested faecal residue nitrogen, divided by feed nitrogen.

3. Two further nitrogen metabolism experiments with six Africander x Hereford and four Hereford steers fed natural pasture hay plus lucerne hay, and one experiment with two Brahman x Shorthorn, two Africander x Hereford and two Hereford steers fed chaffed wheat straw were carried out. The steers were fed an equal amount of ration, irrespective of body weight.

4. In these three experiments faecal nitrogen was fractionated into undigested residue nitrogen, non-dialysable centrifugable nitrogen, non-dialysable non-centrifugable nitrogen, and dialysable nitrogen. The breed groups differed significantly in the amount of dialysable faecal nitrogen excreted but not in any other component.

5. The amount of dialysable faecal nitrogen excreted on equal intake was very significantly negatively correlated with body weight (r = −0·807, P < 0·01).

6. It was found that in two experiments the mean difference between Africander x Herefords and Hereford steers, mean body weights 863 and 686 lb., respectively, was 1·81 ± 0·51 g. nitrogen per day. It was calculated that this would represent about 70 ± 20% of the body-weight difference between the breeds if the lost nitrogen was fully utilizable. This agreed well with the estimate of 65% derived from the square of the correlation coefficient.

Part I, largely introductory, outlines the design of an experiment to measure the responses of ordinary farm crops to supplementary irrigation in a part of England where, from meteorological reasoning, the frequency of need was expected to be about 2 years in 3. The watering treatments were based on estimates of potential transpiration, made from weekly weather data collected on the site, and measured rainfall. The basis of the computation is restated, and the balance of rain and estimated transpiration plotted for each of the 9 years, week by week in summer, month by month in winter. The meteorological specification of frequency of need was satisfied in 5 of the years, during which twenty crops were taken. Of these, eighteen responded to irrigation. In the other years, four of the sixteen crops responded positively to irrigation, and a few of the remaining twelve responded negatively when early irrigation was followed by summer rainfall sufficiently in excess to cause leaching from irrigated plots.

A grass/clover ley (mainly S26 cocksfoot and S 100 white clover 3 years, 1951–53) and a pure grass stand (S 37 cocksfoot 6 years, 1954–59) on the same site had threefold replication of four irrigation treatments: O, unwatered control; C, kept near field capacity throughout; A and B, intermediate between O and C. All plots received the same basic P and K dressing, and half-plots got N dressings either as N1 and N2, or as N2 and N4, the nitrogen being applied in the spring and after every cut except the last at rates: N1 0·15; N2, 0·30; N4, 0·60 cwt. N/acre. Cuts were taken at about 3 or 4 week intervals in the summer, and yields expressed as dry matter.

Potatoes

1951–53, Ulster Chieftain; 1954–56, Majestic, came after spring barley, with threefold replication of four irrigation treatments. All plots received the same basic P and K dressing, and half-plots got N dressings at N1= 0·5, N2 = 1·0 cwt. nitrogen/acre. Under main crop all plots received farmyard at 15 tons/acre, in addition. The ‘early’ potatoes were lifted about mid-July: the main crop at the beginning of October, a few weeks after killing of the haulms by a spray.

1. Twenty Southdown-Romney wether lamb carcasses of a mean hot carcass weight of 39·2 lb. (range 31·2–43·8 lb.) were frozen. Each frozen carcass was divided down the back-bone to give two sides and each side was divided into four parts: leg, loin, 9–10–11 rib cut, and fore. A method of obtaining samples from the parts and from the sides is described. The samples were analysed for water, fat (uncorrected), and residue (uncorrected). The dried residue was analysed to give an ash percentage and a Soxhlet correction factor so that total fat (ether-extract), protein (dried fat-free, ash-free residue), and ash were determined.

2. The weights of the two sides of the twenty carcasses were similar, although the loins of the left sides were highly significantly heavier than those from the right sides and the right fores were highly significantly heavier than the left fores.

3. The mean percentage composition of the two sides of the carcasses studied were similar. Likewise each of the four parts showed close similarity between sides except for the residue and protein percentage of the loin in which the left sides had significantly more protein percentage than the right sides. In all the uncorrected chemical components a significant side × carcass interaction was found.

4. An analysis of the sampling errors showed that the variance of a treatment mean was decreased only slightly by increasing the number of samples per side or by sampling both sides instead of one. Any substantial increase in precision can be achieved only by increasing the number of carcasses per group.

1. In two continuous digestibility trials carried out in 1960 and 1961, groups of three wether sheep were fed on oven-dried herbage which had been selectively collected from natural pastures during December 1959 to March 1960 and December 1960 to March 1961. The organic matter digestibility and the digestible crude protein content of the herbage and the nitrogen concentration in faeces were measured over periods of 5 days. The fresh faeces of dairy cattle grazing the natural pastures were regularly sampled and analysed. Regressions of organic matter digestibility and digestible crude protein content on faecal nitrogen were evaluated. From these equations and the composition of the dairy cattle faeces the digestibility of the herbage grazed was calculated.

2. The herbage consumed by the cattle had a significantly higher organic matter digestibility and digestible crude protein content than the collected material. This difference, which increased as the season progressed, indicates that dairy cattle became increasingly selective in their grazing as the pasture deteriorated in quality.

3. There was a marked yearly difference in digestibility-faecal nitrogen relationships and in the quality of the consumed forage. The grass eaten in 1959-60 had a higher digestibility and lower digestible crude protein content than in the following year. These differences may be part attributable to a seasonal difference in rainfall.

4. The organic matter digestibility of the grazed herbage ranged from 52·71 to 65·03% and the digestible crude protein content from 3·08 to 7·43% For milk production, the herbage consumed is low in digestible protein in relation to the total amount of digestible nutrients.

1. The effect of feeding three levels of concentrates on the organic matter digestibility of two kinds of herbage was determined in four Latin square trials with four wether sheep.

2. Analysis of variance of the trials showed that the organic matter digestibility of all mixed feeds was significantly higher than that of the corresponding herbage. With one exception, the organic matter digestibility of the mixed feeds within each trial was not significantly different.

3. The digestibility coefficients of the concentrates, derived by difference, were invariably high and exceeded 100% for four levels of addition. This indicated a marked improvement of the digestibility of herbage when it was fed with certain levels of concentrate.

4. A possible explanation of the increase of digestibility was discussed and the practical implications of the results indicated.

1. A low magnesium diet is described, consisting of barley straw, sucrose and casein, which induced hypomagnesaemia and one case of clinical tetany in non-pregnant, non-lactating ewes.

2. On the above diet a daily drench of 0·25 g. MgO maintained plasma magnesium levels at 1·60–1·80 mg./100 ml. which was significantly higher than the plasma magnesium level of 1·09–1·20 mg./100 ml. for the unsupplemented group.

3. An experimental formulation of a magnesium heavy pellet is described and its use as a method of supplementation was investigated. On the above diet it was found that two or four heavy pellets also maintained plasma magnesium values at 1·601–80 mg./100 ml. which was significantly higher (P = 0·01) than the level of the unsupplemented group.

4. Five sheep out of the forty ewes used in this experiment were found to have consistently lower plasma magnesium values than the remaining thirty-five.

5. A preliminary trial of the use of heavy pellets as a magnesium supplement in non-pregnant, non-lactating ewes on winter grazing is described. The results of the trial under these conditions were encouraging.

This study is based on 1015 live single calves brod by artificial insemination in a herd of Ayrshire, Friesian, Jersey and two-breed and three-breed cross cattle derived from them. Birth weights, subjected to a least squares analysis, show little effect of year or season of calving. Males were 6·0 lb. heavier than females; second and later parity calves were 6·6 lb. heavier than first parity calves.

Over the range of breeds and crosses studied, heredity was the principal determinant of mean birth weight. No evidence of heterosis was found— means for crossbred calves, however, differed in reciprocal crosses. They deviated from the mean of the parents in the direction of the maternal weight at birth. If 0 is the mean birth weight of the dam's breed or cross and 0 of the sire's breed, the mean weight of offspring is closely estimated by

This expression may not apply to the crossing of breeds differing much more in weight than the Jersey and Friesian breeds. In such crosses it is likely that small dams depress foetal growth more than large dams promote it. The maternal influence on birth weight in cattle as expressed above is in both qualitative and quantitative agreement with the maternal influence as derived from egg transfer studies in sheep.

It is a pleasure to record the authors' heavy obligations to many friends for help during the course of this long experiment. The Milk Marketing Board, in the persons of Dr J. Edwards, C.B.E., Mr T. O'Sullivan, and their colleagues at the A.I. centres made the breeding programme possible. Much time has been saved and much statistical computation cut short by the help afforded us at the Rothamsted Statistical Department by Dr F. Yates and his staff, particularly Mr J. H. A. Dunwoody. Responsibility for the animals on the farms fell at first upon Mr W. S. Biggar, and from 1950 upon Mr J. S. Tavernor. They were aided by many of whom mention must be made of Mr H. L. Williams, Mr R. Pringle and Mr R. Simpson. In the preparation of this paper the authors have been much influenced by the work and criticism of their colleagues.

The current standards or estimates of the essential amino acid requirements of swine are based almost wholly on growth trials. These were carried out with groups of three or four pigs fed individually on semisynthetic diets. The trials generally lasted for only 30–35 days since several expensive amino acids were being fed. The main criticism is that the values given were not adequately substantiated by carrying out nitrogen-balance determinations. It is also possible that the nitrogen-retention values might have led to different conclusions from those arrived at on the basis of the growth trials only. The standards must remain tentative until tested with a larger number of animals and until many more nitrogenbalance determinations have been carried out.