1946 Onderstepoort Journal of Veterinary Science and Animal Industry, Volume 21, Number 1, 1946

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Contentes Pages: Onderstepoort Journal of Veterinary Research, Vol ??, 19??

CONTENTS

*Volume 21: Number 1*

Section I: Virus Diseases

Further investigations into immunization of cattle against rinderpest	Mitchell, DT & Le Roux, PL	7

On the etiology of epizootic or infectious equine abortion	Henning, MW	17

Section II: Bacteriology

Avirulent anthrax vaccine	Sterne, M	41

Section III: Toxicology

Recent investigations into the toxicity of plants, etc., no. XV	Van der Walt, SJ & Steyn, DG	45

Section IV: Nutrition

The biological values of the proteins of some South African (whole seed) maize varieties	Myburgh, SJ	57

Section V: Pathology

The familial incidence of spontaneous osteopetrosis gallinarum	Coles, JDWA & Bronkhorst, JJ	79

Section VI: Wool Research

A study of the compressibility of wool, with special reference to South African merino wool	Van Wyk, CM	99

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A study of the compressibility of wool, with special reference to South African merino wool
(Pretoria : The Government Printer, 1946) Van Wyk, C.M.; Du Toit, P.J.
1. A study has been made of the resistance offered by wool samples to compression at 65 per cent. relative humidity and 70°F. (21.1°C.) temperature. The study has been based mainly on results obtained with the "Pendultex" instrument, designed by Henning (1934), but some additional determinations were made by means of a static cylinder and piston method. 2. A relation has been derived whereby the work done in compressing a wool sample in the "Pendultex" apparatus may be calculated from the number of swings during which the amplitude is reduced from one fixed value to another. 3. During the final constant cycle of compression by the static method, the pressure bears to the inverse cube of the volume a linear relation. With the dynamic method, the law is obeyed by the first compression. 4. The pressure-volume relation is discussed from a theoretical point of view, and it shown that the inverse cube law may be derived on the basis of certain assumptions. An approximate value of Young's modulus by bending can be calculated. 5. An empirical exponential relation between pressure and volume is considered. 6. It is concluded that since the density of packing is not uniform at low degrees of compression, results obtained at low pressures should not be considered together with those obtained at higher pressures, where the density of packing is more uniform and the pressure-volume relation follows the inverse cube law. 7. The method of expressing compressibility and resilience by means of the work done during compression and release is discussed. It is concluded that in the comparison of different wools the work done should be evaluated between volume limits. 8. A marked reduction in resistance to compression with the adsorption of water has been found. 9. Fibre length has no influence on the resistance to compression down to staple lengths of approximately one inch. 10. No correlation has been found between resistance to compression and fibre thickness. Although this result agrees with theoretical expectation, a highly significant partial correlation coefficient of +0.4330 is obtained when the effect of crimping is allowed for. It has been concluded, either that the fibre thickness has a positive influence which is masked by the crimping, or that fibre thickness is correlated with other factors, besides the crimping, which influence resistance to compression. 11. A highly significant positive correlation coefficient has been found between the resistance to compression and the number of crimps per inch. Possible ways in which the crimping can influence the resistance to compression are discussed. 12. For wools whose fineness and crimping agree with Duerden's standards, the resistance to compression increases with the quality number. Wools which are coarser than the crimps indicate have a higher resistance to compression than wools which are finer than the crimps indicate. 13. A significant partial correlation between resistance to compression and variability in fibre thickness has been found, but the coefficient is probably too small to be an important factor in breeding. 14. No correlation exists between the resistance to compression of a sample and the surface friction of its component fibres. It is concluded that the crimping is a more important factor in controlling fibre slippage during compression. 15. No correlation has been found between the resistance to compression of a sample and the tensile strength of the fibres. There are, however, factors which may influence one of these attributes and not the other, thus masking a possible correlation. 16. Samples presumed to have been selected for specific gravity by a sheep and wool expert were found to have been selected for resistance to compression. It is recommended that the term specific gravity should not be employed in wool practice. 17. Fibre thickness was the main factor to determine the harshness of two sets of samples as subjectively estimated. Resistance to compression and the non-wool fleece constituents were less important, though definite, factors. Harshness is, therefore, determined by the resistance to bending of individual fibres, rather than by the resistance to compression of the mass as a whole. An increase in tl1e surface friction of the fibres is responsible for the increased harshness of alkali treated wool. 18. Dipping wool in a lime-sulphur dip has no effect on the resistance to compression. 19. The variation in resistance to compression over the fleece has been studied and the major part of the variation found to be associated with the variation in fibre thickness and crimping. The results are discussed in relation to sampling in experimental work. 20. There is a highly significant negative correlation between the resistance to compression and the percentage clean yield of the fleece, and a highly significant negative correlation between percentage yield and number of crimps per inch, and no correlation between percentage yield and fibre thickness. 21. No difference in the average resistance to compression of fleece of rams and ewes could be found. It is concluded that differences observed in practice are duo to selection of stud rams for the ''substance'' of their wool. 22. On the average, the resistance to compression of the wool increases with the age of the sheep for the first four years, and the increase can be associated almost entirely with the increase in fibre thickness. 23. In a feeding experiment, the plane of nutrition had no effect on the resistance to compression of the wool in spite of a marked effect on the fibre thickness. 24. The distribution of resistance to compression is considered, and it is shown that South African Merino wool covers a range of at least 3:1 in this attribute. 25. The bearing of the correlations found on wool practice, with special reference to breeding, is discussed. 26. Possible results of breeding for "substance" are considered, and the desirability of breeding for this attribute is regarded with some doubt. 27. The importance of breeding for uniformity is stressed. 28. Support is given to a scheme of fleece recording in stud breeding, and emphasis is laid on the necessity of employing exact methods of measuring wool characteristics. 29. The establishment of a wool testing house in South Africa is recommended.
On the etiology of epizootic or infectious equine abortion
(Pretoria : The Government Printer, 1946) Henning, M.W.; Du Toit, P.J.
1. Two outbreaks of infectious equine abortions are reported; both with a very high abortion incidence. 2. In the majority of the abortions studied the foetal organs were found to be extensively invaded by S. abortus-equi but in others this organism could not be recovered from the foetus or after-birth. 3. Both donkey and horse mares were found to be susceptible, donkeys being on the whole more resistant than horses. 4. Abortion was successfully produced in both horse and donkey mares by means of (a) the oral administration of minced abortus-equi infected foetal organs (4 cases), (b) intravenous inoculation of collodion membrane or Berkefeld candle filtrates of these organs (9 cases, including 2 foals that died within 48 hours of birth) and (c) the oral administration of minced foetal organs that were culturally free from abortus-equi (one case). 5. The twelve aborted foetuses and the two foals that died within 48 hours of birth all presented lesions typical of infectious equine abortion. 6 . Abortus-equi was recovered from the organs of ten of the aborted foetuses and one of the dead foals, but not from two aborted foetuses and one dead foal. It was also isolated from the after-birth of two mares that had given birth to live foals (Nos. 704 and 732). 7. All the mares gave negative agglutination reactions at the time of abortion or parturition, but in those cases where abortus-equi was recovered from the foetus-not the foal-the reaction became positive in about 2 weeks. When the organs of the foetus were free from abortus-equi or when a live foal was born, whether its organs contained abortus-equi or not, the agglutination reaction of the mare generally remained negative. 8. The aborting mares did not suffer any ill effects as the results of the abortions and the after-births were expelled normally. 9. It is concluded that the primary cause of infectious equine abortion is an infecting agent that will pass either through collodion membrane, with the size of the pores 810 milli-micra, or through Berkefeld candles. 10. It was not possible to produce abortion in three pregnant donkey mares dosed with large amounts of live abortus-equi culture. 11. The significance of S. abortus-equi in equine abortion is comparable with that of S. cholerae in swine-fever. Like cholerae-suis, abortus-equi is regarded as a saprophyte which frequently occurs in the body of the horse without causing any obvious disturbance, invading the tissues of the body only when conditions become favourable. When the resistance of the foetus, foetal membranes and uterus has been lowered by the primary cause of infectious abortion, viz., the filterable infecting agent, this organism enters and causes a secondary infection. Alternatively abortus-equi plays the role of a synergist as H. influenzae suis. 12. The advisability of further investigating the etiological significance of salmonella encountered in epizootic diseases like calf paratyphoid and fowl typhoid is suggested.
The familial incidence of spontaneous osteopetrosis gallinarum
(Pretoria : The Government Printer, 1946) Bronkhorst, J.J.; Coles, J.D.W.A.; Du Toit, P.J.
Thirty-nine spontaneous cases of osteopetrosis have been studied in the Onderstepoort experimental flock of fowls, and the disease has shown a striking tendency to affect some families more than others. Evidence has been advanced indicating that a susceptibility to the disease depends on a recessive character. There is also some indirect evidence that susceptibility depends on a unifactorial recessive. Malignant conditions, such as leucosis and carcinosis, were not found more frequently in fowls with osteopetrosis than in the flock as a whole. Families stigmatized with osteopetrosis almost never provide birds worthy of inclusion in a high class breeding pen. We have stated the grounds on which a hen should be admitted to a good breeding pen, and we have indicated what success has crowned our efforts to evolve a strain of fowls resistant to neoplastic conditions, while being also highly desirable in all other respects. The literature dealing with osteopetrosis in fowls and man has been reviewed and the points of similarity and dissimilarity have been discussed.
The biological values of the proteins of some South African (whole seed) maize varieties
(Pretoria : The Government Printer, 1946) Myburgh, S.J.; Du Toit, P.J.
1. The biological values of yellow maize and white maize are given for some eleven varieties grown under South African (summer rainfall) conditions. 2. The results indicate that there exists a significant difference in the nutritive value of the proteins of some of these varieties, but that these differences are not associated with the colour of the maize.
Recent investigations into the toxicity of plants, etc., no. XV
(Pretoria : The Government Printer, 1946) Van der Walt, S.J.; Steyn, D.G.; Du Toit, P.J.
Of the 18 plants investigated the following four plants were, according to the literature available to the authors, for the first time proved to be toxic: Tetragonia Schenkii Schinz., Encephalartos Lehmanii (E. & L.) Lehm., Moraea trita var. foliata N.E. Br., and Schizocarphus nervosus (Burch.) F. v. d. M. The toxicity of the pupae of Melasina circophora Meyr. was also investigated.
Avirulent anthrax vaccine
(Pretoria : The Government Printer, 1946) Sterne, Max; Du Toit, P.J.
More than 30 million doses of anthrax vaccine made from avirulent uncapsulated variants have been used in South Africa. The same vaccine is used for all domestic animals, and the results far surpass those obtained with the Pasteur type of spore vaccine. The strains sporulate very readily, and their immunizing power is easily tested in guinea-pigs. It has been found possible to dispense with large-animal immunity tests. Thus these strains lend themselves very well to laboratory manipulations.
Further investigations into immunization of cattle against rinderpest
(Pretoria : The Government Printer, 1946) Mitchell, D.T.; Le Roux, P.L.; Du Toit, P.J.
1. Kabete goat virus was not transmitted from reacting to susceptible cattle under conditions of close contact. 2. A single doubtful transmission was recorded under conditions of open grazing. 3. A febrile condition of unknown aetiology transmissible from cattle to goats was encountered. 4. Urine from reacting animals was non-infective, but faeces in one out of two cases was infective by drenching. 5. Immunity produced by a single injection of formal-glycerine spleen-vaccine had completely disappeared after 8 months. 6. Immunity produced by triple vaccination with formal-saline vaccine had diminished considerably after 8 months. 7. Triple vaccination followed by a single injection of formal-glycerine spleen vaccine 9 months later produced an immunity which persisted for at least 20 months. 8. The rapid production of immunity induced by a single injection of formal-glycerine spleen-vaccine could be used to control the reaction to K.G.V. An interval of 7 days between vaccine and virus appeared to be the optimum. 9. Spleen-vaccine prepared from cattle reacting to K.G.V. has an inferior antigenic potency. 10. The reaction produced by K.G.V. in grade cattle (British breeds of cattle x Zebu) are severe but usually non-fatal. A durable immunity follows the reaction.

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