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.

1. An experiment was carried out in summer when sheep do not normally shed their wool fibres to see if a poor diet would induce fibre shedding. Observations were then continued for a year to follow seasonal variations in the fleece.

2. The two experimental sheep lost about a quarter of their body weight during the nutrition experiment. Measurement of areas tattooed in the skin showed that there was a reduction of about 5% in these areas.

3. Histologieal observations of skin samples showed that there was very little fibre shedding during the nutrition experiment. This suggests that poor nutrition alone will not cause sheep to shed their fibres. More fibre shedding took place during the winter even though the sheep were well fed, suggesting a seasonal stimulus for shedding.

4. ‘Brushes’ which are normally formed when fibres shed in primary follicles were also seen in secondary follicles.

5. Observations were made during the nutrition experiment of the blood vessels in the skin and glycogen in the outer root sheaths of the follicles. No changes were seen in either the numbers of vessels, or the amount of glycogen present.

6. The weight of wool produced per unit area per day was determined at each sampling time during the whole year. The experimental sheep behaved differently from the controls in their wool production during the nutrition experiment. Thereafter all sheep behaved the same, and seasonal fluctuations in wool production were found.

7. The mean length and mean diameter of the wool produced was determined at each sampling time throughout the year.

1. By separating the sources of variability in an experiment involving haematological observations it has been shown how to estimate the usefulness of repeated observations on each animal.

2. In the illustration provided it is concluded that when monozygous twin calves are used, random variability accounts for so much of the total variability that a great improvement in accuracy can be achieved by taking repeated observations on each animal. When unrelated calves are used, little additional accuracy is obtainable by taking more than about three observations on each.

3. It is shown that, in consequence, the relative efficiency of monozygous twin and unrelated calves is likely to vary, depending upon the number of observations on each animal. Thus, to benefit fully from the increased efficiency offered by monozygous twins, more observations are required on each animal than in the case of unrelated animals.

4. Although the figures refer to haematological measurements on calves, the statistical method evolved is of wider application.

1. In an experiment conducted with eight pairs of monozygous twin heifer calves aged from 7 to 9 months, it was shown that the mean haemoglobin concentration of those reared on a high plane of nutrition was higher than the corresponding value of those reared on low-plane rations.

2. The relative anaemia of the low-plane animals was microcytic but normochromic in type. Its cause must await further investigation, but these features would not be inconsistent with a deficiency of iron.

3. For this type of haematological study, monozygous twins proved more efficient than unrelated animals, as shown by the smaller variability within than between pairs.

4. Day-to-day variation in the same animal must be considered an important possible source of sampling error.

Glover & Robinson (1953) have recently criticized the use of a transformation in calculating confidence limits of monthly rainfall, and have suggested that the technique is complicated and even misleading. They contend that the use of unadjusted monthly data leads to no serious discrepancies. If this were in fact so, there is no doubt that much time and effort could be saved. It is therefore desirable to compare the two techniques, and to set out against the recorded data the predictions obtained from them.

1. Superphosphate, at two levels and three intervals of application, was applied to calcareous downland pasture grazed by sheep over a period of 3 years.

2. At the high level, total dry-matter and crudeprotein yields were higher from a single initial application and from thrice-yearly applications than from annual applications.

3. At the high level, mean herbage phosphate content and total phosphate yield were higher following a single initial application than when superphosphate was applied at shorter intervals.

4. Superphosphate increased the cover of grasses and legumes and reduced the cover of herbs.

5. Superphosphate affected the cover of individual species in the following manner:

(a) Favourably: Dactylis glomerata, Festuca rubra, Arrhenatherum elatius, Poa trivialis, Holcus lanatus, Lolium perenne and Trifolium repens.

(b) Unfavourably: Agrostis stolonifera, Leontodon spp., Prunella vulgaris, and other minor herbs.

(c) No measurable effect: Poa pratensis, Plantago lanceolata, Ranunculus bulbosus and Crepis capillaris.

1. The relationship existing between the gross digestible energy content and the chemical composition of twenty-four silages has been studied with nine Cheviot wether lambs over a period of 8 months.

2. Silages were made from grassland herbage and varied widely in the chemical composition of the ingoing material.

3. Each silage was fed to a group of three lambs for a 10-day preliminary- and a 9-day collectionperiod. Faeces and urine were collected in metabolism crates.

4. The silages were analysed for volatile acids and bases, for proximate nutrients and for some of the more precise chemical constituents as suggested in the scheme of analysis of Ferguson (1948).

5. A close relationship existed between the gross digestible energy contents of the silages and the lignin (Ellis) content.

6. The most accurate prediction of gross digestible energy was obtained by taking into account the content of lignin (Ellis), cellulose (Crampton & Maynard) and crude protein, in the silage.

7. In the case of hays (Walker & Hepburn, 1955) no increase in the accuracy of predicting gross digestible energy was obtained by estimating the lignin and cellulose content, rather than crude fibre alone. However, with silages the results give support to the opinion of Mitchell (1942) and Schneider et al. (1951) that analysis for more precise chemical constituents will increase the accuracy of predicting digestibility.

8. Crude fibre and cellulose were not related in any fixed way with the digestibility of energy. Crude fibre itself was digested to some 80% compared with 62% in hays.

9. Metabolizable energy was closely related to digestible energy.

10. The starch equivalents of the silages were calculated by conventional methods and also from the content of gross digestible energy.

An examination was made of wool and skin samples from sheep being dosed with sodium fluoride, and from other sheep acting as controls, from March 1953 to March 1954. It was evident that the sodium fluoride caused the wool to grow shorter, finer, less crimped and to become less lustrous; less wool grease was produced, and it seemed that in certain samples from one sheep tenderness of the fibres had been caused. There was a greater occurrence of capsules associated with follicles in skin samples from the dosed sheep, suggesting that the sodium fluoride might have been the cause of these. The number of capsules in one sample was large enough for the details of possible stages in their development to be described. There were apparently no other abnormalities in the skin and follicles, and follicle counts suggested that the sodium fluoride had not influenced the percentage of shedding fibres. Information was gained about the normal changes in the percentage of shedding fibres through the year.

Semen samples were collected from buffalo bulls by a.v. at intervals of 24, 12, 8 and 2 hr., four consecutive ejaculates being collected for each bull in every treatment. Semen qualities were measured in fresh and stored ejaculate at 4° C. for 48 hr.

1. (a) In fresh semen, the average initial values were 3·12 ml. for volume, 645 × 103 for concentration per cubic millimetre, 2134 × 106 per ejaculate, 7·25 for motility, 80·1% for live spermatozoa and 21·1% for abnormals.

(b) Volume, concentration and percentage of live sperm were not affected by successive ejaculations.

(c) Motility started to decrease after the third collection in most cases.

(d) Percentage of abnormals was highly affected irrespective of interval of collection.

(e) When the interval of collection was short, enlarged middle piece of spermatozoa and detached galea capitis were observed.

2. (a) In stored semen, the average values were for motility 3·12%, for live sperm 64·5%, and for abnormals 27·4%.

(b) Storage caused a decrease in motility and an increase in percentage of abnormals, while it had no effect on percentage of live sperm.

(c) The rupture of head membrane of spermatozoa was observed in stored semen.

A method for measuring the rate of passage of meal through the alimentary tract of pigs by feeding a stained marker is described. The results are given of sixty-four experiments made under standardized conditions on four fattening pigs with live weights ranging from 49·9 to 185·5 lb. and six experiments on a sow weighing 500 lb.

Results were expressed by means of excretion curves. These were sigmoid in shape and from them a value termed R, the mean retention time (hr.) of all the stained particles in the alimentary tract, directly proportional to the area to the left of the curve, was calculated.

In the fattening piga the first appearance of the marker in the faeces occurred 10–24 hr. after feeding, and the mean 5 and 95% excretion times were 21 and 53 hr. respectively. The marker was completely excreted after approximately 80–90 hr. The R value averaged 34·2 hr.

A marker fed at the morning feed (9 a.m.) had earlier 5 and 95% excretion times and the R value was significantly smaller.

There was no statistically significant relationship between the R values and live weight, digestibility of the dry matter of the ration or the dry-matter content of the faeces.

In the sow the 5 and 95% excretion times were 38 and 68 hr. respectively, and the R value averaged 51·1 hr.

Counts of stained particles in the intestines of two of the pigs after slaughter showed that food was delayed mainly in the large intestine.

When planning a factorial experiment, it is often desirable (as pointed out by Yates (1937)) to include certain extra treatments falling outside the usual factorial scheme. I discuss here the exact analysis of an experiment of this type. Only standard principles of experimental analysis are involved, and the full exact analysis is not always required in practice, but the example may illustrate techniques that are useful in investigating more complicated designs that are sometimes encountered. I am grateful to the late Dr E. M. Crowther and Miss B. Benzian, of the Chemistry Department at Rothamsted, for discussion of the problem and for providing data for the illustrative example.

1. Eighteen determinations of the energy retention of six sheep were made when they were given the same batch of dried grass in the form of chopped material or as cubes. The cubes were made following hammer milling to a medium and fine particle size. The fasting heat production of each sheep was also determined, following subsistence on a standard ration.

2. Agreement between determinations of energy retention calculated from the carbon and nitrogen retentions and from the energy exchange was good. The mean discrepancy was 4 Cal./24 hr.

3. There were no statistically significant differences in energy retention as between the three materials at either a low (600 g./24 hr.) or a high (1500 g./24 hr.) level of feeding. Calculations of net energy/100 Cal. of food ingested showed that higher values occurred at the lower level of feeding. Standard errors of the means were small, about ±3% of the determined values. Further analysis showed that no large differences in the net energy value of the materials would appear within the normal feeding range, but slight extrapolation of the data indicated that the cubes would be superior at high feeding levels.

4. Faecal losses of energy were considerably greater when cubes were given and methane losses were much smaller. Individual sheep which showed low methane losses also showed high faecal energy losses. Faecal losses of energy were smaller at the lower feeding level. Urine energy losses were unaffected by the amount or physical form of the food given.

5. Heat losses were greater at the higher nutritional level and were considerably less for cubes than for chopped material. Constancy of net energy value in this study thus involved compensation of high faecal energy losses by low losses of energy as heat and methane.

6. The determinations of the digestibility of the carbohydrate fractions of the grass showed that a fall in the digestibility of the structural components of the cell was the major factor causing increased faecal losses. The digestibility of intracellular constituents fell very much less.

7. It is shown that evaluation of the grasses in terms of metabolizable or digested energy does not place them in their correct physiological order of nutritive value, and that estimates of nutritive value using Kellner's and other factors do not give their true nutritive worth.

8. It is pointed out that physical factors, which change the rate of passage of food through the gut, change the rate and nature of the microbial fermentation, and cause variation in the mechanical work involved in prehending, masticating and cudding food, are as important as the chemical composition of the food in determining its nutritive value.

The fleeces of Border Leicester, Romney Marsh, Lincoln and Dorset Horn ewes which were confined for 3 years to copper-deficient pastures at Robe, in South Australia, have been studied.

As the copper status of the untreated ewes fell, their fleeces revealed abnormalities identical with those encountered in similarly copper-deficient Merino and Merino crossbred sheep.

The crimp characteristic of each breed was lost and straight, ‘steely’ fibres were produced. The capacity for crimp formation returned immediately when the copper status was restored.

Ewes which received regular copper supplements grew normal wool throughout the experiment. Supporting analytical data are presented.

The absence of this specific lesion from the fleeces of copper-deficient British breeds of sheep elsewhere is discussed.

1. The results are presented of two series of digestibility trials. The first series consists of six grass hays, cut at different stages of growth, and two legume hays cut at the flowering stage. The second series consists of trials using seven species of grasses at the ‘standing hay’ stage.

2. Good-quality grass hays are obtained from grasses at the flowering stage. More mature grasses yield poor- or very poor-quality hays of low-protein content.

3. The legume hays were of good quality, being particularly high in digestible protein.

4. The grasses at the ‘standing hay’ stage are generally of poor feeding value, Brachiaria brizantha, a drought-resistant species, being the best of the seven studied.

5. From these results a tentative conclusion is drawn that, during the dry season, the extensive grazing areas of East Africa are capable of providing, at the most, for the maintenance requirements of ruminants.

1. An examination has been made of the results of a number of experiments on the feeding of fodder beet to fattening pigs.

2. When beet is introduced, the daily energy intake and hence the growth rate are slightly reduced.

3. The value of beet as a replacement for meal, neglecting the reduction in growth rate, may be assessed satisfactorily from a knowledge of the dry matter content of the beet and of the starch equivalent of the meal, using the average values given by Woodman (1954).

4. Where beet is used to replace meal, the available digestible protein is reduced. It is possible that the addition of protein-rich supplements to the ration will improve the performance of the pigs.

5. The effects of beet on carcass quality are not clear. The Danish reports examined indicate slightly lower quality, but the English reports similar or slightly higher quality.

1. 863 female pigs, mostly sows discarded from commercial herds in East Anglia, and sold for slaughter, were examined when killed and the condition of the reproductive tract was related to the animal's reproductive history when it was known.

2. Anatomical abnormalities of the reproductive organs, other than cystic ovaries, were found in sixteen animals (including two gilts) and the abnormality involved the ovary in eight of them. At least two of them were brought to notice because of the abnormalities so that the number seen affords a maximal estimate of the incidence of this type of aberration in the pig population from which the sample was drawn.

3. A wide variety of ovarian cysts was found, often within a single pair of ovaries. It is suggested that all the ‘types’ of cyst described here and elsewhere are different degrees of the same kind of aberration, the morphological form being determined by the stage in the ovulation process reached by the follicle (or corpus luteum) when overtaken by the physiological breakdown responsible for the cystic distension.

4. As none but slight degrees of cystic abnormality were found in pregnant animals, these were used as a criterion to distinguish between slight and severe degrees of cystic abnormality, the latter in all probability associated with sterility, and encountered in about 10% of the sows in the sample.

5. Slight degrees of cystic abnormality do not appear to be associated with the production of small litters; pregnancy appears to be either unaffected or else precluded altogether.

6. The reproductive organs of more than half of the sows which were discarded for reproductive failure were found to be normal, and in many cases the failure could only be attributed to chance. A large proportion of the sows discarded as sterile were culled after their first litter. The preponderance of reproductive failure at this stage could not be attributed to ovarian cysts.

7. There was a marked seasonal variation in the incidence of ovarian cysts, the proportion of animals with some degree of cystic abnormality being twice as high in the spring months as in the autumn. The variation is thought not to be due to sampling errors alone. There was no seasonal variation in the average number of corpora lutea or of embryos.

8. The observations are discussed in relation to work of a comparable nature done elsewhere, particularly in U.S.A. Some striking divergences are apparent. Large cysts, commonly found in pregnant animals in America, did not appear to interfere with gestation and were evidently formed during pregnancy. Such cysts were never observed in pregnant animals in the English material, where only nine out of 130 pregnant animals showed any degree at all of cystic abnormality, by no means severe in any of them, and not involving ‘large’ cysts. Marked enlargement of the clitoris was found to be associated with one type of ovarian cyst in America but was not observed in England. A greater diversity of cystic abnormality was recognized in the present work than in American studies, and such histological and endocrinological work as has so far been done has given results somewhat different from those recorded in America.

9. There is strong evidence that oestrus may fail to occur in the sow, so that the animal cannot be served. The condition is probably reported more frequently than it occurs, however, since reliance is often placed on examination alone for the detection of heat, without using a boar.

10. There is some evidence that oestrus and ovulation may get out of step in some animals and it is possible that the cause is related to that of ovarian cysts. Oestrus and service may occur during pregnancy.

In field experiments on vegetable crops dressings of appropriate fertilizers were placed 2 in. to the side of the seed and 2–3 in. below the soil surface, and compared with the same amounts of fertilizer broadcast and worked into the surface soil. The work was carried out on ordinary arable land carrying rotations which included vegetables.

Placing fertilizer gave higher yields of cabbage, lettuce, beetroot, onions, broad beans, runner beans and maize, than broadcasting. Fertilizer, however applied, had no regular effect on the yield of french beans.

Both placed and broadcast fertilizer were tested at two rates of dressing. On average of all experiments on each crop, placing fertilizer at the low rate gave higher yields than broadcasting at the high rate. Broadcast fertilizer had little effect on yields of runner beans and broad beans, while placed dressings gave marked increases.

In two-thirds of all individual experiments placing gave higher yields than broadcasting, and in one-third of the experiments placement was significantly better than broadcasting. There were no instances of significantly higher yields from broadcasting as compared with placing.

Placing fertilizer made most of the crops grow more rapidly in the early stages than broadcasting, this improvement being often reflected in earlier maturity. For cabbage, lettuce and runner beans the relative gains from placing, as compared with broadcasting fertilizer, were much higher at the first than at the second harvest.

By drilling fertilizer beside the seed of vegetable crops grown on ordinary soils, it is possible to economize in the dressings needed. In addition, some crops having placed fertilizer may be ready for market earlier. These advantages may be very profitable where high-value crops are grown and will justify the purchase of special placement drills.

A small series of field experiments on established Brussels sprouts and autumn-planted cabbages compared mid-season top-dressings of nitrogen fertilizer broadcast by hand over the whole soil surface, with dressings placed at one point beneath the surface and near to the plants. The dressings used had practically no effect on yields of Brussels sprouts. Top-dressings broadcast in spring increased yields appreciably in two experiments on cabbage, and at both centres placing gave lower yields than broadcasting.