Data on a full diallel cross involving three rabbit breeds and its effects on some growth and reproductive traits were studied. Data on two thousand and thirteen (2,013) rabbits comprising eight hundred and five (805) purebred bunnies kindled in 60 litters and one thousand, two hundred and five (1,205) crossbred bunnies from 86 litters bred from 2010 to 2014 in five parities were first corrected for the fixed effects of sex, season of kindling and the does‘ age using the least significant differences (lsd) before the analysis was run using the Generalised Linear Model. Of the three breeds, the Chinchilla showed superior performance in both the reproductive and growth performance while the BV X CH crossbred showed superior performance in most of the economic traits that were assessed compared to the other crosses. The BV X NZ and NZ X CH crossbreds recorded significantly (p = < 0.05) higher litter size at birth (6.8±0.1) and at weaning (6.9±0.1) respectively. The heterotic effects of both the main and reciprocal crosses were quite desirable for most of the economic traits. Notable among them was the age at sexual maturity, kindling interval and mortalities which recorded varying levels of negative heterosis. The reciprocal crosses exhibited some level of superiority in the growth traits (bunny weight at birth and the post-weaning growth rate) that recorded positive heterosis. The Chinchilla and BV X CH crossbred comparatively exhibited a higher level of superiority in the general and specific combining abilities in a number of the economic traits that recorded significant differences. The positive heterotic effects encourage the application of crossbreeding schemes in rabbit production for improved productivity within the coastal savannah agro-ecological zone of Ghana.

Background of the Study
Globally, there has been an increasing demand for animal protein; more significantly, in the developing countries of sub Saharan Africa. This soaring demand for animal protein has been attributed not only to the ever-increasing global human population, but is also an acknowledgement of the essential role of animal protein in human development and well-being. Improved economic status, urbanisation and industrialisation, particularly in the developing economies have all contributed to the increased demand for protein from animal sources (Karikari, Darkoh & Deku, 2011). There have been several interventions geared towards meeting this increasing demand. These interventions include improved management and production systems, improved nutrition, efficient utilisation of genetic resources and agro-industrial by-products, as well as rise in backyard or non-commercial animal production (Onifade & Tewe, 2010). More importantly, these interventions also seek to guarantee security in food supply for the marginalised in society (Fayeye & Ayorinde, 2010).

Over the period, poultry in particular has played a significant role in this regard, although the persistent and ever-widening gap between demand and supply of animal protein has not yet been bridged. This has necessitated the need to make more use of alternative sources of animal protein via the development of non-conventional livestock. The rabbit, in recognition of its high prolificacy, rapid growth rate, early sexual maturity, short gestation period (28-31days), good ability to utilise forage feed, high meat yield, comparatively low production cost, lower space requirement, limited cultural and religious prohibitions on its production and consumption, as well as the high nutritive value of its meat, has been identified as a promising food animal (Fayeye, 2013; Obiajulu, Eze, Amadi, & Odoemena, 2016; Sivakumar et al., 2013).

Considering the potential for rabbit production in Ghana, and the success story of some neighbouring West African countries, the National Rabbit and Grasscutter Projects were initiated by Newlove Mamattah, in 1971. With the introduction of some improved rabbit breeds, breeding herd was approximately 1,478 by 1978 (Lukefahr, 1998; Lukefahr, 2000). Individuals, particularly women, children and rural folk who showed keen interest in this species, recorded tremendous successes. This initiative notwithstanding, performance records of rabbits have over the period not only been sub-optimal, but also continued to follow a downward trend. With time a number of individuals and governmental institutions (like the Rabbit Unit of the Animal Research Institute of the Council for Scientific and Industrial Research) abandoned the programme entirely, focusing only on the traditional livestock species. It is thus not surprising that efforts primarily geared towards enhancing the general performance (reproductive and growth) of rabbits through improved nutrition and management practices, have not yielded the expected results.

An important intervention or tool that has greatly influenced output of not only livestock species but also plant species as well has been crossbreeding. Crossbreeding is basically the mating of individuals of different breeds. The exercise results in the alteration of genetic variance, and allows combining the valuable traits of parent lines in their progeny. It has also been found to be a major tool for the full exploitation of genetic variation in rabbits (Lukefahr, 1998), being identified as one of the best options to increase profits of the warren or colony because of its particular impact on productivity and adaptation to the environment (Akinsola et al., 2014; Fayeye & Ayorinde, 2010; Mbanasor, & Wogu, 2006; Obiajulu et al., 2016). Baselga (2004) has indicated that due to the nature of their productive traits, rabbits offer a higher degree of kindness (productivity) when improved via cross breeding.

Diallel crossing is a crossbreeding system that involves crossing each of several individuals with two or more others in order to determine the relative genetic contribution of each parent to specific characters or traits in the offspring. It has been identified as one of the best approaches to facilitate the selection of an ideal genotype, primarily because of the combining ability of the genotypes. Likewise, diallel crossing permits the estimation of heterosis among all pairs of breeds. This has been found to be useful in the evaluation of breeds which are already indigenous to a region or for a limited number of breeds chosen on the basis of prior top cross evaluation (García, Ponce de León & Guzmán, 2012). Aside offering the opening to assess the varied genetic aspects of the parents‘ performance, diallel crossing helps in taking objective decisions in the different improvement programmes right from the identification of superior genotypes and promising combinations for the desired economic traits (Ramos et al., 2006). It is thus not surprising that the diallel crossing is considered as an efficient means of assessing the full genetic and heterotic potential of different breeds or lines.

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Item Type: Ghanaian Topic  |  Size: 184 pages  |  Chapters: 1-5
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