The effect of Gracilaria gracilis (Rhodophyta) on growth and behaviour of farmed abalone Haliotis midae when included in the abalone diet
- Authors: Madlala, Njabulo Praiseworth
- Date: 2024-04-04
- Subjects: Haliotis midae South Africa , Mariculture , Abalones Feeding and feeds , Abalones Growth , Abalones Behavior , Feed utilization efficiency , Integrated mariculture , Gracilaria gracilis
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435332 , vital:73148
- Description: Abalone feed naturally on algae, but commercial abalone farms rely on formulated feed. The inclusion of algae with the formulated feed in the diet improves growth, health and feed conversion ratio (FCR). However, the kelp that is currently included in the feed is wild harvested and this resource is limited and under increasing pressure. Thus, there is a need to develop an alternative sustainable source of algae. The aim was to use Gracilaria gracilis algae (that was produced with mussel in an integrated multitrophic aquaculture system; IMTA) which was then included into abalone feeds and its influence on abalone growth, FCR and behaviour was evaluated. Sea-based G. gracilis was harvested off an existing IMTA system, manufactured into Abfeed® and fed to abalone to determine growth efficiency. Abalone (30 - 40 g abalone-1) originated from the same cohort at Whale Rock Abalone Farm (Pty) Ltd., Hermanus. Abalone were fed either: Abfeed® S34 only with no algae (G0, the control); Abfeed® with sea-based IMTA G. gracilis included in the formulated feed at 0.75 % (G0.75); 1.50 % (G1.50); 3.00 % (G3.00); 6.00 % (G6.00); and 12.00 % (G12.00) inclusion; and Abfeed® S34 with fresh-live G. gracilis (cultured at Whale Rock Abalone Farm (Pty) Ltd.; Gfresh + S34s). Abalone shell length, whole body mass and FCR were measured at a four-months interval over eight months (two growth cycles). Differences in behaviour (i.e., level of activity and feeding activity) were also monitored and comparing between treatments. There was significant difference in mean whole-body mass between treatments (RMANOVA, F(6, 29) = 3.71, p = 0.007). Abalone fed the diet with the highest inclusion of dry G. gracilis (G12.00) had a lower mean whole-body mass value (74.13 ± 2.94 g abalone-1) than abalone from all the other diets after eight months. There was a negative relationship between the condition factor and dry G. gracilis inclusion rate for the first growth cycle (y = - 0.0044x + 1.222, R2 = 0.24, p=0.009) and second-growth cycle (y = - 0.0096x + 1.2233, R2 = 0.51, p = 0.00002). Abalone receiving fresh G. gracilis were less quiescent and more alert on the first hours after food distribution (p < 0.05). The same proportion of abalone with G0, G0.75, and G6.00 G. gracilis inclusion were feeding all along the 9 hours post-feeding. This study will potentially reduce the dependence of abalone farms on wild-harvested kelp in formulated feed. This will improve their contribution to a more environmentally sustainable global production of sea food products, making them more competitive on international markets. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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- Date Issued: 2024-04-04
Effect of dietary inclusion of Moringa oleifera Lam leaf meal on feed conversion efficiency, meat quality, fatty acid composition, shelf life and consumer health-related perceptions of pork
- Authors: Mukumbo, Felicitas Esnart
- Date: 2013
- Subjects: Moringa oleifera , Meat -- Quality , Feed utilization efficiency
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11827 , http://hdl.handle.net/10353/d1016071 , Moringa oleifera , Meat -- Quality , Feed utilization efficiency
- Description: The objective of the study was to determine the feed conversion efficiency (FCE), carcass characteristics, physico-chemical quality, fatty acid (FA) composition and shelf life of pork from pigs fed diets containing either 0% (T1), 2.5% (T2), 5% (T3) or 7.5% (T4) Moringa oleifera leaf meal (MOLM). Consumer health-related perceptions on pork and fatty acids were also investigated. Twenty four crossbred Large White x Landrace pigs of both sexes at 18 weeks of age and initially weighing 71.6 kg on average were housed individually and had ad libitum access to one of the four dietary treatments for a period of six weeks. Average daily feed intake (ADFI) and average daily gain (ADG) and feed conversion ratios (FCR) were calculated as an indication of FCE and pigs were slaughtered at an average live weight of 99.6 kg. Carcass traits such as back fat thickness (BFT), carcass temperatures and pH readings taken 45 minutes and 24 hours (pH45 and pHu) post mortem were recorded. M. longissimus thoracis et lumborum (LTL) samples were taken from each carcass for the determination of lightness (L*), redness (a*), yellowness (b*), thawing loss percentage (TL%), cooking loss percentage (CL%), Warner Bratzler Shear Force (WBSF), shelf life and FA composition. Furthermore a survey was conducted amongst 80 University of Fort Hare Students to determine their health-related perceptions on pork and fatty acids as well as their pork consumption frequency using questionnaires. The FCE of pigs fed on 0-5% MOLM (T1, T2 and T3) diets did not differ significantly, but the FCE of pigs fed 7.5% MOLM (T4) was significantly (p<0.05) reduced. No significant relationship was reported between inclusion of MOLM carcass characteristics and physico-chemical pork quality. There was however a significant improvement (p<0.05) in the shelf life of the pork from MOLM fed pigs in terms of colour and odour during 10 days of refrigerated storage (at 3±1°C). There was a significant (p<0.05) reduction in the total intramuscular fat (IMF) content and the saturated fatty acid (SFA) C18:0 (stearic acid) content and an overall non-significant (p>0.05) increase in the poly unsaturated fatty acid (PUFA) content of pork from MOLM fed pigs. The possible reason for this is that the feeding of MOLM was commenced when the pigs were at an advanced age and weight. The survey revealed that the majority of interviewed students consume fresh (39.7%) and processed (32.4%) pork two to three times a week, perceive pork to be generally healthy (70%) and the second most healthy meat type (39.5%). While the majority (55.4%) were aware of the health implications of FAs they did not know which FA classes pose more of a health risk (51.3%). In conclusion2.5% and 5% of MOLM in finisher pig feed did not negatively affect FCE, carcass characteristics or physico-chemical meat quality; significantly improved pork shelf life and reduced total IMF and SFA content of pork but 7.5% MOLM negatively affected FCE; and the majority of students perceive pork to be the second most healthy type of meat and are generally aware of the health implications of FAs.
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- Date Issued: 2013