The composition and weight of young cotton leaves at a fixed age are given for 3 years which had different rainfall before the sowing of the cotton, and for which the final yields of the cotton are also known. These yields are inversely related to the early growth and percentage composition of the crop. It is not possible to explain this, but the differences in early growth and nutrient absorption are in accord with expectation. In a year of heavy rainfall before sowing, surface soil nitrates are low, which accords with the smaller amounts of nitrogen taken up by the plants. Furthermore, there is evidence to suggest that in such a year the physical condition of the soil would be poor, which is consistent with poor growth and the low uptake of nutrients other than nitrogen.

In the Sudan Gezira the yields of irrigated cotton are positively correlated with the amount of rainfall in the 6 weeks before sowing. This is not due to increased nitrate in the top foot of soil nor is it due to increased efficiency of absorption of nutrients in years of high rainfall.

The survey shows that objective estimates of the yield of maincrop potatoes can be obtained from small samples carefully selected and dug by hand. Samples taken from about 1000 fields gave estimates of the mean yield of all counties sampled with a standard error due to sampling of less than ± 0·2 ton/acre. The precision of the estimate could have been improved by a better distribution of samples among counties.

The results point to underestimation on the part of the official estimates, in each of the 3 years, especially in the case of high yields in particular counties, and in particular years. The discrepancy between the official and the survey yields is of the order of 1¾ tons/acre, after all necessary corrections have been applied to the survey yields.

The experience gained in the survey indicates that the method of sampling adopted provides an accurate and reliable method of estimating the yields of potatoes which could supplement, and, possibly, ultimately replace the present official estimates if more accurate estimates are required. A national scheme, properly designed, which would include all the potato-growing areas in due proportion should not be unduly expensive to operate. Estimates so obtained would not only be generally more accurate than those obtained by the present official method, but, perhaps more important, would indicate far more closely the fluctuation in yield from year to year.

1. The effects of various starch and protein supplements on the digestibility of cellulose determined by the Norman-Jenkins technique and other constituents of the ration were studied in sheep.

2. The addition of small amounts of maize or potato starch or flaked maize to a ration of about 1 lb. of poor hay was associated with a depression in the digestibility of (Norman-Jenkins) cellulose.

3. When tested separately at varying levels, the addition of nearly pure maize protein, casein, white fishmeal, decorticated groundnut cake meal, urea or urea + DL-methionine, had no effect on the digestibility of cellulose, at any particular level of starch equivalent.

4. The digestibility of nitrogenous nutrients was depressed by the addition of maize starch or flaked maize to the ration except when urea was the nitrogen supplement. The depression was even greater when potato starch was added to the ration instead of maize starch.

5. The retention of nitrogen was not decreased by the addition of starch to the ration, although the digestibility of nitrogen-containing material was depressed. The retention was increased when starch was added to a ration containing casein.

6. The retention of nitrogen was poor from rations containing urea and starch, but it was slightly improved by the supplementation with 1 g. DL-methionine per day.

7. The addition of the various supplements had no marked effect on the digestibility of the dry matter or ‘other nutrients’ of the ration.

8. It is suggested that the growth of the microorganisms digesting cellulose in the rumen is not dependent on the supplementary feed nitrogen when the substrate they are digesting contains a reasonable amount of nitrogen. This amount appears to be about 1%.

9. The addition of vitamins of the B-complex to a daily ration of 1100 g. of hay did not affect the digestibility of the dry matter or nitrogencontaining substances or the retention of nitrogen by sheep.

The materials and methods have been described in the first paper of this series (Glover, 1953). All experiments were of 33 factorial design (Yates, 1937) involving three different levels of supply of nitrogen, phosphorus and potassium.

The results of the measurements are shown graphically in Figs. 1–4 inclusive. Because of the limits set by reproduction of Figs. 1 and 2 it is impossible to show minor variations due to different treatments. Where the curves of uptake run together one broad line is used to denote this. Deviations from this line are shown where they occur. Superimposed on the figures are lines denoting the length of the tasselling and silking periods. Thus a line covering a period of, say, 10 days and bearing the symbol T shows that tasselling in the particular series was completed in that period, and the first tassel was set at the date corresponding to the start of the line.

The weight, length and quality (fineness) of wool produced at different times of the year and under different nutritional conditions has been determined over a period of three years by clipping at monthly intervals the wool grown on delineated skin areas of sheep. The treatments consisted of

(a) wet ewes, grazing on pasture all the year, subjected to high and low levels of feeding during the ‘dry’, pregnancy and lactation periods;

(b) dry ewes and lambs fed differentially on grazing during the winter and spring;

(c) wet ewes fed in stalls on a diet of constant composition at rates sufficient to maintain constant effective body weight (i.e. making allowance for pregnancy increase and fleece weight increase). A small number of these ewes was also subjected to increased environmental temperature during the winter.

The experiments have shown the existence of a marked seasonal rhythm in wool growth having a maximum in January (midsummer) and a minimum in July (midwinter). Changes in weight of wool grown are caused by sympathetic changes in both length and diameter. At the same level of feeding the rate of wool growth in midwinter is about onethird of that in midsummer.

The nutritional demands of pregnancy reduce the rate of wool growth in winter and those of lactation delay the rise in production in spring. Nutrition also plays an important part in determining the time of the maximum and minimum. In dry sheep the maximum tends to occur before midsummer when pasture growth is at its best, but lactation in wet sheep prevents the expression of a maximum early in the summer, so that in these ewes it generally occurs after weaning, and therefore after midsummer. The level of nutrition also determines within limits the magnitude of the maximum and minimum.

The fundamental cause of the seasonal rhythm of wool growth remains obscure. Nutrition, pregnancy and lactation can modify the rhythm, but it exists strongly even when variations due to these are eliminated. The seasonal rhythm of solar radiation has recently been shown to influence rate of wool growth, particularly during winter, and though this is undoubtedly one factor it is not the only one. Temperature has been suggested elsewhere as a possible cause, but the experiments described do not support the theory that environmental temperature has any direct effect on wool growth. It is suggested, however, that the seasonal rhythm of temperature may be a second factor.

1. A feeding trial is described including four groups of cattle fed on grades I, II and III silages and on swedes, straw and oats respectively.

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. All three grades of silage produced a significantly greater rate of fattening than swedes plus straw and oats. There was no significant difference between the fattening values of the three grades of silage.

5. The dressing percentages found for 100 silagefed and 71 swede-fed cattle are given. The swedefed cattle yielded a greater average dressing percentage.

6. It is suggested that the higher dressing percentage found for root-fed cattle as compared with silage-fed cattle can be attributed to the more rapid elimination of dietary water from the body in rootfed cattle.

7. An animal behaviour study is described, the time spent by cattle on the four diets, eating, cudding and lying down, being determined.

8. Cattle fed on grass silage spent longer on feeding plus cudding than swede-fed cattle.

9. An experiment is described designed to determine the effect of the dry-matter percentage of the diet on the dry-matter intake of ruminants.

10. The results indicate that when ruminants are subsisting on a diet consisting solely of succulents, the dry-matter intake is depressed when the dry-matter percentage of the diet falls.

1. The resting heart rate of cocks and hens was measured in varying degrees of heat stress, and during acclimatization to heat.

2. When the rectal temperature was below 110°F. (43·3° C), the heart rate varied inversely with the severity of the climate up to an air temperature around 99° F. (37·2° C).

3. At air temperatures of 99° F. (37·2° C.) and above the heart rate was nearly constant over a wide range of rectal temperatures below 110° F. (43·3° C). It averaged about 50 beats/min. less than in an equable climate.

4. Above 110° F. (43·3° C.) there was an increase of about 30 beats/min./° F. (17 beats/min./° C.) rise in rectal temperature. The rate equalled that found in an equable climate, when the rectal temperature reached 111–112° F. (43·9–44·4° C). Over this zone of body temperature the fowls were often agitated.

5. In severe heat stress there was a slight fall in the heart rate on acclimatization, but this was small compared with the effect of climate.

6. In severe heat stress the heart rate during the day was slightly higher than that at night.

7. The relation of these findings to the mechanism of temperature regulation is discussed.

After it had become evident that vitamin B12 can be considered as a part of the so-called ‘Animal Protein Factor’, several experiments with young fattening pigs have been carried out in the Netherlands. The purpose of these experiments was to gain experience as to the value of products rich in vitamin B12 for pig feeding. In these trials 312 animals were used.

The results can be summarized as follows:

1. Substitution to a large extent of animal protein by vegetable protein in rations containing tho same total percentage of protein resulted in a retardation of growth.

2. Addition of vitamin B12 supplements to feed mixtures low in animal protein in this series of experiments generally gave better results than could be obtained without this addition. In the majority of cases, however, the results did not equal those of the groups which received rations containing the usual amount of animal protein.

3. Vitamin B12 can be considered as a component of the animal protein factor, but besides this there probably exist other factors which contribute to the special value of animal protein for young pigs.

4. In circumstances such as prevail in the Netherlands, little benefit can be derived for pig fattening from the use of products rich in vitamin B12.

1. A rapid extraction procedure of dried and ground plant material has been used in conjunction with the Lundegårdh flame method of spectrographic analysis. The accuracy of the analysis has been estimated, and the method has been shown to be comparable with ashing and gravimetric analysis.

2. The effect of fertilizer treatment on yield and on the nutrient composition of the crop has been outlined. The changes which occurred in the period

1852 to 1921 have been summarized by linear regressions fitted to 10-year means.

3. The recovery of potassium was estimated, and the exhaustion or accumulation of potassium was shown to be related to exchangeable potassium in the surface soil.

4. Sodium and magnesium sulphates used as fertilizers were shown to increase crop yield by increasing the potassium supply to the crop. It has been shown that the extra potassium came from non-exchangeable forms.

A uniformity trial on groundnuts has been analysed and the results discussed. Plant number is less variable than yield and less sensitive to shape of plot and of block. For yield, long narrow plots are more efficient than shorter and wider plots, in all shapes and sizes of blocks and in Latin squares. The plots should not be arranged end to end along the contours, but side by side, either singly or in pairs, forming compact blocks.

The regression of the plot variance of the mean yield per unit area on size of plot approximately follows a linear logarithmic relationship. A similar relationship holds for plant number. The value of the regression coefficient b′ is low and it has been shown that, as expected, there is considerable gain from the use of small blocks. The efficiencies of various confounded and incomplete block designs relative to designs in larger blocks have been determined for some particular layouts, and values for other layouts, ignoring shape of plots and of blocks, have been obtained by interpolation.

The field used for this uniformity trial appears equally variable in all directions.

1. Observations made on growing a series of crops in rotation over a range of static ground water-levels in a Fen peat soil are recorded.

2. The crops used show differences in their reaction to ground water conditions, and the seasonal incidence of rain has an overriding influence on their performance.

3. The effects of ground water-level may operate directly on the growth and development of a crop or may influence it indirectly through factors such as weed infestation, difficulties of cultivation, or the incidence of disease.

A study has been made of the relationships of sterile Friesian bulls manifesting ‘knobbed’ spermatozoa, and the conclusion drawn that the characteristic defect of the acrosome is due to an autosomal sexlimited recessive gene (kn).

1. Chromosome pairing has been studied in twenty-two different sterile F1 hybrids involving the genera Aegilops, Agropyron and Triticum, together with their colchicine derived amphidiploids having chromosome numbers of 2n = 42, 56 and 70. Cytological evidence has been correlated with male and female fertility, while chromosome pairing in the parents has been studied in relation to their amphidiploids.

2. Some of the sterile F1 hybrids showed little or no pairing, while in others the pairing was appreciable. There was an association of the amount of pairing with the parental combinations used in the production of the hybrids in that the interspecific hybrids were characterized by a relatively high degree of pairing, particularly those with 28 chromosomes, while the intergeneric hybrids either lacked pairing or showed a low incidence.

3. In the A1 amphidiploid generation, chromosome pairing was in all cases high, and in some cases almost complete. In all cases multivalent formation in the amphidiploid was lower than bivalent formation in its undoubted F1 hybrid. Different amphidiploids showed various degrees of differential affinity. Univalent formation occurred in some amphidiploids, while bivalent formation in some was increased by a loss of chromosomes.

4. In all cases there was a reduction in chiasmata per nucleus and chiasmata per bivalent in the amphidiploid compared with its parent species. Reduction values were not directly associated with any increase in chromosome number of the amphidiploid, nor with the presence of multivalents.

5. No confirmation could be obtained of the view that multivalent formation in amphidiploids is a more generally sensitive index of chromosome homology than bivalent formation in the undoubted F1 hybrid. The absence of multivalents in an amphidiploid does not disprove the existence of structural chromosome homologies between the two parents.

1. In the summer of 1945 samples of the growing crop were taken from eight Broadbalk plots. On all the plots the concentrations of nutrients in all parts of the plants decreased during growth. The compositions of the roots and stems and leaves varied with fertilizer treatment at all times of the season. The nutrient composition of the ears was only slightly affected by fertilizer treatment.

2. The total uptake of nutrients by the crop increased to a maximum and then decreased. The losses of potassium and magnesium from the stems and leaves were particularly large, due to translocation into the ear but there were also net losses of potassium and calcium from the whole plant.

3. The changes which occurred were similar on all plots and the effect of fertilizer treatment on plant composition was always related to the effect at harvest. There was no evidence that the composition of the crop at harvest differed radically from the composition earlier in the season.

1. The rectal temperature of piglets was determined (a) at intervals from birth up to 18 days, (b) at the same time daily until the piglets appeared to be fully thermoregulated.

2. The rectal temperature of a vigorous piglet during parturition may be as high as 104–105° F.

3. During the first few minutes after birth the temperature falls to about 100° F., partly as a result of the lower temperature of the external environment and partly as a result of rapid evaporation of amniotic fluid with which the young pig is covered. The fall in temperature is greater with lighter pigs than with heavier pigs.

4. The temperature falls until the young pig finds its way round to the teats and starts to suckle. This struggle and activity of suckling together with the warmth in the sow's nest causes a temporary rise in temperature. During the first rest the temperature falls again to about 100° F., but vigorous pigs have a normal temperature within 12 hr.

5. Piglets deprived of milk after 5 hr. and 16 hr. suckling experienced a more or less steady fall in temperature to about 98° F. in 2–3 days, when the pigs were comatose and were killed. In the case of a pig which had suckled for 7–8 days the temperature remained more or less normal for 2 days and then declined to 95° F. during 5–6 days. The length of survival depends largely on the initial weight, i.e. on the reserves accummulated during the suckling period, and possibly on the thickness of the insulating layer of subcutaneous fat.

Analyses of grass samples from seventeen fertilizer trials on acid soil showed that both the percentage phosphate in the grass and the amount of phosphate removed by the crop were significantly and directly related to the percentage saturation of the b.e.c. of the soil. The amount of acid-soluble phosphate by difference (Table 1, A — B) was also significantly and directly related to the percentage phosphate in the grass but not to the amount taken up by the crop. The amounts of exchangeable bases, exchangeable calcium and acid-soluble, adsorbed and watersoluble forms of phosphate showed no significant relationships with phosphate uptake and percentage phosphate in the grass.

The percentage saturation of the b.e.c. was found to be, on the average, about five times as effective a contributory factor to the percentage phosphate in the grass as the amount of acid-soluble phosphate by difference. The results confirm previous work, which indicated that in acid soils the main form of available phosphate is that associated with the exchangeable bases the effective presence of which is governed by the percentage saturation of the b.e.c. It is considered that phosphate availability and response in acid soils are best assessed by considering the percentage saturation of the b.e.c. rather than the amounts of some form or forms of phosphate in the soil.

The grass analyses also showed that when the amount of phosphorus (P) hi the dry grass exceeds 0·33% no response to phosphate is to be expected. When the percentage in the grass is less than 0·23% responses of 10% or more are likely.

A method is suggested for the quantitative description of the genetic structure of pedigree breeds of animals. Results are given for eight breeds, showing that the number of herds controlling effective breeding policy is in all cases small.

1. The effects of injections of oestradiol dipropionate, testosterone propionate and progesterone in immature pullets have been studied.

2. Oestradiol dipropionate evokes hypertrophy of the oviduct, and increases in serum calcium and serum riboflavin.

3. Testosterone propionate evokes hypertrophy and reddening of the comb and wattles, it acts synergistically with oestradiol dipropionate in evoking hypertrophy of the oviduct.

4. Progesterone antagonizes the effects of oestradiol dipropionate and testosterone propionate on the growth of the oviduct.

5. Progesterone and/or testosterone propionate increase the percentage of free riboflavin in the hypertrophied magnum from 18% of the total vitamin present to 35%.

1. Piglets reared in a cold building but in pens provided with electrically warmed or wooden beds weighed considerably more at 8 weeks old than piglets reared in pens with solid concrete floors covered with thin permeable cork-tar bricks. At 3 days and 3 weeks old there were no differences in live weight between the three groups.

2. Before weaning at 8 weeks old the piglets reared on concrete floors had very much poorer appetites for solid food than had those from the other two groups.

3. Although the blood haemoglobin concentrations of piglets on warmed and wooden floors rose between 3 and 8 weeks of age, the haemoglobin concentrations in the group on concrete floors fell. The differences in concentrations between groups at weaning just failed to be statistically significant at P = 0·05.

4. Under the conditions of this experiment the provision of electrically warmed or wooden floors diminished but did not eliminate the incidence of a pathological liver condition in pigs which has been attributed to poor housing conditions.

5. The low weaning weights, poor appetites, low haemoglobin concentrations at weaning and the presence of the liver disease in piglets born on concrete floors were probably interdependent, but the mechanism and direction of this interdependence could not be explained from the data collected.