Performance of Weaner Rabbits Fed Maize Husk Based Diets With and Without Enzyme Supplementation
Chapter One
Objectives of the study
- To evaluate the performance characteristics, nutrient retention, carcass characteristics and hematological parameters of weaner rabbits fed diets in which maize husk replaced rice
- To evaluate the performance characteristics, nutrient retention, carcass characteristics and hematological parameters of weaner rabbits fed maize husk based diets supplemented with graded levels of enzyme
CHAPTER TWO
LITERATURE REVIEW
Origin and distribution of rabbits
The domestic rabbit, Oryctolagus cuniculus is a descendent of wild rabbits of southern Europe and North Africa (Brewer and Cruise, 1994). The rabbit is thought to have been discovered by Phoenicians when they reached the shores of Spain about 1000 BC. During this time the Romans spread the rabbit throughout the Roman Empire as a game animal. The Romans, like Spaniards of that time ate foetuses or newly born rabbits, which they called laurices. In their natural environment, rabbits are gregarious and prolific. They are completely herbivorous (eat only plants) and most actively forage in the twilight or in the dark.
Rabbits have been recognized to have a very important role to play in the supply of animal protein to humans, especially in tropical and subtropical areas (Carabano et al., 2000). Moreover, rabbits occupy a midway between ruminants and monogastric animals and can effectively utilize cellulose rich feed with ration containing less than 20% grain (Fraga, 1998). Rabbits have short breeding cycle, high prolificacy and better feed conversion efficiency which logically place them just below poultry (Hasanat et al., 2006). It was reported by Merino (1992) that world’s production of rabbit meat was estimated to be 1.5 million tons per annum. This would mean per caput annual consumption of 280g per person per year. In Africa, the leading rabbit producing countries are Morocco and Nigeria and both countries were reported to produce about 20,000 to 99,000 tons of meat per year (Merino, 1992).
Nutrient requirements of the rabbit
Energy
The energy requirements for various functions (growth, gestation and lactation) have received little attention. Assuming that rabbits, like most animals voluntarily adjust their feed intake to meet their energy needs, the lack of precise data on energy requirements is perhaps of less concern in rabbit diet formulation than the lack of data on requirements of most other nutrients. Lebas (1975) studied the performance of growing rabbits fed diets of different energy content and reported that 9.5 kcal of digestible energy (DE) was required per gram of body weight gain, regardless of energy content of the diet. The data suggested that a level of 2,500kcal of DE per kg of diet will satisfy the energy needs for rapid growth (Lebas, 1975).
Rabbits can efficiently digest starch, the major carbohydrate in cereal grains. High-starch diets were reported to be incompletely digested by rabbit due to rapid transit time in the gastro intestinal tract GIT (McNitt et al., 1996). Similarly, Stevens and Hume (1995) asserted that incomplete chemical digestion of starch fed to weaner rabbits resulted in rapid microbial fermentation. This is because excess starch in the gut resulted in an extremely rapid growth of microbes. If toxin-producing microbes primarily (Clostridium spiroformes) are present in the GIT, high levels of a starchy diet may result to enteritis or possibly death (McNitt et al., 1996; Jenkins, 1999). Grains processed too finely can lead to rapid bacterial fermentation of the starch and cause enterotoxaemia, thus, a coarse grind is recommended.
CHAPTER THREE
MATERIALS AND METHODS
Experimental site
The experiment was conducted at the Animal Farm of the Department of Animal Science, Ahmadu Bello University (ABU) Samaru, Zaria. The Departmental farm is located on longitude 110 9’ 45’’ N and latitude 70 38’ 8’’ E at an altitude of 610m above sea level (Ovimaps, 2012).
Source and processing of the maize husk
The chemical composition of maize husk used in the experiment is presented in Table 3.1. Maize husks were collected from boiled maize sellers within Samaru community area. The boiled maize husk was collected and sun dried to reduce the moisture content to 10%. The dried maize husk was chopped to smaller sizes using a cutlass after which it was taken to the food and nutrition Laboratory of the Department of Animal Science, Faculty of Agriculture, A.B.U., Zaria where it was milled for incorporation into the experimental diets at inclusion levels of 0, 4, 8, 12, 16 and 20% for treatments one to six respectively.
Proximate analyses
Feed samples for each of the six treatments were collected and taken for proximate analyses to determine the nutrient composition. The analysis of the maize husk and feed samples were carried out according to procedures described by A.O.A.C (1995). The dry matter (DM) content of the samples was determined based on the weight loss by oven drying at a temperature of 1000C for 24 hours. The nitrogen content was determined by macro Kjeldhal method and protein content calculated as nitrogen multiplied by 6.25(Nx6.25). The ash content was determined as the residues remaining after incinerating the samples at 5000C for 18hours in a muffled furnace. Similarly, crude fibre (CF) and ether extract (EE) were also determined according to procedures described by A.O.A.C (1995).
CHAPTER FOUR
RESULTS
Performance of Weaner Rabbits Fed Graded Levels of Maize Husk as Replacement for Rice Offal
Performance of weaner rabbits fed graded levels of maize husk as replacement for rice offal is presented in Table 4.1. There was no significant difference (P>0.05) observed in average daily weight gain for rabbits fed 0.0 and 4.0% maize husk. Rabbits fed 8.0, 12.0 and 16.0% maize husk showed similar (P>0.05) results in average daily weight gain. No significant difference (P>0.05) was observed in average daily feed intake across all dietary treatments. Feed conversion ratio (FCR) was significantly (P<0.05) affected by dietary levels of maize husk. Rabbits on the control diet and 4.0% maize husk had similar results in FCR and were significantly (P<0.05) better than all other treatments. FCR did not differ significantly (P>0.05) for rabbits fed 8.0, 12.0 and 16.0% dietary maize husk. The poorest result in FCR was observed for rabbits fed 20.0% dietary maize husk.
It was observed that rabbits fed 0.0 and 4.0% maize husk showed no significant (P>0.05) difference between each other and performed better than rabbits fed diets with graded levels of maize husk at 8.0, 12.0, 16.0 and 20.0% which performed the least in feed cost per kilogram weight gain. Mortality was observed for rabbits fed 12.0 and 16.0% maize husk while no mortality was observed in all other treatments.
Table 4.1: Performance of Weaner Rabbits Fed Graded Levels of Maize Husk as Replacement for Rice Offal
CHAPTER FIVE
DISCUSSION
Performance of Weaner Rabbits Fed Graded Levels of Maize Husk as Replacement for Rice Offal
The gradual decline in average daily weight gain with increasing levels of maize husk was attributed to the poor nutritive value of maize husk compared to rice offal. Aduku (1993) reported that maize husk contains 2.60% crude protein, 0.97% crude fat and 33.51% crude fibre while rice offal contains 6.0% crude protein, 5.60% crude fat and 31.0% crude fibre. Similarly, Maikano (2007) reported that rice offal consists of rice hulls, rice bran, rice polishing and broken rice grains. Hence, rice offal has higher nutritive value in crude protein, crude fat and minerals such as calcium and phosphorus when compared to maize husk. .
The non-significant decline in average daily feed intake with increasing levels of maize husk was in consonance with the reports of Valencia and Chavez (1997) and Philip et al. (2000). Both authors observed a non-significant (P>0.05) decline in feed intake when lignified diets were fed to pigs and calves respectively. Terry et al. (2012) observed a significant decline (P<0.05) with increasing levels of crude fibre and lignin content in grass cutter. Feed conversion ratio (FCR) and feed cost per kilogram weight gain increased as the levels of maize husk increased in the diet of the rabbits beyond 4%. The best results in both parameters were achieved for rabbits fed 0.0 and 4.0% maize husk while higher inclusion levels gave poorer results. This was attributed to the poor nutritive nature of maize husk as reported by Aduku and Olukosi (1990a). The mortality observed for rabbits fed 12.0 and 16.0% maize husk was not attributed to the experimental diet because maize husk does not contain toxic substances.
Carcass Evaluation of Weaner Rabbits Fed Graded Levels of Maize Husk as Replacement for Rice Offal
The live, dressed, skin and thigh percentages were significantly affected (P<0.05) by dietary levels of maize husk. The highest values of dressing percentage and thigh weight were observed for rabbits on the control diet and decreased significantly (P<0.05) with increased levels of maize husk. This could be attributed to the presence of ingestible fibre present (lignin) in maize husk compared to rice offal as reported by Gholizadeh and Naserian (2010). It was reported by Maikano (2007) that rice offal consisted of rice hulls, rice bran, rice polishing and broken rice grains, thus it has a higher nutritive value compared to maize husk. The weights and lengths of internal organs expressed as percentage of the live weight (heart, liver, lungs, kidney, gall bladder and the length of small and large intestines) were not significantly affected (P>0.05) by dietary levels of maize husk. This was because the experimental diets contained no toxic materials as increased sizes in visceral organs indicate poor health status of farm animals.
CHAPTER SIX
SUMMARY, CONCLUSION AND RECOMMENDATION
Summary
Two research trials were conducted to determine the performance of weaner rabbits fed maize husk based diets. In the first experiment, maize husk replaced rice offal at graded levels of 0.0, 4.0, 8.0, 12.0, 16.0 and 20.0% for treatments one to six respectively. Average daily weight gain, average daily feed intake, feed conversion ratio, feed cost per kilogram weight gain, total protein and nutrient digestibility significantly declined (P<0.05) as the levels of maize husk increased in the diets of the rabbits. Rabbits fed 0.0 and 4.0% maize husk showed the best result in all parameters studied while the worst result was observed for rabbits fed 20.0% maize husk. 20.0% maize husk which gave the poorest result in the first experiment was supplemented with enzyme at 0.00, 0.02, 0.03 and 0.04% for treatments one to four respectively and used for the second experiment. Rabbits fed diets supplemented with 0.02% enzyme showed the best result in average daily weight gain, average daily feed intake, feed conversion ratio, feed cost per kilogram weight gain, evaluation of carcass characteristics, nutrient digestibility and total protein. These parameters declined with increasing levels of enzyme thus, 0.04% enzyme showed the poorest result in all parameters studied.
Conclusion
Results obtained from the first experiment showed that the best result in final weight was obtained for rabbits fed 4.0% maize husk while the poorest result was obtained for rabbits fed 20.0% maize husk. It was observed that rabbits could tolerate maize husk up to 4.0% in their diet without negatively affecting weight gain, nutrient digestibility, carcass characteristics, feed conversion ratio, feeds cost per kg gain and haematological evaluation (total protein). Higher inclusion levels of maize husk beyond 4.0% resulted in a decline in performance with regard to nutrient digestibility, carcass and haematological evaluations. The decline in performance with increasing levels of maize husk was attributed to the indigestible fibre content of the husk compared to rice offal.
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