Effects of monosodium glutamate on lines of chickens having different juvenile exponential growth rates

MSG (4 mg/g BW) or the equivalent molar ratio of NaCl were injected subcutaneously into chicks from four populations of chickens derived from a double selection experiment [(1) low exponential growth rate (EGR) to 14 days of age (14L), (2) high EGR to 14 days of age (14H), (3) low EGR to 42 days of age (42L) and high EGR to 42 days of age (42H)]. MSG significantly influenced growth in chickens, but the absolute effect was genotype and sex dependent. Weights of abdominal fat pads were ranked among lines according to the sequence 42H, 14H, 42L and 14L. MSG significantly increased fat pad size by 51%, independent of genotype or sex. MSG significantly decreased breast weight in females and males by 7%. The higher percent fat pads and lower breast weights associated with MSG are indicative of growth due to fat accretion rather than protein deposition.