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Provide shade for reproducing ewes continued from p. 7 AQUAPONICS using waste water for profit Aquaculture in South Africa has not yet realised its full potential due to the fact that traditional agricultural industries have always been pervasive on the South African agricultural landscape. Another reason why opportunities for aquaculture are often overlooked is due to the fact that South Africa is basically a semi-arid country with relatively low rainfall. This lack of water could make it difficult to sustainably produce fish commercially. There is a need to shift to sustainable aquaculture practices using newer technologies that will optimise the use of water. One approach would be to integrate the aquaculture system with other agriculture based industries. Aquaponics, which integrates hydroponics (growing plants without soil) with aquaculture (fish farming), is a good example of a potentially successful integration. The integration of fish and plants increases diversity and thereby enhances system stability. Aquaponics can also be used to produce large quantities of food in very small spaces in an environmentally friendly way. The prin- usually to feed or drink water. Lambs born in paddocks where shade was provided tended to be heavier at birth than contemporaries born in control paddocks (3.87 vs. 3.77kg respectively). It has to be conceded that the pregnant ewes were subjected to the respective treatments for only a short period of approximately 2 weeks before lambing started. The positive effect of shade on lamb birth weight could possibly have been enhanced if the animals were subjected to the experimental conditions over a longer period, particularly during January and the earlier part of February as well. The latter months are regarded as being the months with the highest maximum temperatures at the experiment site. In overseas studies, it was AgriPROBE September 2007 ciple of the integrated system is to optimise the utilisation of nutrients derived from aquaculture for agricultural use. Since 1987, an integration of aquaculture and agriculture has been investigated in South Africa to introduce fish and vegetable production in the same system. This aquaculture model has been well practised in developed countries such as Asia. In South Africa it could be established if sufficient expertise can be built for technology transfer. A farm at Saasveld (George) is practicing aquaponics at present. The system has been operating since 2004. It is a closed recirculating system where breakdown products derived from the fish wastes is used as a nutrient source for the plants within the system. Selecting the suitable fish species for an aquaponics system is very important. In aquaponics the fish and plants selected for aquaponic system should have similar needs as far as temperature and pH is concerned. Catfish and tilapia were selected for production at Saasveld. As a general rule, warm water fish and leafy crops such as lettuce and herbs will do the best, however fruiting plants such as found that chronic heat stress during pregnancy is associated with foetal growth retardation, resulting in a decline in lamb birth weight, and an impairment of the viability of lambs. However, the survival of lambs was not improved by the provision of shade in this experiment, as climatic conditions were not extreme. Lambs born in shaded paddocks were 3.8% heavier at weaning than those born in control paddocks (21.9 vs. 21.1 kg respectively). The provision and distribution of drinking water for livestock is a major challenge on cropping farms in the Western and Southern Cape. According to the results of this study, the water needs of a 1000 ewe flock may be reduced by >800l/day over the summer period, simply by providing shade to reproducing ewes. Shade also had a beneficial effect on the growth of lambs to weaning, while results from the literature suggested that it would also benefit birth weight and survival under more extreme climatic conditions, as are occasionally experienced in South Africa. Predictions regarding global warming suggest that the Western Cape could become prone to more extreme climatic conditions and fluctuations in future. A study to quantify the effects of natural tree shade on the production and welfare of extensive sheep flocks is being planned, because of these evident benefits listed above, and also because of the alleged impact of climate change in the foreseeable future. Dr Carel Muller & Prof Schalk Cloete Institute for Animal Production CarelC@elsenburg.com; SchalkC@elsenburg.com 8
Refiloe Thobejane, Institute for animal produc tion 9 tomatoes and peppers will also be viable, depending on the stocking density of the fish in a system. Factors that make catfish and tilapia suitable candidates for aquaponics: • Tilapia is a warm-water species that grows well in a recirculating tank culture. Furthermore, tilapia is tolerant of fluctuating water conditions such as pH, temperature and dissolved oxygen. Catfish is also a suitable candidate because of tolerant to overcrowding and a poor water quality. • Plants that will do well in any aquaponics system include any leafy lettuce, spinach, basil, mint and chives. • Plants that have higher nutritional demands and will only do well in a heavily stocked and well established aquaponic system include tomatoes, peppers, cucumbers, beans and peas. How does Aquaponics Work? In aquaponics, the nutrient-rich waste-water from recirculating aquaculture provides a food source for the growing plants and the hydroponic beds provide a natural filter for the water fish live in. Gravity drains the water back to the fish dams. This creates an ecosystem where both plants and fish can thrive. Aquaponics is the ideal answer to a fish farmer’s problem of disposing of nutrient rich water and a hydroponic grower’s need for nutrient rich water. The main objective being to investigate the most efficient application of integration of aquaculture with agriculture by utilizing nutrient rich water discharged from recirculating system to irrigate vegetable crops. Refiloe Thobejane Institute for Animal Production e-mail: RefiloeT@elsenburg.com Doctor Do-lots: Sewellen Davey receives Soga medal Dr. Sewellyn Davey, State Veterinarian at Mooreesburg, recently received the Soga medal for exemplary community service, not only in her state vet area, but also to the veterinary community of the Western Cape, which she has faithfully served as honorary Secretary of the Western Cape Branch of the SA Veterinarian Association and Livestock Health and Production Group for the past two decades. Apart from serving communities, Sewellyn demonstrates her empathy and care to individuals in a very tangible way, such as an incident recently with the illegal movement of a pony into the Animal Horse Sickness surveillance area. Biscuit had been purchased for the 6 th birthday of a girl who suffers from mitochondrial neuromuscular dystrophy and weighs 16 kg. She has always wanted a horse and as she had been able to remain out of hospital for more than 6 months, her parents bought her this horse. The Equine Practitioners Group is in the process of laying a charge against the seller as he wrongly informed the girls parents that no special requirements or permits were needed to bring the horse to them in the Malmesbury district. Biscuit was sent off to stand quarantine in the protection zone, leaving a very sick girl extremely disappointed. Sewellyn went out of her way to find a replacement. A very kind farmer is lending the girl a pregnant mare called “Ruby Red” and she will be able to keep the foal. Dr Sewellyn Davey, State Veterinarian at the Moorreesburg Office. AgriPROBE September 2007
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