Browsing by Author "Du Plessis, Izak"

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    The effect of breed type and slaughter age on certain production parameters of beef cattle in the arid sweet bushveld
    (Stellenbosch : University of Stellenbosch, 2004-04) Du Plessis, Izak; Hoffman, Louwrens C.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: The aim of this study was to provide scientifically founded guidelines to enhance the understanding of beef production from natural pastures in arid sweet veld regions. Cattle from four breed types ranging from large to small frame sizes (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni) were compared in terms of cow production and efficiency as well as the growth performance, carcass and meat quality of steers slaughtered at 18, 24 and 30 months of age. Eighteen and 30 month old steers were slaughtered at the end of the wet summer season, while the 24 month old steers were slaughtered at the end of the dry winter season. The Afrikaner herd (59.8 ± 9.0 %) had lower (p < 0.05) pregnancy rates than the Simmentaler cross (79.3 ± 12.2 %), Bonsmara cross (76.5 ± 11.1 %) and Nguni herds (86.1 ± 5.8 %). Breed differences (p < 0.05) for weaning weight and preweaning gain were observed (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni). The Nguni cow herd (46.5 ± 5.7 kg/100 kg mated) was more (p < 0.05) efficient than the Simmentaler cross (36.2 ± 5.5 kg/100 kg mated), Bonsmara cross (37.7 kg/100 kg mated) and Afrikaner herds (29.5 ± 5.9 kg/100 kg mated). During the dry winter season steers gained 23.4 ± 1.5 kg from 7 to 12 months of age and from 18 to 24 months of age they gained 20.9 ± 2.0 kg. During the wet summer season steers gained 109.7 ± 1.8 kg from 12 to 18 months and 120.3 ± 4.1 kg from 24 to 30 months of age. The best (p > 0.05) fat classification codes were attained at 30 months of age and the worst (p < 0.05) at 24 months of age. Simmentaler cross steers attained the lowest (p < 0.05) fat classification at all three age classes. At 30 months of age, 15 of the 63 steers slaughtered had 3 or 4 permanent incisors, while 47 steers had 2 permanent incisors. The total amount as well as the percentage kidney and omental fat were the highest (p < 0.05) at 30 months of age and the lowest (p < 0.05) at 24 months. Back fat thickness followed the same pattern. Although breed differences for some meat quality parameters were observed, slaughter age had a much more pronounced effect on meat quality parameters. The percentage cooking loss was the lowest (p < 0.05) at 30 months of age. The meat was also darker (p > 0.05) and more red (p < 0.05) at 30 months than at 18 or 24 months of age. The pH24 was higher (p < 0.05) at 24 (5.68 ± 0.05) and 30 months (5.65 ± 0.03) than at 18 months of age (5.48 ± 0.04). A trained sensory panel only detected that Longissimus muscle samples from 18 month old steers were more tender (p < 0.05) than that from 30 month old steers. Similar results were found for Warner-Bratzler shear force values. Marketing steers at 30 months of age resulted in higher production outputs for all the breed types than marketing weaners. For marketing both weaners and 30 month old steers the Nguni herd produced more marketable kilograms live weight than the Simmentaler cross, the Bonsmara cross and the Afrikaner herds. Different marketing systems suitable to the Arid Sweet Bushveld were identified. Each marketing system is discussed in terms of its application, advantages, disadvantages and adaptability to arid regions. It is maintained throughout that a conservative approach to grazing as well as cattle management is critical to ensure stable production systems in arid regions with erratic rainfall patterns.