Growth feed efficiency and body composition of transgenic mice expressing a sheep metallothionein 1a sheep growth hormone fusion gene
Pomp, D.; Nancarrow, C.D.; Ward, K.A.; Murray, J.D.
Livestock Production Science 31(3-4): 335-350
ISSN/ISBN: 0301-6226 DOI: 10.1016/0301-6226(92)90079-j
Growth, feed efficiency and body composition were studied in male possessing a sheep metallothionein 1a-sheep growth hormone transgene (oMT1a-oGH). The transgene was activated at weaning (21 d) by 25 nM zinc sulfate provided in drinking water. Bodyweight and feed intake were measured at weekly intervals until 70 d. Transgenic males gained 53.3% more weight than controls during the test period (P < 0.001) while consuming only 10.9% more feed (P < 0.001). When adjusted for metabolic body weight, feed intake was similar for the two genotypes. Transgenics had more epididymal and subcutaneous fat at 70 d (P < 0.001), but less fat at both depots (P < 0.05) when adjusted to a common body weight. Lean tissue, estimated by trimmed hind carcas weight, was greater in transgenics when compared at a common age (P < 0.01) but lower when compared at a common body weight (P< 0.001). If analyzed for a common weight gain, transgenic exhibit much higher efficiency of lean tissue production, due to a much lower intake required to product lean. Visceral organs were heavier in transgenic than in controls, but only liver and spleen exhibited disproportional enlargement relative to overall body size increases (P < 0.001). These results demonstrate that mice processing an oMT1a-oGH transgene exhibit increased efficiency of growth and of lean tissue production, especially when considered over a standard weight gain period.