Effects of ractopamine on performance and composition of pigs phenotypically sorted into fat and lean groups

Crossbred barrows (n = 144; 80 kg) from four farrowing groups were phenotypically selected into fat (FAT) and lean (LEAN) pens using ultrasound. The difference in 10th-rib fat depth between the LEAN and FAT groups was [>/=]0.5 cm. Within a farrowing group, pigs were assigned to pens (five pigs pe...

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Bibliographic Details
Published in:Journal of animal science 2005-06, Vol.83 (6), p.1361-1369
Main Authors: Mimbs, K. J, Pringle, T. D, Azain, M. J, Meers, S. A, Armstrong, T. A
Format: Article
Language:English
Subjects:
Adipose Tissue - diagnostic imaging
Animal Feed - analysis
animal performance
Animal productions
Animals
Biological and medical sciences
body composition
Body Composition - drug effects
body fat
carcass characteristics
carcass composition
Diet - veterinary
feed conversion
feed intake
food animals
Fundamental and applied biological sciences. Psychology
Genotype
Growth - drug effects
growth regulators
Growth Substances - administration & dosage
Growth Substances - pharmacology
lean body mass
liveweight gain
Male
Phenethylamines - administration & dosage
Phenethylamines - pharmacology
Phenotype
swine
Swine - growth & development
Swine - physiology
Terrestrial animal productions
Time Factors
Ultrasonography
Vertebrates
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Summary:Crossbred barrows (n = 144; 80 kg) from four farrowing groups were phenotypically selected into fat (FAT) and lean (LEAN) pens using ultrasound. The difference in 10th-rib fat depth between the LEAN and FAT groups was [>/=]0.5 cm. Within a farrowing group, pigs were assigned to pens (five pigs per pen and eight pens per phenotype) to equalize pen weight and fat depth. Pigs were fed a corn-soybean meal diet containing 19% CP, 1.0% added animal/vegetable fat, and 1.1% lysine (as-fed basis). Half the pens received 10 ppm (as-fed basis) of ractopamine (RAC) during the 28-d finishing phase. At 7-d intervals, live weight and feed disappearance were recorded to calculate ADG, ADFI, and G:F, and 10th-rib fat depth and LM area were ultrasonically measured to calculate fat-free lean and fat and muscle accretion rates. During the first 7 d on feed, LEAN pigs fed RAC gained less (P < 0.05) than FAT pigs fed RAC or LEAN and FAT pigs fed the control diet (RAC x phenotype; P = 0.02); however, RAC did not (P > 0.25) affect ADG after the second, third, and fourth weeks, or over the entire 28-d feeding period. Although wk-2 and -3 ADG were higher (P 0.10) G:F after 7 d on trial; however, RAC improved (P
ISSN:0021-8812
1525-3163
DOI:10.2527/2005.8361361x