Characteristics of hollow-bearing trees occupied by arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia

A total of 1125 hollow-bearing trees was observed for the presence of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia. Different species of arboreal marsupials exhibited preferences for hollow-bearing trees with different characteristics. Gymnobelideus leadbeateri (Leadbeater's possum) selected short, fat trees with numerous holes and a large quantity of dense surrounding vegetation. Very large hollow-bearing trees were favoured as nest sites by Petauroides volans. Petaurus breviceps preferred trees with a large number of fissures, whereas trees favoured by Antechinus stuartii were tall and thin. Trees selected as nest sites by Trichosurus caninus were typically short and fat with few holes. Our results provide evidence of resource partitioning of hollow-bearing trees amongst arboreal marsupials. Clear-felling of montane ash forest on an 80–120-year rotation will have a highly detrimental effect on arboreal marsupials by substantially reducing the number and range of types of hollow-bearing trees required to support the complete diversity of species. The 80–120-year interval between logging operations will result in trees being harvested well before they develop characteristics which make them suitable nest sites for arboreal marsupials.     

Culling on low milk yield and its economic consequences for the dairy herd

Voluntary culling on low milk yield and the economic returns for herds with a stable number of milk cows was investigated for spring calving dairy herds in the Republic of Ireland. The analysis was conducted at annual involuntary removal rates: 15, 20 and 25% and replacement costs as percent of beef value 94, 126, 157%. Varying cow replacement rate above involuntary removal rate by voluntary culling increased milk sold per cow in year 16 to a maximum of +5 to +10% after practicing a fixed strategy for 16 years. Greatest absolute and relative gains in yield occur from voluntary culling at the lowest involuntary replacement rate. Voluntary culling up to 3 to 8 percentage units above involuntary cow replacement rate maximizes economic returns per cow in herd when the market price for replacement heifers exceeds 150% of their beef value. Maximum voluntary culling may be practiced for prices near or below beef value.     

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.