Nutritive value of variously processed rubber seed meals: growth and reproductive performance studies using the laboratory rat as model for pigs

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The study involved evaluating methods of processing raw rubber seeds and the nutritional quality of the processed rubber seed meals as dietary ingredients using the laboratory rat, with specific application to the growing pig in terms of growth and reproductive performance. The work was conducted in four separate experiments. The first experiment aimed at evaluating four simple methods of processing in terms of chemical compositions and energy values of the resultant rubber seed meals. The raw rubber seeds were de-hulled, partially sun-dried for 24 h and divided into five lots, each lot receiving one of four processing methods, namely; sun drying, soaking in water, boiling in water and roasting in addition to the raw or unprocessed rubber seed. The method of processing significantly (P< 0.05) affected the proximate compositions, the mineral contents, amino acid profiles and the metabolizable energy concentrations of the resultant rubber seed meals. Despite its potential as a source of protein for animals, fresh rubber seed meal was shown to contain a toxic factor, hydrogen cyanide (60 mg/100g DM). Imposition of the various processing methods, however, significantly reduced the hydrogen cyanide contents in the resultant rubber seed meals, with the boiled RSM registering the lowest HCN content. The second experiment determined the growth performance and physiological parameters of laboratory rats fed the variously processed rubber seed meals (RSM). Thirty six growing rats (18 males and 18 females) were randomly allotted into 6 groups and were fed a control diet with no RSM and 5 other diets containing 100 g of the raw RSM and the 4 resultant processed rubber seed meals. The feeding of diets incorporating 100 g of the various types of rubber seed meals had no significant (P > 0.05) effect on feed intake, body weight gain and feed conversion efficiency, as compared to rubber seed meal-free (control) diet. However, water consumption by rats was significantly (P< 0.05) influenced by the dietary treatments. No deaths or health-related problems were recorded during the course of the study. Dietary treatments had significant (P< 0.05) impact on relative weights of the liver, heart and lungs but not on the kidney, spleen and intestinal weights. Treatment differences in blood cellular elements and biochemical indices were not significant (P> 0.05), except the WBC count, MCV value and blood sugar levels. With the exception of the RoRSM diet, cost per gram feed and feed cost per gram live weight gain were slightly reduced when the rubber seed meals were used, Seasonal variations in the prices of feedstuffs such as maize and soyabean meal would make the use of alternative feedstuffs such rubber seed meal in animal diets more attractive In experiment three, the use of rat as a model animal for allowing the determination of the reproductive performance in the pig, was evaluated. Eighteen female rats with an average initial body weight of 153.9 g were randomly allotted into 6 groups and fed a control diet with no RSM and 5 other diets containing 100 g each of the raw RSM and the 4 resultant processed rubber seed meals. With the exception of rats on the RoRSM diet, all other rats recorded successful mating and pregnancies. There were no significant (P> 0.05) difference in the gestation length and the pregnant rats delivered normally. No external malformations were observed in any of the pups delivered. No significant (P> 0.05) differences in the maternal body weight, litter size, pup birth weight and number of pups weaned were observed. However, dietary treatments significantly (P< 0.05) influenced weaning weight and post-natal mortality of pups, with those on the control and the SDRSM diets recording the highest mortalities. The present findings indicate that the various types of rubber seed meals evaluated in this study, do not pose any significant reproductive toxicity or complications in pregnancy and delivery in rats. The final experiment generated data on the effect of graded levels of the boiled-RSM (BRSM), identified to be the best quality rubber seed meal from the three initial studies, on growth performance and economy of gain of rats. Twenty four rats (12 males and 12 females) were randomly selected and allocated to 4 dietary treatments containing varying amounts of BRSM (0, 50, 100 and 150 g RSM kg-1) in a complete randomized design such that there were 6 rats (3 males and 3 females) with one rat per replicate. Feed and water were provided ad libitum for 4 weeks. The addition of the graded levels of the BRSM to rat diets significantly (P< 0.05) influenced feed intake and water consumption. However, the inclusion of BRSM in diets had no significant (P> 0.05) effect on body weight gain and efficiency of feed utilisation. In addition, there were no health-related problems nor mortalities attributable to level of BRSM in the diet. Examination of several organs at the termination of the 4-week study revealed no macroscopic deviation from the normal in terms of gross tissue changes. Also, dietary BRSM had no significant effect on the relative organ weights of the experimental animals. The cost per gram of feed declined as more BRSM was included to replace soya bean meal. The diet that contained the highest amount of BRSM was cheaper. Furthermore, feed cost per gram live weight gain was lowest for rats on the 150 g kg-1 diet and highest for the 50 g kg-1 diet. Inclusion of 150 g BRSM kg-1 diet might be beneficial in terms of cost effectiveness.
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the award of the Degree of Master of Philosophy in Reproductive Physiology.