Journal of Agricultural Science, 47

M. L. Ryder. The pre-natal development of follicle population in the Romney lamb (Vol. 47, Pt. 1)

M. L. Ryder. Observations of nutritional and seasonal changes in the fleeces of some Masham sheep (Vol. 47, Pt. 2)

Will readers please note that the plates illustrating the above articles have been incorrectly placed. The present Plate 7 facing p. 144 should be Plate 1 facing p. 10 and the present Plate 1 facing p. 10 should be Plate 7 facing p. 144.

To obtain records of individual animals' habits when a small herd is observed for long periods of time, several observers are essential. The errors between observers were so much less than those between animals and between periods of observation that for most purposes records made by a succession of different observers will be adequate.

The errors of observations at 1 and 4 min. intervals, using the grazing records of ten animals, were 3·20 and 7·36% of the mean respectively. The latter figure being of sufficient accuracy for practical application, it is concluded that the 4 min. interval is suitable for records of a major habit.

The errors for the minor habits were large relative to the mean time occupied on them, but still reasonable in relation to the purposes for which work of this sort would usually be required.

Previous studies on the development of follicle population in relation to the growth of the fleece have, except for the Merino, been mostly post-natal. The pre-natal study of follicle development in some British sheep by Wildman (1932) was mainly qualitative, as also was the work of Carter (1943) in the Merino. The latter study was, however, followed by some numerical work on the same breed (Carter & Hardy, 1947). Figures were given for the follicle density per unit area and the ratio of the number of secondary follicles to the number of primaries at different ages. The present study therefore helps to fill a gap in our knowledge by considering numerically the pre-natal stages of development in the English Romney, a breed which is important in the northern hemisphere and which might be considered to be comparable with the Romney of the southern hemisphere.

When the leaves of sugar-beet crops were sprayed on six occasions in late September and early October with 100 gal./acre of a 3% solution of ammonium nitrate or equivalent urea, in two experiments about 70% of the nitrogen was recovered in the plants in mid-October, compared with 40% recovered from applications of the same amounts of fertilizer to the soil at the same times. In a third experiment the recovery from similar sprayings with urea solution was less than 40%, but very little nitrogen was absorbed from soil dressings, so that the difference between the recoveries from spray and soil applications was nearly the same as in the other experiments.

Nitrogen per cent of dry matter in all parts of the plant was increased by the sprays. More than half of the nitrogen absorbed from the sprays was in the leaf laminae, and the remainder was equally divided between petioles (including crowns) and roots. Between 20 and 30% of the nitrogen supplied in spray in the first two experiments was converted to protein in the leaf laminae, and half of this was present as soluble protein precipitable by trichloracetic acid, a fraction that is extracted in the largescale preparation of leaf protein.

Spraying slightly increased the dry-matter yield of the tops, but not of the roots. It reduced the sugar content of the roots by about 1% of fresh weight. In one experiment it had no effect on sugar yield; in the others it caused losses of 2 and 5 cwt./acre.

The recovery of nitrogen in the tops from a single low-volume spraying (12½ or 25 gal./acre) with nearly saturated urea solution was about the same as from repeated high-volume sprays supplying the same total amount of nitrogen, but in the roots it was higher from the single than from the repeated sprays.

A study has been made of variations in the shrinkage from the live pig to the carcass and from the carcass to the side of Wiltshire bacon. Most of the variation occurs at the first stage when the losses have a variance of 17·67 lb. compared with only 4·59 lb. and the second stage. Similarly, breed differences were found at the first stage, Wessex and Essex pigs giving 1·1 and 2·7 lb. more carcass respectively than the Large White pigs, but not at the second stage. On the other hand, differences between litter groups were found at both stages.

Correlations made between carcass measurements and yield of carcass and bacon were generally found to be small and positive. Antagonisms were indicated between quantity and quality of bacon, in particular by positive correlations between thickness of back-fat and weight of carcass, and between a desirable proportion of cuts and losses on slaughter. The problem of deciding the relative attention which should be paid to various carcass characteristics is discussed and the need for an index of total carcass merit is pointed out.

Seasonal variations in the contents of organic and inorganic constituents of three East African grasses, Bothriochloa insculpta, Chloris gayana and Brachiaria dictyoneura are reported.

Protein content is closely associated with rainfall and the stage of growth of the grasses. Protein content of from 15 to 20% is maintained for a short time only, at the beginning of the rainy season. During the dry season the values fall to 4–5%.

Even in the vegetative phase the fibre contents are relatively high, 23% being the lowest figure recorded.

A common feature of the grasses is a high content of silica, which may amount to more than 10% of the dry matter.

The phosphorus content of the grasses is low, ranging from 0·65% P2O5 in young grass during the rainy season to 0·13% during the dry season.

1. The results of nine digestibility trials on three East African grasses, using sheep as experimental animals, are reported.

2. In five of the trials Bothriochloa insculpta, at various stages of growth during the season, was used. Chloris gayana (Rhodes grass) was used in two trials, as was Pennisetum clandestinum (Kikuyu grass).

3. The results are discussed and are compared with other results from East Africa.

4. P. clandestinum has a high digestible protein content and is highly digestible in the early stages of growth, and maintains its high protein content when 9 to 12 in. in height.

5. Bothriochloa insculpta and Chloris gayana are moderately highly digestible in the-young stages but are relatively low in digestible protein. As growth ceases during the dry season the digestible protein content falls more rapidly than the starch equivalent with consequent widening of the nutritive ratio.

6. It is suggested that the differences between Pennisetum clandestinum and the other grasses may be due to its predominantly vegetative habit.

1. The partition of the egg into shell, yolk, thick and thin albumen has been determined for eggs from pullets, 1-year-old hens and hens aged 6–10 years.

2. The proportion of thick albumen increased, and that of the thin albumen decreased, with advancing age of the hen.

3. It is suggested that these observations may be explained by the action of one or more of the following agencies: an increase in the amount of ovomucin relative to the amount of albumen; an impairment of the adrenal function; and a reduction of the period of time spent by the egg in the shell gland.

The results of 8 days' observations with ten animals, under both free-grazing and night-paddock systems, are given. These results are discussed in relation to changes in the food consumption of the animals. The indications are that when the animals are on rough grazing, the pattern of behaviour is not influenced by the night-paddocking system, but that the food consumption of the animals is affected by the relative abundance of herbage in the day and night enclosures. In this trial one comparison shows a significant reduction in average ruminating times by 1 hr. without any effect on the grazing time, when the herbage was scarce in the night paddock; and in the other comparison, when there was more herbage in the night paddock than in the day paddock, the food consumption, as indicated by the ruminating times, was unaffected, but at the same time the animals needed to graze 1 hr. more under the free-grazing conditions than under the night-paddocking system.

1. An experiment comparing the growth and productivity of six varieties of lucerne representing a wide diversity of ecological conditions grown in association with S 37 Cocksfoot, S143 Cocksfoot and a commercial cocksfoot/timothy mixture is described and the results discussed.

2. Variety of lucerne had a marked effect on establishment, persistence, recovery from defoliation, early spring growth, yield of total dried produce, proportion of lucerne in that produce and on yield of nitrogen.

3. There was no evidence of differing degrees of compatibility of varieties of lucerne with the three strains of grass used.

1. An investigation is described in which the effect of both technical and physiological factors on muscle fibre size was examined. Size was determined by measuring the cross-diameter of 16,450 individual fibres by means of an ocular micrometer. In cases where an animal was represented by a single muscle sample, 100 fibres were measured, otherwise fifty measurements were recorded per sample.

2. The material consisted of muscle samples always taken from the same position along the length of the muscle and immediately afterwards fixed for varying periods of time in 10% formalin. Samples were obtained from various sources, principally from experiments conducted in the past at the School of Agriculture, Cambridge, but also from slaughterhouses and contemporary investigations. These latter samples were treated in the same manner to ensure consistency.

3. From the results of an investigation on the effect of formalin fixation on muscle fibre diameter, carried out on samples obtained from a mature buck rabbit, it was tentatively concluded that although shrinkage does occur the effect is only slight; the difference between measurements of fresh compared with fixed fibres being non-significant statistically. Shrinkage apparently ceased as soon as the fixative had penetrated the sample, since no further changes could be detected after prolonged fixation.

4. The same material was used to study the effect of heat. Application of heat (boiling) for a matter of seconds caused an immediate, highly significant, shrinkage.of individual fibres, but continued heattreatment resulted in no further changes. Though heat caused the fibre to lose its characteristic striated appearance, there were no signs of fibres disintegrating or of the sarcolemma becoming detached from its protoplasmic contents.

5. From the results of previous investigations it was deduced that the measurement of 100 fibres per sample provides a reliable mean value and a representative indication of the dispersion in a given muscle, or at a given age. Results obtained in the present study demonstrated a slight tendency for larger fibres to be measured as the period of observation proceeds, a factor which should be guarded against.

6. The effect of species on muscle fibre diameter was examined by comparing fibres of m. gastrocnemius of the rabbit, the pig, the sheep and cattle at birth and maturity. Only male animals were included in the comparison. It was shown that no relation exists between muscle fibre size and body size at either age. At birth the rabbit and sheep had rather similar-sized fibres, while those of the pig and cattle were respectively smaller and larger in diameter. At maturity the pig had the largest fibres, followed in decreasing order by the rabbit, cattle and sheep. The size of muscle fibres at maturity was accounted for by the degree of post-natal development in body weight of the particular species.

7. The effect of breed was studied on two groups of steers, the one consisting of Dairy Shorthorns and Dairy Shorthorn-crosses, and the other of Friesians and Friesian-crosses. Samples were available from m. longissimus dorsi for each of thirty-four animals: 100 fibres were measured per sample. The Friesians and their crosses had significantly thicker muscle fibres than the pure- and cross-bred Dairy Shorthorn steers. The largest differences existed between the respective pure-bred animals; differences between Friesian × Angus and Dairy Shorthorn × Angus, and Friesian × Hereford and Dairy Shorthorn × Hereford, though fairly distinct, were, however, not statistically significant.

8. The effect of age was investigated on a group of forty-one lambs of different nutritional status and sex, and ranging in age from birth to 290 days. Muscle fibre diameter was shown to increase in general with age, while a consistent decline in the coefficient of variation was regarded as indicative of the fact that muscular growth during post-natal life occurs essentially by hypertrophy of individual fibres, there being no increase in the number of fibres after birth.

9. Correlating changes in muscle fibre diameter with corresponding changes in weight, indicated that muscular growth is primarily a function of physiological age, and not strictly one of chronological age. Though highly significant correlations were established between mean fibre diameter and body and carcass weights, the strongest correlation was shown to exist between the former variate and muscle weight. However, a correlation of an even higher order was obtained between the square of muscle fibre diameter and muscle weight. It was attempted, by means of linear regressions, to indicate the contribution of length growth of the fibres to increments in muscle weight. The need for further investigation is, however, apparent; insufficient data in the present study made it impossible to elucidate this point altogether.

The relationships were confirmed by an analysis of twenty lambs of the same breed, all slaughtered at 112 days of age; the heavier lambs had larger fibres than their lighter counterparts, very nearly proportional to differences in weight of muscle.

10. Sex differences in muscle fibre diameter could very nearly be accounted for on a basis of muscle weight alone at birth and at a carcass weight of 13·6 kg. At 290 days of age, high-plane wethers had but slightly thicker fibres than their female counterparts, despite a significantly heavier musculature. This was ascribed to differences in length of muscle (as shown by bone measurements), and also to differences in composition of the muscle. The results of chemical analyses were presented to prove that the muscles of wethers at that age contain greater amounts of intra-muscular (chemical) fat, hence the apparent increases in the weight of muscle could not be accounted for by an increase in the diameter of component fibres.

11. The effect of nutrition was studied in both lambs and mature ewes and shown to influence muscle fibre diameter appreciably at all ages. However, at birth the differences, though in favour of the high-plane lambs, were not significant statistically, probably due to small numbers in the respective groups. Muscle fibre diameter of mature ewes on a supermaintenance diet increased in proportion to increases in total muscle, while on a submaintenance diet the opposite effect was found. It appeared that continuation of the supermaintenance treatment would have resulted in but little additional changes in the diameter of fibres, while prolongation of the submaintenance treatment probably would have caused considerable further shrinkage of individual fibres.

12. The effect of the individual muscle was studied by comparing absolute and relative development of fibres of m. longissimus dorsi, m. rectus femoris and m. gastrocnemius. At birth m. gastrocnemius possessed the largest fibres and m. longissimus dorsi the smallest. On the whole, fibres of m. longissimus dorsi, the muscle being situated in a late maturing part of the body, showed greatest relative increases during post-natal life, while those of m. gastrocnemius, an earlier maturing muscle, increased latest. On an average, m. rectus femoris had larger fibres than m. longissimus dorsi at maturity, those of m. gastrocnemius being the smallest in absolute measure. Comparing the relative degree to which different muscles develop under high and low planes of nutrition, muscle fibre measurements indicated that the low-plane animals at a chronological age of 290 days, resembled their 60-day-old high-plane counterparts in anatomical development.

In mature animals, the early maturing gastrocnemius appeared to benefit most initially from a supermaintenance diet; however, during the later stages of the experiment, m. longissimus dorsi fibres showed the greatest relative increases, followed in order by m. rectus femoris and m. gastrocnemius. On the submaintenance ration, m. longissimus dorsi fibres appeared to be reduced in size at a greater rate initially than those of the other muscles. Individual variation, however, made it extremely difficult to generalize during subsequent stages.

13. From width and depth measurements on m. longissimus dorsi (or ‘eye muscle’) recorded at the junction of the thoracic and lumbar vertebrae, it was shown that width is the earlier maturing dimension and less affected by nutritional factors than depth.

Though significant relationships were found between mean fibre diameter and both muscle width and depth, the latter dimension was the more strongly correlated with changes in thickness of fibres.

14. It has been suggested that work of this nature might provide a suitable basis for estimating the amount of muscular tissue in a carcass; such a relationship would be of great assistance to students of meat physiology who have to resort to laborious dissection techniques for data on carcass composition. It is obvious, however, that factors such as species, breed, and possibly sex, would have to be considered in an attempt to establish a relationship of this kind. Furthermore, the effect of the individual muscle used for test would demand consideration, different muscles being influenced to varying degrees by age and nutrition. A late maturing muscle probably would furnish the most reliable criterion; in the light of evidence produced by this study, m. longissimus dorsi sampled at the junction of the lumbar and thoracic regions has been suggested as most suitable.

1. A series of experiments, involving the use of three hundred and forty Rhode Island Red x Light Sussex day-old cockerels, was carried out to determine (a) the influence of floor type on the incidence of perosis, and (b) a method of lowering the high incidence of perosis which may occur when chicks are fed the experimental diet no. 124 originally described by Dam et al. (1951).

2. It was found that the incidence of perosis was about 60% higher in groups of chicks raised on wiremesh floors than in groups of chicks similarly raised on wooden floors.

3. Neither the area of the floor space nor the level of manganese in the diet influenced the incidence of perosis.

4. When the calculated choline content of the diet was 500 mg./kg. the incidence of perosis was 60% but when it was raised to above 800 mg./kg. the incidence fell to about 15%. This could not be reduced further by further increasing the choline content.

5. Since the rate of body-weight gain increased as the choline content of the diet was raised to 1400 mg./kg. it is suggested that diet no. 124 may be improved from both the points of view of perosis prevention and of growth rate if the choline content is raised to 1500 mg./kg. of diet.

Using two inbred lines of Brown Leghorns, B and I, a backcrossing experiment was set up to test whether inherent rate of production was a simply inherited trait. Female progeny of each generation, selected for high rate, were mated to males of the B (lower rate) line. The pullet records now available, for 2 full years' production and to 31 March in the third generation, have yielded unexpected results.

In each backcross generation mean egg production has been at least as good as in the better parent, line I. This is not wholly accounted for by the behaviour of rate, since measurements of the trait in the cross approximate to the average of the two inbreds in each year. High viability and absence of very poor layers were also determining factors.

Backcross egg weight remained intermediate between the widely differing parent lines, and the cross produced the greatest total weight of egg material in each set of comparisons. Body weight was also intermediate, but sexual maturity was comparable with that of line B.

It was deduced that selecting the backcross breeding females for high rate had led to the retention of a greater proportion of the original I genotype than would normally have been expected, and so maintained continued heterozygosity in succeeding generations.

Practical implications of the results and interpretation are discussed.

Thirteen experiments on spring cereals were carried out from 1952 to 1954 to compare broadcasting with combine-drilling for nitrophosphate and for mixtures of superphosphate plus equivalent nitrogen. Broadcast nitrophosphate was of little value; drilled dressings were much more effective. Superphosphate drilled with the seed produced consistently higher yields than broadcast superphosphate. Superphosphate plus equivalent nitrogen gave higher average yields than nitrophosphate both when broadcast and when drilled. When the dressings were broadcast, superphosphate was markedly superior to nitrophosphate, but when the fertilizers were drilled with the seed, average yields with superphosphate were only a little higher than with nitrophosphate.

Nitrophosphates may be substituted for mixtures containing water-soluble phosphorus for cereals providing that they are drilled with the seed. Since nitrophosphates do not make cereals grow as rapidly as does superphosphate, even when drilled with the seed, such materials may give poor crops in conditions where the plants need a rapid start. The nitrophosphate tested contained rather more than one-quarter of its phosphorus in water-soluble form; the improved early growth observed where nitrophosphate was combine-drilled may have been largely due to this fraction of the fertilizer.

The ability of various high polymers to stabilize soil crumbs has been investigated using the sodium saturation technique. The soil used came from two plots on the Rothamsted classical fields, Barnfield and Hoosfield, which have received no fertilizer either organic or inorganic for 80 years, but whereas the former contains free CaCO3 the latter is acid.

The polymers tested were poly vinyl alcohol, sodium alginate, a vinyl acetate-maleic acid co-polymer, polyacrylic acid and a dextran. It was necessary to add 0·2–0·5% weight of the polymers in solution to the calcareous soil to produce crumbs of maximum stability, i.e. not dispersing the distilled water. The alginate, however, was effective only if the crumbs were first sodium saturated. With the acid soil, the amount of polyvinyl alcohol necessary for maximum stability was slightly reduced, corresponding to the lower clay content of the soil, whereas only one-tenth the concentration of the maleic acid co-polymer was required. Sodium alginate had no effect on the acid soil.

From the swelling pattern of the sodium-saturated crumbs in dilute salt solutions it was inferred that the non-ionic polymers, polyvinyl alcohol and the dextran form interlamellar complexes, whereas the carboxylated polymers are joined to the edge faces of the crystals. The presence of divalent cations is unnecessary for this edge linkage, as the polymers are equally effective when sodium ions only are present. It is suggested that the polymers form a series of hydrogen bonds with the exposed oxygen and hydroxyl atoms of the octahedral layer. Since these atoms have a greater tendency to co-ordinate a hydrogen ion as the pH is lowered, the carboxylated polymers would be expected to be more efficient on acid soils.

A simplification of the sodium saturation technique for the evaluation of potential soil conditioners is given.

Evidence obtained in the Agricultural Improvement Council Survey of Maincrop Potatoes 1948–50 and in experiments shows that yields in England and Wales are decreased by delay in planting after about 11 April at the rate of about 0·4 tons per acre per week. The effect is rather greater in years with fine springs, and on high-yielding fields.

In Rothamsted experiments the responses to dung and fertilizers were all greatly reduced when planting was delayed; between early April and late May the effects of dung, nitrogen and phosphate were halved, while that of potash was reduced by about 80%. The evidence on the responses of different varieties to early planting in English experiments is contradictory, except for an indication that higher yielding varieties respond better. Data from Craibstone suggest that, if bulk yield is the only criterion, ‘early’ varieties which make rapid growth early in the season have a later optimum planting date than maincrop varieties.

The effect of chitting seed at Craibstone is to increase yields by 1·7 tons per acre for March plantings, and by 2·5 tons per acre for plantings in mid-April and later. There is negligible loss of yield from sprouted seed at Craibstone for plantings delayed up to mid-April, but for unsprouted seed there is evidence of a gain from plantings a month earlier. Sprouted seed planted even as late as 1 May yielded as well as unsprouted planted two months earlier.