Browsing by Author "Engelbrecht, Michiel Nicolaas"
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- ItemThe effect of supplements containing different protein and energy sources and essential oils on the performance of pasture finished heifers(Stellenbosch : Stellenbosch University, 2015-12) Engelbrecht, Michiel Nicolaas; Cruywagen, C. W.; Hoffman, Louwrens C.; Hoffmann, Willem H.; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.ENGLISH ABSTRACT: Sixty Bonsmara heifers (328 ± 3.9 kg) on planted pastures were used to evaluate the effect of two energy sources and three growth promoters on body weight gain. Two supplementary feeds with dried apple pulp (A) or maize (M) as main energy source were formulated on an iso-nutrient base. One of three different growth promoters was included in each energy supplement: placebo (no growth promoter, designated as Treatments Ap and Mp), ionofore (monensin, designated as Treatments Am and Mm) and essential oil extract (from oregano, designated as Treatments Ao and Mo). A fixed amount of the supplements was offered to the six treatment groups in a growth/finishing study on cultivated grass-legume pastures. Animals were stratified according to initial weight in ten blocks and treatments were assigned randomly to animals in each block. The 66 day growth study was conducted during spring (Sepember to November, 2014) in the Western Cape Province of South Africa near Greyton. The cultivated pastures consisted of a perennial grass-legume mixture. A rotation grazing system was applied and animals were moved to new paddocks once a week. Based on falling plate meter readings, the heifers consumed a calculated mean amount of 4.48 ± 0.08 (SEM) kg DM/day over the entire experimental period. A fixed amount of 4 kg (“as is” basis) of the respective supplements were offered daily during the first 42 days, followed by 5 kg/day from 43 days until the end of the study (66 days). Animals were weighed bi-weekly and average daily gain (ADG) was calculated. The mean ADG of the six treatment groups was 1.44 kg/day. No interactions occurred between the energy sources and growth promoters used in the concentrates and main effects were thus interpreted. The supplements that contained apple pulp as energy source resulted in a higher (P < 0.02) ADG (1.54 kg/day) than the maize containing supplements (1.33 kg/day). There were no differences between any of the growth promoters, with the placebo resulting in similar growth rates than monensin and oregano oil extract. Mean ADG values (kg/day) of the different growth promoter treatments were 1.44 (placebo), 1.49 (monensin) and 1.38 (oregano). All the heifers were slaughtered at the end of the trial. Carcass weight and dressing percentage did not differ between energy sources or growth promoters. The mean dressing percentage was 52.5%. The mean income over feeding cost for the 66 day period of the three maize energy source treatments was R254.20/heifer, while that of the apple pulp treatments was R524.75/heifer. According to this study, concentrate supplements containing apple pulp as main energy source were economically more desirable than those containing maize as primary energy source.