Masters Degrees (Animal Sciences)

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Browsing Masters Degrees (Animal Sciences) by Author "Boden, Jarryd Michael"

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    The effect of intensive feeding duration on the authenticity of Karoo lamb
    (Stellenbosch : Stellenbosch University, 2024-03) Boden, Jarryd Michael; Strydom, P. E.; Hoffman, L. C.; Marais, Jeannine; Van Zyl, Johan Hendrik Combrink; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: Present climatic conditions such as droughts are becoming more frequent and may affect the future production of authentic Karoo lamb. To mitigate the effect of these possible climatic events on authentic Karoo lamb production, production practices need to be updated or modified. Although a supplementary feeding protocol is currently in place, establishing an intensive feeding protocol that affords all certified Karoo lamb producers the option to intensively feed for a limited duration, prior to unfavourable climatic conditions, is required. Additionally, as the sensory profile of Karoo lamb is its unique quality, changing the production practices, associated with the feeding regime, may influence the authenticity of Karoo lamb. During this investigation, free-ranging Dorper ram lambs from the Karoo region were intensively fed in a feedlot for 0, 21, 28 and 35 days on the same diet. During this period, the performance, carcass quality and profitability were evaluated. Feedlotting increased feed costs and is an uncharacteristic production system for an origin-based and region-specific meat product, such as Karoo lamb. However, when climatic conditions dictate feedlotting, the Dorper breed when raised and weaned on an extensive production system performs well. Following the initial investigation, the retail shelf-life of lamb chops was evaluated by measuring colour changes and lipid oxidative capacity over a seven-day shelf-life trial. Additionally, the proximate composition and physical characteristics of lamb meat were evaluated. The feeding system appeared to be responsible for the variations in lamb meat colour attributes and lipid oxidative capacity. Lambs slaughtered directly off pasture had better colour stability and lipid oxidative capacity than those placed in a feedlot. Overall, the colour, physical meat characteristics and lipid oxidative capacity of the lamb meat in the current investigation would be considered acceptable across all groups. To measure meat compositional changes, the fatty acid composition and carbon and nitrogen isotopic ratio of lamb meat influenced by intensive feeding duration was evaluated. Fatty acid and stable isotope compositional changes were apparent due to intensive feeding. However, key FAs were still within beneficial bounds and isotope ratios within previously defined isotopic ratios for free-ranging Dorper lambs from the Karoo region. Lastly, the effect of intensive feeding duration on the sensory profile of previously free-ranging Dorper ram lambs was investigated. The “herbaceous” quality was not surrendered during intensive feeding, however the subsequent increase in pastoral aromas diluted and modified the unique aroma and flavour. A diet devoid of feedstuffs known to promote negative aromas and flavours is postulated to be more appropriate for maintaining the unique Karoo lamb meat aroma and flavour during a period of intensive feeding. It is difficult to conclude whether the authentic nature of Karoo lamb was indeed preserved or not. However, the overall quality of Karoo lamb as a meat product changed during an intensive feeding period and thus it is the opinion of the author, that considering everything, the authentic quality of Karoo lamb was not preserved.