1. An experiment is described which lasted for 5 years and in which a comparison was made of twelve grasses or grass mixtures under different fertilizer nitrogen treatments and also when grown with clover. The herbage was cut 4–6 times in each season. Adequate amounts of mineral fertilizers (280–340 lb. K2O and about 100 lb. P2O5 per acre per annum), and the following nitrogen treatments were applied: (1) no nitrogen, no clover, (2) grass sown with clover, (3) 140–208 lb. nitrogen per acre per annum in four to six equal dressings, (4) 350–416 lb. nitrogen per acre per annum in five and six equal dressings.

In 1951, 1952 and 1953 the clover dominant swards (treatment 2) were split between the following treatments; (X) as (3) above, (Y) 35 lb. nitrogen per acre in spring and again in late summer, (Z) no nitrogen as (2) above.

2. The average yields for the 4 years were 2180, 5940 and 8300 lb. dry matter per acre, and 290, 850 and 1460 lb. crude protein per acre for treatments 1, 3 and 4. With treatment 2 the average yields were 2830 lb. dry matter and 400 lb. crude protein in 1949 and 4270 lb. dry matter and 820 lb. crude protein in 1950. An approximate average yield for the 4 years from treatment 2 was 4630 lb. dry matter and 860 lb. crude protein. In 1951–3 average yields for treatments 2X, 2Y and 2Z were, 7240, 6340 and 5750 lb. dry matter and 1240, 1180 and 1100 lb. crude protein per acre.

3. There were considerable differences between grasses in nitrogen response and compatibility with clover. The highest yields with fertilizer nitrogen were given by cocksfoot strains, but, in the presence of clover, ryegrass and timothy strains gave the highest yields. There were also differences between strains within each species.

4. Mean crude protein contents were, for treatments 1, 3 and 4, 13·3, 14·3 and 17·6%, and for treatments 2X, 2Y and 2Z in 1951–3, 17·2, 18·6 and 19·1%. Differences between species were significant in only a few instances.

5. The distribution of yield over the season was most regular with treatment 4. Cocksfoot species gave the least variable yields from cut to cut, while those from timothy and ryegrass swards were the most variable.

6. Treatments 3 and 4 maintained a high proportion of sown grasses in the swards. In treatment 2 the clover percentage rose to a high level by 1950. A high percentage was maintained under treatment 2Z in 1951–3. Treatment 2Y depressed the clover content in some grasses, and treatment 2X further depressed it in those grasses. A fairly high clover content was maintained, however, even with treatment 2X with some timothy strains and meadow fescue.

7. The mineral fertilizers applied maintained the soil analysis at a satisfactory level.

8. The results are discussed with special reference to the relative merits of fertilizer nitrogen and clover nitrogen and to the differences between species and strains.

The results of seventy-one field experiments to compare the effects on crop yields of the phosphate in Billingham nitrophosphates and in superphosphate are reported. The experiments tested nitrophosphates from a manufacturing process in course of development. The 1950 and 1951 products contained less water-soluble P2O5 and slaked less easily in water than the 1952 product.

All three Billingham nitrophosphates gave rather bigger increases in yields of grass and about the same increases in yields of swedes as superphosphate. The 1950 and 1951 products gave about 70% of the increases in yield given by super-phosphate on potatoes but the 1952 product gave about 90% of the increase with superphosphate. There was no evidence that powdery Billingham nitrophosphate was any more effective than granular material.

It is concluded that the phosphate in the 1952 Billingham nitrophosphate is, for practical purposes, as effective as that of superphosphate.

A continental nitrophosphate tested in 1952 gave poorer results than Billingham nitrophosphate. This product contained little water-soluble P2O6 and slaked very slowly in water.

Comment is made on the apparently poor average response of British grassland to phosphate fertilizer.

1. Experiments with two sheep are described in which energy retention was measured at different levels of food intake and the losses of energy incidental to food consumption measured.

2. Attainment of reasonably stable values for energy losses occurred after 72 hr. of fast. On realimentation stable values were not attained until 10 days had elapsed. Methane production was resumed relatively slowly.

3. The accuracy of the mean estimates of energy retention was high, and duplicate determinations of metabolism after lapses of time gave excellent agreement.

4. It is shown that the assumption of linearity of the relationship between energy retention and food intake expressed as metabolizable energy is incorrect.

5. An exponential relationship between energy retention, and food intake was employed to describe the data. This resulted in a reduction of the residual sum of squares compared with a linear regression.

6. It is shown that net energy values (starch equivalents) measured by Kellner, Armsby and Forbes have entirely different meanings, and that the correction employed by Wood reflects these facts.

7. The exponential relationship has been generalized to take into account body-size variation and has been examined as far as it affects concepts of efficiency of food utilization, and of nutritional plane.

8. Nutritional plane has been rigidly defined in such a way that it is independent of body size and of food quality, and it enables net energy values to be predicted at other planes of nutrition once the net energy value at one nutritional plane is known.

9. A simple and rational scheme for the feeding of livestock to take into account the decline in net energy value (starch equivalent) with nutritional plane has been devised.

10. Analysis of the energy losses in relation to nutritional plane shows that losses of energy in faeces, urine and as heat per unit food ingested tend to rise with increasing nutritional plane. Methane losses fall. These results suggest that the prediction of net energy values from measurement of energy losses in faeces, or from estimates of metabolizable energy, can give rise to extremely unreliable results.

11. The results have been discussed in relation to previous work in this field. It is pointed out that the exponential relationships employed are a convenient method of describing a very complex situation and facilitating its analysis.

1. Pigs housed in both a good and a bad piggery were kept to a medium plane of feeding on diets with and without a procaine penicillin supplement. Antibiotic improved neither efficiency nor rate of growth in either piggery during the period from weaning to 100 lb. live weight, nor from then to slaughter at 200 lb. live weight. The average temperatures during the first half of the experiment were 43 and 51° F. in the bad piggery and in the sleeping pens of the good piggery respectively. During the second half of the experiment these averages were 54 and 58° F. respectively.

2. Between weaning and 100 lb. live weight, pigs housed in the bad piggery grew 6% more slowly and 5% less efficiently than in the good piggery, but although the growth rates fitted in well with previous observations, neither difference was statistically significant in this experiment.

3. Between 100 and 200 lb. live weight pigs housed in the good piggery grew 3% less efficiently than in the bad piggery, but there was no difference in rate of growth. The difference in efficiency was statistically significant.

4. Carcasses from pigs housed in the good piggery were fatter than from pigs housed in the bad piggery. These fatter pigs also had higher killing-out percentages.

5. Although dietary antibiotic supplement had no effect upon growth rates or carcass measurements, it resulted in higher killing-out percentages.

1. Methods for the determination of ammonia and nitrate in soil are described. The ammonia and nitrate are extracted at pH 1·0–1·5 with a mixture of potassium sulphate and sulphuric acid, and the ammonia is determined by distillation with magnesium oxide at 25° C. in a modified Conway microdiffusion unit. Ammonia plus nitrate is determined on a separate sample of the same extract by reduction of the nitrate to ammonia with titanous hydroxide and subsequent distillation with magnesium oxide, both the reduction and distillation being carried out in a modified microdiffusion unit at 25° C.

2. The methods are applicable to coloured extracts and are not affected by substances found to interfere with other methods of determining ammonia and nitrate.

3. It is suggested that the methods may also prove useful for the determination of ammonia and nitrate in plant materials.

Before the feeding of antibiotics to pigs can be confidently recommended, more evidence is required as to their effect on growth and efficiency of food conversion. The present series of trials were designed with this object in view. The investigations were carried out by statistically designed growth trials as well as by nitrogen-balance determinations in the metabolism crates.

The main point under investigation in the first growth trial was whether the addition of penicillin to a well-balanced diet supplemented with whitefish meal would result in an increased rate of growth and efficiency of food conversion. It was concluded that, although the trend both as regards live-weight gain and efficiency of food conversion was in favour of the penicillin-fed pigs, the differences were too small to reach statistical significance. Nitrogenbalance determinations were also carried out over a period of 63 days on the white-fish meal diet with and without penicillin. The mean daily retention of nitrogen by the two hogs on the control treatment was 11·59 g., and by their two litter-mates on the penicillin treatment 11·42 g.

In the second growth trial penicillin was added to a diet composed of barley meal and fine bran together with a little lucerne meal and minerals and supplemented with extracted-decorticated groundnut meal. In both the group-feeding and in the individual-feeding trial there were ten pigs receiving this basal diet and twenty pigs on the same diet supplemented with 18 mg. of procaine penicillin per lb. of meal fed. This amount of penicillin is more generous than normally used by food manufacturers. There was a striking contrast in the eagerness with which the pigs fed. The penicillin-fed pigs licked their troughs quickly and cleanly in contrast to the other pigs, and it was quite apparent that the antibiotic had a tonic effect in this respect. Although this difference diminished as the trial proceeded, it was still evident when the pigs averaged 100 lb. live weight. It was also quite obvious that the pigs receiving penicillin drank more water than the control pigs. After 10 weeks on experiment the forty pigs receiving penicillin averaged 87·5 lb. in live weight as compared with a mean of 81·7 lb. for the twenty pigs on the control diet. This compares with mean live weights of 186·6 lb. (penicillin) and 177·9 lb. (control) over the whole 20 weeks that the trial lasted. The differences for the group-fed pigs were too small to reach statistical significance, owing to the wider variations within the groups. Highly significant differences, in the period from 36 to 90 lb. live weight, were obtained with the individually fed pigs. The mean live-weight increase per day was 0·95 lb. on the penicillin treatment as compared with 0·88 lb. on the control diet. Correspondingly significant differences characterized the figures for efficiency of food conversion over this period, the mean requirements being 2·97 lb. on the penicillin treatment and 3·21 lb. on the control diet. In the period from 90 to 200 lb. live weight the differences observed were very small and not statistically significant. Over the whole period from 36 to 190 lb. live weight the control pigs required on an average 5·3 more days and consumed approximately 19 lb. more meal per pig, an increase of 3·4%.

The same diet, supplemented with ex. dec. groundnut meal, was used in the second nitrogen-balance trial. The addition of penicillin failed to bring about any significant improvement in the retention of nitrogen or in the utilization of the dietary protein.

The effect of adding penicillin alone and also in conjunction with a vitamin B12 supplement (Distafeed), to the diet supplemented with ex. dec. groundnut meal, was investigated in the third growth trial. The penicillin-fed pigs were better feeders from the start than the control pigs, but in this trial the Distafeed seemed to have an adverse effect on palatability. From a common initial live weight of 40 lb. for each pig up to 90 lb. live weight, the pigs on the control treatment required on an average 3·6 days longer and consumed 10·54 lb. more meal than the pigs receiving procaine penicillin. The liveweight increase per day averaged 0·92 lb. on the control diet in comparison with 0·98 lb. on the penicillin treatment. The figures for efficiency of food conversion were also in favour of the penicillinfed pigs, being 3·05 and 3·25 lb., respectively. To increase 155 lb. in live weight the penicillin-fed pigs required on an average 4 days less with a saving of about 13 lb. of meal per pig, in comparison with the control pigs. The improvement was entirely confined to the period immediately after weaning. No improvement resulted from the simultaneous addition of vitamin B12 with the antibiotic.

The nitrogen retention of pigs was also investigated with and without penicillin and vitamin B12, using diets supplemented with ex. dec. ground-nut meal and extracted soya-bean meal. A summary is given of the results of nitrogen-balance studies with twenty pigs to investigate the effect of antibiotics on protein metabolism.

It was concluded from the above trials that the main effect of procaine penicillin was to stimulate the appetite of the pigs on all-vegetable diets. It seemed therefore that unless the pigs were allowed to benefit fully from their improved appetites, by being allowed full-feed, the maximum effect from the feeding of penicillin would not be attained. In the fourth growth trial this point was tested, using the group-feeding lay-out and adjusting the ration daily so that food was available almost continuously. With the individually fed pigs in this trial the opportunity was taken to test the statement that the magnitude of the response to the feeding of antibiotics is greater with diets supplemented with soya-bean meal than with other vegetable-protein concentrates.

The group-fed pigs under conditions approaching ad lib. feeding were able to consume without wastage distinctly higher amounts of meal than we usually feed in these growth trials, when the meal is restricted according to the feeding chart. The pigs receiving penicillin displayed at first better appetites than the control pigs, and made correspondingly better live-weight gains, but as the trial proceeded the appetite of the control pigs gradually improved and eventually surpassed that of the penicillin-fed pigs. It seemed as if the latter had been overeating in the initial period and were suffering from surfeit. After 11 weeks on experiment the mean live weight of the control pigs was slightly higher than that of the group that received penicillin. It is also interesting to note that with ad lib. feeding, no outstanding difference in water consumption was observed between the treatments, the water consumption being mainly influenced by food consumption.

The results for the individually fed pigs in the fourth growth trial showed that the effect of adding penicillin to a cereal diet supplemented with ex. soya-bean meal was even less pronounced than with ex. dec. ground-nut meal. No significant effect was shown, even in the period immediately after weaning, on the rate of gain or on the efficiency of food conversion as a result of adding 18 mg. of procaine penicillin per lb. of meal. In this trial the pigs were exceptionally good feeders and the soyabean meal diet proved to be highly palatable.

It may be concluded from the results of these trials that with healthy pigs and using normally balanced palatable rations, the improvement in the rate of growth, efficiency of food conversion and rate of nitrogen retention to be expected from the inclusion of penicillin in the diet is generally too small to make it economically worth while.

1. Some earlier work concerning the management of lucerne is discussed.

2. Two experiments, designed to compare cutting and grazing the second (July) crop, and cutting and grazing the third crop at two different dates (September and October) each year on the yield and botanical composition of a lucerne-grass (mainly cocksfoot) ley, are described and the results discussed.

3. The method of defoliating both the second and the third crops had very little lasting effect on yield or composition of the ley, though some temporary effects, depending on season, were found.

4. It is shown that date of defoliating the third (autumn) crop of a lucerne-grass mixture may influence the yield of oven-dried produce from an individual crop. Late autumn defoliation led to a greater yield of lucerne and a greater proportion of lucerne in the produce, but since the opposite effect was found in the yield of grass there was no overall effect on the total yield of oven-dried produce over a 3-year period.

5. In these experiments it appeared that lack of winter cover had no adverse effect on the productivity or persistence of lucerne in the lucerne-grass mixture studied.

1. The seed of crosses of Secale cereale with S. montanum and S. dalmaticum germinated only when S. cereale was the seed parent.

2. S. cereale was found to differ from S. montanum and S. dalmaticum by two large translocations involving three pairs of chromosomes, and a small translocation involving a fourth pair. The fertility of the F1 plants was low, and in ear morphology and perennial habit they were similar to the S. montanum and S. dalmaticum parents.

3. S. montanum and S. dalmaticum were found to be similar in gross chromosome structure and their hybrids were phenotypically intermediate and fertile.

4. The F2 of the cross S. cereale x S. dalmaticum consisted of three types, in terms of chromosome structural condition and plant morphology, those like one or other parent and those like the F1.

5. The genetic and evolutionary significance of this situation is discussed, together with the problem of the fixation of translocations in populations.

1. A condition that appears to be identical with ‘green yolks’ as observed in natural cases has been reproduced by the oral administration in gelatin capsule of from 250 to 1000 mg. sodium copper chlorophyllin 100% daily for 4 days upwards to Light Sussex hens in second lay.

2. Following suitable extraction procedures the presence of a chlorophyll derivative has been determined spectrophotometrically in the affected yolks.

3. Quantities of sodium copper chlorophyllin of the order of 1 mg. have been recovered from affected yolks.

4. It is considered that the passage of chlorophyll to the yolk indicates that intestinal absorption has occurred.