Browsing by Author "Van der Merwe, J."

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    Effects of varying sweet lupin dietary inclusion levels on feather classes, leather traits and meat composition of feedlot ostriches
    (South African Society for Animal Science, 2017-12-01) Brand, T. S.; Engelbrecht, J. A.; Van der Merwe, J.; Hoffman, L. C.
    The main consumer products derived from ostriches are feathers, leather and meat. Despite progress in optimizing production practices, additional information is still necessary about the value of various raw materials as feed to ensure cost-efficient production. This study aimed to determine the effects of the gradual replacement of soybean oilcake meal with sweet lupin (Lupinus angustifolius) seed in the diet of feedlot ostriches on the feather, leather and meat production characteristics. The chicks received a standard commercial pre-starter ostrich diet, with the trial utilizing 141 ostrich chicks (± 10 chicks per group), beginning with the starter phase (83 days posthatching) and reared until 11 months of age. Five iso-nutritional diets were formulated for each feeding phase (starter, grower and finisher) according to specifications for each phase. In each phase, a control diet (Diet 1, 0% lupin diet (LD)) was formulated using soybean oilcake meal as the sole protein source and Diet 5 (100LD) was formulated to include the maximum amount of sweet lupin according to the specifications for the species and feeding phase. The maximum amount of sweet lupin included in 100LD therefore differs among the three feeding phases. The remaining three diets were formulated by gradually replacing soybean oilcake meal with lupins in the following increments: 100 : 0 (0LD); 75 : 25 (25LD); 50 : 50 (50LD); 25 : 75 (75LD), and 0 : 100 (100LD). There were three replications per treatment, resulting in 15 groups of birds. Feed and water were supplied ad libitum. No differences were found for moisture, crude protein and ash contents of the meat. However, the intra-muscular fat content was significantly influenced by the sweet lupin content of the diet. No differences were found for any of the feather classes that were measured. Regarding leather traits, the treatment diets had no effect on the crust sizes, leather grades, nodule diameters, and nodule densities. Differences were observed for leather thickness and pinhole number. It can be concluded that the sweet lupin inclusion levels evaluated in this study had little influence on leather traits, meat composition and feather classes.
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    Feed preference of grower ostriches consuming diets differing in Lupinus angustifolius inclusion levels
    (South African Society for Animal Science, 2017-12-01) Brand, T. S.; Engelbrecht, J. A.; Van der Merwe, J.; Hoffman, L. C.
    Feed costs contribute the largest proportion of the input costs of slaughter birds in an intensive ostrich production unit. Alternative, cheaper feedstuffs, such as lupins (sweet and bitter cultivars), were therefore evaluated to determine the optimal lupin inclusion level in ostrich rations without affecting feed preference and intake. Sixty South African Black ostriches were randomly divided into ten paddocks of six birds per paddock. Three trials, with five different experimental diets, were conducted to investigate the diet preference of grower ostriches in a free-choice system. Feed and water were supplied ad libitum. The position of the diets in the successive paddocks was varied by rotating the five feed troughs in a clockwise direction, but within each paddock the position of each feeder and diet stayed the same throughout the three trials. In the first two trials, sweet (trial 1) or bitter (trial 2) lupins replaced soybean oilcake meal to have 0, 7.5, 15, 22.5, and 30% lupin inclusion levels in the diet. In trial 3 the soybean oilcake meal was replaced with either sweet or bitter lupins to have dietary inclusion levels as follows: 0% lupins, 15% sweet, 15% bitter, 30% sweet, or 30% bitter. The daily intake per group for each diet was monitored over a period of five days each. The average initial body weight of the birds was 73.6 ± 0.5 kg. No interaction was found between day and diet for the three trials and dry matter intake (DMI) did not differ between the five treatments for any of the three trials. In the second trial the birds tended to show a preference for the 7.5% bitter lupin inclusion level and discriminated against the 15% and 30% bitter lupin inclusion levels. Regression analysis of DMI on lupin inclusion rates revealed no significant trends. In conclusion, the study revealed that soybean oilcake meal can be replaced in the diets of grower ostriches by sweet lupin inclusion levels up to 30%, without any significant detrimental effect on diet preference and feed intake.
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    The influence of different dietary energy concentrations on the production parameters of feedlot ostriches
    (South African Society for Animal Science, 2017-12-01) Brand, T. S.; Viviers, S. F.; Van der Merwe, J.; Hoffman, L. C.
    Energy is essential for the continuous survival of any living organism. In ostrich diets, energy is usually derived from maize, which is often subject to fluctuations in yield as a result of drought conditions. Therefore, the optimal utilization of energy in the diets of ostriches becomes of paramount importance, but without affecting the performance of the birds negatively. This study was conducted to investigate the influence of five treatment diets, each with a different energy concentration, on the growth performance of 300 slaughter ostriches. Three replications per treatment resulted in 15 camps of ostriches being fed through the four feeding phases from pre-starter to starter, then grower, and finally finisher. A high mortality rate was experienced during the pre-starter phase, while the chicks were still young. Significant differences were found among the live weights of the birds after the pre-starter phase, with birds that consumed the middle diet (Diet 3) being the heaviest, at an average of 22.3 ± 0.33 kg. However, by the end of the trial, these differences were not significant. This was reflected in the production parameters, namely dry matter intake (DMI), average daily gain (ADG) and feed conversion ratio (FCR). Differences were found only in the pre-starter phase in ADG, with Diet 3 displaying the highest gain per day of 216.0 ± 8.08 g. Thus, in this study, dietary energy above and below the predicted optimum (Diet 3) seemed to have little influence on the performance of the ostriches, but results may have been affected by the above-average mortalities.
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    The negative effects of mucolytics in otitis media with effusion
    (Health & Medical Publishing Group, 1987) Van der Merwe, J.; Wagenfeld, D. J. H.
    Much controversy still exists in the treatment of otitis media with effusion. A double-blind randomised prospective trial during which bromhexine hydrochloride was compared with a placebo is reported. Information from 60 patients was analysed and the results reveal interesting findings on the effects of bromhexine on middle-ear clearance. The data clearly reveal that bromhexine retards resolution of the effusion. Further discussion of the literature gives insight into the controversy surrounding the treatment of middle-ear effusion. Steroids are proposed for further research and clinical trials.
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    Parameter identification and evaluation of a proportional directional flow control valve model
    (South African Institution of Mechanical Engineering, 2013) Van der Merwe, J.; Muller, J. H.; Scheffer, C
    Servo-pneumatic command device selection and control may be greatly aided by adequate mathematical models and identification procedures. This paper reports on theory and experimental procedures applicable to the characterisation of pneumatic proportional directional flow control valves. The model implemented is shown to be well suited to predicting the effects that sharp-edged, concatenated orifices and small openings have on mass flow. An experimental setup and test protocol is presented that is less wasteful in terms of energy and effort than that of the ISO 6358:1989(E) standard. Unknown model parameters are optimised during the identification procedure, characterising the behaviour of the valve for the entire range of control signal inputs. The identified model yields adequate results, with mean absolute error (MAE) values of less than 10 kPa in the presence of 700 kPa supply pressure for quasi-static control signal inputs. Acceptable prediction is also achieved for the transient control input case investigated. The work presented here then not only serves as a thorough introduction to proportional servo valve modelling theory and identification but may also prove suitable for use in a multitude of practical applications.
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    Treatment of male urethral strictures - possible reasons for the use of repeated dilatation or internal urethrotomy rather than urethroplasty
    (Centre of African Studies, University of Cape Town, 2012-08) Heyns, C. F.; Van der Merwe, J.; Basson, J.; Van der Merwe, A.
    Objective. To investigate the possible reasons for repeated urethral dilatation or optical internal urethrotomy rather than urethroplasty in the treatment of male urethral strictures. Patients and methods. Men referred to the stricture clinic of our institution during the period April 2007 - March 2008 were reviewed and the operative urological procedures performed in the same period were analysed. Statistical analysis was performed using Student’s t-test and Fisher’s exact test (p<0.05 statistically significant). Results. The mean age of the 125 men was 49.9 years (range 12.8 - 93.4 years). Previous stricture treatment had been given 1 - 2, 3 - 4 and 5 - 6 times in 52%, 32% and 12% of patients, respectively (4% had not undergone treatment). In these groups, previous treatment was dilatation in 70%, 76% and 72%, urethrotomy in 26%, 15% and 28%, and urethroplasty in 4%, 9% and 0, respectively. The group with 5 - 6 compared with 1 - 2 previous treatments was significantly older (mean age 60.2 v. 46.6 years) and had a significantly greater proportion with underlying co-morbidities (80% v. 52%). The group that had undergone urethroplasty compared with 5 - 6 repeated dilatations or urethrotomies was significantly younger (mean age 48.2 v. 60.2 years) with a lower prevalence of co-morbidities (47% v. 80%). During the study period urethroplasty was performed in 16 (2%) of 821 inpatients, whereas 55 men were seen who had undergone ≥3 previous procedures, indicating that urethroplasty was performed in less than one-third of cases in which it would have been the optimal treatment. Owing to limited theatre time, procedures indicated for malignancy, urolithiasis, renal failure and congenital anomalies were performed more often than urethroplasty. Conclusions. Factors that possibly influenced the decision to perform repeated urethrotomy or dilatation instead of urethroplasty were limited theatre time, increased patient age and the presence of underlying co-morbidities.