https://commons.ru.ac.za/vital/access/manager/Index en-us 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:5251 Wed 12 May 2021 23:21:27 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:38538 Wed 12 May 2021 23:00:38 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5273 Wed 12 May 2021 20:22:17 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5180 0.05). There is no need to implement a seasonal dietary regime. Cultured H. midae were fed artificial diets with different protein sources, including only soya, only fishmeal, a combination of soya and fishmeal, and these were compared to kelp-fed abalone. Kelp-fed abalone grew slower than those fed artificial feeds (p>0.05). Gonad growth was the greatest when soya meal was included in the diet (average GBI: 74.91 ± 23.31), while the average gonad size of abalone fed the fishmealbased diet had gonads which were 38% smaller, and kelp-fed abalone had gonads which were 75% smaller than those of the abalone fed on diets containing soya meal. The increased gonad mass in abalone fed on diets including soya meal could be attributed to phytoestrogenic activity, as a result of the presence of isoflavones found in the soya plant; this remains to be tested. The use of soya in brood stock diet development is advised. The influence of dietary protein to energy ratio (1.41 – 2.46 g MJ⁻¹) on growth and gonad size was tested. Protein and energy levels within the ranges tested (22 and 33% protein; 13.5 and 15.6 MJ kg⁻¹) did not interact to influence growth rates of cultured H. midae. GBI increased from 50.67 ± 4.16 to 83.93 ± 9.35 units as a function of dietary protein to energy ratio (y = 42.02 x⁰·⁸¹; r² = 0.19; regression analysis: F₁¸₃₈ = 8.9; p = 0.005). In addition, protein level influenced gonad size, with gonad growth being greater in abalone fed the high protein diet (factorial ANOVA: F₁¸₃₂ = 7.1, p = 0.012). Canning yields were reduced by 7% when the protein content was increased, while increasing the quantity of dietary energy improved canning yields by ~ 6% (one-way ANOVA: F₁¸₂₈ = 14.4, p= 0.001). The present study provided evidence that although growth rates are varying seasonally, reproductive investment is not hindering weight gain. Gonad growth can be influenced if desired by farms, depending on the level of soya inclusion, as well as the protein to energy ratio in the diet. Monthly variation in growth and gonad size, as well as the influence of diet on gonad growth were highlighted, and the implications for farm application and further research were discussed.]]> Wed 12 May 2021 19:35:49 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5357 Wed 12 May 2021 19:16:47 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5275 Wed 12 May 2021 16:51:30 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5234 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.]]> Wed 12 May 2021 15:54:00 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5382 0.05).]]> Wed 12 May 2021 15:50:14 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5384 Thu 13 May 2021 15:44:25 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5271 Thu 13 May 2021 07:23:07 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5335 Thu 13 May 2021 07:17:06 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5325 Thu 13 May 2021 02:46:10 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5316 Thu 13 May 2021 01:48:14 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5274 Thu 13 May 2021 01:47:33 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5215 Thu 13 May 2021 01:34:54 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5270 Sun 16 Jun 2024 07:30:41 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:31344 Mon 06 May 2019 15:28:07 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:27629 Mon 03 Jul 2023 14:13:59 SAST ]]>