The field detection of “inter-unit milk flow” in pipeline milking equipment

Abstract

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There are many ways in which a milking machine can transmit infection from cow to cow. The immediate transfer of infection by the, teat-cups is obvious and the reduction of the effectiveness of this vector has been shown to reduce the incidence of mastitis (Wilkinson, 1965 Fell, L. R. and Richards, R J. 1970. A farm survey of milking machine performance, milking management and California Mastitis Test results. Aust. J. Dairy Tech., 25: 39–45.  [Google Scholar]). The change from bucket to pipeline milkers has been associated with an increase in the incidence of mastitis arid this has been attributed to the vacuum instability of the latter system. Fell and Richards (1970 Whittlestone, W. G. and Fell, L. R. 1969. Machine milking and mastitis. Proc. N.Z. Soc. Anim. Prod., 29: 22–25.  [Google Scholar]) have studied the relation-ship between machine stability and the level of somatic cells in milk, and Whittlestone and Fell (1969) Whittlestone, W. G., Leonard, R. O. and Brookbanks, E. O. 1970. Breakthrough in mastitis research. N.Z. Jl Agric., 120: 66–67.  [Google Scholar] have suggested that milk line vacuum instability could be associated with flow conditions that could give rise to the movement of potentially infected milk from the pipeline back into the clusters. This potential vector has been overlooked in the past but its presence, would clearly negate the beneficial effects of “back flushing”. A field study was therefore undertaken to estimate the frequency of occurrence of the “inter-unit flow” effect in pipeline systems, and Whittlestone et at. (1970) Wilkinson, F. C. 1965. Bovine mastitis control in Western Australia. Aust. vet. J., 41: 93–97.  [Google Scholar] found a high incidence of milk movement back to the cluster in high pipeline systems though the effect was not found amongst the limited number of low-line installations examined. Two types of “inter-unit flow” were detected: whole liquid movement which appeared as liquid milk in the measuring trap inserted between the cluster and the milk pipe, and “aerosol” which could only be detected by the use of plugs of cotton wool inserted in the test teat-cups. Evidence for the presence of “aerosol” and its role in transmitting infection within the cluster has been collected by A. Tolle (pers. comm.). This establishes the possibility that once infected milk has reached the cluster it can be transferred to the, end of the teat during milking.     

Mannosidosis — A cause of neonatal mortality in angus calves

Abstract

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Mannosidosis, a lethal inherited neurological disease associated with a deficiency of the lysosomal enzyme α-mannosidase (Hocking et al., 1972 Greene, H. J., Leipold, H. W., Hibbs, C. M. and Kirkbridge, C. A. 1974. Congenital osteopetrosis in Angus calves. J. Am. vet. med. Ass., 164: 389–395.  [Google Scholar]) has been described clinically as affecting Angus calves usually in their firstyear of life (Whittem and Walker, 1957 Hocking, J. D., Jolly, R. D. and Batt, R. D. 1972. Deficiency of α-mannosidase in Angus cattle. Biochem. J., 128: 69–78.  [Google Scholar]; Jolly, 1970 Jolly, R. D. 1970. Diagnosis and control of pseudolipidosis of Angus calves. N.Z. vet. J., 13: 228–229.  [Google Scholar], 1975 Jolly, R. D. 1975. “Mannosidosis of Angus cattle: A prototype control program for some genetic diseases”. In Advances in Veterinary Science and Comparative Medicine, Edited by: Brandly, C. A. and Cornelius, C. E. Vol. 19, London and New York: Academic Press. In [Google Scholar]). Although it has been suspected as a significant cause of neonatal mortality in herds at risk, figures and diagnosis supporting such an hypothesis have not been available.     

Experimental tuberculosis in red deer (Cervus elaphus)

This study was designed to investigate experimental Mycobacterium bovis infection of red deer (Cervus elaphus). Three intravenously inoculated deer (dose 10µg–1000µg) developed miliary tuberculosis of the lungs and all died within 28 days of being infected. No clinical illnesses were observed in four subcutaneously (dose 1 uµg–100uµg) and three intratracheally (dose lµg–100µg) inoculated deer. At the conclusion of the experiment six weeks post inoculation, these seven animals reacted to 2 mg/ml of bovine purified protein derivative. The principal lesions in the intravenously inoculated deer were in the lungs which had multiple foci of necrosis containing very large numbers of acid fast bacilli. A gradation of changes was seen in the subcutaneously inoculated deer. The animal receiving the 1µg dose only had lesions at the injection site and the draining prescapular lymph node. Deer receiving higher doses also had histopathological changes in the lungs and liver. Microscopic changes in the intratracheally infected animals were restricted to the thoracic cavity. The ability of the deer to control infection was related to the route of inoculation.     

Yersiniosis in deer from the Otago-Southland region of New Zealand

Samples from 350 routine deer cases submitted to Invermay Animal Health Laboratory for diagnosis during 1979–1982 were examined specifically for the presence of Yersinia sp. An analysis of 57 cases of yersiniosis due to Yersinia pseudotuberculosis is made and two cases due to Yersinia enterocolitica are described. The occurrence of cases appeared strongly correlated with periods of stress, predominantlyin winter when cool wet conditions and lack of grazing combined to precipitate the disease. Animals up to one year old were most commonly affected (64% of cases). Of the 61 strains of Yersinia pseudotuberculosis isolated 35 were of Serotype I, 17 of Serotype II and nine of Serotype III. All strains of Yersinia pseudotuberculosis and the strains of Yersinia enterocolitica isolated from the two cases described were Hela cell invasive and gave a positive autoagglutination test for virulence.     

Red urine from red deer grazed on pure red clover swards

Twenty-four red deer hinds with their calves were released on to a newly established pure red clover sward and, 2 days later, red staining of the tail, perineum and hocks was observed. This was presumed to be of urinary origin. Observation of micturition showed that when urine was passed, it was a normal straw colour but it turned scarlet-red about 1 hour after exposure to air. Midstream urine remained the normal colour when held under a pure nitrogen atmosphere immediately after micturition, but it turned red when held in air in the dark, suggesting that the colour change was due to an oxidative rather than a photosensitive reaction. All deer grazing red clover were affected but this did not occur in deer grazing ryegrass/white clover swards. No adverse effects were observed in the deer grazing the red clover, and calf growth was significantly higher than on ryegrass/white clover, suggesting that the red urine had no effect on health or productivity.

Blood and urine analyses showed no signs of haemolysis, haematuria or haemoglobinuria. Preliminary chemical analyses suggest that the compounds involved are not those found in the urine of sheep grazing oestrogenic clover. The nature of the compounds have yet to be determined.     

Development of an arterial thrombosis model in pigs for investigating the thrombogenicity of different dietary fats

A surgically induced model of arterial thrombosis in pigs (60–80 kg live weight) has been developed using a balloon angioplasty technique. The purpose of this model is to assess the thrombogenicity of milkfat in comparison with other dietary lipids, thereby assessing its importance in the pathogenesis of human coronary heart disease. Balloon angioplasty catheters (Meditech, 3 cm X 8 mm balloon) are inserted into the left and right femoral arteries via a cut-down on to the saphenous artery. The balloons are inflated five times for 30 seconds with 30 second intervals between inflations. This results in endothelial denudation, exposure of sub-endothelial connective tissue and formation of platelet rich thrombi. Thrombus size is quantitated using autologous blood platelets labelled with ⁹⁹Tc-HMPA0 (technetium - “Deretec”).     

Leptospirosis in a lamb

Abstract

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Recently, we reported on outbreaks of Leptospira interrogans serovar pomona infection in newly weaned lambs(1) Vermunt, JJ, West, DM, Cooke, MM, Alley, MR and Collins-Emerson, J. 1994. Observations on three outbreaks of Leptospira interrogans serovar pomona infection in lambs. New Zealand Veterinary Journal, 42: 133–6. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]. It was suggested that wet environmental conditions played an important role in the pathogenesis of the disease in that class of sheep. This communication presents observations on another case of ovine leptospirosis, one that occurred under different circumstances, i.e. different season, age and environmental conditions.     

Thrombogenicity of dietary milkfat,fish oil and hydrogenated coconut oil in a pig model

Extract

Several indicators of thrombosis and thrombolysis were measured in four groups of 16 pigs fed for 10 weeks on either a low fat basal ration or rations containing 10% anhydrous milkfat (AMF), 10% fish oil (MaxEPA), or 10% hydrogenated coconut oil (HCO). At the end of the feeding period, pigs on the three test fat/oil rations were subjected to balloon angioplasty of both femoral arteries. Thrombus size at the site of injury was measured both morphometrically and using autologous blood platelets labelled with ⁹⁹Tc-HMPAO (technetium - “Deretec”).