The tranfer of Brucella abortus antibodies from dam to calf.

The higher sensitivity of the ABGT (Coombs Test) makes it the most useful test for comparison of total specific immunoglobulins for Brucella abortus in different secretions. Using it in the present study it was found that in 85 cows the mean selective concentration of immunoglobulins in colostrum was six to eight fold, whether the cows were infected or not. In the non-infected group calves acquired mean levels of immunoglobulins of about one third those in colostrum whereas in the infected group this ratio reduced to about one seventh. There were wide individual variations. However, mean values indicate that in both groups the calf acquires a level of antibodies up to twice the level of the dam's pre-partum serum, again with individual wide variations. Titres to the SAT and CFT are also given for all animals.     

Theileriosis: The exposure of immunised cattle in aTheileria lawrencei enzootic area

Summary Three groups of steers were exposed to field challenge in aT. lawrencei-enzootic area of Kenya. Four out of five ECF-susceptible steers and four out of five steers immunised againstT. parva (Muguga) died of theileriosis, the surviving animals experiencing severe reactions. On the other hand, all five steers immunised againstT. parva (Muguga) and a strain of theileria probably homologous with the one present in the area of exposure, survived and only experienced mild reactions. These results indicated that immunisation of cattle withT. parva (Muguga) may not necessarily protect them against field challenge with certainT. lawrencei-type strains, but that immunisation with an apparently homologous strain of theileria may well do so.

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Sumario Tres groupos de novillos fueron expuestos al desafio de campo en un area de Kenya enzootica aT. lawrencei. Cuatro de cinco novillos susceptibles a la Fiebre de la Costa del Este y cuatro de cinco novillos inmunizados contraT. parva (Muguga) murieron de Theileriosis; los animales sobrevivientes experimentaron reacciones severas. De otra manera, todos los cinco novillos inmunizados contraTheileria parva (Muguga) y una cepa de theileria probablemente homologa con la presente en el area de exposición, sobrevivieron y solo experimentaron reacciones ligeras. Estos resultados indicaron de que la inmunización del ganado conT. parva (Muguga) puede no necesariamente proteger contra el desafio de campo con ciertas capas ó tipos deT. lawrencei, pero que la inmunizacion con una cepa de theileria aparentemente homóloga puede proteger.

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Résumé Trois groupes de bouvillons ont été soumis à l'épreuve sur le terrain dans une région du Kenya où sévit une enzootie àT. lawrencei. Quatre sur cinq bouvillons neufs et quatre sur cinq bouvillons immunisés contreT. parva (Muguga) sont morts, les survivants éprouvant des réactions graves. D'autre part, cinq bouvillons immunisés contreT. parva (Muguga) et une souche deTheileria probablement identique à celle présente dans la région d'exposition, ont survécu et n'ont présenté que de faibles réactions. Ces résultats montrent que l'immunisation de bovins avecT. parva (Muguga) peut ne pas les protéger nécessairement de l'épreuve sur le terrain avec certaines souches de typeT. lawrencei, mais que l'immunisation avec une souche deTheileria apparemment identique àT. lawrencei peut le faire.

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On O.D.A. secondment from the A.R.C. Institute for Research in Animal Diseases, Compton, nr. Newbury, Berks., U.K. (Research Project R 2396).

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Supported by a grant from Pfizer Corporation, New York.

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On U.S.D.A. secondment from Plum Island Animal Disease Laboratory, Box 848, Greenport, Long Island, N.Y. 11944, U.S.A.

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Project supported by the United Nations Development Programme, with the Food and Agriculture Organization of the United Nations as the Executing Agency, in co-operation with the East African Community. The Project is also supported by the Overseas Development Administration of the United Kingdom (Research Projects 2396 and 2494), the United States Department of Agriculture, the Rockefeller Foundation, the International Atomic Energy Agency and the Pfizer Corporation.     

The economic consequences of beef crossing in dual-purpose or dairy cattle populations

The total benefit from·beef crossing in a dairy or dual-purpose cow population is (0.68)KM'_bN, where K is the proportion of cows crossed to beef bulls, M'_b is the net economic superiority of beef cross progeny over straight dairy or dual-purpose progeny as beef animals and N is the total number of inseminations. For relatively modest values of K and M'_b, this benefit is shown to be greater than the total cost of the A.I. service. The second consequence of beef crossing is to concentrate the dairy merit transmitted into fewer inseminations. This raises their average genetic value and increases the return for investment in dairy testing and selection.     

Statistical efficiency in bull progeny testing for calving difficulty

The binomial distribution was used to examine the precision attainable in bull progeny testing for traits like calving difficulty as the following parameters were varied: P_o, the basic incidence level in the population, n, the progeny group size, and α and β, the probabilities of two kinds of erroneous conclusion. The results showed that in all circumstances a group size of 250–300 progeny gave a good compromise between cost and precision.There was little to choose between testing based on calvings in heifers and in cows. As the basic frequency increases, more progeny are required for a given degree of precision. Thus testing is more expensive in breeds with high rates of difficult calving than in those with low rates.     

The technical development of sheep production from hill land in Great Britain

The hill-sheep farming industry in Great Britain, in which the ewe flocks are dependent on grazed pastures throughout the year, is described briefly. Research work on the relationships between nutrition and the various components of hill-sheep production (principally ovulation rate, lamb birth weight, milk production and lamb growth rate) has provided an understanding of the biological reasons for current low levels of output, and has led to the development of a new system of management. This is based on the provision of improved nutrition, from higher quality pasture, at the two stages in the annual cycle when sheep production is most responsive to changes in nutrition, i.e. during lactation and in the pre-mating/mating period. In large field-scale tests of the new management system increases of 130 to 290% in the weight of weaned lamb produced have been achieved as a result of combined increases in output per ewe and in ewe numbers.