Masters Degrees (Animal Sciences)

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Browsing Masters Degrees (Animal Sciences) by Author "Badenhorst, Magdalena Johanna"

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    Evaluation of enzymatic activities in rumen fluid and respective in vitro digestibilities
    (Stellenbosch : Stellenbosch University, 2018-03) Badenhorst, Magdalena Johanna; Raffrenato, Emiliano; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: Rumen enzymatic activity studies and in vitro digestibility studies are potentially correlated and affected by similar factors. However, performing enzymatic activity studies parallel to in vitro digestibility studies is hindered by the lack of a standard method of analysis and by the lack of knowledge surrounding the variables that could potentially influence the enzymatic activity. It is known that the composition of the ruminal microbial population is responsive to changes in various natural and feed related factors, but the dynamic between the microbial population and enzymatic activity within the rumen, and factors affecting enzymatic activity are not well defined. The objective of the first experiment was to determine the effect of blending and sonication on enzymatic (amylolytic, lichenase, endoglucanase, xylanase, protease) activity and the effect of blending on in vitro digestibility (starch, neutral detergent fibre, nitrogen) when compared to simple filtration (control). Both blending and sonication significantly and consistently increased amylase, lichenase, endoglucanase and xylanase activity with no significant difference between the two enzyme extraction methods. For protease activity, only sonication was able to significantly increase the activity compared to the control. For the in vitro analysis, blending was unsuccessful in liberating amylolytic microorganism associated with the particulate fraction and might have negatively affected the microbial population responsible for neutral detergent fibre (NDF) and protein digestion. The objective of the second experiment was to determine if diurnal patterns in starch, NDF and protein digestibility and amylolytic, fibrolytic and proteolytic activity, respectively, exist. Two of the cows were restricted from feed for 8-hours overnight, and the other two continued to receive their feed ad libitum, to isolate but also quantify the effects of a possible different feeding behaviour at night. Rumen fluid was sampled before the morning feeding, and subsequent collections were every 4-hours for a 24-hour period. When fitted to a cosine function, all the parameters tested followed a daily pattern that was sensitive to the availability of feed overnight, although the parameters responded differently to the feeding treatment. The highest activities for amylase, lichenase, endoglucanase and xylanase were observed at the time points subsequent to milking and feed delivery, suggesting that the cows adapted their feeding behaviour to the time of feed delivery and milking. Protease activity was unaffected by either feeding treatment or possible feeding behaviour, although when fitted to a cosine function it did display a daily pattern that was sensitive to the availability of feed overnight. The patterns displayed by in vitro digestibility of starch, NDF and nitrogen, across the various fluid collection time points, were much more variable than expected and could be attributed to the fact that a higher number of variables affect the final results. The acrophases observed in the enzymatic analysis did not correspond to those observed in the in vitro analysis. Therefore, different interpretations should be given to enzymatic activities and in vitro digestibility values and the time of rumen fluid collection relative to feeding time should always be included when rumen fluid is utilised for research or commercial purposes.