Abstract
Data on 102 progeny of New Zealand White (NZ), Chinchilla (CH) and Dutch (DU) breeds of rabbits and their crossbreds obtained from birth to 14 weeks were used for this study. Genotype and feeding regime were the factors of interest. The genotypes were New Zealand White x New Zealand White (NZxNZ), Chinchilla×Chinchilla (CHxCH), Dutch×Dutch (DU×DU), New Zealand White x Chinchilla (NZxCH), New Zealand White x Dutch (NZxDU) and Chinchilla×Dutch (CHxDU).The feeding regime consists of ad libitum feeding (A), 14 hours feed restriction/day (B), 10 hours feed restriction/day (C) and 6 hours feed restriction/day (D). The experiment was conducted at the National Agricultural Extension Research and Liaison Services (NAERLS) Skill Acquisition Farm, Ahmadu Bello University, Zaria-Nigeria. The traits studied at pre-weaning were litter size at birth (LSB), litter weight at birth (LWB), litter size at week 2 (LSW2), litter body weight at week 2 (LBW2), litter size at week 4 (LSW4), lit
CHAPTER ONE
INTRODUCTION
1.1 Background Information
Variations exist in the growth performance of different breeds of rabbit. These variations are attributed to genetic and environmental factors. Environmental variations result from managerial, climatic and nutritional factors. Ibe and Nwakalor (1987) indicated that body size and conformation traits are highly heritable traits. This suggests that differences are expected among different genotypes. Several genetic factors such as breed, litter size, weaning age and sex as well as non-genetic factors such as diseases, season, temperature, housing and feeding have been noted to influence post-weaning growth performance of rabbits (Afifi and Emara, 1988). The productivity of an animal is therefore, largely determined by the interaction between genotype and environment (Chineke and Owosangba, 1999). Post-weaning growth is important in the economics of rabbit production, since it influences the rate of attainment of market weight. Kabir et al. (2012) reported that New Zealand White rabbit were superior for litter size at birth and at weaning, but Chinchilla breed is the best for individual weight at birth and at weaning as well as milk yield and mothering ability. Body weight and body measurements are good indicators of growth performance in domestic animals including rabbits. Body weight and body measurements are used to characterize rabbit breeds, contrast variation in size and shape (Shahin and Hassan, 2000) and estimate carcass and body weight (Oliveira et al., 2005). Rabbits need less space and feed due to small body size, shorter generation interval, high prolificacy, faster growth and high feed conversion efficiency which are characteristics that makes it a suitable meat producer (Orheruata et al., 2006 and Kabir et al., 2011). These qualities make rabbit production a panacea to animal protein deficiency in developing countries (Obike et al., 2010). Rabbits are conventionally fed ad libitum (concentrate and forage) to enhance their growth and reproductive performance (Bawa et al., 2007). The recent phenomenal rise in the cost of feeds and feeding stuffs in most parts of the humid tropics have forced farmers to now engage in indiscriminate feed restriction programmes, aimed majorly at reducing cost of production and consequently increasing profitability (Boisot et al., 2003). Reports from the temperate regions have indicated that feed restriction reduces post-weaning digestive disorders and improves feed efficiency (Boisot et al., 2003; Gidenne et al., 2003 and Boisot et al., 2004). Boisot et al. (2003) reported that a feeding level of 60% was more efficient in reducing the negative impact of epizootic rabbit enteropathy syndrome conditions. Gidenne et al. (2003) indicated that mortality and morbidity were significantly reduced during feed restriction (a feeding level of 80% and 70%, respectively). Biobaku and Adegoke (1999) as cited by Yakubu et al. (2007) observed no significant difference in mean daily body weight gain among rabbits fed ad libitum and those fed for 8 and 16 hours, respectively. Therefore, unguided practices could further deteriorate this situation. Some researchers have advocated that growth traits of chicken are affected by feed restriction (Ibe and Nwachukwu, 1988).1.2 Justification
There is dearth of information on the effect of feed restriction on growth traits of rabbit in literatures except perhaps on body weight gain. Information on the effect of feed restriction on growth traits is particularly important in the tropics as animal productivity is generally low in this area compared to the temperate regions. A study to investigate whether or not feed restriction could influence growth traits of rabbits is then necessary. Forages, on the other hand, are scarce and lignified during dry seasons leading to fluctuations in body weight of forage fed animals including rabbits and can influence their growth rates at such times. Therefore, selection of genotypes that can thrive well under limited feeding conditions is thus necessary for sustainable production. Restricted feeding induces compensatory growth by realimination and increases feed efficiency (Tumova et al., 2003 and Dalle Zotte, et al., 2005) and body fat can be reduced (Washburn, 1990). Early feed restriction helps to address problems associated with early life fast growth rate such as increased body fat deposition, high incidence of metabolic disorders and high mortality (Urdaneta-Rincon and Leeson, 2002; Gidenne et al., 2003; Hassanabadi and Nassiri, 2006). Reports on the effect of feed restriction on the performance of chickens abound in literature (Cable and Waldroup, 1990; McGovery et al., 1999), similar investigations with rabbits especially in the tropics are not so available.
This study was therefore designed to determine the optimum combination of genotypes and feed regimes that will enhance optimum growth performance of rabbits in tropical environment.1.3 Objectives The objectives of this study were to determine the: 1. Influence of Genotype on growth performance of domestic rabbit 2. Effect of feed restriction on post-weaning growth performance of domestic rabbit
3. Relationship between the measured traits
1.4 Hypothesis Null hypothesis: Genotype and feed restriction do not have effect on post-weaning growth performance of the domestic rabbit breeds. Ho: x̅1= x̅2= x̅3…x̅n Alternative hypothesis: Genotype and feed restriction have effect on post-weaning growth performance of the domestic rabbit breeds. : x̅1 ≠x̅2 ≠x̅3…x̅n