Abstract
Simple SummaryThe aim of this study was to examine the effectiveness of selection for total body fat content and its effect on productive and carcass traits. Growing rabbits were selected for high or low body fat content. The selection was effective, and the difference in fat reserves (perirenal fat and scapular fat content) increased with each generation. After four generations, the feed conversion rate improved, and the ratios of fore and hind parts increased in lean rabbits. Selection for lower total body fat content could be useful for customers who want to buy animals and meat with lower fat content; while selection for higher fat content could be advantageous for rabbit does because they have more fat (energy) deposits which are in positive connection with maternal ability and a longer lifespan.The aim of this experiment was to study the effect of divergently selected rabbits for total body fat content (fat index) on growth performance and carcass traits. The fat index was determined at 10 weeks of age by computed tomography and lasted for four consecutive generations. The rabbits with the lowest fat index belonged to the lean line and those of the highest values belonged to the fat line. At generation four, 60 rabbits/line were housed in wire-mesh cages and fed with commercial pellet ad libitum from weaning (5 w of age) to slaughtering (11 w of age). Growth performance, dressing out percentage and carcass adiposity were measured. The lean line showed a better feed conversion ratio (p < 0.001) than the fat line. Furthermore, the carcass of the lean rabbits had the highest proportion of fore (p < 0.020) and hind (p < 0.006) parts. On the contrary, rabbits of the fat line had the highest carcass adiposity (p < 0.001). The divergent selection for total body fat content showed to be effective for both lean and fat lines. Selection for lower total body fat content could be useful for terminal male lines, while the selection for higher total body fat content could be an advantage for rabbit does in providing fat (energy) reserves.
Highlights
In recent decades, the main trends in rabbit selection programmes were the increase in doe prolificacy in maternal lines, and the maximization of the growth rate in terminal lines
For the purpose of this study, the divergent selection process was based on the fat index calculated in live rabbits aged 10 weeks, calculated as the ratio of the total body fat volume, the latter estimated by computed tomography (CT), to the body weight
The results highlighted that there was no significant difference in body weight (BW) and daily weight gain (DWG)
Summary
The main trends in rabbit selection programmes were the increase in doe prolificacy in maternal lines, and the maximization of the growth rate in terminal lines. The first purpose was aimed at weaning a higher number of kits, as it represents one of the most important economic components of intensive meat production. The second purpose was aimed at anticipating the slaughter weight [1]. Selection programmes have included traits such as longevity, the homogeneity of birth weight, residual feed intake, meat yield, and resistance to diseases [2,3,4]. Hetzer and Harvey [5] were pioneers in this sense. They selected two different pig breeds for backfat thickness over 8 and 10 generations and demonstrated in both cases that the selection process was rather effective in both directions. Cahaner et al, Zhang et al.; Baéza and Le Bihan-Duval [6,7,8]
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