Selection for postweaning gain in rats: I. Correlated response in feed utilization and body composition.

Abstract

Response to selection for up (U) and (D) 3- to 9-wk gain in rats on average daily gain (ADG), average daily feed intake (ADI), gain/feed (G/F), body composition (BC), fasting metabolic rate per unit metabolic size (MR) and partial efficiency of weight gain (ADG/Fg) was evaluated after 34 generations of mass selection. At 3-wk weaning, 120 litters representing F1 crosses of two replicates within each of the U, D and control (C) selection lines were divided within sexes between bulk-feeder and tube-feeder cage types for recording feed intake until 9 wk of age. Rats from tube-feeder cages representing 16 litters/line were utilized for MR and BC data. Response in ADG was asymmetrical; 16% higher for U line but only 8% lower in D line, compared with C line. Correlated responses were positive and significant in both U and D lines for ADI (6% and -3%) and G/F (5% and -5%). Line differences in MR were not significant but both selected lines were slightly higher than C line in MR at 6 wk of age, and the reverse at 9 wk of age. Over the period of 6 to 9 wk of age, maintenance requirements per unit metabolic size and ADG/Fg were 1 and 5% above for the U and -1 and -4% for D lines, relative to C line. Females of both selected lines were fatter than C line (P less than .05) at 9 wk of age, but only D line males were fatter than C line.

• Authors: J G Rios, M K Nielsen, G E Dickerson, J A DeShazer
• Journal: Journal of animal science (J Anim Sci) Vol. 63 Issue 1 Pg. 34-45 (Jul 1986) ISSN: 0021-8812 [Print] United States
• PMID: 3733575 (Publication Type: Comparative Study, Journal Article)

Topics

• Animal Nutritional Physiological Phenomena
• Animals
• Body Composition
• Body Weight
• Female
• Growth
• Male
• Rats (physiology)
• Selection, Genetic
• Weaning