Gianesella, Matteo (2008) Subacute rumen acidosis in Italian dairy herds: occurence and diagnostic tools. [Tesi di dottorato]
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Subacute rumen acidosis (SARA) represent one of the most important metabolic disorders in intensive dairy farms that affects rumen fermentations, animal welfare, productivity and profitability. Many are the factors that can increase the possible occurrence of SARA in dairy farms and in particular in intensive dairy farms: food type, food administration modality, rumen ability in absorbing short chain fatty acids (SCFA), year period, ingestion frequency, dry-lactation transition period and others conditions able to contribute to the SARA onset. SARA is possibly under diagnosed because of lack of pathognomonic signs, diurnal fluctuations in rumen metabolism, and problems in obtaining representative rumen fluid samples. Clinical signs of SARA include decreased dry matter intake (DMI), laminitis, rumenitis, liver abscesses, pulmonary bacterial emboli and, furthermore, displacement of the abomasums, mastitis and metritis, low fertility. These problems are linked to rumen pathology because of the exceptional osmotic capacity shown by the rumen and the increase in the adsorption rate of ruminal products, which may have toxic and vasomotor effects. Considering the above statement it is impractical to base the diagnosis of SARA only on the outcome of a clinical sign, but the only way to obtain an early and correct diagnosis is to observe and correlate multiple aspects of the condition: a thorough collection of the history in the farm; evaluation of the diet; evaluation of the ruminal fluid. The determination of ruminal pH is a key factor for the diagnosis of SARA. Different methods are available for the collection of rumen fluid for pH analysis. According several researcher rumenocentesis may be useful for the collection of rumen fluid for pH determination. A group of at least 12 cows (early or middle lactation) is defined as having SARA when more than 30% of them show a ruminal pH lower than 5.5. Anyway rumenocentesis remains a mildly invasive diagnostic method so it results hardly used by freelancer veterinarian and poorly accepted by farmer. A practical need for Veterinarians and Food practitioner, is to have a simple and economic method of diagnosis of SARA, in order to implement in a timely manner the appropriate corrective diet, eliminate the causes of arrival of this disorder and avert the danger of progress in the same very high levels. In response to these requests, the aim of this PhD thesis, was to lead three different studies related to each other but, in order to evaluate the occurrence of subacute rumen acidosis in intensive Italian dairy herds to determine the relationship among diet composition, ruminal pH and short chain fatty acids (SCFA) concentration, to evaluate the effect of the subacute ruminal acidosis on some blood parameters in lactating dairy cows and finally to evaluate the effects of rumenocentesis on the health and welfare status of lactating dairy cows, evaluated by physical examination, blood analysis, milk production and superficial temperature on the area of rumenocentesis using infrared thermography.
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