EFFECT OF FEEDING DIFFERENT GRADED DIETARY PROTEIN LEVELS ON GROWTH RATE OF NILE CROCODILE (CROCODYLUS NILOTICUS) HATCHLINGS Masamha Blessing 1, Nyamugure Tendayi 2, Wilson Mhlanga 3, Marisa Lesley 4, Shava Everness 5, Manyame Chiedza 6, Innocent Zacharia 7 1,2,3,4,5,6 Department of Environmental Science, Wildlife & Rangeland Management Unit, Bindura University of Science Education, P. Bag 1020, Zimbabwe 7 Crocraise Farm, Kariba, Zimbabwe ABSTRACT The effect of different graded dietary protein levels on growth rate of Nile crocodile (Crocodylus niloticus) hatchlings was evaluated at Crocraise Farm. Three diets were formulated using the ratio of In-2-Croc STARTMIX LH NOV 10 (GRO25) and Tilapia fish (Oreochromis niloticus) at 70:30, 60:40 and 50:50 to give the 60%, 55% and 50% protein levels respectively. A Completely Randomized Block Design (CRBD) consisting of three dietary treatments replicated six times each was used. The six individual pens (Pen ID) were used as a blocking factor as well as replicates. Hatchlings were fed ad lib everyday for 3 consecutive months. Twenty hatchlings were sampled randomly weekly from each pen and the belly width and length were measured. Statistical data analysis was done using Genstat version 12.1. Results indicated significantly different mean belly width at (P<0.01) for the hatchlings fed with the different diets. Hatchlings fed at 60% protein level exhibited the highest belly width (9.321cm). The means for mass and length were not significantly different for the 60% and the 55% diet at (P>0.05). The 60:40 ratio is recommended for feeding the crocodile hatchlings at Crocraise Farm. Keywords: Crocodile Hatchlings; Protein; Breast Width; Breast Length; Weight I. INTRODUCTION The Nile crocodile is of considerable economic importance as its hide is in great demand in the leather trade hence it is the most commercially utilized species of crocodilians (Patterson, 1987; Collins, 1995). In 1983 Zimbabwe s crocodile population was transferred to Appendix II (ranching) of the Convention on International Trade of Endangered Species (CITES) (Child, 1987). Crocraise farm was founded in the year 2002 mainly for captive rearing of the C. niloticus for the hide. Crocodile hatchlings feed mainly on small fish and aquatic invertebrates whilst sub adults and adult s animals feed on fish. Large crocodiles feed on terrestrial mammals including livestock or even humans (Ross et al., 1992). Growth rates of crocodilians are rapid during the first few months of their life and require feeding at least 6-7 times a week. In two experiments done by Webb et al.,(1983) using Crocodylus johnstoni, it was found that there were no significant differences in growth rates between crocodiles fed daily and those fed five days per week. However Webb et al., (1991) hypothesized that the physiological mechanism associated with digestion and assimilation may not function as efficiently when the stomach is repeatedly filled to capacity as occurs in farm raised animal. According to Garnett (1992), A 123 P a g e
typical juvenile crocodilian will consume about 15-20 percent of its body weight of food every week at constant temperature of 32ºC. Once individuals reach sub adult size they only need to consume 8-10% of their body weight per week. C. niloticus perform well when fed a diet that is high in protein as research suggests that crocodilians utilize protein over fat as an energy source, (Hutton and Webb, 1994; Smith and Marais, 1994). It is very important to adhere to a high protein and calcium diet for hatchling and juveniles less than a year old, as they are susceptible to disease and mortality, (Hutton and Jaarsveldt, 1989; Webb and Monalis, 1989).While protein may be used partially as a source of energy, its main purpose in nutrition is to provide amino acids that are used in the synthesis of the body s own protein for growth of body tissue. The crocodile farming industry requires diets that result in high feed conversion efficiencies so that growth rate is increased and profit margins are increased. The feeding strategies employed by farms will have a direct influence on cost of production. Identifying the optimal feeding strategy for animals fed with manufactured feed that minimizes feeding costs and reduces labour inputs and allows for growth at acceptable levels will improve farm profitability (Davis, 2001). Crocodiles are economically feasible where sufficient quantities of fish, offals or waste from fisheries industries, abattoirs, poultry farms, game meat and other alternative meat sources are readily available (Roth and Merz, 1998). In a study done by Garnett (1988), on the digestion, assimilation and metabolism of captive estuarine crocodiles (Crocodylus porous), protein digestion was adversely affected by high levels of dietary fat. It has been estimated that 42-45% of the operating costs of crocodile production is accounted for by feed (Treadwell et al., 1991). Feed costs are extremely variable between farms, mainly due to variation in the location and source of protein. At Crocraise Farm production cost are high as a result of slow growth rates, poor feed conversion and inadequate protein supplies. This study is expected to generate knowledge on the best protein level that will reduce the cost of feed resulting in hatchlings reaching the belly width and length size required by the market. They will be harvested early thereby saving cost of feeding. High protein diets of at least 50 to 60% are appropriate for crocodile captive breeding. II. MATERIALS AND METHODS 2.1 Study Site Crocraise crocodile farm is located in Kariba in the Mashonaland West Province of Zimbabwe on the north eastern border with Zambia. Crocraise rears its crocodiles in outdoor pens that are constructed with concrete. The Kariba shorelines are dominant supplier of crocodile eggs in the country. The climate is generally tropical with three reasonably distinguishable seasons. A hot rainy season from late November to March, a cool dry season from May to August and a very hot dry season from September to November. Annual rainfall ranges from 400mm (16 inches) in the Valley to about 700mm (28 inches) on the plateau. Winter temperatures rarely go below 13 C; day time temperatures vary around about 40 C during the hot months. Lake Kariba lies in the geographically leached out Gwembe Rift Valley on the Zambezi River at an altitude of 484meters. 2.2 Research Design and Sampling A Completely Randomized Block Design (CRBD) was used where the blocking factor was the different pens and the diets with different protein levels were the treatments (60%; 55% and 50% CP). Hatchlings were randomly sampled weekly to measure the weight breast width and length. The hatchlings were fasted for at least 24 hours prior to measuring to allow for complete emptying of the stomach. The crocodiles were fed for five 124 P a g e
days and then fasted over the weekend to assist in complete digestion of feed in their system. The weight, belly length and width were recorded once a week over a period of twelve weeks. 2.3 Experimental Diets Three diets containing different levels of protein that is, 60%, 55% and 50% were be prepared using Tilapia fish (Oreochromis niloticus) mixed with In-2-Croc STARTMIX LH NOV 10(GRO25) hatchling commercial concentrate. The fish diet were mixed together with In-2-Croc STARTMIX LH NOV 10 (GRO25) (Class: Concentrate for a Complete Crocodile Grower Feed) to make a complete ration for the hatchlings. The 50:50 rations was used as the control as per manufacturer specification. The In-2-Croc STARTMIX LH NOV 10 (GRO25) was mixed at a ratio of 50% fish and 50% startermix for optimal growth. The diets were minced using a disc with 1.2 cm diameter holes. The hatchlings were fed once daily in the afternoon a rate of 15% of body weight during the entire three months period and feed quantity was readjusted after every seven day sampling period depending on the growth of the hatchlings. Table1: Nutrient Composition of the Formulated Experimental Diets. Diet Dry Matter Crude Protein (%) Crude Fiber Fat Ash Ca P 70:30 45.8 60 0.9 21.5 11.6 3.61 2.66 60:40 47.6 55 0.7 21.5 11.9 3.46 2.94 50:50 48.5 50 0.5 21 12.2 3.30 2.99 2.4 Management of Hatchlings The study was conducted in the hatchling section of the farm from February to April 2011. Six pens measuring 36 m 2 each were used for crocodile hatchling rearing with a stocking density 210 hatchlings in each pen. Each of the pens had hot water pipes designed to maintain the C. niloticus hatchlings body temperature and also to aid in fast digestion of feed. The water inside the pens was maintained at a temperature of 32 0 C to avoid temperature stress. Temperatures in the pens were recorded three times each day to monitor temperature changes. Feeding was ad lib. A one meter butterfly brand superior tailoring rule was used for measuring the length and belly width of the hatchlings. Mettler Toledo mode Hawk digital scale was used to weigh the feed that was given to experimental hatchlings. An electric feed mincer was used to prepare the feed. 2.5 Statistical Data Analysis The data on weight, breast width and lengths were tested for normality using the Normal Q-Q Plot and was statistically analysed using the General analysis of variance in SPSS Version 16.0. Least significant difference was used for Post hoc tests. Residual plots were used to test for homoscedasticity. Line graphs were used to depict the growth trends of the hatchlings over 12 weeks. 125 P a g e
III. RESULTS AND DISCUSION Table 2: Mean Crocodile Weight, Belly Width and Belly Length for the Different Diets at Different Weeks Week Diet Weight (g) Belly Width (cm) Belly Length (cm) 1 A 123.841 (±19.271) 7.825 (±0.379) 39.600 (±1.383) B 116.600 (±19.056) 7.564 (±0.286) 38.943 (±1.045) C 127.581 (±22.959) 7.933 (±0.292) 39.400 (±1.065) 2 A 193.875 (±20.212) 7.050 (±0.252) 39.587 (±0.922) B 218.400 (±20.212) 8.075 (±0.252) 41.325 (±0.922) C 224.000 (±20.212) 8.400 (±0.252) 41.937 (±0.922) 3 A 205.000 (±20.212) 7.510 (±0.258) 42.099 (±0.941) B 214.500 (±20.212) 8.535 (±0.253) 43.503 (±0.923) C 218.250 (±20.212) 8.213 (±0.270) 42.260 (±0.984) 4 A 191.625 (±20.212) 7.962 (±0.252) 41.408 (±0.922) B 174.500 (±20.212) 7.187 (±0.252) 40.863 (±0.922) C 240.000 (±20.212) 8.950 (±0.252) 46.238 (±0.922) 5 A 177.625 (±20.212) 8.601 (±0.332) 44.300 (±1.213) B 158.125 (±20.212) 5.684 (±0.579) 38.329 (±2.115) C 172.500 (±20.212) 7.425 (±0.252) 41.738 (±0.922) 6 A 209.850 (±20.212) 7.675 (±0.252) 44.062 (±0.922) B 261.000 (±20.212) 8.475 (±0.252) 46.838 (±0.922) C 222.275 (±20.212) 9.308 (±0.421) 46.239 (±1.537) 7 A 213.875 (±20.212) 8.900 (±0.252) 45.925 (±0.922) B 270.375 (±20.212) 9.950 (±0.252) 48.338 (±0.922) C 218.200 (±20.212) 9.050 (±0.252) 46.100 (±0.922) 8 A 298.175 (±20.212) 10.425(±0.292) 50.592 (±1.065) B 325.825 (±20.212) 10.673(±0.261) 51.410 (±0.952) C 344.875 (±20.212) 10.350(±0.253) 48.912 (±0.923) 9 A 222.875 (±20.212) 9.0870 (±0.252) 45.863 (±0.922) B 330.225 (±20.212) 10.175 (±0.252) 49.550 (±0.922) C 307.250 (±20.212) 9.9250 (±0.270) 49.025 (±0.922) 10 A 328.375 (±20.212) 8.8580 (±0.270) 49.159 (±0.984) B 376.100 (±20.212) 9.3050 (±0.316) 46.391 (±1.152) C 387.750 (±20.212) 9.8680 (±0.579) 45.783 (±2.115) 11 A 343.718 (±20.212) 10.397 (±0.256) 52.179 (±0.934) B 296.625 (±20.212) 9.7370 (±0.252) 50.088 (±0.922) C 265.950 (±20.212) 11.075 (±0.252) 51.663 (±0.922) 12 A 367.805 (±19.964) 9.5730 (±0.249) 50.073 (±0.911) B 398.750 (±20.212) 10.825 (±0.252) 52.625 (±0.922) C 421.900 (±20.212) 11.200 (±0.252) 52.812 (±0.922) Note: Diets A-50:50; B- 60:40; C-70:30 There were no significant differences in the belly width and length of crocodile hatchlings between the three diets in the first and second week. Generally the belly width fell in 5 th and 6 th week across the three diets. In the 70:30 diet mean belly width decreased from 47.2 cm to 44.1 cm and then started to increase again. The 50:50 diet had the lowest breast width and length. At week 5, the breast width and lengths of 70: and 60:40 diets dropped markedly and immediately rose again. Diet 70:30 had the highest breast width and lengths over 12 weeks. 126 P a g e
Both the belly width and the length of the hatchlings remained almost similar throughout the twelve weeks of the research (Fig 4.1). Mass for the 2 nd and the 3 rd week remained unchanged; however the mass of the hatchlings began to fluctuate mainly in the 5 th week, 9 th week and the 11 th week. Dietary protein is always considered to be of primary importance in crocodilian feeding (Jauncey and Ross, 1982), thus sufficient supply of dietary protein is needed for rapid growth). In the present study, results revealed that the optimum dietary protein level is the 60% protein in the diet for it resulted in the highest mean belly width which is of utmost importance when harvesting animals for the market. The larger the belly width, the higher the price of the skin on the market. Crocodilians also fare better when fed a diet that is high in protein, as research suggests that crocodilians utilize protein over fat as an energy source (Hutton and Webb 1994; Smith and Marais 1994). The diet of 60% protein level is recommended for feeding the C. Niloticus hatchlings since it exhibited the highest growth rate. Scope for further research needs to focus on the influence of various stocking densities and clutch (genetics) on growth performance of crocodile hatchlings. The drop in mass in the 5 th week of the experiment was due to storms that occurred in that week which had strong winds that caused flapping of the shed cloths that covered the hatchling pens. This phenomenon caused disturbances and stress to the hatchlings putting them off feed for that particular week. Thus disturbances in the feed intake affected their body mass gain. It has been observed that soon after being disturbed crocodiles exhibit an unusual behaviour of piling to escape and they do not feed (Hoetwoe, 1987). According to Davis (2001), growth rate of crocodiles is highly influenced by a number of factors that include environmental, management and behaviour. In the 9 th week, there was also a fall in the weight gain, this can be attributed to the fall in the temperatures in the crocodile pens that resulted from a shortage of coal used to heat the water that circulates in the pens. Hernandez (1983) found out that in crocodilians the ideal temperature for maximum appetite and growth may be as high as 32 C.This implies that too low a temperature or too high will have an effect on the feed intake. Crocodiles are very sensitive to unusual sounds and temperature (too high or too low) especially when young. These factors affect their appetite (Games, 1990). The mean comparisons for the growth parameters for the different diets showed that the 60% (60:40 diet) 127 P a g e
protein level had the highest weight gain. However in Zimbabwe reports by van Vuuren (1993) indicated no significant difference in growth when three day old Nile crocodiles were fed pellet/ground meat diets in ratios of 30:70, 50:50, and 70:30 over a seven month period. These differences in the results could have been attributed to the differences in the concentrate feed used in the researchers study and the one done by (van Vuuren, 1993) and also the difference in the meat sources used. REFERENCES [1] Child G. (1987). The Management of Crocodiles in Zimbabwe. In: G.J.W. Webb, S.C. Manolis and P.J. Whitehead (Eds). Wildlife Management: Crocodiles and Alligators. Surrey Beatty and Sons, Chipping Norton, Australia. [2] Collins L. (1995). Crocodilian Skin Production 1992 1993. Crocodile Newsletter 15.7. [3] Coulson R.A. and Hernandez.T (1983). Alligator Metabolism: Studies on Chemical Reactions in Vivo: Comparative Biochemistry and Physiology, V. 74 B. [4] Davis B.M. (2001). Improved Nutrition and Management of Farmed Crocodiles from Hatching to Harvest. A Report for the Rural Industries Research and Developement Corporation. [5] Games I. (1990). Growth curves for the Nile crocodile as estimated by skeleton - chronology. P roc. 10 th Workng Group Meeting of the Crocodile Specialist Group of the Species Survival Commission of IUCN. IUCN Gland, Switzerland. [6] Garnett, S.T (1988). Digestion, Assimilation and Metabolism of Captive estuarine crocodiles, crocodylus porosus Comparative Biochemistry and Physiology A Physiology 90, 23 29. [7] Garnett, S.T and Muray R.M (1986). Parameters affecting the growth of the Estuarine crocodile, Crocodylus porous, in captivity, Aust, J. zool. 34:211-223. [8] Hoetwoe, H.F. (1987). Ecology of Reptiles. Surrey Beatty and sons PVT limited, Australia. [9] Hutton, J. M. and Webb G. J. W., (1994). The principles of farming crocodiles. Proceedings of the 2nd Regional meeting of the Crocodile Specialist Group. Darwin, Australia March 1993. [10] Hutton, J.M., (1987). Population ecology of the Nile crocodile at Ngezi. Zimbabwe, department of biological sciences, UZ. [11] Jauncey, K. (1998). Tilapia feeds and feeding. First Edition. Pisces Press Ltd, Stirling, Scotland. [12] Ross,C.A and Garnett,S.(1992).Crocodiles and Alligators, Blitz Edition, Leicester [13] Roth, H.H and Merz, G. (1997).Wildlife resources a global account of economic use. Springer, Berlin. [14] Smith, G.A. and Marais,J.(1994). Stress in crocodiles-crocodiles. Proceedings of the 12 th Working Meeting of the Crocodile Specialist Group, IUCN-The World Conservation union,gland,switzerland.volume2. [15] Treadwell, R., L. McElvie, and G.B. Maguire. (1991). Pages 63-70 in Profitability of selected aquaculture species. ABARE discussion paper 91.11, Canberra. [16] van Vuuren, R. A. (1993). A Review and Update of the Nutrition of Nile Crocodile (Crocodylus niloticus) from Birth to One Year of Age and the Development of Artificial-type diets for Juveniles in Zimbabwe 1989 to 1994. [17] Wallace, K.M and Leslie, A.J. (2008).Diet of the Nile crocodile (Crocodylus niloticus) in the Okavango Delta, Botswana. Journal of herpetology. [18] Webb, G.J.W and Monalis, S.C., (1989) Australian crocodiles: A natural history, New Holland Publishers: Sydney. 128 P a g e