Lactation, hair development and homeothermy are characteristic evolutionary features that define mammals from other vertebrate species. Here we describe the discovery of two autosomal dominant mutations with antagonistic, pleiotropic effects on all three of these biological processes, mediated through the prolactin signalling pathway. Most conspicuously, mutations in prolactin (PRL) and its receptor (PRLR) have an impact on thermoregulation and hair morphology phenotypes, giving prominence to this pathway outside of its classical roles in lactation.

Five generations of phenotypic mass selection for increased 70-d body weight (market age, MW) were conducted in an experimental population of rabbits. Market-age weight was recorded for 1,616 rabbits from 336 litters (sired by 121 bucks and reared by 321 does). Additional growth and carcass traits measured in control (C) and select (S) lines were 28-d weaning weight (WW), 28- to 70-d average daily gain (ADG), carcass yield percentage (CY), loin primal cut percentage (LP), and lean-to-bone ratio in the loin primal cut (LBR). Average inbreeding coefficients in litters by the fifth generation were 10.3 and 11.2% for C and S lines, respectively. After five generations the difference in weighted cumulative selection differential between lines for MW was 1,015 g. Using an animal model with REML and regression procedures, observed and realized estimated heritabilities for MW were .12 and .11, respectively. Estimates of heritability by REML were .04, .17, .37, .25, and .35 for WW, ADG, CY, LP, and LBR, respectively. Bivariate REML estimates of direct genetic, common litter, and residual correlations between MW and a second growth trait (WW or ADG) were all positive and moderate to high in magnitude (range of .56 to .98). At generation five, mean direct breeding values of S and C line rabbits for MW were 133.2 and 12.0 g. Genetic trends were 29.1 and 29.4 g per generation for MW, estimated according to regressions of estimated mean breeding value (obtained from mixed-model analyses) or of observed S minus C line mean differences on generation number, respectively. Correlated response for WW, ADG and LBR was consistently favorable, whereas results for other carcass traits studied were inconclusive. Selection was effective for increasing MW performance.

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High poverty levels continue to plague much of Africa despite several intervention strategies aimed to stem the tide. The role of small livestock like rabbits as a tool in poverty alleviation programmes has been acknowledged for decades and successful national rabbit projects have clearly been demonstrated in Africa. With rising poverty levels across Africa, the need to rejuvenate such national rabbit projects for long-term sustainability becomes apparent. This presentation focuses on the status of rabbit production in Africa, with special attention to smallholder rabbit project development and its connection with poverty alleviation issues in the continent and with an emphasis on the strengths, weaknesses, opportunities and barriers to the system. A special case is made for the sustainable development of smallholder, low-input rabbit production systems in Africa on account of their popularity, low investment requirements and low economic risks, as well as their contributions to family nutrition, income generation and gender empowerment. Successful rabbit projects in several countries across Africa were identified and the reasons for success, as well as lessons learned, are discussed. In all, several cases standout: the National Rabbit Project of Ghana, the Heifer Project International Rabbit Project in Cameroon, and CECURI Rabbit Project in Benin Republic. Other fast-paced and moderately developed rabbit industries (e.g. in Egypt, Tunisia and Algeria) are recognised. Critical constraints to rabbit project development (e.g. non-implementation of sustainable models for low-input rabbit units and absence of client-focused research and development programmes) are noted. Prospects for the development of sustainable smallholder rabbit production models are discussed, which include the following: a paradigm shift among researchers to focus on innovative research related to the development of sustainable backyard rabbit production systems; upscaling of sound practices in smallholder rabbit units across regions; use of local value chains in smallholder rabbit development and setting up regional networks of smallholder family rabbit projects. The actualisation of these goals requires a sustainability research agenda that focuses more on backyard rabbit farmers as the primary beneficiaries. Overall, the need for a poverty focus and a pro-poor research agenda involving owners of backyard rabbits are emphasised.

Lactation records (n = 86) from 60 does of four breeds (Californian, New Zealand White, Palomino and White Satin) were analyzed to assess the effects of breed, parity, day of lactation and number of kits on milk production. Breed of doe tended (P less than .07) to be important for mean milk yield according to ANOVA results. Californian does had numerically higher production than did does of the other breeds. Doe body weight, litter size born alive and weaned and litter weaning weight, likewise, were not influenced (P greater than .05) by breed of doe. Significant linear and quadratic relationships were found between milk production vs day of lactation, and milk production vs number of kits. However, breed x days and breed x number of kits interactions (P less than .05) indicated that the individual breeds responded differently to two of these effects. Peak lactation occurred at approximately 20 d after kindling. As kit number increased, milk yield also increased to a predicted maximum when 12 kits were suckling. Parity tended (P less than .10) to influence lactation yield in a curvilinear manner, increasing steadily through the seventh parity and declining thereafter. A nonsignificant residual correlation (.34) between milk production and doe body weight was observed. Corresponding correlations between milk production were high for litter size born alive and weaned (r = .62 and .87, respectively) and litter weaning weight (r = .86). Although lactation curves are unique to each particular breed, milk yield is influenced by several factors.

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Two hundred twenty-five lactation and litter performance records from 82 does representing four genetic groups and two diets were analyzed to quantify breed, heterosis, reciprocal F1 cross and diet effects for milk production and associative traits. Doe genetic groups were New Zealand White (NN) and Californian (CC) straightbred and Californian X New Zealand White (CN) and New Zealand White X Californian (NC) reciprocal crossbreds. Pelleted diets fed to does and litters were either a commercial control or a 74% alfalfa diet. Three sire breeds of litters included NN, CC and Flemish Giant (FG) straightbreds. Doe genetic group and diet were important sources of variation (P less than .05) for all traits examined except for litter milk efficiency (litter gain/milk intake) and doe feed efficiency (milk yield/feed intake). The sire breed of litter effect did not influence (P greater than .05) lactational performance of does nor associative preweaning traits. Straightbred NN does were heavier at kindling, yielded more milk, reared a heavier litter by 21 d and were more efficient in converting feed into milk than were straightbred CC does (P less than .01). Significant heterosis was detected for milk production and for litter size and weight at 21 d. Reciprocal differences between crossbred doe groups were observed (P less than .05) for litter milk efficiency and doe feed intake. The 74% alfalfa diet was superior to the commercial control diet for effects on milk production and litter size and weight at 21 d, although doe feed intake was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive characters (N = 430 matings) of four doe genetic groups and preweaning performance of litters (N = 280) were evaluated in a 15-mo study. Doe genetic groups were New Zealand White (NN) and Californian (CC) straightbreds and Californian X New Zealand White (CN) and New Zealand White X Californian (NC) crossbreds. Does and litters were provided either a commercial control or a 74% alfalfa pelleted diet. Sires of litters included NN, CC and Flemish Giant (FG) straightbred bucks. The linear and quadratic regression on age of dam affected (P less than .01) litter birth weight. The NN does were heavier than CC does at first breeding at 154 d and produced heavier litters at birth and weaning (all P less than .01). Percentage survival of kits from birth to weaning and doe and preweaning litter feed intake and efficiency were greater from NN than CC does (all P less than .01). Numbers born and reared/litter to weaning at 28 d were likewise greater for NN vs CC straightbred does. Heterosis estimated from comparing litters of reciprocal crossbred vs straightbred does was significant for number born, litter birth and weaning weights and doe and preweaning litter feed intake. Reciprocal crossbred differences were observed (P less than .05) for doe breeding weight, number born and weaned per litter, litter birth and weaning weights and doe and preweaning litter feed intake, favoring CN does reared by NN straightbred dams over NC does. Diet, in consistent favor of the 74% alfalfa diet, significantly affected all traits studied with the exception of doe longevity, doe fertility percentage, and doe and litter feed efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)