Abstract
Two lines of mice, M16 selected for rapid growth and a randomly selected control ICR as well as their reciprocal crosses were used to study the effects of genotype on whole-body energetics and intestinal responses to monensin. Six mice, eight weeks of age, from each line or reciprocal cross were assigned to one of two treatments, 1) drinking water containing 20 mmol/L monensin dissolved in 0.5% V/V ethanol, and 2) drinking water containing 0.5% V/V ethanol (control) for two weeks. After 11 days (age of 9 weeks and 4 days), whole-body O2 consumption was measured. At the end of two weeks, jejunal O2 consumption, intestinal tissue composition and histomorphometrics as well as the rate and efficiency of glucose absorption were estimated. In comparison with the control, monensin administration in drinking water resulted in less daily water intake (13.4 vs. 15.5 ml/mouse, p 0.05) effect on variables measured in either line of mice or their reciprocal cross. In contrast, the M16 line, selected for rapid growth, as compared to the ICR controls or the reciprocal crosses, had less initial (pre-monensin treatment) whole-body O2 consumption per gram of body weight (1.68 vs. 2.11-2.34 µmol/min⋅g BW, p 0.05) effect on whole-body O2 consumption and jejunal function, whilst selection for rapid growth resulted in an apparent down-regulation of intestinal function. These data suggest that genetic selection for increased growth does not result in concomitant changes in intestinal function. This asynchrony in the selection for production traits and intestinal function may hinder full phenotypic expression of genotypic growth potential. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 4 : 554-562)
Highlights
Antibiotics are used in animal industry, where allowed by law, usually for improving growth, feed efficiency, and general health
There have been no studies on the effects of ionophores on whole-body metabolism and intestinal absorption and function across genotypes within a species
The treatment arrangement of this experiment was body energetics and intestinal function amongst different factorial, in which mice from the four genetic lines were genotypes of special interest such as a genetically improved treated with drinking water containing either monensin or rapid growth animal or poultry
Summary
Antibiotics are used in animal industry, where allowed by law, usually for improving growth, feed efficiency, and general health. The treatment arrangement of this experiment was body energetics and intestinal function amongst different factorial, in which mice from the four genetic lines were genotypes of special interest such as a genetically improved treated with drinking water containing either monensin or rapid growth animal or poultry. For each of unlikely that one study using a genotype such as that the four lines, six cages of mice (age 7 weeks), two males in reported by Fan et al (2003), could reflect possible whole- each cage, were randomly assigned to one of the two body and intestinal response to an ionophore antibiotic over drinking water treatments. Mice had free access to drinking water and a measurements, oxygen consumption estimation and commercial pelleted feed (Rodent Laboratory Chow #5001, morphometric analyses was conducted according to Fan et Purina Mills, Inc., St. Louis, MO).
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