Department of Animal Sciences

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Browsing Department of Animal Sciences by Subject "Acacia mearnsii"

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    The effect of condensed tannins from Acacia mearnsii on in vitro kinetic parameters and feedlot lamb growth and carcass parameters
    (Stellenbosch : Stellenbosch University, 2024-03) Featherstone, Bradley William; Van Zyl, Johan Hendrik Combrink; Cruywagen, C. W.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: The enhancement of ruminant production efficiency is arguably one of the areas with the greatest potential to alleviate some of the complex problems that the industry faces, namely land use and greenhouse gas emissions with increasing demand for red meat products. The ruminant nutrition industry holds a considerable number of avenues in which improvements in animal production efficiency can be made. Condensed tannins have been identified as a possible feed additive, due to their high protein binding affinity and their potential use for protecting rumen degradable protein, thereby improving protein flow to the small intestine. Condensed tannins from Acacia mearnsii specifically are of considerable interest from a South African perspective. Not only are they already commercially available, but the A. mearnsii tree is a highly invasive tree species in the country. The incorporation of condensed tannins from this tree species has the potential to open new market opportunities for this invasive species, potentially aiding in limiting their proliferation. The aim of the in vitro section of this study was to identify the ability of condensed tannins from A. mearnsii, to protect a rumen degradable protein source from rumen degradation. Both rate and extent of degradation were determined. Condensed tannin was dosed at 0, 5, 20 en 45 g/kg dry matter and fermented in an in vitro protein degradation study with fresh rumen fluid and sunflowercake meal as substrate for 0, 2, 4, 8, 16, 24 en 48 hours, respectively. The addition of condensed tannins to sunflower oil cake resulted in decreased (P < 0.05) crude protein and dry matter degradation at inclusion levels of 20 and 45 g/kg dry matter. The decrease in crude protein degradation potentially allows for a greater passage of protein into the small intestine for digestion. The decrease in dry matter degradation does pose some concern, as this could lead to an overall slowing of dry matter digestion. This in turn would lead to a prolonged sense of satiety, subsequently decreasing animal voluntary feed intake and animal production. There is the added concern surrounding the well-known astringent nature of condensed tannins and the potential impact their dietary inclusion could have on voluntary feed intake in that regard, particularly at high inclusion levels. The in vivo section of this study aimed to identify the effect of condensed tannins from A. mearnsii on lamb growth and carcass parameters. Forty-eight Merino store lambs were randomly allocated to 4 treatments to contain 0, 5, 20 en 45 g/kg dry matter condenced tannins, respectively. Lambs that received the diets containing high amounts of condensed tannins (45 g/kg dry matter) had significantly poorer (P < 0.05) growth performance and carcass parameters. This was the result of reductions in dry matter intake of these lambs, due to the astringent nature of condensed tannins. At lower condensed tannin inclusion levels (5 and 20 g/kg dry matter), no effect was seen on both growth and carcass parameters, with these results thought to be a consequence of decreases dietary nutrient uptake. This lack of response contradicts reports in literature, further emphasising the complexity of the inclusion of condensed tannins in ruminant diets. Condensed tannins from A. mearnsii have the ability to effectively protect rumen degradable protein from ruminal degradation. Dietary inclusion levels should be limited to below 45 g/kg dry matter, due to the negative effects seen on animal production. Future research should further investigate the optimisation of the inclusion levels of condensed tannins from A. meansii, and the disassociation of condensed tannin-protein complexes post-ruminal digestion. Nevertheless, based on literature, the inclusion of condensed tannins from A. mearnsii in the diets of ruminant animals does have the ability to contribute towards a more balanced and sustainable future for the ruminant livestock industry.