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Discipline: management; Key words: liver fluke, mastitis, milk flocculation, performance.
Liver fluke (Fasciolosis): Milk SA funds two projects to address the problem, a comprehensive investigation on farms in the Tsitsikamma area conducted by Dr Jan van Wyk of Onderstepoort as project leader and an investigation at UKZN on bio-control measures as alternative to drug treatment, the project leader being Prof Mark Laing, with post-doctoral assistant Dr Mawahib Ahmed being responsible. The titles of the projects are, respectively: Fasciola hepatica: Impact on Dairy Production and Sustainable Management on Selected Farms in South Africa, and Biological Control of Liver fluke in Cattle.
On-farm results have confirmed observations of dramatic differences in the importance of Fasciola prevalence between farms situated close together, to the extent of mean totals of respectively zero and about 40 of the intermediate hosts (Lymnaea truncatula and L. columella) per sampling site on two adjacent farms, as well as large differences between adjacent similar sampling sites per farm. Analysis of soil on these farms to understand why the differences occur included more than 50 components of soil, as well as measurements of water acidity and conductivity (calibrated in relation to water temperature), which are of extreme importance to snail survival and propagation. Testing for the susceptibility of the intermediate hosts by PCR has also been initiated and is regarded as of crucial importance to the project, because molecular biological technology could be expected to lead to a practical approach to a relatively simplified quantification of the likelihood of muddy spots, and therefore farms harbouring the intermediate snail hosts and thus the occurrence of fasciolosis. In order to enable PCR investigation of the intermediate host species of Fasciola, as well as the susceptibility of the intermediate hosts to infection with the Fasciola parasite, laboratory facilities have been established at Onderstepoort and isolates from two of the trial farms are being maintained in laboratory snail culture. Experimental infection of the snails with the parasite is in preparation.
In the bio-control work inhibition of the fluke and the intermediate host has been the target. The approach is to test inhibiting plant extracts and Bacillus species. The efficacy of Morgana (Lilium spp), Moringa (Moringa oleifera), Funnel and Lemon grass (Cymbopogon spp) was tested in vitro against fluke eggs using three dfferent solvents at 20 % concentration. Results showed that both Morgana and the Moringa plant extract was 100% effective. With ethanol extraction, both pineapple (Ananas comosus) and Moringa showed strong ovicidal effects against the eggs of the liver fluke.
In the Bacillus work, 43 isolates have been tested against the Lymnaea host. Screening trials revealed possible interference with the reproduction of the snails. Two isolates may have had an effect in the delay of reproduction and another isolate may have had an effect in the inhibition of reproduction. The results, however, were inconclusive and further screening is required.
Mastitis: The studies are conducted within two funded projects, addressing the condition from several angles. The umbrella focus is the problem of possible antibiotic resistance which includes investigations to understand how farmers deal with mastitis, under what circumstances (environmental, managerial etc) does the condition thrive, the distribution of different mastitis-causing organisms and strains throughout the milk producing areas, and alternative prevention and treatment methodologies. Project leaders are Dr Martin van der Leek of Onderstepoort and Prof Mark Laing of UKZN; the responsible post-doctoral assistant being Dr Iona Basdew. The titles of the respective projects are: Resistance to available antibiotics in lactating cows with mastitis, and Investigating alternative methods such as bacteriophages and bacteriocins to control mastitis organisms.
With regard to the van der Leek Project, the survey work and the work conducted for Masters studies are in the phase of statistical analysis or finishing for thesis purposes. Major input was made in communication at the 2017 Large Herds Conference (LHC) and at the World Dairy Summit (WDS) in Belfast. Survey results of farms were presented as posters at the LHC, topics being management in the parlour, general udder health, treatment of clinical mastitis, preventative and failure costs and farmer perceptions. Scientific contributions include: Streptococcus uberis: prevalence and susceptibility patterns among dairy cows with clinical mastitis in selected farms in South Africa, and Antimicrobial susceptibility patterns of CNS species among dairy cows with clinical mastitis from selected herds in South Africa. A poster was also presented on milking machine setting at the LHC, emphasizing the importance of teat liners in preserving teat integrity and udder health. Presentations at the WDS were: A survey of mastitis management practices on South African dairies, Preventive and Failure Costs of Mastitis in South Africa, and Effect of climatological factors on bulk tank somatic cell count (BTSCC) on South African dairies. Furthermore, a paper was accepted for publication, the title being: Proactive udder health management in South Africa and monitoring of antibiotic resistance of Staphylococcus aureus in dairy herds from 2001 to 2010.
At UKZN, a major objective is to build a gene bank of mastitis pathogens and bacteriophages to test against the pathogens. During 2017, a further six strains of Staph. aureus were added to the existing bank of 42 strains and a further four Streptococcus uberis, six S. galactiae and five S. dysgalactiae strains to the existing Streptococcus spp. bank. The phage bank comprises 73 phages, with variable lytic ability against the Streptococci. Eight of these phages showed wide spectrum activity with lytic potential against S. uberis, S. galactiae and S. dysgalactiae, which is promising from a practical application point of view. Laboratory protocols for large-scale production of phages for field trials have also been achieved. However, whereas the protocols are satisfactory to produce phage stocks for field trials, it is by no means on an industrial/commercial level of production. This stillrequires major revision in order to mass produce the phages for herd applications. The bacteriocin aspects of the study at UKZN have been replaced with the use of bacillomycins from lactobacilli. This is still in the early stages of discovery involving extraction, efficacy testing and establishing the host range.
Milk flocculation: This requires studies at the cow feeding level, the bacterial contamination level and the enzymatic proteolytic level in milk. The cow feeding studies are done at Outeniqua, with project leader Prof Robin Meeske and the microbiological/biochemical studies at UFS with project leader Dr Koos Myburgh. The respective project titles are: The effect of anion/cation difference and potassium content of the diet on heat stability of milk, and Further studies to determine the effect of proteolytic enzymes in raw milk on flocculation and gelation.
In the study at Outeniqua, high potassium levels due to pasture fertilization were hypothesized as being contributory. Thus, K levels were progressively increased in the concentrate mix. The pasture grazed was of high quality and contained a K content of 5.2%. With the supplementation, this resulted in a K content in the total diet of the cows on the high K treatment of more than 5%.The higher K levels in the diet significantly reduced the alcohol stability of the milk and also reduced the protein, lactose and MUN content in the milk. The reduced milk protein of 0.2% on the high K treatment compared to the low K treatment may result in a R 0.20-R 0.30/L decrease in milk price depending on the milk buyer. The high K level also resulted in reduced milk Ca, K, P and Mg. The lower milk P content may partly explain the reduced protein stability of the milk as P linkages are present in the structure of casein micelles and are crucial to maintain stability of milk protein.
The UFS studies investigated the effect of milk fat content on flocculation, the effect of high pressure homogenisation on the susceptibility of milk fat towards lipase attack, the inhibition of proteolytic activity by chemicals and the impact of various gasses on the inhibition of milk flocculation. In the fat content study, the results showed that fat-free and low-fat milk were more susceptible to proteolytic attack when hydrolysed by Bacillus enzyme than full-cream milk. Also, when fat-free milk and low-fat milk were hydrolysed by plasmin, they were moresusceptibleto proteolytic attack than full-cream milk. In the homogenization experiment the by-products of lipase hydrolysis (FFA) activated plasminogen to plasmin in both homogenized and un-homogenized milk in comparison to raw milk (control), although there was more enzyme activity in the un-homogenized raw milk. The results furthermore showed that by homogenizing milk, the milk fat became more susceptible to lipase attack and the FFS activated plasminogen to plasmin. Chemicals had a huge impact on the reduction of proteolytic activity induced by either Bacillus enzyme or plasmin enzyme. When UHT fat-free milk was treated with the Bacillus enzyme, the addition of EDTA reduced the enzyme activity the most, followed by CaCl2, SHMP and Sodium citrate. Moreover, when the milk was treated with Plasmin enzyme, there was a more pronounced reduction in protease activity and the addition of SHMP reduced the enzyme activity the most followed by Sodium citrate, CaCl2, SHMP and lastly EDTA. To study the effect of gas addition on flocculation, N2, CO2 and helium were bubbled through respectively UHT fat-free milk, UHT full-cream milk and raw milk. In both UHT milks gas decreased protease activity compared to control UHT milk. Also, when both gas-bubbled UHT milks were hydrolysed by plasmin, the enzyme activity was decreased in comparison to UHT milk not gas treated. A similar result was found for the raw milk. In terms of ranking, the protease activity was decreased the most by CO2 followed by helium and then N2. In the Bacillus protease study, when raw milk was hydrolysed by the enzyme, the protease activity in CO2 and helium bubbled raw milk was decreased in comparison to control. However, surprisingly, N2 stimulated the enzyme activity. Overall, although much work has still to be done, there are similarities, additivity and also distinctive characteristics between the activity of bacterial protease and plasmin, but both play a significant role in milk flocculation/gelation.
Performance measurement in automatic milking systems (AMS): The ultimate goal is to measure performance parameters over time using also historical data to establish trends and develop prediction models. A first requirement was to develop a template from the large data base for easy analysis and interpretation which can be replicated in other investigations. This was the objective of the Masters study of Anton Gresse supervised by Prof Este van Marle-Köster of UP. The title of the project is: Different approaches for analysis of production performance from automatic milking systems in SA.
Two farmers were identified with comprehensive data sets, one in a pasture-based system and one in a TMR system. Historic herd performance data were extracted, data tables were constructed for statistical and trend analyses and a template developed as part of the Masters thesis. It is envisaged that the methodology used in the project will be suitable to be applied to analyse historic herd performance data of other AMS farmers.