Growth performance, carcass traits, muscle fiber characteristics and skeletal muscle mRNA abundance in hair lambs supplemented with ferulic acid.

Ferulic acid (FA) is a phytochemical with various bioactive properties. It has recently been proposed that due to its phytogenic action it can be used as an alternative growth promoter additive to synthetic compounds. The objective of the present study was to evaluate the growth performance, carcass traits, fiber characterization and skeletal muscle gene expression on hair-lambs supplemented with two doses of FA. Thirty-two male lambs (n = 8 per treatment) were individually housed during a 32 d feeding trial to evaluate the effect of FA (300 and 600 mg d-1) or zilpaterol hydrochloride (ZH; 6 mg d-1) on growth performance, and then slaughtered to evaluate the effects on carcass traits, and muscle fibers morphometry from Longissimus thoracis (LT) and mRNA abundance of ß2-adrenergic receptor (ß2-AR), MHC-I, MHC-IIX and IGF-I genes. FA increased final weight and average daily gain with respect to non-supplemented animals (p < 0.05). The ZH supplementation increased LT muscle area, with respect to FA doses and control (p < 0.05). Cross-sectional area (CSA) of oxidative fibers was larger with FA doses and ZH (p < 0.05). Feeding ZH increased mRNA abundance for ß2-AR compared to FA and control (p < 0.05), and expression of MHC-I was affected by FA doses and ZH (p < 0.05). Overall, FA supplementation of male hair lambs enhanced productive variables due to skeletal muscle hypertrophy caused by MHC-I up-regulation. Results suggest that FA has the potential like a growth promoter in lambs.

Differential effect of chronic undernutrition on the fiber type composition of fascicles in the extensor digitorum longus muscles of the rat.

Several studies have shown that chronic low food consumption alters the composition and metabolism of the extensor digitorum longus muscle (EDLm) fiber types. EDLm is constituted by four independent fascicles (F2-F5) of different sizes; their constitution and metabolism, however, as well as how chronic undernourishment affects these is virtually unknown. Thus, the aim of this study is to evaluate the relative fiber type composition and metabolism of each independent fascicle in the EDLm, using control and chronically undernourished young male rats by using the alkaline ATPase and NADH-TR histochemical techniques. Our results indicate that all control fascicles showed a higher percentage of intermediate fibers (P<0.001), except for F5, which had a higher percentage of fast fibers (P<0.001). After chronic undernutrition, the proportion of intermediate fibers decreased in F4 (P<0.05) and increased in F5 (P<0.001), whereas fast fibers decreased in F3 (P<0.05) and F5 (P<0.001). When we investigated fiber metabolism we found that F3 and F4 had a similar composition (mainly glycolytic), whereas F2 and F5 predominantly contained oxidative fibers. All fascicles of chronic undernourished rats showed a general decrease in oxidative fibers (P>0.05), except for F3, in which oxidative fibers increased (P<0.05). After determining the possible predominant metabolism expressed in intermediate fibers, we propose that chronic undernutrition induces the transformation of fast-glycolytic to intermediate-oxidative/glycolytic fibers, mainly in F3 and F5. Our observations confirm that chronic undernourishment differentially affects the fiber types of each fascicle in the EDLm, which could alter their individual physiological contractile properties.

Histoenzymatic and morphometric analysis of muscle fiber type transformation during the postnatal development of the chronically food-deprived rat.

We analyze the effect of chronic undernourishment on extensor digitorum longus (EDL) muscle maturation in the rat. Cytochrome c oxidase (COX) and alkaline ATPase histoenzymatic techniques were used to determine the relative proportion of different fiber types (oxidative/glycolytic and type I, IIa/IId, or IIb, respectively) and their cross-sectional area in control and undernourished EDL muscles at several postnatal (PN) ages. From PN days 15 to 45, undernourished EDL muscles showed predominance of oxidative and type IIa/IId fibers, but from PN days 60 to 90, there were a larger proportion of oxidative fibers and an equal proportion of type IIa/IId and IIb fibers. Meanwhile, in adult stages (from PN days 130-365), the relative proportion of fiber types in control and undernourished EDL muscles showed no significant differences. In addition, from PN days 15 to 90, there was a significant reduction in the cross-sectional area of all fibers (slow: 13-53%; intermediate: 24-74%; fast: 9-80%) but no differences from PN days 130 to 365. It is suggested that chronic undernourishment affects the maturation of fast-type muscle fibers only at juvenile stages (from PN days 15-45) and the probable occurrence of adaptive mechanisms in muscle fibers, allowing adult rats to counterbalance the alterations provoked by chronic food deprivation.