The response of highly productive rabbits to dietary lysine content

Abstract

The lysine requirement of rabbits based on total lysine or on faecal digestibility was investigated. Five diets containing from 0.64 to 0.82% of crude lysine were made by supplementing a basal diet with L-lysine HCl. Apparent lysine digestibility (%) was 74.2±1.0 ( n=9) in the basal diet and 104.4±7.4 for L-lysine HCl, as estimated by the difference method. A feeding trial using 440 rabbit does was carried out over a 5-months experimental period. Milk production was measured in 70 lactations. Reproductive performance traits (parturition interval, prolificacy, kit mortality) did not improve for dietary lysine levels above 0.68 or 0.52% of crude and digestible lysine, respectively. Total milk production was affected quadratically (P < 0.001) by dietary lysine content showing a maximum for 0.80 or 0.64% of crude and digestible lysine, respectively. As a consequence, a positive but decreasing response of growth of kits and feed conversion rate to dietary lysine level was observed. A growth trial was also conducted over the fattening period using 965 weaned rabbits. Carcass traits were determined in 125 rabbits. Average daily gain and carcass dressing percentage increased (P < 0.001) with increasing dietary lysine content, but no response was found beyond 0.76 or 0.60% of crude or digestible lysine, respectively. Feed conversion rate, mortality, and proportion of primal joints in the carcass were not significantly affected (P > 0.05) by type of diet.