Browsing by Author "Rousseau, Francois Jacques"

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    The effects of maize cobs and supplemental rumen-protected conjugated linoleic acid (CLA) on production efficiency and meat quality characteristics of South African mutton merinos
    (Stellenbosch : Stellenbosch University, 2006-04) Rousseau, Francois Jacques; Hoffman, Louwrens C.; Ferreira, A. V.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: The objective of this investigation was to determine the effect of incremental inclusion of maize cobs, as well as supplemental rumen-protected conjugated linoleic acid (CLA) on the production efficiency and meat quality characteristics of South African Mutton Merino lambs. Prior to this trial, an in situ rumen degradability trial was conducted to determine the dry matter, protein and fibre degradability of maize cobs. Five ruminally cannulated Dohne Merino wethers were used to compare ruminal degradability of luceme and oat hay with that of maize cobs, using the in situ nylon bag technique. The samples were incubated in the rumen for varying time intervals. Both postincubated and original samples were analysed for dry matter (DM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF). The percentage disappearance at each incubation time was calculated from the proportion remaining after rumen incubation. Results obtained clearly established that, on average, the degradability of maize cobs is comparable with that of oat hay. Twenty four South African Mutton Merino (SAMM) lambs were used in a feedlot finishing study to evaluate the effect of maize cobs at incremental inclusion levels (4, 8 and 12%) on individual feed intake, average daily gain (ADG) and feed conversion efficiency (FCE). The apparent digestibilities of the three diets were also determined. The three pelleted diets were formulated, on an isonitrogenous and isoenergetic basis. The lambs were slaughtered after the trial had finished and the longissimus dorsi and biceps femoris muscles were removed from each carcass for the determination of proximate chemical composition and physical quality characteristics. Neither ADG nor FCE of the lambs was influenced by dietary treatment. Lambs fed the diet containing 4% maize cobs had the higher nitrogen retention, while diet did not affect energy retention. The proximate chemical composition of both muscles was not significantly affected by diet. Diet only had a significant effect on the cooking loss and the colour measurements of the M. longissimus dorsi. Sixteen South African Mutton Merino (SAMM) lambs were used in a second feedlot finishing study to evaluate the effect of feeding a diet containing supplemental rumen-protected CLA. The procedure followed was the same as in the first feedlot finishing study, except for an additional sensory and fatty acid analysis. No significant differences occurred in the ADG, FCE and dressing percentage of the lambs. Both energy and nitrogen retention of the lambs were not affected by dietary treatment. The proximate chemical composition of both muscles was similar, but diet had a significant effect on the cooking loss and the colour measurements of the M. longissimus dorsi. Diet had no significant effect on any of the five sensory attributes measured. Fatty acid composition was significantly affected by dietary CLA. Palmitic (Cl6:0), stearic (C18:0) and oleic (18:ln-9) acid were the major fatty acids in both muscles, as well as in the three adipose tissue types. The rumen-protected CLA increased the CLA (Cl 8:2n-6) contents of both muscles, although the increase was only significant for the M. longissimus dorsi and not for the biceps femoris muscle.