Journal of Animal Science

Skeletal muscle adaptations and biomechanical properties of tendons in response to jump exercise in rabbits

F. Gondret*, P. Hernandez**, H. Rémignon***, and S. Combes***

Abstarc :

Pen housing has been proposed in rabbits as an alternative tostandard-sized cages. Rabbits reared in pens show greater physicalactivity. This study investigated whether jump exercise couldmodify body composition, muscle biochemical and histologicalcharacteristics, and some meat quality traits, including thebiomechanical properties of tendons. Male weaned rabbits ofsimilar BW (793 ± 11 g) were either reared in giant collectivecages and had to jump over obstacles to get food and water for35 consecutive days (EXE), or confined in small isolated cages(SEDN). Rabbits were weighed weekly to determine ADG (n = 79EXE; n = 46 SEDN) and ADFI (n = 9 cages in EXE; n = 46 cagesin SEDN). At approximately 10 wk of age, rabbits were slaughteredin 2 series. After overnight chilling, carcasses in the firstseries (n = 30 EXE; n = 27 SEDN) were divided into fore, intermediate,and hind parts. Color and ultimate pH were recorded in the bicepsfemoris (BF) and LM. The Achilles tendon and patellar ligamentwere dissected from the legs and cooked. Muscles [semimembranosusproprius, semimembranosus accessorius (SMA), and BF] were harvestedfrom the legs in a subset of animals from the second series(n = 10 in EXE; n = 9 in SEDN). Both ADG and ADFI were slightlyreduced (P < 0.10) in EXE rabbits compared with SEDN rabbits.Exercised rabbits showed a greater (P = 0.01) proportion ofhind parts than SEDN rabbits. Enzyme activities of 3-hydroxyacyl-CoAdehydrogenase and citrate synthase, which play key roles infatty acid oxidation and the terminal oxidative degradationof nutrients, respectively, were increased in the semimembranosusproprius, SMA (except citrate synthase), and BF muscles of EXErabbits compared with SEDN rabbits. Only SMA exhibited a decreased(P = 0.05) activity of the glycolytic enzyme, lactate dehydrogenase,in EXE rabbits compared with SEDN animals. Total lipid content,mean diameter of perimysial adipocytes, and activities of corelipogenic enzymes in the SMA and BF muscles did not differ betweenEXE and SEDN rabbits. Meat color in BF was shifted toward greatera* (red; P = 0.001) and b* (yellow; P = 0.02) values in EXErabbits compared with SEDN rabbits. Cooked Achilles tendon andpatellar ligaments in the legs had greater stiffness (P >= 0.05)in EXE rabbits compared with SEDN rabbits. This experiment demonstratesthat rabbit muscles turn to a more oxidative metabolic patternin response to jump exercise. The quality of attachment of cookedmeat to bone is also improved in active rabbits.

Key Word :
fiber type composition, intramuscular lipid, jump exercise, meat quality, oxidative enzyme, tendon

Volume 87, Number 2, February 2009