1. A preliminary study has been made of some aspects of rumen development and fermentation patterns in groups of ewes and lambs fed perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S) and short-rotation rye-grass plus white clover (S + C).

(2) For ewes there was a significant effect on the weight of the rumen contents from the grass species. The treatment (P) which caused the lowest live weight gave the highest rumen contents weight. There were also significant pasture effects on empty live weight both from grass species differences and from the addition of clover.

3. No difference in rumen dry-matter percentages was found between the four groups.

4. There was no significant difference in the concentration of volatile fatty acids in the rumens of the P and S fed ewes but the addition of white clover had a significant effect.

5. The S + C sheep had a lower proportion of acetic acid, a greater proportion of propionic and butyric acids and greater development of the rumen papillae than the P animals.

6. With the lambs there were no significant differences in rumen characteristics caused by grasses but the addition of white clover caused a greater live weight and a reduction in the weight of the rumen contents.

7. These results are discussed in relation to present knowledge of ruminant metabolism.

The very fast development of maize plants at Ibadan, Nigeria, has been described and an attempt has been made to obtain a better understanding of their development with the aid of a growth analysis. Two varieties of maize have been studied, which, again during this experiment, proved to have a very different yielding performance, in spite of a rather similar vegetative development. It was shown that Lagos White, the local variety, produced approximately 2000 lb./acre and ES 2 3000 lb./acre.

From approximately the ninth week onwards the ear starts rapid development, and the retention of a larger functional photosynthetic area by the introduced variety ES 2, from the eighth week onwards, seems to be the major factor controlling its higher production of dry matter in the latter part of development, when compared with Lagos White.

On the average, n.a.r. had similar values in both varieties and had similar deviations at various stages of development; external or internal factors could not be separated. The l.a.r. indicated that, certainly in the latter part of development, ES 2 plants and Lagos White plants had a similar leaf area per gramme of dry matter; but ES 2 had more of both. This factor stresses the similarity of efficiency in both photosynthetic mechanisms.

The l.a.r shows in clear terms the difference between the two varieties grown at equal spacing. The variety ES 2 still increased its leaf area with its additional laminae, when Lagos White, which had a more rapid loss of leaf by senescence, had come to a standstill. The more pronounced longevity of the photosynthetic area in ES 2 appears therefore the major determinant of the higher production of dry matter by this variety. The possible significance of variation in longevity of leaves had been pointed out already in 1929 by Boonstra, who found some evidence of an association of longevity of leaves and high yields in four varieties of oats.

1. Seed production stands of S 37 cocksfoot were obtained with varying plant densities by utilizing two drill widths, removing sections of drill, or over-sowing drilled material. All density treatments were operative at two levels of N, 87 or 174 lb. N per acre per annum.

2. Tillers in selected quadrats were labelled at monthly intervals during autumn and/or winter for 3 years. Performances of tiller populations were assessed from these quadrats.

3. Seed yields were increased in many cases by reducing plant density from a continuous drill pattern. Increased plant density reduced yields. With plant communities on a 1 ft. square arrangement at the high level of nitrogen, an increase of 33%, or 243 lb. seed, per year over a 3-year period was obtained compared with continuous rows at any level of N. The yield of gapped stands increased over the 3-year period, whilst the yields of continuous rows dropped in the final year.

4. Nitrogen significantly increased the yield of cocksfoot, except in the third year, by increasing the weight of seed per ear.

5. Tiller numbers per quadrat increased in most treatments over the course of the experiment, both within years and from year to year; seasonal peaks of tillering were apparent. The effect of N on tiller numbers differed each year, presumably due to the state of the populations when the N was applied.

6. Higher tiller numbers per plant were obtained with lower plant numbers per unit area. Percentage fertility of tillers was generally higher with lower plant densities, and lower tiller numbers per plant, other factors being equal. The only significant effect of N on fertility was to decrease it in the third year.

1. A co-ordinated trial has been carried out at eight centres to compare the performance of group-fed pigs slaughtered at about 200 lb. live weight (bacon weight) with that of litter-mates slaughtered at 260 lb. (heavy pigs).

2. The bacon pigs were fed either ad lib. or restricted according to live weight, while the heavy pigs were all fed ad lib. with one group having the protein supplement withdrawn from the ration after the pigs had reached 140 lb. live weight.

3. Growth rate, efficiency of food conversion and carcass quality (based on dissection) data are summarized in Table 5.

4. In general, the results indicated that under the conditions that prevailed, and when the leanness of the carcass is the major consideration, the slaughter weight around 200 lb. was preferable to the heavier weight (about 260 lb.) both from the production and economic aspect.

1. A 36-day continuous digestibility trial with three steers and three sheep fed fresh pasture herbage was carried out during May and June, 1960. For all animals the digestibilities of herbage organic matter (O.m.) were estimated both by collection of faeces and by administering standard quantities of chromium sesquioxide (Cr203) twice daily and determining concentrations of Cr203 in faeces. In a further 36-day trial during August and September 1960, three steers and three cows were used; with the steers, digestibilities were estimated by both methods but with the cows by the Cr203 method only.

2. Regression equations were obtained relating O.m. digestibility to the percentage of nitrogen (N) in faecal O.m. When digestibilities were estimated by the same method the same regression coefficients could be fitted to the data from each of the steers and sheep in the spring trial. A similar result was found with the data from each of the steers and cows in the summer trial.

3. In each equation different constant terms were required for each animal, which differed significantly between individuals but not between species or class of animal. Data obtained from an examination of the relationship of g. N excreted per 100 g. feed dry matter to g. N intake per 100 g. feed dry matter indicated that differences between the constant terms could be linked with variations between animals in the excretion of metabolic faecal N.

1. The concentrations of 131I in milk, urine, and faeces were compared to the total and non-proteinbound radio-iodine of blood after a single dose of radio-iodine to cows that were being maintained on diets providing about 3·5 or 12-16 mg. of stable iodine per day.

2. In general, the 131I concentrations in milk and urine tended to parallel the non-protein-bound 131I of blood. Faecal 131I levels of the low-iodine cows tended to parallel that of the whole blood, whereas it followed the non-bound radio-iodine of blood for cows on the higher stable iodine diet.

3. Compartmental analysis of the concentration curves showed a component with a T½ of from 10 to 22 hr. being common to both groups of cows. The second component of the curves constructed for the cows on the higher iodine intake had a T½ of from 41 to 58 hr. The second component for the low-iodine cows had a T½ that ranged from 83 to 169 hr. for the urine, faeces and non-bound radio-iodine of blood and 1200 and 1580 hr., respectively, for the faecal and whole-blood curves.

4. A greater proportion of bound radio-iodine was observed in the milk and blood of cows on the low-iodine diet than for the cows on the higher iodine intake. The proportion of bound 131I in blood increased with time, but the bound 131I of milk was relatively constant.

Twelve digestibility trials were carried out using three adult rams on seven legumes and five nonlegume roughages.

In vitro fermentations were carried out over 24 hr. and the percentage cellulose digestion was determined. The whole rumen juice used to inoculate the fermentation tubes was obtained from a sheep with a permanent rumen fistula. Carbon dioxide was bubbled through during the fermentation run, unless otherwise indicated, to ensure anaerobic conditions.

The following significant correlations were calculated from the results:

In vivo and in vitro cellulose digestion for non-legumes: r = 0·93.

In vivo cellulose digestion and D.E./kg. D.M. for non-legumes: r = 0·90.

In vitro cellulose digestion and D.E./kg. D.M. for non-legumes: r = 0·90.

In vitro cellulose digestion and D.E./kg. D.M. for non-legumes + alfalfa and cashrangeeg: r = 0·91.

In vitro cellulose digestion and D.E./kg. D.M. for all forages tested gave a highly significant correlation: r = 0·73.

In vitro cellulose digestion and D.E./kg. D.M. for legumes: r = −0·77.

Regression equations calculated for non-legumes and for all tested forages, when used for predicting D.E./kg. D.M. gave values which differed from the determined digestible energy by ± 8·70and ± 9·90% respectively. Applying Hershberger's regression equation to the present data, the D.E./kg. D.M. values differed by ± 8·69%.

It seems safe to say that all official performance testing and progeny testing schemes for bacon pigs, up to the present, have been based on an implicit assumption that the pigs found to be superior under the management methods at the testing station would also be superior under other systems of management on commercial farms. If consideration is limited to reasonably good standards of management there is probably little danger in this assumption, though there is little direct evidence as yet to support it. The danger of mistakes in the selection of superior genotypes would be more likely to arise if there were systematic differences between the methods of management at the testing stations and on commercial farms. Actually such a difference does occur as regards methods of feeding. At testing stations, the pigs are generally fed more or less to appetite, being given as much as they will readily clear up in two feeds per day in England (N.P.B.A., 1957) and Northern Ireland (Heaney, 1962) and in three feeds per day in Denmark (Clausen & Thomsen, 1957). In the Republic of Ireland (Department of Agriculture, 1960) three feeds per day are given on a scale which must involve little, if any, restriction in the later stages of fattening. Such practices have the object of discovering the strains which become too fat before they reach bacon weights. Many farmers, on the other hand, adopt some form of restriction during the later stages of fattening, with the object of finishing the pigs at the right stage of fatness, and thus of improving the grading of the carcases at the factory.

1. ‘Wet’ soil plants had greater tiller and leaf number, and were also taller than ‘dry’ soil plants.

2. The straw and grain dry weight, and grain weight as percentage of straw weight, were greater in ‘wet’ soil plants than in ‘dry’ soil ones.

3. Wet soil hastened the time of ear emergence.

4. Increasing the phosphate supply, on the whole, tended to increase the tiller and leaf number, weight of straw and grain and also hastened time of ear emergence.

5. Under ‘wet’ soil conditions high phosphate application is not necessary.

6. The yield of grain at high phosphate level of plants grown on ‘dry’ soil is significantly lower than the yield from those grown on ‘wet’ soil with low phosphate application. This suggested that under ‘dry’ soil conditions availability of nitrogen, as well as of phosphorus, is a limiting factor.

1. Twenty-one experiments were carried out in various parts of England and Scotland in 1959–61 comparing two or more of the nitrogen sources ammonium sulphate, ammonium nitrate, calcium nitrate and urea, combine-drilled in compound fertilizers for spring barley.

2. Ammonium sulphate and ammonium nitrate combine-drilled at rates from 35 to 105 lb./acre of nitrogen checked early growth slightly in some of the experiments, with no important difference between the two sources, which also gave similar grain yields.

3. Calcium nitrate and urea combine-drilled at 45 lb./acre of nitrogen had no large effect on early growth, while at 70 and 90 lb./acre both fertilizers seriously delayed brairding and reduced the plant population in many of the experiments, especially in eastern England. They gave lower yields than ammonium sulphate and ammonium nitrate in many of the experiments in which early growth was affected, and gave lower mean yields at all rates of application.

4. In eleven of the experiments, broadcast applications of two or more of the four nitrogen fertilizers were compared. All sources gave similar mean yields.

5. There was a slightly smaller yield from combine drilling than from broadcasting ammonium sulphate and ammonium nitrate, and a markedly smaller yield from calcium nitrate and urea.

1. Urea containing less than 1% biuret was compared with ammonium nitrate in field experiments on barley, sugar beet, winter wheat and grassland, and with ammonium sulphate on potatoes, in various parts of Great Britain in the years 1957–61.

2. When broadcast on the seed-bed for barley at rates supplying 25–45 lb./acre of nitrogen in twenty-five experiments, urea and ammonium nitrate gave similar mean increases in grain yield on acid soils, while on alkaline soils urea gave smaller increases than ammonium nitrate. The relative effect of the two sources was similar on light and heavy soils and in the east and west of the country.

3. When broadcast on the seed-bed for sugar beet at 50–60 lb./acre of nitrogen in nineteen experiments, mostly on alkaline soils in eastern England, no difference was detected between the mean increases in yield of sugar and tops from urea and from ammonium nitrate.

4. In twenty-two experiments on potatoes urea gave slightly smaller mean increases in yield of tubers than those from ammonium sulphate when applied at 40–60 lb./acre of nitrogen, with a larger difference at 80–120 lb./acre. No influence of soil pH, soil texture, region of the country or method of application (broadcast on the flat or over the open ridges) was detected.

5. When broadcast as spring top dressings in seventeen experiments on winter wheat, mostly in western England and Scotland, at rates supplying 34–45 lb./acre of nitrogen, urea and ammonium nitrate gave similar mean increases in yield of grain.

1. The results of a trial designed to investigate the effects of sheep excreta on sward growth and yield are described.

2. The quantities of plant nutrients excreted, and their distribution, by the grazing animal are discussed. An assessment is made of the value of excreta to pasture growth in the light of the results gained.

3. Under Boghall conditions, the return of excreta had little affect on sward output, the main effect was for the pasture to become progressively more grass dominant. In general, weather and soil nutrient limitation had a greater effect on nitrogen yields from the swards than did excreta. Recovery of excreta nitrogen would appear to be influenced by rainfall and the age of the sward.

4. On a soil inherently low in available potassium, it was found that this element and nitrogen both affected the pattern of herbage growth and composition when returned in excreta. Phosphorus return by the sheep was, however, of no observable value in either the levels of the element in the soil or in the herbage. It was found that rainfall and the botanical composition influenced the contents of mineral elements in the herbages.

5. Balance studies suggest that sheep grazed in small paddocks need adequate pre-conditioning before being moved into a trial. Only by this means can return of excreta reflect consumption of herbage. The limitations of small-scale animal grazing experiments are discussed.

1. A comparison was made of the carcass composition at 56 days of age of early-weaned pigs grown along predetermined growth curves to 30, 40 and 50 lb. live weight and of suckled pigs grown to 50 lb. live weight at 56 days of age.

Eight blocks of four pigs were slaughtered when 56 days old and comprehensive carcass dissections undertaken.

2. There were no differences in the proportionate weight of the joints or of individual bones between the suckled and early-weaned pigs weighing 50 lb. at 56 days of age.

The difference in the proportionate weights of the joints between the three groups of early-weaned pigs reflected the change in development which took place with increasing live weight. There was, however, no clear gradient of development along the bones of the limbs with increasing weight at 56 days of age.

3. The dissected joints (hams, shoulders, neck, pelvis and loin) from the early-weaned pigs which weighed 50 lb. live weight contained 0·5% less bone, 1·5% less muscle and 1·7% more fat than the carcasses of suckled pigs reared to 50 lb. at 56 days of age.

The dissected joints of the early-weaned pigs reared to 30 lb. at 56 days of age contained 1·4% more bone, 2·7% more muscle and 5·3% less fat than the joints of the early-weaned pigs reared to 40 lb. and 2·6% more bone, 5·2% more muscle and 8·8% less fat than the joints of early-weaned pigs reared to 50 lb.

The use of the percentage of crude protein in grass consumed by cattle as a means of estimating the nutritive value of grass was investigated. Regression equations expressing the correlation between crude protein and the digestibility coefficients of crude protein, organic and dry matter were calculated.

A close correlation between the percentage of crude protein in faeces and in consumed grass was found, and a regression equation was calculated.

1. Twenty blocks of four litter-mates were individually fed under standard conditions from 56 days of age to 200 lb. Each block consisted of three early-weaned pigs reared to 50, 40 and 30 lb. live weight, respectively, at 56 days of age and a suckled pig reared to 50 lb. live weight at 56 days of age.

2. There was no difference in the growth rate and feed conversion from 56 days of age to 200 lb. of the early-weaned and suckled pigs reared to 50 lb. at 56 days of age.

The age at 200 lb. of the 30, 40 and 50 lb. early-weaned pigs were 169·8, 176·8 and 182·7 days and the lb. of meal per lb. live-weight gain 3·3, 3·2 and 3·1 lb., respectively. A reduction in 56-day weight led to an increase in growth rate and feed conversion from 50 to 200 lb. live weight.

3. The conformation and composition of the bacon carcasses of the 50 lb. early-weaned pigs were not significantly different from the carcasses of the suckled pigs which also weighed 50 lb. at 56 days of age.

An extensive examination of the carcasses of early-weaned pigs showed that an increase in 56-day weight from 30 to 50 lb. live weight signifieantly reduced the weight of muscle present and significantly increased the amount of subcutaneous fat. The conformation of the carcasses was not affected.

1. In 1958, leys of late flowering red clover (S. 151) and of Italian rye-grass (S. 22) were undersown in barley. In 1959, yield and N and K uptake by clover, and by rye-grass given 0·0, 0·75 or 1·5 cwt. N/acre, were compared; rye-grass, given 1·5 cwt. N/acre, yielded most dry matter and removed three times as much K, but rather less N than did clover.

2. In 1960, wheat given 0·0, 0·25, 0·5 or 0·75 cwt. N/acre as a top-dressing measured residual effects of the N left by each ley. When no N was given to wheat, most grain and straw was obtained after clover ley and least after rye-grass given no N. The residual N from clover was equivalent to 0·14 cwt. N/acre as a fresh top-dressing; N given to rye-grass left only a small residue. When the wheat had 0·5 or 0·75 cwt. N/acre as a top-dressing, N given to rye-grass in 1959 decreased yield, probably because the rye-grass removed much K, but K uptake at harvest was independent of ley.

3. In 1960, leys of early flowering red clover (Dorset Marl) and of Italian rye-grass (S. 22) and a mixture of the two were under-sown in barley. In 1961, yields and N and K uptakes of clover, and of rye-grass given 0·0, 1·0 or 2·0 cwt. N/acre and of clover-rye-grass given 0·0 or 1·0 cwt. N/acre were compared. Rye-grass given 2·0 cwt. N/acre yielded most dry matter and removed one-third more K than did clover, but clover yielded one-third more N.

1. The sodium and potassium content of longissimus dorsi (lumbar), psoas major, rectus femoris, triceps (lateral head) and extensor carpi radialis from 6 pigs each at pork, bacon and manufacturing weights were determined: these varied significantly and systematically between muscles and between groups.

2. Since the concentration of potassium may differ by at least 30% between muscles, it is concluded that assessment of total muscle mass may be inaccurate if based on the integration ofγ-ray emission from 40K.

During the last 5–6 years, many visitors to this Institute have expressed interest in the apparatus used in the Nutrition Department to collect the total urine excreted by male cattle and sheep. The apparatus has now been in continuous routine use for over 6 years and can be regarded as very reliable. This note describes the equipment, shown diagrammatically in Fig. 1.

The correlation between chemical composition and nutritive value of grass fed to short-horn zebu steers in Uganda was investigated. The following regression equations were calculated from the experimental results and discussed in part I of this paper.

Dig. coef. of C.P. = 100·89 log c.p. – 44·45;

r = 0·9738, P < 0·001.

(For use when fodders of wide range of proteins are compared.)

Dig. coef. of c.p.= 5·14 c.p.;

r – 0·9339, P < 0·001.

(For quick calculation when only approximate figures are required.)

Dig. coef. of c.p. = 9·588 + 4·284 c.p.;

r = 0·9521, P < 0·001.

To be used between 4·5 and 17% of crude protein.)

% c.p. in grass eaten = 1·677 c.p.in

faeces – 6·93; r = 0·958, P < 0·001.

Dig. coef. of d.m. = 41·81 + 1·63 c.p.;

r = 0·9362, P < 0·001.

Dig. coef. of o.m.= 46·05 + 1·4152 c.p.;

r = 0·8851, P < 0·001.

The regression equations calculated from the experimental results in the present paper (part II) are as follows:

Dig. coef. of d.m. = 150·88 – 1·179 (c.f. + n.f.e.);

r = 0·9634, P < 0·001.

Dig. coef. of d.m. = 120·03 – 1·778 c.f.;

r = 0·721, P < 0·01.

Dig. coef. of o.m. = 142·50 – 1·045 (c.f. + n.f.e.);

r = 0·9320, P < 0·001.

t.d.n.= 129·39 – 0·9419 (c.f. + n.f.e.);

r = 0·9288, P < 0·001.

t.d.n. = 7·76 + 0·8192 dig. coef. of d.m.;

r = 0·9886, P < 0·001.

s.e. = 0·9367 dig. coef. of d.m. – 20·15;

r = 0·9832, P < 0·001.

s.e. = 120·80 – 1·104 (c.f. + n.f.e.);

r = 0·9468, P < 0·001.

s.e. = 99·44 – 1·868 c.f.

r = 0·7948, P < 0·01.

1. Four in vitro fermentation experiments, in duplicate, were carried out over 24 hr. periods, to estimate the production of v.f.a. and o.a from forages.

2. A new technique for determining the total organic acids produced in the rumen is described.

3. The o.a. produced in the earlier part of the fermentation are considerably higher than the v.f.a. but the difference then diminishes. There is practically no difference in the amounts produced after 24 hr.

4. Highly significant correlations were found between the in vitro production of v.f.a. or o.a. and d.e./kg. d.m., for all the roughages tested. Nonlegumes gave a more highly significant correlation than legumes.

5. Regression equations show that o.a. or v.f.a. were more accurate than in vitro cellulose digestion for predicting the d.e./kg. d.m. of non-legume forages. It is concluded that V.F.A. production in vitro is the best criterion in this respect.