Effects of physical activities on biochemical and biomechanical properties of tendons in two commercial types of chickens.

The aim of our experiment was to study the effects of physical activities on the biochemical and biomechanical properties of tendons in 12 standard (S) broilers and 12 Label Rouge (LR) chickens. In the two types of birds no differences were found between control and active birds for body weights. Gastrocnemius (Gas) tendon and Pectoralis minor (Pm) tendons were harvested and processed for passive stretch tests prior to cooking or not. Some biochemical parameters also were determined. Results showed that total collagen content in Gas tendon was significantly higher in active than in control birds. However, no significant changes were found in collagen solubility in LR tendons while these values were increased in S ones. Active birds showed greater sGAGs content than control ones. Ultimate load was found to be significantly higher in active birds than in control. Deformability (defined by Poisson's ratio) of raw and heated at 80 degrees C Gas tendons increases in active groups because Poisson's ratio decreases. Physical activities also increase the rigidity (defined by elastic modulus) of raw and heated at 80 degrees C Gas tendons because elastic modulos values increase. Physical activity was not able to modify stiffness or maximum stress values in raw or heated at 80 degrees C Gas tendons from broilers whereas these two parameters were found to be slightly higher in active group from LR chickens only in raw tendons. All the biomechanical results recorded in Pm tendons from both types of chickens were not significantly different between control and active birds. A significant correlation was found between the total collagen content and stiffness in Gas tendon from LR active birds.

The effects of overfeeding on myofibre characteristics and metabolical traits of the breast muscle in Muscovy ducks (Caïrina moschata).

The aim of this experiment was to study the consequences of precise feeding on the myofibre characteristics and metabolic traits of the breast muscle (Pectoralis major, Pm) of Muscovy ducks. Twenty-four samples of breast muscle, without skin or subcutaneous fat, from two groups of ducks, control and overfed respectively, were collected at 14 weeks of age. We assayed different chemical (water content, crude proteins, total lipid ashes, total and thermosoluble collagen), biochemical (activities of the CS, LDH and beta-HAD enzymes), histological (muscle fibre typing and intramuscular adipocyte measurements) and technological (drip and cooking losses, texture) determinations. At the force-feeding period, the overfed ducks weighed 6366 g and the control ducks 4606 g of body weight. In the PM muscle, some modifications of the biochemichal parameters and enzyme activities were observed but neither the shear force nor the histological characteristics of the breast muscle were affected by the fattening treatment. The overfed birds had an increased total lipids content (correlated to an increase in the intramuscular area occupied by the adipocyte) and a different fatty acid profile as the result of a higher energy feed intake. The lipids of the Pm muscle of the overfed ducks contained more C16:0, C16:1n-7 and C18:1n-9, but less C18:0, C18:2n-6 and C20:4n-6 than the control birds. These results show that in response to high energy feeding, the muscle is able to respond quickly on a metabolic basis (by increasing the activities of the oxydative enzymes) without changing its typology or morphology. Additionally, fattening was correlated to a degradation in the technological qualities of the breast muscle, especially an increase in the cooking losses.