Abstract
Tilapia ( n=12 per treatment in duplicate) were subjected to two different dietary levels of lipid (∼8% and 17%) and injected doses of recombinant bovine growth hormone (2.5 and 5.0 μg rbGH g −1 body weight week −1). The effects of these treatments were examined with respect to their impact upon growth and body shape. Tilapia fed high-lipid diets expressed increased weight and length gains ( P<0.05). Accelerated growth in body weight and length was recorded in both dietary groups with injection of the lower dose of GH ( P<0.05). However, no effect was seen in fish given the higher GH dose. Limited interactions between GH and dietary lipid were recorded during the experiment and feed efficiencies were similar for all groups. High dietary lipid increased body lipid levels ( P<0.01). Gender differences, favouring females ( P<0.01) for gonadosomatic and males ( P<0.01) for intestinal indices, were recorded, but GH and diet were without overall effect. However, higher dietary lipid increased hepatosomatic indices ( P<0.05). Multivariate tests of significance of whole body outline demonstrated highly significant ( P<0.01) differences between treatment groups, with GH injection increasing post-orbital length. Head shape was profoundly impacted ( P<0.01) by GH, which caused a visual broadening and shortening following examination by superimposition. Analysis of the syncranium using X-radiography illustrated no differences between groups suggesting that external shape change resulted due to modifications to animal physique.
Published Version
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