Abstract
Two experiments were conducted to evaluate the effect of the intramuscular injection of betacarotene associated to tocopherol on the plasma concentration progesterone of superovulated Holstein heifers (experiment 1) and in crossbred (Bos taurus x Bos indicus) heifers submitted to fixed-time embryo transfer (FTET, experiment 2). In experiment 1, after estrus synchronization and superovulation animals were inseminated 12 and 24 hours after estrus onset and embryos flushed 7 days later. Heifers were allocated randomly to one of three treatments: Control; T800 (800 mg of betacarotene plus 500 mg of tocopherol) and T1200 (1,200 mg of betacarotene plus 750 mg of tocopherol). The treatments were given on the day of ear implant placement and repeated on the first day of superovulation. Blood samples were collected on D0, D5, D9, D12 and D16. In experiment 2, treatments were imposed at intravaginal device insertion (D0). The same experimental design, as in experiment 1, was used. Blood samples were collected on D17 (embryos implanted) for progesterone determination by radioimmunoassay. In experiment 1, average plasma progesterone concentrations after corpora lutea formation (D12 plus D16 means) were 13.7±1.8 ng/ml, 14.5±2.3 ng/ml and 10.8±2.3 ng/ml for control, T800 and T1200, respectively, and did not differ (P=0.44). In experiment 2, progesterone concentrations on D17 in Control (8.88±0.57 ng/ml), T800 (7.48±0.64 ng/ml) and T1200 (5.90±1.33 ng/ml) groups were similar (P=0.11). Results indicate that the supplemental betacarotene and tocopherol injections did not influence peripheral progesterone concentrations in superovulated Holstein donors and crossbreed recipients heifers.
Highlights
Betacarotene is a lipid soluble isoprenoid pigment and it is produced by plants and other photosynthetic organisms
This carotenoid is the natural precursor of vitamin A in feedstuff and it is converted to retinol, in the liver and used in tissues as retinal (BENDICH; OLSON, 1989)
Two experiments were conducted to evaluate the effect of the intramuscular injection of betacarotene associated to tocopherol on the plasma concentration progesterone of superovulated Holstein heifers and in crossbred (Bos taurus x Bos indicus) heifers submitted to fixed-time embryo transfer (FTET, experiment 2)
Summary
Betacarotene is a lipid soluble isoprenoid pigment and it is produced by plants and other photosynthetic organisms. The first evidence for the antioxidative effect of betacarotene on luteal cells, reported by Young et al (1995) was that, the supplementation of cells in vitro culture with betacarotene reduced the links between the cholesterol side-cleavage enzyme and adrenodoxin. These results were latter confirmed by Rapoport et al (1998), whom determined a significant positive correlation between the concentrations of lutheal P450 cytochrome, betacarotene and plasma progesterone. Betacarotene stimulates and induces the synthesis of the cholesterol side chain cleavage enzyme, increases cAMP concentrations and activates protein kinase C-dependent cAMP (TALAVERA; CHEW, 1987) Besides this action on steroidogenesis, there are others beneficial effects of betacarotene on reproduction. The hypothesis was: Supplemental betacarotene and vitamin E injection (injectable bolus) increases plasma progesterone concentration in heifers
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